Interferon-gamma modification of mesenchymal stem cells: implications of autologous and allogeneic mesenchymal stem cell therapy in allotransplantation

CEACAM1-engineered MSCs have a broad spectrum of immunomodulatory functions and therapeutic potential via cell-to-cell interaction

Mesenchymal stem cells (MSCs) have garnered attention for their regenerative and immunomodulatory capabilities in clinical trials for various diseases. However, the effectiveness of MSC-based therapies, especially for conditions like graft-versus-host disease (GvHD), remains uncertain. The cytokine interferon (IFN)-γ has been known to enhance the immunosuppressive properties of MSCs through cell-to-cell interactions and soluble factors. In this study, we observed that IFN-γ-treated MSCs upregulated the expression of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), associated with immune evasion through the inhibition of natural killer (NK) cell cytotoxicity. To co-opt this immunomodulatory function, we generated MSCs overexpressing CEACAM1 and found that CEACAM1-engineered MSCs significantly reduced NK cell activation and cytotoxicity via cell-to-cell interaction, independent of NKG2D ligand regulation. Furthermore, CEACAM1-engineered MSCs effectively inhibited the proliferation and activation of T cells along with the inflammatory responses of monocytes. In a humanized GvHD mouse model, CEACAM1-MSCs, particularly CEACAM1-4S-MSCs, demonstrated therapeutic potential by improving survival and alleviating symptoms. These findings suggest that CEACAM1 expression on MSCs contributes to MSC-mediated regulation of immune responses and that CEACAM1-engineered MSC could have therapeutic potential in conditions involving immune dysregulation.

Tumor necrosis factor-α-treated human adipose-derived stem cells enhance inherent radiation tolerance and alleviate in vivo radiation-induced capsular contracture

INTRODUCTION

Post-mastectomy radiotherapy plays a crucial role in breast cancer treatment but can lead to an inflammatory response causing soft tissue damage, particularly radiation-induced capsular contracture (RICC), impacting breast reconstruction outcomes. Adipose-derived stem cells (ADSCs), known for their regenerative potential via paracrine capacity, exhibit inherent radiotolerance. The influence of tumor necrosis factor-alpha (TNF-α) on ADSCs has been reported to enhance the paracrine effect of ADSCs, promoting wound healing by modulating inflammatory responses.

OBJECTIVE

This study investigates the potential of TNF-α-treated human ADSCs (T-hASCs) on silicone implants to alleviate RICC, hypothesizing to enhance suppressive effects on RICC by modulating inflammatory responses in a radiation-exposed environment.

METHODS

In vitro, T-hASCs were cultured on various surfaces to assess viability after exposure to radiation up to 20 Gy. In vivo, T-hASC and non-TNF-α-treated hASC (C-hASCs)-coated membranes were implanted in mice before radiation exposure, and an evaluation of the RICC mitigation took place 4 and 8 weeks after implantation. In addition, the growth factors released from T-hASCs were assessed.

RESULTS

In vitro, hASCs displayed significant radiotolerance, maintaining consistent viability after exposure to 10 Gy. TNF-α treatment further enhanced radiation tolerance, as evidenced by significantly higher viability than C-hASCs at 20 Gy. In vivo, T-hASC-coated implants effectively suppressed RICC, reducing capsule thickness. T-hASCs exhibited remarkable modulation of the inflammatory response, suppressing M1 macrophage polarization while enhancing M2 polarization. The elevated secretion of vascular endothelial growth factor from T-hASCs is believed to induce macrophage polarization, potentially reducing RICC.

CONCLUSION

This study establishes T-hASCs as a promising strategy for ameliorating the adverse effects experienced by breast reconstruction patients after mastectomy and radiation therapy. The observed radiotolerance, anti-fibrotic effects, and immune modulation suggest the possibility of enhancing patient outcomes and quality of life. Further research and clinical trials are warranted for broader clinical uses.

Peptoid-Cross-Linked Hydrogel Stiffness Modulates Human Mesenchymal Stromal Cell Immunoregulatory Potential in the Presence of Interferon-Gamma

Human mesenchymal stromal cell (hMSC) manufacturing requires the production of large numbers of therapeutically potent cells. Licensing with soluble cytokines improves hMSC therapeutic potency by enhancing secretion of immunoactive factors but typically decreases proliferative ability. Soft hydrogels, however, have shown promise for boosting immunomodulatory potential, which may compensate for decreased proliferation. Here, hydrogels are cross-linked with peptoids of different secondary structures to generate substrates of various bulk stiffnesses but fixed network connectivity. Secretions of interleukin 6, monocyte chemoattractive protein-1, macrophage colony-stimulating factor, and vascular endothelial growth factor are shown to depend on hydrogel stiffness in the presence of interferon gamma (IFN-γ) supplementation, with soft substrates further improving secretion. The immunological function of these secreted cytokines is then investigated via coculture of hMSCs seeded on hydrogels with primary peripheral blood mononuclear cells (PBMCs) in the presence and absence of IFN-γ. Cocultures with hMSCs seeded on softer hydrogels show decreased PBMC proliferation with IFN-γ. To probe possible signaling pathways, immunofluorescent studies probe the nuclear factor kappa B pathway and demonstrate that IFN-γ supplementation and softer hydrogel mechanics lead to higher activation of this pathway. Overall, these studies may allow for production of more efficacious therapeutic hMSCs in the presence of IFN-γ.

Primed IFN-γ-Umbilical Cord Stem Cells Ameliorate Temporomandibular Joint Osteoarthritis

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative disorder affecting the temporomandibular joint (TMJ), marked by persistent inflammation and structural damage to the joint. Only symptomatic treatment is available for managing TMJOA. Human umbilical cord mesenchymal stem cells (hUC-MSCs) show potential for treating TMJOA via their immune-modulating actions in the disease area. In addition, stimulation of inflammatory cytokines such as interferon-gamma in hUC-MSCs improves the therapeutic activity of naïve stem cells. Emerging evidence indicates that macrophages play significant roles in regulating joint inflammation through diverse secreted mediators in the pathogenesis of TMJOA. This study was conducted to evaluate the effects of inflammatory cytokine-stimulated hUC-MSCs in repairing TMJOA-induced cartilage lesions and the role of macrophages in the disease. Our in vitro data showed that stimulated hUC-MSCs induce M2 polarization of macrophages and enhance the expression of anti-inflammatory molecules. These effects were subsequently validated in vivo. In a rat model of TMJOA, stimulated hUC-MSCs ameliorated inflammation and increased M2 macrophages ratio. Our results indicate that hUC-MSCs stimulated by inflammatory cytokines modulate the activation of M2 macrophages, thereby shifting the local osteoarthritis microenvironment toward a prochondrogenic state and facilitating cartilage repair in inflammatory conditions. Stimulating hUC-MSCs with inflammatory cytokines could potentially offer an effective therapeutic approach for TMJOA, with macrophages playing a pivotal role in immune modulation.

Mesenchymal Stem Cells-Involved Strategies for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the joints and bone destruction. Because of systemic administration and poor targeting, traditional anti-rheumatic drugs have unsatisfactory treatment efficacy and strong side effects, including myelosuppression, liver or kidney function damage, and malignant tumors. Consequently, mesenchymal stem cells (MSCs)-involved therapy is proposed for RA therapy as a benefit of their immunosuppressive and tissue-repairing effects. This review summarizes the progress of MSCs-involved RA therapy through suppressing inflammation and promoting tissue regeneration and predicts their potential clinical application.

Osteoporosis: interferon-gamma-mediated bone remodeling in osteoimmunology

As the world population ages, osteoporosis, the most common disease of bone metabolism, affects more than 200 million people worldwide. The etiology is an imbalance in bone remodeling process resulting in more significant bone resorption than bone remodeling. With the advent of the osteoimmunology field, the immune system's role in skeletal pathologies is gradually being discovered. The cytokine interferon-gamma (IFN-γ), a member of the interferon family, is an important factor in the etiology and treatment of osteoporosis because it mediates bone remodeling. This review starts with bone remodeling process and includes the cellular and key signaling pathways of bone remodeling. The effects of IFN-γ on osteoblasts, osteoclasts, and bone mass are discussed separately, while the overall effects of IFN-γ on primary and secondary osteoporosis are summarized. The net effect of IFN-γ on bone appears to be highly dependent on the environment, dose, concentration, and stage of cellular differentiation. This review focuses on the mechanisms of bone remodeling and bone immunology, with a comprehensive discussion of the relationship between IFN-γ and osteoporosis. Finding the paradoxical balance of IFN-γ in bone immunology and exploring the potential of its clinical application provide new ideas for the clinical treatment of osteoporosis and drug development.

