Mitogenic action of oestradiol-17 beta on human myometrial and endometrial cells in long-term tissue cultures

In vitro models of the human endometrium: evolution and application for women's health

The endometrium is the inner lining of the uterus that undergoes complex regeneration and differentiation during the human menstrual cycle. The process of endometrial shedding, regeneration, and differentiation is driven by ovarian steroid hormones and prepares the endometrium and intrauterine environment for embryo implantation and pregnancy establishment. Endometrial glands and their secretions are essential for pregnancy establishment, and cross talk between the glandular epithelium and stromal cells appears vital for decidualization and placental development. Despite being crucial, the biology of the human endometrium during pregnancy establishment and most of pregnancy is incomplete, given the ethical and practical limitations of obtaining and studying endometrium from pregnant women. As such, in vitro models of the human endometrium are required to fill significant gaps in understanding endometrial biology. This review is focused on the evolution and development of in vitro three-dimensional models of the human endometrium and provides insight into the challenges and promises of those models to improve women's reproductive health.

In-vitro construction of endometrial-like epithelium using CD146+ mesenchymal cells derived from human endometrium

Endometrial CD146⁺ cells were purified, using magnetic activated cell sorting, and then embedded and cultured in a collagen-matrigel scaffold on top of myometrial smooth muscle cells for 10 days. At the end of culture period, the differentiation and formation of the epithelial-like cells were confirmed by morphological and ultrastructural evaluations, and analysis by reverse transcription polymerase chain reaction of the specific expression of genes: osteopontin (SPP1), matrix metalloproteinase 2, zonula occludens 1, laminin alpha 2 and collagen type IV; and by western blotting of CD9 protein. The results showed that the human endometrial mesenchymal CD146⁺ cells were able to produce endometrial glandular tube-like structures in vitro. Ultrastructural observation revealed some projections on the apical surfaces, appearance of basal lamina-like structures on the basal surface, and tight junctions and desmosomes on the lateral surfaces of the epithelial-like cells. The expression of studied genes at RNA level and CD9 at protein level confirmed the formation of endometrial epithelial-like cells. This culture system may have potential applications in cell therapy and in studies on human embryo implantation.

Etiology and pathogenesis of uterine leiomyomas: a review

Uterine leiomyomas, or fibroids, represent a major public health problem. It is believed that these tumors develop in the majority of American women and become symptomatic in one-third of these women. They are the most frequent indication for hysterectomy in the United States. Although the initiator or initiators of fibroids are unknown, several predisposing factors have been identified, including age (late reproductive years), African-American ethnicity, nulliparity, and obesity. Nonrandom cytogenetic abnormalities have been found in about 40% of tumors examined. Estrogen and progesterone are recognized as promoters of tumor growth, and the potential role of environmental estrogens has only recently been explored. Growth factors with mitogenic activity, such as transforming growth factor- (subscript)3(/subscript), basic fibroblast growth factor, epidermal growth factor, and insulin-like growth factor-I, are elevated in fibroids and may be the effectors of estrogen and progesterone promotion. These data offer clues to the etiology and pathogenesis of this common condition, which we have analyzed and summarized in this review.

Genistein and daidzein modulate in vitro rat uterine contractile activity

The present study investigated the effect of genistein, daidzein and estradiol on in vitro rat uterine responsiveness to oxytocin (OT) and PGF(2)alpha or luprostiol (L). In a first experiment, animals were either sham-operated (SH; n=5), or ovariectomized (OVX; n=20) and orally treated for three months with either genistein (G; n=5; 10 microg/g BW/d) or daidzein (D; n=5; 10 microg/g BW/d) or 17 alpha-ethinylestradiol (E; n=5; 23 microg/kg BW/d) or untreated (OVX; n=5). At necropsy, the basal uterine tension was lower in OVX, G and D than in SH, the highest value being measured in E. Oxytocin (10(-12); 10(-11) M) or PGF(2)alpha (10(-12); 10(-9) M) induced an increase in SH, but not in OVX, E and G. In D, only the highest doses were efficient. In a second experiment, 20 intact animals were s.c. injected with either genistein (G; n=5; 10 microg/g BW) or daidzein (D; n=5; 10 microg/g BW) or estradiol benzoate (E; n=5; 23 microg/kg BW) or vehicle (C: controls; n=5), and killed 24 h later. In C and E, OT (10(-15) to 10(-10) M) or L (10(-12) to 10(-7) M) stimulated uterine contractile activity in a dose-dependent manner until a maximal level. On the opposite, in G and D, contractile agents (except the highest luprostiol doses) did not stimulate myometrium contractions. Moreover, radioligand binding assays showed that genistein or daidzein inhibited the specific binding of [(3)H] estradiol to the calf uterus estrogen receptor (ER). Therefore, it could be postulated that both genistein and daidzein might bind to the rat uterus ER, inducing either anti-estrogenic or very weak estrogenic effects (depending on the experimental conditions) on in vitro uterine responsiveness to OT and PGF(2)alpha or luprostiol.

