Apoptosis in mesenchymal stromal cells activates an immunosuppressive secretome predicting clinical response in Crohn's disease.

In vivo apoptosis of human mesenchymal stromal cells (MSCs) plays a critical role in delivering immunomodulation. Yet, caspase activity not only mediates the dying process but also death-independent functions that may shape the immunogenicity of apoptotic cells. Therefore, a better characterization of the immunological profile of apoptotic MSCs (ApoMSCs) could shed light on their mechanistic action and therapeutic applications. We analyzed the transcriptomes of MSCs undergoing apoptosis and identified several immunomodulatory factors and chemokines dependent on caspase activation following Fas stimulation. The ApoMSC secretome inhibited human T cell proliferation and activation, and chemoattracted monocytes in vitro. Both immunomodulatory activities were dependent on the cyclooxygenase2 (COX2)/prostaglandin E2 (PGE2) axis. To assess the clinical relevance of ApoMSC signature, we used the peripheral blood mononuclear cells (PBMCs) from a cohort of fistulizing Crohn's disease (CD) patients who had undergone MSC treatment (ADMIRE-CD). Compared with healthy donors, MSCs exposed to patients' PBMCs underwent apoptosis and released PGE2 in a caspase-dependent manner. Both PGE2 and apoptosis were significantly associated with clinical responses to MSCs. Our findings identify a new mechanism whereby caspase activation delivers ApoMSC immunosuppression. Remarkably, such molecular signatures could implicate translational tools for predicting patients' clinical responses to MSC therapy in CD.

Gender and Observed Complexity in Palliative Home Care: A Prospective Multicentre Study Using the HexCom Model.

This study analyses gender differences in the complexity observed in palliative home care through a multicentre longitudinal observational study of patients with advanced disease treated by palliative home care teams in Catalonia (Spain). We used the HexCom model, which includes six dimensions and measures three levels of complexity: high (non-modifiable situation), medium (difficult) and low. Results: N = 1677 people, 44% women. In contrast with men, in women, cancer was less prevalent (64.4% vs. 73.9%) (p < 0.001), cognitive impairment was more prevalent (34.1% vs. 26.6%; p = 0.001) and professional caregivers were much more common (40.3% vs. 24.3%; p < 0.001). Women over 80 showed less complexity in the following subareas: symptom management (41.7% vs. 51,1%; p = 0.011), emotional distress (24.5% vs. 32.8%; p = 0.015), spiritual distress (16.4% vs. 26.4%; p = 0.001), socio-familial distress (62.7% vs. 70.1%; p = 0.036) and location of death (36.0% vs. 49.6%; p < 0.000). Men were more complex in the subareas of "practice" OR = 1.544 (1.25-1.90 p = 0.000) and "transcendence" OR = 1.52 (1.16-1.98 p = 0.002). Observed complexity is related to male gender in people over 80 years of age. Women over the age of 80 are remarkably different from their male counterparts, showing less complexity regarding care for their physical, psycho-emotional, spiritual and socio-familial needs.

Describing Complexity in Palliative Home Care Through HexCom: A Cross-Sectional, Multicenter Study.

BACKGROUND: Complexity has become a core issue in caring for patients with advanced disease and/or at the end-of-life. The Hexagon of Complexity (HexCom) is a complexity assessment model in the process of validation in health-care settings. Our objective is to use the instrument to describe differences in complexity across disease groups in specific home care for advanced disease and/or at the end-of-life patients, both in general and as relates to each domain and subdomain. METHODS: Cross-sectional study of home care was conducted in Catalonia. The instrument includes 6 domains of needs (clinical, psychological/emotional, social/family, spiritual, ethical, and death-related), 4 domains of resources (intrapersonal, interpersonal, transpersonal, and practical), and 3 levels of complexity (High (H), Moderate (M), and Low (L)). Interdisciplinary home care teams assessed and agreed on the level of complexity for each patient. RESULTS: Forty-three teams participated (74.1% of those invited). A total of 832 patients were assessed, 61.4% of which were cancer patients. Moderate complexity was observed in 385 (47.0%) cases and high complexity in 347 (42.4%). The median complexity score was 51 for cancer patients and 23 for patients with dementia (p<0.001). We observed the highest level of complexity in the social/family domain. Patients/families most frequently used interpersonal resources (80.5%). CONCLUSIONS: This study sheds light on the high-intensity work of support teams, the importance of the social/family domain and planning the place of death, substantial differences in needs and resources across disease groups, and the importance of relationship wellbeing at the end-of-life.

