Pub Date : 2026-01-01Epub Date: 2025-12-24DOI: 10.1016/j.jot.2025.10.016
Xu Yan , Haixing Wang , Xuan Lu , Linlong Li , Shanshan Bai , Zitong Li , Han Su , Rongjie Wu , Hui Chen , Yinuo Fan , Jiting Liu , Xinkun Zhang , Lichun Xie , Ling Qin , Gang Li , Sien Lin
<div><h3>Background</h3><div>Mechanical stimuli are indispensable for bone regeneration. Distraction osteogenesis (DO) is a widely used clinical technique for limb lengthening and bone defect repair; however, its specific mechanobiological mechanisms remain unclear. Macrophages play crucial regulatory roles throughout bone fracture healing. Recent studies indicate that macrophages are mechanosensitive and can modulate the local immune microenvironment in response to mechanical cues. This study aims to investigate how macrophages respond to mechanical stimulation and regulate bone regeneration during DO.</div></div><div><h3>Methods</h3><div>Animal models of DO (with external fixation) and fracture healing (with internal fixation) were established to compare bone regeneration under different mechanical conditions. Immunohistochemistry (IHC) was used to quantify M1 and M2 macrophage infiltration. An <em>in vitro</em> model of cyclic mechanical stretch (10 %, 0.5 Hz, 12 h) was applied to RAW264.7 cells to study macrophage polarization. Flow cytometry, PCR, and western blot were used to assess macrophage phenotypes. An indirect co-culture system was employed to evaluate the effect of mechanically stimulated M2 macrophages on osteogenic differentiation. Single-cell RNA sequencing analysis of public data was performed to identify key biological processes in macrophage subpopulations during DO. Western blot and immunofluorescence were used to measure expression and phosphorylation levels of SRC and STAT-6. Pathway inhibitors were applied to elucidate regulatory mechanisms. <em>In vivo</em>, Saracatinib and TGF-β were administered locally in DO models. Bone regeneration was evaluated using micro-CT, mechanical testing, and histology.</div></div><div><h3>Results</h3><div>DO significantly enhanced M2 macrophage polarization at 1st, 2nd, and 4th week post-surgery compared to controls. Cyclic stretch promoted M2 polarization <em>in vitro</em> and increased secretion of TGF-β and IL-10. Mechanically induced macrophages enhanced osteoblast differentiation in co-culture. Mechanical activation of the Integrin-SRC-STAT6 pathway drove M2 polarization. Local SRC inhibition suppressed M2 polarization and impaired bone regeneration in DO, which was partially rescued by TGF-β supplementation.</div></div><div><h3>Conclusion</h3><div>Mechanical stimulation during DO promotes M2 macrophage polarization via the Integrin-SRC-STAT6 pathway. TGF-β appears to be a key cytokine secreted by mechanically induced M2 macrophages that facilitates osteogenesis. These findings reveal a novel mechano-immune regulatory axis that supports bone regeneration in DO.</div></div><div><h3>The translational potential of this article</h3><div>This research confirms the core concept of "mechano-immunoregulation" and identifies actionable therapeutic targets, enabling the development of targeted therapies for refractory bone defects by modulating the integrin-β1/SRC/STAT6 pathway and TGF-β1 to enh
{"title":"Mechanotransduction-driven macrophage polarization via Integrin-SRC-STAT6 pathway in distraction osteogenesis","authors":"Xu Yan , Haixing Wang , Xuan Lu , Linlong Li , Shanshan Bai , Zitong Li , Han Su , Rongjie Wu , Hui Chen , Yinuo Fan , Jiting Liu , Xinkun Zhang , Lichun Xie , Ling Qin , Gang Li , Sien Lin","doi":"10.1016/j.jot.2025.10.016","DOIUrl":"10.1016/j.jot.2025.10.016","url":null,"abstract":"<div><h3>Background</h3><div>Mechanical stimuli are indispensable for bone regeneration. Distraction osteogenesis (DO) is a widely used clinical technique for limb lengthening and bone defect repair; however, its specific mechanobiological mechanisms remain unclear. Macrophages play crucial regulatory roles throughout bone fracture healing. Recent studies indicate that macrophages are mechanosensitive and can modulate the local immune microenvironment in response to mechanical cues. This study aims to investigate how macrophages respond to mechanical stimulation and regulate bone regeneration during DO.</div></div><div><h3>Methods</h3><div>Animal models of DO (with external fixation) and fracture healing (with internal fixation) were established to compare bone regeneration under different mechanical conditions. Immunohistochemistry (IHC) was used to quantify M1 and M2 macrophage infiltration. An <em>in vitro</em> model of cyclic mechanical stretch (10 %, 0.5 Hz, 12 h) was applied to RAW264.7 cells to study macrophage polarization. Flow cytometry, PCR, and western blot were used to assess macrophage phenotypes. An indirect co-culture system was employed to evaluate the effect of mechanically stimulated M2 macrophages on osteogenic differentiation. Single-cell RNA sequencing analysis of public data was performed to identify key biological processes in macrophage subpopulations during DO. Western blot and immunofluorescence were used to measure expression and phosphorylation levels of SRC and STAT-6. Pathway inhibitors were applied to elucidate regulatory mechanisms. <em>In vivo</em>, Saracatinib and TGF-β were administered locally in DO models. Bone regeneration was evaluated using micro-CT, mechanical testing, and histology.</div></div><div><h3>Results</h3><div>DO significantly enhanced M2 macrophage polarization at 1st, 2nd, and 4th week post-surgery compared to controls. Cyclic stretch promoted M2 polarization <em>in vitro</em> and increased secretion of TGF-β and IL-10. Mechanically induced macrophages enhanced osteoblast differentiation in co-culture. Mechanical activation of the Integrin-SRC-STAT6 pathway drove M2 polarization. Local SRC inhibition suppressed M2 polarization and impaired bone regeneration in DO, which was partially rescued by TGF-β supplementation.</div></div><div><h3>Conclusion</h3><div>Mechanical stimulation during DO promotes M2 macrophage polarization via the Integrin-SRC-STAT6 pathway. TGF-β appears to be a key cytokine secreted by mechanically induced M2 macrophages that facilitates osteogenesis. These findings reveal a novel mechano-immune regulatory axis that supports bone regeneration in DO.</div></div><div><h3>The translational potential of this article</h3><div>This research confirms the core concept of \"mechano-immunoregulation\" and identifies actionable therapeutic targets, enabling the development of targeted therapies for refractory bone defects by modulating the integrin-β1/SRC/STAT6 pathway and TGF-β1 to enh","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101024"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-12-23DOI: 10.1016/j.jot.2025.11.004
Mingjing Zhang , Shuzhong Liu , Jinyi Xing , An Song , Liqi Ng , Nan Tao , Xin Su , Changning Sun , Chaozong Liu
Critical-sized bone defect repair remains a major challenge in orthopaedics and tissue engineering. Polyetheretherketone (PEEK) has attracted wide attention due to its excellent mechanical compatibility and radiological transparency; however, its inherent bioinertness and insufficient antibacterial properties restrict its clinical utility. In recent years, the incorporation of graphene oxide (GO) has markedly improved the biological performance of PEEK. GO can increase surface hydrophilicity and roughness, enhance protein/ion adsorption, and promote osteoblast adhesion and differentiation, while simultaneously strengthening antibacterial and immunomodulatory effects without compromising, and in some cases even enhancing, mechanical performance. In vitro studies demonstrate that GO-PEEK stimulates osteogenic gene expression and mineralized nodule formation, while in vivo animal models confirm superior osseointegration and new bone formation compared with controls. Synergistic modifications, such as combination with hydroxyapatite, metallic ions, or antimicrobial peptides, further amplify both osteogenic and antibacterial outcomes. Nevertheless, clinical translation of GO-PEEK remains hampered by challenges including long-term stability, potential particulate-related risks, the dynamic balance between antibacterial and osteogenic functions, and issues of manufacturing scalability, consistency, and sterilization compatibility. Future research should focus on establishing a “structure–property–safety” design paradigm, developing temporally programmed multifunctional strategies, and advancing 3D-printed personalized fabrication, with low-load applications such as alveolar or cranial bone repair as potential pioneer indications. Overall, GO-PEEK composites exhibit significant promise in contexts such as post-tumour bone reconstruction, dental implantation, and spinal or joint implants, and are expected to achieve successful clinical translation under evidence-based validation and standardised manufacturing pathways.
