Toru Arase

Stem cell-like properties of the endometrial side population: Implication in endometrial regeneration

Background The human endometrium undergoes cyclical regeneration throughout a womans reproductive life. Ectopic implantation of endometrial cells through retrograde menstruation gives rise to endometriotic lesions which affect approximately 10% of reproductive-aged women. The high regenerative capacity of the human endometrium at eutopic and ectopic sites suggests the existence of stem/progenitor cells and a unique angiogenic system. The objective of this study was to isolate and characterize putative endometrial stem/progenitor cells and to address how they might be involved in the physiology of endometrium. Methodology/Principal Findings We found that approximately 2% of the total cells obtained from human endometrium displayed a side population (SP) phenotype, as determined by flow cytometric analysis of Hoechst-stained cells. The endometrial SP (ESP) cells exhibited preferential expression of several endothelial cell markers compared to endometrial main population (EMP) cells. A medium specific for endothelial cell culture enabled ESP cells to proliferate and differentiate into various types of endometrial cells, including glandular epithelial, stromal and endothelial cells in vitro, whereas in the same medium, EMP cells differentiated only into stromal cells. Furthermore, ESP cells, but not EMP cells, reconstituted organized endometrial tissue with well-delineated glandular structures when transplanted under the kidney capsule of severely immunodeficient mice. Notably, ESP cells generated endothelial cells that migrated into the mouse kidney parenchyma and formed mature blood vessels. This potential for in vivo angiogenesis and endometrial cell regeneration was more prominent in the ESP fraction than in the EMP fraction, as the latter mainly gave rise to stromal cells in vivo. Conclusions/Significance These results indicate that putative endometrial stem cells are highly enriched in the ESP cells. These unique characteristics suggest that ESP cells might drive physiological endometrial regeneration and be involved in the pathogenesis of endometriosis.

Side population in human uterine myometrium displays phenotypic and functional characteristics of myometrial stem cells

Over the course of pregnancy, the human uterus undergoes a 500- to 1,000-fold increase in volume and a 24-fold increase in weight. The uterine smooth muscle layer or myometrium is remodeled, and both cell hypertrophy and hyperplasia are evident. The origin of the new smooth muscle cells, however, is unclear. They may arise from existing smooth muscle cells, or they may be the product of stem cell differentiation. This study describes a subset of myometrial cells isolated from nonpregnant human myometrium that represents the myometrial stem cell population. This was characterized as side population of myometrial cells (myoSP) by a distinct Hoechst dye efflux pattern. In contrast to the main population of myometrial cells (myoMP), myoSP resided in quiescence, underexpressed or lacked myometrial cell markers, and could proliferate and eventually differentiate into mature myometrial cells in vitro only under low oxygen concentration. Although myoMP displayed mature myometrial phenotypes before and after in vitro cultivation, only myoSP, not myoMP, generated functional human myometrial tissues efficiently when transplanted into the uteri of severely immunodeficient mice. Finally, myoSP were multipotent and made to differentiate into osteocytes and adipocytes in vitro under the appropriate differentiation-inducing conditions. Thus, myoSP exhibited phenotypic and functional characteristics of myometrial stem cells. Study of myoSP will improve the understanding of myometrial physiology and the pathogenesis of myometrium-derived diseases such as leiomyoma. myoSP may also represent a novel source of biological material that could be used in the reconstruction of not only the human uterus but also other organs as well.

The UDP-Glucose Receptor P2RY14 Triggers Innate Mucosal Immunity in the Female Reproductive Tract by Inducing IL-8

