Estrogen and progestin receptors in mouse vaginal epithelium and fibromuscular wall

Differential regulation of the expression of estrogen, progesterone, and androgen receptors by sex steroid hormones in the vagina: immunohistochemical studies

OBJECTIVE

Significant structural changes occur in the rat vagina in response to sex steroid hormone deprivation and replacement. However, the mechanism by which these changes occur is not clearly understood and our current hypothesis is that these effects are mediated, at least in part, by the expression of sex steroid hormone receptors. The goal of this study was to assess changes in steroid hormone receptor expression and distribution in response to sex steroid hormone deprivation and administration.

METHODS

Female rats were either kept intact (controls) or ovariectomized. Ovariectomized animals were treated with vehicle, estradiol, testosterone, progesterone, or hormone combinations. Using immunohistochemistry, hormone receptor distribution was assessed in all layers of the vaginal wall.

RESULTS

After ovariectomy, estrogen receptor alpha (ERalpha) was up-regulated and progesterone receptor (PR) was down-regulated. Estradiol replacement restored these ovariectomy-induced changes, and this effect was dose-dependent. Androgen receptor (AR) expression was unaffected by ovariectomy or estradiol replacement. However, testosterone treatment resulted in increased AR density in the muscularis. Addition of either testosterone or progesterone to estradiol mitigated but did not abolish the effects of estradiol alone.

CONCLUSION

Estradiol down-regulated ERalpha and up-regulated PR expression in the vagina, suggesting this may be a mechanism to prevent continued proliferation of the epithelium by surges of estradiol during the estrous cycle.

Distribution of progesterone receptor in female mouse tissues

Two novel antibodies against the mammalian progesterone receptor (PR) were raised and characterized to study the distribution of PR and the effect of estrogen on PR expression in various female murine tissues by immunohistochemistry. There were estrogen-independent constitutive PR expressions in the smooth muscle cells of uterus, uterine blood vessels, urinary bladder, duodenum, and jejunum of ovariectomized mice. Uterine stromal cells, capsular cells of kidney and adrenal gland, and the epithelial cells of submandibular gland expressed PR constitutively. PR expression was detected in some thymic cells and the number of PR-positive thymic cells increased markedly after estrogen treatment. Estrogen induced PR expression in the epithelial cells of uterus, vagina, urethra, and skin and the stromal cells of vagina, urethra, and pancreatic ducts, as well as the smooth muscle cells of some blood vessels. These results suggest cell-specific progesterone actions in the urinary tract, skin, and gastrointestinal organs, on the immune functions, and on the regulation of local blood flow.

The germ layer origin of mouse vaginal epithelium restricts its responsiveness to mesenchymal inductors: uterine induction

The epithelium of the mammalian vagina arises from two distinct germ layers, endoderm from the urogenital sinus and mesoderm from the lower fused Müllerian ducts. While previously it has been reported that neonatal vaginal epithelium can be induced to differentiate as uterus, which normally develops from the middle portion of the Müllerian ducts, it has not been determined whether this ability is shared by both mesoderm- and endoderm-derived vaginal epithelia. To test if germ layer origin influences the ability of vaginal epithelium to undergo uterine differentiation, we have isolated sinus-derived and Müllerian-derived vaginal epithelia from newborn mice, combined them with uterine mesenchyme, and grown them for 4 weeks in female mice. Mesoderm-derived Müllerian vaginal epithelium in combination with uterine mesenchyme formed the simple columnar epithelium typical of uterus. Similar results were obtained with neonatal cervical epithelium, another mesodermal Müllerian duct derivative. On the other hand, sinus vaginal epithelium combined with uterine mesenchyme formed small cysts lined by a stratified squamous vaginal-like epithelium. This epithelium never showed evidence of cycling between the cornified and mucified states as is typically seen in vaginal epithelium combined with vaginal stroma. These results indicate that the ability of epithelium to form uterus is limited to mesoderm-derived epithelia and suggest that endoderm-derived sinus vaginal epithelium cannot undergo the typical differentiative modifications in response to the hormonal fluctuations of the estrous cycle when associated with uterine stroma.

Proliferation and differentiation of prepubertal mouse vaginal epithelial cells in vitro and the specificity of estrogen-induced growth retardation

Mouse vaginal epithelial cells were isolated from intact 21-day-old BALB/cCrgl mice and cultured in a serum-free medium (SF20: basal medium supplemented with insulin, epidermal growth factor, transferrin, and bovine serum albumin--fraction V) to examine the proliferation, differentiation, and specificity of estrogen-induced growth retardation in vitro. Histologic and ultrastructural studies showed that vaginal epithelial cells undergo differentiative changes in vitro in the absence of estrogen, and that these changes are similar to those induced in vivo by estrogen. Addition of 17 beta-estradiol inhibited cellular proliferation in a dose-dependent manner. Whereas other estrane derivatives (17 alpha-estradiol and estriol) also significantly retarded cellular proliferation, cholesterol, testosterone, and progesterone had no effect. Keoxifene, an antiestrogen, significantly reversed estrogen-induced growth inhibition, resulting in proliferation of estrogen-treated cells equivalent to that of the untreated control. The results suggest that both proliferation and differentiation of prepubertal mouse vaginal epithelial cells in vitro are estrogen-independent, and that the growth inhibition is a specific estrogen-induced response.

