Mesenchymal stromal cells for improvement of cardiac function following acute myocardial infarction: a matter of timing

Acute myocardial infarction (AMI) is the leading cause of cardiovascular death and remains the most common cause of heart failure. Reopening of the occluded artery, i.e., reperfusion, is the only way to save the myocardium. However, the expected benefits of reducing infarct size are disappointing due to the reperfusion paradox, which also induces specific cell death. These ischemia-reperfusion (I/R) lesions can account for up to 50% of final infarct size, a major determinant for both mortality and the risk of heart failure (morbidity). In this review, we provide a detailed description of the cell death and inflammation mechanisms as features of I/R injury and cardioprotective strategies such as ischemic postconditioning as well as their underlying mechanisms. Due to their biological properties, the use of mesenchymal stromal/stem cells (MSCs) has been considered a potential therapeutic approach in AMI. Despite promising results and evidence of safety in preclinical studies using MSCs, the effects reported in clinical trials are not conclusive and even inconsistent. These discrepancies were attributed to many parameters such as donor age, in vitro culture, and storage time as well as injection time window after AMI, which alter MSC therapeutic properties. In the context of AMI, future directions will be to generate MSCs with enhanced properties to limit cell death in myocardial tissue and thereby reduce infarct size and improve the healing phase to increase postinfarct myocardial performance.

3D Printing of a Vascularized Mini-Liver Based on the Size-Dependent Functional Enhancements of Cell Spheroids for Rescue of Liver Failure

The emerging stem cell-derived hepatocyte-like cells (HLCs) are the alternative cell sources of hepatocytes for treatment of highly lethal acute liver failure (ALF). However, the hostile local environment and the immature cell differentiation may compromise their therapeutic efficacy. To this end, human adipose-derived mesenchymal stromal/stem cells (hASCs) are engineered into different-sized multicellular spheroids and co-cultured with 3D coaxially and hexagonally patterned human umbilical vein endothelial cells (HUVECs) in a liver lobule-like manner to enhance their hepatic differentiation efficiency. It is found that small-sized hASC spheroids, with a diameter of ≈50 µm, show superior pro-angiogenic effects and hepatic differentiation compared to the other counterparts. The size-dependent functional enhancements are mediated by the Wnt signaling pathway. Meanwhile, co-culture of hASCs with HUVECs, at a HUVECs/hASCs seeding density ratio of 2:1, distinctly promotes hepatic differentiation and vascularization both in vitro and in vivo, especially when endothelial cells are patterned into hollow hexagons. After subcutaneous implantation, the mini-liver, consisting of HLC spheroids and 3D-printed interconnected vasculatures, can effectively improve liver regeneration in two ALF animal models through amelioration of local oxidative stress and inflammation, reduction of liver necrosis, as well as increase of cell proliferation, thereby showing great promise for clinical translation.

Entropy Meets Physiology: Should We Translate Aging as Disorder?

Aging is characterized by an alteration of several physiological processes and biological pathways that leads to an increased susceptibility to age-related diseases and death. Normally, multipotential stem/progenitor cells may contribute to tissue homeostasis, and to minimize the age-depending DNA damage. Scientific research has demonstrated that aging induces several complex changes affecting even the mesenchymal stromal/stem cells (MSCs) ability to self-renew, differentiate, and immunomodulate the human tissues, causing further alterations in the local microenvironment. Cellular senescence can thus be considered as an overall response to several damages. Accordingly, aging seems to create the proper conditions to decrease the tissue's metabolic performance, and the cell-to-cell communication, resulting in a progressive tissue destruction; on the other hand, the MSCs functions appear to be severely reduced. This concise review summarizes the main alterations affecting the MSCs during aging, and it also explains the role of inflammation as a key player in age-related syndromes. The hypothesis is to suggest a parallelism between the thermodynamic concept of "entropy" and biological aging, speculating that both can increase within irreversible systems and both lead toward an irreversible disorder; so, the question is: should we translate aging as disorder?

Overexpression of Alpha-1 Antitrypsin Increases the Proliferation of Mesenchymal Stem Cells by Upregulation of Cyclin D1

Alpha-1 antitrypsin-overexpressing mesenchymal stromal/stem cells (AAT-MSCs) showed improved innate properties with a faster proliferation rate when studied for their protective effects in mouse models of diseases. Here, we investigated the potential mechanism(s) by which AAT gene insertion increases MSC proliferation. Human bone marrow-derived primary or immortalized MSCs (iMSCs) or AAT-MSCs (iAAT-MSCs) were used in the study. Cell proliferation was measured by cell counting and cell cycle analysis. Possible pathways involved in the pro-proliferation effect of AAT were investigated by measuring mRNA and protein expression of key cell cycle genes. Interval cell counting showed increased proliferation in AAT-MSCs or iAAT-MSCs compared to their corresponding MSC controls. Cell cycle analysis revealed more cells progressing into the S and G2/M phases in iAAT-MSCs, with a notable increase in the cell cycle protein, Cyclin D1. Moreover, treatment with Cyclin D1 inhibitors showed that the increase in proliferation is due to Cyclin D1 and that the AAT protein is upstream and a positive regulator of Cyclin D1. Furthermore, AAT's effect on Cyclin D1 is independent of the Wnt signaling pathway as there were no differences in the expression of regulatory proteins, including GSK3β and β-Catenin in iMSC and iAAT-MSCs. In summary, our results indicate that AAT gene insertion in an immortalized MSC cell line increases cell proliferation and growth by increasing Cyclin D1 expression and consequently causing cells to progress through the cell cycle at a significantly faster rate.

Mesenchymal Stromal Cell Therapy Alleviates Ovalbumin-Induced Chronic Airway Remodeling by Suppressing M2 Macrophage Polarization

Chronic asthma is characterized by airway hyperresponsiveness, inflammation, and remodeling. Previous studies have shown that mesenchymal stromal/stem cells (MSCs) exert anti-inflammatory effects on asthma via regulation of the immune cells. However, the therapeutic mechanism of MSCs, especially the mechanism of airway remodeling in chronic asthma, remains to be elucidated. Here, we aimed to investigate the therapeutic effect of MSCs on airway remodeling in chronic asthma and explored the mechanisms by analyzing the polarization phenotype of macrophages in the lungs. We established a mouse model of chronic asthma induced by ovalbumin (OVA) and evaluated the effect of MSCs on airway remodeling. The data showed that MSCs treatment before the challenge exerted protective effects on OVA-induced chronic asthma, i.e., decreased the inflammatory cell infiltration, Th2 cytokine levels, subepithelial extracellular matrix deposition, and transforming growth factor β (TGF-β)/Smad signaling. Additionally, we found that MSCs treatment markedly suppressed macrophage M2 polarization in lung tissue. At the same time, MSCs treatment inhibited NF-κB p65 nuclear translocation, ER stress, and oxidative stress in the OVA-induced chronic allergic airway remodeling mice model. In conclusion, these results demonstrated that MSCs treatment prevents OVA-induced chronic airway remodeling by suppressing macrophage M2 polarization, which may be associated with the dual inhibition of ER stress and oxidative stress. This discovery may provide a new theoretical basis for the future clinical application of MSCs.

Mouse islet-derived stellate cells are similar to, but distinct from, mesenchymal stromal cells and influence the beta cell function

AIMS

Evidence is accumulating of the therapeutic benefits of mesenchymal stromal cells (MSCs) in diabetes-related conditions. We have identified a novel population of stromal cells within islets of Langerhans - islet stellate cells (ISCs) - which have a similar morphology to MSCs. In this study we characterize mouse ISCs and compare their morphology and function to MSCs to determine whether ISCs may also have therapeutic potential in diabetes.

METHODS

ISCs isolated from mouse islets were compared to mouse bone marrow MSCs by analysis of cell morphology; expression of cell-surface markers and extracellular matrix (ECM) components; proliferation; apoptosis; paracrine activity; and differentiation into adipocytes, chondrocytes and osteocytes. We also assessed the effects of co-culture with ISCs or MSCs on the insulin secretory capacity of islet beta cells.

RESULTS

Although morphological similar, ISCs were functionally distinct from MSCs. Thus, ISCs were less proliferative and more apoptotic; they had different expression levels of important paracrine factors; and they were less efficient at differentiation down multiple lineages. Co-culture of mouse islets with ISCs enhanced glucose induced insulin secretion more effectively than co-culture with MSCs.

CONCLUSIONS

ISCs are a specific sub-type of islet-derived stromal cells that possess biological behaviors distinct from MSCs. The enhanced beneficial effects of ISCs on islet beta cell function suggests that they may offer a therapeutic target for enhancing beta cell functional survival in diabetes.

