ENDOMETRIAL CONNEXIN EXPRESSION IN THE MARE AND PIG - EVIDENCE FOR THE SUPPRESSION OF CELL-CELL COMMUNICATION IN UTERINE LUMINAL EPITHELIUM

This investigation examines the relationship between implantation stra tegy and gap junction protein expression in uterine endometrium. The p attern of gap junction and connexin protein expression was analyzed in porcine and equine endometrium from cycling and pregnant animals usin g electron microscopy and immunocytochemistry. Functional analysis of cell cell communication was also monitored by laser cytometry in prima ry cultures of endometrial epithelial cells. Gap junctions were detect ed in endometrial stroma of cycling and pregnant animals, which was co rrelated with immunoreactive Cx43 within stromal fibroblasts and vascu lar elements. No Cx26, Cx32, or Cx43 immunostaining was detected in lu minal endometrial epithelium in either the mare or the pig at any stag e of the estrous cycle or pregnancy. In contrast, endometrial glands o f the mare exhibited a spatiotemporal pattern of Cx43 expression in th e apicolateral plasma membrane which, when present, colocalized with t he tight junction-associated protein, ZO-1. Uterine glandular Cx43 exp ression in mares was present from day 3 postovulation through day 14 o f diestrus and until day 23 of pregnancy, whereas Cx43 was absent with in uterine glands during seasonal anestrus, estrus, and after day 30 o f pregnancy. Primary cultures of equine endometrial epithelial cells e xpressed both immunoreactive Cx43 and significant gap junction-mediate d intercellular communication (GJIC) which was rapidly upregulated by 1.0 mM 8-bromo-cAMP or blocked with 1.0 mM octanol. No GJIC or connexi n protein was detected in cultured porcine epithelial cells despite in cubation with a variety of agents, including 8-bromo-cAMP, steroid hor mones, retinoic acid, and/or prolactin. Junctional communication in en dometrial epithelium of domestic farm animals is different than that r eported for species exhibiting invasive implantation. The absence of G JIC in uterine luminal epithelium of the gilt and mare may be involved in limiting trophoblast invasiveness. Anat. Rec. 251:277-285, 1998. ( C) 1998 Wiley-Liss, Inc.