Extracellular vesicles from senescent mesenchymal stromal cells are defective and cannot prevent osteoarthritis.

Age is the most important risk factor in degenerative diseases such as osteoarthritis (OA), which is associated with the accumulation of senescent cells in the joints. Here, we aimed to assess the impact of senescence on the therapeutic properties of extracellular vesicles (EVs) from human fat mesenchymal stromal cells (ASCs) in OA. We generated a model of DNA damage-induced senescence in ASCs using etoposide and characterized EVs isolated from their conditioned medium (CM). Senescent ASCs (S-ASCs) produced 3-fold more EVs (S-EVs) with a slightly bigger size and that contain 2-fold less total RNA. Coculture experiments showed that S-ASCs were as efficient as healthy ASCs (H-ASCs) in improving the phenotype of OA chondrocytes cultured in resting conditions but were defective when chondrocytes were proliferating. S-EVs were also impaired in their capacity to polarize synovial macrophages towards an anti-inflammatory phenotype. A differential protein cargo mainly related to inflammation and senescence was detected in S-EVs and H-EVs. Using the collagenase-induced OA model, we found that contrary to H-EVs, S-EVs could not protect mice from cartilage damage and joint calcifications, and were less efficient in protecting subchondral bone degradation. In addition, S-EVs induced a pro-catabolic and pro-inflammatory gene signature in the joints of mice shortly after injection, while H-EVs decreased hypertrophic, catabolic and inflammatory pathways. In conclusion, S-EVs are functionally impaired and cannot protect mice from developing OA.

What is the rationale for mesenchymal stromal cells based therapies in the management of hemophilic arthropathies?

Hemophilia A and B are rare X-linked genetic bleeding disorders due to a complete or partial deficiency in the coagulation factors VIII or IX, respectively. The main treatment for hemophilia is prophylactic and based on coagulation factor replacement therapies. These treatments have significantly reduced bleeding and improved the patients' quality of life. Nevertheless, repeated joint bleedings (hemarthroses), even subclinical hemarthroses, can lead to hemophilic arthropathy (HA). This disabling condition is characterized by chronic pain due to synovial inflammation, cartilage and bone destruction requiring ultimately joint replacement. HA resembles to rheumatoid arthritis because of synovitis but HA is considered as having similarities with osteoarthritis as illustrated by the migration of immune cells, production of inflammatory cytokines, synovial hypertrophy and cartilage damage. Various drugs have been evaluated for the management of HA with limited success. The objective of the review is to discuss new therapeutic approaches with a special focus on the studies that have investigated the potential of using mesenchymal stromal cells (MSCs) in the management of HA. A systematic review of the literature has been made. Most of the studies have focused on the interest of MSCs for the delivery of missing factors VIII or IX but in some studies, more insight on the effect of MSC injection on synovial inflammation or cartilage structure were provided and put in perspective for possible clinical applications.

Therapeutic potential in rheumatic diseases of extracellular vesicles derived from mesenchymal stromal cells.

The incidence of rheumatic diseases such as rheumatoid arthritis and osteoarthritis and injuries to articular cartilage that lead to osteochondral defects is predicted to rise as a result of population ageing and the increase in high-intensity physical activities among young and middle-aged people. Current treatments focus on the management of pain and joint functionality to improve the patient's quality of life, but curative strategies are greatly desired. In the past two decades, the therapeutic value of mesenchymal stromal cells (MSCs) has been evaluated because of their regenerative potential, which is mainly attributed to the secretion of paracrine factors. Many of these factors are enclosed in extracellular vesicles (EVs) that reproduce the main functions of parental cells. MSC-derived EVs have anti-inflammatory, anti-apoptotic as well as pro-regenerative activities. Research on EVs has gained considerable attention as they are a potential cell-free therapy with lower immunogenicity and easier management than whole cells. MSC-derived EVs can rescue the pathogenetic phenotypes of chondrocytes and exert a protective effect in animal models of rheumatic disease. To facilitate the therapeutic use of EVs, appropriate cell sources for the production of EVs with the desired biological effects in each disease should be identified. Production and isolation of EVs should be optimized, and pre-isolation and post-isolation modifications should be considered to maximize the disease-modifying potential of the EVs.

