Human Mesenchymal Stem Cells Promote Survival of T Cells in a Quiescent State

Advances in Stem Cell-Based Therapies in the Treatment of Osteoarthritis

Osteoarthritis (OA) is a chronic, degenerative joint disease presenting a significant global health threat. While current therapeutic approaches primarily target symptom relief, their efficacy in repairing joint damage remains limited. Recent research has highlighted mesenchymal stem cells (MSCs) as potential contributors to cartilage repair, anti-inflammatory modulation, and immune regulation in OA patients. Notably, MSCs from different sources and their derivatives exhibit variations in their effectiveness in treating OA. Moreover, pretreatment and gene editing techniques of MSCs can enhance their therapeutic outcomes in OA. Additionally, the combination of novel biomaterials with MSCs has shown promise in facilitating the repair of damaged cartilage. This review summarizes recent studies on the role of MSCs in the treatment of OA, delving into their advantages and exploring potential directions for development, with the aim of providing fresh insights for future research in this critical field.

Polarized Anti-Inflammatory Mesenchymal Stem Cells Increase Hippocampal Neurogenesis and Improve Cognitive Function in Aged Mice

Age-related decline in cognitive functions is associated with reduced hippocampal neurogenesis caused by changes in the systemic inflammatory milieu. Mesenchymal stem cells (MSC) are known for their immunomodulatory properties. Accordingly, MSC are a leading candidate for cell therapy and can be applied to alleviate inflammatory diseases as well as aging frailty via systemic delivery. Akin to immune cells, MSC can also polarize into pro-inflammatory MSC (MSC1) and anti-inflammatory MSC (MSC2) following activation of Toll-like receptor 4 (TLR4) and TLR3, respectively. In the present study, we apply pituitary adenylate cyclase-activating peptide (PACAP) to polarize bone-marrow-derived MSC towards an MSC2 phenotype. Indeed, we found that polarized anti-inflammatory MSC were able to reduce the plasma levels of aging related chemokines in aged mice (18-months old) and increased hippocampal neurogenesis following systemic administration. Similarly, aged mice treated with polarized MSC displayed improved cognitive function in the Morris water maze and Y-maze assays compared with vehicle- and naïve-MSC-treated mice. Changes in neurogenesis and Y-maze performance were negatively and significantly correlated with sICAM, CCL2 and CCL12 serum levels. We conclude that polarized PACAP-treated MSC present anti-inflammatory properties that can mitigate age-related changes in the systemic inflammatory milieu and, as a result, ameliorate age related cognitive decline.

Advances in Mesenchymal Stem Cell Therapy for Osteoarthritis: From Preclinical and Clinical Perspectives

The prevalence of osteoarthritis (OA), a degenerative disorder of joints, has substantially increased in recent years. Its key pathogenic hallmarks include articular cartilage destruction, synovium inflammation, and bone remodeling. However, treatment outcomes are unsatisfactory. Until recently, common therapy methods, such as analgesic and anti-inflammatory treatments, were aimed to treat symptoms that cannot be radically cured. Mesenchymal stem cells (MSCs), i.e., mesoderm non-hematopoietic cells separated from bone marrow, adipose tissue, umbilical cord blood, etc., have been intensively explored as an emerging technique for the treatment of OA over the last few decades. According to existing research, MSCs may limit cartilage degradation in OA by interfering with cellular immunity and secreting a number of active chemicals. This study aimed to examine the potential mechanism of MSCs in the treatment of OA and conduct a thorough review of both preclinical and clinical data.

Modulation of Mesenchymal Stem Cells-Mediated Adaptive Immune Effectors' Repertoire in the Recovery of Systemic Lupus Erythematosus

The breakdown of self-tolerance of the immune response can lead to autoimmune conditions in which chronic inflammation induces tissue damage. Systemic lupus erythematosus (SLE) is a debilitating multisystemic autoimmune disorder with a high prevalence in women of childbearing age; however, SLE incidence, prevalence, and severity are strongly influenced by ethnicity. Although the mystery of autoimmune diseases remains unsolved, disturbance in the proportion and function of B cell subsets has a major role in SLE's pathogenesis. Additionally, colocalizing hyperactive T helper cell subgroups within inflammatory niches are indispensable. Despite significant advances in standard treatments, nonspecific immunosuppression, the risk of serious infections, and resistance to conventional therapies in some cases have raised the urgent need for new treatment strategies. Without the need to suppress the immune system, mesenchymal stem cells (MSCs), as ''smart" immune modulators, are able to control cellular and humoral auto-aggression responses by participating in precursor cell development. In lupus, due to autologous MSCs disorder, the ability of allogenic engrafted MSCs in tissue regeneration and resetting immune homeostasis with the provision of a new immunocyte repertoire has been considered simultaneously. In Brief The bone marrow mesenchymal stem cells (BM-MSCs) lineage plays a critical role in maintaining the hematopoietic stem-cell microstructure and modulating immunocytes. The impairment of BM-MSCs and their niche partially contribute to the pathogenesis of SLE-like diseases. Allogenic MSC transplantation can reconstruct BM microstructure, possibly contributing to the recovery of immunocyte phenotype restoration of immune homeostasis. In terms of future prospects of MSCs, artificially gained by ex vivo isolation and culture adaptation, the wide variety of potential mediators and mechanisms might be linked to the promotion of the immunomodulatory function of MSCs.

Transfer of mesenchymal stem cell mitochondria to CD4+ T cells contributes to repress Th1 differentiation by downregulating T-bet expression

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) are multipotent cells with strong tissue repair and immunomodulatory properties. Due to their ability to repress pathogenic immune responses, and in particular T cell responses, they show therapeutic potential for the treatment of autoimmune diseases, organ rejection and graft versus host disease. MSCs have the remarkable ability to export their own mitochondria to neighboring cells in response to injury and inflammation. However, whether mitochondrial transfer occurs and has any role in the repression of CD4⁺ Th1 responses is unknown.

METHODS AND RESULTS

In this report we have utilized CD4⁺ T cells from HNT TCR transgenic mice that develop Th1-like responses upon antigenic stimulation in vitro and in vivo. Allogeneic bone marrow-derived MSCs reduced the diabetogenic potential of HNT CD4⁺ T cells in vivo in a transgenic mouse model of disease. In co-culture experiments, we have shown that MSCs were able to reduce HNT CD4⁺ T cell expansion, expression of key effector markers and production of the effector cytokine IFNγ after activation. This was associated with the ability of CD4⁺ T cells to acquire mitochondria from MSCs as evidenced by FACS and confocal microscopy. Remarkably, transfer of isolated MSC mitochondria to CD4⁺ T cells resulted in decreased T cell proliferation and IFNγ production. These effects were additive with those of prostaglandin E2 secreted by MSCs. Finally, we demonstrated that both co-culture with MSCs and transfer of isolated MSC mitochondria prevent the upregulation of T-bet, the master Th1 transcription factor, on activated CD4⁺ T cells.

CONCLUSION

The present study demonstrates that transfer of MSC mitochondria to activated CD4⁺ T cells results in the suppression of Th1 responses in part by downregulating T-bet expression. Furthermore, our studies suggest that MSC mitochondrial transfer might represent a general mechanism of MSC-dependent immunosuppression.

Mesenchymal Stem Cells and Their Exocytotic Vesicles

Mesenchymal stem cells (MSCs), as a kind of pluripotent stem cells, have attracted much attention in orthopedic diseases, geriatric diseases, metabolic diseases, and sports functions due to their osteogenic potential, chondrogenic differentiation ability, and adipocyte differentiation. Anti-inflammation, anti-fibrosis, angiogenesis promotion, neurogenesis, immune regulation, and secreted growth factors, proteases, hormones, cytokines, and chemokines of MSCs have been widely studied in liver and kidney diseases, cardiovascular and cerebrovascular diseases. In recent years, many studies have shown that the extracellular vesicles of MSCs have similar functions to MSCs transplantation in all the above aspects. Here we review the research progress of MSCs and their exocrine vesicles in recent years.

