The Therapeutic Potential and Mechanism of Amniotic Fluid Stem Cells in Rescuing Fertility in Mice with Chemotherapy-Induced Premature Ovarian Failure

Chemotherapy (CTx) is commonly used for treating various malignant tumors and for improving the survival rate of cancer patients. However, CTx causes damage to ovarian granulosa cells (GCs), which are required for oocyte survival and follicle development, and results in irreversible premature ovarian failure (POF) in female patients. Recently, amniotic fluid stem cells (AFSCs) emerge as a novel source for regenerative medicine due to their easy accessibility, primitive stage and low immunogenicity. These findings suggest the potential of AFSCs for treating ovarian failure in clinic, but its restorative efficacy and mechanisms are still unclear. In this study, AFSCs were isolated from transgenic mice that ubiquitously express enhanced green fluorescence protein (EGFP), which enables us to trace the fate of AFSCs after transplantation. These AFSCs exhibit morphologies, immunophenotypes, and mesoderm trilineage differentiation potentials similar to mesenchymal stem cells (MSCs). Further, AFSCs proliferate faster than MSCs and express OCT4, a marker for pluripotency. After transplanting into the ovaries of CTx-mice, AFSCs could rescue the reproductive ability of CTx-mice by preventing follicle atresia and sustaining the healthy follicles. Notably, the transplanted AFSCs did not differentiate into GCs and germline cells in vivo. Next, I demonstrate that the therapeutic effects of AFSCs mainly derived from their secretory factors in which AFSC-derived exosomes reproduce the anti-apoptotic effect on CTx-damaged GCs. AFSC-derived exosomes prevent ovarian follicular atresia in CTx-mice via the delivery of microRNAs (miRNAs) in which both miR-146a and miR-10a are highly enriched and their potential target genes are critical to apoptosis. Down-regulation of these two miRNAs in AFSC-derived exosomes attenuates the anti-apoptotic effect on CTx-damaged GCs in vitro whereas administration of these miRNAs recapitulates the effects both in vitro and in vivo in which miR-10a contributes a dominant influence. These findings suggest a potential mechanism for the effects of AFSCs on CTx-damaged ovaries and the dominant role of miR-10a in the regenerative process that implies the promise of a new cell-free therapeutics for treating POF.