Exosomal miRNA-320a Is Released from hAMSCs and Regulates SIRT4 to Prevent Reactive Oxygen Species Generation in POI

Human amniotic mesenchymal stem cells (hAMSCs) were previously shown to effectively rescue ovarian function in a premature ovarian insufficiency (POI) mouse model. The therapeutic mechanism of hAMSC-derived exosomes (hAMSC-Exos) is not fully understood. In this study, the therapeutic mechanism involved in exosomal microRNA-320a (miR-320a) and Sirtuin 4 (SIRT4) was investigated in POI mouse ovaries oocytes and human granulosa cells (hGCs) by fluorescence-activated cell sorting (FACS), hematoxylin and eosin (H&E) staining, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence experiments. hAMSC-Exos improved proliferation, inhibited apoptosis, and decreased the expression of SIRT4 and relative genes in POI hGCs and ovaries. hAMSC-Exos elevated ovarian function and prohibited SIRT4 expression in oogenesis. The therapeutic effects were attenuated when miR-320a was knocked down. hAMSC-Exos decreased the ROS levels in POI hGCs and oocytes and improved ovarian weight and litter size, except for the Exos^{anti-miR-320a}/POI group. Finally, hAMSC-Exos reduced the SIRT4 and ROS levels in POI ovaries and hGCs. The downstream protein expression (ANT2, AMP-dependent kinase [AMPK], and L-OPA1) was downregulated in the hGCs-SIRT4^KD group but disappeared in the Exos^{anti-miR-320a}/POI group. Our study is the first to illustrate the therapeutic potential of hAMSC-Exos in POI. Exosomal miR-320 plays a key role in the hAMSC-Exos-mediated effects on ovarian function via SIRT4 signaling.