Mesenchymal Stem Cells in Radiation-Induced Pulmonary Fibrosis: Future Prospects

Radiation-induced pulmonary fibrosis (RIPF) is a general and fatal side effect of radiotherapy, while the pathogenesis has not been entirely understood yet. By now, there is still no effective clinical intervention available for treatment of RIPF. Recent studies revealed mesenchymal stromal cells (MSCs) as a promising therapy treatment due to their homing and differentiation ability, paracrine effects, immunomodulatory effects, and MSCs-derived exosomes. Nevertheless, problems and challenges in applying MSCs still need to be taken seriously. Herein, we reviewed the mechanisms and challenges in the applications of MSCs in treating RIPF.

Micro-RNAs Shuttled by Extracellular Vesicles Secreted from Mesenchymal Stem Cells Dampen Astrocyte Pathological Activation and Support Neuroprotection in In-Vitro Models of ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no effective cure. Astrocytes display a toxic phenotype in ALS and contribute to motoneuron (MN) degeneration. Modulating astrocytes' neurotoxicity can reduce MN death. Our previous studies showed the beneficial effect of mesenchymal stem cell (MSC) administration in SOD1^G93A ALS mice, but the mechanisms are still unclear. We postulated that the effects could be mediated by extracellular vesicles (EVs) secreted by MSCs. We investigated, by immunohistochemical, molecular, and in vitro functional analyses, the activity of MSC-derived EVs on the pathological phenotype and neurotoxicity of astrocytes isolated from the spinal cord of symptomatic SOD1^G93A mice and human astrocytes (iAstrocytes) differentiated from inducible neural progenitor cells (iNPCs) of ALS patients. In vitro EV exposure rescued mouse and human ALS astrocytes' neurotoxicity towards MNs. EVs significantly dampened the pathological phenotype and neuroinflammation in SOD1^G93A astrocytes. In iAstrocytes, exposure to EVs increased the antioxidant factor Nrf2 and reduced reactive oxygen species. We previously found nine miRNAs upregulated in MSC-derived EVs. Here, the transfection of SOD1^G93A astrocytes with single miRNA mimics reduced astrocytes' activation and the expression of neuroinflammatory factors. Moreover, miR-466q and miR-467f mimics downregulate Mapk11, while miR-466m-5p and miR-466i-3p mimics promote the nuclear translocation of Nrf2. In iAstrocytes, transfection with miR-29b-3p mimic upregulated NQO1 antioxidant activity and reduced neurotoxicity towards MNs. MSC-derived EVs modulate astrocytes' reactive phenotype and neurotoxicity through anti-inflammatory and antioxidant-shuttled miRNAs, thus representing a therapeutic strategy in ALS.

Human Mesenchymal Stem Cell Secretome Driven T Cell Immunomodulation Is IL-10 Dependent

The Human Mesenchymal Stem Cell (hMSC) secretome has pleiotropic effects underpinning its therapeutic potential. hMSC serum-free conditioned media (SFCM) contains a variety of cytokines, with previous studies linking a changed secretome composition to physoxia. The Jurkat T cell model allowed the efficacy of SFCM vs. serum-free media (SFM) in the suppression of immunological aspects, including proliferation and polarisation, to be explored. Cell growth in SFM was higher [(21% O2 = 5.3 × 105 ± 1.8 × 104 cells/mL) and (2% O2 = 5.1 × 105 ± 3.0 × 104 cells/mL)], compared to SFCM [(21% O2 = 2.4 × 105 ± 2.5 × 104 cells/mL) and (2% O2 = 2.2 × 105 ± 5.8 × 103 cells/mL)]. SFM supported IL-2 release following activation [(21% O2 = 5305 ± 211 pg/mL) and (2% O2 = 5347 ± 327 pg/mL)] whereas SFCM suppressed IL-2 secretion [(21% O2 = 2461 ± 178 pg/mL) and (2% O2 = 1625 ± 159 pg/mL)]. Anti-inflammatory cytokines, namely IL-4, IL-10, and IL-13, which we previously confirmed as components of hMSC SFCM, were tested. IL-10 neutralisation in SFCM restored proliferation in both oxygen environments (SFM/SFCM+antiIL-10 ~1-fold increase). Conversely, IL-4/IL-13 neutralisation showed no proliferation restoration [(SFM/SFM+antiIL-4 ~2-fold decrease), and (SFM/SFCM+antiIL-13 ~2-fold decrease)]. Present findings indicate IL-10 played an immunosuppressive role by reducing IL-2 secretion. Identification of immunosuppressive components of the hMSC secretome and a mechanistic understanding of their action allow for the advancement and refinement of potential future cell-free therapies.

Autophagy reprogramming stem cell pluripotency and multiple-lineage differentiation

The cellular process responsible for the degradation of cytosolic proteins and subcellular organelles in lysosomes was termed "autophagy." This process occurs at a basal level in most tissues as part of tissue homeostasis that redounds to the regular turnover of components inside cytoplasm. The breakthrough in the autophagy field is the identification of key players in the autophagy pathway, compounded under the name "autophagy-related genes" (ATG) encoding for autophagy effector proteins. Generally, the function of autophagy can be classified into two divisions: intracellular clearance of defective macromolecules and organelles and generation of degradation products. Therapeutic strategies using stem cell-based approach come as a promising therapy and develop rapidly recently as stem cells have high self-renewability and differentiation capability as known as mesenchymal stem cells (MSCs). They are defined as adherent fibroblast-like population with the abilities to self-renew and multi-lineage differentiate into osteogenic, adipogenic, and chondrogenic lineage cells. To date, they are the most extensively applied adult stem cells in clinical trials. The properties of MSCs, such as immunomodulation, neuroprotection, and tissue repair pertaining to cell differentiation, processes to replace lost, or damaged cells, for aiding cell repair and revival. Autophagy has been viewed as a remarkable mechanism for maintaining homeostasis, ensuring the adequate function and survival of long-lived stem cells. In addition, authophagy also plays a remarkable role in protecting stem cells against cellular stress when the stem cell regenerative capacity is harmed in aging and cellular degeneration. Understanding the under-explored mechanisms of MSC actions and expanding the spectrum of their clinical applications may improve the utility of the MSC-based therapeutic approach in the future.

Mesenchymal stem cells empower T cells in the lymph nodes via MCP-1/PD-L1 axis

Mesenchymal stem cells (MSCs) are a type of immunosuppressive stromal cell found in multiple tissues and organs. However, whether MSCs possess immunosupportive characteristics remains unclear. In this study, we showed that the lymph nodes contain immunosupportive MSCs. They produce and secrete a high level of MCP-1 to promote T-cell proliferation and differentiation, in contrast to bone marrow MSCs (BMMSCs), which repress T-cell activation. Unlike BMMSCs, lymph node MSCs (LNMSCs) fail to respond to activated T-cell-induced production of PD-L1 to induce T-cell apoptosis. Mechanistically, MCP-1 activates phospho-Erk to sustain T-cell proliferation and activation while it represses NF-κB/PD-L1 pathway to avoid induction of T-cell apoptosis. Interestingly, inflammatory lymph node-derived LNMSCs abolish their immunosupportive function due to reduction of MCP-1 expression. Finally, we show that systemic infusion of LNMSCs rescues immunosuppression in cytoxan (CTX)-treated mice. This study reveals a previously unrecognized mechanism underlying MSC-based immunoregulation using the MCP-1/PD-L1 axis to energize T cells and suggests a potential to use MSCs to treat immunosuppressive disorders.

Role of the Microenvironment in Mesenchymal Stem Cell-Based Strategies for Treating Human Liver Diseases

Liver disease is a severe health problem that endangers human health worldwide. Mesenchymal stem cell (MSC) therapy is a novel treatment for patients with different liver diseases due to its vast expansion potential and distinctive immunomodulatory properties. Despite several preclinical trials having confirmed the considerable efficacy of MSC therapy in liver diseases, the questionable safety and efficacy still limit its application. As a precursor cell, MSCs can adjust their characteristics in response to the surrounding microenvironment. The microenvironment provides physical and chemical factors essential for stem cell survival, proliferation, and differentiation. However, the mechanisms are still not completely understood. We, therefore, summarized the mechanisms underlying the MSC immune response, especially the interaction between MSCs and the liver microenvironment, discussing how to achieve better therapeutic effects.

