Enhanced differentiation and clonogenicity of human endometrial polyp stem cells

Telomerase and Telomeres in Endometrial Cancer

Telomeres at the termini of human chromosomes are shortened with each round of cell division due to the “end replication problem” as well as oxidative stress. During carcinogenesis, cells acquire or retain mechanisms to maintain telomeres to avoid initiation of cellular senescence or apoptosis and halting cell division by critically short telomeres. The unique reverse transcriptase enzyme complex, telomerase, catalyzes the maintenance of telomeres but most human somatic cells do not have sufficient telomerase activity to prevent telomere shortening. Tissues with high and prolonged replicative potential demonstrate adequate cellular telomerase activity to prevent telomere erosion, and high telomerase activity appears to be a critical feature of most (80–90%) epithelial cancers, including endometrial cancer. Endometrial cancers regress in response to progesterone which is frequently used to treat advanced endometrial cancer. Endometrial telomerase is inhibited by progestogens and deciphering telomere and telomerase biology in endometrial cancer is therefore important, as targeting telomerase (a downstream target of progestogens) in endometrial cancer may provide novel and more effective therapeutic avenues. This review aims to examine the available evidence for the role and importance of telomere and telomerase biology in endometrial cancer.

Dedifferentiation of human uterine polyp stem cells into embryo-like cells during inducing pluripotency

By introduction of Oct4, Sox2, Klf4 and cMyc, human adult somatic cells can be reprogrammed into embryonic stem cell capable of pluripotent differentiation. In several lines of human endometrial polyp- and cervical polyp-mesenchymal stem cells (EPMSCs and CPMSC), we showed introduction of the four transcription factors led to a dedifferentiation of these cells into early embryo-like cells in three days, ranging from one-cell, two-cell, four-cell embryos, and morula to blastocyst. These early embryo-like cells resembled human early embryo derived from in vitro fertilization (IVF) in morphology, and hatching activity. These cells also expressed hypoblast (GATA4) and trophoblast (Cdx2) markers. After culturing the embryo-like cells for one month, the induced pluripotency stem cells (iPSC) could be formed (proved by pluripotency gene expression, by in vitro and in vivo differentiation). C/EBPα expression was also increased in uterine polyps. In contrast, MSCs derived from normal endometrium could not be induced to dedifferentiation to such early embryo-like cells. We conclude that EPMSCs and CPMSCs could be dedifferentiated to early embryo-like cells by the iPSC cocktail. This suggests that polyps of the organ derived from Mullerian duct may harbor epigenetic markers making them vulnerable to reprogramming to the earliest developmental stage. This study provides a simple model to derive early human embryo-like cells by in vitro.

Reciprocal crosstalk between endometrial carcinoma and mesenchymal stem cells via transforming growth factor-β/transforming growth factor receptor and C-X-C motif chemokine ligand 12/C-X-C chemokine receptor type 4 aggravates malignant phenotypes

Designated for cyclic shedding, the endometrial stroma is rich in endometrial mesenchymal stem cells (EMSCs) and may play an important role in the development of endometrial carcinoma (EC). This study characterized the crosstalk of EC cells with EMSCs and the resultant effects on malignant phenotypes. The cultured EMSCs expressed CD73, CD90, and CD105, but not CD14, CD19, CD34, CD45, or human leukocyte antigen—antigen D related markers. These EMSCs also showed osteogenic, adipogenic, and chondrogenic differentiation ability. Transforming growth factor (TGF)-β1 and C–X–C motif chemokine ligand 12 (CXCL12) secretion or expression were reciprocally enhanced in EC cells and EMSCs, as well as in their tissues. By acting on the receptors expressed in their mutual target cells, the interaction between TGF-β and CXCL12 results in the enhanced migration, invasion, tumorigenesis, and epithelial–mesenchymal transition of EC cells, which can be blocked by neutralizing the antibody of either CXCL12 or C–X–C chemokine receptor type 4. The study revealed unprecedented paracrine interactions between EC cells and EMSCs that resulted in the enhancement of transformation phenotypes. Thus, the blocking of TGF-β or CXCL12 signaling can be a therapeutic target for EC.

Mesenchymal endometrial stem/stromal cells for hard tissue engineering: a review of in vitro and in vivo evidence

Hard tissues including teeth, bone and cartilage have inability or poor capacity to self-renew, especially in large defects. Therefore, repair of damages in these tissues represents a huge challenge in the medical field today. Hard tissue engineering commonly utilizes different stem cell sources as a promising strategy for treating bone, cartilages and tooth defects or disorders. Decades ago, researchers successfully isolated and identified endometrial mesenchymal stem/stromal cells (EnSCs) and discovered their multidifferentiation potential. Current studies suggest that EnSCs have significant advantages compared with stem cells derived from other tissues. In this review article, we summarize the current in vitro and in vivo studies that utilize EnSCs or menstrual blood-derived stem cells for differentiation to osteoblasts, odontoblasts or chondroblasts in an effort to realize the potential of these cells in hard tissues regeneration.

Implications of telomeres and telomerase in endometrial pathology

BACKGROUND

Eukaryotic chromosomal ends are linear and are protected by nucleoprotein complexes known as telomeres. The complex structural anatomy and the diverse functions of telomeres as well as the unique reverse transcriptase enzyme, telomerase that maintains telomeres are under intensive scientific scrutiny. Both are involved in many human diseases including cancer, but also in ageing and chronic disease such as diabetes. Their intricate involvement in many cellular processes and pathways is being dynamically deciphered in many organs including the endometrium. This review summarizes our current knowledge on the topic of telomeres and telomerase and their potential role in providing plausible explanations for endometrial aberrations related to common gynaecological pathologies.

