ACCUMULATION OF CHROMOTROPE 2R POSITIVE CELLS IN EQUINE ENDOMETRIUM DURING EARLY-PREGNANCY AND EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA-2 (TGF-BETA-2)

Endometrial tissue from the gravid uterine horn of pregnant mares was examined by northern analysis and in situ hybridization for mRNA that hybridized to cDNA and RNA probes generated from a mouse TGF-beta 2 1. 2 kb cDNA clone. The mouse cDNA probe hybridized to characteristic TGF -beta 2 mRNA transcripts on a northern blot of total RNA isolated from horse endometrium collected at day 45 of gestation. Two major 4.0 and 3.5 kb transcripts and possibly a minor 1.6 kb transcript were observ ed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes transcribed from the same fragmen t used in northern analysis hybridized to clusters of cells scattered between endometrial glands at days 38, 40, 42, 43, 78 and 81 of gestat ion. Positive cells were absent before day 38. From day 38 to day 43 t here was marked hybridization over maternal leucocytes in the region o f the developing endometrial cups, and at later stages (day 78 and day 81) clusters of cells positive for mRNA encoding TGF-beta 2 were loca lized within the dense band of leucocytes at the periphery of the dege nerating endometrial cups. There was no hybridization to invasive or n on-invasive trophoblast or to fully differentiated endometrial cup cel ls. Approximately 90% of the TGF-beta 2 positive cells detected in the sections taken at day 78 also stained with chromotrope 2R used to det ect eosinophils and the morphology of approximately 50% of these cells was characteristic of eosinophils. These cells are known to accumulat e around endometrial cups and are therefore a possible source of mRNA encoding TGF-beta 2 in the endometrium after day 38 of gestation.