Expression of oestrogen receptor [alpha] in the endometrium of porcine reproductive and respiratory syndrome virus-infected gilts

Porcine reproductive and respiratory syndrome (PRRS) virus infection often lead to infertility in gilts and sows. Nevertheless, the impact of PRRS virus on the endometrial function has not been fully elucidated. The present study aimed to determine the effect of PRRS virus infection on the expression of oestrogen receptor (ER) [alpha] in the endometrium of gilts. Uterine tissues from 54 gilts were classified into two groups according to PRRS virus detection using immunohistochemistry (26 positive and 28 negative samples). The reproductive status was classified as prepubertal, luteal and follicular phases. The expression of ER[alpha] in the epithelium, subepithelium and glandular tissue layers of the endometrium was determined by immunohistochemistry. ER[alpha] immunostaining was detected in 22.2, 13.5 and 33.6 % of the cells in the epithelial, subepithelial and glandular tissue layers, respectively. The ER[alpha] immunostaining in the glandular layer of the endometrium in follicular-phase gilts was higher than that in prepubertal gilts (46.1 and 15.2 %, respectively, P=0.011). The ER[alpha] immunostaining in the glandular layer of the endometrium was positively correlated with body weight (r=0.138, P=0.020) and average daily gain (r=0.169, P=0.005) of the gilts. The ER[alpha] immunostaining in all tissue layers of the endometrium with PRRS virus detection did not differ significantly compared to that without PRRS virus (P>0.05). However, in prepubertal gilts, the ER[alpha] immunostaining cells in the epithelial layer of PRRS virus negative (9.5 %) tended to be lower than PRRS virus positive (26.3 %, P=0.196) uterine tissues. This tendency indicates some impact of PRRS virus infection on the ER[alpha] expression in prepubertal gilts.