Activated Mesenchymal Stromal Cells Process and Present Antigens Regulating Adaptive Immunity

Advancements in diabetic foot ulcer research: Focus on mesenchymal stem cells and their exosomes

Diabetes represents a widely acknowledged global public health concern. Diabetic foot ulcer (DFU) stands as one of the most severe complications of diabetes, its occurrence imposing a substantial economic burden on patients, profoundly impacting their quality of life. Despite the deepening comprehension regarding the pathophysiology and cellular as well as molecular responses of DFU, the current therapeutic arsenal falls short of efficacy, failing to offer a comprehensive remedy for deep-seated chronic wounds and microvascular occlusions. Conventional treatments merely afford symptomatic alleviation or retard the disease's advancement, devoid of the capacity to effectuate further restitution of compromised vasculature and nerves. An escalating body of research underscores the prominence of mesenchymal stem cells (MSCs) owing to their paracrine attributes and anti-inflammatory prowess, rendering them a focal point in the realm of chronic wound healing. Presently, MSCs have been validated as a highly promising cellular therapeutic approach for DFU, capable of effectuating cellular repair, epithelialization, granulation tissue formation, and neovascularization by means of targeted differentiation, angiogenesis promotion, immunomodulation, and paracrine activities, thereby fostering wound healing. The secretome of MSCs comprises cytokines, growth factors, chemokines, alongside exosomes harboring mRNA, proteins, and microRNAs, possessing immunomodulatory and regenerative properties. The present study provides a systematic exposition on the etiology of DFU and elucidates the intricate molecular mechanisms and diverse functionalities of MSCs in the context of DFU treatment, thereby furnishing pioneering perspectives aimed at harnessing the therapeutic potential of MSCs for DFU management and advancing wound healing processes.

Inter- and Intra-donor variability in bone marrow-derived mesenchymal stromal cells: implications for clinical applications

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are attractive as a therapeutic modality in multiple disease conditions characterized by inflammation and vascular compromise. Logistically they are advantageous because they can be isolated from adult tissue sources, such as bone marrow (BM). The phase 2a START clinical trial determined BM-MSCs to be safe in patients with moderate-to-severe acute respiratory distress syndrome (ARDS). Herein, we examine a subset of the clinical doses of MSCs generated for the phase 2a START trial from three unique donors (1-3), where one of the donors' donated BM on two separate occasions (donor 3 and 3W).

METHODS

The main objective of this study was to correlate properties of the cells from the four lots with plasma biomarkers from treated patients and relevant to ARDS outcomes. To do this we evaluated MSC donor lots for (i) post-thaw viability, (ii) growth kinetics, (iii) metabolism, (iv) surface marker expression, (v) protein expression, (vi) immunomodulatory ability and (vii) their functional effects on regulating endothelial cell permeability.

RESULTS

MSC-specific marker expression and protection of thrombin-challenged endothelial barrier permeability was similar among all four donor lots. Inter and intra-donor variability was observed in all the other in vitro assays. Furthermore, patient plasma ANG-2 and protein C levels at 6 hours post-transfusion were correlated to cell viability in an inter- and intra-donor dependent manner.

CONCLUSIONS

These findings highlight the potential of donor dependent (inter-) and collection dependent (intra-) effects in patient biomarker expression.

Activated STING-containing R-EVs from iPSC-derived MSCs promote antitumor immunity

We recently revealed that activated STING is secreted into RAB22A-induced extracellular vesicles (R-EVs) and promotes antitumor immunity in cancer cells. Whether mesenchymal stem cell (MSC)-derived R-EVs containing activated STING can be used as a novel antitumor immunotherapy remains unclear, as MSC-derived EVs are promising cell-free therapeutics due to their superior biocompatibility and safety, as well as low immunogenicity. Here, we report that induced pluripotent stem cell (iPSC)-derived MSCs can generate R-EVs with a size and mechanism of formation that are similar to those of R-EVs produced from cancer cells. Furthermore, these MSC-derived R-EVs containing activated STING induced IFNβ expression in recipient THP-1 monocytes and antitumor immunity in mice. Our findings reveal that the use of MSC-derived R-EVs containing activated STING is a promising cell-free strategy for antitumor immunity.

Interplay Between Skeletal and Hematopoietic Cells in the Bone Marrow Microenvironment in Homeostasis and Aging

PURPOSE OF THE REVIEW

In this review, we discuss the most recent scientific advances on the reciprocal regulatory interactions between the skeletal and hematopoietic stem cell niche, focusing on immunomodulation and its interplay with the cell's mitochondrial function, and how this impacts osteoimmune health during aging and disease.

RECENT FINDINGS

Osteoimmunology investigates interactions between cells that make up the skeletal stem cell niche and immune system. Much work has investigated the complexity of the bone marrow microenvironment with respect to the skeletal and hematopoietic stem cells that regulate skeletal formation and immune health respectively. It has now become clear that these cellular components cooperate to maintain homeostasis and that dysfunction in their interaction can lead to aging and disease. Having a deeper, mechanistic appreciation for osteoimmune regulation will lead to better research perspective and therapeutics with the potential to improve the aging process, skeletal and hematologic regeneration, and disease targeting.

Impact of platelet lysate on immunoregulatory characteristics of equine mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSC) play an increasing role in the treatment of immune-mediated diseases and inflammatory processes. They regulate immune cells via cell-cell contacts and by secreting various anti-inflammatory molecules but are in turn influenced by many factors such as cytokines. For MSC culture, platelet lysate (PL), which contains a variety of cytokines, is a promising alternative to fetal bovine serum (FBS). We aimed to analyze if PL with its cytokines improves MSC immunoregulatory characteristics, with the perspective that PL could be useful for priming the MSC prior to therapeutic application. MSC, activated peripheral blood mononuclear cells (PBMC) and indirect co-cultures of both were cultivated in media supplemented with either PL, FBS, FBS+INF-γ or FBS+IL-10. After incubation, cytokine concentrations were measured in supernatants and control media. MSC were analyzed regarding their expression of immunoregulatory genes and PBMC regarding their proliferation and percentage of FoxP3+ cells. Cytokines, particularly IFN-γ and IL-10, remained at high levels in PL control medium without cells but decreased in cytokine-supplemented control FBS media without cells during incubation. PBMC released IFN-γ and IL-10 in various culture conditions. MSC alone only released IFN-γ and overall, cytokine levels in media were lowest when MSC were cultured alone. Stimulation of MSC either by PBMC or by PL resulted in an altered expression of immunoregulatory genes. In co-culture with PBMC, the MSC gene expression of COX2, TNFAIP6, IDO1, CXCR4 and MHC2 was upregulated and VCAM1 was downregulated. In the presence of PL, COX2, TNFAIP6, VCAM1, CXCR4 and HIF1A were upregulated. Functionally, while no consistent changes were found regarding the percentage of FoxP3+ cells, MSC decreased PBMC proliferation in all media, with the strongest effect in FBS media supplemented with IL-10 or IFN-γ. This study provides further evidence that PL supports MSC functionality, including their immunoregulatory mechanisms. The results justify to investigate functional effects of MSC cultured in PL-supplemented medium on different types of immune cells in more detail.

Three-Dimensionally Cultured Jaw Periosteal Cells Attenuate Macrophage Activation of CD4+ T Cells and Inhibit Osteoclastogenesis

The implementation of a successful therapeutic approach that includes tissue-engineered grafts requires detailed analyses of graft-immune cell interactions in order to predict possible immune reactions after implantation. The phenotypic plasticity of macrophages plays a central role in immune cell chemotaxis, inflammatory regulation and bone regeneration. The present study addresses effects emanating from JPC-seeded β-TCP constructs (3DJPCs) co-cultivated with THP-1 derived M1/M2 macrophages within a horizontal co-culture system. After five days of co-culture, macrophage phenotype and chemokine secretion were analyzed by flow cytometry, quantitative PCR and proteome arrays. The results showed that pro-inflammatory factors in M1 macrophages were inhibited by 3DJPCs, while anti-inflammatory factors were activated, possibly affected by the multiple chemokines secreted by 3D-cultured JPCs. In addition, osteoclast markers of polarized macrophages were inhibited by osteogenically induced 3DJPCs. Functional assays revealed a significantly lower percentage of proliferating CD4+ T cells in the groups treated with secretomes from M1/M2 macrophages previously co-cultured with 3DJPCs compared to controls without secretomes. Quantifications of pit area resorption assays showed evidence that supernatants from 3DJPCs co-cultured with M1/M2 macrophages were able to completely suppress osteoclast maturation, compared to the control group without secretomes. These findings demonstrate the ability of 3D cultured JPCs to modulate macrophage plasticity.

