Abnormalities in the reproductive system of aged mice after neonatal estradiol exposure

New frontiers of developmental endocrinology opened by researchers connecting irreversible effects of sex hormones on developing organs

In the early 1960's, at Professor Bern's laboratory, University of California, Berkeley) in the US, Takasugi discovered ovary-independent, persistent vaginal changes in mice exposed neonatally to estrogen, which resulted in vaginal cancer later in life. Reproductive abnormalities in rodents were reported as a result of perinatal exposure to various estrogenic chemicals. Ten years later, vaginal cancers were reported in young women exposed in utero to the synthetic estrogen diethylstilbestrol (DES) and this has been called the "DES syndrome". The developing organism is particularly sensitive to developmental exposure to estrogens inducing long-term changes in various organs including the reproductive organs. The molecular mechanism underlying the persistent vaginal changes induced by perinatal estrogen exposure was partly demonstrated. Persistent phosphorylation and sustained expression of EGF-like growth factors, lead to estrogen receptor α (ESR1) activation, and then persistent vaginal epithelial cell proliferation. Agents which are weakly estrogenic by postnatal criteria may have major developmental effects, especially during a critical perinatal period. The present review outlines various studies conducted by four generations of investigators all under the influence of Prof. Bern. The studies include reports of persistent changes induced by neonatal androgen exposure, analyses of estrogen responsive genes, factors determining epithelial differentiation in the Müllerian duct, ESR and growth factor signaling, and polyovular follicles in mammals. This review is then expanded to the studies on the effects of environmental estrogens on wildlife and endocrine disruption in Daphnids.

Animal model of uterine adenomyosis: is prolactin a potent inducer of adenomyosis in mice?

Uterine adenomyosis is a benign lesion but a serious disease for women, because the symptoms are characterized by abnormal bleeding, pain, cramps, and sterility. Thus elucidation of the mechanisms involved in the development of the disease would contribute to improved management and treatment and prophylaxis of this lesion. A mouse model, in which ectopic pituitary isografting is associated with an increase in the plasma level of prolactin, is useful for a rapid and frequent induction of uterine adenomyosis and can be used to study the origin of this lesion.

Reproductive abnormalities in female mice exposed neonatally to various doses of coumestrol

Female C57BL/Crgl mice were neonatally exposed to various doses of coumestrol to determine the threshold doses required for the occurrence of reproductive tract abnormalities. Newborn mice received daily subcutaneous injections of 10(-3), 10(-2), 8 X 10(-2), 10(-1), 1, 5, 25, 50, and 100 micrograms coumestrol in 0.005 ml dimethyl sulfoxide (DMSO) or DMSO alone, or received no treatment for the first 5 d of life. Some of the animals were ovariectomized at 40 d of age. Mice were killed at 20-22 mo of age. All neonatal doses of coumestrol advanced vaginal opening before that of controls. At 2 and 20-22 mo of age, doses greater than or equal to 25 micrograms consistently resulted in ovary-independent persistent vaginal cornification as judged by vaginal smears. Intact untreated and DMSO-treated control mice exhibited aging changes in the genital tract, some cervical adenosis and early cervicovaginal pegs and downgrowths, uterine cystic glandular hyperplasia, corpora lutea, and scattered areas of ovarian ceroid deposition. Intact mice receiving neonatal coumestrol exhibited cervicovaginal pegs and downgrowths (at all doses with the exception of 25 and 50 micrograms), cervical adenosis (at doses greater than or equal to 8 X 10(-2) micrograms), uterine squamous metaplasia (significant at doses greater than or equal to 50 micrograms), and a decrease in uterine cystic glandular hyperplasia (significant at doses greater than or equal to 25 micrograms). The levels of 10(-1), 5, and 100 micrograms neonatal coumestrol daily resulted in hemorrhagic follicles. An increase in ovarian ceroid deposition (significant at doses greater than or equal to 5 micrograms) was observed. At 40 d and 20-22 mo of age, corpora lutea were consistently absent from the 100-micrograms-treated animals. Most of the ovariectomized untreated and DMSO-treated control animals showed typical castrate-like morphology of the genital tract, with the majority of the control mice exhibiting uterine cystic glandular hyperplasia. Ovariectomized mice receiving coumestrol neonatally exhibited various degrees of cervicovaginal alterations: pegs and downgrowths (significant at all doses with the exception of 10(-1) micrograms), endometrial collagen deposition (significant at greater than or equal to 25 micrograms), and reduced or absent uterine glands (significant at 10(-3), and 10(-11), and at all doses greater than or equal to 5 micrograms).