Human post-implantation blastocyst-like characteristics of Muse cells isolated from human umbilical cord.

Muse cells, identified as cells positive for the pluripotent surface marker SSEA-3, are pluripotent-like endogenous stem cells located in the bone marrow (BM), peripheral blood, and organ connective tissues. The detailed characteristics of SSEA-3(+) cells in extraembryonic tissue, however, are unknown. Here, we demonstrated that similar to human-adult tissue-Muse cells collected from the BM, adipose tissue, and dermis as SSEA-3(+), human-umbilical cord (UC)-SSEA-3(+) cells express pluripotency markers, differentiate into triploblastic-lineage cells at a single cell level, migrate to damaged tissue, and exhibit low telomerase activity and non-tumorigenicity. Notably, ~ 20% of human-UC-SSEA-3(+) cells were negative for X-inactive specific transcript (XIST), a naïve pluripotent stem cell characteristic, whereas all human adult tissue-Muse cells are XIST-positive. Single-cell RNA sequencing revealed that the gene expression profile of human-UC-SSEA-3(+) cells was more similar to that of human post-implantation blastocysts than human-adult tissue-Muse cells. The DNA methylation level showed the same trend, and notably, the methylation levels in genes particularly related to differentiation were lower in human-UC-SSEA-3(+) cells than in human-adult tissue-Muse cells. Furthermore, human-UC-SSEA-3(+) cells newly express markers specific to extraembryonic-, germline-, and hematopoietic-lineages after differentiation induction in vitro whereas human-adult tissue-Muse cells respond only partially to the induction. Among various stem/progenitor cells in living bodies, those that exhibit properties similar to post-implantation blastocysts in a naïve state have not yet been found in humans. Easily accessible human-UC-SSEA-3(+) cells may be a valuable tool for studying early-stage human development and human reproductive medicine.

Tumor suppressor let-7 acts as a key regulator for pluripotency gene expression in Muse cells.

In embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), the expression of an RNA-binding pluripotency-relevant protein, LIN28, and the absence of its antagonist, the tumor-suppressor microRNA (miRNA) let-7, play a key role in maintaining pluripotency. Muse cells are non-tumorigenic pluripotent-like stem cells residing in the bone marrow, peripheral blood, and organ connective tissues as pluripotent surface marker SSEA-3(+). They express pluripotency genes, differentiate into triploblastic-lineage cells, and self-renew at the single cell level. Muse cells do not express LIN28 but do express let-7 at higher levels than in iPSCs. In Muse cells, we demonstrated that let-7 inhibited the PI3K-AKT pathway, leading to sustainable expression of the key pluripotency regulator KLF4 as well as its downstream genes, POU5F1, SOX2, and NANOG. Let-7 also suppressed proliferation and glycolysis by inhibiting the PI3K-AKT pathway, suggesting its involvement in non-tumorigenicity. Furthermore, the MEK/ERK pathway is not controlled by let-7 and may have a pivotal role in maintaining self-renewal and suppression of senescence. The system found in Muse cells, in which the tumor suppressor let-7, but not LIN28, tunes the expression of pluripotency genes, might be a rational cell system conferring both pluripotency-like properties and a low risk for tumorigenicity.

Phagocytosing differentiated cell-fragments is a novel mechanism for controlling somatic stem cell differentiation within a short time frame.

Stem cells undergo cytokine-driven differentiation, but this process often takes longer than several weeks to complete. A novel mechanism for somatic stem cell differentiation via phagocytosing 'model cells' (apoptotic differentiated cells) was found to require only a short time frame. Pluripotent-like Muse cells, multipotent mesenchymal stem cells (MSCs), and neural stem cells (NSCs) phagocytosed apoptotic differentiated cells via different phagocytic receptor subsets than macrophages. The phagocytosed-differentiated cell-derived contents (e.g., transcription factors) were quickly released into the cytoplasm, translocated into the nucleus, and bound to promoter regions of the stem cell genomes. Within 24 ~ 36 h, the cells expressed lineage-specific markers corresponding to the phagocytosed-differentiated cells, both in vitro and in vivo. At 1 week, the gene expression profiles were similar to those of the authentic differentiated cells and expressed functional markers. Differentiation was limited to the inherent potential of each cell line: triploblastic-, adipogenic-/chondrogenic-, and neural-lineages in Muse cells, MSCs, and NSCs, respectively. Disruption of phagocytosis, either by phagocytic receptor inhibition via small interfering RNA or annexin V treatment, impeded differentiation in vitro and in vivo. Together, our findings uncovered a simple mechanism by which differentiation-directing factors are directly transferred to somatic stem cells by phagocytosing apoptotic differentiated cells to trigger their rapid differentiation into the target cell lineage.