Lung Fibrosis Is Improved by Extracellular Vesicles from IFNγ-Primed Mesenchymal Stromal Cells in Murine Systemic Sclerosis.

BACKGROUND: Systemic sclerosis (SSc) is a severe autoimmune disease for which mesenchymal stromal cells (MSCs)-based therapy was reported to reduce SSc-related symptoms in pre-clinical studies. Recently, extracellular vesicles released by MSCs (MSC-EVs) were shown to mediate most of their therapeutic effect. Here, we aimed at improving their efficacy by increasing the MSC-EV dose or by IFNγ-priming of MSCs. METHODS: small size (ssEVs) and large size EVs (lsEVs) were recovered from murine MSCs that were pre-activated using 1 or 20 ng/mL of IFNγ. In the HOCl-induced model of SSc, mice were treated with EVs at day 21 and sacrificed at day 42. Lung and skin samples were collected for histological and molecular analyses. RESULTS: increasing the dose of MSC-EVs did not add benefit to the dose previously reported to be efficient in SSc. By contrast, IFNγ pre-activation improved MSC-EVs-based treatment, essentially in the lungs. Low doses of IFNγ decreased the expression of fibrotic markers, while high doses improved remodeling and anti-inflammatory markers. IFNγ pre-activation upregulated iNos, IL1ra and Il6 in MSCs and ssEVs and the PGE2 protein in lsEVs. CONCLUSION: IFNγ-pre-activation improved the therapeutic effect of MSC-EVs preferentially in the lungs of SSc mice by modulating anti-inflammatory and anti-fibrotic markers.

Extracellular Vesicles Are More Potent Than Adipose Mesenchymal Stromal Cells to Exert an Anti-Fibrotic Effect in an In Vitro Model of Systemic Sclerosis.

Systemic sclerosis (SSc) is a complex disorder resulting from dysregulated interactions between the three main pathophysiological axes: fibrosis, immune dysfunction, and vasculopathy, with no specific treatment available to date. Adipose tissue-derived mesenchymal stromal cells (ASCs) and their extracellular vesicles (EVs) have proved efficacy in pre-clinical murine models of SSc. However, their precise action mechanism is still not fully understood. Because of the lack of availability of fibroblasts isolated from SSc patients (SSc-Fb), our aim was to determine whether a TGFß1-induced model of human myofibroblasts (Tß-Fb) could reproduce the characteristics of SSc-Fb and be used to evaluate the anti-fibrotic function of ASCs and their EVs. We found out that Tß-Fb displayed the main morphological and molecular features of SSc-Fb, including the enlarged hypertrophic morphology and expression of several markers associated with the myofibroblastic phenotype. Using this model, we showed that ASCs were able to regulate the expression of most myofibroblastic markers on Tß-Fb and SSc-Fb, but only when pre-stimulated with TGFß1. Of interest, ASC-derived EVs were more effective than parental cells for improving the myofibroblastic phenotype. In conclusion, we provided evidence that Tß-Fb are a relevant model to mimic the main characteristics of SSc fibroblasts and investigate the mechanism of action of ASCs. We further reported that ASC-EVs are more effective than parental cells suggesting that the TGFß1-induced pro-fibrotic environment may alter the function of ASCs.

Extracellular vesicles from mesenchymal stromal cells: Therapeutic perspectives for targeting senescence in osteoarthritis.

Osteoarthritis (OA) is a common age-related disease that correlates with a high number of senescent cells in joint tissues. Senescence has been reported to be one of the main drivers of OA pathogenesis, in particular via the release of senescence-associated secretory phenotype (SASP) factors. SASP factors are secreted as single molecules and/or packaged within extracellular vesicles (EVs), thereby contributing to senescent phenotype dissemination. Targeting senescent cells using senolytics or senomorphics has therefore been tested and improvement of OA-associated features has been reported in murine models. Mesenchymal stromal cells (MSCs) and their derived EVs (MSC-EVs) are promising treatments for OA, exerting pleiotropic functions by producing a variety of factors. However, functions of MSCs and MSC-EVs are affected by aging. In this review, we discuss on the impact of the senescent environment on functions of aged MSC-EVs and on the anti-aging properties of MSC-EVs in the context of OA.