Molars to Medicine: A Focused Review on the Pre-Clinical Investigation and Treatment of Secondary Degeneration following Spinal Cord Injury Using Dental Stem Cells

Spinal cord injury (SCI) can result in the permanent loss of mobility, sensation, and autonomic function. Secondary degeneration after SCI both initiates and propagates a hostile microenvironment that is resistant to natural repair mechanisms. Consequently, exogenous stem cells have been investigated as a potential therapy for repairing and recovering damaged cells after SCI and other CNS disorders. This focused review highlights the contributions of mesenchymal (MSCs) and dental stem cells (DSCs) in attenuating various secondary injury sequelae through paracrine and cell-to-cell communication mechanisms following SCI and other types of neurotrauma. These mechanistic events include vascular dysfunction, oxidative stress, excitotoxicity, apoptosis and cell loss, neuroinflammation, and structural deficits. The review of studies that directly compare MSC and DSC capabilities also reveals the superior capabilities of DSC in reducing the effects of secondary injury and promoting a favorable microenvironment conducive to repair and regeneration. This review concludes with a discussion of the current limitations and proposes improvements in the future assessment of stem cell therapy through the reporting of the effects of DSC viability and DSC efficacy in attenuating secondary damage after SCI.

Unveiling the functional heterogeneity of cytokine-primed human umbilical cord mesenchymal stem cells through single-cell RNA sequencing

BACKGROUND

Mesenchymal stem cells (MSCs) hold immense promise for use in immunomodulation and regenerative medicine. However, their inherent heterogeneity makes it difficult to achieve optimal therapeutic outcomes for a specific clinical disease. Primed MSCs containing a certain cytokine can enhance their particular functions, thereby increasing their therapeutic potential for related diseases. Therefore, understanding the characteristic changes and underlying mechanisms of MSCs primed by various cytokines is highly important.

RESULTS

In this study, we aimed to reveal the cellular heterogeneity, functional subpopulations, and molecular mechanisms of MSCs primed with IFN-γ, TNF-α, IL-4, IL-6, IL-15, and IL-17 using single-cell RNA sequencing (scRNA-seq). Our results demonstrated that cytokine priming minimized the heterogeneity of the MSC transcriptome, while the expression of MSC surface markers exhibited only slight changes. Notably, compared to IL-6, IL-15, and IL-17; IFN-γ, TNF-α, and IL-4 priming, which stimulated a significantly greater number of differentially expressed genes (DEGs). Functional analysis, which included Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, indicated that IFN-γ, TNF-α, and IL-4-primed hUC-MSCs are involved in interferon-mediated immune-related processes, leukocyte migration, chemotaxis potential, and extracellular matrix and cell adhesion, respectively. Moreover, an investigation of various biological function scores demonstrated that IFN-γ-primed hUC-MSCs exhibit strong immunomodulatory ability, TNF-α-primed hUC-MSCs exhibit high chemotaxis potential, and IL-4-primed hUC-MSCs express elevated amounts of collagen. Finally, we observed that cytokine priming alters the distribution of functional subpopulations of MSCs, and these subpopulations exhibit various potential biological functions. Taken together, our study revealed the distinct regulatory effects of cytokine priming on MSC heterogeneity, biological function, and functional subpopulations at the single-cell level.

CONCLUSIONS

These findings contribute to a comprehensive understanding of the inflammatory priming of MSCs, paving the way for their precise treatment in clinical applications.

Recombinant Human Bone Morphogenetic Protein-2 Priming of Mesenchymal Stem Cells Ameliorate Acute Lung Injury by Inducing Regulatory T Cells

Mesenchymal stromal/stem cells (MSCs) possess immunoregulatory properties and their regulatory functions represent a potential therapy for acute lung injury (ALI). However, uncertainties remain with respect to defining MSCs-derived immunomodulatory pathways. Therefore, this study aimed to investigate the mechanism underlying the enhanced effect of human recombinant bone morphogenic protein-2 (rhBMP-2) primed ES-MSCs (MSCBMP2) in promoting Tregs in ALI mice. MSC were preconditioned with 100 ng/ml rhBMP-2 for 24 h, and then administrated to mice by intravenous injection after intratracheal injection of 1 mg/kg LPS. Treating MSCs with rhBMP-2 significantly increased cellular proliferation and migration, and cytokines array reveled that cytokines release by MSCBMP2 were associated with migration and growth. MSCBMP2 ameliorated LPS induced lung injury and reduced myeloperoxidase activity and permeability in mice exposed to LPS. Levels of inducible nitric oxide synthase were decreased while levels of total glutathione and superoxide dismutase activity were further increased via inhibition of phosphorylated STAT1 in ALI mice treated with MSCBMP2. MSCBMP2 treatment increased the protein level of IDO1, indicating an increase in Treg cells, and Foxp3+CD25+ Treg of CD4+ cells were further increased in ALI mice treated with MSCBMP2. In co-culture assays with MSCs and RAW264.7 cells, the protein level of IDO1 was further induced in MSCBMP2. Additionally, cytokine release of IL-10 was enhanced while both IL-6 and TNF-α were further inhibited. In conclusion, these findings suggest that MSCBMP2 has therapeutic potential to reduce massive inflammation of respiratory diseases by promoting Treg cells.

Ascorbic acid and IFNγ preconditioning enhance the potency of human mesenchymal stem cells to ameliorate LPS induced cytokine storm

The mesenchymal Stem Cells (MSCs) is one of the leading contender in therapeutic management of cytokine storm implicated in the COVID-19 and other inflammatory conditions. This study was aimed to investigate the effect of Interferon gamma (IFN-γ) and Ascorbic Acid (AA) preconditioning on the secretome of the human Umbilical Cord Derived MSCs (UCMSCs) and their potential to ameliorate the lipopolysaccharide (LPS) induced cytokine storm in the human peripheral blood mononuclear cells (PBMCs). UCMSCs were preconditioned with IFN-γ, AA and secretome (UCMSCs-S, IFNγ-UCMSCs-S and AA-UCSMCs-S) was analysed for the levels of growth factors and cytokines by flow cytometry. The potential of secretome to ameliorate cytokine storm and augment angiogenesis was assessed in the LPS induced PBMCs and yolk sac membrane (YSM) assay respectively. The mRNA transcript and protein levels of IL-6, IL-1β and TNF-α was analysed by RT-PCR and flow cytometry respectively. IFNγ-UCMSCs-S and AA-UCSMCs-S ameliorated the LPS induced cytokine storm as revealed by the decreased mRNA and protein expression of IL-6, IL-1β and TNF-α as compared to the UCMSCs-S. IFNγ-UCMSCs-S and AA-UCSMCs-S augmented angiogenesis in YSM assay. Furthermore, IFNγ and AA preconditioning of UCMSCs exhibited distinct growth factors and cytokine profile in the secretome. Our results unequivocally show that IFNγ and AA preconditioning of MSCs could give better therapeutic outcomes in the cell mediated therapies for COVID-19 and other inflammatory conditions.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Salmonella enhances osteogenic differentiation in adipose-derived mesenchymal stem cells

The potential of mesenchymal stem cells (MSCs) for tissue repair and regeneration has garnered great attention. While MSCs are likely to interact with microbes at sites of tissue damage and inflammation, like in the gastrointestinal system, the consequences of pathogenic association on MSC activities have yet to be elucidated. This study investigated the effects of pathogenic interaction on MSC trilineage differentiation paths and mechanisms using model intracellular pathogen Salmonella enterica ssp enterica serotype Typhimurium. The examination of key markers of differentiation, apoptosis, and immunomodulation demonstrated that Salmonella altered osteogenic and chondrogenic differentiation pathways in human and goat adipose-derived MSCs. Anti-apoptotic and pro-proliferative responses were also significantly upregulated (p < 0.05) in MSCs during Salmonella challenge. These results together indicate that Salmonella, and potentially other pathogenic bacteria, can induce pathways that influence both apoptotic response and functional differentiation trajectories in MSCs, highlighting that microbes have a potentially significant role as influencers of MSC physiology and immune activity.

TIMEAS, a promising method for the stratification of testicular germ cell tumor patients with distinct immune microenvironment, clinical outcome and sensitivity to frontline therapies

PURPOSE

With the heterogeneous genetic background, prognosis prediction and therapeutic targets for testicular germ cell tumors (TGCTs) are still unclear. We defined the tumor immune microenvironment activation status (TIMEAS).

