533. MODULATION OF THE MATERNAL IMMUNE SYSTEM DURING EARLY BOVINE PREGANCY

Abstract

Over the past three decades, there has been a significant decline in dairy cattle fertility. A large proportion of pregnancy losses are believed to occur during the pre-implantation period, when the developing embryo is elongating rapidly and signalling its presence to the maternal system. The molecular mechanisms that prevent progression of the estrous cycle and allow the allogenic embryo to survive within the maternal environment are not well understood. To gain a more complete picture of these molecular events, global transcriptional profiling was performed using endometrial tissue from reproductive day 17 pregnant and non-pregnant (cycling) Holstein-Friesian dairy cattle. Microarray analysis revealed 357 differentially expressed transcripts (with ≥2 fold change in expression; P-value < 0.05) between pregnant and cycling animals in both caruncular and intercaruncular tissue. Additionally, 122 and 26 differentially expressed transcripts were identified only in either caruncular or intercaruncular endometrium, respectively. Pathway analysis of differentially expressed genes revealed enrichment for genes involved in interferon signalling and modulation of the immune response in pregnant animals. Many of these genes have already been described in relation to bovine reproduction. However, this analysis also revealed a number of genes not previously identified in this context, providing further insight into the mechanisms by which the embryo regulates the maternal immune response.