Effects of immune cells on mesenchymal stem cells during fracture healing

In vertebrates, bone is considered an osteoimmune system which encompasses functions of a locomotive organ, a mineral reservoir, a hormonal organ, a stem cell pool and a cradle for immune cells. This osteoimmune system is based on cooperatively acting bone and immune cells, cohabitating within the bone marrow. They are highly interdependent, a fact that is confounded by shared progenitors, mediators, and signaling pathways. Successful fracture healing requires the participation of all the precursors, immune and bone cells found in the osteoimmune system. Recent evidence demonstrated that changes of the immune cell composition and function may negatively influence bone healing. In this review, first the interplay between different immune cell types and osteoprogenitor cells will be elaborated more closely. The separate paragraphs focus on the specific cell types, starting with the cells of the innate immune response followed by cells of the adaptive immune response, and the complement system as mediator between them. Finally, a brief overview on the challenges of preclinical testing of immune-based therapeutic strategies to support fracture healing will be given.

Therapeutic Implications of Mesenchymal Stromal Cells and Their Extracellular Vesicles in Autoimmune Diseases: From Biology to Clinical Applications

Mesenchymal stromal cells (MSCs) are perivascular multipotent stem cells originally identified in the bone marrow (BM) stroma and subsequently in virtually all vascularized tissues. Because of their ability to differentiate into various mesodermal lineages, their trophic properties, homing capacity, and immunomodulatory functions, MSCs have emerged as attractive candidates in tissue repair and treatment of autoimmune disorders. Accumulating evidence suggests that the beneficial effects of MSCs may be primarily mediated via a number of paracrine-acting soluble factors and extracellular vesicles (EVs). EVs are membrane-coated vesicles that are increasingly being acknowledged as playing a key role in intercellular communication via their capacity to carry and deliver their cargo, consisting of proteins, nucleic acids, and lipids to recipient cells. MSC-EVs recapitulate the functions of the cells they originate, including immunoregulatory effects but do not seem to be associated with the limitations and concerns of cell-based therapies, thereby emerging as an appealing alternative therapeutic option in immune-mediated disorders. In the present review, the biology of MSCs will be outlined and an overview of their immunomodulatory functions will be provided. In addition, current knowledge on the features of MSC-EVs and their immunoregulatory potential will be summarized. Finally, therapeutic applications of MSCs and MSC-EVs in autoimmune disorders will be discussed.

Crohn's Disease Increases the Mesothelial Properties of Adipocyte Progenitors in the Creeping Fat

Our understanding of the interplay between human adipose tissue and the immune system is limited. The mesothelium, an immunologically active structure, emerged as a source of visceral adipose tissue. After investigating the mesothelial properties of human visceral and subcutaneous adipose tissue and their progenitors, we explored whether the dysfunctional obese and Crohn's disease environments influence the mesothelial/mesenchymal properties of their adipocyte precursors, as well as their ability to mount an immune response. Using a tandem transcriptomic/proteomic approach, we evaluated the mesothelial and mesenchymal expression profiles in adipose tissue, both in subjects covering a wide range of body-mass indexes and in Crohn's disease patients. We also isolated adipose tissue precursors (adipose-derived stem cells, ASCs) to assess their mesothelial/mesenchymal properties, as well as their antigen-presenting features. Human visceral tissue presented a mesothelial phenotype not detected in the subcutaneous fat. Only ASCs from mesenteric adipose tissue, named creeping fat, had a significantly higher expression of the hallmark mesothelial genes mesothelin (MSLN) and Wilms' tumor suppressor gene 1 (WT1), supporting a mesothelial nature of these cells. Both lean and Crohn's disease visceral ASCs expressed equivalent surface percentages of the antigen-presenting molecules human leucocyte antigen-DR isotype (HLA-DR) and CD86. However, lean-derived ASCs were predominantly HLA-DR ^dim, whereas in Crohn's disease, the HLA-DR ^bright subpopulation was increased 3.2-fold. Importantly, the mesothelial-enriched Crohn's disease precursors activated CD4⁺ T-lymphocytes. Our study evidences a mesothelial signature in the creeping fat of Crohn's disease patients and its progenitor cells, the latter being able to present antigens and orchestrate an immune response.

Harnessing the ECM Microenvironment to Ameliorate Mesenchymal Stromal Cell-Based Therapy in Chronic Lung Diseases

It is known that the cell environment such as biomechanical properties and extracellular matrix (ECM) composition dictate cell behaviour including migration, proliferation, and differentiation. Important constituents of the microenvironment, including ECM molecules such as proteoglycans and glycosaminoglycans (GAGs), determine events in both embryogenesis and repair of the adult lung. Mesenchymal stromal/stem cells (MSC) have been shown to have immunomodulatory properties and may be potent actors regulating tissue remodelling and regenerative cell responses upon lung injury. Using MSC in cell-based therapy holds promise for treatment of chronic lung diseases such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). However, so far clinical trials with MSCs in COPD have not had a significant impact on disease amelioration nor on IPF, where low cell survival rate and pulmonary retention time are major hurdles to overcome. Research shows that the microenvironment has a profound impact on transplanted MSCs. In our studies on acellular lung tissue slices (lung scaffolds) from IPF patients versus healthy individuals, we see a profound effect on cellular activity, where healthy cells cultured in diseased lung scaffolds adapt and produce proteins further promoting a diseased environment, whereas cells on healthy scaffolds sustain a healthy proteomic profile. Therefore, modulating the environmental context for cell-based therapy may be a potent way to improve treatment using MSCs. In this review, we will describe the importance of the microenvironment for cell-based therapy in chronic lung diseases, how MSC-ECM interactions can affect therapeutic output and describe current progress in the field of cell-based therapy.

Taming of Covid-19: potential and emerging application of mesenchymal stem cells

Coronavirus Disease 2019 (COVID-19) caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has turned out to cause a pandemic, with a sky scraping mortality. The virus is thought to cause tissue injury by affecting the renin-angiotensin system. Also, the role of the over-activated immune system is noteworthy, leading to severe tissue injury via the cytokine storms. Thus it would be feasible to modulate the immune system response in order to attenuate the disease severity, as well as treating the patients. Today different medicines are being administered to the patients, but regardless of the efficacy of these treatments, adverse effects are pretty probable. Meanwhile, mesenchymal stem cells (MSCs) prove to be an effective candidate for treating the patients suffering from COVID-19 pneumonia, owing to their immunomodulatory and tissue-regenerative potentials. So far, several experiments have been conducted; transplanting MSCs and results are satisfying with no adverse effects being reported. This paper aims to review the recent findings regarding the novel coronavirus and the conducted experiments to treat patients suffering from COVID-19 pneumonia utilizing MSCs.

Old Friends with Unexploited Perspectives: Current Advances in Mesenchymal Stem Cell-Based Therapies in Asthma

Mesenchymal stem cells (MSCs) have a great regenerative and immunomodulatory potential that was successfully tested in numerous pre-clinical and clinical studies of various degenerative, hematological and inflammatory disorders. Over the last few decades, substantial immunoregulatory effects of MSC treatment were widely observed in different experimental models of asthma. Therefore, it is tempting to speculate that stem cell-based treatment could become an attractive means to better suppress asthmatic airway inflammation, especially in subjects resistant to currently available anti-inflammatory therapies. In this review, we discuss mechanisms accounting for potent immunosuppressive properties of MSCs and the rationale for their use in asthma. We describe in detail an intriguing interplay between MSCs and other crucial players in the immune system as well as lung microenvironment. Finally, we reveal the potential of MSCs in maintaining airway epithelial integrity and alleviating lung remodeling.