The immunogenic profile and immunomodulatory function of mesenchymal stromal / stem cells in the presence of Ptychotis verticillata

Mesenchymal stromal/stem cells (MSCs) are considered to be a promising immunotherapeutic tool due to their easy accessibility, culture expansion possibilities, safety profile, and immunomodulatory properties. Although several studies have demonstrated the therapeutic effects of MSCs, their efficacy needs to be improved while also preserving their safety. It has been suggested that cell homeostasis may be particularly sensitive to plant extracts. The impact of natural compounds on immunity is thus a fascinating and growing field. Ptychotis verticillata and its bioactive molecules, carvacrol and thymol, are potential candidates for improving MSC therapeutic effects. They can be used as immunotherapeutic agents to regulate MSC functions and behavior during immunomodulation. Depending on their concentrations and incubation time, these compounds strengthened the immunomodulatory functions of MSCs while maintaining their immune-evasive profile. Incubating MSCs with carvacrol and thymol does not alter their hypoimmunogenicity, as no induction of the allogeneic immune response was observed. MSCs also showed enhanced abilities to reduce the proliferation of activated T cells. Thus, MSCs are immunologically responsive to bioactive molecules derived from PV. The bioactivity may depend on the whole phyto-complex of the oil. These findings may contribute to the development of safe and efficient immunotherapeutic MSCs by using medicinal plant-derived active molecules.

Identification and characterization of stromal-like cells with CD207+/low CD1a+/low phenotype derived from histiocytic lesions - a perspective in vitro model for drug testing

BACKGROUND

Histiocytoses are rare disorders manifested by increased proliferation of pathogenic myeloid cells sharing histological features with macrophages or dendritic cells and accumulating in various organs, i.a., bone and skin. Pre-clinical in vitro models that could be used to determine molecular pathways of the disease are limited, hence research on histiocytoses is challenging. The current study compares cytophysiological features of progenitor, stromal-like cells derived from histiocytic lesions (sl-pHCs) of three pediatric patients with different histiocytoses types and outcomes. The characterized cells may find potential applications in drug testing.

METHODS

Molecular phenotype of the cells, i.e. expression of CD1a and CD207 (langerin), was determined using flow cytometry. Cytogenetic analysis included GTG-banded metaphases and microarray (aCGH) evaluation. Furthermore, the morphology and ultrastructure of cells were evaluated using a confocal and scanning electron microscope. The microphotographs from the confocal imaging were used to reconstruct the mitochondrial network and its morphology. Basic cytophysiological parameters, such as viability, mitochondrial activity, and proliferation, were analyzed using multiple cellular assays, including Annexin V/7-AAD staining, mitopotential analysis, BrdU test, clonogenicity analysis, and distribution of cells within the cell cycle. Biomarkers potentially associated with histiocytoses progression were determined using RT-qPCR at mRNA, miRNA and lncRNA levels. Intracellular accumulation of histiocytosis-specific proteins was detected with Western blot. Cytotoxicyty and IC50 of vemurafenib and trametinib were determined with MTS assay.

RESULTS

Obtained cellular models, i.e. RAB-1, HAN-1, and CHR-1, are heterogenic in terms of molecular phenotype and morphology. The cells express CD1a/CD207 markers characteristic for dendritic cells, but also show intracellular accumulation of markers characteristic for cells of mesenchymal origin, i.e. vimentin (VIM) and osteopontin (OPN). In subsequent cultures, cells remain viable and metabolically active, and the mitochondrial network is well developed, with some distinctive morphotypes noted in each cell line. Cell-specific transcriptome profile was noted, providing information on potential new biomarkers (non-coding RNAs) with diagnostic and prognostic features. The cells showed different sensitivity to vemurafenib and trametinib.

CONCLUSION

Obtained and characterized cellular models of stromal-like cells derived from histiocytic lesions can be used for studies on histiocytosis biology and drug testing.

Paracrine Responses of Cardiosphere-Derived Cells to Cytokines and TLR Ligands: A Comparative Analysis

Cardiosphere-derived cells (CDCs) are currently being evaluated in clinical trials as a potential therapeutic tool for regenerative medicine. The effectiveness of transplanted CDCs is largely attributed to their ability to release beneficial soluble factors to enhance therapeutic effects. An emerging area of research is the pretreatment of stem cells, including CDCs, with various cytokines to improve their therapeutic properties. This strategy aims to enhance their survival, proliferation, differentiation, and paracrine activities after transplantation. In our study, we investigated the differential effects of various cytokines and TLR ligands on the secretory phenotype of human CDCs. Using a magnetic bead-based immunoassay, we analyzed the CDCs-conditioned media for 41 cytokines and growth factors and detected the presence of 21 cytokines. We found that CDC incubation with lipopolysaccharide, a TLR4 ligand, and the cytokine combination of TNF/IFN significantly increased the secretion of most of the cytokines detected. Specifically, we observed an increased secretion and gene expression of IP10, MCP3, IL8, and VEGFA. In contrast, the TLR3 ligand polyinosinic-polycytidylic acid and TGF-beta had minimal effects on CDC cytokine secretion. Additionally, TNF/IFN, but not LPS, enhanced ICAM1 expression. Our findings offer new insights into the role of cytokines in potentially modulating the biology and regenerative potential of CDCs.

Mesenchymal stem cells under epigenetic control - the role of epigenetic machinery in fate decision and functional properties

Mesenchymal stem cells (mesenchymal stromal cells, MSC) are multipotent stem cells that can differentiate into cells of at least three mesodermal lineages, namely adipocytes, osteoblasts, and chondrocytes, and have potent immunomodulatory properties. Epigenetic modifications are critical regulators of gene expression and cellular differentiation of mesenchymal stem cells (MSCs). Epigenetic machinery controls MSC differentiation through direct modifications to DNA and histones. Understanding the role of epigenetic machinery in MSC is crucial for the development of effective cell-based therapies for degenerative and inflammatory diseases. In this review, we summarize the current understanding of the role of epigenetic control of MSC differentiation and immunomodulatory properties.

The Application of Mesenchymal Stem Cells in Future Vaccine Synthesis

Vaccines have significant potential in treating and/or preventing diseases, yet there remain challenges in developing effective vaccines against some diseases, such as AIDS and certain tumors. Mesenchymal stem cells (MSCs), a subset of cells with low immunogenicity, high proliferation potential, and an abundant source of extracellular vesicles (EVs), represent one of the novel and promising vaccine platforms. This review describes the unique features and potential mechanisms of MSCs as a novel vaccine platform. We also cover aspects such as the safety and stability of MSCs that warrant future in-depth studies.

Extracellular vesicles derived from umbilical cord mesenchymal stromal cells show enhanced anti-inflammatory properties via upregulation of miRNAs after pro-inflammatory priming

Autoimmune conditions, such as rheumatoid arthritis, are characterised by a loss of immune tolerance, whereby the immune cells attack self-antigens causing pain and inflammation. These conditions can be brought into remission using pharmaceutical treatments, but often have adverse side effects and some patients do not respond favourably to them. Human umbilical cord mesenchymal stromal cells (UCMSCs) present a promising alternative therapeutic due to their innate anti-inflammatory properties which can be strengthened using pro-inflammatory conditions. Their therapeutic mechanism of action has been attributed to paracrine signalling, by which nanosized acellular particles called 'extracellular vesicles' (EVs) are one of the essential components. Therefore, this research analysed the anti-inflammatory properties of UCMSC-EVs 'primed' with pro-inflammatory cytokines and at baseline with no inflammatory cytokines (control). Both control and primed EVs were co-cultured with un-pooled peripheral blood mononuclear cells (PBMCs; n = 6) from healthy donors. Neither control nor primed EVs exerted a pro-inflammatory effect on PBMCs. Instead, the primed EVs showed the immunosuppressive potential by increasing the expression of the anti-inflammatory protein FoxP3 in PBMCs. This may be attributed to the upregulated miRNAs identified in primed EVs in comparison to control EVs (miR-139-5p, miR-140-5p, miR-214-5p). These findings aid in understanding how UCMSC-EVs mediate immunosuppression and support their potential use in treating autoimmune conditions.

Different priming strategies improve distinct therapeutic capabilities of mesenchymal stromal/stem cells: Potential implications for their clinical use

Mesenchymal stromal/stem cells (MSCs) have shown significant therapeutic potential, and have therefore been extensively investigated in preclinical studies of regenerative medicine. However, while MSCs have been shown to be safe as a cellular treatment, they have usually been therapeutically ineffective in human diseases. In fact, in many clinical trials it has been shown that MSCs have moderate or poor efficacy. This inefficacy appears to be ascribable primarily to the heterogeneity of MSCs. Recently, specific priming strategies have been used to improve the therapeutic properties of MSCs. In this review, we explore the literature on the principal priming approaches used to enhance the preclinical inefficacy of MSCs. We found that different priming strategies have been used to direct the therapeutic effects of MSCs toward specific pathological processes. Particularly, while hypoxic priming can be used primarily for the treatment of acute diseases, inflammatory cytokines can be used mainly to prime MSCs in order to treat chronic immune-related disorders. The shift in approach from regeneration to inflammation implies, in MSCs, a shift in the production of functional factors that stimulate regenerative or anti-inflammatory pathways. The opportunity to fine-tune the therapeutic properties of MSCs through different priming strategies could conceivably pave the way for optimizing their therapeutic potential.

