Identification of transforming growth factor-β1 mRNA in virgin and pregnant rat uteri by in situ hybridization

Abstract

Transforming growth factor-β1 (TGF-β1) has major effects on hematopoietic cell proliferation, migration and function. In an effort to learn whether or not TGF-β1 might be among the cytokines that influence uterine, placental and embryonic hematopoietic cells, in situ hybridization was used to map expression of the TGF-β1 gene through gestation in the rat. In cycling uteri, hybridization signals with a biotinylated TGF-β1 antisense RNA probe were comparatively weak and were restricted to myometrium. During pregnancy, TGF-β1 mRNA appeared in specific cell lineages in an ordered temporal sequence. In early post-implantation tissues (g.d. 5–8), TGF-β1 transcripts were prominent in uterine epithelial cells, muscle and decidual cells. At g.d. 15, hybridization signals were particularly strong in uterine epithelial cells, muscle and placental trophoblast cells. At this stage, TGF-β1 mRNA was also present in uterine cells resembling macrophages and in natural killer-like (GMG) cells. Steady state levels of specific message in uteri and placentas declined at late stages of gestation (g.d. 18, 21). In rat embryos, specific transcripts were identified at g.d. 9 and were prominently displayed in various types of embryonic cells from mid-gestation onwards. The results of this study are consistent with the postulate that throughout pregnancy in the rat, TGF-β1 may, in addition to its other functions, influence the proportions, patterns of distribution and activities of maternal and fetal hematopoietic cells.