Studies on the cytodynamics of human endometrial regeneration. III. In vitro short-term incubation historadioautography

Improvement in post-partum uterine involution in rats treated with Apios americana

OBJECTIVE

Apios americana, a plant used as a staple ingredient of native American diets, has various properties, including anti-cancer, anti-hyperglycemic, hypotensive, and anti-inflammatory activity. In Japan, Apios is used as a post-natal medication. After parturition, women undergo a period of recovery as they return to pre-pregnancy conditions. However, few health products that aid post-partum recovery are on the market. We explored whether Apios can accelerate the post-partum recovery process, in particular the involution of the uterus.

METHODS

Female rats kept in individual cages were mated with two male rats, with the exception of the control group (female rats without mating, on basal diet; n=6). After delivery, rats were divided into five groups based on their diet: basal diet (model; n=6); basal diet+oral intake at 5.4 g/kg of Chanfukang granules (a Chinese patent medicine preparation for post-partum lochia) (positive; n=6); basal diet containing 10% Apios powder (low; n=6); basal diet containing 20% Apios powder (medium; n=6); basal diet containing 40% Apios powder (high; n=6). Five days later, uteri and spleens were weighed. Uterus and spleen indices for each rat were calculated by dividing visceral weight by the total weight. Hormone and cytokine concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Histological analysis of uteri was completed using hematoxylin and eosin (H&E) staining. Expression of matrix metalloproteinases and inhibitors in uteri was measured by western blotting.

RESULTS

Our results showed that Apios treatment reduced the post-partum uterus index and regulated the hormone concentrations. Moreover, we found that the process of uterine involution was accelerated, based on morphological changes in the uterus. In addition, our results indicated that Apios alleviated the inflammatory response induced by the involution process. Transforming growth factor β was also found to be regulated by Apios. There were significant downregulation of matrix metalloproteinases and upregulation of their inhibitors by Apios, which suggested that Apios increased the rate of the collagen clearance process.

CONCLUSIONS

These results, based on experimental observations at the molecular and protein levels, verified our hypothesis that Apios can improve uterine involution, and demonstrated the potential application of Apios in post-partum care.

Long-term label retaining cells localize to distinct regions within the female reproductive epithelium

The uterus is an extremely plastic organ that undergoes cyclical remodeling including endometrial regeneration during the menstrual cycle. Endometrial remodeling and regeneration also occur during pregnancy and following parturition, particularly in hemochorial implanting species. The mechanisms of endometrial regeneration are not well understood. Endometrial stem/progenitor cells are proposed to contribute to endometrial regeneration in both humans and mice. BrdU label retention has been used to identify potential stem/progenitor cells in mouse endometrium. However, methods are not available to isolate BrdU label-retaining cells (LRC) for functional analyses. Therefore, we employed a transgenic mouse model to identify H2B-GFP LRCs throughout the female reproductive tract with particular interest on the endometrium. We hypothesized that the female reproductive tract contains a population of long-term LRCs that persist even following pregnancy and endometrial regeneration. Endometrial cells were labeled (pulsed) either transplacentally/translactationally or peripubertally. When mice were pulsed transplacentally/translactationally, the label was not retained in the uterus. However, LRCs were concentrated to the distal oviduct and endocervical transition zone (TZ) following natural (i.e., pregnancy/parturition induced) and mechanically induced endometrial regeneration. LRCs in the distal oviduct and endocervical TZ expressed stem cell markers and did not express ERα or PGR, implying the undifferentiated phenotype of these cells. Oviduct and endocervical TZ LRCs did not proliferate during endometrial re-epithelialization, suggesting that they do not contribute to the endometrium in a stem/progenitor cell capacity. In contrast, when mice were pulsed peripubertally long-term LRCs were identified in the endometrial glandular compartment in mice as far out as 9 months post-pulse. These findings suggest that epithelial tissue of the female reproductive tract contains 3 distinct populations of epithelial cells that exhibit stem/progenitor cell qualities. Distinct stem/progenitor-like cells localize to the oviduct, endometrium, and cervix.

