Bone & Joint Research最新文献

Aims: To investigate the role of CXCR4 in response to teriparatide (TPTD) treatment in osteoblasts and osteoclasts.

Methods: Primary murine and human osteoblasts and osteoclasts, MC3T3 cell lines, and hMSC-TERT4 cell lines were treated with TPTD and/or AMD3100, a pharmacological inhibitor of CXCR4. Changes in gene expression, osteoblast viability, mobility, mineralization capacity, and alkaline phosphatase activity were investigated. Osteoclastogenesis and cell fusion were also assessed in response to both treatments.

Results: TPTD increased messenger RNA levels of CXCR4 in all stages of both murine and human osteoblast differentiation. Mineralization analysis showed that CXCR4 was involved in bone matrix formation in response to TPTD. Alkaline phosphatase activity was also impaired by CXCR4 inhibition at early stages of osteoblast differentiation, while it was promoted at late stages, suggesting that CXCR4 could produce a delay in osteoblast maturation. Moreover, we also found a direct activation of osteoclastogenesis after TPTD treatment in murine and human osteoclasts. This process seems to involve CXCR4 activity, since AMD3100-induced CXCR4 inhibition led to a reduction in both murine and human osteoclastogenesis. This process, however, could not be prevented by TPTD treatment.

Conclusion: Our results suggest that CXCR4 is a responsive gene to TPTD treatment, involved in the regulation of osteoblast and osteoclast generation and function. Further in vivo studies are required to confirm this role, and to determine whether pharmacological strategies targeting CXCR4 could potentially improve the treatment outcome for osteoporotic patients.

Aims: The physiological function of sclerostin remains unknown. Sclerostin is synthesized by osteocytes and operates by inhibiting the Wnt/β-catenin pathway. Similarly, it is well established that low levels of sclerostin lead to enhanced bone formation and reduced calciuria, and that high levels of sclerostin are associated with osteoporosis.

Methods: The impact of high levels of recombinant sclerostin on bone and mineral metabolism parameters was analyzed in this study. In male healthy rats, the effects of three elevated doses of sclerostin over a 14-day period were studied, involving bone histomorphometry, micro-CT (μCT), immunohistochemistry, and analysis of mineral metabolism parameters.

Results: Although there was increased bone formation, high doses of sclerostin led to a higher reduction in trabecular bone volume due to a significant increase in bone resorption through the direct activation of osteoclastogenesis. In vitro, sclerostin promoted the differentiation of bone marrow stem cells into osteoclasts. Bone resorption, as measured by tartrate-resistant acid phosphatase (TRAP) activity, was excessive in trabecular, cortical, and subchondral bone. Similarly, high doses of sclerostin increased the number of hypertrophic chondrocytes, consequently expanding the growth plate area. At the cortical level, positive TRAP staining could be observed, suggestive of osteocytic osteolysis and trabecularization of cortical bone. The increased bone resorption resulted in a substantial rise in the urinary excretion of phosphorus and calcium, accompanied by elevated levels of FGF23 and a significant decrease in parathyroid hormone (PTH).

Conclusion: These findings suggest that elevated levels of sclerostin promote bone resorption through the activation of osteoclasts and the generation of osteocytic osteolysis, resulting in increased calciuria, phosphaturia, and changes in mineral metabolism.

Aims: While MRI serves as a tool for assessing the severity of lumbar disc herniation (LDH), it has been observed that imaging diagnoses do not always align with clinical symptoms in nearly half of patients. The absence of dependable prognostic biomarkers impedes the early and accurate diagnosis of LDH, which is critical for the development of further treatment approaches. Thus, the aim of this study was to elucidate the molecular mechanisms that determine pain and LDH severity.

Methods: We conducted a pilot study with 55 patients, employing transcriptomic and metabolomic analyses on blood samples to identify potential biomarkers. A gene-metabolite interaction approach helped in identifying the pivotal pathway linked to disease severity. Moreover, a machine-learning model was designed to differentiate between patients based on the intensity of pain.

Results: Cholinergic-related glycerophospholipid metabolism emerged as the predominant enriched pathway in the severe symptom group via gene-metabolite interaction network analysis. Among various models, the gradient boosting machines (GBM) model stood out, achieving a commendable area under the curve (AUC) of 0.875 in distinguishing between the severe and mild symptom groups using combined RNA and metabolomics data.

Conclusion: Integrated molecular profiling of blood biomarkers has highlighted a novel determining pathway for LDH severity. This machine-learning approach can serve as a valuable predictive tool when MRI findings are inconclusive. Future research will focus on validating these biomarkers and exploring their potential for personalized medicine approaches.