METHODS

We collected a total of 314 TGCT patients from four cohorts, including a 48-case microarray. A nonnegative matrix factorization algorithm was applied to identify the "immune factor", derived the top 150 weighted genes to divide patients into immune and non-immune classes, and further separated the immune class into activated and exhausted subgroups by nearest template prediction. Tumor mutant burden, gene mutation, and copy number alteration were compared with our recently developed package "MOVICS". A random forest algorithm was performed to establish a prediction model with fewer genes. Immunohistochemistry staining was performed to identify TIMEAS in the microarray.

RESULTS

We constructed the TIMEAS in the TCGA-TGCT cohort and further validated it in the GSE3218 and GSE99420 cohorts. The immune class contained the activated status of T-lymphocytes, B-lymphocytes, and macrophages, while Treg cells and the WNT/TGFβ signature were more activated in the immune-suppressed subgroup. Patients in the immune-exhausted subgroup had the worst prognosis, and 22.9% of patients in the immune-activated subgroup had KRAS mutations, which might stimulate the response of the immune system and lead to a favorable prognosis. The immune-exhausted group benefited more from chemotherapy, while the immune-activated subgroup responded well to anti-PD-1/PD-L1 therapy. FSCN1 was validated as the target of the immune-exhausted microenvironment by immunohistochemistry.

CONCLUSION

TIMEAS classification can separate TGCT patients; patients in the immune-activated subgroup could benefit more from anti-PD-L1 immunotherapy, and those in the immune-exhausted subgroup are more suitable for chemotherapy.

Priming Mesenchymal Stem/Stromal Cells with a Combination of a Low Dose of IFN-γ and Bortezomib Results in Potent Suppression of Pathogenic Th17 Immunity Through the IDO1-AHR Axis

Preconditioning of mesenchymal stem/stromal cells (MSCs) with the inflammatory cytokine IFN-γ enhances not only their immunosuppressive activity but also their expression of HLA and proinflammatory genes. We hypothesized that prevention of the upregulation of inflammatory cytokines and HLA molecules in IFN-γ-primed MSCs would render these cells more immunosuppressive and less immunogenic. In this study, we discovered the following findings supporting this hypothesis: (1) activated human T cells induced the expression of IDO1 in MSCs via IFN-γ secretion and those MSCs in turn inhibited T-cell proliferation in an AHR-dependent fashion; (2) there was no difference in the expression of IDO1 and HLA-DR in MSCs after priming with a low dose (25 IU/mL) versus a high dose (100 IU/mL) of IFN-γ; (3) the transient addition of bortezomib, a proteasome inhibitor, to culture MSCs after IFN-γ priming decreased the expression of HLA-DR, inflammatory cytokine genes and Vcam1 while increasing the expression of IDO1 and the production of L-kynurenine; finally, MSCs primed with a combination of a low dose of IFN-γ and bortezomib were more effective in inhibiting Th17-mediated idiopathic pneumonia syndrome (IPS) and chronic colitis than unprimed MSCs. Our results suggest that bortezomib significantly eliminates the unfavorable effects of IFN-γ priming of MSCs (increased expression of MHC molecules and inflammatory cytokines and cell aggregation genes) and simultaneously increases their immunosuppressive activity by upregulating IDO1. Taken together, our newly established MSC priming method may contribute to MSC-based cell therapy for inflammatory diseases.

Preclinical Evaluation of interferon-gamma primed human Wharton's jelly-derived mesenchymal stem cells

The potential of human mesenchymal stem cells (MSCs) for cell therapy has been investigated in numerous immune-mediated conditions; MSCs are considered one of the most promising cellular therapeutics to treat intractable diseases. Recently, approaches to prime MSCs have been investigated, thereby generating cellular products with enhanced potential for a variety of clinical applications. Interferon-gamma (IFN-γ) priming is a current approach used to increase the therapeutic efficacy of MSCs. In this study, we determined the systemic toxicity, tumorigenicity and biodistribution of IFN-γ-primed Wharton's jelly-derived (WJ)-MSCs in male and female BALB/c-nu/nu mice. There were no deaths or pathologic lesions in the mice treated with 5 × 10⁶ cells/kg IFN-γ-primed MSCs in the repeated dose study. In the tumorigenicity study, one of the subcutaneously treated mice showed bronchioloalveolar adenoma in the lung but tested negative for human-specific anti-mitochondrial antibody, suggesting the spontaneous murine origin of the adenoma. A biodistribution study using real-time quantitative polymerase chain reaction demonstrated the systemic IFN-γ-primed MSC clearance by day 28. Based on the toxicity, biodistribution, and tumorigenicity studies, we concluded that IFN-γ-primed MSCs at 5 × 10⁶ cells/kg do not induce tumor formation and adverse changes.

Fat Stem Cells Combined with Complement C3 Inhibits the Progress of Type 2 Diabetes in Rats

This study assessed the effect of fat stem cells combined with complement C3 on Wnt/β-catenin pathway in type 2 diabetic rats. 30 male rats were randomly and equally divided into group of type 2 diabetes (intraperitoneal injection of urea with cephalosporins at a dose of 30 mg/kg and fed with high sugar and fat), type 2 diabetes+adipose stem cells+C3 group (after adipose stem cells+C3 group) and control group. Rats in adipose stem cells+C3 group received administration of stem cells and C3. The model of type 2 diabetic rats was successfully constructed. The blood glucose of type 2 diabetic rats and fat stem cell+C3 group was significantly higher than 11.1 mmol/L. Adipocyte was induced to be differentiated into islet cells depending on insulin secretion and glucose concentration. The combination of complement C3 improved the glucose sensitivity in type 2 diabetic rats. Compared with diabetic group, β-catenin and TCF in fat stem cell+C3 group were significantly decreased (P < 0.05). In conclusion, fat stem cells combined with complement C3 inhibit the disease progression in type 2 diabetic rats possibly by inhibiting the activation of Wnt/β-catenin signaling pathway.

Pulmonary Mesenchymal Stem Cells in Mild Cases of COVID-19 Are Dedicated to Proliferation; In Severe Cases, They Control Inflammation, Make Cell Dispersion, and Tissue Regeneration

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have potent self-renewal capacity and differentiate into multiple cell types. For many reasons, these cells are a promising therapeutic alternative to treat patients with severe COVID-19 and pulmonary post-COVID sequelae. These cells are not only essential for tissue regeneration; they can also alter the pulmonary environment through the paracrine secretion of several mediators. They can control or promote inflammation, induce other stem cells differentiation, restrain the virus load, and much more. In this work, we performed single-cell RNA-seq data analysis of MSCs in bronchoalveolar lavage samples from control individuals and COVID-19 patients with mild and severe clinical conditions. When we compared samples from mild cases with control individuals, most genes transcriptionally upregulated in COVID-19 were involved in cell proliferation. However, a new set of genes with distinct biological functions was upregulated when we compared severely affected with mild COVID-19 patients. In this analysis, the cells upregulated genes related to cell dispersion/migration and induced the γ-activated sequence (GAS) genes, probably triggered by IFNGR1 and IFNGR2. Then, IRF-1 was upregulated, one of the GAS target genes, leading to the interferon-stimulated response (ISR) and the overexpression of many signature target genes. The MSCs also upregulated genes involved in the mesenchymal-epithelial transition, virus control, cell chemotaxis, and used the cytoplasmic RNA danger sensors RIG-1, MDA5, and PKR. In a non-comparative analysis, we observed that MSCs from severe cases do not express many NF-κB upstream receptors, such as Toll-like (TLRs) TLR-3, -7, and -8; tumor necrosis factor (TNFR1 or TNFR2), RANK, CD40, and IL-1R1. Indeed, many NF-κB inhibitors were upregulated, including PPP2CB, OPTN, NFKBIA, and FHL2, suggesting that MSCs do not play a role in the "cytokine storm" observed. Therefore, lung MSCs in COVID-19 sense immune danger and act protectively in concert with the pulmonary environment, confirming their therapeutic potential in cell-based therapy for COVID-19. The transcription of MSCs senescence markers is discussed.

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

BACKGROUND

Systemic sclerosis (SSc) is a severe autoimmune disease for which mesenchymal stromal cells (MSCs)-based therapy was reported to reduce SSc-related symptoms in pre-clinical studies. Recently, extracellular vesicles released by MSCs (MSC-EVs) were shown to mediate most of their therapeutic effect. Here, we aimed at improving their efficacy by increasing the MSC-EV dose or by IFNγ-priming of MSCs.