Adipose tissue-derived Muse cells promote autophagy and oxidative stress tolerance in human epidermal melanocytes.

To investigate the effect of human adipose tissue-derived multilineage-differentiating stress-enduring (Muse) cells on the oxidative stress injury of human epidermal melanocytes (HEMs) in vitro. HEMs were treated with H2O2 to establish an oxidative stress injury model and then were co-cultured with adipose tissue-derived Muse cells. Immunohistochemistry, flow cytometry and Western blotting were used to assess changes in autophagy flux, apoptosis, expression of melanin synthesis related proteins and proliferation of melanocytes. Our findings demonstrate that co-culture with Muse cells significantly increased the tolerance of HEMs to oxidative stress, enhanced autophagy flux and reduced apoptosis. The expression of proteins related to the formation of melanin increased as did cell proliferation. Treatment with the autophagy inhibitor, 3-methyladenine (3MA), partially counteracted the improvement of oxidative stress tolerance in melanocytes elicited by co-culture with Muse cells. Muse cells promote autophagy and oxidative stress tolerance of melanocytes.

Effects of human Muse cells on bladder inflammation, overactivity, and nociception in a chemically induced Hunner-type interstitial cystitis-like rat model.

INTRODUCTION AND HYPOTHESIS: We investigated the effects of locally administered human multilineage-differentiating stress enduring (Muse) cells, nontumorigenic pluripotent-like endogenous stem cells, on bladder tissues, function, and nociceptive behavior in a chemically induced Hunner-type interstitial cystitis (HIC)-like rat model without immunosuppressant. METHODS: Chemical cystitis was induced by intravesical instillation of 0.2 N hydrochloride (HCl) for 15 min in female F344 rats. SSEA-3+ Muse cells, SSEA-3- non-Muse cells or Hanks' balanced salt solution (HBSS; vehicle) were injected into the anterior and posterior bladder wall at each 1×104 cells/10 µl 6 h after HCl application. The sham group received HBSS without HCl instillation. Urinary frequency was assessed using metabolic cages, cystometrograms, nociceptive behavior, and histological analysis of the bladder and L6 spinal cord. RESULTS: Increases in urinary frequency and decreases in bladder capacity compared with the sham group were observed in the vehicle and non-Muse groups, but not in the Muse group, at 1 week. Significant increases in nociceptive behavior compared with the sham group and the expression of TNFα in the bladder and c-Fos in the bilateral dorsal horns of L6 spinal cord were also observed in the vehicle and non-Muse groups, whereas these changes were not seen in the Muse group at 1 week. Histological analysis exhibited a higher proportion of injected Muse cells remaining in the urothelial basal layer and lamina propria of the bladder than non-Muse cells until 4 weeks. CONCLUSIONS: Muse cell therapy could be a promising modality for treating HIC.

Intravenous injection of human multilineage-differentiating stress-enduring cells alleviates mouse severe acute pancreatitis without immunosuppressants.

