Tissue Engineering Part A最新文献

The lymphatic system maintains tissue fluid homeostasis and it is involved in the transport of nutrients and immunosurveillance. It also plays a pivotal role in both pathological and regenerative processes. Lymphatic development in the embryo occurs by polarization and proliferation of lymphatic endothelial cells from the lymph sacs, that is, lymphangiogenesis. Alternatively, lymphvasculogenesis further contributes to the formation of lymphatic vessels. In adult tissues, lymphatic formation rarely occurs under physiological conditions, being restricted to pathological processes. In lymphvasculogenesis, progenitor cells seem to be a source of lymphatic vessels. Indeed, mesenchymal stem cells, adipose stem cells, endothelial progenitor cells, and colony-forming endothelial cells are able to promote lymphatic regeneration by different mechanisms, such as direct differentiation and paracrine effects. In this review, we summarize what is known on the diverse stem/progenitor cell niches available for the lymphatic system, emphasizing the potential that these cells hold for lymphatic tissue engineering through 3D bioprinting and their translation to clinical application.

Conventionally, for cartilage tissue engineering applications, transforming growth factor beta (TGF-β) is administered at doses that are several orders of magnitude higher than those present during native cartilage development. While these doses accelerate extracellular matrix (ECM) biosynthesis, they may also contribute to features detrimental to hyaline cartilage function, including tissue swelling, type I collagen (COL-I) deposition, cellular hypertrophy, and cellular hyperplasia. In contrast, during native cartilage development, chondrocytes are exposed to moderate TGF-β levels, which serve to promote strong biosynthetic enhancements while mitigating risks of pathology associated with TGF-β excesses. Here, we examine the hypothesis that physiologic doses of TGF-β can yield neocartilage with a more hyaline cartilage-like composition and structure relative to conventionally administered supraphysiologic doses. This hypothesis was examined on a model system of reduced-size constructs (∅2 × 2 mm or ∅3 × 2 mm) comprised of bovine chondrocytes encapsulated in agarose, which exhibit mitigated TGF-β spatial gradients allowing for an evaluation of the intrinsic effect of TGF-β doses on tissue development. Reduced-size (∅2 × 2 mm or ∅3 × 2 mm) and conventional-size constructs (∅4-∅6 mm × 2 mm) were subjected to a range of physiologic (0.1, 0.3, 1 ng/mL) and supraphysiologic (3, 10 ng/mL) TGF-β doses. At day 56, the physiologic 0.3 ng/mL dose yielded reduced-size constructs with native cartilage-matched Young's modulus (E_Y) (630 ± 58 kPa) and sulfated glycosaminoglycan (sGAG) content (5.9 ± 0.6%) while significantly increasing the sGAG-to-collagen ratio, leading to significantly reduced tissue swelling relative to constructs exposed to the supraphysiologic 10 ng/mL TGF-β dose. Furthermore, reduced-size constructs exposed to the 0.3 ng/mL dose exhibited a significant reduction in fibrocartilage-associated COL-I and a 77% reduction in the fraction of chondrocytes present in a clustered morphology, relative to the supraphysiologic 10 ng/mL dose (p < 0.001). E_Y was significantly lower for conventional-size constructs exposed to physiologic doses due to TGF-β transport limitations in these larger tissues (p < 0.001). Overall, physiologic TGF-β appears to achieve an important balance of promoting requisite ECM biosynthesis, while mitigating features detrimental to hyaline cartilage function. While reduced-size constructs are not suitable for the repair of clinical-size cartilage lesions, insights from this work can inform TGF-β dosing requirements for emerging scaffold release or nutrient channel delivery platforms capable of achieving uniform delivery of physiologic TGF-β doses to larger constructs required for clinical cartilage repair.

Osteoarthritis is a debilitating chronic joint disorder that affects millions of people worldwide. Since palliative and surgical treatments cannot completely regenerate hyaline cartilage within the articulating joint, osteochondral (OC) tissue engineering has been explored to heal OC defects. Utilizing computational simulations and three-dimensional (3D) printing, we aimed to build rationale around fabricating OC scaffolds with enhanced biomechanics. First, computational simulations revealed that interfacial fibrils within a bilayer alter OC scaffold deformation patterns by redirecting load-induced stresses toward the top of the cartilage layer. Principal component analysis revealed that scaffolds with 800 μm long fibrils (scaffolds 8A-8H) possessed optimal biomechanical properties to withstand compression and shear forces. While compression testing indicated that OC scaffolds with 800 μm fibrils did not have greater compressive moduli than other scaffolds, interfacial shear tests indicated that scaffold 8H possessed the greatest shear strength. Lastly, failure analysis demonstrated that yielding or buckling models describe interfacial fibril failure depending on fibril slenderness S. Specifically for scaffolds with packing density n = 6 and n = 8, the yielding failure model fits experimental loads with S < 10, while the buckling model fitted scaffolds with S < 10 slenderness. The research presented provides critical insights into designing 3D printed interfacial scaffolds with refined biomechanics toward improving OC tissue engineering outcomes.