EGF, TGF-α and Amphiregulin Differently Regulate Endometrium-Derived Mesenchymal Stromal/Stem Cells

The prototypical receptor tyrosine kinase epidermal growth factor receptor (EGFR) is regulated by a set of its ligands, which determines the specificity of signaling and intracellular fate of the receptor. The EGFR signaling system is well characterized in immortalized cell lines such as HeLa derived from tumor tissues, but much less is known about EGFR function in untransformed multipotent stromal/stem cells (MSCs). We compared the effect of epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and amphiregulin (AREG) on physiological responses in endometrial MSCs (enMSC) and HeLa cells. In addition, using Western blotting and confocal microscopy, we studied the internalization and degradation of EGFR stimulated by the three ligands in these cell lines. We demonstrated that unlike HeLa, EGF and TGF-α, but not AREG, stimulated enMSC proliferation and prevented decidual differentiation in an EGFR-dependent manner. In HeLa cells, EGF targeted EGFR for degradation, while TGF-α stimulated its recycling. Surprisingly, in enMSC, both ligands caused EGFR degradation. In both cell lines, AREG-EGFR internalization was not registered. In HeLa cells, EGFR was degraded within 2 h, restoring its level in 24 h, while in enMSC, degradation took more than 4-8 h, and the low EGFR level persisted for several days. This indicates that EGFR homeostasis in MSCs may differ significantly from that in immortalized cell lines.

3D Culture and Interferon-γ Priming Modulates Characteristics of Mesenchymal Stromal/Stem Cells by Modifying the Expression of Both Intracellular and Exosomal microRNAs

Mesenchymal stromal/stem cells (MSCs) have emerged as a therapeutic tool in regenerative medicine. Recent studies have shown that exosome (EXO)-derived microRNAs (miRNAs) play a crucial role in mediating MSC functions. Additionally, intracellular miRNAs have been found to regulate MSC therapeutic capacities. However, the molecular mechanisms underlying miRNA-mediated MSC effects are not fully understood. We used 3D culture and IFN-γ to prime/enhance the MSC therapeutic effects in terms of functional miRNAs. After priming, our analysis revealed stable variations in intracellular miRNA among the MSC biological replicates. Conversely, a significant variability of miRNA was observed among EXOs released from biological replicates of the priming treatment. For each priming, we observed distinct miRNA expression profiles between the MSCs and their EXOs. Moreover, in both types of priming, gene ontology (GO) analysis of deregulated miRNAs highlighted their involvement in tissue repair/regeneration pathways. In particular, the 3D culture enhanced angiogenic properties in both MSCs and EXOs, while IFN-γ treatment enriched miRNAs associated with immunomodulatory pathways. These findings suggest that 3D culture and IFN-γ treatment are promising strategies for enhancing the therapeutic potential of MSCs by modulating miRNA expression. Additionally, the identified miRNAs may contribute to understanding the molecular mechanisms underlying the miRNA-mediated therapeutic effects of MSCs.

Clinical Prospect of Mesenchymal Stromal/Stem Cell-Derived Extracellular Vesicles in Kidney Disease: Challenges and the Way Forward

Kidney disease is a growing public health problem worldwide, including both acute and chronic forms. Existing therapies for kidney disease target various pathogenic mechanisms; however, these therapies only slow down the progression of the disease rather than offering a cure. One of the potential and emerging approaches for the treatment of kidney disease is mesenchymal stromal/stem cell (MSC) therapy, shown to have beneficial effects in preclinical studies. In addition, extracellular vesicles (EVs) released by MSCs became a potent cell-free therapy option in various preclinical models of kidney disease due to their regenerative, anti-inflammatory, and immunomodulatory properties. However, there are scarce clinical data available regarding the use of MSC-EVs in kidney pathologies. This review article provides an outline of the renoprotective effects of MSC-EVs in different preclinical models of kidney disease. It offers a comprehensive analysis of possible mechanisms of action of MSC-EVs with an emphasis on kidney disease. Finally, on the journey toward the implementation of MSC-EVs into clinical practice, we highlight the need to establish standardized methods for the characterization of an EV-based product and investigate the adequate dosing, safety, and efficacy of MSC-EVs application, as well as the development of suitable potency assays.

Mesenchymal Stromal Cell Exosomes Mediate M2-like Macrophage Polarization through CD73/Ecto-5'-Nucleotidase Activity

Mesenchymal stem/stromal cell (MSC) exosomes have been shown to alleviate immune dysfunction and inflammation in preclinical animal models. This therapeutic effect is attributed, in part, to their ability to promote the polarization of anti-inflammatory M2-like macrophages. One polarization mechanism has been shown to involve the activation of the MyD88-mediated toll-like receptor (TLR) signaling pathway by the presence of extra domain A-fibronectin (EDA-FN) within the MSC exosomes. Here, we uncovered an additional mechanism where MSC exosomes mediate M2-like macrophage polarization through exosomal CD73 activity. Specifically, we observed that polarization of M2-like macrophages by MSC exosomes was abolished in the presence of inhibitors of CD73 activity, adenosine receptors A_2A and A_2B, and AKT/ERK phosphorylation. These findings suggest that MSC exosomes promote M2-like macrophage polarization by catalyzing the production of adenosine, which then binds to adenosine receptors A_2A and A_2B to activate AKT/ERK-dependent signaling pathways. Thus, CD73 represents an additional critical attribute of MSC exosomes in mediating M2-like macrophage polarization. These findings have implications for predicting the immunomodulatory potency of MSC exosome preparations.

Bone Metastasis Initiation Is Coupled with Bone Remodeling through Osteogenic Differentiation of NG2+ Cells

The bone microenvironment is dynamic and undergoes remodeling in normal and pathologic conditions. Whether such remodeling affects disseminated tumor cells (DTC) and bone metastasis remains poorly understood. Here, we demonstrated that pathologic fractures increase metastatic colonization around the injury. NG2+ cells are a common participant in bone metastasis initiation and bone remodeling in both homeostatic and fractured conditions. NG2+ bone mesenchymal stem/stromal cells (BMSC) often colocalize with DTCs in the perivascular niche. Both DTCs and NG2+ BMSCs are recruited to remodeling sites. Ablation of NG2+ lineage impaired bone remodeling and concurrently diminished metastatic colonization. In cocultures, NG2+ BMSCs, especially when undergoing osteodifferentiation, enhanced cancer cell proliferation and migration. Knockout of N-cadherin in NG2+ cells abolished these effects in vitro and phenocopied NG2+ lineage depletion in vivo. These findings uncover dual roles of NG2+ cells in metastasis and remodeling and indicate that osteodifferentiation of BMSCs promotes metastasis initiation via N-cadherin-mediated cell-cell interaction.

SIGNIFICANCE

The bone colonization of cancer cells occurs in an environment that undergoes constant remodeling. Our study provides mechanistic insights into how bone homeostasis and pathologic repair lead to the outgrowth of disseminated cancer cells, thereby opening new directions for further etiologic and epidemiologic studies of tumor recurrences. This article is highlighted in the In This Issue feature, p. 247.

Mesenchymal Stromal/Stem Cell (MSC)-Based Vector Biomaterials for Clinical Tissue Engineering and Inflammation Research: A Narrative Mini Review

Mesenchymal stromal/stem cells (MSCs) have the ability of self-renewal, the potential of multipotent differentiation, and a strong paracrine capacity, which are mainly used in the field of clinical medicine including dentistry and orthopedics. Therefore, tissue engineering research using MSCs as seed cells is a current trending directions. However, the healing effect of direct cell transplantation is unstable, and the paracrine/autocrine effects of MSCs cannot be effectively elicited. Tumorigenicity and heterogeneity are also concerns. The combination of MSCs as seed cells and appropriate vector materials can form a stable cell growth environment, maximize the secretory features of stem cells, and improve the biocompatibility and mechanical properties of vector materials that facilitate the delivery of drugs and various secretory factors. There are numerous studies on tissue engineering and inflammation of various biomaterials, mainly involving bioceramics, alginate, chitosan, hydrogels, cell sheets, nanoparticles, and three-dimensional printing. The combination of bioceramics, hydrogels and cell sheets with stem cells has demonstrated good therapeutic effects in clinical applications. The application of alginate, chitosan, and nanoparticles in animal models has also shown good prospects for clinical applications. Three-dimensional printing technology can circumvent the shortage of biomaterials, greatly improve the properties of vector materials, and facilitate the transplantation of MSCs. The purpose of this narrative review is to briefly discuss the current use of MSC-based carrier biomaterials to provide a useful resource for future tissue engineering and inflammation research using stem cells as seed cells.

