Pharmacological Intervention On Peritendinous Adhesion And Related Biological Mechanisms

OBJECTIVESperitendinous adhesion,a common complication in the field of hand surgery,has been one of the most difficult problems for clinicians.The pathological manifestations of peritendinous adhesion include excessive cell proliferation,activation of fibroblasts,and the deposition of extracellular matrix.Although drugs,physical barriers,rehabilitation exercises and other means have been used to prevent the formation of peritendinous adhesion,the effects are not completely satisfactory.Recent studies have found that some small molecule drugs also play a role in anti-fibrosis,such as metformin and rapamycin.With in vivo and in vitro experiments,the present study proposed the protective roles and related mechanism of metformin and rapamycin on preventing peritendinous adhesion formation,which provide theoretical basis for the prevention and treatment of peritendinous adhesion.METHODSIn the first part of the study,first,we performed in vitro experiments using the NIH/3T3 mouse fibroblast cell line.We evaluated the effect of metformin treatment on fibrosis-related gene expressions and cell physiological actions.We further verified whether or not it depended on the activation of AMPK pathway.Then we constructed a deep flexor tendon injury rat model,and orally administrated metformin(200 mg/kg/d)for 21 days.Through gross evaluation,histological evaluation,analysis of gene expression,we analyzed the effect of metformin on progression of peritendinous adhesion.In the second part,we firstly explored the effect of rapamycin on fibrosis-related gene expressions and cell cycle regulation.Furthermore,we applied autophagy inhibitors and si RNA to verify whether the effect of rapamycin was dependent on the activation of autophagy.Then we treated tendon-injured rats with rapamycin(2 mg/kg/d)or equivalent volume of DMSO by intraperitoneal injection,and evaluated the effect of rapamycin on autophagy activity and severity of peritendinous adhesion.RESULTSMetformin treatment also reduced col1,col3,and ?-SMA expression levels and excessive proliferation induced by TGF-?1.However,when AMPK signaling pathway was interfered by Compound C or AMPK si RNA,the protective effects of metformin were abolished.At 21 days after tendon injury in rats,histological analysis showed that there was obvious peritendinous adhesion formation.After the rats were orally administrated with metformin,the general observation and histological analysis showed that the degree of tendon adhesion decreased significantly,and the expression of adhesion related genes was significantly reduced.In fibroblasts,rapamycin treatment inhibited col1,col3,and ?-SMA expression,promoted G0/G1 cell phase arrest,and reduced of cell proliferation.However,when autophagy was inhibited by the application of 3-MA and atg5 si RNA,the protective effects of rapamycin were abolished.Through macroscopic and histologic evaluation,western blot analysis,and immunohistochemical analysis,we found that intraperitoneal injection of rapamycin significantly alleviated the formation of adhesion after tendon injury in rats.CONCLUSIONSAfter tendon is injured,fibroblast activation and extracellular matrix deposition lead to the progression of peritendinous adhesion.Metformin and rapamycin prevented peritendinous adhesion formation through activation of AMPK signaling pathway and autophagy respectively.The present study shows high research value,and provides a theoretical basis for the clinical prevention of peritendinous adhesion.