Mesenchymal stromal cells-derived extracellular vesicles alleviate systemic sclerosis via miR-29a-3p.

Systemic sclerosis (SSc) is a potentially lethal disease with no curative treatment. Mesenchymal stromal cells (MSCs) have proved efficacy in SSc but no data is available on MSC-derived extracellular vesicles (EVs) in this multi-organ fibrosis disease. Small size (ssEVs) and large size EVs (lsEVs) were isolated from murine MSCs or human adipose tissue-derived MSCs (ASCs). Control antagomiR (Ct) or antagomiR-29a-3p (A29a) were transfected in MSCs and ASCs before EV production. EVs were injected in the HOCl-induced SSc model at day 21 and euthanasized at day 42. We found that both ssEVs and lsEVs were effective to slow-down the course of the disease. All disease parameters improved in skin and lungs. Interestingly, down-regulating miR-29a-3p in MSCs totally abolished therapeutic efficacy. Besides, we demonstrated a similar efficacy of human ASC-EVs and importantly, EVs from A29a-transfected ASCs failed to improve skin fibrosis. We identified Dnmt3a, Pdgfrbb, Bcl2, Bcl-xl as target genes of miR-29a-3p whose regulation was associated with skin fibrosis improvement. Our study highlights the therapeutic role of miR-29a-3p in SSc and the importance of regulating methylation and apoptosis.

miR-155 Contributes to the Immunoregulatory Function of Human Mesenchymal Stem Cells.

Objectives: Mesenchymal stem/stromal cells (MSCs) are widely investigated in regenerative medicine thanks to their immunomodulatory properties. They exert their anti-inflammatory function thanks to the secretion of a number of mediators, including proteins and miRNAs, which can be released in the extracellular environment or in the cargo of extracellular vesicles (EVs). However, the role of miRNAs in the suppressive function of MSCs is controversial. The aim of the study was to identify miRNAs that contribute to the immunomodulatory function of human bone marrow-derived MSCs (BM-MSCs). Methods: Human BM-MSCs were primed by coculture with activated peripheral blood mononuclear cells (aPBMCs). High throughput miRNA transcriptomic analysis was performed using Human MicroRNA TaqMan® Array Cards. The immunosuppressive function of miRNAs was investigated in mixed lymphocyte reactions and the delayed type hypersensitivity (DTH) murine model. Results: Upon priming, 21 out of 377 tested miRNAs were significantly modulated in primed MSCs. We validated the up-regulation of miR-29a, miR-146a, miR-155 and the down-regulation of miR-149, miR-221 and miR-361 in additional samples of primed MSCs. We showed that miR-155 significantly reduced the proliferation of aPBMCs in vitro and inflammation in vivo, using the DTH model. Analysis of miRNA-mRNA interactions revealed miR-221 as a potential target gene that is down-regulated by miR-155 both in primed MSCs and in aPBMCs. Conclusion: Here, we present evidence that miR-155 participates to the immunosuppressive function of human BM-MSCs and down-regulates the expression of miR-221 as a possible inflammatory mediator.

Biobased pH-responsive and self-healing hydrogels prepared from O-carboxymethyl chitosan and a 3-dimensional dynamer as cartilage engineering scaffold.

Novel dynamic hydrogels were prepared from O-carboxymethyl chitosan (CMCS) and a water soluble dynamer Dy via crosslinking by imine bond formation using an environmentally friendly method. Dy was synthesized by reaction of Benzene-1,3,5-tricarbaldehyde with Jeffamine. The resulting soft hydrogels exhibit a porous and interconnected morphology, storage modulus up to 1400 Pa, and excellent pH-sensitive swelling properties. The swelling ratio is relatively low at acidic pH due to electrostatic attraction, and becomes exceptionally high up to 7000 % at pH 8 due to electrostatic repulsion. Moreover, hydrogels present outstanding self-healing properties as evidenced by closure of split pieces and rheological measurements. This study opens up a new horizon in the preparation of dynamic hydrogels with great potential for applications in drug delivery, wound dressing, and in particular in tissue engineering as the hydrogels present excellent cytocompatibility.

