Insulin-like growth factor-I as a local regulator of proliferation and differentiated function of the human trophoblast in early pregnancy.
In order to elucidate the role of insulin-like growth factor-I (IGF-I) in human placental growth and function, the effects of IGF-I on the proliferation and differentiation of trophoblasts were investigated using an organ culture system of early placental tissues. Explants of trophoblastic tissues obtained from 4-5-week or 6-12-week placentae were, respectively, cultured with or without IGF-I, in a serum-free condition. The effect of IGF-I on the proliferative activity of trophoblasts was examined by immunocytochemical techniques with a monoclonal antibody to proliferating cell nuclear antigen (PCNA), while the effect of IGF-I on the differentiated function of trophoblasts was assessed by determining the ability to secrete human chorionic gonadotropin (hCG) and human placental lactogen (hPL). In 4-5-week placentae, IGF-I and IGF-I receptor were almost exclusively localized in cytotrophoblasts and IGF-I augmented the proliferative activity of cytotrophoblasts without affecting the ability to secrete hCG and hPL. By contrast, in 6-12-week placentae, IGF-I and IGF-I receptor were localized in both cytotrophoblasts and syncytiotrophoblasts and IGF-I stimulated the secretion of hCG and hPL following the enhancement of the proliferative activity of trophoblasts. In column chromatography of the serum-free medium obtained following 5-day culture of early placental tissues, an elution peak of immunoreactive IGF-I was found in the fractions similar to the elution region of [125I]IGF-I. These findings suggest that IGF-I acts as an autocrine/paracrine factor in regulating early placental growth and function.
Maruo
T
T
Department of Obstetrics and Gynecology, Kobe University School of Medicine, Japan.
Murata
K
K
Matsuo
H
H
Samoto
T
T
Mochizuki
M
M
D002454:Cell Differentiation; D002455:Cell Division; D006063:Chorionic Gonadotropin / Q000378:metabolism; D016895:Culture Media, Serum-Free; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D009924:Organ Culture Techniques; D010928:Placental Lactogen / Q000378:metabolism; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D017526:Receptor, IGF Type 1 / Q000032:analysis; D014327:Trophoblasts / Q000737:chemistry / Q000166:cytology / Q000502:physiology*
D006063:Chorionic Gonadotropin; D016895:Culture Media, Serum-Free; D018809:Proliferating Cell Nuclear Antigen; D007334:Insulin-Like Growth Factor I; D010928:Placental Lactogen; D017526:Receptor, IGF Type 1