Paracrine regulation of menstruation

Endometrial proliferation, secretion, vascular neoformation and modification to shedding is under direct and/or indirect control of steroid hormones. The progressive modification of the endometrial architecture is due to its growth and differentiation. The new tissue regenerates monthly from a 2-5 mm to a 12-18 mm of complex tissue until it sheds under a co-ordinated network of bioactive molecules produced and activated during the menstrual cycle. The steroid hormones, the HLA-DR and integrin molecules, the intense production of several proteins, the vascular damage, and the disconnection of cell-cell and cell-matrix interaction are participating in both the endometrial preparation for embryonic implantation and the shedding and bleeding of the tissue itself. Menstruation is a process associated with damage to the epithelium, endothelium and extracellular matrix, ending on controlled bleeding, tissue dissolution and repair. Endometrial proteinases and tissue factor (TF) contribute to systemic factors to control the mechanisms of regulation of tissue dissolution, tissue shedding, and vascular bleeding during menstruation.

Expression and regulation of insulin-like growth factor binding protein-1 in the rat uterus throughout estrous cycle

In previous studies, we have demonstrated that IGF-1 and IGF-1 receptor are expressed in rat uterus and that the expression is up-regulated by estrogen. The present study examines the expression and regulation of IGFBP-1 and IGFBP-3 in rat uterus throughout the estrous cycle. The stage of the estrous cycle in 16 mature female rats was determined by microscopic examination of daily prepared vaginal smears. Rat uteri were then used for RNA extraction. The results of the Northern blot analysis demonstrate that uterine cells express both IGFBP-1 and IGFBP-3 mRNA throughout the estrous cycle. When autoradiograms were quantitated by a densitometry, a significant reduction in expression of IGFBP-1 mRNA was found in uteri at stages of proestrous and estrous relative to that in diestrus. Although the level of IGFBP-3 mRNA varied in uteri throughout estrous cycle but this variation was not statistically significant. The lowest expression of IGFBP-1 (8.5% relative to diestrus, p < 0.05, n = 4) and IGFBP-3 (71% relative to diestrus) was found in the uteri prepared from rats at the stage of proestrus, while the highest expression of IGFBP-1 and IGFBP-3 was observed in the uteri obtained from rats at the stage of diestrus and metestrus, respectively. Using anti-rabbit IGFBP-1 antibody raised against an oligo-synthetic IGFBP-1 peptide, immunohistochemical staining demonstrates the presence of IGFBP-1 in the luminal and stromal glandular epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of growth factors in the human endometrium during aging

The aim of this study was to investigate the possible role of epidermal growth factor (EGF) and of insulin-like growth factor-I (IGF-I) in physiological and pathological changes of the endometrial tissue during aging. Thirty-four patients undergoing hysterectomy were divided into three groups: (A) premenopausal women with regular menses, (B) pre-menopausal women with irregular bleeding and (C) post-menopausal women. Endometrial samples were collected after the removal of uterus and were used for immunohistochemical evaluation of EGF, EGF receptor (EGFr) and IGF-I and also for Northern blot analysis of IGF-I gene expression. Plasma levels of 17 beta-oestradiol (E2), D4-androstenedione (D4-A) and oestrone (E1) were also assayed. The immunohistochemical scores (HSCORES) for EGF, EGFr and IGF-I were significantly higher in groups A and B than in group C. Independently from the menstrual history, significantly higher HSCORES of EGF, EGFr and IGF-I were present in hyperplastic endometrium than in those which were proliferative and atrophic. Moreover, IGF-I mRNA expression was observed in all pre-menopausal women, whereas only 1 post-menopausal women with hyperplastic endometrium showed detectable RNA encoding for IGF-I. Higher levels of D4-A were also significantly correlated (P < 0.05) with higher HSCORES of EGF, EGFr and IGF-I. Our results suggest that the above mentioned growth factors could act as mediators of oestrogens on the endometrial functional activity.