Dissecting Allo-Sensitization After Local Administration of Human Allogeneic Adipose Mesenchymal Stem Cells in Perianal Fistulas of Crohn's Disease Patients.

Adipose mesenchymal stem cells (ASC) are considered minimally immunogenic. This is due to the low expression of human leukocyte antigens I (HLA-I), lack of HLA-II expression and low expression of co-stimulatory molecules such as CD40 and CD80. The low rate of observed immunological rejection as well as the immunomodulatory qualities, position ASC as a promising cell-based therapy for the treatment of a variety of inflammatory indications. Yet, few studies have addressed relevant aspects of immunogenicity such as ASC donor-to-patient HLA histocompatibility or assessment of immune response triggered by ASC administration, particularly in the cases of presensitization. The present study aims to assess allo-immune responses in a cohort of Crohn's disease patients administered with allogeneic ASC (darvadstrocel formerly Cx601) for the treatment of complex perianal fistulas. We identified donor-specific antibodies (DSA) generation in a proportion of patients and observed that patients showing preexisting immunity were prone to generating DSA after allogeneic therapy. Noteworthy, naïve patients generating DSA at week 12 (W12) showed a significant reduction in DSA titer at week 52 (W52), whereas DSA titer was reduced in pre-sensitized patients only with no specificities against the donor administered. Remarkably, we did not observe any correlation of DSA generation with ASC therapeutic efficacy. In vitro complement-dependent cytotoxicity (CDC) studies have revealed limited cytotoxic levels based upon HLA-I expression and binding capacity even in pro-inflammatory conditions. We sought to identify CDC coping mechanisms contributing to the limited cytotoxic killing observed in ASC in vitro. We found that ASC express membrane-bound complement regulatory proteins (mCRPs) CD55, CD46, and CD59 at basal levels, with CD46 more actively expressed in pro-inflammatory conditions. We demonstrated that CD46 is a main driver of CDC signaling; its depletion significantly enhances sensitivity of ASC to CDC. In summary, despite relatively high clearance, DSA generation may represent a major challenge for allogeneic cell therapy management. Sensitization may be a significant concern when evaluating re-treatment or multi-donor trials. It is still unknown whether DSA generation could potentially be the consequence of donor-to-patient interaction and, therefore, subsequently link to efficacy or biological activity. Lastly, we propose that CDC modulators such as CD46 could be used to ultimately link CDC specificity with allogeneic cell therapy efficacy.

Human cardiac stem cells inhibit lymphocyte proliferation through paracrine mechanisms that correlate with indoleamine 2,3-dioxygenase induction and activity.

Transplantation of allogeneic human cardiac/stem progenitor cells (hCSCs) is currently being tested in several phase I/II clinical trials as a novel and promising therapy for restoration of myocardial tissue function in acute myocardial infarction (AMI) patients. Previous findings demonstrate that these cells have an immune suppressive profile interacting with different populations from the immune system, resulting in overall attenuation of myocardial inflammation. However, transplanted hCSCs are still recognized and cleared from the injured site, impairing long retention times in the tissue that could translate into a higher clinical benefit.In this work, through modeling allogeneic hCSC/T lymphocyte interaction in vitro by direct contact, transwell inserts, and hCSC conditioned medium, our results demonstrate that hCSCs exert an immune-suppressive effect on T lymphocyte proliferation not only through the previously described cell contact-dependent programmed cell death-1 (PD1)/programmed death ligand-1 (PDL-1) axis but also through a paracrine mechanism associated with indoleamine 2,3-dioxygenase (IDO) enzyme-mediated tryptophan metabolism. Such findings constitute a step forward in better understanding the mechanisms of action of transplanted hCSCs in allogeneic settings.

Safety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With ST-Segment Elevation Myocardial Infarction and Left Ventricular Dysfunction.