Testosterone Propionate Promotes Proliferation and Viability of Bone Marrow Mesenchymal Stem Cells while Preserving Their Characteristics and Inducing Their Anti-Cancer Efficacy

Background

Various studies have reported the effects of testosterone on different cell types, yet bone marrow-derived mesenchymal stem cells’ cellular responses to testosterone remain unknown.

Aims

To investigate the effects of testosterone propionate, an oil-soluble short-acting form of testosterone, on human bone marrow-derived mesenchymal stem cells’ proliferation and viability after 24 hours of incubation. We also investigated the impact of testosterone propionate on bone marrow-derived mesenchymal stem cell’s polarization and cytotoxicity on K562 leukemia cell line.

Study Design

In vitro study.

Methods

We expanded commercially available bone marrow derived mesenchymal stem cells in vitro and treated them with testosterone propionate at concentrations ranging from 10^-6-10^-10 M for 24 hours. Ideal concentration was determined by evaluating cellular viability and proliferation with Annexin V/Propidium Iodide assay and carboxyfluorescein succinimidyl ester staining. The characteristic features of bone marrow-derived mesenchymal stem cells were evaluated by immunophenotyping and investigating their differentiation capacities. Bone marrow-derived mesenchymal stem cells’ cytotoxic properties upon testosterone propionate treatment were determined by co-culturing the cells with K562 cells and with confocal imaging investigating polarization.

Results

Testosterone propionate promoted proliferation and maintained the viability of bone marrow-derived mesenchymal stem at 10^-8 M concentration. Further evaluations were conducted with the determined dose. The results showed that, apart from promoting mesenchymal stem cells’ polarization and increasing their cytotoxicity on K562 cells, testosterone propionate did not alter differentiation capacities of bone marrow-derived mesenchymal stem cells and certain cell surface markers, but led to a significant increase in HLA-DR expression.

Conclusion

The findings reveal that testosterone propionate promotes the proliferation and survival of bone marrow-derived mesenchymal stem cells in a dose-dependent manner without hampering their differentiation capacities, induces their polarization to the pro-inflammatory phenotype, and increases their cytotoxicity on the K562 cell line.

The immunomodulation-immunogenicity balance of equine Mesenchymal Stem Cells (MSCs) is differentially affected by the immune cell response depending on inflammatory licensing and major histocompatibility complex (MHC) compatibility

The immunomodulatory properties of equine mesenchymal stem cells (MSCs) are important for their therapeutic potential and for their facilitating role in their escape from immune recognition, which may also be influenced by donor-recipient major histocompatibility complex (MHC) matching/mismatching and MHC expression level. Factors such as inflammation can modify the balance between regulatory and immunogenic profiles of equine MSCs, but little is known about how the exposure to the immune system can affect these properties in equine MSCs. In this study, we analyzed the gene expression and secretion of molecules related to the immunomodulation and immunogenicity of equine MSCs, either non-manipulated (MSC-naive) or stimulated by pro-inflammatory cytokines (MSC-primed), before and after their exposure to autologous or allogeneic MHC-matched/-mismatched lymphocytes, either activated or resting. Cytokine priming induced the immunomodulatory profile of MSCs at the baseline (MSCs cultured alone), and the exposure to activated lymphocytes further increased the expression of interleukin 6 (IL6), cyclooxygenase 2, and inducible nitric oxide synthase, and IL6 secretion. Activated lymphocytes were also able to upregulate the regulatory profile of MSC-naive to levels comparable to cytokine priming. On the contrary, resting lymphocytes did not upregulate the immunomodulatory profile of equine MSCs, but interestingly, MSC-primed exposed to MHC-mismatched lymphocytes showed the highest expression and secretion of these mediators, which may be potentially linked to the activation of lymphocytes upon recognition of foreign MHC molecules. Cytokine priming alone did not upregulate the immunogenic genes, but MSC-primed exposed to activated or resting lymphocytes increased their MHC-I and MHC-II expression, regardless of the MHC-compatibility. The upregulation of immunogenic markers including CD40 in the MHC-mismatched co-culture might have activated lymphocytes, which, at the same time, could have promoted the immune regulatory profile aforementioned. In conclusion, activated lymphocytes are able to induce the equine MSC regulatory profile, and their effects seem to be additive to the priming action. Importantly, our results suggest that the lymphocyte response against MHC-mismatched MSC-primed would promote further activation of their immunomodulatory ability, which eventually might help them evade this reaction. Further studies are needed to clarify how these findings might have clinical implications in vivo, which will help developing safer and more effective therapies.

Effect of Crohn's disease mesenteric mesenchymal stem cells and their extracellular vesicles on T-cell immunosuppressive capacity

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal intestinal tract and has characteristic hypertrophic adipose changes observed in the mesentery. To better understand the role of the mesentery in the pathophysiology of Crohn's disease (CD), we evaluated the immunomodulatory potential of mesenchymal stem cells (MSCs) and their secreted extracellular vesicles (EVs) derived from Crohn's patients. MSCs and EVs were isolated from the mesentery and subcutaneous tissues of CD patients and healthy individuals subcutaneous tissues, and were analysed for differentiation, cytokine expression, self‐renewal and proliferation. The varying capacity of these tissue‐derived MSCs and EVs to attenuate T‐cell activation was measured in in vitro and an in vivo murine model. RNA sequencing of inflamed Crohn's disease mesentery tissue revealed an enrichment of T‐cell activation compared to non‐inflamed subcutaneous tissue. MSCs and MSC‐derived EVs isolated from Crohn's mesentery lose their ability to attenuate DSS‐induced colitis compared to subcutaneous tissue‐derived cell or EV therapy. We found that treatment with subcutaneous isolated MSCs and their EV product compared to Crohn's mesentery MSCs or EVs, the inhibition of T‐cell proliferation and IFN‐γ, IL‐17a production increased, suggesting a non‐inflamed microenvironment allows for T‐cell inhibition by MSCs/EVs. Our results demonstrate that Crohn's patient‐derived diseased mesentery tissue MSCs lose their immunosuppressive capacity in the treatment of colitis by distinct regulation of pathogenic T‐cell responses and/or T‐cell infiltration into the colon.

Engineering of hybrid spheroids of mesenchymal stem cells and drug depots for immunomodulating effect in islet xenotransplantation

Immunomodulation is an essential consideration for cell replacement procedures. Unfortunately, lifelong exposure to nonspecific systemic immunosuppression results in immunodeficiency and has toxic effects on nonimmune cells. Here, we engineered hybrid spheroids of mesenchymal stem cells (MSCs) with rapamycin-releasing poly(lactic-co-glycolic acid) microparticles (RAP-MPs) to prevent immune rejection of islet xenografts in diabetic C57BL/6 mice. Hybrid spheroids were rapidly formed by incubating cell-particle mixture in methylcellulose solution while maintaining high cell viability. RAP-MPs were uniformly distributed in hybrid spheroids and sustainably released RAP for ~3 weeks. Locoregional transplantation of hybrid spheroids containing low doses of RAP-MPs (200- to 4000-ng RAP per recipient) significantly prolonged islet survival times and promoted the generation of regional regulatory T cells. Enhanced programmed death-ligand 1 expression by MSCs was found to be responsible for the immunomodulatory performance of hybrid spheroids. Our results suggest that these hybrid spheroids offer a promising platform for the efficient use of MSCs in the transplantation field.

Cytokine Activation Reveals Tissue-Imprinted Gene Profiles of Mesenchymal Stromal Cells

Development of standardized metrics to support manufacturing and regulatory approval of mesenchymal stromal cell (MSC) products is confounded by heterogeneity of MSC populations. Many reports describe fundamental differences between MSCs from various tissues and compare unstimulated and activated counterparts. However, molecular information comparing biological profiles of activated MSCs across different origins and donors is limited. To better understand common and source-specific mechanisms of action, we compared the responses of 3 donor populations each of human umbilical cord (UC) and bone marrow (BM) MSCs to TNF-α, IL-1β or IFN-γ. Transcriptome profiles were analysed by microarray and select secretome profiles were assessed by multiplex immunoassay. Unstimulated (resting) UC and BM-MSCs differentially expressed (DE) 174 genes. Signatures of TNF-α-stimulated BM and UC-MSCs included 45 and 14 new DE genes, respectively, while all but 7 of the initial 174 DE genes were expressed at comparable levels after licensing. After IL-1β activation, only 5 of the 174 DE genes remained significantly different, while 6 new DE genes were identified. IFN-γ elicited a robust transcriptome response from both cell types, yet nearly all differences (171/174) between resting populations were attenuated. Nine DE genes predominantly corresponding to immunogenic cell surface proteins emerged as a BM-MSC signature of IFN-γ activation. Changes in protein synthesis of select analytes correlated modestly with transcript levels. The dynamic responses of licensed MSCs documented herein, which attenuated heterogeneity between unstimulated populations, provide new insight into common and source-imprinted responses to cytokine activation and can inform strategic development of meaningful, standardized assays.