Systematic review and meta-analysis of mesenchymal stromal/stem cells as strategical means for the treatment of COVID-19

BACKGROUND

In coronavirus disease 2019 (COVID-19) patients, elevated levels of inflammatory cytokines from over stimulation of immune cells have become a concern due to the potential outburst of cytokine storm that damages the tissues and organs, especially the lungs. This leads to the manifestation of COVID-19 symptoms, such as pneumonia, acute respiratory distress syndrome (ARDS), multiple organ failure, and eventually death. Mesenchymal stromal/stem cells (MSCs) are currently one of hopeful approaches in treating COVID-19 considering its anti-inflammatory and immunomodulatory functions. On that account, the number of clinical trials concerning the use of MSCs for COVID-19 has been increasing. However, the number of systematic reviews and meta-analysis that specifically discuss its potential as treatment for the disease is still lacking. Therefore, this review will assess the safety and efficacy of MSC administration in COVID-19 patients.

OBJECTIVES

To pool evidence on the safety and efficacy of MSCs in treating COVID-19 by observing MSC-related adverse effects as well as evaluating its effects in reducing inflammatory response and improving pulmonary function.

DATA SOURCES AND METHODS

Following literature search across six databases and one trial register, full-text retrieval, and screening against eligibility criteria, only eight studies were included for data extraction. All eight studies evaluated the use of umbilical cord-derived mesenchymal stromal/stem cell (UC-MSC), infused intravenously. Of these eight studies, six studies were included in meta-analysis on the incidence of mortality, adverse events (AEs), and serious adverse events (SAEs), and the levels of C-reactive protein (CRP) and interleukin (IL)-6. Meta-analysis on pulmonary function was not performed due to insufficient data.

RESULTS

MSC-treated group showed significantly lower risk of mortality than the control group (p = 0.03). No statistical significance was observed on the incidence of AEs (p = 0.78) and SAEs (p = 0.44), and the levels of CRP (p = 0.06) and IL-6 (p = 0.09).

CONCLUSION

MSCs were safe for use, with lower risk of mortality and no association with AEs. Regarding efficacy, descriptive analysis showed indications of improvement on the inflammatory reaction, lung clearance, and oxygenation status despite the lack of statistical significance in meta-analysis of CRP and IL-6. Nevertheless, more studies are needed for affirmation.

REGISTRATION

This systematic review and meta-analysis was registered on the PROSPERO database (no. CRD42022307730).

Therapeutic potential of mesenchymal stromal/stem cells in critical-care patients with systemic inflammatory response syndrome

BACKGROUND

Despite notable advances in the support and treatment of patients admitted to the intensive care unit (ICU), the management of those who develop a systemic inflammatory response syndrome (SIRS) still constitutes an unmet medical need.

MAIN BODY

Both the initial injury (trauma, pancreatitis, infections) and the derived uncontrolled response promote a hyperinflammatory status that leads to systemic hypotension, tissue hypoperfusion and multiple organ failure. Mesenchymal stromal/stem cells (MSCs) are emerging as a potential therapy for severe ICU patients due to their potent immunomodulatory, anti-inflammatory, regenerative and systemic homeostasis-regulating properties. MSCs have demonstrated clinical benefits in several inflammatory-based diseases, but their role in SIRS needs to be further explored.

CONCLUSION

In the current review, after briefly overviewing SIRS physiopathology, we explore the potential mechanisms why MSC therapy could aid in the recovery of this condition and the pre-clinical and early clinical evidence generated to date.

Conglomeration of T- and B-Cell Matrix Responses Determines the Potency of Human Bone Marrow Mesenchymal Stromal Cells

Cell manufacturing facilities need to define the potency of mesenchymal stromal cells (MSCs) as cellular therapeutics in advanced clinical trials or marketing approval. Since MSCs' mechanism of action in humans is not well defined, more than a single functional property of MSCs needs to be captured as a surrogate measure of potency utilizing assay matrix technologies. However, the current limitation is the sole investigation of MSC-mediated T-cell suppression as a surrogate measure of potency. We investigated the effect of MSCs on B-cell matrix responses to be incorporated into the assay matrix potency analytical system. Our results demonstrate that MSCs inhibit B-cell differentiation and block pan-antibody secretion upon activation of B cells in the PBMCs. In contrast, MSCs are inferior in blocking B-cell matrix responses when purified B cells are used. Mechanistic analysis has demonstrated that MSC-mediated inhibition of B-cell matrix responses is non-contact dependent and Tryptophan metabolic pathway plays a major role, akin to the mechanism of MSC-mediated T-cell suppression. MSCs also inhibit both T-cell and B-cell responses when both of these lymphoid populations are concurrently activated in the PBMCs. Secretome analysis of MSC and T/B cell-activated PBMC cocultures identified direct and inverse correlative matrix signatures between humoral antibody isotypes and secretory molecules. The current analysis of the combined and concomitant investigation of T-cell and B-cell matrix responses fulfills the potency assay matrix strategy by incorporating MSCs' interaction with more than a single inflammatory immune responder.

Bone Marrow Mesenchymal Stromal/Stem Cell-Derived Extracellular Vesicles Promote Corneal Wound Repair by Regulating Inflammation and Angiogenesis

Severe corneal damage leads to complete vision loss, thereby affecting life quality and impinging heavily on the healthcare system. Current clinical approaches to manage corneal wounds suffer from severe drawbacks, thus requiring the development of alternative strategies. Of late, mesenchymal stromal/stem cell (MSC)-derived extracellular vesicles (EVs) have become a promising tool in the ophthalmic field. In the present study, we topically delivered bone-marrow-derived MSC-EVs (BMSC-EVs), embedded in methylcellulose, in a murine model of alkali-burn-induced corneal damage in order to evaluate their role in corneal repair through histological and molecular analyses, with the support of magnetic resonance imaging. Our data show that BMSC-EVs, used for the first time in this specific formulation on the damaged cornea, modulate cell death, inflammation and angiogenetic programs in the injured tissue, thus leading to a faster recovery of corneal damage. These results were confirmed on cadaveric donor-derived human corneal epithelial cells in vitro. Thus, BMSC-EVs modulate corneal repair dynamics and are promising as a new cell-free approach for intervening on burn wounds, especially in the avascularized region of the eye.

Glucose Enhances Pro-Tumorigenic Functions of Mammary Adipose-Derived Mesenchymal Stromal/Stem Cells on Breast Cancer Cell Lines

Adiposity and diabetes affect breast cancer (BC) progression. We addressed whether glucose may affect the interaction between mammary adipose tissue-derived mesenchymal stromal/stem cells (MAT-MSCs) and BC cells. Two-dimensional co-cultures and spheroids were established in 25 mM or 5.5 mM glucose (High Glucose-HG or Low Glucose-LG) by using MAT-MSCs and MCF7 or MDA-MB231 BC cells. Gene expression was measured by qPCR, while protein levels were measured by cytofluorimetry and ELISA. CD44high/CD24low BC stem-like sub-population was quantified by cytofluorimetry. An in vivo zebrafish model was assessed by injecting spheroid-derived labeled cells. MAT-MSCs co-cultured with BC cells showed an inflammatory/senescent phenotype with increased abundance of IL-6, IL-8, VEGF and p16INK4a, accompanied by altered levels of CDKN2A and LMNB1. BC cells reduced multipotency and increased fibrotic features modulating OCT4, SOX2, NANOG, αSMA and FAP in MAT-MSCs. Of note, these co-culture-mediated changes in MAT-MSCs were partially reverted in LG. Only in HG, MAT-MSCs increased CD44high/CD24low MCF7 sub-population and promoted their ability to form mammospheres. Injection in zebrafish embryos of HG spheroid-derived MCF7 and MAT-MSCs was followed by a significant cellular migration and caudal dissemination. Thus, MAT-MSCs enhance the aggressiveness of BC cells in a HG environment.

Autologous Marrow Mesenchymal Stem Cell Driving Bone Regeneration in a Rabbit Model of Femoral Head Osteonecrosis

Osteonecrosis of the femoral head (ONFH) is a progressive degenerative disease that ultimately requires a total hip replacement. Mesenchymal stromal/stem cells (MSCs), particularly the ones isolated from bone marrow (BM), could be promising tools to restore bone tissue in ONFH. Here, we established a rabbit model to mimic the pathogenic features of human ONFH and to challenge an autologous MSC-based treatment. ON has been originally induced by the synergic combination of surgery and steroid administration. Autologous BM-MSCs were then implanted in the FH, aiming to restore the damaged tissue. Histological analyses confirmed bone formation in the BM-MSC treated rabbit femurs but not in the controls. In addition, the model also allowed investigations on BM-MSCs isolated before (ON-BM-MSCs) and after (ON+BM-MSCs) ON induction to dissect the impact of ON damage on MSC behavior in an affected microenvironment, accounting for those clinical approaches foreseeing MSCs generally isolated from affected patients. BM-MSCs, isolated before and after ON induction, revealed similar growth rates, immunophenotypic profiles, and differentiation abilities regardless of the ON. Our data support the use of ON+BM-MSCs as a promising autologous therapeutic tool to treat ON, paving the way for a more consolidated use into the clinical settings.

