Spermatogenic dysfunction caused by cyclophosphamide(CP)chemotherapy has seriously influenced the life quality of patients.Unfortunately,treatments for CP-induced testicular spermatogenic dysfunction are limited,and the molecular mechanisms are not fully understood.For the first time,here,we explored the effects of bone marrow mesenchymal stem cell-derived exosomes(BMSC-exos)on CP-induced testicular spermatogenic dysfunction in vitro and in vivo.BMSC-exos could be taken up by spermatogonia(GC1-spg cells).CP-injured GC1-spg cells and BMSC-exos were cocultured at various doses,and then,cell proliferation was measured using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide(MTT)assay.In addition,photophosphorylation of extracellular-regulated kinase(ERK),p38 mitogen-activated protein kinase(p38MAPK),and protein kinase B(AKT)proteins was evaluated by western blotting as well as apoptosis in GC1-spg cells measured using flow cytometry.Treatment with BMSC-exos enhanced cell proliferation and reduced apoptosis of CP-injured GCI-spg cells.Phosphorylated levels of ERK,AKT,and p38MAPK proteins were reduced in CP-injured spermatogonia when co-treated with BMSC-exos,indicating that BMSC-exos acted against the reproductive toxicity of CP via the p38MAPK/ERK and AKT signaling pathways.In experiments in vivo,CP-treated rats received BMSC-exos by injection into the tail vein,and testis morphology was compared between treated and control groups.Histology showed that transfusion of BMSC-exos inhibited the pathological changes in CP-injured testes.Thus,BMSC-exos could counteract the reproductive toxicity of CP via the p38MAPK/ERK and AKT signaling pathways.The findings provide a potential treatment for CP-induced male spermatogenic dysfunction using BMSC-exos.