INTRODUCTION: We examined the effect of intravenously injected human multilineage-differentiating stress-enduring (Muse) cells, non-tumorigenic endogenous reparative stem cells already used in clinical trials, on a severe acute pancreatitis (SAP) mouse model without immunosuppressants. METHODS: Human Muse cells (1.0 × 105 cells) collected from mesenchymal stem cells (MSCs) as SSEA-3(+) were injected into a C57BL/6 mouse model via the jugular vein 6 h after SAP-induction with taurocholate. The control group received saline or the same number of SSEA-3(-)-non-Muse MSCs. RESULTS: Edematous parameters, F4/80(+) macrophage infiltration and terminal deoxynucleotidyl transferase dUTP nick-end labeling positivity was the lowest and the number of proliferating endogenous pancreatic progenitors (CK18(+)/Ki67(+) cells) the highest in the Muse group among the three groups, with statistical significance, at 72 h. An enzyme-linked immunosorbent assay and quantitative polymerase chain reaction demonstrated that in vitro production of VEGF, HGF, IGF-1, and MMP-2, which are relevant to tissue protection, anti-inflammation, and anti-fibrosis, were higher in Muse cells than in non-Muse MSCs, particularly when cells were cultured in SAP mouse serum. Consistently, the pancreas of animals in the Muse group contained higher amounts of those factors according to Western blotting at 18 h than that in the non-Muse MSCs and control groups. CONCLUSIONS: Intravenous injection of human Muse cells was suggested to be effective for attenuating edema, inflammation and apoptosis in the acute phase of SAP.

Rescue from Stx2-Producing E. coli-Associated Encephalopathy by Intravenous Injection of Muse Cells in NOD-SCID Mice.

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic colitis, hemolytic uremic syndrome, and acute encephalopathies that may lead to sudden death or severe neurologic sequelae. Current treatments, including immunoglobulin G (IgG) immunoadsorption, plasma exchange, steroid pulse therapy, and the monoclonal antibody eculizumab, have limited effects against the severe neurologic sequelae. Multilineage-differentiating stress-enduring (Muse) cells are endogenous reparative non-tumorigenic stem cells that naturally reside in the body and are currently under clinical trials for regenerative medicine. When administered intravenously, Musecells accumulate to the damaged tissue, where they exert anti-inflammatory, anti-apoptotic, anti-fibrotic, and immunomodulatory effects, and replace damaged cells by differentiating into tissue-constituent cells. Here, severely immunocompromised non-obese diabetic/severe combined immunodeficiency (NOD-SCID) mice orally inoculated with 9 × 109 colony-forming units of STEC O111 and treated 48 h later with intravenous injection of 5 × 104 Muse cells exhibited 100% survival and no severe after-effects of infection. Suppression of granulocyte-colony-stimulating factor (G-CSF) by RNAi abolished the beneficial effects of Muse cells, leading to a 40% death and significant body weight loss, suggesting the involvement of G-CSF in the beneficial effects of Muse cells in STEC-infected mice. Thus, intravenous administration of Muse cells could be a candidate therapeutic approach for preventing fatal encephalopathy after STEC infection.

The evaluation of the safety and efficacy of intravenously administered allogeneic multilineage-differentiating stress-enduring cells in a swine hepatectomy model.

INTRODUCTION: Multilineage-differentiating stress-enduring (Muse) cells are non-tumorigenic endogenous pluripotent-like cells residing in the bone marrow that exert a tissue reparative effect by replacing damaged/apoptotic cells through spontaneous differentiation into tissue-constituent cells. Post-hepatectomy liver failure (PHLF) is a potentially fatal complication. The main purpose of this study was to evaluate the safety and efficiency of allogeneic Muse cell administration via the portal vein in a swine model of PHLF. METHODS: Swine Muse cells, collected from swine bone marrow-mesenchymal stem cells (MSCs) as SSEA-3(+) cells, were examined for their characteristics. Then, 1 × 107 allogeneic-Muse cells and allogeneic-MSCs and vehicle were injected via the portal vein in a 70% hepatectomy swine model. RESULTS: Swine Muse cells exhibited characteristics comparable to previously reported human Muse cells. Compared to the MSC and vehicle groups, the Muse group showed specific homing of the administered cells into the liver, resulting in improvements in the control of hyperbilirubinemia (P = 0.04), prothrombin international normalized ratio (P = 0.05), and suppression of focal necrosis (P = 0.04). Integrated Muse cells differentiated spontaneously into hepatocyte marker-positive cells. CONCLUSIONS: Allogeneic Muse cell administration may provide a reparative effect and functional recovery in a 70% hepatectomy swine model and thus may contribute to the treatment of PHLF.

Study of the protective effect on damaged intestinal epithelial cells of rat multilineage-differentiating stress-enduring (Muse) cells.