The concentration of estrogen receptors in rabbit uterine myocytes decreases in culture

OBJECTIVE

The purpose of this study was to determine whether the concentration of estrogen receptors in cultured myocytes is preserved after dispersion.

STUDY DESIGN

Primary myocytes were prepared from rabbit myometrium by collagenase dispersion after removing the endometrium and were isolated with Percoll density gradients. The cells were assayed for estrogen receptor concentration at intervals after dispersion by means of a whole-cell binding assay. Unpaired t test was used for comparisons.

RESULTS

The concentration of estrogen receptors on the first day after dispersion was 12,058 +/- 1096 sites per cell (mean +/- SEM) and decreased to 4389 +/- 1223 site per cell within 9 to 14 days after dispersion (63% decline, p < 0.001). A similar decrease was observed when 2 nmol/L estradiol was present in the medium.

CONCLUSION

The concentration of estrogen receptors in isolated rabbit uterine myocytes decreases after dispersion. This may partly explain the difficulty of demonstrating in vitro estrogen effects on myocytes, which are well established in vivo.

Transfected endometrial cultured cells: a system to study gene-regulation by estrogens

Glandular epithelial (GE) and stromal cells were isolated from guinea-pig endometrium, cultured and subcultured separately. At the end of subculture, the purity of each cell population was higher than 95% and cells displayed a high level of estrogen receptors. Calcium phosphate transfection conditions were defined using a control plasmid containing the bacterial CAT gene driven by viral promoter and enhancer sequences. Transfection experiments were performed with other plasmids in which CAT gene was linked to different estrogen response elements (EREs) derived from those of vitellogenin genes. CAT activity was significantly increased by estradiol-17 beta treatment only when GE or stromal cells were transfected with plasmids containing EREs previously reported as functional EREs in other cell types. This induction was abolished by ICI 164,384 diethylstilbestrol was as effective as estradiol-17 beta for CAT induction and estradiol-17 alpha was ineffective. Transiently transfected endometrial cells in subculture are a suitable system to study the estrogen effect on gene regulatory elements.

Growth, morphologic, and invasive characteristics of early and late passages of a human endometrial carcinoma cell line (RL95-2)

Two in vitro passages of a human endometrial adenocarcinoma continuous cell line (RL95-2), an early (subcultured less than 30 times) and a late passage (subcultured greater than 200 times) have provided an interesting model to study the growth, morphologic, and invasive properties of endometrial tumors. The early passage, which has been shown to be estrogen-receptor positive, has characteristics closely resembling a primary tumor, whereas the estrogen receptor negative late passage exhibits several features of the metastatic phenotype. Compared to the early passage cells, the late passage cells were less serum dependent, formed foci, demonstrated a faster rate of growth (due to their shorter doubling times), and attained higher saturation densities. The late passage cells also displayed an altered morphology which was accompanied by alterations in the distribution of F-actin. Even though early and late passages showed similar invasive potential in an in vitro invasion assay, the late passage cells, by virtue of their several transformed characteristics, maintain distinctive properties compared with their early passage counterparts.

Insulin-like growth factor-I gene expression during development and estrous cycle in the rat uterus