Impact statement Contactless manipulation and cell patterning techniques provide rapid and cost-effective three-dimensional (3D) cell culture model formation for tissue engineering applications. The present study introduces a new methodology that comprised alginate-based bioink to pattern cells via contactless magnetic manipulation to fabricate 3D cardiac structures. The developed cardiac model was evaluated in terms of Doxorubicin-induced cardiotoxicity and biopatterned 3D cardiac structures were found more resistant to drug exposure compared to two-dimensional control.

This perspective, marking the 30th anniversary of the Tissue Engineering journal, discusses the exciting trends in the global commercialization of tissue engineering technology. Within a historical context, we present an evolution of challenges and a discussion of the last 5 years of global commercial successes and emerging market trends, highlighting the continued expansion of the field in the northeastern United States. This leads to an overview of the last 5 years' progress in clinical trials for tissue-engineered therapeutics, including an analysis of trends in success and failure. Finally, we provide a broad overview of preclinical research and a perspective on where the state-of-the-art lies on the horizon.

Tissues on a chip are sophisticated three-dimensional (3D) in vitro microphysiological systems designed to replicate human tissue conditions within dynamic physicochemical environments. However, the current fabrication methods for tissue spheroids on a chip require multiple parts and manual processing steps, including the deposition of spheroids onto prefabricated "chips." These challenges also lead to limitations regarding scalability and reproducibility. To overcome these challenges, we employed 3D printing techniques to automate the fabrication process of tissue spheroids on a chip. This allowed the simultaneous high-throughput printing of human liver spheroids and their surrounding polymeric flow chamber "chips" containing inner channels in a single step. The fabricated liver tissue spheroids on a liver-on-a-chip (LOC) were subsequently subjected to dynamic culturing by a peristaltic pump, enabling assessment of cell viability and metabolic activities. The 3D printed liver spheroids within the printed chips demonstrated high cell viability (>80%), increased spheroid size, and consistent adenosine triphosphate (ATP) activity and albumin production for up to 14 days. Furthermore, we conducted a study on the effects of acetaminophen (APAP), a nonsteroidal anti-inflammatory drug, on the LOC. Comparative analysis revealed a substantial decline in cell viability (<40%), diminished ATP activity, and reduced spheroid size after 7 days of culture within the APAP-treated LOC group, compared to the nontreated groups. These results underscore the potential of 3D bioprinted tissue chips as an advanced in vitro model that holds promise for accurately studying in vivo biological processes, including the assessment of tissue response to administered drugs, in a high-throughput manner.

Investigating the infection mechanism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the airway epithelium and developing effective defense strategies against infection are important. To achieve this, establishing appropriate infection models is crucial. Therefore, various in vitro models, such as cell lines and primary cultures, and in vivo models involving animals that exhibit SARS-CoV-2 infection and genetically humanized animals have been used as animal models. However, no animal model has been established that allows infection experiments with human cells under the physiological environment of airway epithelia. Therefore, we aimed to establish a novel animal model that enables infection experiments using human cells. Human induced pluripotent stem cell-derived airway epithelial cell-transplanted nude rats (hiPSC-AEC rats) were used, and infection studies were performed by spraying lentiviral pseudoviruses containing SARS-CoV-2 spike protein and the GFP gene on the tracheae. After infection, immunohistochemical analyses revealed the existence of GFP-positive-infected transplanted cells in the epithelial and submucosal layers. In this study, a SARS-CoV-2 infection animal model including human cells was established mimicking infection through respiration, and we demonstrated that the hiPSC-AEC rat could be used as an animal model for basic research and the development of therapeutic methods for human-specific respiratory infectious diseases.

