EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA ISOFORMS (BETA-2 AND BETA-3) IN THE MOUSE UTERUS - ANALYSIS OF THE PERIIMPLANTATION PERIOD AND EFFECTS OF OVARIAN-STEROIDS

Expression of beta-type transforming growth factor genes (TGF-beta-2 and TGF-beta-3) in the mouse uterus during the periimplantation period and in response to an acute exposure to 17-beta-estradiol (E2) and progesterone (P4) was studied using Northern blot hybridization and/or immunocytochemistry. Polyclonal antipeptide antibodies specific for TGF-beta-2 or TGF-beta-3 were employed for immunocytochemistry. In the preimplantation uterus [days (D) 1-4 of pregnancy; day 1 = vaginal plug], immunostaining for TGF-beta-2 was observed in luminal and glandular epithelia as well as in myometrium and vascular smooth muscle. In the postimplantation period (D5-D8), TGF-beta-2 immunostaining was also detected in decidual cells. In contrast, TGF-beta-3 immunostaining was restricted to the myometrium and vascular smooth muscle throughout the periimplantation period (D1-D8). Antisense TGF-beta-2 and TGF-beta-3 RNA probes were employed for Northern blotting. Northern blot hybridization revealed four TGF-beta-2 transcripts (approximately 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 TGF-beta-2 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 TGF-beta-3 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 psuedopregnancy, 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 TGF-beta-2 and TGF-beta-3 mRNAs were examined in uteri of adult ovariectomized mice. Uterine TGF-beta-2 or TGF-beta-3 mRNA persisted in ovariectomized mice. However, an injection of E2 induced a rapid (6 h), but transient, induction (approximately 3- to 4-fold) of TGF-beta-2 mRNA. An injection of P4 had no effect on TGF-beta-2 mRNA levels, and coinjection of P4 with E2 did not antagonize the E2-stimulated transient accumulation of TGF-beta-2 mRNA. In comparison, neither an injection of E2 nor one of P4 exerted significant effects on TGF-beta-3 mRNA levels. The results of this study establish that 1) TGF-beta-2 and TGF-beta-3 genes are expressed in the periimplantation uterus; 2) epithelial, myometrial, and decidual cells are primary sites of TGF-beta-2 synthesis, whereas myometrial cells are the primary site of synthesis of TGF-beta-3 during the periimplantation period; and 3) E2 may play a role in the regulation of TGF-beta-2 mRNA levels, but an acute treatment with P4 and/or E2 does not regulate TGF-beta-3 gene expression. The distinct uterine cell type-specific expression of TGF-beta-2 and TGF-beta-3 suggests that these growth factors may have different functional roles during the periimplantation period.