Pluripotency and immunomodulatory signatures of canine induced pluripotent stem cell-derived mesenchymal stromal cells are similar to harvested mesenchymal stromal cells

With a view towards harnessing the therapeutic potential of canine mesenchymal stromal cells (cMSCs) as modulators of inflammation and the immune response, and to avoid the issues of the variable quality and quantity of harvested cMSCs, we examined the immunomodulatory properties of cMSCs derived from canine induced pluripotent stem cells (ciMSCs), and compared them to cMSCs harvested from adipose tissue (cAT-MSC) and bone marrow (cBM-MSC). A combination of deep sequencing and quantitative RT-PCR of the ciMSC transcriptome confirmed that ciMSCs express more genes in common with cBM-MSCs and cAT-MSCs than with the ciPSCs from which they were derived. Both ciMSCs and harvested cMSCs express a range of pluripotency factors in common with the ciPSCs including NANOG, POU5F1 (OCT-4), SOX-2, KLF-4, LIN-28A, MYC, LIF, LIFR, and TERT. However, ESRRB and PRDM-14, both factors associated with naïve, rather than primed, pluripotency were expressed only in the ciPSCs. CXCR-4, which is essential for the homing of MSCs to sites of inflammation, is also detectable in ciMSCs, cAT- and cBM-MSCs, but not ciPSCs. ciMSCs constitutively express the immunomodulatory factors iNOS, GAL-9, TGF-β1, PTGER-2α and VEGF, and the pro-inflammatory mediators COX-2, IL-1β and IL-8. When stimulated with the canine pro-inflammatory cytokines tumor necrosis factor-α (cTNF-α), interferon-γ (cIFN-γ), or a combination of both, ciMSCs upregulated their expression of IDO, iNOS, GAL-9, HGF, TGF-β1, PTGER-2α, VEGF, COX-2, IL-1β and IL-8. When co-cultured with mitogen-stimulated lymphocytes, ciMSCs downregulated their expression of iNOS, HGF, TGF-β1 and PTGER-2α, while increasing their expression of COX-2, IDO and IL-1β. Taken together, these findings suggest that ciMSCs possess similar immunomodulatory capabilities as harvested cMSCs and support further investigation into their potential use for the management of canine immune-mediated and inflammatory disorders.

Immunomodulatory Properties of Mesenchymal Stromal Cells: An Update

Mesenchymal stromal cells (MSCs) are characterized by an extraordinary capacity to modulate the phenotype and functional properties of various immune cells that play an essential role in the pathogenesis of inflammatory disorders. Thus, MSCs efficiently impair the phagocytic and antigen-presenting capacity of monocytes/macrophages and promote the expression of immunosuppressive molecules such as interleukin (IL)-10 and programmed cell death 1 ligand 1 by these cells. They also effectively inhibit the maturation of dendritic cells and their ability to produce proinflammatory cytokines and to stimulate potent T-cell responses. Furthermore, MSCs inhibit the generation and proinflammatory properties of CD4⁺ T helper (Th)1 and Th17 cells, while they promote the proliferation of regulatory T cells and their inhibitory capabilities. MSCs also impair the expansion, cytokine secretion, and cytotoxic activity of proinflammatory CD8⁺ T cells. Moreover, MSCs inhibit the differentiation, proliferation, and antibody secretion of B cells, and foster the generation of IL-10-producing regulatory B cells. Various cell membrane-associated and soluble molecules essentially contribute to these MSC-mediated effects on important cellular components of innate and adaptive immunity. Due to their immunosuppressive properties, MSCs have emerged as promising tools for the treatment of inflammatory disorders such as acute graft-versus-host disease, graft rejection in patients undergoing organ/cell transplantation, and autoimmune diseases.

Dose- and Time-Dependent Effects of Human Mesenchymal Stromal Cell Infusion on Cardiac Allograft Rejection in Mice

Heart transplantation is the final life-saving therapeutic strategy for many end-stage heart diseases. Long-term immunosuppressive regimens are needed to prevent allograft rejection. Mesenchymal stromal cells (MSCs) have been shown as immunomodulatory therapy for organ transplantation. However, the effect of dose and timing of MSC treatment on heart transplantation has not yet been examined. In this study, we infused three doses (1 × 106, 2 × 106, or 5 × 106 cells) of human MSCs (hMSCs) to the recipient BALB/c mice before (7 days or 24 h) or after (24 h) receiving C57BL/6 cardiac transplants. We found that infusion of high dose hMSCs (5 × 106) at 24 h post-transplantation significantly prolonged the survival time of cardiac grafts. To delineate the underlying mechanism, grafts, spleens, and draining lymph nodes were harvested for analysis. Dose-dependent effect of hMSC treatment was shown in: (1) alleviation of International Society of Heart and Lung Transplantation (ISHLT) score in grafts; (2) reduction of the population of CD4+ and CD8+ T cells; (3) increase of regulatory T (Treg) cells; (4) and decrease of serum levels of inflammatory cytokines and donor-specific antibodies. Taken together, we showed timing critical and dose-dependent immunomodulatory effects of hMSC treatment against acute allograft rejection in a mouse model of heart transplantation.

Potential of Extracellular Vesicle-Associated TSG-6 from Adipose Mesenchymal Stromal Cells in Traumatic Brain Injury

Multipotent mesenchymal stromal cells (MSC) represent a promising strategy for a variety of medical applications. Although only a limited number of MSC engraft and survive after in vivo cellular infusion, MSC have shown beneficial effects on immunomodulation and tissue repair. This indicates that the contribution of MSC exists in paracrine signaling, rather than a cell-contact effect of MSC. In this review, we focus on current knowledge about tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6) and mechanisms based on extracellular vesicles (EV) that govern long-lasting immunosuppressive and regenerative activity of MSC. In this context, in particular, we discuss the very robust set of findings by Jha and colleagues, and the opportunity to potentially extend their research focus on EV isolated in concentrated conditioned media (CCM) from adipose tissue derived MSC (ASC). Particularly, the authors showed that ASC-CCM mitigated visual deficits after mild traumatic brain injury in mice. TSG-6 knockdown ASC were, then, used to generate TSG-6-depleted CCM that were not able to replicate the alleviation of abnormalities in injured animals. In light of the presented results, we envision that the infusion of much distilled ASC-CCM could enhance the alleviation of visual abnormalities. In terms of EV research, the advantages of using size-exclusion chromatography are also highlighted because of the enrichment of purer and well-defined EV preparations. Taken together, this could further delineate and boost the benefit of using MSC-based regenerative therapies in the context of forthcoming clinical research testing in diseases that disrupt immune system homeostasis.

Improved outcomes after mesenchymal stem cells injections for knee osteoarthritis: results at 12-months follow-up: a systematic review of the literature

PURPOSE

According to the World Health organization (WHO), more than 10% in people older than 60 years suffer from osteoarthritis (OA). Over the last years, there has been an increased interest around regenerative medicine, especially regarding stem cell treatments and related applications. We hypothesize that stem cell therapies can represent a feasible option for idiopathic knee OA, delaying or even avoiding the joint replacement. To emphasize the potential of percutaneous injections of mesenchymal stem cells for knee OA, a comprehensive systematic review of the literature was conducted.

MATERIAL AND METHODS

Two independent authors (FM, GC) performed the literature search. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA). The main databases were accessed: Pubmed, Embase, Google Scholar, Cochrane Systematic Reviews, Scopus, AMED. For this systematic review, all articles treating percutaneous injections of mesenchymal stem cells for knee OA were considered. Because of the rapid advancements promoted by the scientific progress on stem cell expansion and processing, only articles published within the last five years were included. Solely articles reporting the outcomes of interest across 6- and 12-month follow-up were recruited for eligibility. We included only studies reporting quantitative data under the outcomes of interest. We referred for the quality assessment to the Coleman Methodology Score (CMS). The statistical analysis was performed with Review Manager Software 5.3 (The Nordic Cochrane Centre, Copenhagen).

RESULTS

A total of 18 studies were enrolled in the present study, comprising 1069 treated knees. The mean age of the samples was 57.39 ± 7.37 years. 72% of the included studies harvested the stem cells from the iliac crest (bone marrow-derived MSCs), the remaining 28% from the adipose tissue (adipose-derived MSCs). The mean visual analogic scale improved from 18.37 to 30.98 and 36.91 at 6- and 12-month follow-up, respectively. The mean WOMAC score improved from 25.66 to 25.23 and 15.60 at 6- and 12-month follow-up, respectively. The mean walking distance improved from 71.90 to 152.22 and 316.72 at 6- and 12-month follow-up, respectively. The mean Lequesne scale improved from 33.76 to 12.90 at 12-month follow-up. The KOOS score improved from 41.07 to 8.47% and 18.94 at 6- and 12-month follow-up. All the KOOS subscales improved significantly from the baseline. A total of 136 (12.7%) local complications were detected.

