title: Very small embryonic-like stem cells: implications in reproductive biology.
abstract: The most primitive germ cells in adult mammalian testis are the spermatogonial stem cells (SSCs) whereas primordial follicles (PFs) are considered the fundamental functional unit in ovary. However, this central dogma has recently been modified with the identification of a novel population of very small embryonic-like stem cells (VSELs) in the adult mammalian gonads. These stem cells are more primitive to SSCs and are also implicated during postnatal ovarian neo-oogenesis and primordial follicle assembly. VSELs are pluripotent in nature and characterized by nuclear Oct-4A, cell surface SSEA-4, and other pluripotent markers like Nanog, Sox2, and TERT. VSELs are considered to be the descendants of epiblast stem cells and possibly the primordial germ cells that persist into adulthood and undergo asymmetric cell division to replenish the gonadal germ cells throughout life. Elucidation of their role during infertility, endometrial repair, superovulation, and pathogenesis of various reproductive diseases like PCOS, endometriosis, cancer, and so on needs to be addressed. Hence, a detailed review of current understanding of VSEL biology is pertinent, which will hopefully open up new avenues for research to better understand various reproductive processes and cancers. It will also be relevant for future regenerative medicine, translational research, and clinical applications in human reproduction.
authors.affiliation: Stem Cell Biology Department, National Institute for Research in Reproductive Health (ICMR), Mumbai, Maharashtra 400 012, India. deepa.bhartiya@yahoo.in
authors.forename: Deepa
authors.initials: D
authors.lastname: Bhartiya
authors.forename: Sreepoorna
authors.initials: S
authors.lastname: Unni
authors.forename: Seema
authors.initials: S
authors.lastname: Parte
authors.forename: Sandhya
authors.initials: S
authors.lastname: Anand
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D053595:Embryonic Stem Cells / Q000166:cytology*; D005260:Female; D005298:Fertility; D005718:Gametogenesis; D005819:Genetic Markers; D005855:Germ Layers / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D009866:Oogenesis; D006080:Ovarian Follicle / Q000166:cytology; D010053:Ovary / Q000378:metabolism; D044968:Regenerative Medicine / Q000379:methods*; D012098:Reproduction / Q000502:physiology*; D013091:Spermatogenesis; D013093:Spermatogonia / Q000378:metabolism; D013737:Testis / Q000378:metabolism
chemical_list: D005819:Genetic Markers; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human