The Translational Potential of this Article: The findings of this review highlight the potential of graphene oxide-modified PEEK (GO-PEEK) composites as next-generation orthopaedic biomaterials. By integrating enhanced osteogenic activity, antibacterial efficacy, and immunomodulatory capacity into a mechanically compatible and radiolucent polymer, GO-PEEK offers a multifunctional platform for bone repair. Importantly, its promising performance in vitro and in vivo provides a foundation for translation into clinical contexts such as dental implants, spinal fusion cages, and tumour-related bone defect reconstruction. Addressing challenges in long-term stability, sterilization compatibility, and large-scale manufacturing will be critical to establish a clear regulatory and translational pathway from laboratory research to clinical practice.
{"title":"Graphene oxide-modified PEEK composites: Properties and applications in orthopaedic repair — A review","authors":"Mingjing Zhang , Shuzhong Liu , Jinyi Xing , An Song , Liqi Ng , Nan Tao , Xin Su , Changning Sun , Chaozong Liu","doi":"10.1016/j.jot.2025.11.004","DOIUrl":"10.1016/j.jot.2025.11.004","url":null,"abstract":"<div><div>Critical-sized bone defect repair remains a major challenge in orthopaedics and tissue engineering. Polyetheretherketone (PEEK) has attracted wide attention due to its excellent mechanical compatibility and radiological transparency; however, its inherent bioinertness and insufficient antibacterial properties restrict its clinical utility. In recent years, the incorporation of graphene oxide (GO) has markedly improved the biological performance of PEEK. GO can increase surface hydrophilicity and roughness, enhance protein/ion adsorption, and promote osteoblast adhesion and differentiation, while simultaneously strengthening antibacterial and immunomodulatory effects without compromising, and in some cases even enhancing, mechanical performance. In vitro studies demonstrate that GO-PEEK stimulates osteogenic gene expression and mineralized nodule formation, while in vivo animal models confirm superior osseointegration and new bone formation compared with controls. Synergistic modifications, such as combination with hydroxyapatite, metallic ions, or antimicrobial peptides, further amplify both osteogenic and antibacterial outcomes. Nevertheless, clinical translation of GO-PEEK remains hampered by challenges including long-term stability, potential particulate-related risks, the dynamic balance between antibacterial and osteogenic functions, and issues of manufacturing scalability, consistency, and sterilization compatibility. Future research should focus on establishing a “structure–property–safety” design paradigm, developing temporally programmed multifunctional strategies, and advancing 3D-printed personalized fabrication, with low-load applications such as alveolar or cranial bone repair as potential pioneer indications. Overall, GO-PEEK composites exhibit significant promise in contexts such as post-tumour bone reconstruction, dental implantation, and spinal or joint implants, and are expected to achieve successful clinical translation under evidence-based validation and standardised manufacturing pathways.</div><div><strong><em>The Translational Potential of this Article</em></strong>: The findings of this review highlight the potential of graphene oxide-modified PEEK (GO-PEEK) composites as next-generation orthopaedic biomaterials. By integrating enhanced osteogenic activity, antibacterial efficacy, and immunomodulatory capacity into a mechanically compatible and radiolucent polymer, GO-PEEK offers a multifunctional platform for bone repair. Importantly, its promising performance in vitro and in vivo provides a foundation for translation into clinical contexts such as dental implants, spinal fusion cages, and tumour-related bone defect reconstruction. Addressing challenges in long-term stability, sterilization compatibility, and large-scale manufacturing will be critical to establish a clear regulatory and translational pathway from laboratory research to clinical practice.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101028"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2026-01-07DOI: 10.1016/j.jot.2025.101038
Huaqiang Tao , Gaoran Ge , Kai Chen , Tianrui Chen , Wenming Li , Peng Yang , Yunshu Che , Yufan Wang , Wenlong Chen , Hang Yu , Xing Yang , Jun Shen , Dechun Geng
<div><div>Redox homeostasis is crucial for maintaining cellular processes and is closely linked to human skeletal health. Prior research has demonstrated that oxidative stress is important for regulating osteoblast and osteoclast differentiation in the bone microenvironment, leading to a reduction in bone mass and skeletal degradation. The bone marrow is a complex niche containing various cell types, including bone marrow adipocytes (BMAs), which engage in dynamic interplay with osteo-associated cells through processes governed by redox equilibrium within the marrow compartment. During aging, a decrease in osteoblasts coincides with an increase in BMAs counts. Evidence suggests that oxidative stress influences the differentiation of BMAs, leading to the accumulation of bone marrow adipose tissue (BMAT) and contributing to bone remodeling imbalances. The fate of BMAs is determined by a precise molecular network that involves transcription factors, epigenetic regulators, and ncRNAs. The expansion of BMAT affects the commitment and differentiation of bone marrow-derived mesenchymal stem cells (BMSCs), resulting in poor osteoblast differentiation, enhancing osteoclast differentiation and function, and accelerating bone loss. Consequently, elucidating oxidative stress dynamics in pathological marrow states and delineating their correlation with aberrant BMAs differentiation emerges as a research imperative. This comprehensive review delineates the mechanistic interplay whereby oxidative stress within the osseous niche orchestrates BMAs differentiation, while simultaneously exploring how expanded BMAs reciprocally amplify oxidative stress levels. Furthermore, we dissect how maladaptive BMAs differentiation cascades perturb osteoblast-osteoclast equilibrium through paracrine signaling and microenvironmental reprogramming. By synthesizing these molecular insights, we aim to unravel the pathogenic nexus between BMAs-driven redox imbalance and compromised bone remodeling, ultimately proposing innovative therapeutic strategies for osteopathic disorders.