Single cell-derived clones from human adipose stem cells present different immunomodulatory properties

Short-Term Autophagy Preconditioning Upregulates the Expression of COX2 and PGE2 and Alters the Immune Phenotype of Human Adipose-Derived Stem Cells In Vitro

Human adipose-derived stem cells (hASCs) are potent modulators of inflammation and promising candidates for the treatment of inflammatory and autoimmune diseases. Strategies to improve hASC survival and immunoregulation are active areas of investigation. Autophagy, a homeostatic and stress-induced degradative pathway, plays a crucial role in hASC paracrine signaling—a primary mechanism of therapeutic action. Therefore, induction of autophagy with rapamycin (Rapa), or inhibition with 3-methyladenine (3-MA), was examined as a preconditioning strategy to enhance therapeutic efficacy. Following preconditioning, both Rapa and 3-MA-treated hASCs demonstrated preservation of stemness, as well as upregulated transcription of cyclooxygenase-2 (COX2) and interleukin-6 (IL-6). Rapa-ASCs further upregulated TNFα-stimulated gene-6 (TSG-6) and interleukin-1 beta (IL-1β), indicating additional enhancement of immunomodulatory potential. Preconditioned cells were then stimulated with the inflammatory cytokine interferon-gamma (IFNγ) and assessed for immunomodulatory factor production. Rapa-pretreated cells, but not 3-MA-pretreated cells, further amplified COX2 and IL-6 transcripts following IFNγ exposure, and both groups upregulated secretion of prostaglandin-E2 (PGE2), the enzymatic product of COX2. These findings suggest that a 4-h Rapa preconditioning strategy may bestow the greatest improvement to hASC expression of cytokines known to promote tissue repair and regeneration and may hold promise for augmenting the therapeutic potential of hASCs for inflammation-driven pathological conditions.

Comparison of the Characteristics of Breast Milk-derived Stem Cells with the Stem Cells Derived from the Other Sources: A Comparative Review

Breast milk (BrM) not only supplies nutrition, but it also contains a diverse population of cells. It has been estimated that up to 6% of the cells in human milk possess the characteristics of mesenchymal stem cells (MSC). Available data also indicate that these cells are multipotent and capable of self-renewal and differentiation with other cells. In this review, we have compared different characteristics, such as CD markers, differentiation capacity, and morphology of stem cells, derived from human breast milk (hBr-MSC) with human bone marrow (hBMSC), Wharton's jelly (WJMSC), and human adipose tissue (hADMSC). Through the literature review, it was revealed that human breast milk-derived stem cells specifically express a group of cell surface markers, including CD14, CD31, CD45, and CD86. Importantly, a group of markers, CD13, CD29, CD44, CD105, CD106, CD146, and CD166, were identified, which were common in the four sources of stem cells. WJMSC, hBMSC, hADMSC, and hBr-MSC are potently able to differentiate into the mesoderm, ectoderm, and endoderm cell lineages. The ability of hBr-MSCs todifferentiate into the neural stem cells, neurons, adipocyte, hepatocyte, chondrocyte, osteocyte, and cardiomyocytes has made these cells a promising source of stem cells in regenerative medicine, while isolation of stem cells from the commonly used sources, such as bone marrow, requires invasive procedures. Although autologous breast milk-derived stem cells are an accessible source for women who are in the lactation period, breast milk can be considered as a source of stem cells with high differentiation potential without any ethical concern.

Immunophenotypic characteristics of multipotent mesenchymal stromal cells that affect the efficacy of their use in the prevention of acute graft vs host disease

BACKGROUND

Multipotent mesenchymal stromal cells (MSCs) are widely used in the clinic due to their unique properties, namely, their ability to differentiate in all mesenchymal directions and their immunomodulatory activity. Healthy donor MSCs were used to prevent the development of acute graft vs host disease (GVHD) after allogeneic bone marrow transplantation (allo-BMT). The administration of MSCs to patients was not always effective. The MSCs obtained from different donors have individual characteristics. The differences between MSC samples may affect their clinical efficacy.

AIM

To study the differences between effective and ineffective MSCs.