Innate mucosal immune responses, including recognition of pathogen-associated molecular patterns through Toll-like receptors, play an important role in preventing infection in the female reproductive tract (FRT). Damaged cells release nucleotides, including ATP and uridine 5′-diphosphoglucose (UDP-glucose), during inflammation and mechanical stress. We show in this report that P2RY14, a membrane receptor for UDP-glucose, is exclusively expressed in the epithelium, but not the stroma, of the FRT in humans and mice. P2RY14 and several proinflammatory cytokines, such as IL-8, are up-regulated in the endometria of patients with pelvic inflammatory disease. UDP-glucose stimulated IL-8 production via P2RY14 in human endometrial epithelial cells but not stromal cells. Furthermore, UDP-glucose enhanced neutrophil chemotaxis in the presence of a human endometrial epithelial cell line in an IL-8-dependent manner. Administration of UDP-glucose into the mouse uterus induced expression of macrophage inflammatory protein-2 and keratinocyte-derived cytokine, two murine chemokines that are functional homologues of IL-8, and augmented endometrial neutrophil recruitment. Reduced expression of P2RY14 by small interfering RNA gene silencing attenuated LPS- or UDP-glucose-induced leukocytosis in the mouse uterus. These results suggest that UDP-glucose and its receptor P2RY14 are key front line players able to trigger innate mucosal immune responses in the FRT bypassing the recognition of pathogen-associated molecular patterns. Our findings would significantly impact the strategic design of therapies to modulate mucosal immunity by targeting P2RY14.

OCT4 expression in human uterine myometrial stem/progenitor cells

BACKGROUND The transcription factor, octamer-binding transcription factor 4 (OCT4)/POU5F1, is expressed in embryonic stem cells, germ cells and some types of adult stem cells. Human OCT4 encodes two isoforms, OCT4A and OCT4B. While OCT4A plays a crucial role in the maintenance of stem cell properties, including pluripotency, whereas OCT4B does not. We previously reported that human myometrium contains side population cells (myoSP) with a Hoechst 33 342 low-fluorescent profile. These cells exhibit phenotypic and functional characteristics of myometrial stem cells. The objective of this study was to investigate the comparative expression of OCT4 in the stem/progenitor cell population of the human myometrium. METHODS Human myometrial tissue samples were collected from 18 consenting patients who underwent hysterectomy because of benign gynecological diseases. The resultant isolated or cultured myometrial cells and isolated myoSP were subjected to semi-quantitative and real-time RT-PCR analyses, immunoblot analyses and immunohistochemistry. RESULTS RT-PCR and immunoblot analyses revealed that OCT4 mRNA and OCT4 protein were detectable in some (but not all) myometrial samples. Immunohistochemistry showed that OCT4 protein was confined to the nuclei of relatively few cells in myometrial tissues expressing OCT4 mRNA. OCT4 and OCT4A transcripts, but not those of OCT4B, were more abundant in myoSP than in non-myoSP, as determined by real-time and semi-quantitative RT-PCR analyses. CONCLUSIONS Relatively few myometrial cells express OCT4 protein. OCT4 mRNA, in particular OCT4A mRNA, is up-regulated in myoSP that have been reported to exhibit stem cell-like properties. Taken together, the present results indicate that the myoSP population is enriched in OCT4 mRNA.

Pregnancy outcomes of reciprocal translocation carriers who have a history of repeated pregnancy loss

Cytogenetic investigation of 2,324 Japanese couples with repeated pregnancy loss revealed that 4.91% of couples (n = 114) had chromosome abnormalities including reciprocal translocation (n = 74), Robertsonian translocation (n = 23), and inversion (n = 10). Parental reciprocal translocation was a significant predictor of subsequent miscarriage (adjusted odds ratio: 3.6, 95% confidence interval: 1.8-7.1), and most of the miscarriages of the carrier couples were inevitable because of abnormal karyotypes, despite appropriate treatments.

Glycodelin blocks progression to S phase and inhibits cell growth: a possible progesterone-induced regulator for endometrial epithelial cell growth.

Prolonged exposure to unopposed estrogen in the absence of progesterone gives rise to endometrial hyperplasia and carcinoma. Post-ovulatory progesterone is necessary for the proper growth and differentiation of endometrial epithelial cells (EECs). Progesterone exposure induces the endometrial production of numerous bioactive substances, one of which is the glycoprotein, glycodelin (Gd). We investigated the role of Gd in cell cycle progression and cell growth to better understand how Gd affects EEC behavior and endometrial cancer pathogenesis. Ishikawa cells, a well-differentiated human endometrial epithelial cancer cell line, were transfected with expression plasmids encoding enhanced green fluorescent protein (EGFP) or EGFP-fused Gd (EGFP-Gd). They were then subjected to a cell proliferation assay, flow cytometry cell cycle analysis and RT-PCR analysis of cyclin-dependent kinase inhibitors (CDKIs) including p21, p27 and p16. Overexpression of EGFP-Gd resulted in a reduction of cell proliferation activity, an accumulation of G1-phase cells and up-regulation of p21, p27 and p16 mRNAs. Furthermore, progesterone-induced inhibition of Ishikawa cell growth was partially attenuated by Gd knockdown using siRNA. These results indicate that Gd causes inhibition of G1/S progression together with up-regulation of CDKIs thereby reducing cell growth. Thus, progesterone-induced expression of Gd may, at least in part, contribute to the suppression of endometrial epithelial growth observed during the secretory phase.