The Characteristics and Survival Potential Under Sub-lethal Stress of Mesenchymal Stromal/Stem Cells Isolated from the Human Vascular Wall

Mesenchymal stromal/stem cells (MSCs) have been identified in multiple human tissues, including the vascular wall. High proliferative potential, multilineage, and immunomodulatory properties make vascular MSCs promising candidates for regenerative medicine. Indeed, their location is strategic for controlling vascular and extra-vascular tissue homeostasis. However, the clinical application of MSCs, and in particular vascular MSCs, is still challenging. Current studies are focused on developing strategies to improve MSC therapeutic applications, like priming MSCs with stress conditions (hypoxia, nutrient deprivation) to achieve a higher therapeutic potential. The goal of the present study is to review the main findings regarding the MSCs isolated from the human vascular wall. Further, the main priming strategies tested on MSCs from different sources are reported, together with the experience on vascular MSCs isolated from healthy cryopreserved and pathological arteries. Stress induction can be a priming approach able to improve MSC effectiveness through several mechanisms that are discussed in this review. Nevertheless, these issues have not been completely explored in vascular MSCs and potential side effects need to be investigated.

Chemokine Assay Matrix Defines the Potency of Human Bone Marrow Mesenchymal Stromal Cells

Potency analysis of mesenchymal stromal cells (MSCs) is required for their use in advanced clinical trials. Assay matrix strategy evaluating more than a single property of MSCs is an emerging strategy in potency analysis. Here we developed an assay matrix approach focusing on the secretory chemokine responses of MSCs using multiplex analytical method. MSCs’ innate fitness in secreting matrix of chemokines is correlated with their metabolic fitness in differential degrees. In addition, innately secreting chemokines are correlated among themselves in a unique pattern. MSC’s matrix chemokine responses to exogenous stimulation of IFNγ and/or TNFα are distinct. However, the combination of IFNγ and TNFα is superior than individual stimulations in eliciting robust and broad matrix chemokine responses of MSCs. Correlation matrix analysis has identified that chemokine responses to IFNγ and/or TNFα display unique correlative secretion patterns. MSC and peripheral blood mononuclear cells coculture analysis has identified the correlation matrix responses of chemokines that predicted immune suppression. In addition, MSC-mediated blocking of T-cell proliferation predominantly correlates with chemokines in an inverse manner. Knockdown of chemokines has demonstrated that MSC-sourced inherent chemokines do not actively play a role in T-cell suppression and thus are the bystander predictors of T-cell suppression. The present analysis of MSC’s matrix chemokine responses can be deployed in the advanced potency analysis of MSCs.

Acellular cardiac scaffolds enriched with MSC-derived extracellular vesicles limit ventricular remodelling and exert local and systemic immunomodulation in a myocardial infarction porcine model

Rationale: Extracellular vesicles (EVs) from mesenchymal stromal cell (MSC) are a potential therapy for cardiac healing after myocardial infarction (MI). Nevertheless, neither their efficient administration nor therapeutic mechanisms are fully elucidated. Here, we evaluate the preclinical efficacy of a tissue engineering approach to locally deliver porcine cardiac adipose tissue MSC-EV (cATMSC-EV) in an acute MI pig model. Methods: After MI by permanent ligation of the coronary artery, pigs (n = 24) were randomized to Untreated or treated groups with a decellularised pericardial scaffold filled with peptide hydrogel and cATMSC-EV purified by size exclusion chromatography (EV-Treated group) or buffer (Control group), placed over the post-infarcted myocardium. Results: After 30 days, cardiac MRI showed an improved cardiac function in EV-Treated animals, with significantly higher right ventricle ejection fraction (+20.8% in EV-Treated; p = 0.026), and less ventricle dilatation, indicating less myocardial remodelling. Scar size was reduced, with less fibrosis in the distal myocardium (-42.6% Col I in EV-Treated vs Untreated; p = 0.03), a 2-fold increase in vascular density (EV-Treated; p = 0.019) and less CCL2 transcription in the infarct core. EV-treated animals had less macrophage infiltration in the infarct core (-31.7% of CD163+ cells/field in EV-Treated; p = 0.026), but 5.8 times more expressing anti-inflammatory CD73 (p = 0.015). Systemically, locally delivered cATMSC-EV also triggered a systemic effect, doubling the circulating IL-1ra (p = 0.01), and reducing the PBMC rush 2d post-MI, the TNFα and GM-CSF levels at 30d post-MI, and modulating the CD73+ and CCR2+ monocyte populations, related to immunomodulation and fibrosis modulation. Conclusions: These results highlight the potential of cATMSC-EV in modulating hallmarks of ischemic injury for cardiac repair after MI.

The cultivation conditions affect the aggregation and functionality of β-cell lines alone and in coculture with mesenchymal stromal/stem cells

The manufacturing of viable and functional β-cell spheroids is required for diabetes cell therapy and drug testing. Mesenchymal stromal/stem cells (MSCs) are known to improve β-cell viability and functionality. We therefore investigated the aggregation behavior of three different β-cell lines (rat insulinoma-1 cell line [INS-1], mouse insulinoma-6 cell line [MIN6], and a cell line formed by the electrofusion of primary human pancreatic islets and PANC-1 cells [1.1B4]), two MSC types, and mixtures of β-cells and MSCs under different conditions. We screened several static systems to produce uniform β-cell and MSC spheroids, finding cell-repellent plates the most suitable. The three different β-cell lines differed in their aggregation behavior, spheroid size, and growth in the same static environment. We found no major differences in spheroid formation between primary MSCs and an immortalized MSC line, although both differed with regard to the aggregation behavior of the β-cell lines. All spheroids showed a reduced viability due to mass transfer limitations under static conditions. We therefore investigated three dynamic systems (shaking multi-well plates, spinner flasks, and shaking flasks). In shaking flasks, there were no β-cell-line-dependent differences in aggregation behavior, resulting in uniform and highly viable spheroids. We found that the aggregation behavior of the β-cell lines changed in a static coculture with MSCs. The β-cell/MSC coculture conditions must be refined to avoid a rapid segregation into distinct populations under dynamic conditions.

MDS cells impair osteolineage differentiation of MSCs via extracellular vesicles to suppress normal hematopoiesis

Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoietic stem cells (HSCs), characterized by ineffective hematopoiesis and frequent progression to leukemia. It has long remained unresolved how MDS cells, which are less proliferative, inhibit normal hematopoiesis and eventually dominate the bone marrow space. Despite several studies implicating mesenchymal stromal or stem cells (MSCs), a principal component of the HSC niche, in the inhibition of normal hematopoiesis, the molecular mechanisms underlying this process remain unclear. Here, we demonstrate that both human and mouse MDS cells perturb bone metabolism by suppressing the osteolineage differentiation of MSCs, which impairs the ability of MSCs to support normal HSCs. Enforced MSC differentiation rescues the suppressed normal hematopoiesis in both in vivo and in vitro MDS models. Intriguingly, the suppression effect is reversible and mediated by extracellular vesicles (EVs) derived from MDS cells. These findings shed light on the novel MDS EV-MSC axis in ineffective hematopoiesis.

Potential Therapeutic Effect and Mechanisms of Mesenchymal Stem Cells-Extracellular Vesicles in Renal Fibrosis

Renal fibrosis (RF) is central pathological pathway for kidney diseases, with the main pathological features being the aberrant accumulation of myofibroblasts that produce accumulation of extracellular matrix in the renal interstitium and glomeruli. Acute kidney injury (AKI) and chronic kidney disease (CKD) are associated with RF. Current treatment strategies for RF are ineffective. Mesenchymal stem cells (MSCs) have been found to be able to treat organ fibrosis including RF, but they have some safety problems, such as cell rejection, carcinogenicity, and virus contamination, which limit the application of MSCs. However, current studies have found that MSCs may exert their therapeutic effect by releasing extracellular vesicles (EVs). MSC-EVs can transfer functional proteins and genetic material directly to the recipient cells. As non-cell membrane structures, MSC-EVs have the advantages of low immunogenicity, easy preservation, and artificial modification, but do not have the characteristics of self-replication and ectopic differentiation. Therefore, EVs are safer than MSCs for treatment, but might be less effective than MSCs. Recent studies have also found that MSC-EVs can improve renal function and pathological changes of RF. Thus, this review summarizes the therapeutic effect of MSC-EVs on RF and the mechanisms that have been discovered so far, so as to provide a theoretical basis for the further study of the role of MSC-EVs in treating RF diseases.

