The Importance of the Canonical Wnt Signaling Pathway in the Porcine Endometrial Stromal Stem/Progenitor Cells: Implications for Regeneration

Hypoxia-induced upregulation of hsa-miR-584-3p suppresses endometrial glandular epithelial cell function by targeting DKK-1

OBJECTIVE

To investigate the impact of hypoxia on microRNA (miRNA) expression profiles in endometrial glandular epithelial cells (EECs) and elucidate potential mechanisms underlying proliferation, migration, and invasion.

METHODS

EECs in the logarithmic growth phase were exposed to normoxic (21% oxygen) and hypoxic (1% oxygen) conditions. MiRNA expression profiles were analyzed using RNA sequencing, and differential expression of hsa-miR-584-3p was confirmed by real-time quantitative PCR (RT-qPCR). Target prediction through TargetScan identified Dickkopf-1 (DKK-1) as a target gene of hsa-miR-584-3p. The interaction between hsa-miR-584-3p and DKK-1 was validated through a double-luciferase reporter gene assay and Western blotting. Cell proliferation, migration, and invasion were assessed using the Cell Counting Kit-8 (CCK-8) assay, wound healing assay, and Transwell invasion assay, respectively.

RESULTS

Hypoxic conditions significantly upregulated the expression of hsa-miR-584-3p in EECs (P<0.001). TargetScan analysis predicted DKK-1 as a downstream target of hsa-miR-584-3p. The double-luciferase reporter gene assay confirmed the binding of hsa-miR-584-3p to the 3' untranslated region of the DKK-1 gene, leading to reduced DKK-1 protein expression (P<0.001). Functional assays demonstrated decreased proliferation and increased migration and invasion of EECs under hypoxia.

CONCLUSION

Hypoxia-induced upregulation of hsa-miR-584-3p suppresses the function of EECs by targeting DKK-1 protein activity, thereby influencing their proliferation, migration, and invasion.

Promotion of uterine reconstruction by a tissue-engineered uterus with biomimetic structure and extracellular matrix microenvironment

The recurrence rate for severe intrauterine adhesions is as high as 60%, and there is still lack of effective prevention and treatment. Inspired by the nature of uterus, we have developed a bilayer scaffold (ECM-SPS) with biomimetic heterogeneous features and extracellular matrix (ECM) microenvironment of the uterus. As proved by subtotal uterine reconstruction experiments, the mechanical and antiadhesion properties of the bilayer scaffold could meet the requirement for uterine repair. With the modification with tissue-specific cell-derived ECM, the ECM-SPS had the ECM microenvironment signatures of both the endometrium and myometrium and exhibited the property of inducing stem cell-directed differentiation. Furthermore, the ECM-SPS has recruited more endogenous stem cells to promote endometrial regeneration at the initial stage of repair, which was accompanied by more smooth muscle regeneration and a higher pregnancy rate. The reconstructed uterus could also sustain normal pregnancy and live birth. The ECM-SPS may thereby provide a potential treatment for women with severe intrauterine adhesions.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Conditioned Medium Promotes Human Endometrial Cell Proliferation through Wnt/β-Catenin Signaling

Purpose

Mesenchymal stem cells (MSCs) and their derivant are among the promising treatments for intrauterine adhesion (IUA); they have been reported to repair the endometrial injury by proliferating endometrial cells. However, the signal pathways involved are not clear. This study investigated the role of human umbilical cord mesenchymal stem cell-derived conditioned medium (hUCMSC-CM) in relieving IUA to find out whether Wnt/β-catenin signaling was involved, and if so, to determine the possible ligands.

Methods

After endometrial epithelial cells (EECs) were treated with hUCMSC-CM, their proliferation and migration were measured by the CCK8 assay and the scratch assay. The activation of Wnt/β-catenin signaling was measured by Western blots, fluorescent staining, and T-cell factor/lymphoid enhancer factor (TCF/LEF) luciferase. A Wnt inhibitor (XAV393) was used to inhibit the proliferation effect of hUCMSC-CM in EECs. Wnt5a expression in hUCMSC was measured by Western blots and fluorescent staining, and Wnt5a in hUCMSC-CM was detected by enzyme-linked immunosorbent assay (ELISA), to further clarify the mechanism.

