Experimental Study Of Umbilical Cord Mesenchymal Stem Cells In Treatment Of Steroid-induced Femoral Head Necrosis

Background: Due to the extensive application of glucocorticoids in many rheumatic immune diseases,Fukushima et al showed that steroid-induced necrosis of the femoral head had become the first non-traumatic necrosis of the femoral head.Umbilical cord mesenchymal stem cells are derived from umbilical cord and possess high purity,high proliferative activity,excellent ability of multidirectional differentiation and cytokine secretion.Because of its unique ability,it shows great clinical application prospect in the treatment of femur head necrosis.According to the existing data in the clinical application of stem cells in patients with early femoral head necrosis has obtained the good safety and clinical response,the main clinical observation indexes including hip score and the improvement of imaging,reduced patients’ pain and necrotic area as well as the hip function improved,significantly improve the life quality of patients.At present,the research of umbilical cord mesenchymal stem cells on femoral head necrosis is still in the preliminary stage of exploration,and there is a lack of systematic and standardized basic research.In this study,a complete umbilical cord mesenchymal stem cell preparation and quality control system were established,and a rat model of femoral head necrosis was further established to analyze the occurrence of femoral head necrosis and the possible mechanism of stem cell therapy from the perspectives of cellular immunity and inflammatory mediators.Apoptosis is a prominent determinant of the steroid-induced avascular necrosis of the femoral head(SANFH).Human umbilical cord mesenchymal stem cells(hUC-MSCs)have been shown to be involved in apoptosis in disease models.However,the mechanism of hUC-MSCs regulating apoptosis in SANFH remains to be further studied.Objective: To explore the possible mechanism of umbilical cord mesenchymal stem cells in the treatment of steroid induced femoral head necrosis by injecting umbilical cord mesenchymal stem cells into the tail vein of rat steroid induced femoral head necrosis model.Methods: Part Ⅰ: Umbilical cord mesenchymal stem cells were extracted and their phenotypes were identified.Part Ⅱ: The rat model of steroid-induced femur head necrosis constructed by lipopolysaccharide combined with dexamethasone was identified by HE staining of pathological sections.Part Ⅲ: The established model of steroid-induced femur head necrosis was treated by injecting umbilical cord mesenchymal stem cells.The levels of serum inflammatory factors,the polarization direction of macrophages in femoral head samples were detected by immunofluorescence and the expression levels of polarization-related proteins in macrophages were detected by Western blot.Results: Part Ⅰ: umbilical cord mesenchymal stem cells extracted from umbilical cord met the international stem cell standards and experimental application standards.The second part: HE staining of pathological sections of rats in the modeling group showed necrosis of femoral head chondrocytes,disappearance of columnar arrangement,collapse of subchondral bone trabecular bone,and increase of empty bone lacunae,indicating that the rat model of steroid-induced necrosis of femoral head was successfully established.Part Ⅲ: Treatment with hUC-MSCs can reduce femoral head necrosis and osteocyte apoptosis,reduce macrophage polarization,and decrease the levels of TNF-α,IL-1 β and IL-6 in peripheral blood,as well as the expression of p-AKT and p-mTOR in vivo.Conclusions:HUC-MSCs ameliorate necrosis and osteocyte apoptosis in hormone-induced ONFH model by reducing macrophage polarization,which is related to the AKT/mTOR signaling pathway.