Submitted January 15, 2008
Returned for revision February 10, 2008
Accepted April 21, 2008
Ovary
Involvement of the KIT/KITL Signaling Pathway in 4-Vinylcyclohexene Diepoxide-Induced Ovarian Follicle Loss in Rats
Shannon M. Fernandez ,
Aileen F. Keating ,
Patricia J. Christian ,
Nivedita Sen ,
James B. Hoying ,
Heddwen L. Brooks ,
and
Patricia B. Hoyer *
* To whom correspondence should be addressed. E-mail: hoyer{at}u.arizona.edu.
Abstract
Repeated daily dosing of rats with the occupational chemical, 4-vinylcyclohexene diepoxide (VCD), depletes the ovary of primordial and primary follicles through an increase in the natural process of atresia. Additionally, in vitro exposure of postnatal day 4 (PND4) rat ovaries to VCD causes similar follicular depletion. This study was designed to investigate survival signaling pathways that may be associated with VCD-induced ovotoxicity in small pre-antral follicles. Female Fischer 344 rats (PND28) were dosed daily (80mg/kg/day VCD i.p.; 12d in vivo) and PND4 ovaries were cultured (VCD 20 or 30 µM; 8d in vitro). Microarray analysis identified a subset of 14 genes whose expression was increased or decreased by VCD in both experiments (ie. via both exposure routes). Particularly, the analysis showed that relative to controls VCD did not affect mRNA expression of growth and differentiation factor 9 (Gdf9), whereas, there were decreases in mRNA encoding bone morphogenic protein receptor 1a (Bmpr1a) and Kit. To confirm findings from microarray, the genes, Gdf9, Bmpr1a, and Kit were further examined. When growth factors associated with these pathways were added to ovarian cultures during VCD exposure, GDF9 and BMP4 had no effect on VCD-induced ovotoxicity; however KITL attenuated this follicle loss. Additionally, there was a decrease in Kit and an increase in Kitl expression (mRNA and protein) following VCD exposure, relative to control. These results support that VCD compromises KIT/KITL signaling, which is critical for follicular survival in primordial and primary follicles.
Key words:
Ovary •
Kit •
Kitl •
ovotoxicity •
pre-antral follicles
