Temporal changes in endometrial gene expression and protein localization of members of the IGF family in cattle: effects of progesterone and pregnancy

Abstract

In the study presented, the hypothesis that ligands of the insulin-like growth factor (IGF) family, as well as their binding proteins (BPs), are temporally regulated and are altered by elevated progesterone (P4) and/or pregnancy was tested. Heifers detected in standing estrus following synchronization (n = 210, day 0), were artificially inseminated (n = 140) or left as noninseminated cyclic controls (n = 70). On day 3, half of each group were randomly assigned to receive a P4-releasing intravaginal device resulting in four treatment groups, pregnant and cyclic heifers with high and normal P4 concentrations on either day 5, 7, 13, or 16 of the estrous cycle/early pregnancy. Quantitative real-time PCR and immunohistochemistry were performed on endometrial homogenate and uterine cross sections to measure transcript abundance and protein localization respectively (n = 5 per treatment per time point). No effect of day, treatment, or their interactions was observed for IGF2, IGFBP4, and -5 (P > 0.05). IGF1 and IGFBP6 expression decreased, while IGF1R and IGFBP2 expression increased (P < 0.05) as the days of the cycle or pregnancy progressed. The expression of IGFBP2 was increased by elevated P4; in addition, localization of both IGF2 and IGFBP2 protein in the luminal and superficial glandular epithelium displayed a P4 × day interaction. In conclusion it is proposed that decreased IGF1 and IGFBP6 expression with a coordinate increase in IGF1R and IGFBP2 as the estrous cycle/early pregnancy progresses, along with other factors, are required to establish a uterine environment that promotes the growth and development of the conceptus prior to implantation. In addition, the increased protein abundance of both IGF2 and IGFBP2 observed in heifers supplemented with P4 contributes to the enhanced conceptus elongation observed in this model.

Molecular determinants of a competent bovine corpus luteum: first- vs final-wave dominant follicles

“…3) as animals enter the follicular phase. Expression of uterine IGFBP2 mRNA and protein increases towards the late luteal phase and is thought to be under the regulation of P4 (McCarthy et al 2012, Costello et al 2014. Elevated expression of IGFBP2 transcripts in group C DFs (Table 4) and IGFBP2 protein in follicular phase fluids (Fig.…”

Maternal embryokines that regulate development of the bovine preimplantation embryo

“…IGF1 is also expressed in the uterine endometrium (55,59,60). There is little variation in expression between days 5 and 16 after estrus in cyclic or pregnant cows (61). Endometrial expression of IGF1 was not regulated by somatotropin in 2 experiments (59,60).…”

Global gene expression in endometrium of high and low fertility heifers during the mid-luteal phase of the estrous cycle

“…Using conventional candidate approaches many studies have examined bovine endometrial gene expression under various conditions; during early pregnancy in animals that produced viable and non-viable embryos [23], in pregnant and cycling animals with artificially induced high, and normal systemic progesterone concentrations [24–26] and during the various phases of the estrous cycle [27]. Furthermore global endometrial gene expression analyses have been conducted and include comparisons between cycling and pregnant animals [28, 29], fertile and sub-fertile animal strains [30, 31], progesterone supplementation treatments [32], and specific estrous cycle phases [33, 34].…”