Transcriptional analysis of WNT-related genes in uterine samples on day 16 from pregnant and non-pregnant Holstein dairy cows.

Two hundred Holstein dairy cows (milk yield of 34.5 ± 0.6 kg/d, 3.1 ± 1.2 lactations) were enrolled to investigate the role of WNTs signaling network in early pregnancy loss. The ISG15 mRNA abundance of uterine luminal cells obtained via brushing on day 16 after service was used to determine initial pregnancy status, with confirmation via ultrasound on days 32 and 60. The mRNA abundance of cells obtained from uterine brushing for WNT2, WNT5A, WNT7A, WNT11, frizzled receptors (FZD), dickkopf proteins (DKK1), Kremen and LDL receptor related protein (LRP 5/6), lymphoid enhancer-binding factor 1 (LEF1) and transcription factor 7 (TCF) was determined at day16 after insemination. Relative mRNA abundance of DKK1 (1.98-fold), WNT5A (2.67-fold), WNT7A (1.83-fold) and WNT11 (2.16-fold) genes in pregnant cows were significantly greater than in cows with early embryonic mortality (P < 0.05). In contrast, relative mRNA abundance of WNT2 (3.35-fold) and FZD6 (5.50-fold) genes were significantly greater in pregnant-embryo loss cows compared to pregnant cows on day 16 (P < 0.05). The relative mRNA abundance of LRP5, LRP6, LEF1, FZD3, FZD5, FZD8 and TCF genes were not affected by pregnancy status although their variances were lower; however, there was a negative correlation among ISG15 and these genes. In conclusion, differences in mRNA abundance of WNT signaling genes in uterine brushing samples are associated with pregnancy status in lactating dairy cows and may contribute to minimizing early bovine pregnancy losses.