Osteoporosis a is a metabolic bone disease caused by an imbalance in bone homeostasis, which is regulated by osteoblasts and osteoclasts. Protein palmitoylation modification is a post-translational modification that affects protein function, localization, and targeting by attaching palmitoyl groups to specific amino acid residues of proteins. Recent studies have shown that protein palmitoylation is involved in the regulation of osteoclast overproduction, osteoblast migration, osteogenic differentiation, dysfunctional autophagy, and endocrine hormone membrane receptors in osteoporosis. Exactly to what extent palmitoylation modifications can regulate osteoporosis, and whether palmitoylation inhibition can delay osteoporosis, is a key question that needs to be investigated urgently. In this review, we observed that palmitoylation modifications act mainly through two target cells - osteoblasts and osteoclasts - and that the targets of palmitoylation modifications are focused on plasma membrane proteins or cytosolic proteins of the target cells, which tend to assume the role of receiving extracellular signals. We also noted that different palmitoyl transferases acting on different substrate proteins exert conflicting regulation of osteoblast function. We concluded that the regulation of osteocyte function, bone homeostasis, and osteoporosis by palmitoylation modifications is multidimensional, diverse, and interconnected. Perfecting the palmitoylation modification network can enhance our ability to utilize post-translational modifications to resist osteoporosis and lay the foundation for targeting palmitoyl transferases to treat osteoporosis in the future.

Aims: Cyclooxygenase-2 (COX-2) is an enzyme that synthesizes prostaglandins from arachidonic acid. Previous reports have indicated that COX-2 is constitutively expressed in osteogenic cells instead of being expressed only after pathogenic induction, and that it facilitates osteoblast proliferation via PTEN/Akt/p27^kip1 signalling. However, the role of COX-2 in osteogenic differentiation of murine bone marrow mesenchymal stromal cells (BMSCs) remains controversial. In this study, we investigated the function of COX-2 in the osteogenic differentiation of BMSCs.

Methods: COX-2 inhibitor, COX-2 overexpression vector, and p27^kip1 small interfering RNA (siRNA) were used to evaluate the role of COX-2 in osteogenic differentiation and related signalling pathways in BMSCs.

Results: We found that the messenger RNA (mRNA) and protein levels of COX-2 decreased gradually during osteogenic differentiation. Inhibition of COX-2 activity promoted FOXO3a and p27^kip1 expression and simultaneously enhanced osteogenesis, as indicated by increased osteogenic gene expression and mineralization in BMSCs. Furthermore, when p27^kip1 was silenced, the suppressive effects of COX-2 on osteogenesis were reversed. It demonstrated that the negative regulatory effect of COX-2 on osteogenesis was mediated by p27^kip1. In addition, our results showed that overexpression of COX-2 reduced the mRNA and protein levels of FOXO3a and p27^kip1, and thus attenuated osteogenic gene expression. These results indicate that COX-2 negatively regulates osteogenic differentiation by reducing the expression of osteogenic genes via the FOXO3a/p27^kip1 signalling pathway.

Conclusion: Together with the findings from previous and current studies, these results indicate that COX-2 has a different role in proliferation versus differentiation during osteogenesis via FOXO3a/p27^kip1 signalling in osteoblasts or BMSCs.

Aims: Thresholds for acceptable amounts of migration tibial components measured with radiostereometric analysis (RSA) are limited to specific follow-up moments and do not use the full migration pattern. The Michaelis-Menten (MM) model, a non-linear model from biochemistry, could potentially be used to model the entire migration pattern. The purpose of this study was therefore to determine if MM models can be fitted to RSA migration data of tibial components, and if these fitted model parameters can be used for early detection of tibial components at high risk for aseptic loosening.

Methods: Migration patterns of tibial component maximum total point motion (MTPM) over six months, one year, and two years, as well as revision rates for aseptic loosening from previously published systematic reviews, were used. Fitted MM models gave the estimated maximal MTPM (MTPMemax) and a constant (K), which is the time in months at which half the MTPMemax is reached for tibial component designs. To assess model fit, intraclass correlation coefficients (ICCs) were calculated for the modelled MTPMemax and reported five-year MTPM values. The estimated MTPMemax and K-values were plotted against their corresponding five-year revision rate for aseptic loosening.

Results: For six-month, one-year, and two-year migration patterns, the ICC was 0.81, 0.83, and 0.91, respectively, suggesting excellent agreement between calculated MTPMemax values and the known five-year MTPM values. MTPMemax up to 1.3 mm was considered to be safe based on association with aseptic loosening revision rate, while MTPMemax of more than 1.3 mm was unsafe. The K-value could not be used as a predictor for safe versus unsafe implants.