Results

As shown by the CCK8 assay, hUCMSC-CM promoted proliferation and migration of EECs. The expression of β-catenin, c-myc, and cyclin D1 increased in EECs after being treated with hUCMSC-CM. Moreover, hUCMSC-CM was found to promote β-catenin delivery into nuclei by Western blot and fluorescent staining; meanwhile, the inhibitor (XAV393) could restrain this process and inhibit the effect of hUCMSC-CM on EEC proliferation. Wnt5a was detected in hUCMSCs and hUCMSC-CM, which might be a potential therapeutic target.

Conclusion

This study demonstrated that hUCMSC-CM promoted human endometrial cell proliferation through Wnt/β-catenin signaling, and Wnt5a might be a potential activator. This would be one of the activating signal pathways in the MSC-related treatment of IUA.

WNT5A Interacts With FZD5 and LRP5 to Regulate Proliferation and Self-Renewal of Endometrial Mesenchymal Stem-Like Cells

Endometrial mesenchymal stem-like cells (eMSC) reside in the basal layer of the endometrium and are responsible for cyclic regeneration during the reproductive lives of women. Myometrial cells act as a component of the niche and regulate the stem cell fate through the activation of WNT/β-catenin signaling via WNT5A. Since WNT5A-responsive mechanisms on eMSC are still uncertain, we hypothesize that the WNT ligand–WNT5A works to activate WNT/β-catenin signaling through binding to Frizzled receptors (FZDs) and co-receptor low-density lipoprotein receptor-related protein 5 (LRP5). Among the various receptors that have been reported to interact with WNT5A, we found FZD5 abundantly expressed by eMSC when compared to unfractionated stromal cells. Neutralizing the protein expression by using anti-FZD5 antibody suppressed the stimulatory effects on phenotypic expression and the clonogenicity of eMSC in a myometrial cell–eMSC co-culture system as well as in an L-Wnt5a conditioned medium. Gene silencing of FZD5 not only reduced the binding of WNT5A to eMSC but also decreased the TCF/LEF transcriptional activities and expression of active β-catenin. Inhibition of LRP coreceptors with recombinant Dickkopf-1 protein significantly reduced the binding affinity of eMSC to WNT5A as well as the proliferation and self-renewal activity. During postpartum remodeling in mouse endometrium, active β-catenin (ABC) was detected in label-retaining stromal cells (LRSCs), and these ABC+ LRSCs express FZD5 and LRP5, suggesting the activation of WNT/β-catenin signaling. In conclusion, our findings demonstrate the interaction of WNT5A, FZD5, and LRP5 in regulating the proliferation and self-renewal of eMSC through WNT/β-catenin signaling.

The effect of hypoxia on the proteomic signature of pig adipose-derived stromal/stem cells (pASCs)

Human adipose-derived stem cells (ASCs) have potential to improve wound healing; however, their equivalents from domestic animals have received less attention as an alternative cell-based therapy for animals or even humans. Hypoxia is essential for maintaining stem cell functionality in tissue-specific niches. However, a cellular response to low oxygen levels has not been demonstrated in pig ASCs. Hence, the goal of our study was to characterize ASCs isolated from the subcutaneous fat of domestic pigs (pASCs) and examine the effect of hypoxia on their proteome and functional characteristics that might reproduce pASCs wound healing ability. Analysis of immunophenotypic and functional markers demonstrated that pASCs exhibited characteristics of mesenchymal stem cells. Proteomic analysis revealed 70 differentially abundant proteins between pASCs cultured under hypoxia (1% O₂) or normoxia (21% O₂). Among them, 42 proteins were enriched in the cells exposed to low oxygen, whereas 28 proteins showed decrease expression following hypoxia. Differentially expressed proteins were predominantly involved in cell metabolism, regulation of focal and intracellular communication, and attributed to wound healing. Functional examination of hypoxic pASCs demonstrated acquisition of contractile abilities in vitro. Overall, our results demonstrate that hypoxia pre-conditioning impacts the pASC proteome signature and contractile function in vitro and hence, they might be considered for further cell-based therapy study on wound healing.