Histone acetylation in reproductive organs: Significance of histone deacetylase inhibitors in gene transcription

Acetylation of histories is cooperatively regulated by two groups of enzymes, histone acetyltransferases and histone deacetylases. Histone acetylation status plays a fundamental role in the level of gene transcription; numerous studies have demonstrated that histone deacetylase inhibitors cause cell growth arrest, apoptosis, and differentiation in various cells including human mammary gland and endometrial cells by altering transcription of a small number of genes. A recent study has also shown that a highly acetylated histone status alters cell motility. After the present review of the published reports on the mechanisms underlying histone acetylation and in vitro effects of histone deacetylase inhibitors, we conclude that this class of agents may have potential not only as anticancer drugs, but also as inducers of differentiation and/or motility for benign gynecologic conditions such as endometriosis and disorders of endometrial differentiation and dysfunction.

Human endometrial cytodifferentiation by histone deacetylase inhibitors

Human uterine endometrium repeats proliferation, differentiation (decidualization) and tissue breakdown during the menstrual period. Appropriate secretion of ovarian steroid hormones regulates these sequential endometrial remodeling cycles. While progesterone replacement therapy is adopted for endometrial dysfunction of differentiation, including recurrent impairment of implantation, no obvious effective results are obtained. Histone reversible acetylation, regulated by histone acetyltransferases and histone deacetylases plays a pivotal role in gene transcription. Although, in cells cultured with histone deacetylase inhibitors (HDACI), the expression of only about 2% of expressed genes is changed twofold or more compared with untreated control cells. Numerous previous works have demonstrated that HDACI affect cell proliferation/apoptosis in a variety of types of cells. To date, several HDACI are in phase I or phase II clinical trials as anti-cancer drugs. However, no reports have been found that HDACI is useful for transdifferentiation in human endometrium. Recently, we reported that HDACI could induce the expression of differentiation marker proteins, morphological change and functional cytodifferentiation in both human endometrial stromal and epithelial cells. In this review, we summarize the effect of HDACI against the human endometrial cytodifferentiation, indicating the possibility that HDACI can be used not only as an anticancer drug, but also as a transdifferentiation reagent, based on a new strategy.

CD34 and CD49f Double-Positive and Lineage Marker-Negative Cells Isolated from Human Myometrium Exhibit Stem Cell-Like Properties Involved in Pregnancy-Induced Uterine Remodeling

ABSTRACT Repeated and dramatic pregnancy-induced uterine enlargement and remodeling throughout reproductive life suggests the existence of uterine smooth muscle stem/progenitor cells. The aim of this study was to isolate and characterize stem/progenitor-like cells from human myometrium through identification of specific surface markers. We here identify CD49f and CD34 as markers to permit selection of the stem/progenitor cell-like population from human myometrium and show that human CD45– CD31– glycophorin A– and CD49f+ CD34+ myometrial cells exhibit stem cell-like properties. These include side population phenotypes, an undifferentiated status, high colony-forming ability, multilineage differentiation into smooth muscle cells, osteoblasts, adipocytes, and chondrocytes, and in vivo myometrial tissue reconstitution following xenotransplantation. Furthermore, CD45– CD31– glycophorin A– and CD49f+ CD34+ myometrial cells proliferate under hypoxic conditions in vitro and, compared with the untreated nonpregnant myometrium, show greater expansion in the estrogen-treated nonpregnant myometrium and further in the pregnant myometrium in mice upon xenotransplantation. These results suggest that the newly identified myometrial stem/progenitor-like cells influenced by hypoxia and sex steroids may participate in pregnancy-induced uterine enlargement and remodeling, providing novel insights into human myometrial physiology.