Reepithelialization of the uterine surface arises from endometrial glands: evidence from a functional mouse model of breakdown and repair

The human endometrium is highly regenerative undergoing monthly cycles of growth and regression. Endometrial repair after menses is a critical component of the cycle; however, little is understood about the mechanisms behind this rapid process. Adult stem/progenitor cells identified in human and mouse endometrium may be responsible for its remarkable regenerative capacity; however, a functional role for stem/progenitor cells in menstruation is yet to be established. This study aimed to identify label retaining cells as candidate epithelial stem or progenitor cells involved in the rapid reepithelization of the uterine surface in our functional mouse model of endometrial breakdown and repair. Adult mice were pulse labeled with bromodeoxyuridine before endometrial breakdown and repair was induced. Throughout endometrial breakdown and repair, very rapid dilution of bromodeoxyuridine label was observed in the luminal epithelium, whereas label within the glandular epithelium remained constant. Importantly, glandular epithelial cells were shown to proliferate selectively in response to endometrial repair, and the majority strongly expressed estrogen receptor-alpha at this time. This is the first study to demonstrate a functionally diverse response during endometrial repair from the anatomically connected luminal and glandular epithelium and highlights the likelihood that the endometrial glands are the residence of epithelial progenitor cells contributing to reepithelialization of the uterine surface after menses.

The Macaque Endometrium, with Special Reference to the Cynomolgus Monkey (Macaca fascicularis)

The macaque endometrium undergoes dramatic morphologic and functional changes during the menstrual cycle that are nearly identical to those of the human endometrium. The sequential events that take place in the endometrium are mainly driven by the ovarian steroids and their respective receptors. To be able to interpret the changes and effects induced by mammalian or synthetic hormones and other compounds that could have influence on the hormonal status of the animal, a thorough knowledge of the anatomy, physiology, and histology of the cyclic hormone-mediated processes within the endometrium is indispensable. In this paper we give an overview of uterine growth and development, anatomy, basic histology, aging, spontaneous pathology, and the techniques to study the endometrium in-life. In addtion, a comprehensive description of the receptor-mediated, hormone-driven morphological changes during the menstrual cycle in the cynomolgus monkey (Macaca fascicularis) is given. Where possible, differences between the macaque and human endometria are discussed.

Competing Interests: This article was sponsored by Covance Inc. and Schering-Plough. Gerhard F. Weinbauer and Eberhard Buse are employed by Covance Inc. Eric Van Esch is employed by Schering-Plough. No other competing interests were declared.

Estrogen is not essential for full endometrial restoration after breakdown: lessons from a mouse model

The current dogma surrounding endometrial regeneration after menses includes a critical need for estrogen-primed proliferation. Although some evidence suggests that estrogen may not be required for the initial reepithelialization of the uterine surface, it is widely believed that it is essential for successful stromal renewal. This study aimed to identify proliferating cell types during endometrial repair and to examine whether estrogen is required for successful repair using a previously developed mouse model. In the model, decidualization is artificially induced, and progesterone support withdrawn; the endometrial tissue progressively breaks down by 24 h after progesterone withdrawal and by 48 h has usually undergone complete repair. Although the mice are ovariectomized, restoration of both the stromal and epithelial components proceeds rapidly after breakdown and results in what appears to be a normal endometrium. However, potential estrogenic influences from extraovarian sources (particularly the diet and fat) remain. In this study, complete removal of extraovarian estrogen was achieved by maintenance of animals on a soy-free diet and administration of aromatase inhibitor letrozole. No significant differences in uterine weight or estrogen-responsive genes lactoferrin and progesterone receptor were observed compared with control ovariectomized but otherwise untreated mice, whereas significantly higher measurements were obtained from an estrogen-added group. Importantly, no significant difference in the rate of endometrial repair was observed in the complete absence of estrogen, demonstrating that estrogen is not essential for complete endometrial restoration in this model.

Bcl-2 and Fas expression in eutopic and ectopic human endometrium during the menstrual cycle in relation to endometrial cell apoptosis

OBJECTIVE

Our purpose was to investigate Bcl-2 and Fas expression in human eutopic and ectopic endometrium during the menstrual cycle in relation to endometrial cell apoptosis.