CONCLUSION

According to the current evidences and the main findings of this systematic review, we reported that MSC infiltrations for knee OA can represent a feasible option, leading to an overall remarkable improvement of all clinical and functional considered outcomes, regardless of the cell source. Patients treated at earlier-degeneration stages reported statistically significant greater outcomes. The pain and function scores were improved considerably, thus, leading to a significant improvement of patient participation in recreational activities and quality of life.

Fat Therapeutics: The Clinical Capacity of Adipose-Derived Stem Cells and Exosomes for Human Disease and Tissue Regeneration

Fat grafting is a well-established surgical technique used in plastic surgery to restore deficient tissue, and more recently, for its putative regenerative properties. Despite more frequent use of fat grafting, however, a scientific understanding of the mechanisms underlying either survival or remedial benefits of grafted fat remain lacking. Clinical use of fat grafts for breast reconstruction in tissues damaged by radiotherapy first provided clues regarding the clinical potential of stem cells to drive tissue regeneration. Healthy fat introduced into irradiated tissues appeared to reverse radiation injury (fibrosis, scarring, contracture and pain) clinically; a phenomenon since validated in several animal studies. In the quest to explain and enhance these therapeutic effects, adipose-derived stem cells (ADSCs) were suggested as playing a key role and techniques to enrich ADSCs in fat, in turn, followed. Stem cells - the body's rapid response 'road repair crew' - are on standby to combat tissue insults. ADSCs may exert influences either by releasing paracrine-signalling factors alone or as cell-free extracellular vesicles (EVs, exosomes). Alternatively, ADSCs may augment vital immune/inflammatory processes; or themselves differentiate into mature adipose cells to provide the 'building-blocks' for engineered tissue. Regardless, adipose tissue constitutes an ideal source for mesenchymal stem cells for therapeutic application, due to ease of harvest and processing; and a relative abundance of adipose tissue in most patients. Here, we review the clinical applications of fat grafting, ADSC-enhanced fat graft, fat stem cell therapy; and the latest evolution of EVs and nanoparticles in healing, cancer and neurodegenerative and multiorgan disease.

Intrathecal Infusion of Autologous Adipose-Derived Regenerative Cells in Autoimmune Refractory Epilepsy: Evaluation of Safety and Efficacy

Objective/Purpose. Evaluation of efficacy and safety of autologous adipose-derived regenerative cells (ADRCs) treatment in autoimmune refractory epilepsy. Patients. Six patients with proven or probable autoimmune refractory epilepsy (2 with Rasmussen encephalitis, 2 with antineuronal autoantibodies in serum, and 2 with possible FIRES) were included in the project with approval of the Bioethics Committee.

Immunomodulatory Properties of Mesenchymal Stromal Cells: Still Unresolved "Yin and Yang"

Mesenchymal stromal cells (MSC) are mesodermal elements characterized by the ability to differentiate into several types of cells present mainly in connective tissues. They play a key function in tissue homeostasis and repair. Furthermore, they exert a strong effect on both innate and adaptive immune response. The main current of thought considers MSC as strong inhibitors of the immune system. Indeed, the first description of MSC immunomodulation pointed out their inability to induce alloimmune responses and their veto effects on mixed lymphocyte reactions. This inhibition appears to be mediated both by direct MSC interaction with immune cells and by soluble factors. Unfortunately, evidence to support this notion comes almost exclusively from in vitro experiments. In complex experimental systems, it has been shown that MSC can exert immunosuppressive effects also in vivo, either in murine models or in transplanted patients to avoid the graft versus host disease. However, it is still debated how the small number of administered MSC can regulate efficiently a large number of host effector lymphocytes. In addition, some reports in the literature indicate that MSC can trigger rather than inhibit lymphocyte activation when a very low number of MSC are co-cultured with lymphocytes. This would imply that the ratio between the number of MSC and immune cells is a key point to forecast whether MSC will inhibit or activate the immune system. Herein, we discuss the conflicting results reported on the immunomodulatory effects of MSC to define which features are relevant to understand their behavior and cross-talk with immune cells.

Multiple doses of adipose tissue-derived mesenchymal stromal cells induce immunosuppression in experimental asthma

In experimental house dust mite (HDM)‐induced allergic asthma, therapeutic administration of a single dose of adipose tissue‐derived mesenchymal stromal cells (MSCs) ameliorates lung inflammation but is unable to reverse remodeling. We hypothesized that multiple doses of MSCs might exert better therapeutic effects by reducing lung inflammation and remodeling but might also result in immunosuppressive effects in experimental asthma. HDM was administered intranasally in C57BL/6 mice. After the last HDM challenge, mice received two or three doses of MSCs (10⁵ cells per day) or saline intravenously. An additional cohort of mice received dexamethasone as a positive control for immunosuppression. Two and three doses of MSCs reduced lung inflammation, levels of interleukin (IL)‐4, IL‐13, and eotaxin; total leukocyte, CD4⁺ T‐cell, and eosinophil counts in bronchoalveolar lavage fluid; and total leukocyte counts in bone marrow, spleen, and mediastinal lymph nodes. Two and three doses of MSCs also reduced collagen fiber content and transforming growth factor‐β levels in lung tissue; however, the three‐dose regimen was more effective, and reduced these parameters to control levels, while also decreasing α‐actin content in lung tissue. Two and three doses of MSCs improved lung mechanics. Dexamethasone, two and three doses of MSCs similarly increased galectin levels, but only the three‐dose regimen increased CD39 levels in the thymus. Dexamethasone and the three‐dose, but not the two‐dose regimen, also increased levels of programmed death receptor‐1 and IL‐10, while reducing CD4⁺CD8^low cell percentage in the thymus. In conclusion, multiple doses of MSCs reduced lung inflammation and remodeling while causing immunosuppression in HDM‐induced allergic asthma.

Immune modulation by mesenchymal stem cells

Mesenchymal stem cells (MSCs) can be derived from various adult tissues with multipotent and self‐renewal abilities. The characteristics of presenting no major ethical concerns, having low immunogenicity and possessing immune modulation functions make MSCs promising candidates for stem cell therapies. MSCs could promote inflammation when the immune system is underactivated and restrain inflammation when the immune system is overactivated to avoid self‐overattack. These cells express many immune suppressors to switch them from a pro‐inflammatory phenotype to an anti‐inflammatory phenotype, resulting in immune effector cell suppression and immune suppressor cell activation. We would discuss the mechanisms governing the immune modulation function of these cells in this review, especially the immune‐suppressive effects of MSCs.

The Importance of HLA Assessment in "Off-the-Shelf" Allogeneic Mesenchymal Stem Cells Based-Therapies

The need for more effective therapies of chronic and acute diseases has led to the attempts of developing more adequate and less invasive treatment methods. Regenerative medicine relies mainly on the therapeutic potential of stem cells. Mesenchymal stem cells (MSCs), due to their immunosuppressive properties and tissue repair abilities, seem to be an ideal tool for cell-based therapies. Taking into account all available sources of MSCs, perinatal tissues become an attractive source of allogeneic MSCs. The allogeneic MSCs provide "off-the-shelf" cellular therapy, however, their allogenicity may be viewed as a limitation for their use. Moreover, some evidence suggests that MSCs are not as immune-privileged as it was previously reported. Therefore, understanding their interactions with the recipient's immune system is crucial for their successful clinical application. In this review, we discuss both autologous and allogeneic application of MSCs, focusing on current approaches to allogeneic MSCs therapies, with a particular interest in the role of human leukocyte antigens (HLA) and HLA-matching in allogeneic MSCs transplantation. Importantly, the evidence from the currently completed and ongoing clinical trials demonstrates that allogeneic MSCs transplantation is safe and seems to cause no major side-effects to the patient. These findings strongly support the case for MSCs efficacy in treatment of a variety of diseases and their use as an "off-the-shelf" medical product.