Mesenchymal Stromal/Stem Cells and Their Products as a Therapeutic Tool to Advance Lung Transplantation

Lung transplantation (LTx) has become the gold standard treatment for end-stage respiratory failure. Recently, extended lung donor criteria have been applied to decrease the mortality rate of patients on the waiting list. Moreover, ex vivo lung perfusion (EVLP) has been used to improve the number/quality of previously unacceptable lungs. Despite the above-mentioned progress, the morbidity/mortality of LTx remains high compared to other solid organ transplants. Lungs are particularly susceptible to ischemia-reperfusion injury, which can lead to graft dysfunction. Therefore, the success of LTx is related to the quality/function of the graft, and EVLP represents an opportunity to protect/regenerate the lungs before transplantation. Increasing evidence supports the use of mesenchymal stromal/stem cells (MSCs) as a therapeutic strategy to improve EVLP. The therapeutic properties of MSC are partially mediated by secreted factors. Hence, the strategy of lung perfusion with MSCs and/or their products pave the way for a new innovative approach that further increases the potential for the use of EVLP. This article provides an overview of experimental, preclinical and clinical studies supporting the application of MSCs to improve EVLP, the ultimate goal being efficient organ reconditioning in order to expand the donor lung pool and to improve transplant outcomes.

Mesenchymal Stromal/Stem Cells-Derived Exosomes as an Antimicrobial Weapon for Orodental Infections

The oral cavity as the second most various microbial community in the body contains a broad spectrum of microorganisms which are known as the oral microbiome. The oral microbiome includes different types of microbes such as bacteria, fungi, viruses, and protozoa. Numerous factors can affect the equilibrium of the oral microbiome community which can eventually lead to orodental infectious diseases. Periodontitis, dental caries, oral leukoplakia, oral squamous cell carcinoma are some multifactorial infectious diseases in the oral cavity. In defending against infection, the immune system has an essential role. Depending on the speed and specificity of the reaction, immunity is divided into two different types which are named the innate and the adaptive responses but also there is much interaction between them. In these responses, different types of immune cells are present and recent evidence demonstrates that these cell types both within the innate and adaptive immune systems are capable of secreting some extracellular vesicles named exosomes which are involved in the response to infection. Exosomes are 30-150 nm lipid bilayer vesicles that consist of variant molecules, including proteins, lipids, and genetic materials and they have been associated with cell-to-cell communications. However, some kinds of exosomes can be effective on the pathogenicity of various microorganisms and promoting infections, and some other ones have antimicrobial and anti-infective functions in microbial diseases. These discrepancies in performance are due to the origin of the exosome. Exosomes can modulate the innate and specific immune responses of host cells by participating in antigen presentation for activation of immune cells and stimulating the release of inflammatory factors and the expression of immune molecules. Also, mesenchymal stromal/stem cells (MSCs)-derived exosomes participate in immunomodulation by different mechanisms. Ease of expansion and immunotherapeutic capabilities of MSCs, develop their applications in hundreds of clinical trials. Recently, it has been shown that cell-free therapies, like exosome therapies, by having more advantages than previous treatment methods are emerging as a promising strategy for the treatment of several diseases, in particular inflammatory conditions. In orodental infectious disease, exosomes can also play an important role by modulating immunoinflammatory responses. Therefore, MSCs-derived exosomes may have potential therapeutic effects to be a choice for controlling and treatment of orodental infectious diseases.

Tumorigenic Aspects of MSC Senescence-Implication in Cancer Development and Therapy

As an organism ages, many physiological processes change, including the immune system. This process, called immunosenescence, characterized by abnormal activation and imbalance of innate and adaptive immunity, leads to a state of chronic low-grade systemic inflammation, termed inflammaging. Aging and inflammaging are considered to be the root of many diseases of the elderly, as infections, autoimmune and chronic inflammatory diseases, degenerative diseases, and cancer. The role of mesenchymal stromal/stem cells (MSCs) in the inflammaging process and the age-related diseases is not completely established, although numerous features of aging MSCs, including altered immunomodulatory properties, impeded MSC niche supporting functions, and senescent MSC secretory repertoire are consistent with inflammaging development. Although senescence has its physiological function and can represent a mechanism of tumor prevention, in most cases it eventually transforms into a deleterious (para-)inflammatory process that promotes tumor growth. In this review we are going through current literature, trying to explore the role of senescent MSCs in making and/or sustaining a microenvironment permissive to tumor development and to analyze the therapeutic options that could target this process.

Pro-regenerative Dialogue Between Macrophages and Mesenchymal Stem/Stromal Cells in Osteoarthritis

Osteoarthritis (OA), the most common degenerative and inflammatory joint disorder, is multifaceted. Indeed, OA characteristics include cartilage degradation, osteophytes formation, subchondral bone changes, and synovium inflammation. The difficulty in discovering new efficient treatments for OA patients up to now comes from the adoption of monotherapy approaches targeting either joint tissue repair/catabolism or inflammation to address the diverse components of OA. When satisfactory, these approaches only provide short-term beneficial effects, since they only result in the repair and not the full structural and functional reconstitution of the damaged tissues. In the present review, we will briefly discuss the current therapeutic approaches used to repair the damaged OA cartilage. We will highlight the results obtained with cell-based products in clinical trials and demonstrate how the current strategies result in articular cartilage repair showing restricted early-stage clinical improvements. In order to identify novel therapeutic targets and provide to OA patients long-term clinical benefits, herein, we will review the basis of the regenerative process. We will focus on macrophages and their ambivalent roles in OA development and tissue regeneration, and review the therapeutic strategies to target the macrophage response and favor regeneration in OA.

Dichotomic Potency of IFNγ Licensed Allogeneic Mesenchymal Stromal Cells in Animal Models of Acute Radiation Syndrome and Graft Versus Host Disease

Mesenchymal stromal cells (MSCs) are being tested as a cell therapy in clinical trials for dozens of inflammatory disorders, with varying levels of efficacy reported. Suitable and robust preclinical animal models for testing the safety and efficacy of different types of MSC products before use in clinical trials are rare. We here introduce two highly robust animal models of immune pathology: 1) acute radiation syndrome (ARS) and 2) graft versus host disease (GvHD), in conjunction with studying the immunomodulatory effect of well-characterized Interferon gamma (IFNγ) primed bone marrow derived MSCs. The animal model of ARS is based on clinical grade dosimetry precision and bioluminescence imaging. We found that allogeneic MSCs exhibit lower persistence in naïve compared to irradiated animals, and that intraperitoneal infusion of IFNγ prelicensed allogeneic MSCs protected animals from radiation induced lethality by day 30. In direct comparison, we also investigated the effect of IFNγ prelicensed allogeneic MSCs in modulating acute GvHD in an animal model of MHC major mismatched bone marrow transplantation. Infusion of IFNγ prelicensed allogeneic MSCs failed to mitigate acute GvHD. Altogether our results demonstrate that infused IFNγ prelicensed allogeneic MSCs protect against lethality from ARS, but not GvHD, thus providing important insights on the dichotomy of IFNγ prelicensed allogenic MSCs in well characterized and robust animal models of acute tissue injury.

Human umbilical cord tissue-derived mesenchymal stromal cells as adjuvant therapy for myocardial infarction: a review of current evidence focusing on pre-clinical large animal models and early human trials

Although biologically appealing, the concept of tissue regeneration underlying first- and second-generation cell therapies has failed to translate into consistent results in clinical trials. Several types of cells from different origins have been tested in pre-clinical models and in patients with acute myocardial infarction (AMI). Mesenchymal stromal cells (MSCs) have gained attention because of their potential for immune modulation and ability to promote endogenous tissue repair, mainly through their secretome. MSCs can be easily obtained from several human tissues, the umbilical cord being the most abundant source, and further expanded in culture, making them attractive as an allogeneic "of-the-shelf" cell product, suitable for the AMI setting. The available evidence concerning umbilical cord-derived MSCs in AMI is reviewed, focusing on large animal pre-clinical studies and early human trials. Molecular and cellular mechanisms as well as current limitations and possible translational solutions are also discussed.