METHODS

MSCs derived from the bone marrow of a hematopoietic stem cells donor were injected intravenously into allo-BMT recipients for GVHD prophylaxis at the moment of blood cell reconstitution. Aliquots of 52 MSC samples that were administered to patients were examined, and the same cells were cultured in the presence of peripheral blood mononuclear cells (PBMCs) from a third-party donor or treated with the pro-inflammatory cytokines IL-1β, IFN and TNF. Flow cytometry revealed the immunophenotype of the nontreated MSCs, the MSCs cocultured with PBMCs for 4 d and the MSCs exposed to cytokines. The proportions of CD25-, CD146-, CD69-, HLA-DR- and PD-1-positive CD4+ and CD8+ cells and the distribution of various effector and memory cell subpopulations in the PBMCs cocultured with the MSCs were also determined.

RESULTS

Differences in the immunophenotypes of effective and ineffective MSCs were observed. In the effective samples, the mean fluorescence intensity (MFI) of HLA-ABC, HLA-DR, CD105, and CD146 was significantly higher. After MSCs were treated with IFN or cocultured with PBMCs, the HLA-ABC, HLA-DR, CD90 and CD54 MFI showed a stronger increase in the effective MSCs, which indicated an increase in the immunomodulatory activity of these cells. When PBMCs were cocultured with effective MSCs, the proportions of CD4+ and CD8+central memory cells significantly decreased, and the proportion of CD8+CD146+ lymphocytes increased more than in the subpopulations of lymphocytes cocultured with MSC samples that were ineffective in the prevention of GVHD; in addition, the proportion of CD8+effector memory lymphocytes decreased in the PBMCs cocultured with the effective MSC samples but increased in the PBMCs cocultured with the ineffective MSC samples. The proportion of CD4+CD146+ lymphocytes increased only when cocultured with the inefficient samples.

CONCLUSION

For the first time, differences were observed between MSC samples that were effective for GVHD prophylaxis and those that were ineffective. Thus, it was shown that the immunomodulatory activity of MSCs depends on the individual characteristics of the MSC population.

Downregulation of microRNA‑143 promotes osteogenic differentiation of human adipose‑derived mesenchymal stem cells through the k‑Ras/MEK/ERK signaling pathway

MicroRNAs (miRNAs) are known to have regulatory roles in the osteogenic differentiation of various mesenchymal stem cells (MSCs), although their regulatory role on human adipose‑derived mesenchymal stem cells (hADSCs) remains unclear. The aim of the present study was to investigate the biological function and underlying molecular mechanism of miRNAs in regulating the osteogenic differentiation of hADSCs using microarray assay. hADSCs differentiated into osteoblasts under culture with osteogenic medium, with an increase observed in calcium deposits and alkaline phosphatase activity. The mRNA levels of bone sialoprotein, osteopontin and osteocalcin increased, whereas Runt‑related transcription factor‑2 expression decreased during osteogenic differentiation. In addition, miR‑143 was markedly downregulated during osteogenic differentiation, while miR‑143 overexpression inhibited and miR‑143 knockdown enhanced this process. miR‑143 overexpression also blocked extracellular signal‑regulated kinase 1/2 (ERK1/2) pathway activation, while miR‑143 inhibition enhanced it. The promoting effects of miR‑143 knockdown on the osteogenic differentiation of hADSCs were partly diminished by the mitogen‑activated protein kinase (MEK) inhibitors U0126 and PD98059. Bioinformatics analysis further revealed that miR‑143 targets k‑Ras and directly binds to the 3'‑untranslated region of its mRNA. Inhibition of miR‑143 enhanced the activation of the k‑Ras/MEK/ERK pathway during osteogenic differentiation, whereas miR‑143 overexpression had the opposite effect. Collectively, these results demonstrated that miR‑143 negatively regulates the osteogenic differentiation of hADSCs through the k‑Ras/MEK/ERK pathway, providing further insight into the underlying molecular mechanisms.