The ontogeny and estrous cycle-dependent variation of insulin-like growth factor-I (IGF-I) gene expression was analyzed in the rat uterus. RNA extracted from rat uteri contained transcripts with estimated sizes of 7.0, 1.7, and 1.2-0.8 kb that were recognized by a 32P-labelled mouse IGF-I RNA probe. A solution hybridization RNase protection assay was used to measure the abundance of IGF-I mRNAs in uteri from rats of different ages. The highest levels were found in adult rats (p less than 0.01). The levels of IGF-I transcripts changed markedly during the estrous cycle with the highest levels at proestrus (p less than 0.01). There was an 8-fold increase in the abundance of IGF-I mRNA between diestrus-2 and proestrus. The corresponding livers had no significant variation of IGF-I gene expression during the estrous cycle, demonstrating a tissue-specific regulation of the IGF-I gene. The time and dose dependency of estrogen regulation of IGF-I gene expression was studied in hypophysectomized rats. The levels of IGF-I mRNA in the uterus decreased after hypophysectomy. A single s.c. injection of estradiol significantly increased the levels of IGF-I transcripts after 3 h (p less than 0.01). A low dose of estradiol (0.1 micrograms/100 g) increased the levels of IGF-I transcripts but progesterone in higher doses (5 micrograms/100 g) was without effect, indicating that the effect was specific for estradiol. However, the present study provides no information regarding whether this regulation is at the level of transcription or mRNA stability.(ABSTRACT TRUNCATED AT 250 WORDS)

Estrogen induction of insulin-like growth factors and myc proto-oncogene expression in the uterus

In contrast to the effects observed in vivo, isolated uterine cells cultured in vitro demonstrate little proliferative response to estrogens. Estrogen induced uterine proliferation involves a carefully orchestrated, sequential activation of genes which encode a variety of biologically active molecules. These include nuclear transcription factors, growth factors and growth factor receptors. Expression of these proteins serve to amplify the effect of estrogen through cellular, autocrine and paracrine mechanisms. In this review the effects of estrogen on uterine expression of the myc family of oncogenes and the insulin-like growth factors are discussed.

Regulation of epidermal growth factor and insulin-like growth factor I receptors by estradiol and progesterone in normal and neoplastic endometrial cell cultures

Growth factors are polypeptides which regulate cell proliferation through binding to specific receptor proteins. Normal and neoplastic human endometrium have been shown to express epidermal growth factor (EGF) and insulin-like growth factor I (IGF-1) receptors. Endometrial cell cultures were used to test modulation of EGF and IGF-1 receptors in response to steroid hormones. Endometrial gland and stroma cells were separated by enzymatic dispersion and were incubated in medium containing estradiol (10, 100, or 1000 pg/ml) or progesterone (1, 10, or 100 ng/ml) followed by radioligand assays. Normal endometrial cultures (n = 6) treated with estradiol demonstrated 40% less EGF binding than control cultures (P less than 0.05), while IGF-1 binding was unaffected. Stromal cells treated identically decreased in only one treatment group. Progesterone treatment stimulated a significant increase in EGF and IGF-1 receptors in gland cultures. Cultures derived from adenocarcinoma (n = 2) demonstrated decreased EGF binding compared with normal endometrium (P less than 0.05). Carcinoma cells treated with progesterone resulted in a dose-dependent increase in EGF binding over control (P less than 0.05). These data illustrate effects of steroid hormones upon growth factor receptors in human endometrium, and suggest involvement of growth factors in the regulation of normal and neoplastic endometrial growth.

Gland formation from human endometrial epithelial cells in vitro

We have developed methods for the culture of human endometrial glandular epithelia in vitro. The culture medium is serum-free and is used in combination with Matrigel, an extracellular matrix material applied as a coating on cell culture plates. Cell growth begins as a monolayer, but the cells subsequently form glandular or organoid structures. The glands are composed of polar columnar cells facing a central lumen, which is enclosed by the apical surfaces of cells displaying numerous microvilli and sealed by tight junction complexes. The ability to study in vitro the complex process of glandular morphogenesis represents an important new tool in cell biology which may be used to investigate growth regulation, hormone production and dependency, and cellular recognition and interactions. Ultimately, these characteristics may be applied to study the alterations of glandular epithelia associated with neoplasia.

Epidermal growth factor binding in rat uterus during the peri-implantation period

The profile of epidermal growth factor (EGF) binding to uterine membranes of rats on Day 1 through Day 7 of pregnancy was studied. The binding was lowest on Day 1 and increased gradually through the pre- and postimplantation periods. Binding affinity of the Day 7 uterine membranes was considerably higher than that of the Day 1. Apparent affinity constants (Ka) of Day 1 and Day 7 membranes were 0.29 X 10(-8) M and 1.03 X 10(-8) M respectively. To our knowledge, this is the first report of the modulation of EGF binding to uterine membranes by progesterone-estrogen interaction during early pregnancy.