TGFBI secreted by mesenchymal stromal cells ameliorates osteoarthritis and is detected in extracellular vesicles.

Mesenchymal stem/stromal cells (MSCs) are of interest in the context of osteoarthritis (OA) therapy. We previously demonstrated that TGFß-induced gene product-h3 (TGFBI/BIGH3) is downregulated in human MSCs (hMSCs) from patients with OA, suggesting a possible link with their impaired regenerative potential. In this study, we investigated TGFBI contribution to MSC-based therapy in OA models. First, we showed that co-culture with murine MSCs (mMSCs) partly restored the expression of anabolic markers and decreased expression of catabolic markers in OA-like chondrocytes only upon priming by TGFß3. Moreover, TGFß3-primed hMSCs not only modulated the expression of anabolic and catabolic markers, but also decreased inflammatory factors. Then, we found that upon TGFBI silencing, mMSCs partly lost their inductive effect on chondrocyte anabolic markers. Injection of hMSCs in which TGFBI was silenced did not protect mice from OA development. Finally, we showed that MSC chondroprotection was attributed to the presence of TGFBI mRNA and protein in extracellular vesicles. Our findings suggest that TGFBI is a chondroprotective factor released by MSCs and an anabolic regulator of cartilage homeostasis.

Biocompatible Glycine-Assisted Catalysis of the Sol-Gel Process: Development of Cell-Embedded Hydrogels.

The sol-gel process can be used for hydrogel cross-linking, thus opening an attractive route for the design of biocompatible hydrogels under soft conditions. The sol-gel process can be catalysed at basic or acidic pH values, under neutral conditions with the addition of a nucleophile. Therefore, working around pH 7 unlocks the possibility of direct cell embedment and the preparation of bioinks. We aimed to propose a generic method for sol-gel 3D bioprinting, and first screened different nucleophilic catalysts using bis-silylated polyethylene glycol (PEG) as a model hydrogel. A synergistic effect of glycine and NaF, used in low concentrations to avoid any toxicity, was observed. Biocompatibility of the approach was demonstrated by embedding primary mouse mesenchymal stem cells. The measure of viscosity as a function of time showed the impact of reaction parameters, such as temperature, complexity of the medium, pH and cell addition, on the kinetics of the sol-gel process, and allowed prediction of the gelation time.

Fibrosis Development in HOCl-Induced Systemic Sclerosis: A Multistage Process Hampered by Mesenchymal Stem Cells.

Objectives: Skin fibrosis is the hallmark of systemic sclerosis (SSc) a rare intractable disease with unmet medical need. We previously reported the anti-fibrotic potential of mesenchymal stem cells (MSCs) in a murine model of SSc. This model, based on daily intra-dermal injections of hypochlorite (HOCl) during 6 weeks, is an inducible model of the disease. Herein, we aimed at characterizing the development of skin fibrosis in HOCl-induced SSc (HOCl-SSc), and evaluating the impact of MSC infusion during the fibrogenesis process. Methods: After HOCl-SSc induction in BALB/c mice, clinical, histological and biological parameters were measured after 3 weeks (d21) and 6 weeks (d42) of HOCl challenge, and 3 weeks after HOCl discontinuation (d63). Treated-mice received infusions of 2.5 × 105 MSCs 3 weeks before sacrifice (d0, d21, d42). Results: HOCl injections induced a two-step process of fibrosis development: first, an 'early inflammatory phase', characterized at d21 by highly proliferative infiltrates of myofibroblasts, T-lymphocytes and macrophages. Second, a phase of 'established matrix fibrosis', characterized at d42 by less inflammation, but strong collagen deposition and followed by a third phase of 'spontaneous tissue remodeling' after HOCl discontinuation. This phase was characterized by partial fibrosis receding, due to enhanced MMP1/TIMP1 balance. MSC treatment reduced skin thickness in the three phases of fibrogenesis, exerting more specialized mechanisms: immunosuppression, abrogation of myofibroblast activation, or further enhancing tissue remodeling, depending on the injection time-point. Conclusion: HOCl-SSc mimics three fibrotic phenotypes of scleroderma, all positively impacted by MSC therapy, demonstrating the great plasticity of MSC, a promising cure for SSc.

