Abstract
BackgroundRepeat breeding directly affects reproductive efficiency in cattle due to an increase in services per conception and calving interval. This study aimed to investigate whether changes in endometrial gene expression profile are involved in repeat breeding in cows. Differential gene expression profiles of the endometrium were investigated during the mid-luteal phase of the estrous cycle between repeat breeder (RB) and non-RB cows using microarray analysis.MethodsThe caruncular (CAR) and intercaruncular (ICAR) endometrium of both ipsilateral and contralateral uterine horns to the corpus luteum were collected from RB (inseminated at least three times but not pregnant) and non-RB cows on Day 15 of the estrous cycle (4 cows/group). Global gene expression profiles of these endometrial samples were analyzed with a 15 K custom-made oligo-microarray for cattle. Immunohistochemistry was performed to investigate the cellular localization of proteins of three identified transcripts in the endometrium.ResultsMicroarray analysis revealed that 405 and 397 genes were differentially expressed in the CAR and ICAR of the ipsilateral uterine horn of RB, respectively when compared with non-RB cows. In the contralateral uterine horn, 443 and 257 differentially expressed genes were identified in the CAR and ICAR of RB, respectively when compared with non-RB cows. Gene ontology analysis revealed that genes involved in development and morphogenesis were mainly up-regulated in the CAR of RB cows. In the ICAR of both the ipsilateral and contralateral uterine horns, genes related to the metabolic process were predominantly enriched in the RB cows when compared with non-RB cows. In the analysis of the whole uterus (combining the data above four endometrial compartments), RB cows showed up-regulation of 37 genes including PRSS2, GSTA3 and PIPOX and down-regulation of 39 genes including CHGA, KRT35 and THBS4 when compared with non-RB cows. Immunohistochemistry revealed that CHGA, GSTA3 and PRSS2 proteins were localized in luminal and glandular epithelial cells and stroma of the endometrium.ConclusionThe present study showed that endometrial gene expression profiles are different between RB and non-RB cows. The identified candidate endometrial genes and functions in each endometrial compartment may contribute to bovine reproductive performance.
Highlights
Repeat breeding directly affects reproductive efficiency in cattle due to an increase in services per conception and calving interval
Gene expression profiles of CAR and ICAR in ipsilateral uterine horns A total of 405 and 397 genes were differentially expressed in CAR and ICAR of the ipsilateral uterine horn of repeat breeder (RB) cows, respectively when compared with non-RB cows
(See figure on previous page.) Fig. 3 quantitative real-time RT-PCR (qPCR) analysis of top five up- and down-regulated known genes in whole uterus between RB and non-RB cows for validation of the gene expression changes obtained from microarray analysis. a, b, c, d, e up-regulated known genes in RB cows when compared with non-RB cows. f, g, h, i, j down-regulated known genes in RB cows when compared with non-RB cows
Summary
Repeat breeding directly affects reproductive efficiency in cattle due to an increase in services per conception and calving interval. This study aimed to investigate whether changes in endometrial gene expression profile are involved in repeat breeding in cows. A study of reciprocal transfers of embryos between RB and virgin heifers showed that a higher proportion of embryos transferred from RB to virgin heifers than from virgin to RB heifers survived at day 16 to 17, suggesting that the uterine environment in RB heifers is less suitable than in the virgins for supporting a successful embryo development [4]. About an association between alteration of uterine environment and repeat breeding, Katagiri et al have demonstrated that there is a close relationship between the endometrial epidermal growth factor profile and diminished fertility of RB cows [6]
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