Endometrial and Menstrual Blood Mesenchymal Stem/Stromal Cells: Biological Properties and Clinical Application

A highly proliferative mesenchymal stem/stromal cell (MSC) population was recently discovered in the dynamic, cyclically regenerating human endometrium as clonogenic stromal cells that fulfilled the International Society for Cellular Therapy (ISCT) criteria. Specific surface markers enriching for clonogenic endometrial MSC (eMSC), CD140b and CD146 co-expression, and the single marker SUSD2, showed their perivascular identity in the endometrium, including the layer which sheds during menstruation. Indeed, cells with MSC properties have been identified in menstrual fluid and commonly termed menstrual blood stem/stromal cells (MenSC). MenSC are generally retrieved from menstrual fluid as plastic adherent cells, similar to bone marrow MSC (bmMSC). While eMSC and MenSC share several biological features with bmMSC, they also show some differences in immunophenotype, proliferation and differentiation capacities. Here we review the phenotype and functions of eMSC and MenSC, with a focus on recent studies. Similar to other MSC, eMSC and MenSC exert immunomodulatory and anti-inflammatory impacts on key cells of the innate and adaptive immune system. These include macrophages, T cells and NK cells, both in vitro and in small and large animal models. These properties suggest eMSC and MenSC as additional sources of MSC for cell therapies in regenerative medicine as well as immune-mediated disorders and inflammatory diseases. Their easy acquisition via an office-based biopsy or collected from menstrual effluent makes eMSC and MenSC attractive sources of MSC for clinical applications. In preparation for clinical translation, a serum-free culture protocol was established for eMSC which includes a small molecule TGFβ receptor inhibitor that prevents spontaneous differentiation, apoptosis, senescence, maintains the clonogenic SUSD2+ population and enhances their potency, suggesting potential for cell-therapies and regenerative medicine. However, standardization of MenSC isolation protocols and culture conditions are major issues requiring further research to maximize their potential for clinical application. Future research will also address crucial safety aspects of eMSC and MenSC to ensure these protocols produce cell products free from tumorigenicity and toxicity. Although a wealth of data on the biological properties of eMSC and MenSC has recently been published, it will be important to address their mechanism of action in preclinical models of human disease.

Understanding the regulatory mechanisms of endometrial cells on activities of endometrial mesenchymal stem-like cells during menstruation

BACKGROUND

The identification of endometrial stem/progenitor cells in a high turnover rate tissue suggests that a well-orchestrated underlying network controls the behaviour of these stem cells. The thickness of the endometrium can grow from 0.5-1 mm to 5-7 mm within a week indicating the need of stem cells for self-renewal and differentiation during this period. The cyclical regeneration of the endometrium suggests specific signals can activate the stem cells during or shortly after menstruation.

METHODS

Endometrial mesenchymal stem-like cells (eMSCs) were cocultured with endometrial epithelial or stromal cells from different phases of the menstrual cycle; the clonogenicity and the phenotypic expression of eMSC markers (CD140b and CD146) were assessed. The functional role of WNT/β-catenin signalling on eMSC was determined by western blot analysis, immunofluorescent staining, flow cytometry, quantitative real-time PCR and small interfering RNA. The cytokine levels in the conditioned medium of epithelial or stromal cells cocultured with eMSCs were evaluated by enzyme-linked immunosorbent assays.

RESULTS

Coculture of endometrial cells (epithelial or stromal) from the menstrual phase enhanced the clonogenicity and self-renewal activities of eMSCs. Such phenomenon was not observed in niche cells from the proliferative phase. Coculture with endometrial cells from the menstrual phase confirmed an increase in expression of active β-catenin in the eMSCs. Treatment with IWP-2, a WNT inhibitor, suppressed the observed effects. Anti-R-spondin-1 antibody reduced the stimulatory action of endometrial niche cells on WNT/β-catenin activation in the T cell factor/lymphoid enhancer-binding factor luciferase reporter assay. Moreover, the mRNA level and protein immunoreactivities of leucine-rich repeat-containing G-protein coupled receptor 5 were higher in eMSCs than unfractionated stromal cells. Conditioned media of endometrial niche cells cocultured with eMSCs contained increased levels of C-X-C motif ligand 1 (CXCL1), CXCL5 and interleukin 6. Treatment with these cytokines increased the clonogenic activity and phenotypic expression of eMSCs.

CONCLUSIONS

Our findings indicate a role of WNT/β-catenin signalling in regulating activities of endometrial stem/progenitor cells during menstruation. Certain cytokines at menstruation can stimulate the proliferation and self-renewal activities of eMSCs. Understanding the mechanism in the regulation of eMSCs may contribute to treatments of endometrial proliferative disorders such as Asherman's syndrome.

