Principal Investigator: Ned Place

DESCRIPTION (provided by applicant): 

Most species of the Felidae family are threatened with extinction. Breeding felids in conservation centers has historically been challenging, resulting in an increased reliance on assisted reproductive technologies (ARTs) such as artificial insemination (AI), ovum pickup (OPU) for in vitro fertilization (IVF), and embryo transfer (ET) to propagate these species. Assisted reproduction in females begins with ovarian stimulation (OS), in which exogenous gonadotropins act directly at the ovaries to increase the numbers of developing follicles, ovulations, and corpora lutea. However, pregnancy failure after OS is very common, and when pregnancies occur, litter sizes are low. These problems persist even after optimizing the numbers and quality of sperm, oocytes, and embryos, suggesting that diminished reproductive success after OS may arise from defects in the maternal reproductive tract. OS increases the numbers of hormone-secreting follicles and corpora lutea, which has been shown to create an abnormal endocrine environment in several felid species, including domestic cats. Similar hormonal responses in rodents and humans have numerous effects on the uterus that hinder embryonic implantation. It is unknown whether these same secondary effects occur after OS in felids, but if so, they could contribute to the low pregnancy rates and litter sizes observed after assisted reproduction in this taxon. The present study will assess structural and molecular outcomes in domestic cat uteri. Intact, sexually-mature queens will undergo either natural estrus with physiological ovulation after vaginal stimulation (VS) or OS using gonadotropins. Cats will be spayed two weeks after ovulation to coincide with the window of implantation, and ovaries, blood serum, and uteri will be collected. Adequate preparation of the endometrium, the innermost uterine layer, is a major determinant of implantation success, and various aspects of this tissue will be compared between groups. This study has two main aims: comparing the morphological and the molecular responses of the endometrium to OS versus VS. Morphological outcomes, including structural dimensions, vascular remodeling, immune cell population, and occurrence of cellular differentiation, will be assessed using histological, immunohistochemical, and immunofluorescent techniques. Molecular outcomes, including differential gene expression (RT-qPCR, RNA-sequencing) and protein localization (immunohistochemistry) will also be assessed. Comparison of the endometrial responses to OS and VS will generate new understandings of felid implantation biology and provide potential targets for interventions that affect implantation success. Future clinical applications include optimized OS protocols to improve felid ART outcomes and novel, nonsurgical methods of feline contraception.