Contribution of microRNAs to the immunosuppressive function of mesenchymal stem cells.

Mesenchymal stem/stromal cells (MSCs) are progenitor cells identified in many adult tissues, in particular in bone marrow or adipose tissue and, in placental tissues. MSCs exert pleiotropic functions that render them attractive for many clinical applications, both in degenerative and inflammatory diseases. Their main mode of action is through the secretion of trophic factors that can be released in the extracellular milieu or packaged within extracellular vesicles. These factors can be proteins, lipids, mRNAs or miRNAs that possess diverse effects, notably pro-angiogenic, anti-fibrotic, anti-apoptotic or anti-inflammatory. The anti-inflammatory role of a number of miRNAs has been demonstrated with different types of immune cells but few have been associated with the immunomodulatory function of MSCs. In this review, we summarize the data on the miRNAs that have been validated as participating to the anti-inflammatory role of MSCs.

Mesenchymal stem cells-derived exosomes are more immunosuppressive than microparticles in inflammatory arthritis.

Objectives: Mesenchymal stem cells (MSCs) release extracellular vesicles (EVs) that display a therapeutic effect in inflammatory disease models. Although MSCs can prevent arthritis, the role of MSCs-derived EVs has never been reported in rheumatoid arthritis. This prompted us to compare the function of exosomes (Exos) and microparticles (MPs) isolated from MSCs and investigate their immunomodulatory function in arthritis. Methods: MSCs-derived Exos and MPs were isolated by differential ultracentrifugation. Immunosuppressive effects of MPs or Exos were investigated on T and B lymphocytes in vitro and in the Delayed-Type Hypersensitivity (DTH) and Collagen-Induced Arthritis (CIA) models. Results: Exos and MPs from MSCs inhibited T lymphocyte proliferation in a dose-dependent manner and decreased the percentage of CD4+ and CD8+ T cell subsets. Interestingly, Exos increased Treg cell populations while parental MSCs did not. Conversely, plasmablast differentiation was reduced to a similar extent by MSCs, Exos or MPs. IFN-γ priming of MSCs before vesicles isolation did not influence the immunomodulatory function of isolated Exos or MPs. In DTH, we observed a dose-dependent anti-inflammatory effect of MPs and Exos, while in the CIA model, Exos efficiently decreased clinical signs of inflammation. The beneficial effect of Exos was associated with fewer plasmablasts and more Breg-like cells in lymph nodes. Conclusions: Both MSCs-derived MPs and Exos exerted an anti-inflammatory role on T and B lymphocytes independently of MSCs priming. However, Exos were more efficient in suppressing inflammation in vivo. Our work is the first demonstration of the therapeutic potential of MSCs-derived EVs in inflammatory arthritis.

iNOS Activity Is Required for the Therapeutic Effect of Mesenchymal Stem Cells in Experimental Systemic Sclerosis.

Objectives: Fibrosis is a hallmark of systemic sclerosis (SSc), an intractable disease where innovative strategies are still being sought. Among novel anti-fibrotic approaches, mesenchymal stromal/stem cell (MSC)-based therapy appears promising. Previously, we reported anti-fibrotic effects of MSC in an experimental model of SSc, through various mechanisms (tissue remodeling, immunomodulation, anti-oxidant defense). Since immunomodulation is a pivotal mechanism for MSC therapeutic effects, we investigated the specific role of critical molecules associated with MSC immunosuppressive properties and hypothesized that MSC defective for these molecules would be less effective in reducing fibrosis in SSc. Methods: SSc was induced by 6-week daily intradermal injections of hypochlorite (HOCl) in mice. MSC were isolated from the bone marrow of wild type mice (WT) or mice knockout for IL1RA, IL6, or iNOS (IL1RA-/-, IL6-/-, or iNOS-/- MSC, respectively). Treated-mice received 2.5 × 105 MSC intravenous infusion at d21. Skin thickness, histological and biological parameters were evaluated in skin and blood at d42. Results: IL1RA-/- and IL6-/- MSC exerted similar anti-fibrotic properties as WT MSC, with a reduction of skin thickness together with less collagen deposition. Conversely, iNOS-/- MSC did not exert anti-fibrotic functions as shown by a similar skin thickness progression as non-treated HOCl-SSc mice. Compared with WT MSC, iNOS-/- MSC kept some immunosuppressive and tissue remodeling properties, but lost their capacity to reduce oxidative stress in HOCl-SSc mice. Conclusion: Our study highlights the crucial role of iNOS, whose activity is required for the anti-fibrotic properties of MSC in experimental SSc, with a special emphasis on NO-related anti-oxidant functions.