The effect of estradiol on human myelomonocytic cells. II. Mechanism of enhancing activity of colony formation

Elevated proportions of monocytes have previously been found in the blood of healthy women during the ovulation period as well as in other conditions associated with increased blood estradiol (E2). This phenomenon was explained, in part, by an augmenting effect which physiological concentrations of E2 may have on the development of granulocyte-macrophage (GM) colonies derived from normal peripheral blood mononuclear cells. To analyze this effect, we tested possible alternatives for the interaction between E2, colony-stimulating factor (CSF) and GM colony progenitor cells. E2 was found not to interact synergistically with CSF, but pre-treatment of the progenitor cells with E2 resulted in higher numbers of colonies in response to CSF. Moreover, E2 did not induce higher secretion of CSF but treatment with anti-CSF antibodies abolished the enhancing effect of E2. Based on these results, we suggest that the augmenting effect of E2 on GM colony formation is mediated by inducing the colony precursor cells to be more responsive to CSF. These findings may help to elucidate some of the complex relationships between estrogens, immune responses and hemopoiesis.

Morphologically stable epithelial vesicles cultured from normal human endometrium in defined media

Epithelium from normal human endometrium was cultured as morphologically stable vesicular structures in a defined, hormone-supplemented PFMR-4 medium. The structures consisted of a single layer of polarized epithelial cells with the apical surface facing the external culture medium, and the basal surface resting on a well-defined basal lamina adjacent to the internal lumen. Vesicles were shown to retain their viability for up to 3 mo. in culture, to actively synthesize DNA after being cultured for over a month in a defined medium, and to respond to steroid hormones. When embedded within a collagen gel, the vesicles reversed their epithelial polarity and formed branching, pseudoglandular structures. It was concluded that the three-dimensional shape of the epithelial vesicles had a critical role to play in their morphological stability, nutrient requirement, and hormone sensitivity.

The effect of estradiol on human myelomonocytic cells. 1. Enhancement of colony formation

Cyclic changes were observed in the content of blood monocytes during the menstrual cycle of normal women. Elevated blood monocytes were found during the ovulation period as well as in other conditions which are associated with increased blood estradiol (E2). To understand the possible association between E2 and monocytosis, we analysed the in vitro effect of E2 on the development of myelomonocytic colonies in culture. E2 in physiological concentrations was found to increase the number of colonies developed from peripheral blood mononuclear cells (PBM) of both females and males. The optimal concentration for the augmenting effect on males' PBM was lower than that for females. Mononuclear cells derived from cord blood, which yielded much higher numbers of colonies than adult PBM, also responded to the stimulatory effect of E2. Estrone and estriol were less effective than E2 in adult PBM. In contrast, progesterone, diethylstilbestrol and testosterone did not affect the number of colonies at the range of physiological concentrations tested. The anti-estrogen Tamoxifen did not inhibit the stimulatory effect of E2. The augmenting effect of E2 on monomyelocytic colony formation may explain at least in part the increase in blood monocyte content of women with high E2 as well as other phenomena of macrophage and granulocyte changes associated with the menstrual cycle.

Ultrastructural study of cultured smooth muscle cells from uterine leiomyoma and myometrium under the influence of sex steroids

Upon the hypothesis that the differentiation or development of smooth muscle cells in both myometrium and leiomyomas may be under the regulation of sex steroids, myometrial and myoma cells were cultured in the presence of sex steroids and their morphological changes were studied ultrastructurally. The cells from the explants of both leiomyoma and myometrium at the 14th day in either control or E (10(-8) M 17-beta-estradiol)-added medium showed extremely well-developed cytoplasmic organelles with few filaments located at the marginal portion of the cytoplasm. These ultrastructural features resembled those of a dedifferentiated stage of smooth muscle cells in vitro. At the 21st day, these cells showed a moderate number of cytoplasmic filaments with dense bodies. These ultrastructural features resembled those of a redifferentiated stage of smooth muscle cells in vitro. In both E- and P (10(-7) M progesterone)-added medium, the cultured smooth muscle cells from both leiomyoma and myometrium showed an increased number of myofilaments with dense bodies even at the 14th day to the 21st day of culture in comparison to the cells either in control or estrogen-added medium. Therefore, the cultured smooth muscle cells in the medium with E and P lacked their dedifferentiated phase in vitro and/or the differentiation or maintenance of their filaments might be under the influence of both estrogen and progesterone. On the observation that the cultured smooth muscle cells from both leiomyoma and myometrium showed very similar ultrastructural changes under the influence of sex steroids, it was suggested that leiomyoma may have the same progenitor cells as myometrium.