Mesenchymal stem cells and extracellular vesicles for the treatment of pain: Current status and perspectives

Mesenchymal stem/stromal cells (MSCs) are multipotent progenitor cells of mesodermal origin. Due to their capacity for self-renewal and differentiation into several cell types, MSCs have been extensively studied in experimental biology and regenerative medicine in recent years. Moreover, MSCs release extracellular vesicles (EVs), which might be partly responsible for their regenerative properties. MSCs regulate several processes in target cells via paracrine signalling, such as immunomodulation, anti-apoptotic signalling, tissue remodelling, angiogenesis and anti-fibrotic signalling. The aim of this review is to provide a detailed description of the functional properties of MSCs and EVs and their potential clinical applications, with a special focus on pain treatment. The analgesic, anti-inflammatory and regenerative properties of MSCs and EVs will be discussed for several diseases, such as neuropathic pain, osteoarthritis and spinal cord injury.

Extracellular Vesicles for the Treatment of Radiation Injuries

Normal tissue injury from accidental or therapeutic exposure to high-dose radiation can cause severe acute and delayed toxicities, which result in mortality and chronic morbidity. Exposure to single high-dose radiation leads to a multi-organ failure, known as acute radiation syndrome, which is caused by radiation-induced oxidative stress and DNA damage to tissue stem cells. The radiation exposure results in acute cell loss, cell cycle arrest, senescence, and early damage to bone marrow and intestine with high mortality from sepsis. There is an urgent need for developing medical countermeasures against radiation injury for normal tissue toxicity. In this review, we discuss the potential of applying secretory extracellular vesicles derived from mesenchymal stromal/stem cells, endothelial cells, and macrophages for promoting repair and regeneration of organs after radiation injury.

Cardiac Derived CD51-Positive Mesenchymal Stem Cells Enhance the Cardiac Repair Through SCF-Mediated Angiogenesis in Mice With Myocardial Infarction

Objective: Many tissues contained resident mesenchymal stromal/stem cells (MSCs) that facilitated tissue hemostasis and repair. However, there is no typical marker to identify the resident cardiac MSCs. We aimed to determine if CD51 could be an optimal marker of cardiac MSCs and assess their therapeutic potential for mice with acute myocardial infarction (AMI).

Methods: Cardiac-derived CD51⁺CD31^–CD45^–Ter119^– cells (named CD51⁺cMSCs) were isolated from C57BL/6 mice(7-day-old) by flow cytometry. The CD51⁺cMSCs were characterized by proliferation capacity, multi-differentiation potential, and expression of typical MSC-related markers. Adult C57BL/6 mice (12-week-old) were utilized for an AMI model via permanently ligating the left anterior descending coronary artery. The therapeutic efficacy of CD51⁺cMSCs was estimated by echocardiography and pathological staining. To determine the underlying mechanism, lentiviruses were utilized to knock down gene (stem cell factor [SCF]) expression of CD51⁺cMSCs.

Results: In this study, CD51 was expressed in the entire layers of the cardiac wall in mice, including endocardium, epicardium, and myocardium, and its expression was decreased with age. Importantly, the CD51⁺cMSCs possessed potent self-renewal potential and multi-lineage differentiation capacity in vitro and also expressed typical MSC-related surface proteins. Furthermore, CD51⁺cMSC transplantation significantly improved cardiac function and attenuated cardiac fibrosis through pro-angiogenesis activity after myocardial infarction in mice. Moreover, SCF secreted by CD51⁺cMSCs played an important role in angiogenesis both in vivo and in vitro.

Conclusions: Collectively, CD51 is a novel marker of cardiac resident MSCs, and CD51⁺cMSC therapy enhances cardiac repair at least partly through SCF-mediated angiogenesis.

Characterization of Extracellular Vesicles from Preconditioned Human Adipose-Derived Stromal/Stem Cells

Cell-free therapy using extracellular vesicles (EVs) from adipose-derived mesenchymal stromal/stem cells (ASCs) seems to be a safe and effective therapeutic option to support tissue and organ regeneration. The application of EVs requires particles with a maximum regenerative capability and hypoxic culture conditions as an in vitro preconditioning regimen has been shown to alter the molecular composition of released EVs. Nevertheless, the EV cargo after hypoxic preconditioning has not yet been comprehensively examined. The aim of the present study was the characterization of EVs from hypoxic preconditioned ASCs. We investigated the EV proteome and their effects on renal tubular epithelial cells in vitro. While no effect of hypoxia was observed on the number of released EVs and their protein content, the cargo of the proteins was altered. Proteomic analysis showed 41 increased or decreased proteins, 11 in a statistically significant manner. Furthermore, the uptake of EVs in epithelial cells and a positive effect on oxidative stress in vitro were observed. In conclusion, culture of ASCs under hypoxic conditions was demonstrated to be a promising in vitro preconditioning regimen, which alters the protein cargo and increases the anti-oxidative potential of EVs. These properties may provide new potential therapeutic options for regenerative medicine.

Control of Mesenchymal Stromal Cell Senescence by Tryptophan Metabolites

Cellular senescence contributes to aging and age-related disorders. High glucose (HG) induces mesenchymal stromal/stem cell (MSC) senescence, which hampers cell expansion and impairs MSC function. Intracellular HG triggers metabolic shift from aerobic glycolysis to oxidative phosphorylation, resulting in reactive oxygen species (ROS) overproduction. It causes mitochondrial dysfunction and morphological changes. Tryptophan metabolites such as 5-methoxytryptophan (5-MTP) and melatonin attenuate HG-induced MSC senescence by protecting mitochondrial integrity and function and reducing ROS generation. They upregulate the expression of antioxidant enzymes. Both metabolites inhibit stress-induced MSC senescence by blocking p38 MAPK signaling pathway, NF-κB, and p300 histone acetyltransferase activity. Furthermore, melatonin upregulates SIRT-1, which reduces NF-κB activity by de-acetylation of NF-κB subunits. Melatonin and 5-MTP are a new class of metabolites protecting MSCs against replicative and stress-induced cellular senescence. They provide new strategies to improve the efficiency of MSC-based therapy for diverse human diseases.

Regen med therapeutic opportunities for fighting COVID-19

This perspective from a Regenerative Medicine Manufacturing Society working group highlights regenerative medicine therapeutic opportunities for fighting COVID-19. This article addresses why SARS-CoV-2 is so different from other viruses and how regenerative medicine is poised to deliver new therapeutic opportunities to battle COVID-19. We describe animal models that depict the mechanism of action for COVID-19 and that may help identify new treatments. Additionally, organoid platforms that can recapitulate some of the physiological properties of human organ systems, such as the lungs and the heart, are discussed as potential platforms that may prove useful in rapidly screening new drugs and identifying at-risk patients. This article critically evaluates some of the promising regenerative medicine-based therapies for treating COVID-19 and presents some of the collective technologies and resources that the scientific community currently has available to confront this pandemic.

Mesenchymal stromal cells for sepsis and septic shock: Lessons for treatment of COVID-19

Sepsis is defined as life‐threatening organ dysfunction caused by a deregulated immune host response to infection. The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has highlighted this multifactorial and complex syndrome. The absence of specific treatment neither against SARS‐CoV‐2 nor against acute respiratory distress syndrome (ARDS), the most serious stage of this infection, has emphasized the need to find alternative treatments. Several therapeutics are currently being tested, including mesenchymal stromal cells. These cells, already used in preclinical models of ARDS, sepsis, and septic shock and also in a few clinical trials, appear well‐tolerated and promising, but many questions remain unanswered.

Roles of cell fusion between mesenchymal stromal/stem cells and malignant cells in tumor growth and metastasis

Invasion and metastasis are the basic characteristics and important markers of malignant tumors, which are also the main cause of death in cancer patients. Epithelial-mesenchymal transition (EMT) is recognized as the first step of tumor invasion and metastasis. Many studies have demonstrated that cell fusion is a common phenomenon and plays a critical role in cancer development and progression. At present, cancer stem cell fusion has been considered as a new mechanism of cancer metastasis. Mesenchymal stromal/stem cell (MSC) is a kind of adult stem cells with high self-renewal ability and multidifferentiation potential, which is used as a very promising fusogenic candidate in the tumor microenvironment and has a crucial role in cancer progression. Many research results have shown that MSCs are involved in the regulation of tumor growth and metastasis through cell fusion. However, the role of cell fusion between MSCs and malignant cells in tumor growth and metastasis is still controversial. Several studies have demonstrated that MSCs can enhance malignant characteristics, promoting tumor growth and metastasis by fusing with malignant cells, while other conflicting reports believe that MSCs can reduce tumorigenicity upon fusion with malignant cells. In this review, we summarize the recent research on cell fusion events between MSCs and malignant cells in tumor growth and metastasis. The elucidation of the molecular mechanisms between MSC fusion and tumor metastasis may provide an effective strategy for tumor biotherapy.