Assessment of Enrichment of Human Mesenchymal Stem Cells Based on Plasma and Mitochondrial Membrane Potentials

Background: Human mesenchymal stem cells (hMSCs) are utilized preclinically and clinically as a candidate cell therapy for a wide range of inflammatory and degenerative diseases. Despite promising results in early clinical trials, consistent outcomes with hMSC-based therapies have proven elusive in many of these applications. In this work, we attempt to address this limitation through the design of a stem cell therapy to enrich hMSCs for desired electrical and ionic properties with enhanced stemness and immunomodulatory/regenerative capacity. Materials and Methods: In this study, we sought to develop initial protocols to achieve electrically enriched hMSCs (EE-hMSCs) with distinct electrical states and assess the potential relationship with respect to hMSC state and function. We sorted hMSCs based on fluorescence intensity of tetramethylrhodamine ethyl ester (TMRE) and investigated phenotypic differences between the sorted populations. Results: Subpopulations of EE-hMSCs exhibit differential expression of genes associated with senescence, stemness, immunomodulation, and autophagy. EE-hMSCs with low levels of TMRE, indicative of depolarized membrane potential, have reduced mRNA expression of senescence-associated markers, and increased mRNA expression of autophagy and immunomodulatory markers relative to EE-hMSCs with high levels of TMRE (hyperpolarized). Conclusions : This work suggests that the utilization of EE-hMSCs may provide a novel strategy for cell therapies, enabling live cell enrichment for distinct phenotypes that can be exploited for different therapeutic outcomes.

DNA methylation profile of different clones of human adipose stem cells does not allow to predict their differentiation potential

Human adipose stem cells can differentiate into various mesodermic lineages, including adipogenic, osteogenic, chondrogenic, myogenic and endothelial pathways. In addition, these cells types possess immunomodulatory properties, potentially useful for autoimmune and autoinflammatory diseases. However, single-cell expanded clones have shown that the cells can present a variety of differentiation potential, which may be partly due to epigenetic differences among them. The objective of this study was to assess if DNA methylation plays a role in the differentiation potential observed between different cell clones obtained from the same donor. To this end, the methylation profile of five clonal cell lines of human adipose stem cells obtained by liposuction from two donors was analyzed. Previous reports demonstrated that cell lines 1.7 and 1.22 from Donor 1 and 3.5 from Donor 3 were adipogenic-osteogenic, but not cell lines 1.10 and 3.10. The genes analyzed were neuronal, endothelial, myogenic, osteogenic, adipogenic, extracellular matrix, cell cycle, cytoskeleton and metabolic enzymes. All clones analyzed in this study displayed a similar pattern of methylation in most of the gene families: 85.5% were hypomethylated genes and 14.5% hypermethylated. In conclusion, the methylation pattern of the 1113 genes studied in this report was not a consistent tool to identify the differentiation potential of human adipose stem cells.

Applicability of adipose-derived mesenchymal stem cells in treatment of patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is mainly characterized by insulin resistance (IR) and impaired insulin secretion. The chronic inflammatory process contributed to IR and could also hamper pancreatic β cell function. However, currently applied treatment cannot reverse β cell damage or alleviate inflammation. Mesenchymal stem cells (MSCs), the cell-based therapy for their self-renewable, differentiation potential, and immunosuppressive properties, have been demonstrated in displaying therapeutic effects in T2DM. Adipose-derived MSCs (AD-MSCs) attracted more attention due to less harvested inconvenience and ethical issues commonly accompany with bone marrow-derived MSCs (BM-MSCs) and fetal annex-derived MSCs. Both AD-MSC therapy studies and mechanism explorations in T2DM animals presented that AD-MSCs could translate to clinical application. However, hyperglycemia, hyperinsulinemia, and metabolic disturbance in T2DM are crucial for impairment of AD-MSC function, which may limit the therapeutical effects of MSCs. This review focuses on the outcomes and the molecular mechanisms of MSC therapies in T2DM which light up the hope of AD-MSCs as an innovative strategy to cure T2DM.

Diverse repertoire of human adipocyte subtypes develops from transcriptionally distinct mesenchymal progenitor cells