RATIONALE: Allogeneic cardiac stem cells (AlloCSC-01) have shown protective, immunoregulatory, and regenerative properties with a robust safety profile in large animal models of heart disease. OBJECTIVE: To investigate the safety and feasibility of early administration of AlloCSC-01 in patients with ST-segment-elevation myocardial infarction. METHODS AND RESULTS: CAREMI (Safety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With STEMI and Left Ventricular Dysfunction) was a phase I/II multicenter, randomized, double-blind, placebo-controlled trial in patients with ST-segment-elevation myocardial infarction, left ventricular ejection fraction ≤45%, and infarct size ≥25% of left ventricular mass by cardiac magnetic resonance, who were randomized (2:1) to receive AlloCSC-01 or placebo through the intracoronary route at days 5 to 7. The primary end point was safety and included all-cause death and major adverse cardiac events at 30 days (all-cause death, reinfarction, hospitalization because of heart failure, sustained ventricular tachycardia, ventricular fibrillation, and stroke). Secondary safety end points included major adverse cardiac events at 6 and 12 months, adverse events, and immunologic surveillance. Secondary exploratory efficacy end points were changes in infarct size (percentage of left ventricular mass) and indices of ventricular remodeling by magnetic resonance at 12 months. Forty-nine patients were included (92% male, 55±11 years), 33 randomized to AlloCSC-01 and 16 to placebo. No deaths or major adverse cardiac events were reported at 12 months. One severe adverse events in each group was considered possibly related to study treatment (allergic dermatitis and rash). AlloCSC-01 elicited low levels of donor-specific antibodies in 2 patients. No immune-related adverse events were found, and no differences between groups were observed in magnetic resonance-based efficacy parameters at 12 months. The estimated treatment effect of AlloCSC-01 on the absolute change from baseline in infarct size was -2.3% (95% confidence interval, -6.5% to 1.9%). CONCLUSIONS: AlloCSC-01 can be safely administered in ST-segment-elevation myocardial infarction patients with left ventricular dysfunction early after revascularization. Low immunogenicity and absence of immune-mediated events will facilitate adequately powered studies to demonstrate their clinical efficacy in this setting. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov . Unique identifier: NCT02439398.

Comparative Analysis between the In Vivo Biodistribution and Therapeutic Efficacy of Adipose-Derived Mesenchymal Stromal Cells Administered Intraperitoneally in Experimental Colitis.

Mesenchymal stem cells (MSCs) have emerged as a promising treatment for inflammatory diseases. The immunomodulatory effect of MSCs takes place both by direct cell-to-cell contact and by means of soluble factors that leads to an increased accumulation of regulatory immune cells at the sites of inflammation. Similar efficacy of MSCs has been described regardless of the route of administration used, the inflammation conditions and the major histocompatibility complex context. These observations raise the question of whether the migration of the MSCs to the inflamed tissues is a pre-requisite to achieve their beneficial effect. To address this, we examined the biodistribution and the efficacy of intraperitoneal luciferase-expressing human expanded adipose-derived stem cells (Luci-eASCs) in a mouse model of colitis. Luci-eASC-infused mice were stratified according to their response to the Luci-eASC treatment. According to the stratification criteria, there was a tendency to increase the bioluminescence signal in the intestine at the expense of a decrease in the bioluminescence signal in the liver in the "responder" mice. These data thus suggest that the accumulation of the eASCs to the inflamed tissues is beneficial for achieving an optimal modulation of inflammation.

Human Cardiac-Derived Stem/Progenitor Cells Fine-Tune Monocyte-Derived Descendants Activities toward Cardiac Repair.

Cardiac repair following MI relies on a finely regulated immune response involving sequential recruitment of monocytes to the injured tissue. Monocyte-derived cells are also critical for tissue homeostasis and healing process. Our previous findings demonstrated the interaction of T and natural killer cells with allogeneic human cardiac-derived stem/progenitor cells (hCPC) and suggested their beneficial effect in the context of cardiac repair. Therefore, we investigated here whether monocytes and their descendants could be also modulated by allogeneic hCPC toward a repair/anti-inflammatory phenotype. Through experimental in vitro assays, we assessed the impact of allogeneic hCPC on the recruitment, functions and differentiation of monocytes. We found that allogeneic hCPC at steady state or under inflammatory conditions can incite CCL-2/CCR2-dependent recruitment of circulating CD14+CD16- monocytes and fine-tune their activation toward an anti-inflammatory profile. Allogeneic hCPC also promoted CD14+CD16- monocyte polarization into anti-inflammatory/immune-regulatory macrophages with high phagocytic capacity and IL10 secretion. Moreover, hCPC bended the differentiation of CD14+CD16- monocytes to dendritic cells (DCs) toward anti-inflammatory macrophage-like features and impaired their antigen-presenting function in favor of immune-modulation. Collectively, our results demonstrate that allogeneic hCPC could reshape monocytes, macrophages as well as DCs responses by favoring their anti-inflammatory/tolerogenic activation/polarization. Thereby, therapeutic allogeneic hCPC might also contribute to post-infarct myocardial healing by modeling the activities of monocytes and their derived descendants.