STUDY DESIGN

Eutopic and ectopic endometrial samples were obtained from 29 patients with endometriosis, and eutopic endometrial tissue samples were obtained from 9 patients with uterine myoma. Bcl-2 and Fas expression were examined by immunohistochemical staining with specific monoclonal antibodies; Bcl-2 expression in eutopic endometrium was also examined by Western blotting and apoptotic cells were detected by the labeling of deoxyribonucleic acid fragments.

RESULTS

In eutopic endometrium Bcl-2 was strongly expressed during the proliferative phase. Endometrial glandular cells showed evidence of cyclic changes in Bcl-2 expression, but cyclic changes were not apparent in peritoneal and ovarian endometriotic tissue. Fas expression was observed on glandular cells but not on stromal cells, and no cyclic changes in expression occurred in either ectopic or eutopic endometrium. Apoptotic cells were observed primarily in the glandular cells of the basal layer in eutopic endometrium during the late secretory and menstrual phases.

CONCLUSION

The current study indicated that there was no apparent correlation between Bcl-2 or Fas expression with endometrial cell apoptosis. The absence of cyclic changes in Bcl-2 expression in ectopic endometrium implied a difference in the mechanisms of proliferation or differentiation between eutopic and ectopic endometrium.

Origin of premenstrual syndrome: assessment by endometrial ablation

STUDY OBJECTIVE

To determine the origin of premenstrual syndrome (PMS) by endometrial ablation.

DESIGN

Evaluation of 108 consecutive women requiring endometrial ablation.

SETTING

The study was conducted in several hospitals and a surgical center in Fort Worth, Texas. Evaluation of patients was done in-office.

PATIENTS

The women had disabling uterine bleeding not related to malignancy. Of the 108 women, 6 were having a second procedure.

INTERVENTIONS

All women underwent endometrial ablation with the rollerbar resectoscope under local stand-by anesthesia, with suction curettage preparation of the uterus.

MEASUREMENTS AND MAIN RESULTS

The 73 women who were identified with PMS were evaluated by a 12-point protocol preoperatively and between 1 and 2 years postoperatively to gain insight into the origin of PMS. After surgery most of them were initially amenorrheic and essentially free of symptoms; however, with recurrence of bleeding PMS often recurred. Persistence of amenorrhea after ablation was associated with continued relief of PMS.

CONCLUSIONS

We postulate that the etiology of PMS in women with disabling menstrual bleeding involves products from or substances in endometrial tissue.

The number of proliferating cell nuclear antigen positive cells in endometriotic lesions differs from that in the endometrium. Analysis of PCNA positive cells during the menstrual cycle and in post-menopause

Immunohistochemical expression of proliferating cell nuclear antigen (PCNA) was studied in the endometrium and in endometriotic lesions during the menstrual cycle and in post-menopausal patients. During the menstrual cycle, in the basal layer of the endometrium, an increase in the number of positive indices (PI) of PCNA was observed in epithelial cells from the menstrual phase. It reached a maximum in the proliferative phase and decreased in the secretory phase. However, no change was observed in the stromal cells of the basal layer. In the functional layer of the endometrium, the PI of the epithelial cells showed a high peak in the late proliferative phase, decreased sharply in the secretory phase and remained unchanged thereafter. The PI of the stromal cells in the functional layer showed two peaks, one in the late proliferative and the other in the mid and late secretory phase. In the endometriotic lesions, except for the proliferative phase, the number of PI was significantly higher than that of the corresponding endometrium and no significant changes were observed during the menstrual cycle. In post-menopausal endometriotic lesions, the number of PI was also higher than that of the corresponding endometrium. Thus the numbers of PI differed between the endometrium and endometriotic lesions in the same patients. These results imply that the endometriotic lesions are constantly more proliferative than the endometrium irrespective of the hormonal milieu during both the menstrual cycle and in a post-menopausal environment.

The distribution of oestrogen and progesterone receptors in the human endometrial basal and functional layer during the normal menstrual cycle. An immunocytochemical study

The distribution of oestrogen and progesterone receptors in the human endometrial basal and functional layer during the normal menstrual cycle was investigated by means of an immunocytochemical technique. A cyclic pattern of receptor distribution was observed. The highest concentration of hormone receptors was observed in the basal layer, in accordance with the idea that this layer is the source of endometrial regeneration.