METHODS

small size (ssEVs) and large size EVs (lsEVs) were recovered from murine MSCs that were pre-activated using 1 or 20 ng/mL of IFNγ. In the HOCl-induced model of SSc, mice were treated with EVs at day 21 and sacrificed at day 42. Lung and skin samples were collected for histological and molecular analyses.

RESULTS

increasing the dose of MSC-EVs did not add benefit to the dose previously reported to be efficient in SSc. By contrast, IFNγ pre-activation improved MSC-EVs-based treatment, essentially in the lungs. Low doses of IFNγ decreased the expression of fibrotic markers, while high doses improved remodeling and anti-inflammatory markers. IFNγ pre-activation upregulated iNos, IL1ra and Il6 in MSCs and ssEVs and the PGE2 protein in lsEVs.

CONCLUSION

IFNγ-pre-activation improved the therapeutic effect of MSC-EVs preferentially in the lungs of SSc mice by modulating anti-inflammatory and anti-fibrotic markers.

Mesenchymal Stem Cells in the Treatment of COVID-19, a Promising Future

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have a potent self-renewal capacity and can differentiate into multiple cell types. They also affect the ambient tissue by the paracrine secretion of numerous factors in vivo, including the induction of other stem cells’ differentiation. In vitro, the culture media supernatant is named secretome and contains soluble molecules and extracellular vesicles that retain potent biological function in tissue regeneration. MSCs are considered safe for human treatment; their use does not involve ethical issues, as embryonic stem cells do not require genetic manipulation as induced pluripotent stem cells, and after intravenous injection, they are mainly found in the lugs. Therefore, these cells are currently being tested in various preclinical and clinical trials for several diseases, including COVID-19. Several affected COVID-19 patients develop induced acute respiratory distress syndrome (ARDS) associated with an uncontrolled inflammatory response. This condition causes extensive damage to the lungs and may leave serious post-COVID-19 sequelae. As the disease may cause systemic alterations, such as thromboembolism and compromised renal and cardiac function, the intravenous injection of MSCs may be a therapeutic alternative against multiple pathological manifestations. In this work, we reviewed the literature about MSCs biology, focusing on their function in pulmonary regeneration and their use in COVID-19 treatment.

IFN-γ and PPARδ influence the efficacy and retention of multipotent adult progenitor cells in graft vs host disease

Cell‐based therapy for the treatment of inflammatory disorders has focused on the application of mesenchymal stromal cells (MSCs) and multipotent adult progenitor cells (MAPCs). Despite the recent positive findings in industry‐sponsored clinical trials of MSCs and MAPCs for graft vs host disease (GvHD), cell therapy is efficacious in some but not all patients, highlighting the need to identify strategies to enhance cell‐based therapeutic efficacy. Here, we demonstrate the capacity for interferon (IFN)‐γ licensing to enhance human MAPC efficacy and retention following early administration in a humanized mouse model of acute GvHD (aGvHD). Activation of the nuclear receptor peroxisome proliferator‐activated receptor delta (PPARδ) negatively influenced the retention and efficacy of human MAPCs as well as IFN‐γ‐licensed MAPCs in the aGvHD model. PPARδ antagonism significantly enhanced the efficacy of human MAPCs when administered early in the humanized aGvHD model. COX‐2 expression in human MAPC was significantly decreased in IFN‐γ licensed MAPCs exposed to a PPARδ agonist. Importantly, MAPC exposure to the PPARδ antagonist in the presence of a COX‐2 inhibitor indomethacin before administration significantly reduced the efficacy of PPARδ antagonized MAPCs in the aGvHD humanized mouse model. This is the first study to demonstrate the importance of PPARδ in human MAPC efficacy in vivo and highlights the importance of understanding the disease microenvironment in which cell‐based therapies are to be administered. In particular, the presence of PPARδ ligands may negatively influence MAPC or MSC therapeutic efficacy.

Mesenchymal stem cells alleviate idiopathic pneumonia syndrome by modulating T cell function through CCR2-CCL2 axis

BACKGROUND

Idiopathic pneumonia syndrome (IPS) is a non-infectious fatal complication characterized by a massive infiltration of leukocytes in lungs and diffuse pulmonary injury after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Conventional immunosuppressive treatments for IPS have poor therapeutic effects. Safe and effective treatments are not yet available and under explorations. Our previous study demonstrated that mesenchymal stem cells (MSCs) can alleviate IPS, but the mechanisms remain unclear.

METHODS

Co-cultured pre-activated T cells and MSCs in vitro to observe the changes in the CCR2-CCL2 axis. By establishing an IPS mouse model and administering MSCs to further verify the results of in vitro experiments.

RESULTS

Co-culture of pre-activated T cells with MSCs in vitro modulated the CCR2-CCL2 axis, resulting in quiescent T cells and polarization toward CCR2⁺CD4⁺ T cell subsets. Blocking CCR2-CCL2 interaction abolished the immunoregulatory effect of MSCs, leading to re-activation of T cells and partial reversion of polarizing toward CCR2⁺CD4⁺ T cells. In IPS mouse model, application of MSCs prolonged the survival and reduced the pathological damage and T cell infiltration into lung tissue. Activation of CCR2-CCL2 axis and production of CCR2⁺CD4⁺ T cells were observed in the lungs treated with MSCs. The prophylactic effect of MSCs on IPS was significantly attenuated by the administration of CCR2 or CCL2 antagonist in MSC-treated mice.

CONCLUSIONS

We demonstrated an important role of CCR2-CCL2 axis in modulating T cell function which is one of the mechanisms of the prophylactic effect of MSCs on IPS.

From Mesenchymal Stromal/Stem Cells to Insulin-Producing Cells: Immunological Considerations

Mesenchymal stem cell (MSC)-based therapy for type 1 diabetes mellitus (T1DM) has been the subject matter of many studies over the past few decades. The wide availability, negligible teratogenic risks and differentiation potential of MSCs promise a therapeutic alternative to traditional exogenous insulin injections or pancreatic transplantation. However, conflicting arguments have been reported regarding the immunological profile of MSCs. While some studies support their immune-privileged, immunomodulatory status and successful use in the treatment of several immune-mediated diseases, others maintain that allogeneic MSCs trigger immune responses, especially following differentiation or in vivo transplantation. In this review, the intricate mechanisms by which MSCs exert their immunomodulatory functions and the influencing variables are critically addressed. Furthermore, proposed avenues to enhance these effects, including cytokine pretreatment, coadministration of mTOR inhibitors, the use of Tregs and gene manipulation, are presented. As an alternative, the selection of high-benefit, low-risk donors based on HLA matching, PD-L₁ expression and the absence of donor-specific antibodies (DSAs) are also discussed. Finally, the necessity for the transplantation of human MSC (hMSC)-derived insulin-producing cells (IPCs) into humanized mice is highlighted since this strategy may provide further insights into future clinical applications.

Recent Trends in Multipotent Human Mesenchymal Stem/Stromal Cells: Learning from History and Advancing Clinical Applications

Early cell biology reports demonstrated the presence of cells with stem-like properties in bone marrow, with both hematopoietic and mesenchymal lineages. Over the years, various investigations have purified and characterized mesenchymal stromal/stem cells (MSCs) from different human tissues as cells with multilineage differentiation potential under the appropriate conditions. Due to their appealing characteristics and versatile potentials, MSCs are leveraged in many applications in medicine such as oncology, bioprinting, and as recent as therapeutics discovery and innovation for COVID-19. To date, studies indicate that MSCs have varied differentiation capabilities into different cell types, and demonstrate immunomodulating and anti-inflammatory properties. Different microenvironments or niche for MSCs and their resulting heterogeneity may influence attendant cellular behavior and differentiation capacity. The potential clinical applications of MSCs and exosomes derived from these cells have led to an avalanche of research reports on their properties and hundreds of clinical trials being undertaken. There is ample reason to think, as discussed in this expert review that the future looks bright and promising for MSC research, with many clinical trials under way to ascertain their clinical utility. This review provides a synthesis of the latest advances and trends in MSC research to allow for broad and critically informed use of MSCs. Early observations of the presence of these cells in the bone marrow and their remarkable differentiation capabilities and immunomodulation are also presented.

