Effects of Low Progesterone on the Endometrial Transcriptome in Cattle1

Abstract

The objective of the present study was to determine how low progesterone (P4) affects the endometrial transcriptome, with specific emphasis on those changes that may impact conceptus elongation. Following estrous synchronization and detection (estrus ¼ Day 0, n ¼ 40), heifers were randomly assigned to a control group (n ¼ 12) or a low P4 group (n ¼ 28). Heifers in the low P4 group had consistently lower P4 concentrations compared to controls (P , 0.05). Microarray analysis of endometrial gene expression revealed low P4 altered the expression of 498 differentially expressed genes (DEGs; 215 up-and 283 down-regulated) on Day 7 and 351 DEGs (272 upand 79 down-regulated) on Day 13. A similar number of temporal changes occurred between Day 7 and Day 13 in both groups (2212 in heifers with normal P4 compared with 2247 in heifers with low P4); of these DEGs, 1278 were common to both groups. Little overlap in the number of DEGs affected by high or low P4 was observed across days. Comparison of the temporal changes that occur during normal estrous cycle progression (i.e., from Day 7 to Day 13) to those affected by altered P4 found significant numbers of genes were modulated by elevated (4157) and decreased (809) P4 alone. Analysis of selected genes by quantitative real-time PCR and in situ hybridization revealed that expression of MEP1B, NID2, and PRSS23 increased on Day 13 compared to Day 7 (P , 0.05) and that the magnitude of increase was significantly diminished in heifers with low P4 compared to controls. MEP1B predominantly localized to the both the superficial and deep glandular epithelium (GE), NID2 localized to the deep GE, whereas PRSS23 localized only to the luminal epithelium. In conclusion, we have determined the global changes in the endometrial transcriptome induced by decreasing the output of P4 from the corpus luteum in vivo using a unique animal model. Placing these data into context with previous data in which P4 was supplemented or elevated after ovulation, we have identified a panel of genes that are truly regulated in the endometrium by circulating concentrations of P4 in vivo and that likely impact conceptus elongation.

Maternal-embryo interaction leading up to the initiation of implantation of pregnancy in cattle

“…Most convincingly, the embryo does not need to be present in the uterus during the period of P4 elevation in order to benefit from it (Clemente et al, 2009;O'Hara et al, 2014), strongly suggesting that the effect of P4 is via advancing the endometrial transcriptome (Forde et al, 2009) resulting in advancing conceptus elongation (Carter et al, 2008;Clemente et al, 2009). In addition reducing the output of P4 from the CL results in a delay in the temporal changes in the endometrial transcriptome resulting in delayed conceptus elongation in vivo (Forde et al, 2011a and2012a).…”

“…These are necessary to drive the changes required in the endometrium (and resulting histotroph), in order to provide the embryo/conceptus with the nutritional requirements it needs, which change as the embryo undergoes distinct morphological events. Data on the pre-hatching embryo indicate that the expression of a large number of genes and pathways (Forde et al, 2009(Forde et al, , 2011b(Forde et al, and 2012a, including aminopeptidase, lipoprotein lipase and lactotransferrin amino acids, ions and glucose (Hugentobler et al, 2007 and as well as proteins in the histotroph including Ezrin, triosephosphate isomerase, Glutathione S transferase mu, Cathepsin D, Annexin A1, which were more abundant in the histotroph than in circulation (Faulkner et al, 2012). This expression pattern is governed, in part, by the expression of the nuclear P4 receptor (PGR) in the LE and glandular epithelium (GE).…”

“…Coordinate with this event is an alteration in the overall transcriptional profile of the endometrium (Forde et al, 2012a and allowing the switching on of genes (and their protein products) that have been shown to drive conceptus elongation in cattle or other species. This includes the increased expression and or secretion of the proteins IGFBP1 (Simmons et al, 2009), GRP, APOA1, ARSA, LCAT, NCDN, PLIN , Legumin, TIMP2 (Ledgard et al, 2009) and RBP4 (Costello et al, 2010;Mullen et al, 2012) into the uterine lumen where they are available to help promote conceptus elongation.…”

“…First, supplementation with exogenous P4 advances the down-regulation of the PGR (Okumu et al, 2010) while delaying the output of P4 from the CL, delays the down-regulation of the PGR (Forde et al, 2011a). This has consequences for the expression of genes that contribute to the histotroph; elevating P4 advances or increases the expression of genes while low P4 delays or decreases the expression of genes known to be important for histotroph composition including ANPEP, APOA1, DGAT2, FABP3, IGFBP1, IHH, LCAT, LPL, LTF, MEP1B, NID2, NMN, NPNT, NXPH3, PENK, PLIN2, PRSS23, RBP4, SCG5, SERPINA14, TINGAL1 and TFF3 (Costello et al, 2010;Forde et al, 2011a and2012a;Mullen et al, 2012). The P4 modification of the expression of these genes, and in some cases their protein products, results in a change in the capacity of the uterus to support conceptus elongation.…”

63 Effect of Endometrial Biopsy on Uterine Health of Tropically Adapted Beef Cattle

“…Similarly, although my results confirmed the hypothesis that EB performed at Day 7 post-oestrus will not affect the CL lifespan, CL functionality is impaired throughout the oestrous cycle due to the lower level of P4 found in heifers biopsied at Day 7 post-oestrus compared to heifers biopsied at Day 4 post-oestrus. Since the role of P4 during the second week of gestation is to regulate embryo elongation (Betteridge and Fléchon, 1988) and it is also required for a successful maternal recognition of pregnancy, reduction of P 4 output from the CL results in changes to the endometrial transcriptome which in turn is responsible for a delay in conceptus elongation (Clemente et al, 2009, Forde et al, 2012. In conclusion, this Model could be the most accurate and indicative of endometrial receptivity but embryo survival may be highly compromised.…”