Identification of mitophagy-related biomarkers in osteoarthritis.

BACKGROUND: Osteoarthritis (OA) is a common joint disease, and existing drugs cannot cure OA, so there is an urgent need to identify new targets. Mitophagy plays an important role in OA; however, the role of mitophagy in the OA immune system is not yet clear. METHODS: In this study, differential analysis and enrichment analysis were used to identify mitophagy-related genes (MRGs) with differential expression in OA and the functional pathways involved in OA. Subsequently, two machine learning methods, RF and LASSO, were used to screen MRGs with diagnostic value and construct nomograms. At the same time, the relationship between mitophagy and OA immune response was explored by immunoinfiltration analysis. RESULTS: Forty-three differentially MRGs were identified in OA, of which six MRGs (GABARAPL2, PARL, GABARAPL1, JUN, RRAS, and SNX7) were associated with the diagnosis of OA. The ROC analysis results show that these 6 MRGs have high predictive accuracy in the diagnosis of OA. In immune infiltration analysis, we found that the abundance of significantly different immune cells in OA was mostly upregulated. In addition, the expression of diagnostic-related MRGs is correlated with changes in the abundance of immune cells in OA. CONCLUSION: This study demonstrates that six MRGs can be used as diagnostic biomarkers. The expression of diagnostic-related MRGs is correlated with changes in the abundance of immune cells in OA. At the same time, mitophagy may affect the immune microenvironment of OA by regulating immune cells, ultimately leading to the progression of OA.

[Study on effectiveness of treating femoral neck fractures based on theory of "positive support"].

Objective: To explore effectiveness of positive support reduction and internal fixation in the treatment of femoral neck fractures. Methods: A clinical data of 74 patients with femoral neck fractures treated with hollow screw internal fixation between September 2017 and September 2021 was retrospectively analyzed. Based on the quality of fracture reduction, they were divided into positive support reduction group (group A, n=25), negative support reduction group (group B, n=21), and anatomical reduction group (group C, n=28). There was no significant difference in baseline data such as gender, age, cause of injury, disease duration, fracture side, Garden classification, and fracture line position classification between groups (P>0.05). The occurrence of complications such as early fixation failure, femoral neck shortening, non-union of fractures, and femoral head necrosis in three groups, as well as the Harris score of the hip joint were recorded and compared. Results: All patients had primary healing of incisions after operation and were followed up more than 12 months. The follow-up time for groups A, B, and C was (21.1±5.7), (22.6±4.3), and (21.9±4.1) months, respectively; there was no significant difference between groups (P>0.05). There was no significant difference in the incidences of non-union of fractures, early internal fixation failure, and the femoral head necrosis between groups (P>0.05). The incidence and length of femoral neck shortening, and the hip Harris score at last follow-up in groups A and C were all superior to those in the group B, with significant difference (P<0.05). There was no significant difference in the above indicators between groups A and C (P>0.05). Conclusion: Positive support reduction can provide a good biomechanical environment for the healing of femoral neck fractures, thereby achieving a higher fracture healing rate, reducing the occurrence of femoral neck shortening, minimizing the function of hip joint, and achieving effectiveness similar to anatomical reduction.

Osteochondral repair using scaffolds with gradient pore sizes constructed with silk fibroin, chitosan, and nano-hydroxyapatite.

BACKGROUND: One of the main problems associated with the development of osteochondral reparative materials is that the accurate imitation of the structure of the natural osteochondral tissue and fabrication of a suitable scaffold material for osteochondral repair are difficult. The long-term outcomes of single- or bilayered scaffolds are often unsatisfactory because of the absence of a progressive osteochondral structure. Therefore, only scaffolds with gradient pore sizes are suitable for osteochondral repair to achieve better proliferation and differentiation of the stem cells into osteochondral tissues to complete the repair of defects. METHODS: A silk fibroin (SF) solution, chitosan (CS) solution, and nano-hydroxyapatite (nHA) suspension were mixed at the same weight fraction to obtain osteochondral scaffolds with gradient pore diameters by centrifugation, freeze-drying, and chemical cross-linking. RESULTS: The scaffolds prepared in this study are confirmed to have a progressive structure starting from the cartilage layer to bone layer, similar to that of the normal osteochondral tissues. The prepared scaffolds are cylindrical in shape and have high internal porosity. The structure consists of regular and highly interconnected pores with a progressively increasing pore distribution as well as a progressively changing pore diameter. The scaffold strongly absorbs water, and has a suitable degradation rate, sufficient space for cell growth and proliferation, and good resistance to compression. Thus, the scaffold can provide sufficient nutrients and space for cell growth, proliferation, and migration. Further, bone marrow mesenchymal stem cells seeded onto the scaffold closely attach to the scaffold and stably grow and proliferate, indicating that the scaffold has good biocompatibility with no cytotoxicity. CONCLUSION: In brief, the physical properties and biocompatibility of our scaffolds fully comply with the requirements of scaffold materials required for osteochondral tissue engineering, and they are expected to become a new type of scaffolds with gradient pore sizes for osteochondral repair.