Metabolic Reprogramming of GMP Grade Cord Tissue Derived Mesenchymal Stem Cells Enhances Their Suppressive Potential in GVHD

Acute graft-vs.-host (GVHD) disease remains a common complication of allogeneic stem cell transplantation with very poor outcomes once the disease becomes steroid refractory. Mesenchymal stem cells (MSCs) represent a promising therapeutic approach for the treatment of GVHD, but so far this strategy has had equivocal clinical efficacy. Therapies using MSCs require optimization taking advantage of the plasticity of these cells in response to different microenvironments. In this study, we aimed to optimize cord blood tissue derived MSCs (CBti MSCs) by priming them using a regimen of inflammatory cytokines. This approach led to their metabolic reprogramming with enhancement of their glycolytic capacity. Metabolically reprogrammed CBti MSCs displayed a boosted immunosuppressive potential, with superior immunomodulatory and homing properties, even after cryopreservation and thawing. Mechanistically, primed CBti MSCs significantly interfered with glycolytic switching and mTOR signaling in T cells, suppressing T cell proliferation and ensuing polarizing toward T regulatory cells. Based on these data, we generated a Good Manufacturing Process (GMP) Laboratory protocol for the production and cryopreservation of primed CBti MSCs for clinical use. Following thawing, these cryopreserved GMP-compliant primed CBti MSCs significantly improved outcomes in a xenogenic mouse model of GVHD. Our data support the concept that metabolic profiling of MSCs can be used as a surrogate for their suppressive potential in conjunction with conventional functional methods to support their therapeutic use in GVHD or other autoimmune disorders.

Eradication of specific donor-dependent variations of mesenchymal stem cells in immunomodulation to enhance therapeutic values

Mesenchymal stem cells (MSCs) are one of the most widely clinically trialed stem cells, due to their abilities to differentiate into multiple cell lineages, to secrete regenerative/rejuvenative factors, and to modulate immune functions, among others. In this study, we analyzed human umbilical-cord-derived MSCs from 32 donors and revealed donor-dependent variations in two non-correlated properties, (1) cell proliferation, and (2) immune modulatory functions in vitro and in vivo, which might explain inconsistent clinical efficacies of MSCs. Through unbiased transcriptomic analyses, we discovered that IFN-γ and NF-κB signaling were positively associated with immune modulatory function of MSCs. Activation of these two pathways via IFN-γ and TNF-α treatment eradicated donor-dependent variations. Additional transcriptomic analyses revealed that treatment with these two factors, while having abolished donor-dependent variations in immune modulatory function, did not overall make different donor-derived MSCs the same at whole transcriptomic levels, demonstrating that the cells were still different in many other biological perspectives, and may not perform equally for therapeutic purposes other than immune modulation. Pre-selection or pre-treatment to eradicate MSC variations in a disease-treatment-specific manner would therefore be necessary to ensure clinical efficacies. Together this study provided novel insights into the quality control perspective of using different-donor-derived MSCs to treat inflammation-related clinical conditions and/or autoimmune diseases.

Engineering the MSC Secretome: A Hydrogel Focused Approach

The therapeutic benefits of exogenously delivered mesenchymal stromal/stem cells (MSCs) have been largely attributed to their secretory properties. However, clinical translation of MSC-based therapies is hindered due to loss of MSC regenerative properties during large-scale expansion and low survival/retention post-delivery. These limitations might be overcome by designing hydrogel culture platforms to modulate the MSC microenvironment. Hydrogel systems could be engineered to i) promote MSC proliferation and maintain regenerative properties (i.e., stemness and secretion) during ex vivo expansion, ii) improve MSC survival, retention, and engraftment in vivo, and/or iii) direct the MSC secretory profile using tailored biochemical and biophysical cues. Herein, it is reviewed how hydrogel material properties (i.e., matrix modulus, viscoelasticity, dimensionality, cell adhesion, and porosity) influence MSC secretion, mediated through cell-matrix and cell-cell interactions. In addition, it is highlighted how biochemical cues (i.e., small molecules, peptides, and proteins) can improve and direct the MSC secretory profile. Last, the authors' perspective is provided on future work toward the understanding of how microenvironmental cues influence the MSC secretome, and designing the next generation of biomaterials, with optimized biophysical and biochemical cues, to direct the MSC secretory profile for improved clinical translation outcomes.

Mesenchymal Stem Cell Derived Extracellular Vesicles for Repairing the Neurovascular Unit after Ischemic Stroke

Ischemic stroke is a debilitating disease and one of the leading causes of long-term disability. During the early phase after ischemic stroke, the blood-brain barrier (BBB) exhibits increased permeability and disruption, leading to an influx of immune cells and inflammatory molecules that exacerbate the damage to the brain tissue. Mesenchymal stem cells have been investigated as a promising therapy to improve the recovery after ischemic stroke. The therapeutic effects imparted by MSCs are mostly paracrine. Recently, the role of extracellular vesicles released by these MSCs have been studied as possible carriers of information to the brain. This review focuses on the potential of MSC derived EVs to repair the components of the neurovascular unit (NVU) controlling the BBB, in order to promote overall recovery from stroke. Here, we review the techniques for increasing the effectiveness of MSC-based therapeutics, such as improved homing capabilities, bioengineering protein expression, modified culture conditions, and customizing the contents of EVs. Combining multiple techniques targeting NVU repair may provide the basis for improved future stroke treatment paradigms.

Applications and therapeutic mechanisms of action of mesenchymal stem cells in radiation-induced lung injury

Radiation-induced lung injury (RILI) is one of the most common complications associated with radiotherapy, characterized by early-stage radiation pneumonia and subsequent radiation pulmonary fibrosis. However, effective therapeutic strategies for RILI are currently lacking. Recently, an increasing number of studies reported that mesenchymal stem cells (MSCs) can enhance the regeneration of damaged tissue, modulate the inflammatory response, reduce the levels of fibrotic cytokines and reactive oxygen species, and inhibit epithelial-mesenchymal transformation. Interestingly, MSCs can also exert immunosuppressive effects, which highlights a new potential therapeutic activity of MSCs for managing RILI. Here, we reviewed the potential applications and therapeutic mechanisms of action of MSCs in RILI, which will represent a good compendium of information for researchers in this field.

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.

Local administration of allogeneic or autologous bone marrow-derived mesenchymal stromal cells enhances bone formation similarly in distraction osteogenesis

BACKGROUND AIMS

Distraction osteogenesis (DO) is a surgical technique to promote bone regeneration that requires a long time for bone healing. Bone marrow-derived mesenchymal stromal cells (MSCs) have been applied to accelerate bone formation in DO. Allogeneic MSCs are attractive, as they could be ready to use in clinics. Whether allogeneic MSCs would have an effect similar to autologous MSCs with regard to promoting bone formation in DO is still unknown. This study compares the effect of autologous MSCs versus allogeneic MSCs on bone formation in a rat DO model.

METHODS

Rat bone marrow-derived MSCs were isolated, characterized and expanded in vitro. Adult rats were subjected to right tibia transverse osteotomy. On the third day of distraction, each rat received one injection of phosphate-buffered saline (PBS), autologous MSCs or allogeneic MSCs at the distraction site. Tibiae were harvested after 28 days of consolidation for micro-computed tomography examination, mechanical test and histological analysis.

RESULTS

Results showed that treatment with both allogeneic and autologous MSCs promoted bone formation, with significantly higher bone mass, mechanical properties and mineral apposition rate as well as expression of angiogenic and bone formation markers at the regeneration sites compared with the PBS-treated group. No statistical difference in bone formation was found between the allogeneic and autologous MSC treatment groups.

CONCLUSIONS

This study indicates that allogeneic and autologous MSCs have a similar effect on promoting bone consolidation in DO. MSCs from an allogeneic source could be used off-the-shelf with DO to achieve early bone healing.

Neural Regenerative Potential of Stem Cells Derived from the Tooth Apical Papilla

The regenerative effects of stem cells derived from dental tissues have been previously investigated. This study assessed the potential of human tooth stem cells from apical papilla (SCAP) on nerve regeneration. The SCAP collected from nine individuals were characterized and polarized by exposure to interferon-γ (IFN-γ). IFN-γ increased kynurenine and interleukin-6 (IL-6) production by SCAP, without affecting the cell viability. IFN-γ-primed SCAP exhibited a decrease of brain-derived neurotrophic factor (BDNF) mRNA levels, followed by an upregulation of glial cell-derived neurotrophic factor mRNA. Ex vivo, the co-culture of SCAP with neurons isolated from the rat dorsal root ganglion induced neurite outgrowth, accompanied by increased BDNF secretion, irrespective of IFN-γ priming. In vivo, the local application of SCAP reduced the mechanical and thermal hypersensitivity in Wistar rats that had been submitted to sciatic chronic constriction injury. The SCAP also reduced the pain scores, according to the evaluation of the Grimace scale, partially restoring the myelin damage and BDNF immunopositivity secondary to nerve lesion. Altogether, our results provide novel evidence about the regenerative effects of human SCAP, indicating their potential to handle nerve injury-related complications.