Single-cell sequencing technologies have revealed an unexpectedly broad repertoire of cells required to mediate complex functions in multicellular organisms. Despite the multiple roles of adipose tissue in maintaining systemic metabolic homeostasis, adipocytes are thought to be largely homogenous with only 2 major subtypes recognized in humans so far. Here we report the existence and characteristics of 4 distinct human adipocyte subtypes, and of their respective mesenchymal progenitors. The phenotypes of these distinct adipocyte subtypes are differentially associated with key adipose tissue functions, including thermogenesis, lipid storage, and adipokine secretion. The transcriptomic signature of "brite/beige" thermogenic adipocytes reveals mechanisms for iron accumulation and protection from oxidative stress, necessary for mitochondrial biogenesis and respiration upon activation. Importantly, this signature is enriched in human supraclavicular adipose tissue, confirming that these cells comprise thermogenic depots in vivo, and explain previous findings of a rate-limiting role of iron in adipose tissue browning. The mesenchymal progenitors that give rise to beige/brite adipocytes express a unique set of cytokines and transcriptional regulators involved in immune cell modulation of adipose tissue browning. Unexpectedly, we also find adipocyte subtypes specialized for high-level expression of the adipokines adiponectin or leptin, associated with distinct transcription factors previously implicated in adipocyte differentiation. The finding of a broad adipocyte repertoire derived from a distinct set of mesenchymal progenitors, and of the transcriptional regulators that can control their development, provides a framework for understanding human adipose tissue function and role in metabolic disease.

Improvement of Mesenchymal Stem Cell Immunomodulatory Properties by Heat-Killed Propionibacterium acnes via TLR2

Mesenchymal stem cells (MSCs) are an essential tool for regenerative medicine, which aims to develop new technologies to improve their effects to obtain useful transplantation results. MSC immunomodulatory role has been just demonstrated; however, how they react when they are stimulated by an adjuvant is poorly understood. Our group showed the adjuvant effect of killed Propionibacterium acnes (P. acnes) on hematopoietic stem cells. As these cells share the same MSCs bone marrow (BM) site and interact with each other, here we evaluated the P. acnes and its soluble polysaccharide (PS) effect on MSCs and their immunomodulatory role in a murine model of traumatic brain injury (TBI). The bacteria increased the absolute number of MSCs, including MSC subpopulations, and maintained MSC plasticity. P. acnes and PS enhanced MSC proliferation and improved their immunomodulatory effect. P. acnes-MSC and PS-MSC transplantation increased anti-inflammatory cytokine expression and diminished pro-inflammatory cytokine expression after injury. This effect seemed to be mediated via TLR2 since P. acnes-KOTLR2-MSC transplantation decreased TGF-β and IL-10 expression. Increasing in neural stem cells and neuroblasts after PS-MSC transplantation was also observed. The adjuvant effect of P. acnes is an alternative means of expanding MSCs and important to identify their subpopulations to know better their role under exogenous stimuli including inflammation resolution in an experimental model.

Differences of Clonogenic Mesenchymal Stem Cells on Immunomodulation of Lymphocyte Subsets

Mesenchymal stem cells (MSC) are a widely used population in cell therapy for their ability to differentiate into distinct tissues and more lately, for their immunomodulatory properties. However, the use of heterogeneous populations could be responsible for the nondesired outcomes reflected in the literature. Here, we analyse the different capacities of five one-cell-derived MSC clones to exert their immunomodulation ex vivo. We assessed proliferation assays in cocultures of MSC clones and purified cluster of differentiation (CD)3⁺, CD4⁺, or CD8⁺ lymphocytes; analysed the regulatory T (Treg) cells fold change rate; determined the effects on viability of peripheral blood mononuclear cells (PBMC); and also measured the coculture cytokine profiles (Th1/Th2). Conditioned media (CM) of different clones were also used to perform both proliferation assays and to analyse Treg fold change. The five clones analysed in this work were able to generate heterogeneous environments. Different clones inhibited proliferation of CD3⁺ and CD4⁺ lymphocytes, with different intensities. Surprisingly, all clones promoted proliferation of CD8⁺ lymphocytes. Different MSC clones and their CM were able to increase the number of Treg with different intensities. Finally, different clones also promoted different effects on the viability of PBMC treated with ultraviolet light. Considering all these data together, it seems that different clones, even from the same donor, can promote a wide spectrum of responses from anti-inflammatory to proinflammatory character. This fact may be important to standardise the design of personalized cell therapy protocols, thus diminishing the aforementioned undesired outcomes existing nowadays in this type of therapies.