</div><div>The translational potential of this article: The growing interest in BMAs originates from their significant yet underexplored functions in bone metabolism and systemic energy homeostasis, establishing them as a novel and promising component for managing osteoporosis and related metabolic bone disorders. Clinically, this focus addresses two critical gaps in current osteoporotic care, which predominantly relies on anti-resorptive agents and bone-forming medications. While these conventional treatments demonstrate efficacy, they face limitations such as potential long-term safety concerns, the presence of treatment-resistant patients, and an incomplete ability to restore bone quality and mechanical strength. Targeting BMAs presents a complementary or alternative therapeutic strategy by addressing a fundamental cellular element within the bone marrow microenvironment that actively participates in bone
{"title":"Oxidative stress and bone marrow adipocytes: Molecular mechanisms and possible implications","authors":"Huaqiang Tao , Gaoran Ge , Kai Chen , Tianrui Chen , Wenming Li , Peng Yang , Yunshu Che , Yufan Wang , Wenlong Chen , Hang Yu , Xing Yang , Jun Shen , Dechun Geng","doi":"10.1016/j.jot.2025.101038","DOIUrl":"10.1016/j.jot.2025.101038","url":null,"abstract":"<div><div>Redox homeostasis is crucial for maintaining cellular processes and is closely linked to human skeletal health. Prior research has demonstrated that oxidative stress is important for regulating osteoblast and osteoclast differentiation in the bone microenvironment, leading to a reduction in bone mass and skeletal degradation. The bone marrow is a complex niche containing various cell types, including bone marrow adipocytes (BMAs), which engage in dynamic interplay with osteo-associated cells through processes governed by redox equilibrium within the marrow compartment. During aging, a decrease in osteoblasts coincides with an increase in BMAs counts. Evidence suggests that oxidative stress influences the differentiation of BMAs, leading to the accumulation of bone marrow adipose tissue (BMAT) and contributing to bone remodeling imbalances. The fate of BMAs is determined by a precise molecular network that involves transcription factors, epigenetic regulators, and ncRNAs. The expansion of BMAT affects the commitment and differentiation of bone marrow-derived mesenchymal stem cells (BMSCs), resulting in poor osteoblast differentiation, enhancing osteoclast differentiation and function, and accelerating bone loss. Consequently, elucidating oxidative stress dynamics in pathological marrow states and delineating their correlation with aberrant BMAs differentiation emerges as a research imperative. This comprehensive review delineates the mechanistic interplay whereby oxidative stress within the osseous niche orchestrates BMAs differentiation, while simultaneously exploring how expanded BMAs reciprocally amplify oxidative stress levels. Furthermore, we dissect how maladaptive BMAs differentiation cascades perturb osteoblast-osteoclast equilibrium through paracrine signaling and microenvironmental reprogramming. By synthesizing these molecular insights, we aim to unravel the pathogenic nexus between BMAs-driven redox imbalance and compromised bone remodeling, ultimately proposing innovative therapeutic strategies for osteopathic disorders.</div><div>The translational potential of this article: The growing interest in BMAs originates from their significant yet underexplored functions in bone metabolism and systemic energy homeostasis, establishing them as a novel and promising component for managing osteoporosis and related metabolic bone disorders. Clinically, this focus addresses two critical gaps in current osteoporotic care, which predominantly relies on anti-resorptive agents and bone-forming medications. While these conventional treatments demonstrate efficacy, they face limitations such as potential long-term safety concerns, the presence of treatment-resistant patients, and an incomplete ability to restore bone quality and mechanical strength. Targeting BMAs presents a complementary or alternative therapeutic strategy by addressing a fundamental cellular element within the bone marrow microenvironment that actively participates in bone ","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101038"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2026-01-22DOI: 10.1016/j.jot.2025.101044
Yang Li , Sonu Ng , Keyu Kong , Minghao Jin , Wenxuan Fan , Wenjie Zhou , Zanjing Zhai , Huiwu Li
Depression and musculoskeletal disorders including osteoporosis (OP), fractures, osteoarthritis (OA) and rheumatoid arthritis (RA) exhibit significant bidirectional epidemiological and pathophysiological links. Rising depression prevalence (approximately 2.7 % annually) is accompanied by the high global burden of musculoskeletal disorders. Shared mechanisms center on the neuroimmune–inflammatory axis: Depression-associated inflammation (e.g., IL-6, TNF-α) promotes bone resorption, cartilage degradation, and RA disease activity, while autonomic/endocrine dysregulation increases fracture risk through increased norepinephrine (NE) and cortisol. Contributing factors include oxidative stress, gut dysbiosis, and sex hormone imbalances. Antidepressants show divergent skeletal effects: selective serotonin reuptake inhibitors (SSRIs) may reduce bone mineral density (BMD) and increase fracture risk, while serotonin-norepinephrine reuptake inhibitors (SNRIs) can improve OA symptoms. Depression significantly worsens orthopedic outcomes, leading to increased fracture risk, pain and disability, reduced treatment response. Integrated care approaches and novel neuroimmune targets offer potential for improved comorbidity management.
The Translational Potential of this Article
This review links depression with common orthopaedic disorders by synthesizing convergent neuro-immune-endocrine and metabolic pathways, and documents measurable skeletal deficits. These insights support immediate, low-cost actions: bidirectional screening, strengthened orthopaedics–psychiatry referral, and pragmatic combination care bundles. If implemented, this approach could reduce fracture risk, pain, and disability while improving recovery trajectories.