Biological properties of bone marrow stem cells and adipose-derived stem cells derived from T2DM rats: a comparative study

Background

Patients with type 2 diabetes mellitus (T2DM), especially those with poor glycemic control, are characterized by low bone mass and destruction of bone microstructure. Nowadays, autologous mesenchymal stem cells (auto-MSCs) have been used to repair defects and promote tissue regeneration due to handy source, low immunogenicity and self-renewing and multi-differentiating potential. However, T2DM changed the biological properties of auto-MSCs, and investigating the most suitable auto-MSCs for T2DM patients becomes a focus in tissue engineering.

Results

In this research, we compared the biological characteristics of adipose-derived stem cells (ASCs) and bone marrow stem cells (BMSCs) derived from T2DM rats. These results demonstrated that ASCs had a higher proliferation rate, colony-formation and cell-sheet forming ability, while BMSCs got better osteogenesis-related staining, expression of osteogenesis-related genes and proteins, and osteogenic capacity in vitro.

Conclusions

As it turned out, ASCs from T2DM had a higher proliferation, while BMSCs had significantly higher osteogenetic ability no matter in vitro and in vivo. Therefore, we should take into account the specific and dominated properties of MSC according to different needs to optimize the protocols and improve clinical outcomes for tissue regeneration of T2DM patients.

Anti-Inflammatory Effects of Magnetically Targeted Mesenchymal Stem Cells on Laser-Induced Skin Injuries in Rats

Introduction

Mesenchymal stem cells (MSCs) are a promising resource for tissue regeneration and repair. However, their clinical application is hindered by technical limitations related to MSC enrichment at the target sites.

Methods

MSCs were labeled with magnetic Fe₃O₄ nanoparticles (NPs). We analyzed the effects of NP on cell proliferation, stem cell characteristics, and cytokine secretion. Furthermore, we induced NP-labeled MSC migration with an external magnetic field toward laser-induced skin wounds in rats and evaluated the associated anti-inflammatory effects.

Results

Fe₃O₄ NP application did not adversely affect MSC characteristics. Moreover, Fe₃O₄ NP-labeled MSCs presented increased anti-inflammatory cytokine and chemokine production compared with unlabeled MSCs. Furthermore, MSCs accumulated at the injury site and magnetic targeting promoted NP-labeled MSC migration toward burn injury sites in vivo. On day 7 following MSC injection, reduced inflammation and promoted angiogenesis were observed in the magnetically targeted MSC group. In addition, anti-inflammatory factors were upregulated, whereas pro-inflammatory factors were downregulated within the magnetically targeted MSC group compared with those in the PBS group.

Conclusion

This study demonstrates that magnetically targeted MSCs contribute to cell migration to the site of skin injury, improve anti-inflammatory effects and enhance angiogenesis compared with MSC injection alone. Therefore, magnetically targeted MSC therapy may be an effective treatment approach for epithelial tissue injuries.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

Allogeneic ADSCs Induce the Production of Alloreactive Memory-CD8 T Cells through HLA-ABC Antigens

We investigated the immunogenicity of allogeneic human adipose-derived mesenchymal stem cells (ADSCs) through the production of alloreactive-CD8 T and -memory CD8 T cells, based on their human leukocyte antigen (HLA) expression. In surface antigen analysis, ADSCs do not express co-stimulatory molecules, but expresses HLA-ABC, which is further increased by exposure to the pro-inflammatory cytokines as well as IFN-γ alone. For immunogenicity analysis, allogeneic ADSCs cultured in xenofree medium (XF-ADSCs) were incubated with the recipient immune cells for allogeneic-antigen stimulation. As a result, XF-ADSCs induced IFN-γ and IL-17A release by alloreactive-CD8 T cells and the production of alloreactive-CD8 T cell through a direct pathway, although they have immunomodulatory activity. In the analysis of alloreactive memory CD8 T cells, XF-ADSCs also significantly induced the production of CFSE-low-CD8 TEM and -CD8 TCM cells. However, HLA-blocking antibodies significantly inhibited the production of CFSE-low memory-CD8 T cells, indicating that HLAs are the main antigens responsible for the development of allogeneic ADSCs' immunogenicity. These results suggested that HLA surface antigens expressed in allogeneic MSCs should be solved in order to address concerns related to the immunogenicity problem.

GVHD-derived plasma as a priming strategy of mesenchymal stem cells

Background

Mesenchymal stem cell (MSC) therapy is an important alternative for GVHD treatment, but a third of patients fail to respond to such therapy. Therefore, strategies to enhance the immunosuppressive potential of MSCs constitute an active area of investigation. Here, we proposed an innovative priming strategy based on the plasma obtained from GVHD patients and tested whether this approach could enhance the immunosuppressive capacity of MSCs.

Methods

We obtained the plasma from healthy as well as acute (aGVHD) and chronic (cGVHD) GVHD donors. Plasma samples were characterized according to the TNF-α, IFN-γ, IL-10, IL-1β, IL-12p40, and IL-15 cytokine levels. The MSCs primed with such plasmas were investigated according to surface markers, morphology, proliferation, mRNA expression, and the capacity to control T cell proliferation and Treg generation.

Results

Interestingly, 57% of aGVHD and 33% of cGVHD plasmas significantly enhanced the immunosuppressive potential of MSCs. The most suppressive MSCs presented altered morphology, and those primed with cGHVD displayed a pronounced overexpression of ICAM-1 on their surface. Furthermore, we observed that the ratio of IFN-γ to IL-10 cytokine levels in the plasma used for MSC priming was significantly correlated with higher suppressive potential and Treg generation induction by primed MSCs, regardless of the clinical status of the donor.

Conclusions

This work constitutes an important proof of concept which demonstrates that it is possible to prime MSCs with biological material and also that the cytokine levels in the plasma may affect the MSC immunosuppressive potential, serving as the basis for the development of new therapeutic approaches for the treatment of immune diseases.

Bone Marrow-Derived Progenitor Cells Mediate Immune Cell Regulation

Human bone marrow (BM) derived mesenchymal stem cells (MSC) have high capacity to propagate ex vivo with superior reparative, immunosuppressive, and anti-inflammatory properties. Here we describe standardized protocols and culture conditions that enable the isolation, expansion and maintenance of a highly purified and homogenous population of human MSC. These third party-derived off-the-shelf MSC from healthy human bone marrow donors can potently inhibit mitogenically or allogeneically activated human T cells in proliferation assays. The standard operating procedures described in this chapter can be applied to researchers aiming to enhance MSC immunosuppressive properties and defining MSC mechanisms of action. Importantly, these assays can be incorporated into clinical protocols where the safety and efficacy of human BM MSC can be verified in diseases that are modulated by T cell responses.

Extracellular Vesicles from Interferon-γ-primed Human Umbilical Cord Mesenchymal Stromal Cells Reduce Escherichia coli-induced Acute Lung Injury in Rats

BACKGROUND

Human umbilical cord mesenchymal stromal cells possess considerable therapeutic promise for acute respiratory distress syndrome. Umbilical cord mesenchymal stromal cells may exert therapeutic effects via extracellular vesicles, while priming umbilical cord mesenchymal stromal cells may further enhance their effect. The authors investigated whether interferon-γ-primed umbilical cord mesenchymal stromal cells would generate mesenchymal stromal cell-derived extracellular vesicles with enhanced effects in Escherichia coli (E. coli) pneumonia.

METHODS

In a university laboratory, anesthetized adult male Sprague-Dawley rats (n = 8 to 18 per group) underwent intrapulmonary E. coli instillation (5 × 10 colony forming units per kilogram), and were randomized to receive (a) primed mesenchymal stromal cell-derived extracellular vesicles, (b) naïve mesenchymal stromal cell-derived extracellular vesicles (both 100 million mesenchymal stromal cell-derived extracellular vesicles per kilogram), or (c) vehicle. Injury severity and bacterial load were assessed at 48 h. In vitro studies assessed the potential for primed and naïve mesenchymal stromal cell-derived extracellular vesicles to enhance macrophage bacterial phagocytosis and killing.

