Study On The Mechanism Of FGF18 Promoting Bone Healing Of Rotator Cuff Tendon By Inhibiting BMSCs Aging In Osteoporosis

Research background:With the accelerating aging process of the population,the incidence of rotator cuff injury has been increasing year by year.Patients with rotator cuff injury accompanied by osteoporosis have poor postoperative prognosis,which has become a challenge for the development of sports medicine.The arrangement of the tendon bone interface in osteoporotic mice is disordered,and there are a large number of aging cells;This project aims to investigate the relationship between osteoporosis and rotator cuff tendon bone healing by constructing a mouse osteoporosis model and a rotator cuff injury repair model;Provide new ideas for promoting the healing of the rotator cuff tendon bone.Research Objective:Exploring the effect of FGF18 on the healing of rotator cuff tendon bone in osteoporotic mice through cell and animal experiments.Research Method:(1)In vitro experiments:β-The aging indexes of BMSCs were detected by galactosidase staining;Aging induction and overexpression of FGF18 were performed on mouse bone marrow mesenchymal stem cells.The expression levels of osteogenic,chondrogenic,tendinous differentiation,and aging related genes were detected by real-time fluorescence quantitative PCR and Western blotting.The effect of osteogenic differentiation medium on the osteogenic ability of aging BMSCs was detected by ALP staining,and the effect of FGF18 on the aging,osteogenic,chondrogenic,and tendinous differentiation ability of aging BMSCs was preliminarily judged;Aging BMSCs were treated with mTOR pathway inhibitors rapamycin and FGF18,and p-mTOR and p-S6 proteins were detected by Western blot.(2)In vivo experiment:90 C57BL/6 mice were randomly divided into blank control group,OVX group(ovariectomy group),and OVX+FGF18 group.OVX+FGF18 group injected fibrin gel mixed with FGF18 recombinant protein at supraspinatus muscle insertion,and at the 2nd and 4th weeks after rotator cuff repair,combined with histological results,immunofluorescence staining Comprehensive evaluation of the effect of FGF18 on tendon bone healing after repair of rotator cuff injury in osteoporotic mice using immunohistochemical staining,micro CT,and biomechanical testing.Research Results:FGF18 can promote the expression of Runx2,OCN,COL Ⅱ,SOX9,TNMD,and SCX genes in BMSCs,and it was found that FGF18 can inhibit the expression of p16,p21,and Rb aging related genes induced by hydrogen peroxide in BMSCs.ALP staining showed that FGF18 can promote osteogenic differentiation in aging BMSCs.By immunofluorescence staining,q-PCR,and Western blot,it was confirmed that FGF18 inhibits-the mTOR/S6 signaling pathway and affects cell aging.Two weeks after surgery,it was found that compared with the OVX group,the OVX+FGF18 group had more chondrocyte generation at the tendon bone healing interface,better healing effect,higher histological score,and higher expression levels of Runx2 and SOX9 at the tendon bone healing interface.Micro-CT analysis found that the OVX+FGF18 group had better BV/TV(bone volume/total volume fraction)around the supraspinatus muscle insertion area.The OVX+FGF18 group had a higher maximum destructive load in the second week after surgery compared to the OVX group.Research Conclusion:FGF18 promotes the differentiation of aging BMSCs into three lineages and can reverse the aging of BMSCs.FGF18 inhibits cell aging by inhibiting the mTOR/S6 signaling pathway,and promotes osteogenic and chondrogenic differentiation at the tendon bone healing interface in vivo,improving the biomechanical function of the tendon bone healing site.This study provides a new treatment method for osteoporotic rotator cuff tendon bone healing.