OBJECTIVE AND RATIONALE

This review outlines the recent major findings in telomere and telomerase functions in the context of endometrial biology. It highlights the contemporary discoveries in hormonal regulation, normal endometrial regeneration, stem cells and common gynaecological diseases such as endometriosis, infertility, recurrent reproductive failure and endometrial cancer (EC).

SEARCH METHODS

The authors carried out systematic PubMed (Medline) and Ovid searches using the key words: telomerase, telomeres, telomere length, human telomerase reverse transcriptase, telomeric RNA component, with endometrium, hormonal regulation, endometrial stem/progenitor cells, endometrial regeneration, endometriosis, recurrent miscarriage, infertility, endometrial hyperplasia, EC and uterine cancer. Publications used in this review date from 1995 until 31st June 2016.

OUTCOMES

The human endometrium is a unique somatic organ, which displays dynamic telomerase activity (TA) related to the menstrual cycle. Telomerase is implicated in almost all endometrial pathologies and appears to be crucial to endometrial stem cells. In particular, it is vital for normal endometrial regeneration, providing a distinct route to formulate possible curative, non-hormonal therapies to treat chronic endometrial conditions. Furthermore, our current understanding of telomere maintenance in EC is incomplete. Data derived from other malignancies on the role of telomerase in carcinogenesis cannot be extrapolated to EC because unlike in other cancers, TA is already present in proliferating healthy endometrial cells.

WIDER IMPLICATIONS

Since telomerase is pivotal to endometrial regeneration, further studies elucidating the role of telomeres, telomerase, their associated proteins and their regulation in normal endometrial regeneration as well as their role in endometrial pathologies are essential. This approach may allow future development of novel treatment strategies that are not only non-hormonal but also potentially curative.

Expression of CD133 in endometrial cancer cells and its implications

Cancer stem cells are an attractive therapeutic target for cancer. The present study examined stem cell characteristics of CD133+ cells isolated from endometrial cancer. Phenotypic characteristics, proliferation, migration, anchorage-independent growth, chemoresistance, gene expression profile and tumorigenicity of CD133+ tumor cells were assessed. Primary tumor exhibited immunoreactivity for CD133. Endometrial CD133+ tumor cells enhanced proliferation rate, colony formation, chemotaxis migration ability, and chemoresistance to cisplatin, paclitaxel, and doxorubicin than CD133- cells. CD133+ cells expressed more cancer stem cells markers such as EpCAM, aldehyde dehydrogenase 1 and insulin-like growth factor-1 receptor than CD133- cells. Moreover, CD133+ cells also increased expression of embryonic stem cell markers including oct4, nanog, sox2, and cmyc than CD133- cells. Finally, CD133+ tumor cells could generate xenograft but not CD133- tumor cells. CD133 and Ki67 were extensively expressed in the xenograft. In conclusion, endometrial CD133+ tumor cells displayed cancer stem cell characteristics and might represent a valuable tool for identifying endometrial cancer stem cells and hence a potential therapeutic target.

Human Infrapatellar Fat Pad-Derived Stromal Cells Have More Potent Differentiation Capacity Than Other Mesenchymal Cells and Can Be Enhanced by Hyaluronan

The microenvironment plays an important role in the homing in and differentiation of stem cells to repair injured tissue. Infrapatellar fat pad stromal cells (IFPSCs) are a promising source of such cells for the repair of articular injury-induced degeneration. This study investigated the chemotaxis of IFPSCs to chondrocytes and the effect of hyaluronan (HA) on the biological and regenerative properties of IFPSCs. The IFPSCs were obtained from patients undergoing arthroscopy and cultured via a standard 2-week culture protocol that yielded more than 10 million cells on passage 3. The results showed that the IFPSCs had a higher capacity for chondrogenic differentiation than mesenchymal cells from body fat, bone marrow, and Wharton's jelly of the umbilical cord. The IFPSCs cultured on 25% or 50% HA showed better osteogenic and adipogenic capabilities than those without HA or with 75% HA (p < 0.001). Cultures of the IFPSCs on 25% HA had a fourfold increase in chondrogenic differentiation compared to cultures without HA, which was better than with 50% and 75% HA (p < 0.05). Cell proliferation was not affected by the presence of HA. In conclusion, IFPSCs have a strong potential for chondrogenic regeneration, which can even be augmented in a 25% HA microenvironment.

Regenerating endometrium from stem/progenitor cells: is it abnormal in endometriosis, Asherman's syndrome and infertility?

PURPOSE OF REVIEW

Stem/progenitor cells are present in human and rodent endometrium and have a key role in endometrial regeneration in normal cycling and after parturition. We review emerging evidence of multiple types of endometrial stem/progenitor cells, and that abnormalities in their location and function may contribute to endometriosis.

RECENT FINDINGS

Candidate human endometrial stem/progenitors have been identified as clonogenic, Side Population and possessing tissue reconstitution activity. Markers have been identified for human endometrial mesenchymal stem cells, showing their perivascular location in functionalis and basalis endometrium. Human embryonic stem cells can be induced to develop endometrial epithelium, recapitulating endometrial development. In rodent studies, endometrial stem/progenitor cells were identified as label-retaining cells and their role in endometrial repair and regeneration revealed, perhaps via mesenchymal to epithelial transition. Studies of Wnt signalling in the regulation of endometrial stem/progenitor cells may yield insights into their function in endometrial regeneration. Stem/progenitor cells can be isolated from endometrial biopsy or menstrual blood and may be used autologously to regenerate endometrium in Asherman's syndrome.

SUMMARY

There is much to be learnt about endometrial stem/progenitor cell biology and their role in endometriosis. Endometrial stem/progenitor cells hold great promise for new treatments for infertility associated disorders, including thin dysfunctional endometrium and Asherman's syndrome.