Evaluation of the effects of the combination of BMP-2-modified BMSCs and PRP on cartilage defects.

Articular cartilage is avascular and aneural, and has limited capacity for self-regeneration when injured. Tissue engineering has emerged as a promising approach in repairing cartilage defects. To improve the therapy of cartilage healing, the present study investigated the efficacy of the combination of lentivirus-mediated bone morphogenetic protein-2 (BMP2) in bone marrow-derived stromal cells (BMSCs) and platelet-rich plasma (PRP) on cartilage and bone healing in a cartilage defect model using the rabbit knee. The BMSCs were harvested from New Zealand rabbits and transduced with lentivirus carrying BMP-2. Standard bone defects were introduced in the femoral groove of patellofemoral joints of 48 New Zealand rabbits. The cartilage defects were subjected to synthetic scaffold mosaicplasty with chitosan/silk fibroin/nanohydroxyapatite particles tri-component scaffolds soaked in BMSCs and PRP. After 16 weeks, the tissue specimens were assessed by micro-computed tomography (micro-CT) and macroscopic examination. The results showed that lentivirus-mediated BMP-2 and PRP increased the cell viability of the BMSCs, induced the expression of associated genes and enhanced osteogenic differentiation in vitro. In vivo, the expression of BMP-2 was observed for 16 weeks. The combination of BMP-2 and PRP treatment led to optimal results, compared with the other groups on micro-CT and gross observations. The results of the present study present a novel therapy using the lentivirus-mediated BMP-2 gene together with PRP for cartilage healing.

Composite scaffolds loaded with bone mesenchymal stem cells promote the repair of radial bone defects in rabbit model.

This study aimed to investigate the efficacy of three-dimensional scaffolds of silk fibroin/chitosan/nano-hydroxyapatite (SF/CS/nHA) and bone marrow derived mesenchymal stem cells (BMSCs) on the repair of long segmental bone defects in rabbits. BMSCs were cultured with SF/CS/nHA in vitro, and cell proliferation, alkaline phosphatase activity and Ca2+ content were examined. A 15mm segmental defect in the radius was generated in 12 New Zealand White rabbits, which were divided randomly into three groups (n=4): experimental group with SF/CS/nHA scaffold of induced BMSCs; control group with SF/CS/nHA scaffold; and blank group without any materials. Postoperatively at 12 weeks, osteogenesis effect and the degradation and absorption of SF/CS/nHA were evaluated by X-ray, hematoxylin eosin staining, and scanning electron microscopy. In vitro, SF/CS/nHA scaffolds exhibited good biocompatibility and no toxicity. SF/CS/nHA promoted adhesion, growth, and calcium nodule formation of BMSCs compared to control (P<0.05). In vivo, we observed gradual new bone formation and bone defect gradually recovered at 12 weeks in experimental and control group, but more new bone was formed in experimental group (P<0.05). In blank group, limited bone formation was observed and bone defect was obvious. In conclusion, SF/CS/nHA scaffolds loaded with BMSCs achieve high efficacy to repair segmental defect in the radius.

Preparation of a biphase composite scaffold and its application in tissue engineering for femoral osteochondral defects in rabbits.

PURPOSE: Three-dimensional bioactive scaffolds are useful tools for stem cell implant in tissue-engineering. For chondral and subchondral repair, the chondroinductive and osteoinductive property of a scaffold is a major challenge. The scaffolds that aim to osteogenic differentiation have been well studied. However, cartilage cells can hardly be induced for osteogenesis, and monophase scaffolds cannot ideally repair both cartilage and subchondral defects at the same time. METHODS: We developed a novel biphase composite scaffold and observe its application osteochondral defects. We combined the advantages of silk-fibroin/chitosan (SF/CS) scaffold in chondrogenic differentiation and the silk-fibroin/chitosan/nano-hydroxyapatite (SF/CS/nHA) scaffold in osteogenic differentiation and bone regeneration, and synthesized a SF/CS-SF/CS/nHA scaffold, which contained both the chondrocytic phase (SF/CS) and the osteoblastic phase (SF/CS/nHA). RESULTS: The biphase scaffold exhibited a porosity ratio around 90% and a water absorption ratio about 822%. A similar degradation property to traditional monophase scaffolds was observed. Bone mesenchymal stem cells (BMSCs) showed a good proliferation on this scaffold. Expression of two types of collagen was inducable for BMSCs on the scaffold. Neoformative extracellular matrix integrated with the scaffold was observed by the scanning electron microscope. When implanted in the lesion site in the rabbit femur with cartilage injury, mixing and filling function were exerted by the cell-scaffold constructs (CSCs). Micro-CT scanning revealed both chondral and subchondral layers were repaired. Moreover, type I and II collagens were both expressed in the implanted CSCs. CONCLUSIONS: Chondral and subchondral repair can be achieved using the biphase scaffold implant that permits both chondrogenesis and osteogenesis from BMSCs. This approach has the potential to be clinically used for tissue engineering implantation.