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(218) TROPHOBLAST CELLS INVADING THE UTERINE MESOMETRIAL TRIANGLE POSSESS A NOVEL ENDOCRINE PHENOTYPE. Ain, Rupasri1, Kent, Lindsey1, Dai, Guoli1, Soares, Michael, 1 Department of Molecular and Integrative Physiology, Kansas City, KS ABSTRACT- Cells of the trophoblast lineage have the capacity to invade into the uterine endometrium and establish relationships with the uterine vasculature. This process is characteristic of human and also rat placentation. In the rat, trophoblast cells arising from the chorioallantoic placenta are activated to invade into the endometrium during the last week of gestation. These trophoblast cells penetrate through the decidual capsule and congregate in the mesometrial triangle (metrial gland); a site consisting of a prominent collection of blood vessels supplying the placenta and associated natural killer (NK) cells. Two populations of invasive trophoblast cells are evident: i) interstitial and ii) endovascular. In this report, we have investigated the endocrine phenotype of trophoblast cells associated with the mesometrial triangle. Mesometrial triangle and placental tissues were dissected from pregnant rats during the last week of gestation. RNA was isolated and analyzed with the prolactin (PRL) family miniarray and by Northern analysis. Trophoblast cell distributions and phenotypes were assessed by cytokeratin immunocytochemistry and in situ hybridization for PRL family members. NK cells were identified by their expression of perforin. Both the placenta and the mesometrial triangle expressed members of the PRL family. In contrast to the placenta, the mesometrial triangle expressed a unique subset of only three PRL family members, PRL-like protein-A (PLP-A), PLP-L, and PLP-M. PLP-A mRNA was localized to both interstitial and endovascular trophoblast cells. NK cell and trophoblast cell numbers were reciprocally related. PLP-A is a known NK cell regulator and its production by trophoblast cells of the mesometrial triangle further highlights its importance. Although, the biology of PLP-L and PLP-M are yet to be described, their unique pattern of expression by trophoblast cells of the mesometrial triangle implicate them as potential regulators of the resident immune cells and/or vasculature. In conclusion, invasive trophoblast cells of the mesometrial triangle exhibit an endocrine phenotype; corroborating early speculations that the metrial gland possessed an endocrine function. (Supported by the American Heart Association, the Andrew Mellon Foundation, and the NIH, HD20676, HD37123, HD38430) KEY WORDS: prolactin, trophoblast, placenta, metrial gland |