Serum-free culture of enriched mouse anterior and ventral prostatic epithelial cells in collagen gel

Sustained growth of mouse ventral and anterior prostatic epithelial cells embedded within collagen gel matrix was achieved in a serum-free medium composed of Dulbecco's modified Eagle's medium and Ham's F12 medium, 1:1 (vol/vol), supplemented with bovine serum albumin fraction V, epidermal growth factor, transferrin, cholera toxin, prolactin, 5 alpha-dihydrotestosterone, cortisol, putrescine, fibroblast growth factor, and a trace element mixture. Three-dimensional growth of prostatic epithelial cells occurred inside the collagen gel matrix. This serum-free medium allowed cell growth greater than sevenfold over 10 d in culture. Tissue recombination and cell culture techniques were integrated to demonstrate that cultured cells retained prostatic characteristics. Following 10 d of culture, epithelial colonies from mouse ventral and anterior prostatic epithelial cell cultures were isolated and combined with rat fetal urogenital sinus mesenchyme and grown for 4 wk under the renal capsule of intact athymic male mice. These tissue recombinants showed distinctive prostatic histologic characteristics (alveoli and ducts lined with cuboidal or columnar epithelium surrounded by stroma). When histologic sections of recombinants were stained with the Hoechst 33258, epithelial cells of mouse origin were distinguishable from stromal cells of rat origin.

Steroid binding alterations in tissue compartments of the vagina of control and neonatally diethylstilbestrol-treated adult mice

Steroid binding in both the vaginal epithelium and the vaginal fibromuscular wall (FMW) was compared in control and neonatally estrogen-treated mice. Neonatal treatment with a low dose of the estrogen diethylstilbestrol (DES) had no significant effect on adult estrogen binding within the assayed vaginal compartments; however, this treatment caused a 2-fold increase in the level of cytosolic progestin binding in the vaginal FMW over that in vehicle-treated mice. This low neonatal dose did not affect the level of progestin binding in the vaginal epithelium. In contrast, neonatal treatment with a larger dose of DES caused marked increases in cytosolic progestin binding, decreases in cytosolic estrogen binding, and increases in nuclear estrogen binding within the FMW. Furthermore, as a result of the changes in specific binding induced by the neonatal DES treatment, the degree of the estrogen binding within in each tissue shifted from a predominantly cytosolic site to a nuclear one.

Growth of mouse vaginal epithelial cells in culture: effect of sera and supplemented serum-free media

Normal mouse vaginal epithelial cells isolated from ovariectomized ca. 35-d-old BALB/cCrgl mice were grown in primary culture using collagen gel matrix and a serum-free medium composed of a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12 (D:H) medium supplemented with insulin (IN), epidermal growth factor (EGF), cholera toxin, transferrin, and bovine serum albumin V (BSA). Three-dimensional cellular outgrowths occurred inside the collagen gel matrix. The contribution of each factor to cell growth was examined by individual addition to the basic D:H medium and by individual deletion from the complete serum-free medium. When added individually, only IN promoted growth. Deletion of IN from the complete serum-free medium markedly diminished growth; deletion of EGF or BSA slightly diminished growth. When horse, fetal bovine, or chicken serum was added to the basal D:H medium, only with increasing doses of horse serum was there enhanced cell growth. The effect of 17 beta-estradiol and diethylstilbestrol on the growth of cells was also tested, using a suboptimal medium of D:H supplemented with BSA and IN, or a minimal medium supplemented with IN alone. During the 8-d time period, addition of estrogen did not enhance cell growth in either medium. To date, we have been unable to demonstrate a mitogenic effect of estrogen; rather a dose-dependent inhibition of proliferation is seen.

Growth of mouse vaginal epithelial cells in culture: functional integrity of the estrogen receptor system and failure of estrogen to induce proliferation

Normal mouse vaginal epithelial cells isolated from ovariectomized ca. 40-day-old BALB/cCrg1 mice were purified by Percoll density gradient centrifugation and grown in primary culture using a collagen gel matrix and a serum-free complete medium. During the 9-day culture period, a 6-fold increase in cell number was observed. Addition of estrogen to the medium did not enhance epithelial cell proliferation. In fact, all doses of estrogen (180 fM to 18 nM) were inhibitory, resulting in only a 3- to 4-fold increase in cell number by day 9 of culture. Continuous exposure to estradiol (1.8 nM) for 9 days in the serum-free complete medium resulted in a decrease in cytosolic estrogen receptors with associated nuclear accumulation of estrogen receptors. A corresponding increase of cytosolic progestin receptors was also observed, indicating that no qualitative modification of the estrogen receptor system had occurred. Thus, despite its effectiveness in specific product synthesis (progestin receptors), estrogen does not stimulate proliferation of vaginal cells in this culture system, but rather inhibits epithelial cell proliferation.

Restoration of normal morphology and estrogen responsiveness in cultured vaginal and uterine epithelia transplanted with stroma

We have investigated the capacity of vaginal and uterine epithelia (VE and UE) to reexpress normal morphology and hormone responsiveness following cell culture. VE and UE from adult ovariectomized mice were grown in a collagen gel matrix with serum-free medium for 7-10 days. Proliferation of these cells occurs in the absence of 17 beta-estradiol and is not stimulated by 17 beta-estradiol; the VE usually does not keratinize or stratify in vitro. Cultured VE and UE were recombined with homologous vaginal or uterine stroma (VS and US, respectively) and these recombinants were grown under the renal capsule of female hosts for 4 weeks. The epithelium of the VS + VE recombinants cycled, proliferated and stratified in response to estrogen and mucified normally in response to progesterone. The UE that was grown in vivo with cultured US also showed normal morphology and estrogen responsiveness. These changes in the UE and VE were not simply a result of return to the in vivo environment, as epithelia alone in collagen gels transplanted under the renal capsule did not survive. These results indicate that both VE and UE, which are not estrogen-dependent in vitro, reexpress their estrogen dependency and normal morphology when recombined with homologous stroma and grown in vivo. Thus, the changes these cells show when grown in culture are the result of altered conditions in vitro rather than an irreversible alteration in the cells themselves or the selection of specific subpopulations that are not mitogenically or morphologically responsive to estrogen under any condition.