Myometrial Cells Stimulate Self-Renewal of Endometrial Mesenchymal Stem-Like Cells Through WNT5A/β-Catenin Signaling

Human endometrium undergoes cycles of proliferation and differentiation throughout the reproductive years of women. The endometrial stem/progenitor cells contribute to this regenerative process. They lie in the basalis layer of the endometrium next to the myometrium. We hypothesized that human myometrial cells provide niche signals regulating the activities of endometrial mesenchymal stem-like cells (eMSCs). In vitro coculture of myometrial cells enhanced the colony-forming and self-renewal ability of eMSCs. The cocultured eMSCs retained their multipotent characteristic and exhibited a greater total cell output when compared with medium alone culture. The expression of active β-catenin in eMSCs increased significantly after coculture with myometrial cells, suggesting activation of WNT/β-catenin signaling. Secretory factors in spent medium from myometrial cell culture produced the same stimulatory effects on eMSCs. The involvement of WNT/β-catenin signaling in self-renewal of eMSCs was confirmed with the use of WNT activator (Wnt3A conditioned medium) and WNT inhibitors (XAV939 and inhibitor of Wnt Production-2 [IWP-2]). The myometrial cells expressed more WNT5A than other WNT ligands. Recombinant WNT5A stimulated whereas anti-WNT5A antibody suppressed the colony formation, self-renewal, and T-cell factor/lymphoid enhancer-binding factor (TCF/LEF) transcriptional activities of eMSCs. Moreover, eMSCs expressed FZD4 and LRP5. WNT5A is known to activate the canonical WNT signaling in the presence of these receptor components. WNT antagonist, DKK1, binds to LRP5/6. Consistently, DKK1 treatment nullified the stimulatory effect of myometrial cell coculture. In conclusion, our findings show that the myometrial cells are niche components of eMSCs, modulating the self-renewal activity of eMSCs by WNT5A-dependent activation of WNT/β-catenin signaling. Stem Cells 2019;37:1455-1466.

Augmenting canonical Wnt signalling in therapeutically inert cells converts them into therapeutically potent exosome factories

Cardiosphere-derived cells (CDCs) are therapeutic candidates with disease-modifying bioactivity, but their variable potency has complicated their clinical translation. Transcriptomic analyses of CDCs from human donors have revealed that the therapeutic potency of these cells correlates with Wnt/β-catenin signalling and with β-catenin protein levels. Here, we show that skin fibroblasts engineered to overexpress β-catenin and the transcription factor Gata4 become immortal and therapeutically potent. Transplantation of the engineered fibroblasts into a mouse model of acute myocardial infarction led to improved cardiac function and mouse survival. And in the mdx mouse model of Duchenne muscular dystrophy, exosomes secreted by the engineered fibroblasts improved exercise capacity and reduced skeletal-muscle fibrosis. We also demonstrate that exosomes from high-potency CDCs exhibit enhanced levels of miR-92a (a known potentiator of the Wnt/β-catenin pathway), and that they activate cardioprotective bone-morphogenetic-protein signalling in cardiomyocytes. Our findings show that the modulation of canonical Wnt signalling can turn therapeutically inert mammalian cells into immortal exosome factories for cell-free therapies.

Overexpression of β-catenin and the transcription factor Gata4 in skin fibroblasts converts them into therapeutically active cells that secrete reparative exosomes as shown in mice models of myocardial infarction and Duchenne muscular dystrophy.

Benzo(a)pyrene inhibits endometrial cell apoptosis in early pregnant mice via the WNT5A pathway

Benzo(a)pyrene (BaP) is an endocrine-disrupting pollutant present in various aspects of daily life, and studies have demonstrated that BaP exerts reproductive toxicity. We previously showed that BaP damages endometrial morphology and decreases the number of implantation sites in early pregnant mice, but the mechanisms underlying these effects remain unclear. The endometrial function is crucial for implantation, which is associated with endometrial cell apoptosis. In this study, we focused on the effect of BaP on endometrial cell apoptosis and the role of WNT signaling during this process. Pregnant mice were gavaged with corn oil (control group) or 0.2 mg·kg^-1 ·day ^-1 BaP (treatment group) from Days 1 to 6 of pregnancy. BaP impaired endometrial function by decreasing the expression of HOXA10 and BMP2, two markers of receptivity and decidualization. WNT5A and β-catenin were activated in the BaP group. BaP affected the expression of apoptosis-related proteins and inhibited the apoptosis of endometrial stromal cells. In vitro, human endometrial stromal cells (HESCs) were treated with different concentrations of BaP (dimethyl sulfoxide (DMSO); 5, 10 µM). WNT5A and β-catenin were also upregulated in the BaP treatment group. HESC apoptosis was restrained by BaP. Inhibiting WNT5A by SFRP5 partially restored the effect of BaP on apoptosis. In summary, these results suggested that BaP exposure during early pregnancy activates WNT5A/β-catenin signaling pathway, which inhibits the endometrial cell apoptosis and potentially destroys endometrial function.

