Effects of transplantation of FGF-2-transfected MSCs and XACB on TNF-α expression with avascular necrosis of the femoral head in rabbits

Emerging roles of growth factors in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a potentially disabling orthopedic condition that requires total hip arthroplasty in most late-stage cases. However, mechanisms underlying the development of ONFH remain unknown, and the therapeutic strategies remain limited. Growth factors play a crucial role in different physiological processes, including cell proliferation, invasion, metabolism, apoptosis, and stem cell differentiation. Recent studies have reported that polymorphisms of growth factor-related genes are involved in the pathogenesis of ONFH. Tissue and genetic engineering are attractive strategies for treating early-stage ONFH. In this review, we summarized dysregulated growth factor-related genes and their role in the occurrence and development of ONFH. In addition, we discussed their potential clinical applications in tissue and genetic engineering for the treatment of ONFH.

Tissue Engineering Strategies for Treating Avascular Necrosis of the Femoral Head

Avascular necrosis (AVN) of the femoral head commonly leads to symptomatic osteoarthritis of the hip. In older patients, hip replacement is a viable option that restores the hip biomechanics and improves pain but in pediatric, adolescent, and young adult patients hip replacements impose significant activity limitations and the need for multiple revision surgeries with increasing risk of complication. Early detection of AVN requires a high level of suspicion as diagnostic techniques such as X-rays are not sensitive in the early stages of the disease. There are multiple etiologies that can lead to this disease. In the pediatric and adolescent population, trauma is a commonly recognized cause of AVN. The understanding of the pathophysiology of the disease is limited, adding to the challenge of devising a clinically effective treatment strategy. Surgical techniques to prevent progression of the disease and avoid total hip replacement include core decompression, vascular grafts, and use of bone-marrow derived stem cells with or without adjuncts, such as bisphosphonates and bone morphogenetic protein (BMP), all of which are partially effective only in the very early stages of the disease. Further, these strategies often only improve pain and range of motion in the short-term in some patients and do not predictably prevent progression of the disease. Tissue engineering strategies with the combined use of biomaterials, stem cells and growth factors offer a potential strategy to avoid metallic implants and surgery. Structural, bioactive biomaterial platforms could help in stabilizing the femoral head while inducing osteogenic differentiation to regenerate bone and provide angiogenic cues to concomitantly recover vasculature in the femoral head. Moreover, injectable systems that can be delivered using a minimal invasive procedure and provide mechanical support the collapsing femoral head could potentially alleviate the need for surgical interventions in the future. The present review describes the limitations of existing surgical methods and the recent advances in tissue engineering that are leading in the direction of a clinically effective, translational solution for AVN in future.

Stem cell therapy for osteonecrosis of femoral head: Opportunities and challenges

Osteonecrosis of the femoral head (ONFH) is a progressive disease with a complex etiology and unclear pathogenesis, resulting in severe hip pain and dysfunction mainly observed in young patients. Although total hip arthroplasty (THA) is the most effective treatment for patients with ONFH in the terminal stage, the results of THA in young patients or active populations are often not favorable, with some complications related to the prosthesis. With the development of biotechnology, an increasing number of studies pay attention to use of stem cells for the treatment of ONFH. Stem cells are characterized by the ability to self-renew and differentiate into multiple cell types, including differentiation into osteoblasts and endothelial cells to mediate bone repair and angiogenesis. Furthermore, stem cells can offer growth factors to promote blood supply in the necrotic regions by paracrine effects. Therefore, stem cell therapy has become one of the hip-preserving alternatives for ONFH. This review summarized the current trends in stem cell therapy for ONFH, from clinical applications to related basic research, and showed that an increasing number of studies have confirmed the effectiveness of stem cell therapy in ONFH. However, many unsolved problems and challenges in practical applications of stem cell therapy still exist, such as patient selection, standardized procedures, safety assessment, and the fate of transplanted cells in the body. Additional studies are required to find ideal cell sources, appropriate transplantation methods, and the optimal number of cells for transplantation.

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Diversities in repair processes present a challenge in the targeted treatment of ONFH.

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Osteogenesis and angiogenesis are the primary mechanisms of MSCs treatment in ONFH.

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Systematic safety assessment and cell tracing are necessary for stem cell therapy.

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Optimal numbers and methods of cell transplantation need to be further confirmed.

Mesenchymal stem cells-derived and siRNAs-encapsulated exosomes inhibit osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a progressive, obstinate and disabling disease. At present, the treatment of ONFH is still a global medical problem. We aim to explore the role of bone mesenchymal stem cells (BMSCs)‐derived and siRNAs‐encapsulated exosomes (siRNAs‐encapsulated BMSCexos) in ONFH. We first isolated BMSCexos and screened siRNAs of 6 ONFH‐related genes for siRNAs‐encapsulated BMSCexo. The expression of these 6 ONFH‐related genes in dexamethasone (DXM)‐treated MC3T3‐E1 cell, cell model of ONFH, was detected by RT‐qPCR and Western blot analysis. And then, we performed CCK‐8 assay, angiogenesis assay and HE staining analysis to test the promotion role of the siRNAs‐encapsulated BMSCexo for angiogenesis during ONFH repair. The results suggest that the obtained particles were BMSCexos. The screened effective siRNAs could effectively knock down their expression in VECs. Moreover, siRNAs‐encapsulated BMSCexo could effectively knock down the expression of these genes in VECs. In addition, siRNAs‐encapsulated BMSCexo promote angiogenesis during ONFH repair. In conclusion, we found siRNAs‐encapsulated BMSCexos could promote ONFH repair by angiogenesis, and indicated exosome as the new siRNA carrier is of great significance to improve the efficiency of RNAi.

Therapeutic Applications of Genes and Gene-Engineered Mesenchymal Stem Cells for Femoral Head Necrosis

Osteonecrosis of the femoral head (ONFH) is a common and disabling joint disease. Although there is no clear consensus on the complex pathogenic mechanism of ONFH, trauma, abuse of glucocorticoids, and alcoholism are implicated in its etiology. The therapeutic strategies are still limited, and the clinical outcomes are not satisfactory. Mesenchymal stem cells (MSCs) have been shown to exert a positive impact on ONFH in preclinical experiments and clinical trials. The beneficial properties of MSCs are due, at least in part, to their ability to home to the injured tissue, secretion of paracrine signaling molecules, and multipotentiality. Nevertheless, the regenerative capacity of transplanted cells is impaired by the hostile environment of necrotic tissue in vivo, limiting their clinical efficacy. Recently, genetic engineering has been introduced as an attractive strategy to improve the regenerative properties of MSCs in the treatment of early-stage ONFH. This review summarizes the function of several genes used in the engineering of MSCs for the treatment of ONFH. Further, current challenges and future perspectives of genetic manipulation of MSCs are discussed. The notion of genetically engineered MSCs functioning as a "factory" that can produce a significant amount of multipotent and patient-specific therapeutic product is emphasized.