Abstract
BackgroundWe have earlier reported that follicle stimulating hormone (FSH) modulates ovarian stem cells which include pluripotent, very small embryonic-like stem cells (VSELs) and their immediate descendants ‘progenitors’ termed ovarian germ stem cells (OGSCs), lodged in adult mammalian ovarian surface epithelium (OSE). FSH may exert pleiotropic actions through its alternatively spliced receptor isoforms. Four isoforms of FSH receptors (FSHR) are reported in literature of which FSH-R1 and FSH-R3 have biological activity. Present study was undertaken to identify FSHR isoforms mediating FSH action on ovarian stem cells, using sheep OSE cells culture as the study model.MethodsCultures of sheep OSE cells (a mix of epithelial cells, VSELs, OGSCs and few contaminating red blood cells) were established with and without FSH 5IU/ml treatment. Effect of FSH treatment on self-renewal of VSELs and their differentiation into OGSCs was studied after 15 hrs by qRT-PCR using markers specific for VSELs (Oct-4A, Sox-2) and OGSCs (Oct-4). FSH receptors and its specific transcripts (R1 and R3) were studied after 3 and 15 hrs of FSH treatment by immunolocalization, in situ hybridization and qRT-PCR. FSHR and OCT-4 were also immuno-localized on sheep ovarian sections, in vitro matured follicles and early embryos.ResultsFSH treatment resulted in increased stem cells self-renewal and clonal expansion evident by the appearance of stem cell clusters. FSH receptors were expressed on ovarian stem cells whereas the epithelial cells were distinctly negative. An increase in R3 mRNA transcripts was noted after 3 hrs of FSH treatment and was reduced to basal levels by 15 hrs, whereas R1 transcript expression remained unaffected. Both FSHR and OCT-4 were immuno-localized in nuclei of stem cells, showed nuclear or ooplasmic localization in oocytes of primordial follicles and in cytoplasm of granulosa cells in growing follicles.ConclusionsFSH modulates ovarian stem cells via FSH-R3 to undergo potential self-renewal, clonal expansion as ‘cysts’ and differentiation into oocytes. OCT-4 and FSHR proteins (required initially to maintain pluripotent state of VSELs and for FSH action respectively) gradually shift from nuclei to cytoplasm of developing oocytes and are later possibly removed by surrounding granulosa cells as the oocyte prepares itself for fertilization.
Highlights
Follicle stimulating hormone (FSH) is a pleiotropic hormone produced by the pituitary that exerts diverse actions on the gonads like growth, proliferation, differentiation, facilitates steroidogenesis and acts as an anti-apoptotic survival factor in vitro, besides being associated with post-menopausal bone loss [1] and is implicated in various kind of tumors [2,3,4]
OCT-4 and FSH receptors (FSHR) proteins gradually shift from nuclei to cytoplasm of developing oocytes and are later possibly removed by surrounding granulosa cells as the oocyte prepares itself for fertilization
We have reported that besides the granulosa cells of antral follicles, follicle stimulating hormone (FSH) receptors are expressed in adult mouse ovary surface epithelium (OSE), which houses the pluripotent very small ES-like stem cells (VSELs) and ovarian germ stem cells (OGSCs)
Summary
Follicle stimulating hormone (FSH) is a pleiotropic hormone produced by the pituitary that exerts diverse actions on the gonads like growth, proliferation, differentiation, facilitates steroidogenesis and acts as an anti-apoptotic survival factor in vitro, besides being associated with post-menopausal bone loss [1] and is implicated in various kind of tumors [2,3,4]. Evidence is available that blocking FSH action results in azoospermia in non-human primates [18] and a significant loss of primordial follicles in hamster ovaries [19]. It remains rather ambiguous at present whether FSH regulates germ cells function indirectly through the granulosa or Sertoli cells or does FSH exert direct action on both the somatic and germ cell compartment in the gonads. Present study was undertaken to identify FSHR isoforms mediating FSH action on ovarian stem cells, using sheep OSE cells culture as the study model
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