Dad's Snoring May Have Left Molecular Scars in Your DNA: the Emerging Role of Epigenetics in Sleep Disorders

The sleep-wake cycle is a biological phenomena under the orchestration of neurophysiological, neurochemical, neuroanatomical, and genetical mechanisms. Moreover, homeostatic and circadian processes participate in the regulation of sleep across the light-dark period. Further complexity of the understanding of the genesis of sleep engages disturbances which have been characterized and classified in a variety of sleep-wake cycle disorders. The most prominent sleep alterations include insomnia as well as excessive daytime sleepiness. On the other side, several human diseases have been linked with direct changes in DNA, such as chromatin configuration, genomic imprinting, DNA methylation, histone modifications (acetylation, methylation, ubiquitylation or sumoylation, etc.), and activating RNA molecules that are transcribed from DNA but not translated into proteins. Epigenetic theories primarily emphasize the interaction between the environment and gene expression. According to these approaches, the environment to which mammals are exposed has a significant role in determining the epigenetic modifications occurring in chromosomes that ultimately would influence not only development but also the descendants' physiology and behavior. Thus, what makes epigenetics intriguing is that, unlike genetic variation, modifications in DNA are altered directly by the environment and, in some cases, these epigenetic changes may be inherited by future generations. Thus, it is likely that epigenetic phenomena might contribute to the homeostatic and/or circadian control of sleep and, possibly, have an undescribed link with sleep disorders. An exciting new horizon of research is arising between sleep and epigenetics since it represents the relevance of the study of how the genome learns from its experiences and modulates behavior, including sleep.

Comparative Analysis of Media and Supplements on Initiation and Expansion of Adipose-Derived Stem Cells

Adipose-derived stem cells (ASCs) are being tested in clinical trials related to cell-based regenerative therapies. Although most of the current expansion protocols for ASCs use fetal calf serum (FCS), xenogeneic-free medium supplements are greatly desired. This study aims to compare the effect of FCS, human platelet lysate (hPL), and a fully defined medium on the initiation and maintenance of ASC cultures. ASCs obtained from five donors were cultured in five different media: StemPro, Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% hPL, or α-minimum essential medium (A-MEM) supplemented with 5% hPL, 10% hPL, or 10% FCS. The effect of media on proliferation, colony-forming units (CFUs), attachment, and morphology was assessed along with cell size, granularity, and immunophenotype. StemPro greatly compromised the initiation of ASC cultures, which could not survive more than a few passages. Cells cultured in A-MEM proliferated at a faster rate than in DMEM, and hPL significantly enhanced cell size, granularity, and proliferation compared with FCS. All media except StemPro supported CFUs equally well. Analysis of surface markers revealed higher levels of CD73 and CD105 in FCS-cultured ASCs, whereas increased levels of CD146 were found in hPL-cultured cells. Multiparametric flow cytometric analysis performed after seven passages revealed the existence of four distinct ASC subpopulations, all positive for CD73, CD90, and CD105, which mainly differed by their expression of CD146 and CD271. Analysis of the different subpopulations might represent an important biological measure when assessing different medium formulations for a particular clinical application.

Ex vivo identification and characterization of a population of CD13(high) CD105(+) CD45(-) mesenchymal stem cells in human bone marrow

Introduction

Mesenchymal stem cells (MSCs) are multipotent cells capable of self-renewal and multilineage differentiation. Their multipotential capacity and immunomodulatory properties have led to an increasing interest in their biological properties and therapeutic applications. Currently, the definition of MSCs relies on a combination of phenotypic, morphological and functional characteristics which are typically evaluated upon in vitro expansion, a process that may ultimately lead to modulation of the immunophenotypic, functional and/or genetic features of these cells. Therefore, at present there is great interest in providing markers and phenotypes for direct in vivo and ex vivo identification and isolation of MSCs.

Methods

Multiparameter flow cytometry immunophenotypic studies were performed on 65 bone marrow (BM) samples for characterization of CD13^high CD105⁺ CD45^– cells. Isolation and expansion of these cells was performed in a subset of samples in parallel to the expansion of MSCs from mononuclear cells following currently established procedures. The protein expression profile of these cells was further assessed on (paired) primary and in vitro expanded BM MSCs, and their adipogenic, chondrogenic and osteogenic differentiation potential was also determined.

Results

Our results show that the CD13^high CD105⁺ CD45⁻ immunophenotype defines a minor subset of cells that are systematically present ex vivo in normal/reactive BM (n = 65) and that display immunophenotypic features, plastic adherence ability, and osteogenic, adipogenic and chondrogenic differentiation capacities fully compatible with those of MSCs. In addition, we also show that in vitro expansion of these cells modulates their immunophenotypic characteristics, including changes in the expression of markers currently used for the definition of MSCs, such as CD105, CD146 and HLA-DR.