IFN-? stimulated dental follicle mesenchymal stem cells regulate activated lymphocyte response in rheumatoid arthritis patients in vitro

Background/aim

Multipotent mesenchymal stem cells (MSCs) have been investigated in autoimmune diseases such as rheumatoid arthritis (RA) due to their immunomodulatory and regenerative properties. In this study, their immunosuppressive effects on peripheral blood mononuclear cells (PBMC) of RA patients were studied.

Materials and methods

Dental follicle stem cells (DFSCs) were isolated from follicle tissue in the orofacial region. Characterization and multipotency analyses were performed. Lymphocytes were isolated from peripheral venous blood of RA patients (n = 5) and healthy individuals (n = 5). DFSCs were preincubated with IFN-γ for 48 h. PBMCs of RA patients and healthy individuals were separately cultured with or without DFSCs for 72 h. After culture period, lymphocyte proliferation and viability, the frequency of CD4+ CD25+FoxP3+ T regulatory cells, IL-10 and TNF-α levels in the culture supernatants were measured via flow cytometry.

Results

Our results demonstrated that DFSCs suppressed proliferation of T lymphocytes by increasing the number of FoxP3 expressing CD4+CD25+ T regulatory cells and suppressed lymphocyte apoptosis in RA patients. Also, DFSCs reduced TNF-α cytokine secretion and upregulated IL-10 secreting cells.

Conclusions

Such cells could potentially be a source for future immunomodulatory treatments of RA patients.

The Yin and Yang of the Bone Marrow Microenvironment: Pros and Cons of Mesenchymal Stromal Cells in Acute Myeloid Leukemia

Mesenchymal stromal cells (MSCs) have, for a long time, been recognized as pivotal contributors in the set up and maintenance of the hematopoietic stem cell (HSC) niche, as well as in the development and differentiation of the lympho-hematopoietic system. MSCs also have a unique immunomodulatory capacity, which makes them able to affect, both in vitro and in vivo, the function of immune cells. These features, namely the facilitation of stem cell engraftment and the inhibition of lymphocyte responses, have both proven essential for successful allogeneic stem cell transplantation (allo-SCT), which remains the only curative option for several hematologic malignancies. For example, in steroid-refractory acute graft-vs. host disease developing after allo-SCT, MSCs have produced significant results and are now considered a treatment option. However, more recently, the other side of the MSC coin has been unveiled, because of their emerging role in creating a protective and immune-tolerant microenvironment able to support the survival of leukemic cells and affect the response to therapies. In this light, it has been proposed that the failure of current treatments to efficiently override the stroma-mediated protection of leukemic cells accounts for the high rate of relapse in acute myeloid leukemia, at least in part. In this review, we will focus on emerging microenvironment-driven mechanisms conferring a survival advantage to leukemic cells overt physiological HSCs. This body of evidence increasingly highlights the opportunity to consider tumor-microenvironment interactions when designing new therapeutic strategies.

Silk fibroin scaffolds potentiate immunomodulatory function of human mesenchymal stromal cells

Although mesenchymal stromal cells (MSCs) show great potential for use in regenerative medicine, their therapeutic efficacy remains limited because of their low adaptation efficiency and viability observed in clinical trials. To potentiate the adaptation and survival efficiency of MSCs after administration in vivo, silk fibroin nanofibers (SFNs) were applied as a scaffold. SFNs are biocompatible, biodegradable polymers with tunable architectures and mechanical properties. Treatment with interferon (IFN)-γ for 18 h increased the expression of immunomodulatory functional cytokines, IDO and COX2 in MSCs. Further, the MSCs grown on SFN sheets showed enhanced IDO1 and COX2 expression following IFN-γ treatment. MSCs showed significantly greater migratory ability on SFN sheets than on glass surfaces or PLGA control sheets. Though IFN-γ treatment slightly reduced the migration ability of MSCs cultured on glass or poly(lactic-co-glycolic acid) (PLGA) nanofiber sheets, it did not alter MSC motility on SFN sheets. Furthermore, MSCs cultured on SFN sheets dramatically suppressed TNF-α secretion from lipopolysaccharide-activated murine splenocytes, suggesting that the immunomodulatory function of MSCs was enhanced by the SFN sheets. Taken together, these data demonstrate that SFN sheets potentiate the reparative and regenerative properties of MSCs.

IFN-γ stimulation of dental follicle mesenchymal stem cells modulates immune response of CD4+ T lymphocytes in Der p1+ asthmatic patients in vitro

BACKGROUND

House dust mite (Dermataphagoides pteronyssinus) is a widespread risk factor in the development of asthma. CD4⁺ T lymphocytes have an important role in the pathogenesis of allergic asthma by polarizing to Th2 cells.

OBJECTIVE

We aimed to evaluate the immunoregulatory effects of dental follicle mesenchymal stem cells with and without IFN-γ stimulation on peripheral blood mononuclear cells of house dust mite sensitive asthmatic patients, and compared those with Dexamethasone as a systemic steroid.

MATERIAL AND METHODS

PBMC of asthmatic patients and healthy individuals separately cultured with or without DF-MSCs in the presence and absence of IFN-γ or Der p1 or Dexamethasone for 72h. CD4⁺ T proliferation, cell viability, CD4⁺CD25⁺FoxP3⁺ Treg cell frequency and cytokine profiles of PBMC were evaluated via flow cytometry.

RESULTS

DF-MSCs suppressed proliferation of CD4⁺ T lymphocytes (p_CDmix<0.01, p_Derp1<0.01, p_IFN<0.005) by increasing the number of FoxP3 expressing CD4⁺CD25⁺ T regulatory cells (p_CDmix<0.005, p_Derp1<0.01, p_IFN<0.001) and suppressed lymphocyte apoptosis (p_CDmix<0.05, p_Derp1<0.05, p_IFN<0.05), while Dexamethasone increased the apoptosis and decreased Treg cell frequency in asthmatic patients. IFN-γ stimulation increased the suppressive effect of DF-MSCs and also enhanced the frequency of FoxP3 expressing CD4⁺CD25⁺ T regulatory cells. The cytokine levels were regulated by DF-MSCs by reducing IL-4 cytokine levels (p_CDmix<0.01, p_Derp1<0.05, p_IFN<0.05) and upregulating IFN-γ levels (p_CDmix<0.01, p_Derp1<0.05, p_IFN<0.005) in asthmatic patients.

CONCLUSION

IFN-γ stimulated DF-MSCs were found to have a high modulatory effect on CD4⁺ T cell responses, while Dexamethasone had an apoptotic effect on CD4⁺ T cells in asthmatic patients. DF-MSCs may be a new cell-based therapy option for allergic diseases including asthma.

Immunoregulatory mechanisms of mesenchymal stem and stromal cells in inflammatory diseases

Mesenchymal stem cells (MSCs; also referred to as mesenchymal stromal cells) have attracted much attention for their ability to regulate inflammatory processes. Their therapeutic potential is currently being investigated in various degenerative and inflammatory disorders such as Crohn's disease, graft-versus-host disease, diabetic nephropathy and organ fibrosis. The mechanisms by which MSCs exert their therapeutic effects are multifaceted, but in general, these cells are thought to enable damaged tissues to form a balanced inflammatory and regenerative microenvironment in the presence of vigorous inflammation. Studies over the past few years have demonstrated that when exposed to an inflammatory environment, MSCs can orchestrate local and systemic innate and adaptive immune responses through the release of various mediators, including immunosuppressive molecules, growth factors, exosomes, chemokines, complement components and various metabolites. Interestingly, even nonviable MSCs can exert beneficial effects, with apoptotic MSCs showing immunosuppressive functions in vivo. Because the immunomodulatory capabilities of MSCs are not constitutive but rather are licensed by inflammatory cytokines, the net outcomes of MSC activation might vary depending on the levels and the types of inflammation within the residing tissues. Here, we review current understanding of the immunomodulatory mechanisms of MSCs and the issues related to their therapeutic applications.