[Mesenchymal stem cells and regenerative medicine: future perspectives in osteoarthritis]. / Cellules souches mésenchymateuses et médecine régénératrice - Quel avenir pour l'arthrose ?

Mesenchymal stromal or stem cells (MSCs) are multipotent adult cells that can be isolated from a variety of adult or neonatal tissues, such as bone marrow, fat tissue, placenta or umbilical cord. A therapy based on MSCs can be justified in osteoarthritis (OA) thanks to their differentiation abilities but mostly, to their paracrine and immunosuppressive properties. Possible therapeutic strategies therefore rely on the articular injection of MSCs suspensions for trophic activity or the implantation of MSCs combined with biodegradable materials for tissue engineering applications. Depending on the mode of administration and behavior after implantation, they can decrease local inflammation, prevent chondrocyte hypertrophy and apoptosis as well as differentiate into cartilage-forming chondrocytes. In this review, we summarize pathophysiological and mechanistic data and discuss perspectives confirming the interest of MSCs as a potential therapeutic strategy in OA.

Pathogenic or Therapeutic Extracellular Vesicles in Rheumatic Diseases: Role of Mesenchymal Stem Cell-Derived Vesicles.

Extracellular vesicles (EVs) are important mediators of cell-to-cell communication pathways via the transport of proteins, mRNA, miRNA and lipids. There are three main types of EVs, exosomes, microparticles and apoptotic bodies, which are classified according to their size and biogenesis. EVs are secreted by all cell types and their function reproduces that of the parental cell. They are involved in many biological processes that regulate tissue homeostasis and physiopathology of diseases. In rheumatic diseases, namely osteoarthritis (OA) and rheumatoid arthritis (RA), EVs have been isolated from synovial fluid and shown to play pathogenic roles contributing to progression of both diseases. By contrast, EVs may have therapeutic effect via the delivery of molecules that may stop disease evolution. In particular, EVs derived from mesenchymal stem cells (MSCs) reproduce the main functions of the parental cells and therefore represent the ideal type of EVs for modulating the course of either disease. The aim of this review is to discuss the role of EVs in OA and RA focusing on their potential pathogenic effect and possible therapeutic options. Special attention is given to MSCs and MSC-derived EVs for modulating OA and RA progression with the perspective of developing innovative therapeutic strategies.

Adipose-Derived Mesenchymal Stem Cells in Autoimmune Disorders: State of the Art and Perspectives for Systemic Sclerosis.

Mesenchymal stromal/stem cells (MSC) are non-hematopoietic multipotent progenitor cells, first described in bone marrow in the middle of last century. Since then, MSC have been the objects of a myriad of publications, progressively increasing our knowledge on their potentialities and bringing high expectancies for their regenerative properties. During the same period, numerous tissues, such as adipose tissue, placenta, or umbilical cord, have been used as alternative sources of MSC in comparison with bone marrow. In particular, considering the accessibility and ease to harvest fat tissue, adipose-derived MSC have gained interest above bone marrow-derived MSC. More recently, the discovery of MSC immunomodulatory properties made MSC-based therapy progressively slip from the field of regenerative medicine to the one of autoimmunity. Indeed, in this group of disorders caused by aberrant activation of the immune system resulting in loss of self-tolerance and auto-reactivity, conventional immunosuppressant may be harmful. One advantage of MSC-based therapy would lie in their immune plasticity, resulting in space and time-limited immunosuppression. More specifically, among autoimmune disorders, systemic sclerosis appears as a peculiar multifaceted disease, in which autoimmune phenomena coexist with vascular abnormalities and multi-visceral fibrosis. Considering the pleiotropic effects of MSC, displaying immunomodulatory, angiogenic and antifibrotic capabilities, MSC-based therapy could counteract the three main pathogenic axes of systemic sclerosis and might thus represent a complete breakthrough in this intractable disease with unmet medical need. In this article, while reviewing most recent literature on MSC biology, we itemize their current applications in the field of autoimmunity and shed light onto the potential use of adipose-derived MSC as an innovative strategy to cure systemic sclerosis.