Collagen gel culture system and analysis of estrogen effects on mammary carcinogenesis

The results obtained to date from studies dealing with the role of hormones, including estrogen, on growth of mammary epithelial cells inside the collagen gel are described. The collagen gel matrix culture system appears to be a suitable system to obtain in vivo-like effects of hormones on mammary cell in vitro. The results thus far indicate that prolactin along with progesterone or cortisol can stimulate mammary cell proliferation. Thus far, estrogen has not been found to be mitogenic in our in vitro system.

Establishment and morphologic characterization of normal human endometrium in vitro

Tissue culture offers a model system with which to study the endocrine-mediated growth, differentiation, and metabolic activities of the endometrium. We have established and continue to maintain monolayer cultures of normal human endometrial epithelial cells from each phase of the menstrual cycle. At present, eight proliferative, two secretory, and two menstrual phase cultures have been established. These have been passed at least three times. One proliferative phase culture has been growing for 18 mo, and passed 10 times. Colonies of epithelioid cells as well as single cells appear in the cultures within 2 to 8 h of initial culture and maintain this appearance throughout long-term growth. The cells are periodic acid Schiff positive for carbohydrates and positive for keratin, an immunochemical marker for epithelial tissues. Studies comparing the ultrastructure of the cultures with fresh endometrial tissue revealed morphologic features common to both, including prominent nucleoli, Golgi, mitochondria-rough endoplasmic reticulum complexes, and abundant glycogen. The cells are not tumorigenic in the nude mouse and do not form colonies on soft agarose, confirming the nonneoplastic identity of the cells.

Enzymatic dissociation of ovarian and uterine tissues

A method is described for the preparation of high yields of viable, dissociated cells from porcine theca interna and corpus luteum and from human and bovine endometrium. The tissues were dissociated by incubation at 37 degrees C in a mixture of 0.5% collagenase, 0.1% hyaluronidase and 0.1% pronase in balanced salt solution containing 1% chicken serum. This procedure consistently provided high yields of structurally and metabolically intact dispersed cells after a digestion period of 60 min. The procedure is superior to methods previously reported in the literature.

Characterization of a new human endometrial carcinoma (RL95-2) established in tissue culture

A new human endometrial cell line, RL95-2, derived from a Grade 2 moderately differentiated adenosquamous carcinoma of the endometrium has been passaged successfully in cell culture for more than 2 yr. The cells are characteristically epithelioid with well-defined junctional complexes, tonofilaments, filopodialike extensions, and surface microvilli. Nuclei are large, irregular, and invaginated frequently with multiple, prominent, lamellar nucleoli. The cells have a log phase doubling time of 22 to 34 h followed by continued growth at a reduced rate with no apparent plateau phase. They exhibit a strong tendency for piling up as well as for the formation of glandlike dome structures. Karyotypically the line is trisomic 8 (47,XX,+8) and has an 8% frequency of polyploidization. Both cytoplasmic and nuclear estrogen receptors are present. Antihuman alpha-keratin characterizes the cell line as epithelial, nonstromal. The RL95-2 cell line may provide a useful in vitro system for the investigation of the endocrine regulation of endometrial neoplasia.

Morphology and growth potential of stromal cell cultures derived from human endometrium

Propagable cell cultures derived from human endometrial tissue were determined to contain cells predominantly of stromal cell origin based on their morphologic resemblance to endometrial stromal cells. These features included nexi, solitary cilia, and predecidual cytology. In addition to morphology the cell cultures retained a normal karyotype and responded to steroid hormones as evidenced by cellular aggregation. The stromal cells were evaluated for a variety of characteristics associated with transformed cells and seemed to be biologically normal without neoplastic phenotypes. Growth potential of the stromal cell cultures was also characterized in normal maintenance medium, in nutritionally depleted medium with reduced levels of calcium or serum, and in medium with increased levels of serum. The prolonged survival of the stromal cells in vitro coupled with the retention of in vivo characteristics and an absence of neoplastic phenotype provides a human cell system that is amenable to a variety of long-term experimental analyses.