Biodistribution and Efficacy of Human Adipose-Derived Mesenchymal Stem Cells Following Intranodal Administration in Experimental Colitis.

Mesenchymal stem cells (MSCs) have a large potential in cell therapy for treatment of inflammatory and autoimmune diseases, thanks to their immunomodulatory properties. The encouraging results in animal models have initiated the translation of MSC therapy to clinical trials. In cell therapy protocols with MSCs, administered intravenously, several studies have shown that a small proportion of infused MSCs can traffic to the draining lymph nodes (LNs). This is accompanied with an increase of different types of regulatory immune cells in the LNs, suggesting the importance of migration of MSCs to the LNs in order to contribute to immunomodulatory response. Intranodal (IN), also referred as intralymphatic, injection of cells, like dendritic cells, is being proposed in the clinic for the treatment of cancer and allergy, showing that this route of administration is clinically safe and efficient. In this study, we investigated, for the first time, the biodistribution and the efficacy of Luciferase+ adipose-derived MSCs (Luci-eASCs), infused through the inguinal LNs (iLNs), in normal mice and in inflamed mice with colitis. Most of the Luci-eASCs remain in the iLNs and in the adipose tissue surrounding the inguinal LNs. A small proportion of Luci-eASCs can migrate to other locations within the lymphatic system and to other tissues and organs, having a preferential migration toward the intestine in colitic mice. Our results show that the infused Luci-eASCs protected 58% of the mice against induced colitis. Importantly, a correlation between the response to eASC treatment and a higher accumulation of eASCs in popliteal, parathymic, parathyroid, and mesenteric LNs were found. Altogether, these results suggest that IN administration of eASCs is feasible and may represent an effective strategy for cell therapy protocols with human adipose-derived MSCs in the clinic for the treatment of immune-mediated disorders.

Intralymphatic Administration of Adipose Mesenchymal Stem Cells Reduces the Severity of Collagen-Induced Experimental Arthritis.

Mesenchymal stem cells (MSCs) are multipotent stromal cells with immunomodulatory properties. They have emerged as a very promising treatment for autoimmunity and inflammatory diseases such as rheumatoid arthritis. Previous studies have demonstrated that MSCs, administered systemically, migrate to lymphoid tissues associated with the inflammatory site where functional MSC-induced immune cells with a regulatory phenotype were increased mediating the immunomodulatory effects of MSCs. These results suggest that homing of MSCs to the lymphatic system plays an important role in the mechanism of action of MSCs in vivo. Thus, we hypothesized that direct intralymphatic (IL) (also referred as intranodal) administration of MSCs could be an alternative and effective route of administration for MSC-based therapy. Here, we report the feasibility and efficacy of the IL administration of human expanded adipose mesenchymal stem cells (eASCs) in a mouse model of collagen-induced arthritis (CIA). IL administration of eASCs attenuated the severity and progression of arthritis, reduced bone destruction and increased the levels of regulatory T cells (CD25+Foxp3+CD4+ cells) and Tr1 cells (IL10+CD4+), in spleen and draining lymph nodes. Taken together, these results indicate that IL administration of eASCs is very effective in modulating established CIA and may represent an alternative treatment modality for cell therapy with eASCs.

Intravenous administration of expanded allogeneic adipose-derived mesenchymal stem cells in refractory rheumatoid arthritis (Cx611): results of a multicentre, dose escalation, randomised, single-blind, placebo-controlled phase Ib/IIa clinical trial.