Therapy with mesenchymal stem cells (MSCs) is considered an attractive strategy for the repair or regeneration of damaged tissues. However, low survival of MSCs limits their applications clinically. Oxidized low-density lipoprotein (ox-LDL) is significantly increased in patients with hyperlipidemia and decreases the survival of MSCs. Bcl-2 is critically involved in important cell functions, including cell membrane integrity and cell survival. The present study was designed to test the hypothesis that ox-LDL attenuates the survival of MSCs through suppression of Bcl-2 expression. Bone marrow MSCs from C57BL/6 mice were cultured with ox-LDL at different concentrations (0-140 μg/mL) for 24 h with native LDL as control. Ox-LDL treatment substantially decreased the survival of MSCs dose-dependently and enhanced the release of intracellular lactate dehydrogenase (LDH) in association with a significant decrease in Bcl-2 protein level without change in BAX protein expression in MSCs. Bcl-2 overexpression effectively protected MSCs against ox-LDL-induced damages with preserved cell numbers without significant increase in LDH release. Treatment with N-acetylcysteine (NAC) (1 mM) effectively preserved Bcl-2 protein expression in MSCs and significantly attenuated ox-LDL-induced decrease of cell number and increase in the release of intracellular LDH. These data indicated that ox-LDL treatment resulted in a significant damage of cell membrane and dramatically decreased the survival of MSCs dose-dependently through inhibition of Bcl-2 expression. NAC treatment significantly protected MSCs against the damage of cell membrane by ox-LDL and promoted the survival of MSCs in association with preserved Bcl-2 expression.

Volumetric muscle loss (VML) injuries are defined by loss of sufficient skeletal muscle to produce persistent deficits in muscle form and function, with devastating lifelong consequences to both soldiers and civilians. There are currently no satisfactory treatments for VML injuries. The work described herein details the implementation of a fully enclosed bioreactor environment (FEBE) system that efficiently interfaces with our existing automated bioprinting and advanced biomanufacturing methods for cell deposition on sheet-based scaffolds for our previously described tissue-engineered muscle repair (TEMR) technology platform. Briefly, the TEMR technology consists of a porcine bladder acellular matrix seeded with skeletal muscle progenitor cells and preconditioned via 10% uniaxial cyclic stretch in a bioreactor. Overall, TEMR implantation in an established rat tibialis anterior (TA) VML injury model can result in 60 to ∼90% functional recovery. However, our original study documented >50% failure rate. That is, more than half of the implanted TEMR constructs produced no functional improvement beyond no treatment/repair. The high failure rate was attributed to the untoward mechanical disruption of TEMR during surgical implantation. In a follow-up study, adjustments were made to the geometry of both the VML injury and the TEMR construct, and the "nonresponder" group was reduced from over half the TEMR-treated animals to just 33%. Nonetheless, additional improvement is needed for clinical applicability. The main objectives of the current study were twofold: (1) explore the use of advanced biomanufacturing methods (i.e., FEBE bioreactor) to further improve TEMR reliability (i.e., increase functional response rate), (2) determine if previously established bioprinting methods, when coupled to the customized FEBE system would further improve the rate, magnitude or amplitude of functional outcomes following TEMR implantation in the same rat TA VML injury model. The current study demonstrates the unequivocal benefits of a customized bioreactor system that reduces manipulation of TEMR during cell seeding and maturation via bioprinting while simultaneously maximizing TEMR stability throughout the biofabrication process. This new biomanufacturing strategy not only accelerated the rate of functional recovery, but also eliminated all TEMR failures. In addition, implementation of bioprinting resulted in more physiomimetic skeletal muscle characteristics of repaired muscle tissue.

Xenotransplantation of acellular adipose matrix (AAM) has come to prominence as an intriguing option for soft tissue reconstruction. However, the presence of immunogenic antigens within AAM can trigger unfavorable immune reactions, leading to inadequate in vivo regeneration outcomes. Therefore, the development of advanced technology capable of modulating immune responses is crucial for the therapeutic implementation of AAM xenografts. In this work, an innovative technique is created to bypass the immune system by covering the surface of both AAM and Arg-Gly-Asp (RGD) peptide-modified AAM xenografts with autologous red blood cell (RBC) membrane. The RBC membrane coating remained persistent and exhibited no significant decline even after 21 days. Moreover, it effectively reduced the expression of antigen major histocompatibility complex class 1 (MHC1) on the AAM surface. Following xenogeneic transplantation, the RBC-coated xenografts demonstrated increased expression of the adipogenic factor PPAR-γ, Adipoq, Fabp4, Fasn, and Plin1 and higher numbers of adipocytes. In addition, they exhibited decreased expression of immunological factors, including IL-6, IL-2, IFN-γ, and TNF-α, and fewer inflammatory cells. These findings indicate that RBC membrane coating successfully suppressed immune responses and promoted increased adipogenesis in AAM xenografts. Therefore, AAM camouflage coating with RBC has a lot of potential as a biomaterial for soft tissue reconstruction in clinical settings.