Expression of transforming growth factor-β isoforms (β2 and β3) in the mouse uterus: Analysis of the periimplantation period and effects of ovarian steroids

Abstract

Expression of β-type transforming growth factor genes (TGFβ2 and TGFβ3) in the mouse uterus during the periimplantation period and in response to an acute exposure to 17β-estradiol (E2) and progesterone (P4) was studied using Northern blot hybridization and/or immunocytochemistry. Polyclonal antipeptide antibodies specific for TGFβ2 or TGFβ3 were employed for immunocytochemistry. In the preimplantation uterus [days (D) 1-4 of pregnancy; day 1 = vaginal plug], immunostaining for TGFβ2 was observed in luminal and glandular epithelia as well as in myometrium and vascular smooth muscle. In the postimplantation period (D5-D8), TGFβ2 immunostaining was also detected in decidual cells. In contrast, TGFβ3 immunostaining was restricted to the myometrium and vascular smooth muscle throughout the periimplantation period (D1-D8). Antisense TGFβ2 and TGFβ3 RNA probes were employed for Northern blotting. Northern blot hybridization revealed four TGFβ2 transcripts (∼6.0, 5.0, 4.0, and 3.5 kilobases) in total uterine poly(A)+ RNA on D1-D6 and in poly(A)+ RNA from the deciduum and myometrium collected on D7 and D8 of pregnancy. These TGFβ2 transcripts were also detected in isolated samples of deciduomata or myometrium obtained from D8 pseudopregnant mice in which the decidual cell reaction was induced experimentally on D4. The levels of these transcripts remained relatively constant during the periimplantation period. Northern blot analysis detected a 3.8-kilobase TGFβ3 transcript in total uterine poly(A)+ RNA on D1-D6. This transcript was detected in myometrial RNA samples on D7 and D8 of pregnancy or D8 of pseudopregnancy, but was not detected in RNA from the deciduum on D7 and D8 or in that from deciduomata on D8. The effects of ovarian steroids on TGFβ2 and TGFβ3 mRNAs were examined in uteri of adult ovariectomized mice. Uterine TGFβ2 or TGFβ3 mRNA persisted in ovariectomized mice. However, an injection of E2 induced a rapid (6 h), but transient, induction (∼3- to 4-fold) of TGFβ2 mRNA. An injection of P4 had no effect on TGFβ2 mRNA levels, and coinjection of P4 with E2 did not antagonize the E2-stimulated transient accumulation of TGFβ2 mRNA. In comparison, neither an injection of E2 nor one of P4 exerted significant effects on TGFβ3 mRNA levels. The results of this study establish that 1) TGFβ2 and TGFβ3 genes are expressed in the periimplantation uterus; 2) epithelial, myometrial, and decidual cells are primary sites of TGFβ2 synthesis, whereas myometrial cells are the primary site of synthesis of TGFβ3 during the periimplantation period; and 3) E2 may play a role in the regulation of TGFβ2 mRNA levels, but an acute treatment with P4 and/or E2 does not regulate TGFβ3 gene expression. The distinct uterine cell type-specific expression of TGFβ2 and TGFβ3 suggests that these growth factors may have different functional roles during the periimplantation period.