Macrophage-derived Exosomal Mirna Induce Peritendious Adhesion

Objective:Fibrotic healing response developed after tendon injury impairs tendon function and restricts motion,leading to tendon adhesion.Communication between macrophages and tendon cells has a critical role in regulating tendon healing process;however,the mechanisms employed by macrophages to control peritendinous fibrosis are not fully understood.This study aim to look for new molecular targets from the perspective of exosomal-miRNAs,providing a new theoretical basis for the prevention and treatment of tendon adhesion.Methods:Here,the macrophage-deficient mice were constructed using drugs,and the role of macrophages in tendon adhesion was elucidated by gross view,histology and biomechanics after modeling tendon adhesion.Then,the macrophage-derived exosome were extracted.Intravenous reinfusion into macrophage-deficient mice to explore whether exosome causes tendon adhesion.Subsequently,in vitro experiments elucidate the effects of exosome on the biological behavior of fibroblasts and tenocytes.Then,using small RNA deep sequencing to determine the highest content of microRNAs.In vitro transfection with miRNA-mimic or miR-mimic-NC to verify the effect of the miRNA on fibroblasts and tenocytes.Finally,using bioinformatics analysis to predict the downstream target of the disease causing miRNA,and in vitro useing lentivirus and miRNA-mimic co-transfection to verify the validity of the target gene.Results:The depletion of macrophages reduced peritendinous fibrosis in the injured tendon,but treatment with bone marrow macrophage-derived exosomes,which contained miR-21-5p,restarted fibrotic tendon healing.Overexpression of miR-21-5p in fibroblasts and tenocytes induced cell proliferation and migration and upregulated the expression of fibrosis markers such as collagens type I and III and α-SMA,while downregulating SMAD7,a miR-21 target and a member of the TGF-β1 superfamily;however,co-expression with SMAD7 attenuated miR-21-5p effects,suggesting that miR-21 activated fibrogenesis in tendon cells through inhibition of SMAD7.Conclusions:In this study,our results indicated that miR-21-5p delivered by exosomes from bone marrow-derived macrophages promoted proliferation,migration,and fibrotic activity of tendon cells through targeting SMAD7.These findings provide new insights into the role of exosomal miRs secreted by macrophages in tendon adhesion.