ABSTRACT TYSON, AMY MICHELLE. Toll-like Receptors in the Bovine Corpus Luteum.

ABSTRACT TYSON, AMY MICHELLE. Toll-like Receptors in the Bovine Corpus Luteum. (Under the direction of Dr. Daniel H Poole).

Understanding of the mechanisms controlling the reproductive cycle will maximize the sustainability of today’s animal industry. The corpus luteum (CL) is a transient endocrine organ that forms after ovulation, controls the reproductive cycle, and is required for maintenance of pregnancy. Toll-like receptors (TLR) are found in a variety of tissues and mediate the immune response by recruiting cytokines during inflammatory-like processes. Previous studies have demonstrated the role of immune cells within the CL. However, the mechanisms regulating the cellular interactions within the CL remain largely unknown; therefore, the objectives of this project were to examine TLR expression during the luteal lifespan and in cultured luteal cells treated with TLR ligands. Bovine CL at various stages of luteal development (stage I, days 1-4; stage II, days 5-10; stage III, days 11-17; stage IV, days 18-21, and CL of pregnancy) were collected at a local abattoir. Luteal tissue was immediately frozen in liquid nitrogen for RNA analysis. Polymerase chain reaction (PCR) was used to detect TLR1-TLR4, TLR7-TLR8, and TLR10, TLR4 signaling components (MD2 and CD14), CD45 (a marker for leukocytes), and cytokine (TNF, IFNG, IL6, IL12, and TGFβ) mRNA expression. In addition, luteal cells from stage III CL (n=3) were dissociated and cultured with TLR4 and TLR1/TLR2 ligands to evaluate TLR role in luteal function via quantitative PCR. Preliminary data, using semi-quantitative PCR analysis, revealed differential expression in TLR across CL stages. Expression of TLR1, TLR2, TLR4, and TLR6 mRNA through quantitative PCR was greatest in stage IV compared to other stages (p