The Anti-Inflammatory, Anti-Oxidative, and Anti-Apoptotic Benefits of Stem Cells in Acute Ischemic Kidney Injury

Ischemia-reperfusion injury (IRI) plays a significant role in the pathogenesis of acute kidney injury (AKI). The complicated interaction between injured tubular cells, activated endothelial cells, and the immune system leads to oxidative stress and systemic inflammation, thereby exacerbating the apoptosis of renal tubular cells and impeding the process of tissue repair. Stem cell therapy is an innovative approach to ameliorate IRI due to its antioxidative, immunomodulatory, and anti-apoptotic properties. Therefore, it is crucial to understand the biological effects and mechanisms of action of stem cell therapy in the context of acute ischemic AKI to improve its therapeutic benefits. The recent finding that treatment with conditioned medium (CM) derived from stem cells is likely an effective alternative to conventional stem cell transplantation increases the potential for future therapeutic uses of stem cell therapy. In this review, we discuss the recent findings regarding stem cell-mediated cytoprotection, with a focus on the anti-inflammatory effects via suppression of oxidative stress and uncompromised immune responses following AKI. Stem cell-derived CM represents a favorable approach to stem cell-based therapy and may serve as a potential therapeutic strategy against acute ischemic AKI.

Biological functions of mesenchymal stem cells and clinical implications

Mesenchymal stem cells (MSCs) are isolated from multiple biological tissues-adult bone marrow and adipose tissues and neonatal tissues such as umbilical cord and placenta. In vitro, MSCs show biological features of extensive proliferation ability and multipotency. Moreover, MSCs have trophic, homing/migration and immunosuppression functions that have been demonstrated both in vitro and in vivo. A number of clinical trials are using MSCs for therapeutic interventions in severe degenerative and/or inflammatory diseases, including Crohn's disease and graft-versus-host disease, alone or in combination with other drugs. MSCs are promising for therapeutic applications given the ease in obtaining them, their genetic stability, their poor immunogenicity and their curative properties for tissue repair and immunomodulation. The success of MSC therapy in degenerative and/or inflammatory diseases might depend on the robustness of the biological functions of MSCs, which should be linked to their therapeutic potency. Here, we outline the fundamental and advanced concepts of MSC biological features and underline the biological functions of MSCs in their basic and translational aspects in therapy for degenerative and/or inflammatory diseases.

Current understanding of the immunosuppressive properties of mesenchymal stromal cells

Several studies have demonstrated the anti-inflammatory potential of mesenchymal stromal cells (MSCs) isolated from bone marrow, adipose tissue, placenta, and other sources. Nevertheless, MSCs may also induce immunosuppression when administered systemically or directly to injured environments, as shown in different preclinical disease models. MSCs express certain receptors, including toll-like receptors and the aryl-hydrocarbon receptor, that are activated by the surrounding environment, thus leading to modulation of their immunosuppressive activity. Once MSCs are activated, they can affect a wide range of immune cells (e.g., neutrophils, monocytes/macrophages, dendritic cells, natural killer cells, T and B lymphocytes), a phenomenon that has been correlated to secretion of several mediators (e.g., indolamine 2,3-dioxygenase, galectins, prostaglandin E₂, nitric oxide, and damage- and pathogen-associated molecular patterns) and stimulation of certain signaling pathways (e.g., protein kinase R, signal transducer and activator of transcription-1, nuclear factor-κB). Additionally, MSC manipulation and culture conditions, as well as the number of passages, duration of cryopreservation, and O₂ content available, can significantly affect the immunosuppressive properties of MSCs. This review sheds light on current knowledge regarding the mechanisms by which MSCs exert immunosuppressive effects both in vitro and in vivo, focusing on the receptors expressed by MSCs, the correlation between soluble factors secreted by MSCs and their immunosuppressive effects, and interactions between MSCs and immune cells.

Isolation and Characterization of an Adult Stem Cell Population from Human Epidural Fat

Study Design

Isolation and characterization of human epidural fat (HEF) stem/progenitor cells.

Objective

To identify a progenitor population within HEF and to determine if they meet the minimal criteria of a mesenchymal stem cell (MSC).

Summary of Background Data

The biological function, if any, has yet to be determined for HEF. The presence of MSCs within HEF may indicate a regenerative potential within the HEF.

Methods

HEF was isolated from 10 patients during elective spinal surgery. HEF cells were differentiated along osteo-, adipo-, and chondrogenic lineages, with differentiation analyzed via qPCR and histology. The cell surface receptor profile of HEF cells was examined by flow cytometry. HEF cells were also assayed through the collagen contraction assay. Prx1^CreERT2GFP:R26R^TdTomato MSC lineage-tracking mice were employed to identify EF MSCs in vivo.

Results

HEF cell lines were obtained from all 10 patients in the study. Cells from 2/10 patients demonstrated full MSC potential, while cells from 6/10 patients demonstrated progenitor potential; 2/10 patients presented with cells that retained only adipogenic potential. HEF cells demonstrated MSC surface marker expression. All patient cell lines contracted collagen gels. A Prx1-positive population in mouse epidural fat that appeared to contribute to the dura of the spinal cord was observed in vivo.

Conclusions

MSC and progenitor populations are present within HEF. MSCs were not identified in all patients examined in the current study. Furthermore, all patient lines demonstrated collagen contraction capacity, suggesting either a contaminating activated fibroblast population or HEF MSCs/progenitors also demonstrating a fibroblast-like phenotype. In vivo analysis suggests that these cell populations may contribute to the dura. Overall, these results suggest that cells within epidural fat may play a biological role within the local environment above providing a mechanical buffer.

Mesenchymal stem/stromal cell function in modulating cell death

Mesenchymal stem/stromal cells (MSCs) delivered as cell therapy to individuals with degenerative and/or inflammatory disorders can help improve organ features and resolve inflammation, as demonstrated in preclinical studies and to some extent in clinical studies. MSCs have trophic, homing/migration, and immunosuppression functions, with many benefits in therapeutics. MSC functions are thought to depend on the paracrine action of soluble factors and/or the expression of membrane-bound molecules, mostly belonging to the molecular class of adhesion molecules, chemokines, enzymes, growth factors, and interleukins. Cutting-edge studies underline bioactive exchanges, including that of ions, nucleic acids, proteins, and organelles transferred from MSCs to stressed cells, thereby improving the cells' survival and function. From this aspect, MSC death modulation function appears as a decisive biological function that could carry a significant part of the therapeutic effects of MSCs. Identifying the function and modes of actions of MSCs in modulating cell death may be exploited to enhance consistency and efficiency of cell therapy that is based on MSCs as medical treatment for degenerative and/or inflammatory diseases. Here, we review the essentials of MSC functions in modulating cell death in unfit cells, and its modes of actions based on current advances and outline the clinical implications.

Effects of enzyme and cryoprotectant concentrations on yield of equine adipose-derived multipotent stromal cells

OBJECTIVE To evaluate effects of various concentrations of collagenase and dimethyl sulfoxide (DMSO) on yield of equine adipose-derived multipotent stromal cells (ASCs) before and after cryopreservation. SAMPLE Supragluteal subcutaneous adipose tissue from 7 Thoroughbreds. PROCEDURES Tissues were incubated with digests containing 0.1%, 0.05%, or 0.025% type I collagenase. Part of each resulting stromal vascular fraction was cryopreserved in 80% fetal bovine serum (FBS), 10% DMSO, and 10% Dulbecco modified Eagle medium F-12 and in 95% FBS and 5% DMSO. Half of each fresh and cryopreserved heterogeneous cell population was not immunophenotyped (unsorted) or was immunophenotyped for CD44⁺, CD105⁺, and major histocompatability complex class II (MHCII; CD44⁺-CD105⁺-MHCII⁺ cells and CD44⁺-CD105⁺-MHCII^- cells). Cell proliferation (cell viability assay), plasticity (CFU frequency), and lineage-specific target gene and oncogene expression (reverse transcriptase PCR assays) were determined in passage 1 cells before and after culture in induction media. RESULTS Digestion with 0.1% collagenase yielded the highest number of nucleated cells. Cell surface marker expression and proliferation rate were not affected by collagenase concentration. Cryopreservation reduced cell expansion rate and CD44⁺-CD105⁺-MHCII^- CFUs; it also reduced osteogenic plasticity of unsorted cells. However, effects appeared to be unrelated to DMSO concentrations. There were also variable effects on primordial gene expression among cell isolates. CONCLUSIONS AND CLINICAL RELEVANCE Results supported the use of 0.1% collagenase in an adipose tissue digest and 5% DMSO in cryopreservation medium for isolation and cryopreservation, respectively, of equine ASCs. These results may be used as guidelines for standardization of isolation and cryopreservation procedures for equine ASCs.