{"title":"Brain–bone axis dysregulation: Biological code underlying the bidirectional association between depression and musculoskeletal disorders","authors":"Yang Li , Sonu Ng , Keyu Kong , Minghao Jin , Wenxuan Fan , Wenjie Zhou , Zanjing Zhai , Huiwu Li","doi":"10.1016/j.jot.2025.101044","DOIUrl":"10.1016/j.jot.2025.101044","url":null,"abstract":"<div><div>Depression and musculoskeletal disorders including osteoporosis (OP), fractures, osteoarthritis (OA) and rheumatoid arthritis (RA) exhibit significant bidirectional epidemiological and pathophysiological links. Rising depression prevalence (approximately 2.7 % annually) is accompanied by the high global burden of musculoskeletal disorders. Shared mechanisms center on the neuroimmune–inflammatory axis: Depression-associated inflammation (e.g., IL-6, TNF-α) promotes bone resorption, cartilage degradation, and RA disease activity, while autonomic/endocrine dysregulation increases fracture risk through increased norepinephrine (NE) and cortisol. Contributing factors include oxidative stress, gut dysbiosis, and sex hormone imbalances. Antidepressants show divergent skeletal effects: selective serotonin reuptake inhibitors (SSRIs) may reduce bone mineral density (BMD) and increase fracture risk, while serotonin-norepinephrine reuptake inhibitors (SNRIs) can improve OA symptoms. Depression significantly worsens orthopedic outcomes, leading to increased fracture risk, pain and disability, reduced treatment response. Integrated care approaches and novel neuroimmune targets offer potential for improved comorbidity management.</div></div><div><h3>The Translational Potential of this Article</h3><div>This review links depression with common orthopaedic disorders by synthesizing convergent neuro-immune-endocrine and metabolic pathways, and documents measurable skeletal deficits. These insights support immediate, low-cost actions: bidirectional screening, strengthened orthopaedics–psychiatry referral, and pragmatic combination care bundles. If implemented, this approach could reduce fracture risk, pain, and disability while improving recovery trajectories.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101044"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2026-01-13DOI: 10.1016/j.jot.2025.101037
Xiuqin Peng , Jiaming Han , Yu Tian , Xiaohong Li , Xuanqi Zhang , Song Li , Jun Yang , Liang Chen , Siru Zhou , Nan Su , Xueqin Mao , Bin Zhang , Hangang Chen , Jing Yang , Min Jin , Can Li , Wanling Jiang , Peng Liu , Yangli Xie , Liang Kuang , Lin Chen
Objective
Osteoarthritis (OA) is a chronic disease characterized by degeneration of articular cartilage, affecting over half a billion individuals globally. Current treatments such as non-steroidal anti-inflammatory drugs are effective in symptom relief, but lack the ability to modify OA progression. Fibroblast growth factor 8b (FGF8b) plays crucial roles in chondrogenesis and cartilage formation, suggesting its potential application in cartilage homeostasis maintenance. This study aims to investigate the effect of exogenous FGF8b on cartilage protection and OA progression, and explore the underlying mechanisms.
Design
Therapeutic effects of intra-articular FGF8b injections either once weekly or once every four weeks were evaluated in OA mouse models induced by destabilization of the medial meniscus (DMM) using histological analysis, X-ray imaging, micro-computed tomography (micro-CT), immunohistochemistry (IHC), and RNA sequencing of cartilage. Additionally, the therapeutic effects and underlying mechanisms of FGF8b on human cartilage and chondrocytes were further investigated using ex vivo OA models and in vitro assays.
Results
Once-weekly administration of FGF8b attenuated cartilage degradation while exacerbating osteophyte formation in a dose-dependent manner. Higher doses of FGF8b resulted in stronger cartilage-protective effects while increased osteophyte formation. Conversely, intermittent administration of FGF8b (once every four weeks) protected cartilage from degeneration without causing significant osteophyte formation. Mechanistically, FGF8b was found to help the maintenance of cartilage homeostasis by promoting anabolic metabolism and inhibiting catabolic metabolism in chondrocytes through activation of the FGFR3-PI3K-AKT signaling pathway.
Conclusions
Exogenous FGF8b attenuates articular cartilage degeneration by increasing anabolism and inhibiting catabolism, thereby presenting therapeutic potential for OA treatment.
The translational potential of this article
In this study, we demonstrate that intermittent administration of FGF8b protects articular cartilage from degeneration by increasing anabolic metabolism and inhibiting catabolic metabolism in cartilage, making it a promising disease-modifying agent for OA. Moreover, the findings offer valuable insights into optimizing the exposure regimens of FGFs to achieve safer and more effective OA treatment.
{"title":"Intermittent intra-articular delivery of FGF8b enhances cartilage homeostasis and attenuates osteoarthritis progression","authors":"Xiuqin Peng , Jiaming Han , Yu Tian , Xiaohong Li , Xuanqi Zhang , Song Li , Jun Yang , Liang Chen , Siru Zhou , Nan Su , Xueqin Mao , Bin Zhang , Hangang Chen , Jing Yang , Min Jin , Can Li , Wanling Jiang , Peng Liu , Yangli Xie , Liang Kuang , Lin Chen","doi":"10.1016/j.jot.2025.101037","DOIUrl":"10.1016/j.jot.2025.101037","url":null,"abstract":"<div><h3>Objective</h3><div>Osteoarthritis (OA) is a chronic disease characterized by degeneration of articular cartilage, affecting over half a billion individuals globally. Current treatments such as non-steroidal anti-inflammatory drugs are effective in symptom relief, but lack the ability to modify OA progression. Fibroblast growth factor 8b (FGF8b) plays crucial roles in chondrogenesis and cartilage formation, suggesting its potential application in cartilage homeostasis maintenance. This study aims to investigate the effect of exogenous FGF8b on cartilage protection and OA progression, and explore the underlying mechanisms.</div></div><div><h3>Design</h3><div>Therapeutic effects of intra-articular FGF8b injections either once weekly or once every four weeks were evaluated in OA mouse models induced by destabilization of the medial meniscus (DMM) using histological analysis, X-ray imaging, micro-computed tomography (micro-CT), immunohistochemistry (IHC), and RNA sequencing of cartilage. Additionally, the therapeutic effects and underlying mechanisms of FGF8b on human cartilage and chondrocytes were further investigated using ex vivo OA models and in vitro assays.</div></div><div><h3>Results</h3><div>Once-weekly administration of FGF8b attenuated cartilage degradation while exacerbating osteophyte formation in a dose-dependent manner. Higher doses of FGF8b resulted in stronger cartilage-protective effects while increased osteophyte formation. Conversely, intermittent administration of FGF8b (once every four weeks) protected cartilage from degeneration without causing significant osteophyte formation. Mechanistically, FGF8b was found to help the maintenance of cartilage homeostasis by promoting anabolic metabolism and inhibiting catabolic metabolism in chondrocytes through activation of the FGFR3-PI3K-AKT signaling pathway.</div></div><div><h3>Conclusions</h3><div>Exogenous FGF8b attenuates articular cartilage degeneration by increasing anabolism and inhibiting catabolism, thereby presenting therapeutic potential for OA treatment.</div></div><div><h3>The translational potential of this article</h3><div>In this study, we demonstrate that intermittent administration of FGF8b protects articular cartilage from degeneration by increasing anabolic metabolism and inhibiting catabolic metabolism in cartilage, making it a promising disease-modifying agent for OA. Moreover, the findings offer valuable insights into optimizing the exposure regimens of FGFs to achieve safer and more effective OA treatment.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101037"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147419918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2026-02-11DOI: 10.1016/j.jot.2025.101032
Gang Li , Le Wang , Xiaoyu Wu , Xiaolin Zeng , Lingli Long , Wenwu Zhang , Jiewen Chen , Di Zhang , Xi Chen , YiLong Deng , XinZhi , Yong Wan , Xiang Li
Introduction
Spinal cord injury (SCI) induces fibrotic scarring that impairs axonal regeneration. Pericytes contribute to scar formation via pericyte-to-myofibroblast transition (PMT), yet the mechanisms underlying PMT in SCI remain unclear. Although CXCL4, a pleiotropic chemokine, is implicated in various fibrotic disorders, its role in driving PMT post-SCI remains unexplored.
Objectives
To investigate whether CXCL4 drives PMT after SCI, elucidate its mechanisms, and assess its therapeutic potential.
