Presentation Title

Short Photoperiod Exposure Induces Declines in Ovarian Levels of Vascular Endothelial Growth Factor

Faculty Mentor

Kelly Young

Start Date

18-11-2017 2:15 PM

End Date

18-11-2017 3:15 PM

Location

BSC-Ursa Minor 76

Session

Poster 3

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

Reproductive function of many seasonally breeding mammals, including Siberian hamsters (Phodopus sungorus), is regulated by photoperiod. Exposure to long days (16 hours of light:8h of dark; LD) stimulates and maintains ovarian function. In contrast, exposure to short days (8L:16D, SD) induces ovarian atrophy. While it was known that inhibitory photoperiods suppress ovarian function through inhibition of the hypothalamic pituitary gonadal axis, little is known about the changes in key ovarian processes during restoration of ovarian function. Angiogenesis, or development of new blood vessels, is a potentially important process in ovarian recrudescence. Vascular endothelial growth factor (VEGF) is a protein that mediates angiogenesis in the normal, cycling ovary. We hypothesized that 1) SD exposure would reduce ovarian function, and 2) VEGF protein would be present and differentially-regulated in ovaries of females exposed to LD, SD, or those exposed first to short days for 14 weeks and then transferred to long days for two weeks (PT) to restore ovarian cyclicity. Ovarian mass, plasma estradiol, number of antral follicles and number of corpora lutea all significantly declined with exposure to SD, and were restored to LD levels in the PT group. This pattern was mirrored with the overall VEGF immunostaining extent; however, overall VEGF protein immunostaining intensity peaked in LD, declined significantly in SD and remained low in PT. When immunostaining in individual structures was assessed, a similar pattern of declines in both SD and PT was seen in both stroma and secondary follicles. Taken together, recovery of ovarian function may involve changes in intra-ovarian protein levels of VEGF. It is likely that angiogenesis is a critical component of restoring the ovary to function.

Key Words: Ovary, VEGF, seasonal reproduction, photoperiod

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Nov 18th, 2:15 PM Nov 18th, 3:15 PM

Short Photoperiod Exposure Induces Declines in Ovarian Levels of Vascular Endothelial Growth Factor

BSC-Ursa Minor 76

Reproductive function of many seasonally breeding mammals, including Siberian hamsters (Phodopus sungorus), is regulated by photoperiod. Exposure to long days (16 hours of light:8h of dark; LD) stimulates and maintains ovarian function. In contrast, exposure to short days (8L:16D, SD) induces ovarian atrophy. While it was known that inhibitory photoperiods suppress ovarian function through inhibition of the hypothalamic pituitary gonadal axis, little is known about the changes in key ovarian processes during restoration of ovarian function. Angiogenesis, or development of new blood vessels, is a potentially important process in ovarian recrudescence. Vascular endothelial growth factor (VEGF) is a protein that mediates angiogenesis in the normal, cycling ovary. We hypothesized that 1) SD exposure would reduce ovarian function, and 2) VEGF protein would be present and differentially-regulated in ovaries of females exposed to LD, SD, or those exposed first to short days for 14 weeks and then transferred to long days for two weeks (PT) to restore ovarian cyclicity. Ovarian mass, plasma estradiol, number of antral follicles and number of corpora lutea all significantly declined with exposure to SD, and were restored to LD levels in the PT group. This pattern was mirrored with the overall VEGF immunostaining extent; however, overall VEGF protein immunostaining intensity peaked in LD, declined significantly in SD and remained low in PT. When immunostaining in individual structures was assessed, a similar pattern of declines in both SD and PT was seen in both stroma and secondary follicles. Taken together, recovery of ovarian function may involve changes in intra-ovarian protein levels of VEGF. It is likely that angiogenesis is a critical component of restoring the ovary to function.

Key Words: Ovary, VEGF, seasonal reproduction, photoperiod