OBJECTIVES: To evaluate the safety and tolerability of the intravenous administration of Cx611, a preparation of allogeneic expanded adipose-derived stem cells (eASCs), in patients with refractory rheumatoid arthritis (RA), as well as to obtain preliminary clinical efficacy data in this population. METHODS: It is a multicentre, dose escalation, randomised, single-blind (double-blind for efficacy), placebo-controlled, phase Ib/IIa clinical trial. Patients with active refractory RA (failure to at least two biologicals) were randomised to receive three intravenous infusions of Cx611: 1 million/kg (cohort A), 2 million/kg (cohort B), 4 million/kg (cohort C) or placebo, on days 1, 8 and 15, and they were followed for therapy assessment for 24 weeks. RESULTS: Fifty-three patients were treated (20 in cohort A, 20 in cohort B, 6 in cohort C and 7 in placebo group). A total of 141 adverse events (AEs) were reported. Seventeen patients from the group A (85%), 15 from the group B (75%), 6 from the group C (100%) and 4 from the placebo group (57%) experienced at least one AE.Eight AEs from 6 patients were grade 3 in intensity (severe), 5 in cohort A (lacunar infarction, diarrhoea, tendon rupture, rheumatoid nodule and arthritis), 2 in cohort B (sciatica and RA) and 1 in the placebo group (asthenia). Only one of the grade 3 AEs was serious (the lacunar infarction). American College of Rheumatology 20 responses for cohorts A, B, C and placebo were 45%, 20%, 33% and 29%, respectively, at month 1, and 25%, 15%, 17% and 0%, respectively, at month 3. CONCLUSIONS: The intravenous infusion of Cx611 was in general well tolerated, without evidence of dose-related toxicity at the dose range and time period studied. In addition, a trend for clinical efficacy was observed. These data, in our opinion, justify further investigation of this innovative therapy in patients with RA. TRIAL REGISTRATION NUMBERS: EudraCT: 2010-021602-37; NCT01663116; Results.

Adipose-derived mesenchymal stromal cells modulate experimental autoimmune arthritis by inducing an early regulatory innate cell signature.

Modulation of innate immune responses in rheumatoid arthritis and other immune-mediated disorders is of critical importance in the clinic since a growing body of information has shown the key contribution of dysregulated innate responses in the progression of the disease. Mesenchymal stromal cells (MSCs) are the focus of intensive efforts worldwide due to their key role in tissue regeneration and modulation of inflammation. In this study, we define innate immune responses occurring during the early course of treatment with a single dose of expanded adipose-derived MSCs (eASCs) in established collagen-induced arthritis. eASCs delay the progression of the disease during the early phase of the disease. This is accompanied by a transient induction of Ly6C+ monocytes that differentiate into IL10+F4/80+ cells in arthritic mice. Strikingly, the induced IL10+F4/80+ myeloid cells preferentially accumulated in the draining lymph nodes. This effect was accompanied with a concomitant declining of their frequencies in the spleens. Our results show that eASCs attenuate the arthritic process by inducing an early innate cell signature that involves a transient induction of Ly6C+ monocytes in periphery that differentiate into IL10+F4/80+ macrophages. Our findings demonstrate that early regulatory innate cell responses, involving the monocyte compartment, are targeted by the eASCs during the onset of collagen-induced inflammation.

Estudio comparativo del aislamiento de exosomas derivados de células madre mesenquimales humanas para uso clínico / Comparative study of isolated human mesenchymal stem cell derived exosomes for clinical use / Estudo comparativo do isolamento de exossomos derivados de celulas-tronco mesenquimais humanas para uso clinico

Los exosomas son microvesículas derivadas de la exocitosis que son liberados al espacio extracelular. Las funciones de los exosomas dependen en gran medida de la célula de la cual provienen. Los exosomas derivados de células madre mesenquimales (Mesenchymal Stem Cells, MSCs), al igual que las células de origen, poseen un enorme potencial terapéutico que favorece la regeneración tisular y reduce la inflamación. Los prometedores resultados preclínicos que emplean estos exosomas han abierto las puertas a la futura aplicación clínica de estas vesículas. El diseño de nuevos protocolos que permitan el aislamiento de exosomas para su aplicación clínica es una necesidad actual teniendo en cuenta el enorme interés que ha surgido a raíz de los prometedores resultados en ensayos preclínicos. El objetivo de este trabajo ha sido comparar, en términos de rendimiento, tamaño y pureza, diferentes métodos de aislamiento de exosomas a partir de MSCs humanas. Los resultados obtenidos demuestran que el uso de filtros concentradores para sobrenadantes de cultivos podría ser una alternativa a los protocolos convencionales basados en la ultracentrifugación. Los resultados de este trabajo permiten orientar en el diseño de protocolos para la obtención de exosomas derivados de MSCs en grado clínico...

Human Adipose-Derived Mesenchymal Stem Cells Modulate Experimental Autoimmune Arthritis by Modifying Early Adaptive T Cell Responses.