Tracking of Infused Mesenchymal Stem Cells in Injured Pulmonary Tissue in Atm-Deficient Mice

Pulmonary failure is the main cause of morbidity and mortality in the human chromosomal instability syndrome Ataxia-telangiectasia (A-T). Major phenotypes include recurrent respiratory tract infections and bronchiectasis, aspiration, respiratory muscle abnormalities, interstitial lung disease, and pulmonary fibrosis. At present, no effective pulmonary therapy for A-T exists. Cell therapy using adipose-derived mesenchymal stromal/stem cells (ASCs) might be a promising approach for tissue regeneration. The aim of the present project was to investigate whether ASCs migrate into the injured lung parenchyma of Atm-deficient mice as an indication of incipient tissue damage during A-T. Therefore, ASCs isolated from luciferase transgenic mice (mASCs) were intravenously transplanted into Atm-deficient and wild-type mice. Retention kinetics of the cells were monitored using in vivo bioluminescence imaging (BLI) and completed by subsequent verification using quantitative real-time polymerase chain reaction (qRT-PCR). The in vivo imaging and the qPCR results demonstrated migration accompanied by a significantly longer retention time of transplanted mASCs in the lung parenchyma of Atm-deficient mice compared to wild type mice. In conclusion, our study suggests incipient damage in the lung parenchyma of Atm-deficient mice. In addition, our data further demonstrate that a combination of luciferase-based PCR together with BLI is a pivotal tool for tracking mASCs after transplantation in models of inflammatory lung diseases such as A-T.

Mesenchymal stromal/stem cell-derived extracellular vesicles in tissue repair: challenges and opportunities

Mesenchymal stem/stromal cells (MSCs) are important players in tissue homeostasis and regeneration owing to their immunomodulatory potential and release of trophic factors that promote healing. They have been increasingly used in clinical trials to treat multiple conditions associated with inflammation and tissue damage such as graft versus host disease, orthopedic injuries and cardiac and liver diseases. Recent evidence demonstrates that their beneficial effects are derived, at least in part, from their secretome. In particular, data from animal models and first-in-man studies indicate that MSC-derived extracellular vesicles (MSC-EVs) can exert similar therapeutic potential as their cells of origin. MSC-EVs are membranous structures loaded with proteins, lipids, carbohydrates and nucleic acids, which play an important role in cell-cell communication and may represent an attractive alternative for cell-based therapy. In this article we summarize recent advances in the use of MSC-EVs for tissue repair. We highlight several isolation and characterization approaches used to enrich MSC-derived EVs. We discuss our current understanding of the relative contribution of the MSC-EVs to the immunomodulatory and regenerative effects mediated by MSCs and MSC secretome. Finally we highlight the challenges and opportunities, which come with the potential use of MSC-EVs as cell free therapy for conditions that require tissue repair.

Immune Dysregulation in HFpEF: A Target for Mesenchymal Stem/Stromal Cell Therapy

Over 26 million people worldwide suffer from heart failure, a disease associated with a 1 year mortality rate of 22%. Half of these patients present heart failure with preserved ejection fraction (HFpEF), for which there is no available therapy to improve prognosis. HFpEF is strongly associated with aging, inflammation, and comorbid burden, which are thought to play causal roles in disease development. Mesenchymal stromal/stem cells (MSCs) have potent immunomodulatory actions and promote tissue healing, thus representing an attractive therapeutic option in HFpEF. In this review, we summarize recent data suggesting that a two-hit model of immune dysregulation lies at the heart of the HFpEF. A first hit is represented by genetic mutations associated with clonal hematopoiesis of indeterminate potential (CHIP), which skew immune cells toward a pro-inflammatory phenotype, are associated with HFpEF development in animal models, and with immune dysregulation and risk of HF hospitalization in patients. A second hit is induced by cardiovascular risk factors, which cause subclinical cardiac dysfunction and production of danger signals. In mice, these attract proinflammatory macrophages, Th1 and Th17 cells into the myocardium, where they are required for the development of HFpEF. MSCs have been shown to reduce the pro-inflammatory activity of immune cell types involved in murine HFpEF in vitro, and to reduce myocardial fibrosis and improve diastolic function in vivo, thus they may efficiently target immune dysregulation in HFpEF and stop disease progression.

Adipose-derived stromal/stem cells successfully attenuate the fibrosis of scleroderma mouse models

AIM

Systemic sclerosis (SSc) is an autoimmune disease characterized by skin and lung fibrosis. Although SSc has a high mortality risk, an effective treatment for the disease has not been established yet. Mesenchymal stromal/stem cells (MSCs) are multipotential nonhematopoietic progenitor cells that have the ability to regulate immune responses. Adipose-derived stromal/stem cells (ASCs), one of the types of MSCs, have the advantage of accessibility and potent immunomodulatory effects when compared with other MSCs, such as bone marrow-derived MSCs. This study aimed to investigate the antifibrotic effect of ASCs in scleroderma mouse models, including bleomycin-induced scleroderma and sclerodermatous chronic graft-versus-host disease (Scl-cGVHD) models.

METHOD

ASCs were intravenously administered to a bleomycin-induced scleroderma or Scl-cGVHD model on day 0. We compared the skin and lung fibrosis of scleroderma model mice between the ASC-treated group and control group.

RESULTS

Administration of ASCs attenuated the skin and lung fibrosis of bleomycin-induced scleroderma and Scl-cGVHD model mice compared to that in the control mice. Immunohistochemical staining showed that ASCs suppressed the infiltration of CD4⁺ , CD8⁺ T cells and macrophages into the dermis of bleomycin model mice compared to that in control mice. In addition, ASCs attenuated the messenger RNA expression of collagen and fibrogenic cytokines, such as interleukin (IL)-6 and IL-13, in the skin of bleomycin model mice. ASCs also reduced the frequency of fibrogenic cytokine-producing CD4⁺ T cells and effector B cells in the spleen of bleomycin model mice.

CONCLUSION

ASCs could prove to be a potential therapeutic agent for use in patients with SSc.

Blocking the FSTL1-DIP2A Axis Improves Anti-tumor Immunity

Immune dysfunction is a strong factor in the resistance of cancer to treatment. Blocking immune checkpoint pathways is a promising approach to improve anti-tumor immunity, but the clinical efficacies are still limited. We previously identified follistatin-like 1 (FSTL1) as a determinant of immune dysfunction mediated by mesenchymal stromal/stem cells (MSCs) and immunoregulatory cells. Here, we demonstrate that blocking FSTL1 but not immune checkpoint pathways significantly suppresses cancer progression and metastasis in several mouse tumor models with increased MSCs. Expression of DIP2A (the receptor of FSTL1) in tumor cells is critical for FSTL1-induced immunoresistance. FSTL1/DIP2A co-positivity in tumor tissues correlates with poor prognosis in NSCLC patients. Thus, breaking the FSTL1-DIP2A axis may be a useful strategy for successfully inducing anti-tumor immunity.

Isolation, Characterization, Differentiation and Immunomodulatory Capacity of Mesenchymal Stromal/Stem Cells from Human Perirenal Adipose Tissue. Cells. 2019;8:1346. [PMID: 31671899 PMCID: PMC6928994 DOI: 10.3390/cells8111346]

Mesenchymal stromal/stem cells (MSCs) are immature multipotent cells, which represent a rare population in the perivascular niche within nearly all tissues. The most abundant source to isolate MSCs is adipose tissue. Currently, perirenal adipose tissue is rarely described as the source of MSCs. MSCs were isolated from perirenal adipose tissue (prASCs) from patients undergoing tumor nephrectomies, cultured and characterized by flow cytometry and their differentiation potential into adipocytes, chondrocytes, osteoblasts and epithelial cells. Furthermore, prASCs were stimulated with lipopolysaccharide (LPS), lipoteichoic acid (LTA) or a mixture of cytokines (cytomix). In addition, prASC susceptibility to human cytomegalovirus (HCMV) was investigated. The expression of inflammatory readouts was estimated by qPCR and immunoassay. HCMV infection was analyzed by qPCR and immunostaining. Characterization of cultured prASCs shows the cells meet the criteria of MSCs and prASCs can undergo trilineage differentiation. Cultured prASCs can be induced to differentiate into epithelial cells, shown by cytokeratin 18 expression. Stimulation of prASCs with LPS or cytomix suggests the cells are capable of initiating an inflammation-like response upon stimulation with LPS or cytokines, whereas, LTA did not induce a significant effect on the readouts (ICAM-1, IL-6, TNFα, MCP-1 mRNA and IL-6 protein). HCMV broadly infects prASCs, showing a viral load dependent cytopathological effect (CPE). Our current study summarizes the isolation and culture of prASCs, clearly characterizes the cells, and demonstrates their immunomodulatory potential and high permissiveness for HCMV.

