The possible role of hemidesmosomes in neonatally estrogen-induced selection of a permanently altered abnormal vaginal epithelium

Does sinus vaginal epithelium persist in the adult mouse vagina?

It generally is held that the murine vagina develops from the urogenital sinus and the lower portion of the Müllerian ducts and that both endodermally derived sinus epithelium and mesodermally derived Müllerian epithelium contribute to the adult vagina. We tested Müllerian and urogenital sinus-derived vaginal epithelia for their ability to differentiate in response to various hormonal conditions and compared these responses to those of the in situ vagina. Tissue recombinants were prepared with 0-day Müllerian-derived vaginal epithelium and vaginal mesenchyme. Similarly, tissue recombinants containing urogenital sinus-derived vaginal epithelium were prepared with either 0-day sinus vaginal epithelium or 16-day fetal urogenital sinus epithelium and vaginal mesenchyme. Müllerian- or sinus-derived vaginal mesenchyme was used to construct the tissue recombinants; however, the source of the mesenchyme had no influence on the results. Tissue recombinants were grafted to the renal capsule of female mice, allowed to develop for 1 month, and exposed to various hormonal treatments. In diethylstilbestrol-treated hosts, all tissue recombinants regardless of the source of the epithelium were lined by a cornified epithelium. In contrast, only in tissue recombinants containing mesodermally derived Müllerian vaginal epithelium did the epithelium mucify in response to progesterone plus estrogen or become atrophic in ovariectomized hosts. These are the same epithelial modifications seen in the hosts' vagina. Tissue recombinants containing endodermally derived urogenital sinus epithelium or sinus vaginal epithelium and grafts of intact urogenital sinus maintained a stratified squamous noncornified epithelium in both ovariectomized and progesterone plus estrogen-treated hosts. Furthermore, in tissue recombinants containing Müllerian vaginal epithelium and vaginal mesenchyme, estrogen induced a slightly higher epithelial labeling index than in tissue recombinants containing urogenital sinus epithelium or sinus vaginal epithelium. The epithelial labeling index was the same regardless of the source of the vaginal mesenchyme. These results indicate that Müllerian-derived and sinus-derived vaginal epithelia are not equivalent and suggest that Müllerian vaginal epithelium displaces sinus vaginal epithelium during postnatal development. The replacement may result in part from a slight but consistently higher proliferation rate in Müllerian versus sinus vaginal epithelium.

Origin of permanently altered epithelial cells of the vagina in neonatally estrogen-treated mice

In adult mice, neonatal injections of estrogen induce persistent, estrogen-independent cornification of the vaginal epithelium. Since the occurrence of nodules composed of affected epithelial cells (B cells) is a prodromic phenomenon of the irreversible vaginal alterations, the relationship between the occurrence of B-cell nodules and the time of DNA synthesis in the vaginal epithelial cells was examined by means of the techniques of serial mapping and autoradiography. B-cell nodules appeared in the epithelium of mullerian vagina 3-5 days after the initiation of neonatal estrogen treatment, without spatial continuity to cuboidal epithelial cells of the sinus vagina. The time of DNA synthesis was different in B cells from that in both columnar mullerian and cuboidal sinus cells, suggesting that the mother cells of B cells might be a population of still unidentified, undifferentiated cells.

The importance of stroma in morphogenesis and functional activity of urogenital epithelium

Urogenital morphogenesis and cytodifferentiation are presented in the context of the epithelial-stromal interaction. The essential role of stroma in the processes is reviewed.

Physiological mechanisms of diethylstilbestrol organotropic carcinogenesis

Treatment of pregnant women with diethylstilbestrol (DES) during pregnancy has been demonstrated to be associated with an increased risk in the female offspring for development of an otherwise very rare type of malignancy: clear-cell adenocarcinoma of the vagina and cervix. The present knowledge about this association is reviewed. In experimental animals, many different types of malignancy can be induced by DES administered in large doses and during long periods. For the human situation there are as yet no indications that exposure to DES during fetal life has resulted in any generally increased incidence of malignant tumors. By injecting neonatal mice with DES for the first five days after birth, histologically malignant changes develope in the uterine cervix of the animals when more than one year old. A comparison is made between this animal model and development of tumors in the human female offspring of DES treated mothers. In the female mice, neonatal DES treatment results in a disturbed epithelial differentiation process in the upper part of the vagina and the uterine cervix, a disturbed development of the hypothalamic-pituitary gland control system as well as a disturbance in the normal development of the lymphoid system. The abnormal epithelial differentiation process results in development of adenosis and within these areas the malignant changes later appear. We do no know whether adenosis is a pre-cancerous condition or not, in the meaning that it contains dormant malignant cells. Other factors could act upon adenosis to result in cancer. The reasons for DES being called a "carcinogen" are reviewed. The possibility for factors in the environment acting as potential transplacental carcinogens in the human fetus should not be excluded.