Mesenchymal stem cells (MSCs) are multipotent stromal cells with immunosuppressive properties. They have emerged as a very promising treatment for autoimmunity and inflammatory diseases such as rheumatoid arthritis. Recent data have identified that GM-CSF-expressing CD4 T cells and Th17 cells have critical roles in the pathogenesis of arthritis and other inflammatory diseases. Although many studies have demonstrated that MSCs can either prevent or suppress inflammation, no studies have addressed their modulation on GM-CSF-expressing CD4 T cells and on the plasticity of Th17 cells. To address this, a single dose of human expanded adipose-derived mesenchymal stem cells (eASCs) was administered to mice with established collagen-induced arthritis. A beneficial effect was observed soon after the infusion of the eASCs as shown by a significant decrease in the severity of arthritis. This was accompanied by reduced number of pathogenic GM-CSF(+) CD4(+) T cells in the spleen and peripheral blood and by an increase in the number of different subsets of regulatory T cells like FOXP3(+) CD4(+) T cells and IL10(+) IL17(-) CD4(+) T cells in the draining lymph nodes (LNs). Interestingly, increased numbers of Th17 cells coexpressing IL10 were also found in draining LNs. These results demonstrate that eASCs ameliorated arthritis after the onset of the disease by reducing the total number of pathogenic GM-CSF(+) CD4(+) T and by increasing the number of different subsets of regulatory T cells in draining LNs, including Th17 cells expressing IL10. All these cellular responses, ultimately, lead to the reestablishment of the regulatory/inflammatory balance in the draining LNs.

T Lymphocyte Prestimulation Impairs in a Time-Dependent Manner the Capacity of Adipose Mesenchymal Stem Cells to Inhibit Proliferation: Role of Interferon γ, Poly I:C, and Tryptophan Metabolism in Restoring Adipose Mesenchymal Stem Cell Inhibitory Effect.

The immunomodulatory properties of mesenchymal stem/stromal cells (MSCs) make them an attractive therapeutic tool to treat chronic inflammatory diseases, such as rheumatoid arthritis or Crohn's disease. These indications are characterized by a chronic activation of immune cells that perpetuates the disease. In vitro, when adipose mesenchymal stem cells (ASCs) are cultured with T lymphocytes at the time of stimulation, their proliferation is inhibited. However, these experimental settings do not necessarily fit with what ASCs will face in inflammatory conditions in vivo, where ASCs will likely encounter and interact with already activated immune cells which might affect their immunomodulatory capacity. In most in vitro studies, MSCs have been cultured with peripheral blood mononuclear cells at the time of lymphocyte stimulation and information about the interaction between MSCs and prestimulated lymphocytes in vitro is scarce. Therefore, a better understanding of the capacity of MSCs to modulate the responses of preactivated immune cells is needed. In this study we focused on the effects of ASCs on prestimulated lymphocytes and systematically investigated the potential mechanisms involved. We report that prestimulation of T lymphocytes 48 h before the coculture with ASCs impairs the capacity of ASCs to inhibit proliferation. Preactivation of ASCs with interferon γ or the toll-like receptor ligand Poly I:C, but not other stimuli tested, enhanced the ability to inhibit the proliferation of 48 h-stimulated T lymphocytes. The inhibitory effect of ASCs was shown to be time dependent and mediated through the actual magnitude of tryptophan degradation by indoleamine 2,3-dioxygenase.

Mesenchymal stem cells as a therapeutic tool to treat sepsis.

Sepsis is a clinical syndrome caused by a deregulated host response to an infection. Sepsis is the most frequent cause of death in hospitalized patients. Although knowledge of the pathogenesis of sepsis has increased substantially during the last decades, attempts to design effective and specific therapies targeting components of the derailed host response have failed. Therefore, there is a dramatic need for new and mechanistically alternative therapies to treat this syndrome. Based on their immunomodulatory properties, adult mesenchymal stem or stromal cells (MSCs) can be a novel therapeutic tool to treat sepsis. Indeed, MSCs reduce mortality in experimental models of sepsis by modulating the deregulated inflammatory response against bacteria through the regulation of multiple inflammatory networks, the reprogramming of macrophages and neutrophils towards a more anti-inflammatory phenotype and the release of anti-microbial peptides. This report will review the current knowledge on the effects of MSC treatment in preclinical experimental small animal models of sepsis.