Osteogenic differentiation of adipose-derived stem cells on dihydroartemisinin electrospun nanofibers

Background

Adipose tissue-derived stem cells (ASCs) are promising candidate in stem cell therapies, and maintaining their stemness potential is vital to achieve effective treatment. Natural-based scaffolds have been recently attracted increasing attention in nanomedicine and drug delivery. In this study, Dihydroartemisinin (DHART)-loaded polycaprolactone collagen nanofibers (PCL/Col NFs) were constructed as effective biocompatible scaffolds through adjusting the proportions of hydrophobic/ hydrophilic polymers for enhanced osteoblastic differentiation of human adipose-derived stem cells (hADSCs).

Results

The designed NFs were characterized through FTIR, XRD, TGA, FE-SEM, and tensile testing. DHART-loaded PCL/Col electrospun NFs provide an ideal solution, with the potential of sustained drug release as well as inhibition of drug re-crystallization. Interestingly, inhibiting DHART re-crystallization can improve its bioavailability and provide a more effective therapeutic efficacy. Besides, the data set found through FE-SEM, MTT, PicoGreen, qPCR, and alkaline phosphatase (ALP) assays revealed the improved adhesion and proliferation rate of hADSCs cultured on PCL/Col/DHART (5%) NFs after 14 and 21 days of incubation.

Conclusions

These findings confirmed the potential of the designed NF scaffolds for sustained/controlled release of DHART therapeutic molecules toward bone tissue regeneration and engineering.

Graphical Abstract

Topical applications of allogeneic adipose-derived mesenchymal stem cells ameliorate the canine keratoconjunctivitis sicca

Background

Canine keratoconjunctivitis sicca (KCS) is predominantly an immune-mediated disease. Current therapy of canine KCS is mainly by immunosuppressant, but the effectiveness was limited in some patients. In the past few years, some studies showed the results of the use of mesenchymal stem cells in treating canine KCS via periocular injections. However, the periocular injection procedure requires sedation or general anesthesia, and may lead to iatrogenic or incidental injury during the injection process. The aim of this study was to investigate the efficacy of topical allogenic canine adipose-derived mesenchymal stem cells (cAD-MSCs) in clinical patients of canine KCS.

Results

The cAD-MSCs used in this study were characterized for their capability of tri-lineage differentiation and immunomodulatory properties. In addition, preparation methods for eye drops of cAD-MSCs was developed and its optimal preservation was tested. The canine KCS patients were recruited for clinical trial and divided into two groups based on their history of previous treatment. All patients received topical cAD-MSCs treatment once per week for 6 consecutive weeks and complete ophthalmic examinations were performed 1 week before treatment (week 0) and at 3rd, 6th, 9th weeks, respectively. The results showed that the quantity and quality of tears have improved significantly following topical cAD-MSCs treatment based on Schirmers tear test-1 and tear break-up time. More than half of all patients were found improved in the tear quantity. In particular, 56.5% of the patients that were unresponsive to prior immunosuppressant therapy had an effective increase in tear volume. The severity of clinical signs was also ameliorated according to the numeric rating scale score from both patient owners and the clinician.

Conclusion

To sum up, topical cAD-MSCs may be beneficial especially in KCS patients with poor owner compliance for frequent daily use of eye drops or those who are unresponsive to immunosuppressant therapy.

CD317-Positive Immune Stromal Cells in Human "Mesenchymal Stem Cell" Populations

Heterogeneity of bone marrow mesenchymal stromal cells (MSCs, frequently referred to as "mesenchymal stem cells") clouds biological understanding and hampers their clinical development. In MSC cultures most commonly used in research and therapy, we have identified an MSC subtype characterized by CD317 expression (CD317^pos (29.77 ± 3.00% of the total MSC population), comprising CD317^dim (28.10 ± 4.60%) and CD317^bright (1.67 ± 0.58%) MSCs) and a constitutive interferon signature linked to human disease. We demonstrate that CD317^pos MSCs induced cutaneous tissue damage when applied a skin explant model of inflammation, whereas CD317^neg MSCs had no effect. Only CD317^neg MSCs were able to suppress proliferative cycles of activated human T cells in vitro, whilst CD317^pos MSCs increased polarization towards pro-inflammatory Th1 cells and CD317^neg cell lines did not. Using an in vivo peritonitis model, we found that CD317^neg and CD317^pos MSCs suppressed leukocyte recruitment but only CD317^neg MSCs suppressed macrophage numbers. Using MSC-loaded scaffolds implanted subcutaneously in immunocompromised mice we were able to observe tissue generation and blood vessel formation with CD317^neg MSC lines, but not CD317^pos MSC lines. Our evidence is consistent with the identification of an immune stromal cell, which is likely to contribute to specific physiological and pathological functions and influence clinical outcome of therapeutic MSCs.

HLA-G and CD152 Expression Levels Encourage the Use of Umbilical Cord Tissue-Derived Mesenchymal Stromal Cells as an Alternative for Immunosuppressive Therapy

Mesenchymal stromal cells (MSCs) have been used in immunosuppressive therapy due to their therapeutic effects, with the HLA-G molecule seeming to play a fundamental role. This work evaluated alternative MSC sources to bone marrow (BM), namely, umbilical cord tissue (UC), adipose tissue (AD) and dental pulp tissue (DP), and the influence of interferon-γ (IFN-γ) and hypoxia on the cultivation of these cells for use in immunosuppression therapies. Expression of costimulatory markers CD40, CD80 and CD86 and immunosuppressive molecules CD152 and HLA-G was analyzed. Lymphocyte inhibition assays were also performed. Sequencing of the HLA-G gene from exons 1 to 5 was performed using next-generation sequencing to determine the presence of alleles. UC-derived MSCs (UCMSCs) expressed higher CD152 and HLA-G1 under standard cultivation. UCMSCs and DP-derived MSCs (DPSCs) secreted similar levels of HLA-G5. All MSC sources inhibited the proliferation of peripheral blood mononuclear cells (PBMCs); growth under regular versus hypoxic conditions resulted in similar levels of inhibition. When IFN-γ was added, PBMC growth was inhibited to a lesser extent by UCMSCs. The HLA-G*01:04:01:01 allele appears to generate a more efficient MSC response in inhibiting lymphocyte proliferation. However, the strength of this conclusion was limited by the small sample size. UCMSCs are an excellent alternative to BM in immunosuppressive therapy: they express high concentrations of inhibitory molecules and can be cultivated without stimuli, which minimizes cost.

UM171A-induced ROS promote antigen cross-presentation of immunogenic peptides by bone marrow-derived mesenchymal stromal cells

Background

Mesenchymal stromal cells (MSCs) have been extensively used in the clinic due to their exquisite tissue repair capacity. However, they also hold promise in the field of cellular vaccination as they can behave as conditional antigen presenting cells in response to interferon (IFN)-gamma treatment under a specific treatment regimen. This suggests that the immune function of MSCs can be pharmacologically modulated. Given the capacity of the agonist pyrimido-indole derivative UM171a to trigger the expression of various antigen presentation-related genes in human hematopoietic progenitor cells, we explored the potential use of UM171a as a means to pharmacologically instill and/or promote antigen presentation by MSCs.

Methods

Besides completing a series of flow-cytometry-based phenotypic analyses, several functional antigen presentation assays were conducted using the SIINFEKL-specific T-cell clone B3Z. Anti-oxidants and electron transport chain inhibitors were also used to decipher UM171a’s mode of action in MSCs. Finally, the potency of UM171a-treated MSCs was evaluated in the context of therapeutic vaccination using immunocompetent C57BL/6 mice with pre-established syngeneic EG.7T-cell lymphoma.

Results

Treatment of MSCs with UM171a triggered potent increase in H2-K^b cell surface levels along with the acquisition of antigen cross-presentation abilities. Mechanistically, such effects occurred in response to UM171a-mediated production of mitochondrial-derived reactive oxygen species as their neutralization using anti-oxidants or Antimycin-A mitigated MSCs’ ability to cross-present antigens. Processing and presentation of the immunogenic ovalbumin-derived SIINFEKL peptide was caused by de novo expression of the Psmb8 gene in response to UM171a-triggered oxidative stress. When evaluated for their anti-tumoral properties in the context of therapeutic vaccination, UM171a-treated MSC administration to immunocompetent mice with pre-established T-cell lymphoma controlled tumor growth resulting in 40% survival without the need of additional supportive therapy and/or standard-of-care.