In this study, we determined whether multilineage-differentiating stress-enduring (Muse) cells exist in rat bone marrow and elucidated their effects on protection against the injury of intestinal epithelial cells associated with inflammation. Rat Muse cells were separated from bone marrow mesenchymal stem cells (BMMSCs) by trypsin-incubation stress. The group of cells maintained the characteristics of BMMSCs; however, there were high positive expression levels of stage-specific embryonic antigen-3 (SSEA-3; 75.6 ± 2.8%) and stage-specific embryonic antigen-1 (SSEA-1; 74.8 ± 3.1%), as well as specific antigens including Nanog, POU class 5 homeobox 1 (OCT 3/4), and SRY-box 2 (SOX 2). After inducing differentiation, α-fetoprotein (endodermal), α-smooth muscle actin and neurofilament medium polypeptide (ectodermal) were positive in Muse cells. Injuries of intestinal epithelial crypt cell-6 (IEC-6) and colorectal adenocarcinoma 2 (Caco-2) cells as models were induced by tumor necrosis factor-α stimulation in vitro. Muse cells exhibited significant protective effects on the proliferation and intestinal barrier structure, the underlying mechanisms of which were related to reduced levels of interleukin-6 (IL-6) and interferon-γ (IFN-γ), and the restoration of transforming growth factor-ß (TGF-ß) and IL-10 in the inflammation microenvironment. In summary, there were minimal levels of pluripotent stem cells in rat bone marrow, which exhibit similar properties to human Muse cells. Rat Muse cells could provide protection against damage to intestinal epithelial cells depending on their anti-inflammatory and immune regulatory functionality. Their functional impact was more obvious than that of BMMSCs.

Mobilized Muse Cells After Acute Myocardial Infarction Predict Cardiac Function and Remodeling in the Chronic Phase.

BACKGROUND: Multilineage differentiating stress-enduring (Muse) cells are SSEA3+and CD105+double-positive pluripotent-like stem cells. We aimed to examine the mobilization of Muse cells into peripheral blood after acute myocardial infarction (AMI) and their effects on left ventricular (LV) function and remodeling.Methods and Results:In 79 patients with AMI, 44 patients with coronary artery disease (CAD), and 64 normal subjects (Control), we measured the number of Muse cells in the peripheral blood by fluorescence-activated cell sorting. Muse cells were measured on days 0, 1, 7, 14, and 21 after AMI. Plasma sphingosine-1-phosphate (S1P) levels were measured. Cardiac echocardiography was performed in the acute (within 7 days) and chronic (6 months) phases of AMI. Muse cell number on day 1 was significantly higher in the AMI (276±137 cells/100 µL) than in the CAD (167±89 cells/100 µL) and Control (164±125 cells/100 µL) groups. Muse cell number peaked on day 1, and had gradually decreased on day 21. Muse cell number positively correlated with plasma S1P levels. Patients with a higher increase in the number of Muse cells in the peripheral blood but not those with a lower increase in number of Muse cells in the acute phase showed improved LV function and remodeling in the chronic phase. CONCLUSIONS: Endogenous Muse cells were mobilized into the peripheral blood after AMI. The number of Muse cells could be a predictor of prognosis in patients with AMI.

Acute Myocardial Infarction, Cardioprotection, and Muse Cells.

Acute myocardial infarction (AMI) is a common cause of morbidity and mortality worldwide. Severe MI leads to heart failure due to a marked loss of functional cardiomyocytes. First-line treatment for AMI is to reperfuse the occluded coronary artery by PCI as soon as possible. Besides PCI, there are several therapies to reduce the infarct size and improve the cardiac function and remodeling. These are drug therapies such as pharmacological pre- and postconditioning, cytokine therapies, and stem cell therapies. None of these therapies have been clinically developed as a standard treatment for AMI. Among many cell sources for stem cell therapies, the Muse cell is an endogenous non-tumorigenic pluripotent stem cell, which is able to differentiate into cells of all three germ layers from a single cell, suggesting that the Muse cell is a potential cell source for regenerative medicine. Endogenous Muse cell dynamics in the acute phase plays an important role in the prognosis of AMI patients; AMI patients with a higher number of Muse cells in the peripheral blood in the acute phase show more favorable improvement of the cardiac function and remodeling in the chronic phase, suggesting their innate reparative function for the heart. Intravenously administered exogenous Muse cells engrafted preferentially and efficiently to infarct border areas via the S1P-S1PR2 axis and differentiated spontaneously into working cardiomyocytes and vessels, showed paracrine effects, markedly reduced the myocardial infarct size, and delivered long-lasting improvement of the cardiac function and remodeling for 6 months. These findings suggest that Muse cells are reparative stem cells, and thus their clinical application is warranted.