Human menstrual blood-derived stem cells promote the repair of impaired endometrial stromal cells by activating the p38 MAPK and AKT signaling pathways

Multiple studies have confirmed that human menstrual blood-derived stem cells (MenSCs) have potential applications in regenerative medicine or cell therapy. However, the contribution of MenSCs to endometrial repair is currently unknown. We evaluated the protective effects of MenSCs on impaired endometrial stromal cells (ESCs), as well as the signaling pathways involved in this process. Mifepristone was used to damage human ESCs, which were subsequently cocultured with MenSCs. The proliferation, apoptosis, and migration of ESCs were assessed, together with the expression of related signaling proteins including total p38 mitogen-activated protein kinase, P-p38, total protein kinase B (AKT), P-AKT, β-catenin, and vascular endothelial growth factor (VEGF). MenSCs significantly recovered the proliferation and migration ability of impaired ESCs, inhibited ESC apoptosis, and upregulated protein expression of P-AKT, P-p38, VEGF, and β-catenin. Our findings suggest that MenSC-based therapies could be promising strategies for the treatment of endometrial injury, and that AKT and p38 signaling pathways may be involved in this process.

Oestrogen, progesterone and stem cells: the discordant trio in endometriosis?

Oestrogen–progesterone signalling is highly versatile and critical for the maintenance of healthy endometrium in humans. The genomic and nongenomic signalling cascades initiated by these hormones in differentiated cells of endometrium have been the primary focus of research since 1920s. However, last decade of research has shown a significant role of stem cells in the maintenance of a healthy endometrium and the modulatory effects of hormones on these cells. Endometriosis, the growth of endometrium outside the uterus, is very common in infertile patients and the elusiveness in understanding of disease pathology causes hindrance in selection of treatment approaches to enhance fertility. In endometriosis, the stem cells are dysfunctional as it can confer progesterone resistance to their progenies resulting in disharmony of hormonal orchestration of endometrial homeostasis. The bidirectional communication between stem cell signalling pathways and oestrogen–progesterone signalling is found to be disrupted in endometriosis though it is not clear which precedes the other. In this paper, we review the intricate connection between hormones, stem cells and the cross-talks in their signalling cascades in normal endometrium and discuss how this is deregulated in endometriosis. Re-examination of the oestrogen–progesterone dependency of endometrium with a focus on stem cells is imperative to delineate infertility associated with endometriosis and thereby aid in designing better treatment modalities.

Identification of perivascular and stromal mesenchymal stem/progenitor cells in porcine endometrium

Mammalian uterus contains a population of mesenchymal stem/progenitor cells that likely contribute to endometrial regeneration during each reproductive cycle. In human and mouse, they reside in perivascular, epithelial and stromal compartments of the endometrial functionalis and basalis. Here, we aimed to identify tissue resident cells expressing mesenchymal stem cell markers CD29, CD44, CD90, CD105, CD140b and CD146 in the porcine endometrium. We used single immunofluorescence and Western blotting. Each of these markers was detected in small cells surrounding endometrial blood vessels. CD105 and CD146 were also expressed in single stromal cells. A few stromal and perivascular cells showed the presence of pluripotency marker Oct4 in the cytoplasm, but not in the nucleus, which may imply they are not truly pluripotent. Endometrial cell cultures were examined for the expression of CD29, CD44, CD90, CD105 and CD140b proteins and tested in wound-healing assay and culture model of chemotaxis. In conclusion, our results demonstrate perivascular location of prospective mesenchymal stem/progenitor cells in the porcine endometrium and may suggest that stromal CD105⁺ and CD146⁺ cells represent more mature precursors originating from their perivascular ancestors.

