Dynamic expression of SOLD1 in bovine uteroplacental tissues during gestation

Secreted protein of Ly-6 domain 1 (SOLD1), a novel member of the Ly-6 superfamily, is present in the extracellular matrix of the mesenchyme in placental cotyledonary villi and is possibly involved in placental construction.

We investigated bovine SOLD1 expression in uteroplacental tissues with temporo-spatial patterning throughout gestation.

Placentomal and endometrial tissues during gestation were analyzed for SOLD1 mRNA levels by using quantitative RT-PCR. Tissue sections of placentomes and intercaruncular endometrium were used for determining SOLD1 mRNA and protein levels respectively with in situ hybridization and immunohistochemistry.

SOLD1 mRNA was more strongly expressed in fetal membranes than in endometrial tissues on day 35 of pregnancy, and its expression was maintained throughout pregnancy. SOLD1 mRNA was detected in mononucleate cells at early and mid gestation, and, interestingly, in mononucleate and binucleate trophoblast cells at late gestation. It was also present in endometrial epithelial cells and the stroma surrounding uterine glands. SOLD1 protein was widely distributed in the mesenchyme of the villous tree as the pregnancy progressed.

Our study shows the temporo-spatial expression patterns of bovine SOLD1 during gestation in uteroplacental tissues. To our knowledge, this is the first report on the involvement of fetal trophoblastic and endometrial cells in the secretion of SOLD1. These results suggest that SOLD1 may play a crucial role not only in the remodeling of the uteroplacental area, but also in that of the endometrium during late gestation, in addition to its role at early gestation in placental construction.