Monolayer culture of human endometrium: methods of culture and identification of cell types

Monolayer cultures can be established from human endometrial tissue after enzymatic dispersal into isolated glands or single cells. Three cell types that have distinct morphology by light and electron microscopy are observed in the resulting primary cultures. One cell type, an elongated spindle cell, is similar in appearance to fibroblasts derived from other tissues. A second cell type forms colonies of tightly cohesive cells, ranging in shape from oval to polygonal. These cells have typical organelles and junctional complexes characteristic of epithelial cells from the endometrium. The third cell type assumes a pavement-like appearance composed of polygonal cells when viewed by phase contrast microscopy, but lacks distinctive ultrastructural features of epithelial cells. These cells in culture resemble the endometrial stromal cell, the predominant cell type of the human endometrium in vivo. The epithelial cell does not survive subculturing but the other two cell types can be passaged through several generations and can be stored in liquid nitrogen and subsequently returned to culture.

Growth characteristics of primary cultures of stromal cells from human endometrium

The growth rate of stromal cells derived from 23 specimens of human endometrial tissue taken at various phases of the cycle was measured during the first seven days of primary culture. The stromal cells were found to differ radically in their ability to grow in culture according to the phase of the cycle at which the tissue was obtained. Early and mid proliferative stromal cells were capable of proliferation but that capacity was lost in late proliferative tissue. Growth at significant rates reappeared at days 21--22 and persisted in cells from late secretory tissue. Following plating, a 2--4 day lag period preceded proliferation of all but the most rapidly growing cultures. Subcultures showed a shorter lag period and faster maximal growth rate than the primary cultures from which they were derived. Estradiol, 10(-9) M. inhibition stromal cell growth in primary culture and this effect was prevented by 10(-8) M progesterone. These observations indicate that proliferative characteristics of stromal cells in primary culture are strongly influenced by the hormonal environment of the endometrium at the time of biopsy.

Role of steroid hormones and prostaglandins in the regulation of DNA synthesis by decidual cells in culture

The effect of oestrogen and progesterone on prostaglandin synthesis and on DNA synthesis by rat decidual cells was studied in a culture system. The cells were explanted from deciduoma either during the proliferation phase (namely on the 5th day of leukocytic smear, Day L5:"L5 cells") or during the maintenance phase ("L8 cells") and examined on the second day of culture. Oestradiol-17 beta (7 X 10(-11) M) and progesterone (6 X 10(-8) M) significantly inhibited accumulation of PGE by cells explanted on Day L5: L8-cell cultures showed no significant response to oestradiol and the progesterone effect was markedly reduced. Progesterone stimulated [3H]thymidine incorporation into cells explanted on Day L5, but had no effect on L8-cultures. Other inhibitors of PG synthesis, namely cortisol, flufenamic acid and indomethacin, also had a stimulatory effect on DNA synthesis by L5 cells. PGE2 (5-10 micrograms/ml) inhibited DNA synthesis in control, indomethacin-treated and progesterone-treated L5-cell cultures, suggesting that the progesterone-induced stimulation of DNA synthesis may be in part be due to its inhibitory effect on PGE accumulation by decidual cells. The possibility is discussed that during the proliferation phase of decidual development in vivo, the rate of DNA synthesis may be influenced by steroid-induced changes in PGE content of the tissue.

