Cell type-specific expression of transforming growth factor-β1 in the mouse uterus during the periimplantation period

Abstract

Immunohistochemistry and in situ and Northern blot hybridization were employed to determine temporal and spatial expression of transforming growth factor-β1 (TGFβ1) in the mouse uterus during the periimplantation period. The polyclonal antisera antiLC-(1-30) and anti-CC-(1-30), raised against two different preparations of a peptide corresponding to the amino-terminal 30 amino acids of TGFβ1, were used for histochemical analyses because of their distinct staining patterns. Anti-LC shows intracellular staining, while staining by anti-CC is primarily extracellular. The colocalization of intracellular staining by anti-LC with in situ hybridization of TGFβ1 mRNA in the luminal and glandular epithelia on days 1-4 of pregnancy (day 1 = vaginal plug) indicates that the epithelial cells are the primary sites of TGFβ1 synthesis during the preimplantation period. On the other hand, staining of the extracellular matrix of the stroma by anti-CC during this period suggests an active accumulation of TGF-β1 that is synthesized in and secreted from the epithelia. While intracellular staining and accumulation of TGF-β1 mRNA in the epithelia were clearly evident on days 1-4, the extracellular staining showed temporal fluctuations. The clear extracellular staining of the stroma that was observed on day 1 was absent on day 2; moderate staining was again visualized in the stroma on day 3 and was markedly increased on day 4. On day 5 (after initiation of implantation on the evening of day 4), while the intracellular staining was restricted to the luminal epithelium and primary decidual zone (PDZ), intense extracellular staining was noted in the decidualizing stroma around the PDZ. On days 6 and 7, the PDZ was still positive for intracellular staining, but the extracellular staining was limited to the secondary decidual zone (SDZ) on day 6 and to the decidua capsularis on day 7. The extracellular staining persisted in the decidua capsularis on day 8, while the intracellular staining was diffuse in the regressing decidua. On days 7 and 8, decidua at the mesometrial pole also showed intense extracellular staining. TGFβ1 mRNA was diffusely distributed throughout the decidua on days 5-8; however, the presence of intracellular staining in the PDZ provides evidence that this zone is the primary site of TGFβ1 synthesis, while extracellular immunostaining in the SDZ and decidua capsularis is indicative of the sites of accumulation. The colocalization of mRNA with intracellular staining of the protein in the implanting embryo indicates that the embryo also synthesizes this growth factor. Northern blot hybridization of total RNA confirmed the presence of 2.4-kilobase TGFβ1 mRNA in uteri and decidua during the periimplantation period. The results suggest that TGFβ has a role in regulating interactions between the epithelium and surrounding stroma in the uterus during the preimplantation period, and between the PDZ and SDZ in the deciduum during the postimplantation period. Furthermore, because of TGFβ's role in proliferation and differentiation as well as in the formation of extracellular matrix and cell surface molecules, this TGF is likely to participate in various events of blastocyst implantation, decidualization, placentation, and embryogenesis.