Conclusions

BM MSCs can be identified ex vivo in normal/reactive BM, based on a robust CD13^high CD105⁺ and CD45⁻ immunophenotypic profile. Furthermore, in vitro expansion of these cells is associated with significant changes in the immunophenotypic profile of MSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0152-8) contains supplementary material, which is available to authorized users.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Placental mesenchymal stem cells of fetal origin deposit epigenetic alterations during long-term culture under serum-free condition

OBJECTIVE

Fetal placental mesenchymal stem cells (fPMSCs) have shown promising cell therapy potentials. However, their genetic and epigenetic stability during in vitro propagation has not been well studied. We thus interrogated the methylation alterations and tumorigenicity of fPMSCs after in vitro expansion using serum-free medium.

RESEARCH DESIGN AND METHODS

The properties of fPMSCs cultured in a serum-free medium at passage 3 and passage 8 were ascertained by determining their MSC markers, proliferative capacity, chromosomal stability, activity of global DNA methyltransferases and methylation profile. Their potential of malignant transformation was also evaluated in a severe combined immunodeficiency (SCID) murine model.

RESULTS

The fPMSCs could maintain their MSC characteristics but quickly reached a senescent state of proliferation during in vitro expansion. 246 genes with differential DNA methylation of promoters were identified, along with a significantly downregulated global DNA methyltransferase activity. The genes associated with aging and tumorigenesis had a significantly demethylated tendency over in vitro propagation. However, the deposition of epigenetic alterations did not translate into malignant transformation in SCID mice.

CONCLUSION

The fPMSCs cultured in serum-free medium have a tendency to deposit methylation modifications over in vitro expansion, therefore the detection of genetic and/or epigenetic alterations is necessary for fPMSCs before they are employed for clinical uses.

Obesity and weight loss could alter the properties of adipose stem cells?

The discovery that adipose tissue represents an interesting source of multipotent stem cells has led to many studies exploring the clinical potential of these cells in cell-based therapies. Recent advances in understanding the secretory capacity of adipose tissue and the role of adipokines in the development of obesity and associated disorders have added a new dimension to the study of adipose tissue biology in normal and diseased states. Subcutaneous adipose tissue forms the interface between the clinical application of regenerative medicine and the establishment of the pathological condition of obesity. These two facets of adipose tissue should be understood as potentially related phenomena. Because of the functional characteristics of adipose stem cells, these cells represent a fundamental tool for understanding how these two facets are interconnected and could be important for therapeutic applications. In fact, adipose tissue stem cells have multiple functions in obesity related to adipogenic, angiogenic and secretory capacities. In addition, we have also previously described a predominance of larger blood vessels and an adipogenic memory in the subcutaneous adipose tissue after massive weight loss subsequent to bariatric surgery (ex-obese patients). Understanding the reversibility of the behavior of adipose stem cells in obeses and in weight loss is relevant to both physiological studies and the potential use of these cells in regenerative medicine.

DNA methyltransferase inhibition accelerates the immunomodulation and migration of human mesenchymal stem cells

DNA methyltransferase (DNMT) inhibitors regulate target gene expression through epigenetic modifications, and these compounds have primarily been studied for cancer therapy or reprogramming. However, the effect of DNMT inhibitors on the immunomodulatory capacity of human mesenchymal stem cells (hMSCs) has not been investigated. In the present study, we treated hMSCs with 5-azacytidine (5-aza), a DNMT inhibitor, and confirmed that the inhibitory effects on mononuclear cell proliferation and cell migration toward activated T cells were increased. To identify the immunomodulatory factors stimulated through 5-aza treatment, we investigated the changes in promoter methylation patterns using methylation arrays and observed that the promoters of immunomodulatory factors, COX2 and PTGES, and migration-related factors, CXCR2 and CXCR4, were hypomethylated after 5-aza treatment. In addition, we observed that the COX2-PGE₂ pathway is one of the main pathways for the enhanced immunosuppressive activity of hMSCs through 5-aza treatment. We also determined that the migration of hMSCs toward ligands for CXCR2/CXCR4 was increased after 5-aza treatment. Moreover, using an experimental colitis model, we showed that 5-aza pre-treatment could enhance the therapeutic effect of MSCs against immune-related diseases.