Mesenchymal stem cells for inflammatory airway disorders: promises and challenges. Biosci Rep. 2019;39. [PMID: 30610158 PMCID: PMC6356012 DOI: 10.1042/bsr20182160]

The regenerative and immunomodulatory characteristics of mesenchymal stem cells (MSCs) make them attractive in the treatment of many diseases. Although they have shown promising preclinical studies of immunomodulation and paracrine effects in inflammatory airway disorders and other lung diseases, there are still challenges that have to be overcome before MSCs can be safely, effectively, and routinely applied in the clinical setting. A good understanding of the roles and mechanisms of the MSC immunomodulatory effects will benefit the application of MSC-based clinical therapy. In this review, we summarize the promises and challenges of the preclinical and clinical trials of MSC therapies, aiming to better understand the role that MSCs play in attempt to treat inflammatory airway disorders.

Immunomodulatory Functions of Mesenchymal Stem Cells in Tissue Engineering

The inflammatory response to chronic injury affects tissue regeneration and has become an important factor influencing the prognosis of patients. In previous stem cell treatments, it was revealed that stem cells not only have the ability for direct differentiation or regeneration in chronic tissue damage but also have a regulatory effect on the immune microenvironment. Stem cells can regulate the immune microenvironment during tissue repair and provide a good "soil" for tissue regeneration. In the current study, the regulation of immune cells by mesenchymal stem cells (MSCs) in the local tissue microenvironment and the tissue damage repair mechanisms are revealed. The application of the concepts of "seed" and "soil" has opened up new research avenues for regenerative medicine. Tissue engineering (TE) technology has been used in multiple tissues and organs using its biomimetic and cellular cell abilities, and scaffolds are now seen as an important part of building seed cell microenvironments. The effect of tissue engineering techniques on stem cell immune regulation is related to the shape and structure of the scaffold, the preinflammatory microenvironment constructed by the implanted scaffold, and the material selection of the scaffold. In the application of scaffold, stem cell technology has important applications in cartilage, bone, heart, and liver and other research fields. In this review, we separately explore the mechanism of MSCs in different tissue and organs through immunoregulation for tissue regeneration and MSC combined with 3D scaffolds to promote MSC immunoregulation to repair damaged tissues.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

Impact of one versus two doses of mesenchymal stromal cells on lung and cardiovascular repair in experimental emphysema

Background

A single administration of mesenchymal stromal cells (MSCs) has been shown to reduce lung inflammation in experimental elastase-induced emphysema; however, effects were limited in terms of lung-tissue repair and cardiac function improvement. We hypothesized that two doses of MSCs could induce further lung and cardiovascular repair by mitigating inflammation and remodeling in a model of emphysema induced by multiple elastase instillations. We aimed to comparatively investigate the effects of one versus two doses of MSCs, administered 1 week apart, in a murine model of elastase-induced emphysema.

Methods

C57BL/6 mice were randomly divided into control (CTRL) and emphysema (E) groups. Mice in the E group received porcine pancreatic elastase (0.2 IU, 50 μL) intratracheally once weekly for four consecutive weeks; the CTRL animals received sterile saline (50 μL) using the same protocol. Three hours after the last instillation, the E group was further randomized to receive either saline (SAL) or murine MSCs (10⁵ cells) intratracheally, in one or two doses (1 week apart). Fourteen days later, mice were euthanized, and all data analyzed.

Results

Both one and two doses of MSCs improved lung mechanics, reducing keratinocyte-derived chemokine and transforming growth factor-β levels in lung homogenates, total cell and macrophage counts in bronchoalveolar lavage fluid (BALF), and collagen fiber content in airways and blood vessels, as well as increasing vascular endothelial growth factor in lung homogenates and elastic fiber content in lung parenchyma. However, only the two-dose group exhibited reductions in tumor necrosis factor-α in lung tissue, BALF neutrophil and lymphocyte count, thymus weight, and total cellularity, as well as CD8⁺ cell counts and cervical lymph node CD4⁺ and CD8⁺ T cell counts, as well as further increased elastic fiber content in the lung parenchyma and reduced severity of pulmonary arterial hypertension.

Conclusions

Two doses of MSCs enhanced lung repair and improvement in cardiac function, while inducing T cell immunosuppression, mainly of CD8⁺ cells, in elastase-induced emphysema.

Effect of mesenchymal stem cells-derived exosomes on tumor microenvironment: Tumor progression versus tumor suppression

Mesenchymal stem cells (MSCs) are multipotent cells with the potential to differentiate into different cell types. Owing to their immunosuppressive and anti-inflammatory properties, they are widely used in regenerative medicine, but they have a dual effect on cancer progression and exert both growth-stimulatory or -inhibitory effects on different cancer types. It has been proposed that these controversial effects of MSC in tumor microenvironment (TME) are mediated by their polarization to proinflammatory or anti-inflammatory phenotype. In addition, they can polarize the immune system cells that in turn influence tumor progression. One of the mechanisms involved in the TME communications is extracellular vesicles (EVs). MSCs, as one of cell populations in TME, produce a large amount of EVs that can influence tumor development. Similar to MSC, MSC-EVs can exert both anti- or protumorigenic effects. In the current study, we will investigate the current knowledge related to MSC role in cancer progression with a focus on the MSC-EV content in limiting tumor growth, angiogenesis, and metastasis. We suppose MSC-EVs can be used as safe vehicles for delivering antitumor agents to TME.

Suppressive effect mediated by human adipose-derived stem cells on T cells involves the activation of JNK

Adipose-derived stem cells (ADSCs) have an immunomodulatory role in vascularized composite tissue allo-transplantation (VCA). However, the specific effects of ADSCs on lymphocytes remain to be fully elucidated. The present study examined the changes in T cells co-cultured with ADSCs in terms of the proliferation by Cell Counting Kit-8 assay, cell cycle profile and apoptosis by flow cytom-etry, inflammatory cytokine production by polymerase chain reaction and ELISA, in addition to the expression of survival proteins by western blotting. The ADSCs reduced the viability of Jurkat T cells and downregulated the transcription of tumor necrosis factor-α and transforming growth factor-β1. Co-culture with ADSCs also induced apoptosis and increased the levels of phosphorylated c-Jun N-terminal kinase in the T cells. Taken together, these findings confirmed that ADSCs modulate the host immune response by suppressing T cells.

Tissue Engineering in Osteoarthritis: Current Status and Prospect of Mesenchymal Stem Cell Therapy

Osteoarthritis (OA) is the most common form of arthritis. Over the last 20 years, attempts have been made to regenerate articular cartilage to overcome the limitations of conventional treatments. As OA is generally associated with larger and diffuse involvement of articular surfaces and alteration of joint homeostasis, a tissue engineering approach for cartilage regeneration is more difficult than in simple chondral defects. Autologous and allogeneic mesenchymal stem cells (MSCs) have rapidly emerged as investigational products for cartilage regeneration. This review outlines points to consider in MSC-based approaches for OA treatment, including allogeneic MSCs, sources of MSCs, dosages, feasibility of multiple injections, indication according to severity of OA lesion and patient age, and issues regarding implantation versus injection. We introduce possible mechanisms of action of implanted or injected MSCs as well as the immunological aspects of MSC therapy and provide a summary of clinical trials of MSCs in the treatment of OA. Given current knowledge, it is too early to draw conclusions on the ultimate effectiveness of intra-articular application of MSCs in terms of regenerative effects. Further radiological and histological data will be needed, with a larger pool of patients, before this question can be answered.