Application of Muse Cell Therapy to Stroke.

Stroke is defined as a sudden onset of neurologic deficits arising from cerebrovascular complications. It is the second common cause of death around the world and the major cause of disability. Because brain is an organ with complicated neural networks and neurons are highly differentiated, it has been traditionally considered to possess a limited potential for regeneration. The number of stroke patients is increasing, and stroke represents a serious problem from the viewpoint of the national medical economy. Even with the current sophisticated treatments, more than half of stroke patient survivors remain disabled. Therefore, it is imperative to develop a new treatment for promoting functional recovery and repair of the lost neurological circuit. Multilineage-differentiating stress-enduring (Muse) cells are endogenous non-tumorigenic stem cells with pluripotency. After transplantation, Muse cells recognize the injured site through their specific receptor for damage signal, home preferentially into these tissues and spontaneously differentiate into tissue-compatible cells to replace the lost cells, and repair the tissue, delivering functional and structural regeneration. These properties are desirable for the treatment of strokes and advantageous compared to other stem cell therapies. Here, we describe the current status of stem cell therapies for stroke and future possibilities of Muse cell therapy.

Muse Cells and Ischemia-Reperfusion Lung Injury.

Ischemia-reperfusion injury (IRI) is one of the main causes of primary graft dysfunction that accounts for 25% of mortality after lung transplantation. Disruption of blood supply and subsequent reperfusion result in organ damage with activating innate and adaptive immune response, leading to inflammatory insults. The IRI after lung transplantation is primarily manifested by permeability pulmonary edema on the basis of pulmonary vascular endothelial cell injury as seen in acute respiratory distress syndrome (ARDS). Stem cells have potent anti-inflammatory and immunomodulatory properties through local paracrine mechanisms. The application of mesenchymal stem cells (MSCs) for ARDS as well as IRI in various organs, therefore, has been interested and extensively investigated in animal models with promising results. Furthermore, two recent clinical randomized, placebo-controlled pilot studies demonstrated that treatment of ARDS with MSCs appears to be safe and feasible.Muse cells are stress-tolerant and non-tumorigenic endogenous pluripotent-like stem cells. They comprise small proportions of cultured fibroblasts and MSCs and can be isolated from these populations. Muse cells are known to migrate to the damaged tissue after local or systemic administration, spontaneously differentiate into the tissue-compatible cells, and also secrete factors related to immunomodulation and tissue repair. We have recently shown the effect of Muse cells on ameliorating lung IRI in a rat model. With 2 h of warm ischemia and subsequent reperfusion on the left lung, the lung showed severe pulmonary edema. Administration of Muse cell through the left pulmonary artery immediately after reperfusion more significantly improved lung oxygenation capacity, compliance, and histological damage on days 1 and 3 after reperfusion compared with MSCs, and this was associated with higher expression levels of proteins related with anti-inflammation and tissue repair in the lung. Encouraging results of this study advocate further investigation of the ability of Muse cells to prevent and treat IRI after lung transplantation.

Investigating the Potential of Multilineage Differentiating Stress-Enduring Cells for Osteochondral Healing.