Conclusions

Altogether, our findings reveal a new immune-related function for UM171a and clearly allude to a direct link between UM171a-mediated ROS induction and antigen cross-presentation by MSCs. The fact that UM171a treatment modulates MSCs to become antigen-presenting cells without the use of IFN-gamma opens-up a new line of investigation to search for additional agents capable of converting immune-suppressive MSCs to a cellular tool easily adaptable to vaccination.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02693-z.

Stem Cell Transplantation in the Treatment of Type 1 Diabetes Mellitus: From Insulin Replacement to Beta-Cell Replacement

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that attacks pancreatic β-cells, leading to the destruction of insulitis-related islet β-cells. Islet β-cell transplantation has been proven as a curative measure in T1DM. However, a logarithmic increase in the global population with diabetes, limited donor supply, and the need for lifelong immunosuppression restrict the widespread use of β-cell transplantation. Numerous therapeutic approaches have been taken to search for substitutes of β-cells, among which stem cell transplantation is one of the most promising alternatives. Stem cells have demonstrated the potential efficacy to treat T1DM by reconstitution of immunotolerance and preservation of islet β-cell function in recent research. cGMP-grade stem cell products have been used in human clinical trials, showing that stem cell transplantation has beneficial effects on T1DM, with no obvious adverse reactions. To better achieve remission of T1DM by stem cell transplantation, in this work, we explain the progression of stem cell transplantation such as mesenchymal stem cells (MSCs), human embryonic stem cells (hESCs), and bone marrow hematopoietic stem cells (BM-HSCs) to restore the immunotolerance and preserve the islet β-cell function of T1DM in recent years. This review article provides evidence of the clinical applications of stem cell therapy in the treatment of T1DM.

Identification of alpha-enolase as a potential immunogenic molecule during allogeneic transplantation of human adipose-derived mesenchymal stromal cells

BACKGROUND AIMS

Given their low immunogenicity, immunoregulatory effects and multiple differentiation capacity, mesenchymal stromal cells (MSCs) have the potential to be used for "off-the-shelf" cell therapy to treat various diseases. However, the allorejection of MSCs indicates that they are not fully immune-privileged. In this study, the authors investigated the immunogenicity of human adipose-derived MSCs (Ad-MSCs) and identified potential immunogenic molecules.

METHODS

To evaluate the immunogenicity of human Ad-MSCs in vivo, cells were transplanted into humanized mice (hu-mice), then T-cell infiltration and clearance of human Ad-MSCs were observed by immunofluorescence and bioluminescence imaging. One-way mixed lymphocyte reaction and flow cytometry were performed to evaluate the immunogenicity of human Ad-MSCs in vitro. High-throughput T-cell receptor (TCR) repertoire sequencing and mass spectrometry were applied to identified potential immunogenic molecules.

RESULTS

The authors observed that allogeneic Ad-MSCs recruited human T cells and caused faster clearance in hu-mice than non-humanized NOD.Cg-Prkdcscid IL2rgtm1Wjl/SzJ (NSG) mice. The proliferation and activation of T cells were significantly enhanced during in vitro co-culture with human Ad-MSCs. In addition, the level of HLA-II expression on human Ad-MSCs was dramatically increased after co-culture with human peripheral blood mononuclear cells (PBMCs). High-throughput sequencing was applied to analyze the TCR repertoire of the Ad-MSC-recruited T cells to identify dominant TCR CDR3 sequences. Using synthesized TCR CDR3 peptides, the authors identified several potential immunogenic candidates, including alpha-enolase (ENO1). The ENO1 expression level of Ad-MSCs significantly increased after co-culture with PBMCs, whereas ENO1 inhibitor (ENOblock) treatment decreased the expression level of ENO1 and Ad-MSC-induced proliferation of T cells.

CONCLUSIONS

The authors' findings improve the understanding of the immunogenicity of human Ad-MSCs and provide a theoretical basis for the safe clinical application of allogeneic MSC therapy.

Safety and Effectiveness of Cell Therapy in Neurodegenerative Diseases: Take-Home Messages From a Pilot Feasibility Phase I Study of Progressive Supranuclear Palsy

Mesenchymal stromal cells (MSCs) are multipotent cells with anti-inflammatory properties. Here we tested the safety of MSCs in patients with progressive supranuclear palsy (PSP; ClinicalTrials.gov: NCT01824121; Eudract No. 2011-004051-39). Seven patients were treated. To improve the safety, protocol adjustments were made during the performance of the study. The objectives of our work were: (1) to assess the safety of MSCs and (2) to identify critical issues in cell therapies for neurodegenerative diseases. Autologous MSCs from the bone marrow of PSP patients were administered through the internal carotid arteries. 1-year survival and number of severe adverse events were considered as safety endpoints. Clinical rating scales, neuropsychological assessments, gait and posture analysis, single-photon emission computed tomography, positron emission tomography, and brain magnetic resonance (BMR) were performed at different follow-up times. Peripheral blood levels of inflammatory cytokines were measured before and after cell infusion. Six of the seven treated patients were living 1 year after cell infusion. Asymptomatic spotty lesions were observed at BMR after 24 h in six of the seven treated patients. The last patient in the preliminary cohort (Case 5) exhibited transiently symptomatic BMR ischemic alterations. No severe adverse events were recorded in the last two treated patients. Interleukin-8 serum concentrations decreased in three patients (Case 2, 3, and 4). An adaptive study design, appropriate and up-to-date efficacy measures, adequate sample size estimation, and, possibly, the use of a cellular and/or allogeneic cell sources may help in performing phase II trials in the field.

From Primary MSC Culture of Adipose Tissue to Immortalized Cell Line Producing Cytokines for Potential Use in Regenerative Medicine Therapy or Immunotherapy

For twenty-five years, attempts have been made to use MSCs in the treatment of various diseases due to their regenerative and immunomodulatory properties. However, the results are not satisfactory. Assuming that MSCs can be replaced in some therapies by the active factors they produce, the immortalized MSCs line was established from human adipose tissue (HATMSC1) to produce conditioned media and test its regenerative potential in vitro in terms of possible clinical application. The production of biologically active factors by primary MSCs was lower compared to the HATMSC1 cell line and several factors were produced only by the cell line. It has been shown that an HATMSC1-conditioned medium increases the proliferation of various cell types, augments the adhesion of cells and improves endothelial cell function. It was found that hypoxia during culture resulted in an augmentation in the pro-angiogenic factors production, such as VEGF, IL-8, Angiogenin and MCP-1. The immunomodulatory factors caused an increase in the production of GM-CSF, IL-5, IL-6, MCP-1, RANTES and IL-8. These data suggest that these factors, produced under different culture conditions, could be used for different medical conditions, such as in regenerative medicine, when an increased concentration of pro-angiogenic factors may be beneficial, or in inflammatory diseases with conditioned media with a high concentration of immunomodulatory factors.

Melanocytes as emerging key players in niche regulation of limbal epithelial stem cells

PURPOSE

Limbal melanocytes (LMel) represent essential components of the corneal epithelial stem cell niche and are known to protect limbal epithelial stem/progenitor cells (LEPCs) from UV damage by transfer of melanosomes. Here, we explored additional functional roles for LMel in niche homeostasis, immune regulation and angiostasis.

METHODS

Human corneoscleral tissues were morphologically analyzed in normal, inflammatory and wound healing conditions. The effects of LMel on LEPCs were analyzed in direct and indirect co-culture models using electron microscopy, immunocytochemistry, qRT-PCR, Western blotting and functional assays; limbal mesenchymal stromal cells and murine embryonic 3T3 fibroblasts served as controls. The immunophenotype of LMel was assessed by flow cytometry before and after interferon-γ stimulation, and their immunomodulatory properties were analyzed by mixed lymphocytes reaction, monocyte adhesion assays and cytometric bead arrays. Their angiostatic effects on human umbilical cord endothelial cells (HUVECs) were evaluated by proliferation, migration, and tube formation assays.

RESULTS

LMel and LEPCs formed structural units in the human limbal stem cell niche in situ, which could be functionally replicated, including melanosome transfer, by co-cultivation in vitro. LMel supported LEPCs during clonal expansion and during epithelial wound healing by stimulating proliferation and migration, and suppressed their differentiation through direct contact and paracrine effects. Under inflammatory conditions, LMel were increased in numbers and upregulated expression of ICAM-1 and MHC II molecules (HLA-DR), but lacked expression of HLA-G, -DP, -DQ and costimulatory molecules CD80 and CD86. They were also found to be potent suppressors of alloreactive T- cell proliferation and cytokine secretion, which largely depended on direct cell-cell interaction. Moreover, the LMel secretome exerted angiostatic activity by inhibiting vascular endothelial cell proliferation and capillary network formation.

