Induction of mammotroph development by a combination of epidermal growth factor, insulin, and estradiol-17β in rat pituitary tumor GH3 cells

Several reports have indicated that prolactin-secreting cells (PRL cells) are generated from growth hormone-secreting cells (GH cells). We have shown that treatment with a combination of epidermal growth factor (EGF), insulin, and estradiol-17beta (E-2) induces the appearance of PRL cells in pituitary tumor GH3 cells. The aim of the present study was to clarify the involvement of mitosis in the cytogenesis of PRL cells in rat pituitary and GH3 cells. The effects of the treatment with EGF, insulin and E-2 on DNA-replication were studied by detecting the uptake of bromodeoxyuridine (BrdU) into the nucleus. In cultured rat pituitary cells, BrdU-labeled PRL cells were observed irrespective of the hormone treatment. In GH3 cells, BrdU-Iabeled GH cells and mammosomatotrophs (MS cells) were detected; BrdU-labeled PRL cells were not detected, however, when GH3 cells were treated with BrdU for 3 hr and then immediately examined for BrdU-labeling. BrdU-Iabeled PRL cells were found only when GH3 cells treated with BrdU were allowed to grow for another 3 days. This finding suggests that during the additional 3-day culture, BrdU-labeled PRL cells were generated from BrdU-Iabeled cells other than PRL cells. These results indicate that PRL cells are transdifferentiated from GH cells or VIS cells in GH3 cells by a combined treatment with EGF, insulin and E-2, while PRL cells in rat pituitaries are able to proliferate in response to the hormone treatment. Thus, there may be two pathways for cytogenesis of PRL cells the transdifferentiation of GH cells or VIS cells, and a self-duplication of PRL cells

Gene Expression and the Physiological Role of Transforming Growth Factor-α in the Mouse Pituitary

Transforming growth factor-alpha (TGF-alpha), a member of the epidermal growth factor (EGF) family, is produced within the mouse anterior pituitaries. However, the cell types of TGF-alpha-expressing cells and the physiological roles of TGF-a within mouse pituitary glands remain unclear. The aim of the present study was to localize TGF-alpha mRNA-expressing cells, and to clarify the involvement of TGF-alpha in estrogen-induced DNA replication in mouse anterior pituitary cells. Northern blot analysis demonstrated TGF-alpha mRNA expression in adult male and female mouse anterior pituitaries. In situ hybridization analysis of the pituitaries in these mice showed that TGF-alpha mRNA-expressing cells in the anterior pituitary are round, oval, and medium-sized. TGF-alpha mRNA was colocalized in most of the growth hormone (GH) mRNA-expressing cells, while only some of the prolactin (PRL) mRNA-expressing cells. DNA replication in the anterior pituitary cells was detected by monitoring the cellular uptake of a thymidine analogue, bromodeoxyuridine (BrdU) in a primary serum-free culture system. Estradiol-17beta (E2) and TGF-alpha treatment increased the number of BrdU-labelled mammotrophs, indicating that E2 and TGF-alpha treatment stimulates the DNA replication in mammotrophs. Immunoneutralization of TGF-alpha with anti-TGF-alpha-antibodies nullified the E2-induced increase in DNA replication. RT-PCR analysis of TGF-alpha mRNA expression in ovariectomized female mice revealed that E2 increases TGF-alpha mRNA levels. These results indicate that the TGF-alpha produced primarily in the somatotrophs mediates the stimulatory effects of estrogen on the DNA replication of pituitary cells in a paracrine or autocrine manner

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

Physiological roles of Runx3 in female reproductive organs in mice

Runx3(Runtdomaintranscriptionfactor3)はRunxファミリーに属する転写因子で雌マウスにおいてRunx3 mRNAは, 卵巣や子宮に発現していた。雌のRunx3(-/-)マウスは不妊であった。Runx3(-/-)マウスは卵胞形成異常を起こしており, 無排卵であった。一方で, 排卵能および黄体形成能は有していた。以上より, Runx3は卵胞形成および排卵制御に関与していることを明らかにした。Runx3(-/-)マウスの子宮は萎縮している。子宮内膜上皮細胞では, E2依存性の細胞増殖が起こらなかった。しかし,子宮内膜間質細胞では, E2, P4存在下で正常に細胞増殖が起きた。以上より, Runx3はE2による子宮の細胞増殖に関与していることを明らかにした