Methods
scRNA-seq characterized cell-type dynamics and profibrotic signals in injured mouse spinal cords. In vitro, primary pericytes were exposed to exogenous CXCL4 or co-cultured with Spp1+Fn1+ macrophages. PMT was evaluated by RT-qPCR, Western blot, immunofluorescence, and flow cytometry. PI3K/Akt inhibition or CXCR3 knockdown dissected signaling pathways. In vivo, intrathecal injections of a CXCL4-neutralizing antibody or PI3K inhibitor were administered post-injury. Pericyte differentiation and fibrotic remodeling were assessed via immunostaining, Masson's trichrome staining, and gene expression profiling. Axonal regeneration and motor function were evaluated using CST tracing, serotonergic fiber labeling, Basso Mouse Scale scoring, and footprint analysis.
Results
PMT occurred post SCI, with Pdgfrβ+Acta2+ pericytes acting as major contributors. Spp1+Fn1+ macrophage subpopulation was identified as the main source of CXCL4, transcriptionally regulated by MAFB. CXCL4 levels were significantly upregulated post-injury, while pericytes in the lesion expressed its receptor, CXCR3. In vitro, exogenous CXCL4 induced PMT in pericytes via PI3K/Akt signaling. Co-culture experiments confirmed that Spp1+Fn1+ macrophages promoted pericyte transition through the CXCL4/CXCR3 axis. In vivo, blocking CXCL4 or PI3K suppressed PMT, reduced fibrotic scarring, enhanced axonal regeneration, and improved locomotor function in SCI mice.
Conclusion
Profibrotic macrophage-derived CXCL4 activates CXCR3/PI3K/Akt signaling in pericytes, driving their transition into scar-forming myofibroblasts after SCI. Blocking this axis mitigates fibrosis and enhances axonal regeneration and motor recovery.
The translational potential of this article
This study indicates that targeting the CXCL4-driven pericyte-to-myofibroblast transition to reduce fibrotic scar formation may provide an effective therapeutic strategy for enhancing axonal regeneration and functional recovery after SCI.
{"title":"Profibrotic macrophage-derived CXCL4 promotes pericyte-to-myofibroblast transition after spinal cord injury","authors":"Gang Li , Le Wang , Xiaoyu Wu , Xiaolin Zeng , Lingli Long , Wenwu Zhang , Jiewen Chen , Di Zhang , Xi Chen , YiLong Deng , XinZhi , Yong Wan , Xiang Li","doi":"10.1016/j.jot.2025.101032","DOIUrl":"10.1016/j.jot.2025.101032","url":null,"abstract":"<div><h3>Introduction</h3><div>Spinal cord injury (SCI) induces fibrotic scarring that impairs axonal regeneration. Pericytes contribute to scar formation via pericyte-to-myofibroblast transition (PMT), yet the mechanisms underlying PMT in SCI remain unclear. Although CXCL4, a pleiotropic chemokine, is implicated in various fibrotic disorders, its role in driving PMT post-SCI remains unexplored.</div></div><div><h3>Objectives</h3><div>To investigate whether CXCL4 drives PMT after SCI, elucidate its mechanisms, and assess its therapeutic potential.</div></div><div><h3>Methods</h3><div>scRNA-seq characterized cell-type dynamics and profibrotic signals in injured mouse spinal cords. <em>In vitro</em>, primary pericytes were exposed to exogenous CXCL4 or co-cultured with Spp1<sup>+</sup>Fn1<sup>+</sup> macrophages. PMT was evaluated by RT-qPCR, Western blot, immunofluorescence, and flow cytometry. PI3K/Akt inhibition or CXCR3 knockdown dissected signaling pathways. <em>In vivo</em>, intrathecal injections of a CXCL4-neutralizing antibody or PI3K inhibitor were administered post-injury. Pericyte differentiation and fibrotic remodeling were assessed via immunostaining, Masson's trichrome staining, and gene expression profiling. Axonal regeneration and motor function were evaluated using CST tracing, serotonergic fiber labeling, Basso Mouse Scale scoring, and footprint analysis.</div></div><div><h3>Results</h3><div>PMT occurred post SCI, with Pdgfrβ<sup>+</sup>Acta2<sup>+</sup> pericytes acting as major contributors. Spp1<sup>+</sup>Fn1<sup>+</sup> macrophage subpopulation was identified as the main source of CXCL4, transcriptionally regulated by MAFB. CXCL4 levels were significantly upregulated post-injury, while pericytes in the lesion expressed its receptor, CXCR3. <em>In vitro</em>, exogenous CXCL4 induced PMT in pericytes via PI3K/Akt signaling. Co-culture experiments confirmed that Spp1<sup>+</sup>Fn1<sup>+</sup> macrophages promoted pericyte transition through the CXCL4/CXCR3 axis. <em>In vivo</em>, blocking CXCL4 or PI3K suppressed PMT, reduced fibrotic scarring, enhanced axonal regeneration, and improved locomotor function in SCI mice.</div></div><div><h3>Conclusion</h3><div>Profibrotic macrophage-derived CXCL4 activates CXCR3/PI3K/Akt signaling in pericytes, driving their transition into scar-forming myofibroblasts after SCI. Blocking this axis mitigates fibrosis and enhances axonal regeneration and motor recovery.</div></div><div><h3>The translational potential of this article</h3><div>This study indicates that targeting the CXCL4-driven pericyte-to-myofibroblast transition to reduce fibrotic scar formation may provide an effective therapeutic strategy for enhancing axonal regeneration and functional recovery after SCI.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101032"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-12-01DOI: 10.1016/j.jot.2025.10.013
Yiting Lei , Yuwei Zhang , Liangbin Zhou , Zhilong Zhou , Mario Rothbauer , Long Bai , Jiankun Xu , Denghui Xie , Ali Mobasheri , Xin Zhang , Dongquan Shi , Changhai Ding , Jiake Xu , Wei Huang , Shiqing Feng , Liu Yang , Yuxiao Lai , Guanghua Lei , Zhuojing Luo , Chenzhong Li , Zhong Alan Li
While conventional in vitro and in vivo models of orthopaedic conditions have yielded valuable insights into disease mechanisms and drug efficacy, only a few discoveries have been successfully translated to clinical practice. Organoids and organs-on-chips (OoCs) are transforming orthopaedic translation by providing 3D customizable models that aim to faithfully recapitulate musculoskeletal (MSK) (patho)physiology. Using joint-mimicking OoCs and skeletal muscle organoids as examples, we review the evolution of these systems that have been developed to model the pathogenesis, progression, prognosis, and treatment of orthopaedic conditions. We highlight how organoid and OoC models recapitulate multi-tissue crosstalk, drug responses, and disease heterogeneity. Furthermore, we summarize and discuss the global regulatory landscape for organoids and OoCs. Current global regulatory trends support the potential of these human-centric platforms as alternatives, or even future replacements for animal testing. Looking ahead, organoids and OoCs are gaining increasing attention in AI-guided drug development, patient stratification, and regenerative medicine evaluation. The ongoing rapid developments are expected to position organoids and OoCs at the forefront of precision orthopaedics.