CONCLUSION

These findings suggest that LMel are not only professional melanin-producing cells, but exert various non-canonical functions in limbal niche homeostasis by regulating LEPC maintenance, immune responses, and angiostasis. Their potent regulatory, immunomodulatory and anti-angiogenic properties may have important implications for future regenerative cell therapies.

Preclinical Evaluation of the Safety and Immunological Action of Allogeneic ADSC-Collagen Scaffolds in the Treatment of Chronic Ischemic Cardiomyopathy

The use of allogeneic adipose-derived mesenchymal stromal cells (alloADSCs) represents an attractive approach for treating myocardial infarction (MI). Furthermore, adding a natural support improves alloADSCs engraftment and survival in heart tissues, leading to a greater therapeutic effect. We aimed to examine the safety and immunological reaction induced by epicardial implantation of a clinical-grade collagen scaffold (CS) seeded with alloADSCs for its future application in humans. Thus, cellularized scaffolds were myocardially or subcutaneously implanted in immunosuppressed rodent models. The toxicological parameters were not significantly altered, and tumor formation was not found over the short or long term. Furthermore, biodistribution analyses in the infarcted immunocompetent rats displayed cell engraftment in the myocardium but no migration to other organs. The immunogenicity of alloADSC-CS was also evaluated in a preclinical porcine model of chronic MI; no significant humoral or cellular alloreactive responses were found. Moreover, CS cellularized with human ADSCs cocultured with human allogeneic immune cells produced no alloreactive response. Interestingly, alloADSC-CS significantly inhibited lymphocyte responses, confirming its immunomodulatory action. Thus, alloADSC-CS is likely safe and does not elicit any alloreactive immunological response in the host. Moreover, it exerts an immunomodulatory action, which supports its translation to a clinical setting.

Processing and Ex Vivo Expansion of Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells for the Development of an Advanced Therapy Medicinal Product for use in Humans

Adipose tissue (AT) represents a commonly used source of mesenchymal stem/stromal cells (MSCs) whose proregenerative potential has been widely investigated in multiple clinical trials worldwide. However, the standardization of the manufacturing process of MSC-based cell therapy medicinal products in compliance with the requirements of the local authorities is obligatory and will allow us to obtain the necessary permits for product administration according to its intended use. Within the research phase (RD), we optimized the protocols used for the processing and ex vivo expansion of AT-derived MSCs (AT-MSCs) for the development of an Advanced Therapy Medicinal Product (ATMP) for use in humans. Critical process parameters (including, e.g., the concentration of enzyme used for AT digestion, cell culture conditions) were identified and examined to ensure the high quality of the final product containing AT-MSCs. We confirmed the identity of isolated AT-MSCs as MSCs and their trilineage differentiation potential according to the International Society for Cellular Therapy (ISCT) recommendations. Based on the conducted experiments, in-process quality control (QC) parameters and acceptance criteria were defined for the manufacturing of hospital exemption ATMP (HE-ATMP). Finally, we conducted a validation of the manufacturing process in a GMP facility. In the current study, we presented a process approach leading to the optimization of processing and the ex vivo expansion of AT-MSCs for the development of ATMP for use in humans.

Immune modulation via adipose derived Mesenchymal Stem cells is driven by donor sex in vitro

Mesenchymal stromal/stem cells (MSCs) are currently being used in clinical trials as proposed treatments for a large range of genetic, immunological, orthopaedic, cardiovascular, endocrine and neurological disorders. MSCs are potent anti-inflammatory mediators which are considered immune evasive and employ a large range of secreted vesicles to communicate and repair damaged tissue. Despite their prolific use in therapy, sex specific mechanism of action is rarely considered as a potential confounding factor for use. The purpose of this study was to examine the potency and functionality of both female and male adipose derived MSCs in order to gain further insights into donor selection. Methods MSC were expanded to passage 4, secretome was harvested and stored at − 80c. To assess potency MSC were also primed and assessed via functional immune assays, ELISA, multiplex and immunophenotyping. Results Female MSCs (fMSC), consistently suppressed Peripheral blood mononuclear cell (PBMC) proliferation significantly (p < 0.0001) more than male MSC (mMSC). In co-culture mPBMCs, showed 60.7 ± 15.6% suppression with fMSCs compared with 22.5 ± 13.6% suppression with mMSCs. Similarly, fPBMCs were suppressed by 67.9 ± 10.4% with fMSCs compared to 29.4 ± 9.3% with mMSCs. The enhanced immunosuppression of fMSCs was attributed to the production of higher concentrations of the anti-inflammatory mediators such as IDO1 (3301 pg/mL vs 1699 pg/mL) and perhaps others including IL-1RA (1025 pg/mL vs 701 pg/mL), PGE-2 (6142 pg/mL vs 2448 pg/mL) and prolonged expression of VCAM-1 post activation relative to mMSCs. In contrast, mMSCs produces more inflammatory G-CSF than fMSCs (806 pg/mL vs 503 pg/mL). Moreover, IDO1 expression was correlated to immune suppression and fMSCs, but not mMSCs induced downregulation of the IL-2 receptor and sustained expression of the early T cell activation marker, CD69 in PBMCs further highlighting the differences in immunomodulation potentials between the sexes. Conclusion In conclusion, our data shows that female MSC are more potent in vitro than their male counterparts. The inability of male MSC to match female MSC driven immunomodulation and to use the inflammatory microenvironment to their advantage is evident and is likely a red flag when using allogeneic male MSC as a therapeutic for disease states.

Engineering Strategies for Allogeneic Solid Tissue Acceptance

Advances in allogeneic transplantation of solid organs and tissues depend on our understanding of mechanisms that mediate the prevention of graft rejection. For the past decades, clinical practice has established guidelines to prevent allograft rejection, which mostly rely on the intake of nontargeted immunosuppressants as the gold standard. However, such lifelong regimens have been reported to trigger severe morbidities and commonly fail in preventing late allograft loss. In this review, the biology of allogeneic rejection and self-tolerance is analyzed, as well as the mechanisms of cellular-based therapeutics driving suppression and/or tolerance. Bioinspired engineering strategies that take advantage of cells, biomaterials, or combinations thereof to prevent allograft rejection are addressed, as well as biological mechanisms that drive their efficacy.

The Unique Immunomodulatory Properties of MSC-Derived Exosomes in Organ Transplantation

Methods for suppressing the host immune system over the long term and improving transplantation tolerance remain a primary issue in organ transplantation. Cell therapy is an emerging therapeutic strategy for immunomodulation after transplantation. Mesenchymal stem cells (MSCs) are adult multipotent stem cells with wide differentiation potential and immunosuppressive properties, which are mostly used in regenerative medicine and immunomodulation. In addition, emerging research suggests that MSC-derived exosomes have the same therapeutic effects as MSCs in many diseases, while avoiding many of the risks associated with cell transplantation. Their unique immunomodulatory properties are particularly important in the immune system-overactive graft environment. In this paper, we review the effects of MSC-derived exosomes in the immune regulation mechanism after organ transplantation and graft-versus-host disease (GvHD) from various perspectives, including immunosuppression, influencing factors, anti-inflammatory properties, mediation of tissue repair and regeneration, and the induction of immune tolerance. At present, the great potential of MSC-derived exosomes in immunotherapy has attracted a great deal of attention. Furthermore, we discuss the latest insights on MSC-derived exosomes in organ transplantation and GvHD, especially its commercial production concepts, which aim to provide new strategies for improving the prognosis of organ transplantation patients.

Tumor immune microenvironment-based classifications of bladder cancer for enhancing the response rate of immunotherapy

Immunotherapy is a potential way to save the lives of patients with bladder cancer, but it only benefits approximately 20% of them. A total of 4,028 bladder cancer patients were collected for this study. Unsupervised non-negative matrix factorization and the nearest template prediction algorithms were employed for the classification. We identified the immune and non-immune classes from The Cancer Genome Atlas Bladder Urothelial Carcinoma (TCGA-BLCA) training cohort. The 150 most differentially expressed genes between these two classes were extracted, and the classification reappeared in 20 validation cohorts. For the activated and exhausted subgroups, a stromal activation signature was assessed by the NTP algorithm. Patients in the immune class showed highly enriched signatures of immunocytes, while the exhausted subgroup also exhibited activated transforming growth factor (TGF)-β1, and cancer-associated extracellular matrix signatures. Patients in the immune-activated subgroup showed a lower genetic alteration and better overall survival. Anti-PD-1/PD-L1 immunotherapy was more beneficial for the immune-activated subgroup, while immune checkpoint blockade therapy plus a TGF-β inhibitor or an EP300 inhibitor might achieve greater efficacy for patients in the immune-exhausted subgroup. Novel immune molecular classifier was identified for the innovative immunotherapy of patients with bladder cancer.