OBJECTIVE: Multilineage differentiating stress-enduring (Muse) cells, a pluripotent stem cell subset of mesenchymal stem cells (MSCs), have shown promise for various tissue repairs due to their stress tolerance and multipotent capabilities. We aimed to investigate the differentiation potential in vitro, the dynamics in vivo, and the reparative contribution of Muse cells to osteochondral lesions. DESIGN: Labeled MSCs were cultured and sorted into Muse and non-Muse (MSCs without Muse cells) groups. These cells were then formed into spheroids, and chondrogenic differentiation was assessed in vitro. Twenty-one immunocompromised mice were used as the in vivo models of osteochondral lesions. Live imaging, macroscopic evaluation, and histological and immunohistochemical analyses were conducted at the 4- and 8-week time points. RESULTS: Muse cell spheroids were formed, which were larger and stained more intensely with toluidine blue than non-Muse spheroids, indicating better chondrogenic differentiation. Live imaging confirmed luminescence in all 4-week model knees, but only in a few knees at 8 weeks, suggesting cell persistence. Macroscopically and histologically, no significant differences were observed between the Muse and non-Muse groups at 4 and 8 weeks; however, both groups showed better cartilage repair than that of the vehicle group at 8 weeks. No collagen type II generation was observed in the repaired tissues. CONCLUSION: The implantation of the spheroids of Muse and non-Muse cells resulted in better healing of osteochondral lesions than that of the controls, and Muse cells had a higher chondrogenic differentiation potential in vitro than non-Muse cells.

Human Muse cells isolated from preterm- and term-umbilical cord delivered therapeutic effects in rat bleomycin-induced lung injury model without immunosuppressant.

BACKGROUND: Bleomycin (BLM)-induced lung injury is characterized by mixed histopathologic changes with inflammation and fibrosis, such as observed in human patients with bronchopulmonary dysplasia, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease. Although no curative therapies for these lung diseases exist, stem cell therapy has emerged as a potential therapeutic option. Multilineage-differentiating stress-enduring (Muse) cells are endogenous pluripotent- and macrophage-like stem cells distributed in various adult and fetal tissues as stage-specific embryonic antigen-3-positive cells. They selectively home to damaged tissue by sensing sphingosine-1-phosphate and replace the damaged/apoptotic cells by in vivo differentiation. Clinical trials for some human diseases suggest the safety and therapeutic efficacy of intravenously injected human leukocyte antigen-mismatched allogenic Muse cells from adult bone marrow (BM) without immunosuppressant. Here, we evaluated the therapeutic effects of human Muse cells from preterm and term umbilical cord (UC), and adult BM in a rat BLM-induced lung injury model. METHODS: Rats were endotracheally administered BLM to induce lung injury on day 0. On day 3, human preterm UC-Muse, term UC-Muse, or adult BM-Muse cells were administered intravenously without immunosuppressants, and rats were subjected to histopathologic analysis on day 21. Body weight, serum surfactant protein D (SP-D) levels, and oxygen saturation (SpO2) were monitored. Histopathologic lung injury scoring by the Ashcroft and modified American Thoracic Society document scales, quantitative characterization of engrafted Muse cells, RNA sequencing analysis, and in vitro migration assay of infused Muse cells were performed. RESULTS: Rats administered preterm- and term-UC-Muse cells exhibited a significantly better recovery based on weight loss, serum SP-D levels, SpO2, and histopathologic lung injury scores, and a significantly higher rate of both Muse cell homing to the lung and alveolar marker expression (podoplanin and prosurfactant protein-C) than rats administered BM-Muse cells. Rats receiving preterm-UC-Muse cells showed statistically superior results to those receiving term-UC-Muse cells in many of the measures. These findings are thought to be due to higher expression of genes related to cell migration, lung differentiation, and cell adhesion. CONCLUSION: Preterm UC-Muse cells deliver more efficient therapeutic effects than term UC- and BM-Muse cells for treating BLM-induced lung injury in a rat model.

Multipotent/pluripotent stem cell populations in stromal tissues and peripheral blood: exploring diversity, potential, and therapeutic applications.