Endometritis and In Vitro PGE2 Challenge Modify Properties of Cattle Endometrial Mesenchymal Stem Cells and Their Transcriptomic Profile

Mesenchymal stem cells (MSCs) were isolated and characterized from postpartum bovine endometrium of animals with subclinical (n = 5) and clinical endometritis (n = 3) and healthy puerperal females (n = 5). Cells isolated displayed mean morphological features of MSCs and underwent osteogenic, chondrogenic, and adipogenic differentiation after induction (healthy and subclinical). Cells from cows with clinical endometritis did not undergo adipogenic differentiation. All cells expressed mRNAs for selected MSC markers. Endometrial MSCs were challenged in vitro with PGE₂ at concentrations of 0, 1, 3, and 10 μM, and their global transcriptomic profile was studied. Overall, 1127 genes were differentially expressed between unchallenged cells and cells treated with PGE₂ at all concentrations (763 up- and 364 downregulated, fold change > 2, and P < 0.05). The pathways affected the most by the PGE₂ challenge were immune response, angiogenesis, and cell proliferation. In conclusion, we demonstrated that healthy puerperal bovine endometrium contains MSCs and that endometritis modifies and limits some functional characteristics of these cells, such as their ability to proceed to adipogenic differentiation. Also, PGE₂, an inflammatory mediator of endometritis, modifies the transcriptomic profile of endometrial MSCs. A similar situation may occur during inflammation associated with endometritis, therefore affecting the main properties of endometrial MSCs.

Deregulated angiogenesis in chronic lung diseases: a possible role for lung mesenchymal progenitor cells (2017 Grover Conference Series)

Chronic lung disease (CLD), including pulmonary fibrosis (PF) and chronic obstructive pulmonary disease (COPD), is the fourth leading cause of mortality worldwide. Both are debilitating pathologies that impede overall tissue function. A common co-morbidity in CLD is vasculopathy, characterized by deregulated angiogenesis, remodeling, and loss of microvessels. This substantially worsens prognosis and limits survival, with most current therapeutic strategies being largely palliative. The relevance of angiogenesis, both capillary and lymph, to the pathophysiology of CLD has not been resolved as conflicting evidence depicts angiogenesis as both reparative or pathologic. Therefore, we must begin to understand and model the underlying pathobiology of pulmonary vascular deregulation, alone and in response to injury induced disease, to define cell interactions necessary to maintain normal function and promote repair. Capillary and lymphangiogenesis are deregulated in both PF and COPD, although the mechanisms by which they co-regulate and underlie early pathogenesis of disease are unknown. The cell-specific mechanisms that regulate lung vascular homeostasis, repair, and remodeling represent a significant gap in knowledge, which presents an opportunity to develop targeted therapies. We have shown that that ABCG2^pos multipotent adult mesenchymal stem or progenitor cells (MPC) influence the function of the capillary microvasculature as well as lymphangiogenesis. A balance of both is required for normal tissue homeostasis and repair. Our current models suggest that when lymph and capillary angiogenesis are out of balance, the non-equivalence appears to support the progression of disease and tissue remodeling. The angiogenic regulatory mechanisms underlying CLD likely impact other interstitial lung diseases, tuberous sclerosis, and lymphangioleiomyomatosis.

Characterization of mesenchymal stem cells in bovine endometrium during follicular phase of oestrous cycle

Stem cells have been postulated as responsible for cell regeneration in highly and continuously regenerative tissues such as the endometrium. Few studies in cattle have identified and specified the presence of stem cells in the endometrium during the oestrous cycle. The aim of this study was to investigate the presence of mesenchymal stem cells (MSCs) in the bovine endometrium during the follicular phase (FP) of the oestrous cycle. Uterine tissue was collected in the time-frame comprising day 18 of the cycle and ovulation (day 0). We isolated, cultured and expanded four primary cell lines from endometrium and identified byRT-qPCR the expression of OCT4, SOX2 but not NANOG (undifferentiated/embryonic markers), CD44 (MSCs marker) and c-KIT (stem cell marker) genes; and the encoded Oct4, Sox2 and Cd44 proteins by Western blot or immunostaining of paraffin-embedded tissue in endometrium. We demonstrated that cells isolated from bovine endometrium displayed essentially the same gene expression pattern; however, at the protein level, Oct4 and Cd44 were not detected. Besides, they showed typical functional characteristics of MSCs such as fibroblast-like morphology, plastic adherence, high proliferative capacity, clone formation in vitro and the ability to differentiate into chondrogenic, osteogenic and adipogenic lineages. We obtained for the first time an extensive characterization of undifferentiated cells populations contained in the bovine endometrium during the FP of the oestrous cycle.