Role of prostaglandin E2 in allogeneic mesenchymal stem cell therapy for cardiac repair

Ischemic heart disease is among the primary causes of cardiovascular-related deaths worldwide. Conventional treatments including surgical interventions and medical therapies aid in preventing further damage to heart muscle but are unable to provide a permanent solution. In recent years, stem cell therapy has emerged as an attractive alternative to restore damaged myocardium after myocardial injury. Allogeneic (donor-derived) mesenchymal stem cells (MSCs) have shown great promise in preclinical and clinical studies, making them the most widely accepted candidates for cardiac cell therapy. MSCs promote cardiac repair by modulating host immune system and secreting various soluble factors, of which prostaglandin E2 (PGE2) is an important one. PGE2 plays a significant role in regulating cardiac remodeling following myocardial injury. In this review, we provide an overview of allogeneic MSCs as candidates for myocardial regeneration with a focus on the role of the PGE2/cyclooxygenase-2 (COX2) pathway in mediating these effects.

Mesenchymal Stem cells in the context of canine atopic dermatitis: A Review

ABSTRACT Canine atopic dermatitis (CAD) is a chronic inflammatory skin disease and has a high frequency among dermatological diseases. The interaction of genetic factors, skin and environmental conditions affect the expression of the disease, developing a complex pathology. Current multimodal treatment has numerous adverse effects and variations in its efficacy and safety, demonstrating the need to develop safe and effective therapeutic resources for patients with CAD. Mesenchymal stem cells (MSCs) are multipotent cells, with special characteristics, such as self-renewal, immunomodulatory properties, and de-differentiation, making them useful for several clinical problems. The discovery of the immunosuppressive effect of MSCs on T cells has opened the potential for new perspectives with its use as a therapeutic agent for immune diseases, such as CAD. The scarce number of research using the MSC as a treatment for CAD result in the lack of knowledge about the benefits and possible protocols to be followed for the use of this cell therapy. In this review, we highlighted the clinical studies and potential biological mechanisms of MSC-based cell therapy effects attenuating canine atopic dermatitis compared to conventional treatment, which might lead to a safe improvement of the animal’s clinical condition in a short period without causing adverse effects.

Obesity induced by high-fat diet is associated with critical changes in biological and molecular functions of mesenchymal stromal cells present in visceral adipose tissue

The mesenchymal stromal cells (MSCs) residing within the stromal component of visceral adipose tissue appear to be greatly affected by obesity, with impairment of their functions and presence of senescence. To gain further insight into these phenomena, we analyzed the changes in total proteome content and secretome of mouse MSCs after a high-fat diet (HFD) treatment compared to a normal diet (ND). In healthy conditions, MSCs are endowed with functions mainly devoted to vesicle trafficking. These cells have an immunoregulatory role, affecting leukocyte activation and migration, acute inflammation phase response, chemokine signaling, and platelet activities. They also present a robust response to stress. We identified four signaling pathways (TGF-β, VEGFR2, HMGB1, and Leptin) that appear to govern the cells' functions. In the obese mice, MSCs showed a change in their functions. The immunoregulation shifted toward pro-inflammatory tasks with the activation of interleukin-1 pathway and of Granzyme A signaling. Moreover, the methionine degradation pathway and the processing of capped intronless pre-mRNAs may be related to the inflammation process. The signaling pathways we identified in ND MSCs were replaced by MET, WNT, and FGFR2 signal transduction, which may play a role in promoting inflammation, cancer, and aging.

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.

Involvement of Mesenchymal Stem Cells in Oral Mucosal Bacterial Immunotherapy

Recent clinical observations indicate that bacterial vaccines induce cross-protection against infections produced by different microorganisms. MV130, a polyvalent bacterial sublingual preparation designed to prevent recurrent respiratory infectious diseases, reduces the infection rate in patients with recurrent respiratory tract infections. On the other hand, mesenchymal stem cells (MSCs) are key cell components that contribute to the maintenance of tissue homeostasis and exert both immunostimulatory and immunosuppressive functions. Herein, we study the effects of MV130 in human MSC functionality as a potential mechanism that contributes to its clinical benefits. We provide evidence that during MV130 sublingual immunization of mice, resident oral mucosa MSCs can take up MV130 components and their numbers remain unchanged after vaccination, in contrast to granulocytes that are recruited from extramucosal tissues. MSCs treated in vitro with MV130 show an increased viability without affecting their differentiation potential. In the short-term, MSC treatment with MV130 induces higher leukocyte recruitment and T cell expansion. In contrast, once T-cell activation is initiated, MV130 stimulation induces an up-regulated expression of immunosuppressor factors in MSCs. Accordingly, MV130-primed MSCs reduce T lymphocyte proliferation, induce the differentiation of dendritic cells with immunosuppressive features and favor M2-like macrophage polarization, thus counterbalancing the immune response. In addition, MSCs trained with MV130 undergo functional changes, enhancing their immunomodulatory response to a secondary stimulus. Finally, we show that MSCs are able to uptake, process and retain a reservoir of the TLR ligands derived from MV130 digestion which can be subsequently transferred to dendritic cells, an additional feature that also may be associated to trained immunity.

Mesenchymal Stromal Cells as Critical Contributors to Tissue Regeneration

Adult stem cells that are tightly regulated by the specific microenvironment, or the stem cell niche, function to maintain tissue homeostasis and regeneration after damage. This demands the existence of specific niche components that can preserve the stem cell pool in injured tissues and restore the microenvironment for their subsequent appropriate functioning. This role may belong to mesenchymal stromal cells (MSCs) due to their resistance to damage signals and potency to be specifically activated in response to tissue injury and promote regeneration by different mechanisms. Increased amount of data indicate that activated MSCs are able to produce factors such as extracellular matrix components, growth factors, extracellular vesicles and organelles, which transiently substitute the regulatory signals from missing niche cells and restrict the injury-induced responses of them. MSCs may recruit functional cells into a niche or differentiate into missing cell components to endow a niche with ability to regulate stem cell fates. They may also promote the dedifferentiation of committed cells to re-establish a pool of functional stem cells after injury. Accumulated evidence indicates the therapeutic promise of MSCs for stimulating tissue regeneration, but the benefits of administered MSCs demonstrated in many injury models are less than expected in clinical studies. This emphasizes the importance of considering the mechanisms of endogenous MSC functioning for the development of effective approaches to their pharmacological activation or mimicking their effects. To achieve this goal, we integrate the current ideas on the contribution of MSCs in restoring the stem cell niches after damage and thereby tissue regeneration.

Mesenchymal Stromal Cell Immunology for Efficient and Safe Treatment of Osteoarthritis

Mesenchymal stem cell (MSC) therapy represents a promising approach for the treatment of osteoarthritis (OA). MSCs can be readily isolated from multiple sources and expanded ex vivo for possible clinical application. They possess a unique immunological profile and regulatory machinery that underline their therapeutic effects. They also have the capacity to sense the changes within the tissue environment to display the adequate response. Indeed, there is a close interaction between MSCs and the host cells. Accordingly, MSCs demonstrate encouraging results for a variety of diseases including OA. However, their effectiveness needs to be improved. In this review, we selected to discuss the importance of the immunological features of MSCs, including the type of transplantation and the immune and blood compatibility. It is important to consider MSC immune evasive rather than immune privileged. We also highlighted some of the actions/mechanisms that are displayed during tissue healing including the response of MSCs to injury signals, their interaction with the immune system, and the impact of their lifespan. Finally, we briefly summarized the results of clinical studies reporting on the application of MSCs for the treatment of OA. The research field of MSCs is inspiring and innovative but requires more knowledge about the immunobiological properties of these cells. A better understanding of these features will be key for developing a safe and efficient medicinal product for clinical use in OA.

Dual Bioelectrical Assessment of Human Mesenchymal Stem Cells Using Plasma and Mitochondrial Membrane Potentiometric Probes

Background: Bioelectrical properties are known to impact stem cell fate, state, and function. However, assays that measure bioelectrical properties are generally limited to the plasma membrane potential. In this study, we propose an assay to simultaneously assess cell plasma membrane and mitochondrial membrane potentials. Materials and Methods: Mesenchymal stem cell (MSC) plasma and mitochondrial membrane potentials were measured using flow cytometry and a combination of tetramethylrhodamine, methyl ester (TMRM), and bis-(1,3-dibutylbarbituric acid)trimethine oxonol (DiBAC) dyes. We investigated the shifts in the bioelectrical phenotype of MSCs due to extended culture in vitro, activation with interferon-gamma (IFN-γ), and aggregate conditions. Results: MSCs subjected to extended culture in vitro acquired plasma and mitochondrial membrane potentials consistent with a hyperpolarized bioelectrical phenotype. Activation with IFN-γ shifted MSCs toward a state associated with increased levels of both DiBAC and TMRM. MSCs in aggregate conditions were associated with a decrease in TMRM levels, indicating mitochondrial depolarization. Conclusions: Our proposed assay described distinct MSC bioelectrical transitions due to extended in vitro culture, exposure to an inflammatory cytokine, and culture under aggregate conditions. Overall, our assay enables a more complete characterization of MSC bioelectrical properties within a single experiment, and its relative simplicity enables researchers to apply it in variety of settings.

