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 observed, consistent with specific hybridization to equine TGF-beta 2 mRNA. By in situ hybridization, riboprobes transcribed from the same fragment used in northern analysis hybridized to clusters of cells scattered between endometrial glands at days 38, 40, 42, 43, 78 and 81 of gestation. Positive cells were absent before day 38. From day 38 to day 43 there was marked hybridization over maternal leucocytes in the region of the developing endometrial cups, and at later stages (day 78 and day 81) clusters of cells positive for mRNA encoding TGF-beta 2 were localized within the dense band of leucocytes at the periphery of the degenerating endometrial cups. There was no hybridization to invasive or non-invasive trophoblast or to fully differentiated endometrial cup cells. Approximately 90% of the TGF-beta 2 positive cells detected in the sections taken at day 78 also stained with chromotrope 2R used to detect eosinophils and the morphology of approximately 50% of these cells was characteristic of eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)