The translational potential of this article
This article accelerates the clinical translation of orthopaedic discoveries by demonstrating how OoCs and organoids can be positioned as regulatory-ready alternatives to animal studies. Using joint-on-a-chip systems and skeletal muscle organoid as examples, we review the technological development of these platforms. By connecting recent policy shifts from key global regulators, including the U.S. Food and Drug Administration (FDA), European Medicines Agency (EMA), China National Medical Products Administration (NMPA), and Pharmaceuticals and Medical Devices Agency (PMDA), to practical model qualification steps, we provide clinicians, industry, and regulators with a clear pathway to adopt OoCs and organoids. This process will facilitate their use as human-centric systems for patient stratification, implant safety evaluation, and disease-modifying drug development within the 3Rs (Replacement, Reduction, and Refinement) framework.
{"title":"Organoids and organs-on-chips for accelerating R&D and clinical translation in Orthopaedics: Emerging opportunities and regulatory pathways","authors":"Yiting Lei , Yuwei Zhang , Liangbin Zhou , Zhilong Zhou , Mario Rothbauer , Long Bai , Jiankun Xu , Denghui Xie , Ali Mobasheri , Xin Zhang , Dongquan Shi , Changhai Ding , Jiake Xu , Wei Huang , Shiqing Feng , Liu Yang , Yuxiao Lai , Guanghua Lei , Zhuojing Luo , Chenzhong Li , Zhong Alan Li","doi":"10.1016/j.jot.2025.10.013","DOIUrl":"10.1016/j.jot.2025.10.013","url":null,"abstract":"<div><div>While conventional <em>in vitro</em> and <em>in vivo</em> models of orthopaedic conditions have yielded valuable insights into disease mechanisms and drug efficacy, only a few discoveries have been successfully translated to clinical practice. Organoids and organs-on-chips (OoCs) are transforming orthopaedic translation by providing 3D customizable models that aim to faithfully recapitulate musculoskeletal (MSK) (patho)physiology. Using joint-mimicking OoCs and skeletal muscle organoids as examples, we review the evolution of these systems that have been developed to model the pathogenesis, progression, prognosis, and treatment of orthopaedic conditions. We highlight how organoid and OoC models recapitulate multi-tissue crosstalk, drug responses, and disease heterogeneity. Furthermore, we summarize and discuss the global regulatory landscape for organoids and OoCs. Current global regulatory trends support the potential of these human-centric platforms as alternatives, or even future replacements for animal testing. Looking ahead, organoids and OoCs are gaining increasing attention in AI-guided drug development, patient stratification, and regenerative medicine evaluation. The ongoing rapid developments are expected to position organoids and OoCs at the forefront of precision orthopaedics.</div></div><div><h3>The translational potential of this article</h3><div>This article accelerates the clinical translation of orthopaedic discoveries by demonstrating how OoCs and organoids can be positioned as regulatory-ready alternatives to animal studies. Using joint-on-a-chip systems and skeletal muscle organoid as examples, we review the technological development of these platforms. By connecting recent policy shifts from key global regulators, including the U.S. Food and Drug Administration (FDA), European Medicines Agency (EMA), China National Medical Products Administration (NMPA), and Pharmaceuticals and Medical Devices Agency (PMDA), to practical model qualification steps, we provide clinicians, industry, and regulators with a clear pathway to adopt OoCs and organoids. This process will facilitate their use as human-centric systems for patient stratification, implant safety evaluation, and disease-modifying drug development within the 3Rs (Replacement, Reduction, and Refinement) framework.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101021"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2026-01-12DOI: 10.1016/j.jot.2025.101039
Zhenyu Zhu , Xiaofeng Lin , Fanqi Kong , Ziran Wang , Yongcheng Liang , Chenglong Ji , Hongxuan Chen , Kaiqiang Sun , Changnan Wang , Ximing Xu , Jiangang Shi
Background
Intervertebral disc degeneration (IVDD) is a leading cause of chronic low back pain. Programmed cell death, particularly necroptosis, contributes to nucleus pulposus (NP) cell loss. Mixed lineage kinase domain-like protein (MLKL) phosphorylation plays a critical role in necroptotic execution, but its upstream regulation in IVDD remains poorly defined.
Methods
We analyzed human and mouse degenerative disc tissues, as well as TNF-α/Smac mimetic/Z-VAD-FMK (TSZ)-treated NP cells, to assess MLKL phosphorylation. MLKL knockdown in human NP cells and conditional knockout (CKO) in mice were performed to determine its functional role. Immunoprecipitation coupled with mass spectrometry identified potential MLKL-binding proteins. Functional assays with USP39 knockdown/overexpression, together with in vitro and in vivo IVDD models, were conducted to explore regulatory mechanisms.
Results
MLKL phosphorylation was markedly elevated in human IVDD tissues, LSI-induced mouse discs, and TSZ-stimulated NP cells. Genetic knockdown or conditional deletion of Mlkl significantly preserved extracellular matrix integrity and delayed degeneration. USP39 was identified as a novel MLKL-interacting deubiquitinase. USP39 expression was reduced in IVDD, and its overexpression inhibited MLKL ubiquitination and phosphorylation, alleviating NP cell degeneration. In vivo, AAV-mediated Usp39 delivery attenuated disc degeneration and suppressed MLKL activation.
Conclusion
Our study reveals that MLKL phosphorylation drives necroptosis in IVDD and identifies USP39 as a critical upstream regulator that deubiquitinates MLKL. Targeting the USP39-MLKL axis provides a promising therapeutic strategy for delaying IVDD progression.
The Translational Potential of this Article
This study reveals that USP39 inhibits MLKL phosphorylation through deubiquitination, thereby suppressing necroptosis of nucleus pulposus cells and alleviating IVDD. Targeting the USP39–MLKL axis provides a potential therapeutic strategy to preserve NP cell viability and slow the progression of IVDD, offering new insight for translational interventions in chronic low back pain.