RESULTS

Survival increased with primed (10 of 11 [91%]) and naïve (8 of 8 [100%]) mesenchymal stromal cell-derived extracellular vesicles compared with vehicle (12 of 18 [66.7%], P = 0.038). Primed-but not naïve-mesenchymal stromal cell-derived extracellular vesicles reduced alveolar-arterial oxygen gradient (422 ± 104, 536 ± 58, 523 ± 68 mm Hg, respectively; P = 0.008), reduced alveolar protein leak (0.7 ± 0.3, 1.4 ± 0.4, 1.5 ± 0.7 mg/ml, respectively; P = 0.003), increased lung mononuclear phagocytes (23.2 ± 6.3, 21.7 ± 5, 16.7 ± 5 respectively; P = 0.025), and reduced alveolar tumor necrosis factor alpha concentrations (29 ± 14.5, 35 ± 12.3, 47.2 ± 6.3 pg/ml, respectively; P = 0.026) compared with vehicle. Primed-but not naïve-mesenchymal stromal cell-derived extracellular vesicles enhanced endothelial nitric oxide synthase production in the injured lung (endothelial nitric oxide synthase/β-actin = 0.77 ± 0.34, 0.25 ± 0.29, 0.21 ± 0.33, respectively; P = 0.005). Both primed and naïve mesenchymal stromal cell-derived extracellular vesicles enhanced E. coli phagocytosis and bacterial killing in human acute monocytic leukemia cell line (THP-1) in vitro (36.9 ± 4, 13.3 ± 8, 0.1 ± 0.01%, respectively; P = 0.0004) compared with vehicle.

CONCLUSIONS

Extracellular vesicles from interferon-γ-primed human umbilical cord mesenchymal stromal cells more effectively attenuated E. coli-induced lung injury compared with extracellular vesicles from naïve mesenchymal stromal cells, potentially via enhanced macrophage phagocytosis and killing of E. coli.

Phenotypic, Transcriptional, and Functional Analysis of Liver Mesenchymal Stromal Cells and Their Immunomodulatory Properties

The liver is an immunologically active organ with a tolerogenic microenvironment at a quiescent state. The immunoregulatory properties of the liver appear to be retained after transplantation because liver allografts can reduce alloresponses against other organs that are simultaneously transplanted. Mechanisms of this phenomenon remain unknown. Given the known immunomodulatory properties of mesenchymal stromal cells (MSCs), we hypothesized that liver mesenchymal stromal cells (L-MSCs) are superior immunomodulators and contribute to liver-mediated tolerance. L-MSCs, generated from human liver allograft biopsies, were compared with adipose mesenchymal stromal cells (A-MSCs) and bone marrow mesenchymal stromal cells (BM-MSCs). Trilineage differentiation of L-MSCs was confirmed by immunohistochemistry. Comparative phenotypic analyses were done by flow cytometry and transcriptome analyses by RNA sequencing in unaltered cell cultures. The in vitro functional analyses were performed using alloreactive T cell proliferation assays. The transcriptome analysis showed that the L-MSCs are different than the A-MSCs and BM-MSCs, with significant enrichment of genes and gene sets associated with immunoregulation. Compared with the others, L-MSCs were found to express higher cell surface levels of several select immunomodulatory molecules. L-MSCs (versus A-MSCs/BM-MSCs) inhibited alloreactive T cell proliferation (22.7% versus 56.4%/58.7%, respectively; P < 0.05) and reduced the frequency of interferon ɤ-producing T cells better than other MSCs (52.8% versus 94.4%/155.4%; P < 0.05). The antiproliferative impact of L-MSCs was not dependent on cell-to-cell contact, could be reversed incompletely by blocking programmed death ligand 1, and required a higher concentration of the competitive inhibitor of indoleamine 2,3-dioxygenase for complete reversal. In conclusion, L-MSCs appear to be uniquely well-equipped immunomodulatory cells, and they are more potent than A-MSCs and BM-MSCs in that capacity, which suggests that they may contribute to liver-induced systemic tolerance.

Hypermethylation in Calca Promoter Inhibited ASC Osteogenic Differentiation in Rats with Type 2 Diabetic Mellitus

The abnormal environment of type 2 diabetes mellitus (T2DM) leads to a substantial decrease in osteogenic function of stem cells. However, the gene sequence does not vary before and after disease for the patient. This phenomenon may be related to changes in osteogenesis-related gene expression caused by DNA methylation. In this study, we established T2DM models to extract adipose-derived stem cells (ASCs) for different gene identifications through DNA methylation sequencing. Specific fragments of methylation changes in the target gene (Calca) were identified by IGV analysis. CGRP was applied to compare the effects on ASCs-T2DM morphology via phalloidin staining, proliferation through CCK-8 assay, and osteogenic differentiation with osteogenic staining, qPCR, and repair of calvarial defect. Furthermore, 5-azacytidine (5-az) was used to intervene ASCs-T2DM to verify the relationship between the methylation level of the target fragment and expression of Calca. We found that the DNA methylation level of target fragment of Calca in ASCs-T2DM was higher than that in ASCs-C. CGRP intervention showed that it did not change the morphology of ASCs-T2DM but could improve proliferation within a certain range. Meanwhile, it could significantly enhance the formation of ALP and calcium nodules in ASCs-T2DM, increase the expression of osteogenesis-related genes in vitro, and promote the healing of calvarial defects of T2DM rat in a concentration-dependent manner. 5-az intervention indicated that the reduction of the methylation level in Calca target fragment of ASCs-T2DM indeed escalated the gene expression, which may be related to DNMT1. Taken together, the environment of T2DM could upregulate the methylation level in the promoter region of Calca and then decrease the Calca expression. The coding product of Calca revealed a promoting role for osteogenic differentiation of ASCs-T2DM. This result provides an implication for us to understand the mechanism of the decreased osteogenic ability of ASCs-T2DM and improve its osteogenic capacity.

Transplantation of IFN-γ Primed hUCMSCs Significantly Improved Outcomes of Experimental Autoimmune Encephalomyelitis in a Mouse Model

The aim of this study was to investigate potential therapeutic effects of IFN-γ primed human umbilical cord mesenchymal stem cell (IFN-γ-hUCMSCs) transplantation on experimental autoimmune encephalomyelitis (EAE) in mice. In this study, EAE mouse model was established by MOG35-55 immunization method. Outcomes of the EAE mice in terms of body weight and clinical symptoms were analyzed. Electromyography (EMG) was performed to evaluate nerve conduction. ELISA was applied to quantify inflammatory cytokine levels in serum. Our results showed that IFN-γ could up-regulate protein expression of indoleamine 2, 3-dioxygenease 1 (IDO1), an important molecule released by MSCs to exert their immune suppressive activity (p < 0.01). In this study treatment efficacy for EAE was compared between transplantation of hUCMSCs alone and the IFN-γ-hUCMSCs which were cultured in the presence of IFN-γ for 48 h prior to be harvested for transplantation. Compared with hUCMSCs alone and control (PBS transfusion) group, transplantation of the IFN-γ-hUCMSCs could significantly alleviate the body weight loss and clinical symptoms of EAE mice (p < 0.05). Consistently EMG latency was significantly improved in treatment groups (p < 0.001), and the IFN-γ-hUCMSCs group was even better than the hUCMSCs group (p < 0.05). Moreover, the concentrations of IL-17A and TNF-α in serum of the mice treated by IFN-γ-hUCMSCs were significantly lower than hUCMSCs alone and controls, respectively (p < 0.05). In few of the roles of IL-17A and TNF-α in the pathogenesis of EAE, IFN-γ-hUCMSCs treatment associated-suppression of IL-17A and TNF-α expression may contribute in part to their therapeutic effects on EAE. In sum, our study highlights a great clinical potential of IFN-γ-hUCMSCs for multiple sclerosis (MS) treatment.

Effects of Physical, Chemical, and Biological Stimulus on h-MSC Expansion and Their Functional Characteristics

Human adult mesenchymal stem or stromal cells (h-MSC) therapy has gained considerable attention due to the potential to treat or cure diseases given their immunosuppressive properties and tissue regeneration capabilities. Researchers have explored diverse strategies to promote high h-MSC production without losing functional characteristics or properties. Physical stimulus including stiffness, geometry, and topography, chemical stimulus, like varying the surface chemistry, and biochemical stimuli such as cytokines, hormones, small molecules, and herbal extracts have been studied but have yet to be translated to industrial manufacturing practice. In this review, we describe the role of those stimuli on h-MSC manufacturing, and how these stimuli positively promote h-MSC properties, impacting the cell manufacturing field for cell-based therapies. In addition, we discuss other process considerations such as bioreactor design, good manufacturing practice, and the importance of the cell donor and ethics factors for manufacturing potent h-MSC.