Comparison between Stromal Vascular Fraction and Adipose Mesenchymal Stem Cells in Remodeling Hypertrophic Scars.

Hypertrophic scars (HTS) are characterized by excessive amount of collagen deposition and principally occur following burn injuries or surgeries. In absence of effective treatments, the use of mesenchymal stem/stromal cells, which have been shown to attenuate fibrosis in various applications, seems of interest. The objectives of the present study were therefore to evaluate the effect of human adipose tissue-derived mesenchymal stem cells (hASC) on a pre-existing HTS in a humanized skin graft model in Nude mice and to compare the efficacy of hASCs versus stromal vascular fraction (SVF). We found that injection of SVF or hASCs resulted in an attenuation of HTS as noticed after clinical evaluation of skin thickness, which was associated with lower total collagen contents in the skins of treated mice and a reduced dermis thickness after histological analysis. Although both SVF and hASCs were able to significantly reduce the clinical and histological parameters of HTS, hASCs appeared to be more efficient than SVF. The therapeutic effect of hASCs was attributed to higher expression of TGFß3 and HGF, which are important anti-fibrotic mediators, and to higher levels of MMP-2 and MMP-2/TIMP-2 ratio, which reflect the remodelling activity responsible for fibrosis resorption. These results demonstrated the therapeutic potential of hASCs for clinical applications of hypertrophic scarring.

Human adipose mesenchymal stem cells as potent anti-fibrosis therapy for systemic sclerosis.

OBJECTIVES: Displaying immunosuppressive and trophic properties, mesenchymal stem/stromal cells (MSC) are being evaluated as promising therapeutic options in a variety of autoimmune and degenerative diseases. Although benefits may be expected in systemic sclerosis (SSc), a rare autoimmune disease with fibrosis-related mortality, MSC have yet to be evaluated in this specific condition. While autologous approaches could be inappropriate because of functional alterations in MSC from patients, the objective of the present study was to evaluate allogeneic and xenogeneic MSC in the HOCl-induced model of diffuse SSc. We also questioned the source of human MSC and compared bone marrow- (hBM-MSC) and adipose-derived MSC (hASC). METHODS: HOCl-challenged BALB/c mice received intravenous injection of BM-MSC from syngeneic BALB/c or allogeneic C57BL/6 mice, and xenogeneic hBM-MSC or hASC (3 donors each). Skin thickness was measured during the experiment. At euthanasia, histology, immunostaining, collagen determination and RT-qPCR were performed in skin and lungs. RESULTS: Xenogeneic hBM-MSC were as effective as allogeneic or syngeneic BM-MSC in decreasing skin thickness, expression of Col1, Col3, α-Sma transcripts, and collagen content in skin and lungs. This anti-fibrotic effect was not associated with MSC migration to injured skin or with long-term MSC survival. Interestingly, compared with hBM-MSC, hASC were significantly more efficient in reducing skin fibrosis, which was related to a stronger reduction of TNFα, IL1ß, and enhanced ratio of Mmp1/Timp1 in skin and lung tissues. CONCLUSIONS: Using primary cells isolated from 3 murine and 6 human individuals, this preclinical study demonstrated similar therapeutic effects using allogeneic or xenogeneic BM-MSC while ASC exerted potent anti-inflammatory and remodeling properties. This sets the proof-of-concept prompting to evaluate the therapeutic efficacy of allogeneic ASC in SSc patients.