Progesterone-induced glycogen accumulation in human endometrium during organ culture

An organ culture system was used to evaluate the response of human proliferative endometrium to progesterone stimulation. The glycogen content of proliferative tissue was increased as much as thirteenfold during organ culture in media containing progesterone. The steroid-induced increase in tissue glycogen was detectable after 16 hours and reached a maximum at 48 and 72 hours of culture. Progesterone induced a significant increase in glycogen at a media concentration of 1.6 x 10(-8)M and a maximal increase at 3.2 x 10(-7) to 3.2 x 10(-6)M. At higher media concentrations of progesterone (1.6 x 10(-5)M), glycogen levels failed to reach the maximum obtainable. The extent of the response correlated poorly with the initial glycogen content of the tissue and not at all with the initial content of high-affinity progesterone-binding sites in cytosol. Addition of estradiol-17 beta to medium (10(-10)M to 10(-7)) has no effect on the progesterone-induced increase in tissue glycogen. Delaying the addition of progesterone to the cultures for 24 hours resulted in a diminished glycogen response; the reduced response may be related to a rapid decrease in high-affinity progesterone-binding sites as measured in cytosol prepared from tissues cultured in the absence of progesterone. High-affinity progesterone-binding sites in endometrial cytosol were found to decrease rapidly during the first 24 hours of culture. The addition of cycloheximide or actinomycin D to the culture media inhibited the increase in tissue glycogen caused by progesterone. These results demonstrate that progesterone can induce an in vitro response in human proliferative endometrium similar to that seen in vivo. The response of the endometrium is reproducible and allows for comparisons between grouped data obtained by using tissues from several different donors.

Normal human endometrium in cell culture. II. A microspectrophotometric study of polyploid nuclei in short-term primary epithelial cultures

The growth of short-term primary cultures of endometrial epithelium has been studied using Feulgen microspectrophotometry. A gradual increase in the number of polyploid nuclei up to 64C has been observed and is associated with a decline in the growth capacity of the cultures. The specific mechanism(s) of this polyploidization is not known.

Promotion of human adipocyte precursor replication by 17beta-estradiol in culture

The influence of 17beta-estradiol and 17alpha-estradiol on adult human omental adipocyte precursors grown in a propagating culture system was studied. Cells were grown in subculture in the presence or absence of hormone. 17beta-estradiol resulted in significant promotion of adipocyte precursor replication, as determined by cell counting and incorporation of radioactive thymidine into DNA. The hormone stimulated cell multiplication in the concentration range 0.5--500 ng/ml growth medium. The highest level tested was 500 ng/ml. The maximal effects were obtained at 50 ng/ml (P less than 0.001 by paired t test, 48 h after hormone addition). All 10 cell strains (five were derived from men and five from women) that were tested responded similarly to the hormone. 17beta-estradiol did not affect cell size. 17alpha-estradiol did not promote the replication of adipocyte precursors, nor did it influence cell size. Thus, 17beta-estradiol, which is the active isomer in known target tissues, stimulates the multiplication of human adipocyte precursors in culture.

Normal human endometrium in cell culture. I. Separation and characterization of epithelial and stromal components in vitro

Separation of human endometrium into its epithelial and stromal components has been achieved through collagenase digestion and has permitted a study of these two cell populations under specific experimental culture conditions. The stromal cell populations showed a progesterone response, were easily handled in culture, and displayed a limited in vitro life span typical of human diploid fibroblasts. In contrast, epithelium only survived in short-term primary culture and showed no clear hormone response. High-density epithelial cultures remained viable for longer periods in culture. Comparisons between resurfacing endometrial epithelial cells in vivo and epithelial cells migrating from explants in vitro suggested that this initial epithelial migration in vitro was the counterpart of the repair response in vivo.

Ultrastructure of human endometrial epithelium in monolayer culture with and without steroid hormones

Colonies of cells of epithelioid appearance were identified in monolayer cultures grown up to 50 days from normal human endometrial cell suspension obtained by a method designed to insure a maximum harvest of glandular cells. Groups of these cells were separated from stromal cells by means of cloning cylinders. Studies comparing the ultrastructure of cells of this type to fresh endometrial tissue revealed a number of similarities. The morphological characteristics common to both types of samples included junctional complexes, perinuclear microfilaments and microvilli with glycocalyx. Other common features were prominent nucleoli, well developed Golgi, rough endoplasmic reticulum and membrane-bound electron-dense bodies in the cytoplasm. A stripping technique applied to the fetal bovine serum used in the nutrient medium made it possible to initiate cultures in a steroid-free environment and to maintain them in the presence of the specified concentration of estradiol and/or progesterone. Isolation of epithelial cells of endometrium in monolayer culture may provide a useful model system in which to study the specific effects of steroid hormones on cellular function and differentiation.