The Immunomodulatory Properties of the Human Amnion-Derived Mesenchymal Stromal/Stem Cells Are Induced by INF-γ Produced by Activated Lymphomonocytes and Are Mediated by Cell-To-Cell Contact and Soluble Factors

Human mesenchymal stromal/stem cells (MSCs), being immunoprivileged and having immunomodulatory ability, represent a promising tool to be applied in the field of regenerative medicine. Based on numerous in vitro evidences, the immunological effects of MSCs on immune cells could depend on different mechanisms as cell-to-cell contact and paracrine signals. Furthermore, recent studies have shown that the immunomodulatory activity of MSCs is initiated by activated immune cells; thus, their interaction represents a potential homeostatic mechanism by which MSCs regulate the immune response. MSCs also release exosomes able to give different effects, in a paracrine manner, by influencing inflammatory processes. In this study, we aimed to establish the potential role of human amnion-derived MSCs (hAMSCs), in immunomodulation. We found that the immunosuppressive properties of hAMSCs are not constitutive, but require "supportive signals" capable of promoting these properties. Indeed, we observed that hAMSCs alone are not able to produce an adequate amount of soluble immunomodulatory factors. Here, we studied, in depth, the strong immunomodulatory licensing signal deriving from the direct interaction between hAMSCs and stimulated peripheral blood mononuclear cells. We found that the immunomodulatory effect of hAMSCs also depends on cell-to-cell contact through the contribution of the PDL-1/PD-1 axis. We then investigated the IFN-γ priming of hAMSCs (γ-hAMSCs), which induce the increase of PDL-1 expression, high production of IDO, and upregulation of different immunomodulatory exosome-derived miRNAs. Our miRNA-target network analysis revealed that nine of the deregulated miRNAs are involved in the regulation of key proteins that control both T cell activation/anergy and monocyte differentiation pathways. Finally, we observed that γ-hAMSCs induce in monocytes both M2-like phenotype and the increase of IL-10 production. The extensive implications of MSCs in modulating different aspects of the immune system make these cells attractive candidates to be employed in therapeutic application in immune-based diseases. For these reasons, we aimed, with this study, to shed light on the potential of hAMSCs, and how they could become a useful tool for treating different inflammatory diseases, including end-stage pathologies or adverse effects in transplanted patients.

Cell-based interferon gene therapy using proliferation-controllable, interferon-releasing mesenchymal stem cells

An important safety concern on cell-based gene therapy is that few methods have been available to control the proliferation and functioning of therapeutic protein-expressing cells after transplantation. We previously reported that the proliferation and functioning of the cells transfected with herpes simplex virus thymidine kinase (HSVtk) gene, a suicide gene, can be controlled by administration of ganciclovir. In this study, we tried to control the amount of murine interferon-γ (IFN-γ) secreted from transplanted murine mesenchymal stem cell line C3H10T1/2 cells to achieve safe cell-based IFN-γ gene therapy for cancer. C3H10T1/2 cells were transfected with HSVtk- and murine IFN-γ-expressing plasmid vectors to obtain C3H10T1/2/HSVtk/IFN-γ cells. C3H10T1/2/HSVtk/IFN-γ cells released IFN-γ and were sensitive to ganciclovir. C3H10T1/2/HSVtk/IFN-γ cells significantly suppressed the proliferation of murine adenocarcinoma cell line colon26 cells both in vitro and in vivo. Moreover, subcutaneous administration of ganciclovir to mice transplanted with NanoLuc luciferase-expressing C3H10T1/2/HSVtk cells for three consecutive days reduced the luminescence signals from the transplanted cells. These results indicate that the cell regulation system using HSVtk gene and ganciclovir can be useful for safe and efficient cell-based IFN-γ gene therapy for cancer.

Application of "Primed" Mesenchymal Stromal Cells in Hematopoietic Stem Cell Transplantation: Current Status and Future Prospects

Regenerative potential of mesenchymal stem/stromal cells (MSCs) has led to their application in various cellular therapies. Since in vivo these cells are present in very low numbers, they need expansion in culture to get clinically relevant numbers; however, such long-term ex vivo manipulation leads to loss of their regenerative capacity. Although use of naïve MSCs is still the most common approach used in various therapies, several strategies, both genetic and pharmacological, are being tried out to boost the regenerative capacity of in vitro expanded MSCs. Such manipulations are very commonly reported for regeneration of various tissues like bone, cartilage, kidney, pancreas, and others. Likewise, several efforts have been made to investigate priming of MSCs to enhance their immunoregulatory activity, but such efforts have not been made to the same extent for enhancing the efficacy of hematopoietic stem cell transplantation (HSCT). Development of such approaches for HSCT would not only be useful for enhancing the transplantation efficacy of cord blood cells, which are fewer in numbers, and aged HSCs, which could be functionally compromised, but also for genetically modified HSCs, which are likely to be both, fewer in number and functionally compromised. This review specifically deals with application of "primed" MSCs in the scenario of HSCT.

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.

Cell membrane and bioactive factors derived from mesenchymal stromal cells: Cell-free based therapy for inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract associated with multifactorial conditions such as ulcerative colitis and Crohn’s disease. Although the underlying mechanisms of IBD remain unclear, growing evidence has shown that dysregulated immune system reactions in genetically susceptible individuals contribute to mucosal inflammation. However, conventional treatments have been effective in inducing remission of IBD but not in preventing the relapse of them. In this way, mesenchymal stromal cells (MSC) therapy has been recognized as a promising treatment for IBD due to their immunomodulatory properties, ability to differentiate into several tissues, and homing to inflammatory sites. Even so, literature is conflicted regarding the location and persistence of MSC in the body after transplantation. For this reason, recent studies have focused on the paracrine effect of the biofactors secreted by MSC, especially in relation to the immunomodulatory potential of soluble factors (cytokines, chemokines, and growth factors) and extracellular vehicles that are involved in cell communication and in the transfer of cellular material, such as proteins, lipids, and nucleic acids. Moreover, treatment with interferon-γ, tumor necrosis factor-α, and interleukin-1β causes MSC to express immunomodulatory molecules that mediate the suppression via cell-contact dependent mechanisms. Taken together, we present an overview of the role of bioactive factors and cell membrane proteins derived from MSC as a cell-free therapy that can improve IBD treatment.

Umbilical cord as a long-term source of activatable mesenchymal stromal cells for immunomodulation

BACKGROUND

Mesenchymal stromal cells (MSCs) are used in over 800 clinical trials mainly due to their immune inhibitory activity. Umbilical cord (UC), the second leading source of clinically used MSCs, is usually cut in small tissue pieces. Subsequent cultivation leads to a continuous outgrowth of MSC explant monolayers (MSC-EMs) for months. Currently, the first MSC-EM culture takes approximately 2 weeks to grow out, which is then expanded and applied to patients. The initiating tissue pieces are then discarded. However, when UC pieces are transferred to new culture dishes, MSC-EMs continue to grow out. In case the functional integrity of these cells is maintained, later induced cultures could also be expanded and used for cell therapy. This would drastically increase the number of available cells for each patient. To test the functionality of MSC-EMs from early and late induction time points, we compared the first cultures to those initiated after 2 months by investigating their clonality and immunomodulatory capacity.

METHODS

We analyzed the clonal composition of MSC-EM cultures by umbilical cord piece transduction using integrating lentiviral vectors harboring genetic barcodes assessed by high-throughput sequencing. We investigated the transcriptome of these cultures by microarrays. Finally, the secretome was analyzed by multiplexed ELISAs, in vitro assays, and in vivo in mice.

RESULTS

DNA barcode analysis showed polyclonal MSC-EMs even after months of induction cycles. A transcriptome and secretome analyses of early and late MSC cultures showed only minor changes over time. However, upon activation with TNF-α and IFN-γ, cells from both induction time points produced a multitude of immunomodulatory cytokines. Interestingly, the later induced MSC-EMs produced higher amounts of cytokines. To test whether the different cytokine levels were in a therapeutically relevant range, we used conditioned medium (CM) in an in vitro MLR and an in vivo killing assay. CM from late induced MSC-EMs was at least as immune inhibitory as CM from early induced MSC-EMs.

CONCLUSION

Human umbilical cord maintains a microenvironment for the long-term induction of polyclonal and immune inhibitory active MSCs for months. Thus, our results would offer the possibility to drastically increase the number of therapeutically applicable MSCs for a substantial amount of patients.