Conclusion: MTPMemax values may be used for early detection of tibial components at high risk for aseptic loosening, possibly offering improvements over the older threshold system.

Aims: This systematic review aimed to investigate the association between growth differentiation factor 15 (GDF-15) and rheumatoid arthritis (RA) disease activity, explore the differences at the genetic level, and evaluate the value of GDF-15 in diagnosing RA.

Methods: A comprehensive literature search was conducted using PubMed, Web of Science, Cochrane Library, and Embase on 23 August 2023. Methodological quality was independently assessed by using the Agency for Healthcare Research and Quality scale. The primary parameters analyzed were the serum GDF-15 concentration, disease activity, and diagnostic sensitivity and specificity.

Results: A total of 469 documents were retrieved, and five clinical studies were ultimately included. In the included studies, GDF-15 serum levels were found to be notably greater in RA patients than in healthy individuals, and these levels exhibited a positive correlation with disease severity. Furthermore, increased GDF-15 serum levels were associated with specific gene variations in RA patients, but varied according to ethnicity. In two included studies, GDF-15 showed high diagnostic sensitivity and specificity for highly active RA, demonstrating its utility as a diagnostic biomarker of RA.

Conclusion: GDF-15 expression is increased in RA patients and is associated with disease activity; thus, GDF-15 is potentially an effective diagnostic biomarker for RA. However, additional high-quality studies, especially randomized controlled trials and cohort studies with follow-up data, are needed to assess the role of GDF-15 in RA.

Aims: This study aimed to evaluate the effects of Nd:YAG laser treatment on fracture healing in a rat model. We hypothesized that laser therapy would accelerate healing by stimulating early neovascularization and osteoblast recruitment.

Methods: A total of 54 male Sprague-Dawley rats received intramedullary Kirschner wire (K-wire) osteosynthesis following femoral osteotomy, and were randomly divided into two groups (n = 27 each): the control group, and the laser group that received daily pulsed Nd:YAG laser for ten days immediately after osteotomy. Fracture sites were assessed using micro-CT (μCT; n = 8 at each timepoint), histology (n = 4), and three-point bending tests (n = 4) at week 2, week 4, and week 6, respectively. At week 2, an additional three rats per group were selected for the western blot tests.

Results: Compared to controls, the laser group showed higher vascular endothelial growth factor (VEGF), CD31, and Runx2 protein expression, and significantly higher neovascular area density and osteoblast density (p = 0.025 and p = 0.008, respectively) at week 2. At week 4, the laser treatment led to higher histological fracture healing scale and flexural modulus, and less strain (p = 0.001, p = 0.020, and p = 0.004, respectively). Macroscopically, the laser group showed higher mature bone volume fraction and radiological union score at weeks 4 and 6 (volume fraction: p = 0.017 and p = 0.001; union score: p = 0.001 and p = 0.024, respectively).

Conclusion: Pulsed Nd:YAG laser therapy accelerates multiple quantitative indicators of fracture healing within six weeks in a rat femoral osteotomy model, which was associated with enhanced angiogenesis and osteogenesis during the early healing phase.

Aims: Spontaneous neck fractures are feared complications of cephalomedullary nail removal after successful healing of per- and subtrochanteric fractures. To date, the initial postoperative stability as well as the correct weightbearing regimen remain unclear. The aim of this biomechanical ex vivo study was to evaluate the initial postoperative failure load after hardware removal of specimens, which received cephalomedullary nails during their lifetime.

Methods: A total of 20 specimens of voluntary body donors were included in this study. Group 1 (n = 10) consisted of specimens that received cephalomedullary nails during their lifetime due to per- or subtrochanteric fractures. Each individual was matched for age, sex, femur size, and neck-shaft angle (Group 2 = control, n = 10). Biomechanical testing was performed in a single-leg stance setting, and volumetric bone mineral density (vBMD) was measured proximally at the femoral neck and distally at the epicondyles.

Results: Groups 1 and 2 differed significantly in terms of failure loads (p = 0.002), fracture types, and ratios of proximal and distal vBMD (p = 0.035). Femora after nail removal were significantly weaker (1,835.0 N vs 4,523.0 N) and showed lower ratios of proximal to distal vBMD (0.74 vs 1.18), which indicated altered stress distributions at the femoral neck in presence of femoral neck screws. They were further characterized by predominantly subcapital buckle-type fractures, while the control Group 2 showed predominantly transcervical fractures.

Conclusion: Altered stress distribution in presence of femoral neck screws leads to changes in biomechanical properties of the proximal femur, resulting in potentially unstable situations after nail removal in clinical settings. Elective removal of cephalomedullary nails should be undertaken with caution in view of the potentially increased fracture risk.