Stromal vascular fraction technologies and clinical applications

Introduction: The heterogeneous pool of cells found in the stromal vascular fraction of adipose tissue (SVF) and the purified mesenchymal stromal/stem cells (ASCs) isolated from this pool have increasingly been used as therapeutic tools in regenerative medicine.Areas covered: As SVF and ASCs are different, and should be used in different manners according to various clinical and biological indications, we reviewed the current literature, and focused on the clinical use of SVF to appraise the main medical fields for development. Both enzymatic digestion and mechanical disruption have been used to obtain SVF for non-homologous use. The safety and/or benefits of SVF have been examined in 71 clinical studies in various contexts, mainly musculoskeletal conditions, wound healing, urogenital, and cardiovascular and respiratory diseases. The use of SVF as a therapy remains experimental, with few clinical trials.Expert opinion: SVF provides a cellular and molecular microenvironment for regulation of ASC' activities under different clinical conditions. SVF may enhance angiogenesis and neovascularization in wound healing, urogenital and cardiovascular diseases. In joint conditions, therapeutic benefits may rely on paracrine immune-modulatory and anti-inflammatory mechanisms. Novel point of care methods are emerging to refine SVF in ways that meet the regulatory requirements for minimal manipulation.

Mesenchymal stem cells: Cell therapy and regeneration potential

Rapid advances in the isolation of multipotent progenitor cells, routinely called mesenchymal stromal/stem cells (MSCs), from various human tissues and organs have provided impetus to the field of cell therapy and regenerative medicine. The most widely studied sources of MSCs include bone marrow, adipose, muscle, peripheral blood, umbilical cord, placenta, fetal tissue, and amniotic fluid. According to the standard definition of MSCs, these clonal cells adhere to plastic, express cluster of differentiation (CD) markers such as CD73, CD90, and CD105 markers, and can differentiate into adipogenic, chondrogenic, and osteogenic lineages in vitro. However, isolated MSCs have been reported to vary in their potency and self-renewal potential. As a result, the MSCs used for clinical applications often lead to variable or even conflicting results. The lack of uniform characterization methods both in vitro and in vivo also contributes to this confusion. Therefore, the name "MSCs" itself has been increasingly questioned lately. As the use of MSCs is expanding rapidly, there is an increasing need to understand the potential sources and specific potencies of MSCs. This review discusses and compares the characteristics of MSCs and suggests that the variations in their distinctive features are dependent on the source and method of isolation as well as epigenetic changes during maintenance and growth. We also discuss the potential opportunities and challenges of MSC research with the hope to stimulate their use for therapeutic and regenerative medicine.

Mesenchymal stromal cells for ocular surface repair

INTRODUCTION

Cornea is a transparent, robust tissue that comprises highly organized cells. Disruption of this specialized tissue can lead to scarring and subsequent blindness, making corneal damage a considerable challenge worldwide. At present, the available medical treatments are unable to address the wide range of corneal diseases. Mesenchymal stem cells (MSCs) have increasingly been investigated for their regenerative effect on ocular surface injury due to their unique ability for growth factor production, anti-inflammatory activity, immunomodulatory capacity and differentiation into multiple cell lineages.

AREAS COVERED

Within this review, we explore the pathogenesis of corneal disorders in response to injury and disease, and the potential for MSCs to modulate this process as a treatment. Through the review of over 25 animal studies, we investigate the common mechanisms of action by which MSCs have their effect and discuss their potential for treating and/or preventing corneal deterioration

EXPERT OPINION

Depending on the environmental cues, MSCs can exert a potent effect on corneal wound healing through reducing opacity and vascularization, whilst promoting re-epithelialization. Whilst their mechanism is multifactorial, it seems clear that the anti-inflammatory/immunomodulatory factors they produce in response to damage are key to their control of cellular milieu and improving healing outcomes.

Mesenchymal Stromal Cell Derived Extracellular Vesicles Reduce Hypoxia-Ischaemia Induced Perinatal Brain Injury

Background

Neonatal hypoxic-ischemic (HI) insult is a leading cause of disability and death in newborns, with therapeutic hypothermia being the only currently available clinical intervention. Thus there is a great need for adjunct and novel treatments for enhanced or alternative post-HI neuroprotection. Extracellular vesicles (EVs) derived from mesenchymal stromal/stem cells (MSCs) have recently been shown to exhibit regenerative effects in various injury models. Here we present findings showing neuroprotective effects of MSC-derived EVs in the Rice–Vannucci model of severe HI-induced neonatal brain insult.

Methods

Mesenchymal stromal/stem cell-derived EVs were applied intranasally immediately post HI-insult and behavioral outcomes were observed 48 h following MSC-EV treatment, as assessed by negative geotaxis. Brains were thereafter excised and assessed for changes in glial responses, cell death, and neuronal loss as markers of damage at 48 h post HI-insult.

Results

Brains of the MSC-EV treated group showed a significant decrease in microglial activation, cell death, and percentage tissue volume loss in multiple brain regions, compared to the control-treated groups. Furthermore, negative geotaxis test showed improved behavioral outcomes at 48 h following MSC-EV treatment.

Conclusion

Our findings highlight the clinical potential of using MSC-derived EVs following neonatal hypoxia-ischaemia.

Tracking of Adipose-Derived Mesenchymal Stromal/Stem Cells in a Model of Cisplatin-Induced Acute Kidney Injury: Comparison of Bioluminescence Imaging versus qRT-PCR

Determining the cell fate and the distribution of mesenchymal stromal/stem cells (MSCs) after transplantation are essential parts of characterizing the mechanisms of action and biosafety profile of stem cell therapy. Many recent studies have shown that MSCs migrate into injured tissues, but are only detectable at extremely low frequencies. We investigated the cell fate of MSCs after transplantation in an acute kidney injury (AKI) mouse model using in vivo bioluminescence imaging (BLI) and subsequent verification of cell migration using quantitative real-time polymerase chain reaction (qRT-PCR). The AKI was induced by a single injection of cisplatin (8 or 12 mg/kg). One day later, adipose-derived mesenchymal stromal/stem cells isolated from luciferase transgenic mice (Luc⁺-mASCs, 5 × 10⁵) were intravenously transplanted. Migration kinetics of the cells was monitored using BLI on day 1, 3, and 6, and finally via quantitative real-time PCR at the endpoint on day 6. Using BLI, infused Luc⁺-mASCs could only be detected in the lungs, but not in the kidneys. In contrast, PCR endpoint analysis revealed that Luc-specific mRNA could be detected in injured renal tissue; compared to the control group, the induction was 2.2-fold higher for the 8 mg/kg cisplatin group (p < 0.05), respectively 6.1-fold for the 12 mg/kg cisplatin group (p < 0.001). In conclusion, our study demonstrated that Luc-based real-time PCR rather than BLI is likely to be a better tool for cell tracking after transplantation in models such as cisplatin-induced AKI.

Effect of Different Preconditioning Regimens on the Expression Profile of Murine Adipose-Derived Stromal/Stem Cells

Stem cell-based therapies require cells with a maximum regenerative capacity in order to support regeneration after tissue injury and organ failure. Optimization of this regenerative potential of mesenchymal stromal/stem cells (MSC) or their conditioned medium by in vitro preconditioning regimens are considered to be a promising strategy to improve the release of regenerative factors. In the present study, MSC were isolated from inguinal adipose tissue (mASC) from C57BL/6 mice, cultured, and characterized. Then, mASC were either preconditioned by incubation in a hypoxic environment (0.5% O₂), or in normoxia in the presence of murine epidermal growth factor (EGF) or tumor necrosis factor α (TNFα) for 48 h. Protein expression was measured by a commercially available array. Selected factors were verified by PCR analysis. The expression of 83 out of 308 proteins (26.9%) assayed was found to be increased after preconditioning with TNFα, whereas the expression of 61 (19.8%) and 70 (22.7%) proteins was increased after incubation with EGF or in hypoxia, respectively. Furthermore, we showed the proliferation-promoting effects of the preconditioned culture supernatants on injured epithelial cells in vitro. Our findings indicate that each preconditioning regimen tested induced an individual expression profile with a wide variety of factors, including several growth factors and cytokines, and therefore may enhance the regenerative potential of mASC for cell-based therapies.