The concept of "stemness" incorporates the molecular mechanisms that regulate the unlimited self-regenerative potential typical of undifferentiated primitive cells. These cells possess the unique ability to navigate the cell cycle, transitioning in and out of the quiescent G0 phase, and hold the capacity to generate diverse cell phenotypes. Stem cells, as undifferentiated precursors endow with extraordinary regenerative capabilities, exhibit a heterogeneous and tissue-specific distribution throughout the human body. The identification and characterization of distinct stem cell populations across various tissues have revolutionized our understanding of tissue homeostasis and regeneration. From the hematopoietic to the nervous and musculoskeletal systems, the presence of tissue-specific stem cells underlines the complex adaptability of multicellular organisms. Recent investigations have revealed a diverse cohort of non-hematopoietic stem cells (non-HSC), primarily within bone marrow and other stromal tissue, alongside established hematopoietic stem cells (HSC). Among these non-HSC, a rare subset exhibits pluripotent characteristics. In vitro and in vivo studies have demonstrated the remarkable differentiation potential of these putative stem cells, known by various names including multipotent adult progenitor cells (MAPC), marrow-isolated adult multilineage inducible cells (MIAMI), small blood stem cells (SBSC), very small embryonic-like stem cells (VSELs), and multilineage differentiating stress enduring cells (MUSE). The diverse nomenclatures assigned to these primitive stem cell populations may arise from different origins or varied experimental methodologies. This review aims to present a comprehensive comparison of various subpopulations of multipotent/pluripotent stem cells derived from stromal tissues. By analysing isolation techniques and surface marker expression associated with these populations, we aim to delineate the similarities and distinctions among stromal tissue-derived stem cells. Understanding the nuances of these tissue-specific stem cells is critical for unlocking their therapeutic potential and advancing regenerative medicine. The future of stem cells research should prioritize the standardization of methodologies and collaborative investigations in shared laboratory environments. This approach could mitigate variability in research outcomes and foster scientific partnerships to fully exploit the therapeutic potential of pluripotent stem cells.

The Phoenix of stem cells: pluripotent cells in adult tissues and peripheral blood.

Pluripotent stem cells are defined as cells that can generate cells of lineages from all three germ layers, ectoderm, mesoderm, and endoderm. On the contrary, unipotent and multipotent stem cells develop into one or more cell types respectively, but their differentiation is limited to the cells present in the tissue of origin or, at most, from the same germ layer. Multipotent and unipotent stem cells have been isolated from a variety of adult tissues, Instead, the presence in adult tissues of pluripotent stem cells is a very debated issue. In the early embryos, all cells are pluripotent. In mammalians, after birth, pluripotent cells are maintained in the bone-marrow and possibly in gonads. In fact, pluripotent cells were isolated from marrow aspirates and cord blood and from cultured bone-marrow stromal cells (MSCs). Only in few cases, pluripotent cells were isolated from other tissues. In addition to have the potential to differentiate toward lineages derived from all three germ layers, the isolated pluripotent cells shared other properties, including the expression of cell surface stage specific embryonic antigen (SSEA) and of transcription factors active in the early embryos, but they were variously described and named. However, it is likely that they are part of the same cell population and that observed diversities were the results of different isolation and expansion strategies. Adult pluripotent stem cells are quiescent and self-renew at very low rate. They are maintained in that state under the influence of the "niche" inside which they are located. Any tissue damage causes the release in the blood of inflammatory cytokines and molecules that activate the stem cells and their mobilization and homing in the injured tissue. The inflammatory response could also determine the dedifferentiation of mature cells and their reversion to a progenitor stage and at the same time stimulate the progenitors to proliferate and differentiate to replace the damaged cells. In this review we rate articles reporting isolation and characterization of tissue resident pluripotent cells. In the attempt to reconcile observations made by different authors, we propose a unifying picture that could represent a starting point for future experiments.

Pathophysiology of cellulite: Possible involvement of selective endotoxemia.

The most relevant hallmarks of cellulite include a massive protrusion of superficial adipose tissue into the dermis, reduced expression of the extracellular glycoprotein fibulin-3, and an unusually high presence of MUSE cells in gluteofemoral white adipose tissue (gfWAT) that displays cellulite. Also typical for this condition is the hypertrophic nature of the underlying adipose tissue, the interaction of adipocytes with sweat glands, and dysfunctional lymph and blood circulation as well as a low-grade inflammation in the areas of gfWAT affected by cellulite. Here, we propose a new pathophysiology of cellulite, which connects this skin condition with selective accumulation of endogenous lipopolysaccharides (LPS) in gfWAT. The accumulation of LPS within a specific WAT depot has so far not been considered as a possible pathophysiological mechanism triggering localized WAT modifications, but may very well be involved in conditions such as cellulite and, secondary to that, lipedema.