{"title":"USP39 inhibits MLKL phosphorylation and deubiquitination to suppress necroptosis of nucleus pulposus cells and attenuate intervertebral disc degeneration","authors":"Zhenyu Zhu , Xiaofeng Lin , Fanqi Kong , Ziran Wang , Yongcheng Liang , Chenglong Ji , Hongxuan Chen , Kaiqiang Sun , Changnan Wang , Ximing Xu , Jiangang Shi","doi":"10.1016/j.jot.2025.101039","DOIUrl":"10.1016/j.jot.2025.101039","url":null,"abstract":"<div><h3>Background</h3><div>Intervertebral disc degeneration (IVDD) is a leading cause of chronic low back pain. Programmed cell death, particularly necroptosis, contributes to nucleus pulposus (NP) cell loss. Mixed lineage kinase domain-like protein (MLKL) phosphorylation plays a critical role in necroptotic execution, but its upstream regulation in IVDD remains poorly defined.</div></div><div><h3>Methods</h3><div>We analyzed human and mouse degenerative disc tissues, as well as TNF-α/Smac mimetic/Z-VAD-FMK (TSZ)-treated NP cells, to assess MLKL phosphorylation. MLKL knockdown in human NP cells and conditional knockout (CKO) in mice were performed to determine its functional role. Immunoprecipitation coupled with mass spectrometry identified potential MLKL-binding proteins. Functional assays with USP39 knockdown/overexpression, together with in vitro and in vivo IVDD models, were conducted to explore regulatory mechanisms.</div></div><div><h3>Results</h3><div>MLKL phosphorylation was markedly elevated in human IVDD tissues, LSI-induced mouse discs, and TSZ-stimulated NP cells. Genetic knockdown or conditional deletion of Mlkl significantly preserved extracellular matrix integrity and delayed degeneration. USP39 was identified as a novel MLKL-interacting deubiquitinase. USP39 expression was reduced in IVDD, and its overexpression inhibited MLKL ubiquitination and phosphorylation, alleviating NP cell degeneration. In vivo, AAV-mediated Usp39 delivery attenuated disc degeneration and suppressed MLKL activation.</div></div><div><h3>Conclusion</h3><div>Our study reveals that MLKL phosphorylation drives necroptosis in IVDD and identifies USP39 as a critical upstream regulator that deubiquitinates MLKL. Targeting the USP39-MLKL axis provides a promising therapeutic strategy for delaying IVDD progression.</div></div><div><h3>The Translational Potential of this Article</h3><div>This study reveals that USP39 inhibits MLKL phosphorylation through deubiquitination, thereby suppressing necroptosis of nucleus pulposus cells and alleviating IVDD. Targeting the USP39–MLKL axis provides a potential therapeutic strategy to preserve NP cell viability and slow the progression of IVDD, offering new insight for translational interventions in chronic low back pain.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101039"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147419919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-27DOI: 10.1016/j.jot.2025.10.009
Andrea Mainardi , Andrea Barbero , Martin Ehrbar , Marco Rasponi , Ivan Martin , Paola Occhetta
Background
Homeostasis at the cartilage–bone interface of articular joints depends on tightly orchestrated signalling among chondrocytes, osteogenic progenitors, and subchondral vasculature. Disruption of this crosstalk is considered one of the main drivers of osteoarthritis (OA), the most prevalent musculoskeletal disease worldwide. However, the timing, location, and mechanisms underlying the pathological onset of OA remain unclear, hindering the development of targeted regenerative strategies. This knowledge gap emphasises the need for in vitro models that replicate OA's multi-tissue crosstalk in a representative yet accessible format.
Methods and results
Here, we present a modular, dual-compartment Organ-on-Chip (OoC) platform that enables the stepwise ‘de- and re-construction’ of the vascularized osteochondral unit, allowing systematic interrogation of cell-specific roles in homeostasis and inflammation. Through the side-by-side culture of human articular chondrocytes (hACs) and bone marrow-derived mesenchymal stromal cells (bmMSCs), we generated biphasic, compartmentalized constructs with a contiguous interface, in which bmMSCs exhibited osteogenic commitment without compromising the stable chondrogenic capacity of hACs. The addition of human umbilical vein endothelial cells (HUVECs) to the bmMSCs compartment at a finely tuned 3:2 ratio (bmMSCs:HUVECs) enabled the formation of lumenized vascular vessels surrounded by α-SMA–expressing cells and laminin sheaths, while preserving bmMSCs' osteogenic commitment. Under homeostatic conditions, the presence of a cartilage layer adjacent to such vascularized and mineralized tissue impeded vascular and stromal invasion, whereas exposure to IL-1β (1 ng/mL) allowed to override such chondrocyte “barrier,” triggering endothelial and stromal penetration into the cartilage, thus mimicking inflammatory OA.
Conclusion
The proposed platform combines ease of use, real-time imaging capabilities, and precise control over cellular modules, offering a versatile tool for future mechanistic studies in OA and related joint disorders.
The translational potential of this article
This modular Organ-on-Chip platform offers a physiologically relevant and experimentally accessible model of the vascularized osteochondral interface, enabling systematic dissection of cell-specific roles in joint homeostasis and inflammation. By recapitulating key features of early osteoarthritic pathology—including barrier breakdown, stromal invasion, and endothelial remodeling— with a highly modular and technologically robust approach, this system holds translational promise for preclinical testing of disease-modifying OA therapies, biomarker discovery, and regenerative strategies targeting cartilage–bone crosstalk.
{"title":"Modular de- and re-construction of vascularized osteochondral tissues in an Organ-on-Chip dual-compartment platform","authors":"Andrea Mainardi , Andrea Barbero , Martin Ehrbar , Marco Rasponi , Ivan Martin , Paola Occhetta","doi":"10.1016/j.jot.2025.10.009","DOIUrl":"10.1016/j.jot.2025.10.009","url":null,"abstract":"<div><h3>Background</h3><div>Homeostasis at the cartilage–bone interface of articular joints depends on tightly orchestrated signalling among chondrocytes, osteogenic progenitors, and subchondral vasculature. Disruption of this crosstalk is considered one of the main drivers of osteoarthritis (OA), the most prevalent musculoskeletal disease worldwide. However, the timing, location, and mechanisms underlying the pathological onset of OA remain unclear, hindering the development of targeted regenerative strategies. This knowledge gap emphasises the need for <em>in vitro</em> models that replicate OA's multi-tissue crosstalk in a representative yet accessible format.</div></div><div><h3>Methods and results</h3><div>Here, we present a modular, dual-compartment Organ-on-Chip (OoC) platform that enables the stepwise ‘de- and re-construction’ of the vascularized osteochondral unit, allowing systematic interrogation of cell-specific roles in homeostasis and inflammation. Through the side-by-side culture of human articular chondrocytes (hACs) and bone marrow-derived mesenchymal stromal cells (bmMSCs), we generated biphasic, compartmentalized constructs with a contiguous interface, in which bmMSCs exhibited osteogenic commitment without compromising the stable chondrogenic capacity of hACs. The addition of human umbilical vein endothelial cells (HUVECs) to the bmMSCs compartment at a finely tuned 3:2 ratio (bmMSCs:HUVECs) enabled the formation of lumenized vascular vessels surrounded by α-SMA–expressing cells and laminin sheaths, while preserving bmMSCs' osteogenic commitment. Under homeostatic conditions, the presence of a cartilage layer adjacent to such vascularized and mineralized tissue impeded vascular and stromal invasion, whereas exposure to IL-1β (1 ng/mL) allowed to override such chondrocyte “barrier,” triggering endothelial and stromal penetration into the cartilage, thus mimicking inflammatory OA.