Tryptophan concentration is the main mediator of the capacity of adipose mesenchymal stromal cells to inhibit T-lymphocyte proliferation in vitro.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have immunomodulatory properties that are mediated by cell-to-cell interactions and paracrine effects through soluble factors, among which tryptophan (Trp) conversion into kynurenine (Kyn) through the enzymatic activity of indoleamine 2,3-dioxygenase has been proven to be of special relevance. However, the respective role of Trp depletion and/or Kyn accumulation on the inhibition of T-cell proliferation by MSCs remains unclear. METHODS: The effect of supplementation with increasing concentrations of Trp on the capacity of MSCs to inhibit T-lymphocyte proliferation in vitro was investigated. RESULTS: We report that Trp supplementation impairs the capacity of adipose mesenchymal stromal cells (ASCs) to inhibit T-cell proliferation, despite the accumulation of very high concentrations of Kyn in the medium (>200 µmol/L). Moreover, Trp supplementation after 72 h of peripheral blood mononuclear cell:ASC co-culture, once the inhibitory effect of ASCs was established, reverted ASC inhibition and restored T-cell proliferation. Addition to stimulated lymphocytes of Kyn inhibited T proliferation in 3 of 10 peripheral blood mononuclear cell donors, but at different concentrations, suggesting that sensitivity of lymphocytes to Kyn might be donor-dependent. CONCLUSIONS: Our results confirm the relevance of Trp metabolism as a key mediator of the immunomodulatory properties of ASCs and clarify the respective roles of the Trp/Kyn balance.

Human adipose tissue-derived mesenchymal stromal cells promote B-cell motility and chemoattraction.

BACKGROUND AIMS: Mesenchymal stromal cells hold special interest for cell-based therapy because of their tissue-regenerative and immunosuppressive abilities. B-cell involvement in chronic inflammatory and autoimmune pathologies makes them a desirable target for cell-based therapy. Mesenchymal stromal cells are able to regulate B-cell function; although the mechanisms are little known, they imply cell-to-cell contact. METHODS: We studied the ability of human adipose tissue-derived mesenchymal stromal cells (ASCs) to attract B cells. RESULTS: We show that ASCs promote B-cell migration through the secretion of chemotactic factors. Inflammatory/innate signals do not modify ASC capacity to mediate B-cell motility and chemotaxis. Analysis of a panel of B cell-related chemokines showed that none of them appeared to be responsible for B-cell motility. Other ASC-secreted factors able to promote cell motility and chemotaxis, such as the cytokine interleukin-8 and prostaglandin E2, did not appear to be implicated. CONCLUSIONS: We propose that ASC promotion of B-cell migration by undefined secreted factors is crucial for ASC regulation of B-cell responses.

Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Fourth Meeting: lessons learned from first clinical trials.

The Fourth Expert Meeting of the Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Consortium took place in Barcelona on October 19 and 20, 2012. This meeting focused on the translation of preclinical data into early clinical settings. This position paper highlights the main topics explored on the safety and efficacy of mesenchymal stem cells as a therapeutic agent in solid organ transplantation and emphasizes the issues (proper timing, concomitant immunossupression, source and immunogenicity of mesenchymal stem cells, and oncogenicity) that have been addressed and will be followed up by the MiSOT Consortium in future studies.

Toll-like receptors as modulators of mesenchymal stem cells.

Mesenchymal stem cells (MSCs) have differentiation and immunomodulatory properties that make them interesting tools for the treatment of degenerative disorders, allograft rejection, or inflammatory and autoimmune diseases. Biological properties of MSCs can be modulated by the inflammatory microenvironment they face at the sites of injury or inflammation. Indeed, MSCs do not constitutively exert their immunomodulating properties but have to be primed by inflammatory mediators released from immune cells and inflamed tissue. A polarization process, mediated by Toll-like receptors (TLRs), toward either an anti-inflammatory or a pro-inflammatory phenotype has been described for MSCs. TLRs have been linked to allograft rejection and the perpetuation of chronic inflammatory diseases (e.g., Crohn's disease, rheumatoid arthritis) through the recognition of conserved pathogen-derived components or endogenous ligands (danger signals) produced upon injury. Interest in understanding the effects of TLR activation on MSCs has greatly increased in the last few years since MSCs will likely encounter TLR ligands at sites of injury, and it has been proven that the activation of TLRs in MSCs can modulate their function and therapeutic effect.