Presentation Title

Inhibitory photoperiod alters mRNA expression of FSH-Responsive but not FSH-Independent Folliculogenic Factors in Siberian Hamsters (Phodopus sungorus)

Start Date

November 2016

End Date

November 2016

Location

HUB 302-56

Type of Presentation

Poster

Abstract

Exposure to short photoperiods typical of the non-breeding season reduces ovarian activity in Siberian hamsters, whereas exposure to long photoperiods stimulates return of ovarian function in a process known as ovarian recrudescence. While the endocrine changes driving this transition are well understood, little is known about how folliculogenesis itself resumes with photostimulation. Because it is likely that growth and transcription factors that mediate folliculogenesis are involved in the return of ovarian function, we hypothesized that mRNA expression of key folliculogenic factors would change during recrudescence. To address this hypothesis, hamsters were exposed to either long days (LD, 16h of light and 8h of dark, control) or short days (SD, 8L:16D, regressed) for 14 weeks. A subset of SD hamsters were then transferred into LD for 2, 4, or 8 weeks to induce recrudescence (post transfer, PT groups). While exposure to short photoperiod reduced the number of tertiary follicles and corpora lutea as compared to LD and PT8 ovaries, no changes were noted in the number of primordial, primary, or secondary follicles. Similarly, mRNA expression of FSH-independent transcription and growth factors that mediate primordial to primary follicle development (SOHLH1, NOBOX, c-KIT, and KITL) did not change across photoperiod groups. In contrast, mRNA for FSH-dependent factors that regulate growth of later stage follicles (FSHR, Inhibin-α) was reduced in SD as compared to LD and PT8 ovaries. These data suggest that the photoinhibited ovary is not completely quiescent, as gonadotropin-independent stages of follicle development are not affected by changes in photoperiod in Siberian hamsters.

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Inhibitory photoperiod alters mRNA expression of FSH-Responsive but not FSH-Independent Folliculogenic Factors in Siberian Hamsters (Phodopus sungorus)

HUB 302-56

Exposure to short photoperiods typical of the non-breeding season reduces ovarian activity in Siberian hamsters, whereas exposure to long photoperiods stimulates return of ovarian function in a process known as ovarian recrudescence. While the endocrine changes driving this transition are well understood, little is known about how folliculogenesis itself resumes with photostimulation. Because it is likely that growth and transcription factors that mediate folliculogenesis are involved in the return of ovarian function, we hypothesized that mRNA expression of key folliculogenic factors would change during recrudescence. To address this hypothesis, hamsters were exposed to either long days (LD, 16h of light and 8h of dark, control) or short days (SD, 8L:16D, regressed) for 14 weeks. A subset of SD hamsters were then transferred into LD for 2, 4, or 8 weeks to induce recrudescence (post transfer, PT groups). While exposure to short photoperiod reduced the number of tertiary follicles and corpora lutea as compared to LD and PT8 ovaries, no changes were noted in the number of primordial, primary, or secondary follicles. Similarly, mRNA expression of FSH-independent transcription and growth factors that mediate primordial to primary follicle development (SOHLH1, NOBOX, c-KIT, and KITL) did not change across photoperiod groups. In contrast, mRNA for FSH-dependent factors that regulate growth of later stage follicles (FSHR, Inhibin-α) was reduced in SD as compared to LD and PT8 ovaries. These data suggest that the photoinhibited ovary is not completely quiescent, as gonadotropin-independent stages of follicle development are not affected by changes in photoperiod in Siberian hamsters.