Epidermal Growth Factor and Transforming Growth Factor-α Stimulate the Proliferation of Mouse Uterine Stromal Cells

Growth factors produced in the uterine endometrium are considered to be involved in the proliferation of the mouse uterine stromal cells induced by estradiol-17beta (E-2) and progesterone (P). The effect of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), one of EGF-related growth factors, on the proliferation of mouse uterine stromal cells was studied in a serum-free culture. The growth of the uterine stromal cells was measured by MTT assay. EGF was found to increase the number of uterine stromal cells in a dose-dependent manner. The DNA-replicating cells were investigated using the immunocytochemical detection of bromodeoxyuridine (BrdU)-labeled cells. EGF and TGF-alpha increased the percentage of BrdU-Iabeled cells in a dose-dependent manner. Administration of the combination of E-2 (10(-9) M) and P (10(-7) M) for 2 days increased the percentage of BrdU-Iabeled cells 2.3-fold. The stimulatory effect of EGF, TGF-a and the combination of E2 and P on DNA replication in the uterine stromal cells was repressed by RG-13022 (10(-5) M, the inhibitor of the EGF receptor tyrosine kinase). RT-PCR analysis of EGF-receptor-, TGF-alpha, and EGF-mRNA was carried,out in the cultured uterine stromal cells, and revealed the expression of those mRNAs. These data supported the hypothesis that uterine endometrial stromal growth induced by sex steroids required the EGF family of ligands such as EGF and TGF-alpha, both produced in the stromal cells, acting for DNA synthesis through EGF receptors.