Multilineage Differentiating Stress Enduring (Muse) Cells: A New Era of Stem Cell-Based Therapy.

Stem cell transplantation has recently demonstrated a significant therapeutic efficacy in various diseases. Multilineage-differentiating stress-enduring (Muse) cells are stress-tolerant endogenous pluripotent stem cells that were first reported in 2010. Muse cells can be found in the peripheral blood, bone marrow and connective tissue of nearly all body organs. Under basal conditions, they constantly move from the bone marrow to peripheral blood to supply various body organs. However, this rate greatly changes even within the same individual based on physical status and the presence of injury or illness. Muse cells can differentiate into all three-germ-layers, producing tissue-compatible cells with few errors, minimal immune rejection and without forming teratomas. They can also endure hostile environments, supporting their survival in damaged/injured tissues. Additionally, Muse cells express receptors for sphingosine-1-phosphate (S1P), which is a protein produced by damaged/injured tissues. Through the S1P-S1PR2 axis, circulating Muse cells can preferentially migrate to damaged sites following transplantation. In addition, Muse cells possess a unique immune privilege system, facilitating their use without the need for long-term immunosuppressant treatment or human leucocyte antigen matching. Moreover, they exhibit anti-inflammatory, anti-apoptotic and tissue-protective effects. These characteristics circumvent all challenges experienced with mesenchymal stem cells and induced pluripotent stem cells and encourage the wide application of Muse cells in clinical practice. Indeed, Muse cells have the potential to break through the limitations of current cell-based therapies, and many clinical trials have been conducted, applying intravenously administered Muse cells in stroke, myocardial infarction, neurological disorders and acute respiratory distress syndrome (ARDS) related to novel coronavirus (SARS-CoV-2) infection. Herein, we aim to highlight the unique biological properties of Muse cells and to elucidate the advantageous difference between Muse cells and other types of stem cells. Finally, we shed light on their current therapeutic applications and the major obstacles to their clinical implementation from laboratory to clinic.

Fetal Muse-based therapy prevents lethal radio-induced gastrointestinal syndrome by intestinal regeneration.

BACKGROUND: Human multilineage-differentiating stress enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be easily obtained from various adult or fetal tissues. Regenerative effects of Muse cells have been shown in some disease models. Muse cells specifically home in damaged tissues where they exert pleiotropic effects. Exposition of the small intestine to high doses of irradiation (IR) delivered after radiotherapy or nuclear accident results in a lethal gastrointestinal syndrome (GIS) characterized by acute loss of intestinal stem cells, impaired epithelial regeneration and subsequent loss of the mucosal barrier resulting in sepsis and death. To date, there is no effective medical treatment for GIS. Here, we investigate whether Muse cells can prevent lethal GIS and study how they act on intestinal stem cell microenvironment to promote intestinal regeneration. METHODS: Human Muse cells from Wharton's jelly matrix of umbilical cord (WJ-Muse) were sorted by flow cytometry using the SSEA-3 marker, characterized and compared to bone-marrow derived Muse cells (BM-Muse). Under gas anesthesia, GIS mice were treated or not through an intravenous retro-orbital injection of 50,000 WJ-Muse, freshly isolated or cryopreserved, shortly after an 18 Gy-abdominal IR. No immunosuppressant was delivered to the mice. Mice were euthanized either 24 h post-IR to assess early small intestine tissue response, or 7 days post-IR to assess any regenerative response. Mouse survival, histological stainings, apoptosis and cell proliferation were studied and measurement of cytokines, recruitment of immune cells and barrier functional assay were performed. RESULTS: Injection of WJ-Muse shortly after abdominal IR highly improved mouse survival as a result of a rapid regeneration of intestinal epithelium with the rescue of the impaired epithelial barrier. In small intestine of Muse-treated mice, an early enhanced secretion of IL-6 and MCP-1 cytokines was observed associated with (1) recruitment of monocytes/M2-like macrophages and (2) proliferation of Paneth cells through activation of the IL-6/Stat3 pathway. CONCLUSION: Our findings indicate that a single injection of a small quantity of WJ-Muse may be a new and easy therapeutic strategy for treating lethal GIS.