Mesenchymal stromal cells as potential immunomodulatory players in severe acute respiratory distress syndrome induced by SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus-2 and the related coronavirus disease-19 (COVID-19) is a worldwide emerging situation, which was initially reported in December 2019 in Wuhan, China. Currently, more than 7258842 new cases, and more than 411879 deaths have been reported globally. This new highly transmitted coronavirus is responsible for the development of severe acute respiratory distress syndrome. Due to this disorder, a great number of patients are hospitalized in the intensive care unit followed by connection to extracorporeal membrane oxygenation for breath supporting and survival. Severe acute respiratory distress syndrome is mostly accompanied by the secretion of proinflammatory cytokines, including interleukin (IL)-2, IL-6, IL-7, granulocyte colony-stimulating factor (GSCF), interferon-inducible protein 10 (IP10), monocyte chemotactic protein-1 (MCP1), macrophage inflammatory protein 1A (MIP1A), and tumor necrosis factor alpha (TNF-α), an event which is known as "cytokine storm". Further disease pathology involves a generalized modulation of immune responses, leading to fatal multiorgan failure. Currently, no specific treatment or vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been developed. Mesenchymal stromal cells (MSCs), which are known for their immunosuppressive actions, could be applied as an alternative co-therapy in critically-ill COVID-19 patients. Specifically, MSCs can regulate the immune responses through the conversion of Th1 to Th2, activation of M2 macrophages, and modulation of dendritic cells maturation. These key immunoregulatory properties of MSCs may be exerted either by produced soluble factors or by cell-cell contact interactions. To date, several clinical trials have been registered to assess the safety, efficacy, and therapeutic potential of MSCs in COVID-19. Moreover, MSC treatment may be effective for the reversion of ground-glass opacity of damaged lungs and reduce the tissue fibrosis. Taking into account the multifunctional properties of MSCs, the proposed stem-cell-based therapy may be proven significantly effective in critically-ill COVID-19 patients. The current therapeutic strategy may improve the patient's overall condition and in parallel may decrease the mortality rate of the current disease.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Stem cell homing: From physiology to therapeutics

Stem cell homing is a multistep endogenous physiologic process that is also used by exogenously administered hematopoietic stem and progenitor cells (HSPCs). This multistep process involves cell migration and is essential for hematopoietic stem cell transplantation. The process can be manipulated to enhance ultimate engraftment potential, and understanding stem cell homing is also important to the understanding of stem cell mobilization. Homing is also of potential importance in the recruitment of marrow mesenchymal stem and stromal cells (MSCs) to sites of injury and regeneration. This process is less understood but assumes importance when these cells are used for repair purposes. In this review, the process of HSPC and MSC homing is examined, as are methods to enhance this process.

Stem Cells in Veterinary Medicine-Current State and Treatment Options

Regenerative medicine is a branch of medicine that develops methods to grow, repair, or replace damaged or diseased cells, organs or tissues. It has gained significant momentum in recent years. Stem cells are undifferentiated cells with the capability to self—renew and differentiate into tissue cells with specialized functions. Stem cell therapies are therefore used to overcome the body's inability to regenerate damaged tissues and metabolic processes after acute or chronic insult. The concept of stem cell therapy was first introduced in 1991 by Caplan, who proposed that massive differentiation of cells into the desired tissue could be achieved by isolation, cultivation, and expansion of stem cells in in vitro conditions. Among different stem cell types, mesenchymal stem cells (MSC) currently seem to be the most suitable for therapeutic purposes, based on their simple isolation and culturing techniques, and lack of ethical issues regarding their usage. Because of their remarkable immunomodulatory abilities, MSCs are increasingly gaining recognition in veterinary medicine. Developments are primarily driven by the limitations of current treatment options for various medical problems in different animal species. MSCs represent a possible therapeutic option for many animal diseases, such as orthopedic, orodental and digestive tract diseases, liver, renal, cardiac, respiratory, neuromuscular, dermal, olfactory, and reproductive system diseases. Although we are progressively gaining an understanding of MSC behavior and their mechanisms of action, some of the issues considering their use for therapy are yet to be resolved. The aim of this review is first to summarize the current knowledge and stress out major issues in stem cell based therapies in veterinary medicine and, secondly, to present results of clinical usage of stem cells in veterinary patients.

Inflammation in myocardial injury- Stem cells as potential immunomodulators for myocardial regeneration and restoration

The ineffective immunosuppressant's and targeted strategies to neutralize inflammatory mediators have worsened the scenario of heart failure and have opened many questions for debate. Stem cell therapy has proven to be a promising approach for treating heart following myocardial infarction (MI). Adult stem cells, induced pluripotent stem cells and embryonic stem cells are possible cell types and have successfully shown to regenerate damaged myocardial tissue in pre-clinical and clinical studies. Current implications of using mesenchymal stem cells (MSCs) owing to their immunomodulatory functions and paracrine effects could serve as an effective alternative treatment option for rejuvenating the heart post MI. The major setback associated with the use of MSCs is reduced cell retention, engraftment and decreased effectiveness. With a few reports on understanding the role of inflammation and its dual effects on the structure and function of heart, this review focuses on these missing insights and further exemplifies the role of MSCs as an alternative therapy in treating the pathological consequences in myocardial infarction (MI).

Mesenchymal Stem Cells Beyond Regenerative Medicine

Mesenchymal stem cells (MSCs) are competent suitors of cellular therapy due to their therapeutic impact on tissue degeneration and immune-based pathologies. Additionally, their homing and immunomodulatory properties can be exploited in cancer malignancies to transport pharmacological entities, produce anti-neoplastic agents, or induce anti-tumor immunity. Herein, we create a portfolio for MSC properties, showcasing their distinct multiple therapeutic utilities and successes/challenges thereof in both animal studies and clinical trials. We further highlight the promising potential of MSCs not only in cancer management but also in instigating tumor-specific immunity - i.e., cancer vaccination. Finally, we reflect on the possible reasons impeding the clinical advancement of MSC-based cancer vaccines to assist in contriving novel methodologies from which a therapeutic milestone might emanate.

Therapeutic Mesenchymal Stromal Cells for Immunotherapy and for Gene and Drug Delivery

Mesenchymal stromal cells (MSCs) possess several fairly unique properties that, when combined, make them ideally suited for cellular-based immunotherapy and as vehicles for gene and drug delivery for a wide range of diseases and disorders. Key among these are: (1) their relative ease of isolation from a variety of tissues; (2) the ability to be expanded in culture without a loss of functionality, a property that varies to some degree with tissue source; (3) they are relatively immune-inert, perhaps obviating the need for precise donor/recipient matching; (4) they possess potent immunomodulatory functions that can be tailored by so-called licensing in vitro and in vivo; (5) the efficiency with which they can be modified with viral-based vectors; and (6) their almost uncanny ability to selectively home to damaged tissues, tumors, and metastases following systemic administration. In this review, we summarize the latest research in the immunological properties of MSCs, their use as immunomodulatory/anti-inflammatory agents, methods for licensing MSCs to customize their immunological profile, and their use as vehicles for transferring both therapeutic genes in genetic disease and drugs and genes designed to destroy tumor cells.

Mesenchymal Stromal Cells from Fetal and Maternal Placenta Possess Key Similarities and Differences: Potential Implications for Their Applications in Regenerative Medicine

Placenta-derived mesenchymal stromal cells (MSC) have attracted more attention for their immune modulatory properties and poor immunogenicity, which makes them suitable for allogeneic transplantation. Although MSC isolated from different areas of the placenta share several features, they also present significant biological differences, which might point to distinct clinical applications. Hence, we compared cells from full term placenta distinguishing them on the basis of their origin, either maternal or fetal. We used cells developed by Pluristem LTD: PLacenta expanded mesenchymal-like adherent stromal cells (PLX), maternal-derived cells (PLX-PAD), fetal-derived cells (PLX-R18), and amniotic membrane-derived MSC (hAMSC). We compared immune modulatory properties evaluating effects on T-lymphocyte proliferation, expression of cytotoxicity markers, T-helper and T-regulatory cell polarization, and monocyte differentiation toward antigen presenting cells (APC). Furthermore, we investigated cell immunogenicity. We show that MSCs and MSC-like cells from both fetal and maternal sources present immune modulatory properties versus lymphoid (T cells) and myeloid (APC) cells, whereby fetal-derived cells (PLX-R18 and hAMSC) have a stronger capacity to modulate immune cell proliferation and differentiation. Our results emphasize the importance of understanding the cell origin and characteristics in order to obtain a desired result, such as modulation of the inflammatory response that is critical in fostering regenerative processes.