</div></div><div><h3>Conclusion</h3><div>The proposed platform combines ease of use, real-time imaging capabilities, and precise control over cellular modules, offering a versatile tool for future mechanistic studies in OA and related joint disorders.</div></div><div><h3>The translational potential of this article</h3><div>This modular Organ-on-Chip platform offers a physiologically relevant and experimentally accessible model of the vascularized osteochondral interface, enabling systematic dissection of cell-specific roles in joint homeostasis and inflammation. By recapitulating key features of early osteoarthritic pathology—including barrier breakdown, stromal invasion, and endothelial remodeling— with a highly modular and technologically robust approach, this system holds translational promise for preclinical testing of disease-modifying OA therapies, biomarker discovery, and regenerative strategies targeting cartilage–bone crosstalk.</div></div>","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101017"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-12-20DOI: 10.1016/j.jot.2025.10.011
Aoyuan Fan , Zhiying Pang , Zheng Liu , Feng Yin , Yiming Wang
<div><h3>Introduction</h3><div>Osteoarthritis (OA) is a prevalent degenerative joint disease driven largely by chondrocyte senescence. Extracellular vesicle (EV)-based therapies have emerged as a promising strategy; however, the extensive stem-cell expansion required to obtain therapeutic EV doses unavoidably erodes their potency.</div></div><div><h3>Objectives</h3><div>Leveraging our prior finding that decellularized extracellular matrix (dECM) rejuvenates stem cells during in vitro expansion, we further investigate whether dECM could resolve the current bottleneck in EV therapy by preserving therapeutic efficacy even in late-passage cells.</div></div><div><h3>Methods</h3><div>Human adipose-derived stromal cells (hADSCs) were expanded to passage 15 on either tissue culture plastic (TCP) or dECM, and their EVs were isolated. We first interrogated the capacity of dECM-primed EVs to counteract chondrocyte senescence and ER stress in vitro, then validated their therapeutic impact in a rat OA model. Mechanistic insight was pursued through proteomic profiling, followed by loss- and gain-of-function studies using pharmacologic inhibitors and targeted knockdown.</div></div><div><h3>Results</h3><div>Late-passage EVs generated under dECM (dECM-P15-EVs) surpassed those under TCP (TCP-P15-EVs) in alleviating chondrocyte senescence and ER stress. In vivo, dECM-P15-EVs attenuated cartilage degradation more effectively than their conventionally cultured counterparts. Proteomics revealed dECM-P15-EVs were enriched in both FN and its receptor integrin β1 (ITGB1). Either pharmacologic blockade or siRNA-mediated knockdown of FN in dECM or of ITGB1 in EV-producing cells abrogated the anti-senescence and chondro-protective benefits of dECM-P15-EVs. Further experiments implicated FN/ITGB1 transfer as a critical step in re-activating downstream SIRT1 signaling.</div></div><div><h3>Conclusion</h3><div>By reinstating FN/ITGB1 homeostasis and reinvigorating SIRT1-dependent pathways, dECM-P15-EVs effectively counteract chondrocyte senescence and OA progression—offering a scalable, senescence-resistant platform for next-generation EV therapy.</div><div>The Translational Potential of this Article: Producing the large quantities of EVs required for clinical OA therapy necessitates prolonged expansion of stem cells, which inevitably blunts EV efficacy. dECM culture restores the potency of EVs without additional biosafety concerns. Thus, dECM-P15-EVs offer strong translational promise as an advanced, EV-centric OA therapy that overcomes current limitations.</div></div><div><h3>The translational potential of this article</h3><div>Producing the large quantities of EVs required for clinical OA therapy necessitates prolonged expansion of stem cells, which inevitably blunts EV efficacy. dECM culture restores the potency of EVs without additional biosafety concerns. Thus, dECM-P15-EVs offer strong translational promise as an advanced, EV-centric OA therapy that overcomes current lim
{"title":"Decellularized extracellular matrix restores Fibronectin/Integrin β1 balance through extracellular vesicles to rejuvenate chondrocytes and alleviate osteoarthritis progression","authors":"Aoyuan Fan , Zhiying Pang , Zheng Liu , Feng Yin , Yiming Wang","doi":"10.1016/j.jot.2025.10.011","DOIUrl":"10.1016/j.jot.2025.10.011","url":null,"abstract":"<div><h3>Introduction</h3><div>Osteoarthritis (OA) is a prevalent degenerative joint disease driven largely by chondrocyte senescence. Extracellular vesicle (EV)-based therapies have emerged as a promising strategy; however, the extensive stem-cell expansion required to obtain therapeutic EV doses unavoidably erodes their potency.</div></div><div><h3>Objectives</h3><div>Leveraging our prior finding that decellularized extracellular matrix (dECM) rejuvenates stem cells during in vitro expansion, we further investigate whether dECM could resolve the current bottleneck in EV therapy by preserving therapeutic efficacy even in late-passage cells.</div></div><div><h3>Methods</h3><div>Human adipose-derived stromal cells (hADSCs) were expanded to passage 15 on either tissue culture plastic (TCP) or dECM, and their EVs were isolated. We first interrogated the capacity of dECM-primed EVs to counteract chondrocyte senescence and ER stress in vitro, then validated their therapeutic impact in a rat OA model. Mechanistic insight was pursued through proteomic profiling, followed by loss- and gain-of-function studies using pharmacologic inhibitors and targeted knockdown.</div></div><div><h3>Results</h3><div>Late-passage EVs generated under dECM (dECM-P15-EVs) surpassed those under TCP (TCP-P15-EVs) in alleviating chondrocyte senescence and ER stress. In vivo, dECM-P15-EVs attenuated cartilage degradation more effectively than their conventionally cultured counterparts. Proteomics revealed dECM-P15-EVs were enriched in both FN and its receptor integrin β1 (ITGB1). Either pharmacologic blockade or siRNA-mediated knockdown of FN in dECM or of ITGB1 in EV-producing cells abrogated the anti-senescence and chondro-protective benefits of dECM-P15-EVs. Further experiments implicated FN/ITGB1 transfer as a critical step in re-activating downstream SIRT1 signaling.</div></div><div><h3>Conclusion</h3><div>By reinstating FN/ITGB1 homeostasis and reinvigorating SIRT1-dependent pathways, dECM-P15-EVs effectively counteract chondrocyte senescence and OA progression—offering a scalable, senescence-resistant platform for next-generation EV therapy.</div><div>The Translational Potential of this Article: Producing the large quantities of EVs required for clinical OA therapy necessitates prolonged expansion of stem cells, which inevitably blunts EV efficacy. dECM culture restores the potency of EVs without additional biosafety concerns. Thus, dECM-P15-EVs offer strong translational promise as an advanced, EV-centric OA therapy that overcomes current limitations.</div></div><div><h3>The translational potential of this article</h3><div>Producing the large quantities of EVs required for clinical OA therapy necessitates prolonged expansion of stem cells, which inevitably blunts EV efficacy. dECM culture restores the potency of EVs without additional biosafety concerns. Thus, dECM-P15-EVs offer strong translational promise as an advanced, EV-centric OA therapy that overcomes current lim","PeriodicalId":16636,"journal":{"name":"Journal of Orthopaedic Translation","volume":"56 ","pages":"Article 101019"},"PeriodicalIF":5.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147420118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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