The studies, reported by Herraiz et al (2018) published in Fertility and Sterility and commented upon by Prof Bates, clearly tells us that stem cells in human BM  get mobilized into the peripheral blood on injecting G-CSF which are lacking in PBMNCs that help improve ovarian function in chemoablated mice.   Further experiments involving the xenografted human cortical tissue pieces in mice shows that these stem cells have better regenerative potential compared to CD133+ sorted cells. Earlier CD133+ cells were used to treat thin endometrium with marginal benefit. Thanks to Prof Bates for acknowledging our work on VSELs.  We have reported that a novel population of pluripotent stem cells exists in adult ovaries, testes and uterus [https://www.ncbi.nlm.nih.gov/pubmed/27614362] – they survive oncotherapy [https://www.ncbi.nlm.nih.gov/pubmed/25779995] – and can restore non-functional ovary/testis/uterus when a healthy niche is provided by transplanting mesenchymal cells [https://www.ncbi.nlm.nih.gov/pubmed/29128912; https://www.ncbi.nlm.nih.gov/pubmed/28342456; https://www.ncbi.nlm.nih.gov/pubmed/27663915; https://www.ncbi.nlm.nih.gov/pubmed/28911213]. Most probably it is the MSCs that got mobilized have provided beneficial effects and allowed endogenous VSELs in the chemoablated mouse ovary and xenografted human cortical tissue with poor follicular reserve to undergo neo-oogenesis and follicle assembly.  Since human mobilized cells were transplanted in mice – MSCs numbers were perhaps enough to result in beneficial effect.  But G-CSF mobilization of cells in patients with poor ovarian reserve may not suffice to result in beneficial effects in humans.  Best approach will be to expand autologus MSCs and transplant directtly in non-functional ovaries, testes and also in thin endometrium.  Stem cells lodged in ovary surface epithelium can bring about neo-oogenesis and follicle assembly  [https://www.ncbi.nlm.nih.gov/pubmed/29304868; https://www.ncbi.nlm.nih.gov/pubmed/26635884]. Being a basic scientist, I cannot conduct clinical trials but wait for someone to follow this approach.  It will be an international breakthrough and revolutionize reproductive medicine  for the common man including  cancer survivors.

Deepa Bhartiya, PhD; ICMR-National Institute for Research in Reproductive Health, Parel, Mumbai, INDIA  www.nirrh.res.in