Preconditioning of Human Mesenchymal Stem Cells to Enhance Their Regulation of the Immune Response. Stem Cells Int. 2016;2016:3924858. [PMID: 27822228 PMCID: PMC5086389 DOI: 10.1155/2016/3924858]

Culture Substrates for Improved Manufacture of Mesenchymal Stromal Cell Therapies

Recent developments in mesenchymal stromal cell (MSC) therapies have increased the demand for tools to improve their manufacture, including the selection of optimal culture substrate materials. While many clinical manufacturers use planar tissue culture plastic (TCP) surfaces for MSC production, others have begun exploring the use of alternative culture substrates that present a variety of spatial, mechanical, and biochemical cues that influence cell expansion and resulting cell quality. In this review, the effects of culture and material properties distinct from traditional planar TCP surfaces on MSC proliferation, surface marker expression, and commonly used indications for therapeutic potency are examined. The different properties summarized include the use of alternative culture formats such as cellular aggregates or 3D scaffolds, as well as the effects of culture substrate stiffness and presentation of specific adhesive ligands and topographical cues. Specific substrate properties can be related to greater cell expansion and improvement in specific therapeutic functionalities, demonstrating the utility of culture materials in further improving the clinical-scale manufacture of highly secretory MSC products.

Function of Dental Follicle Progenitor/Stem Cells and Their Potential in Regenerative Medicine: From Mechanisms to Applications

Dental follicle progenitor/stem cells (DFPCs) are a group of dental mesenchyme stem cells that lie in the dental follicle and play a critical role in tooth development and maintaining function. Originating from neural crest, DFPCs harbor a multipotential differentiation capacity. More importantly, they have superiorities, including the easy accessibility and abundant sources, active self-renewal ability and noncontroversial sources compared with other stem cells, making them an attractive candidate in the field of tissue engineering. Recent advances highlight the excellent properties of DFPCs in regeneration of orofacial tissues, including alveolar bone repair, periodontium regeneration and bio-root complex formation. Furthermore, they play a unique role in maintaining a favorable microenvironment for stem cells, immunomodulation and nervous related tissue regeneration. This review is intended to summarize the current knowledge of DFPCs, including their stem cell properties, physiological functions and clinical application potential. A deep understanding of DFPCs can thus inspire novel perspectives in regenerative medicine in the future.

Hypoxic mesenchymal stem cells ameliorate acute kidney ischemia-reperfusion injury via enhancing renal tubular autophagy

BACKGROUND

Acute kidney injury (AKI) is an emerging global healthcare issue without effective therapy yet. Autophagy recycles damaged organelles and helps maintain tissue homeostasis in acute renal ischemia-reperfusion (I/R) injury. Hypoxic mesenchymal stem cells (HMSCs) represent an innovative cell-based therapy in AKI. Moreover, the conditioned medium of HMSCs (HMSC-CM) rich in beneficial trophic factors may serve as a cell-free alternative therapy. Nonetheless, whether HMSCs or HMSC-CM mitigate renal I/R injury via modulating tubular autophagy remains unclear.

METHODS

Renal I/R injury was induced by clamping of the left renal artery with right nephrectomy in male Sprague-Dawley rats. The rats were injected with either PBS, HMSCs, or HMSC-CM immediately after the surgery and sacrificed 48 h later. Renal tubular NRK-52E cells subjected to hypoxia-reoxygenation (H/R) injury were co-cultured with HMSCs or treated with HMSC-CM to assess the regulatory effects of HSMCs on tubular autophagy and apoptosis. The association of tubular autophagy gene expression and renal recovery was also investigated in patients with ischemic AKI.

RESULT

HMSCs had a superior anti-oxidative effect in I/R-injured rat kidneys as compared to normoxia-cultured mesenchymal stem cells. HMSCs further attenuated renal macrophage infiltration and inflammation, reduced tubular apoptosis, enhanced tubular proliferation, and improved kidney function decline in rats with renal I/R injury. Moreover, HMSCs suppressed superoxide formation, reduced DNA damage and lipid peroxidation, and increased anti-oxidants expression in renal tubular epithelial cells during I/R injury. Co-culture of HMSCs with H/R-injured NRK-52E cells also lessened tubular cell death. Mechanistically, HMSCs downregulated the expression of pro-inflammatory interleukin-1β, proapoptotic Bax, and caspase 3. Notably, HMSCs also upregulated the expression of autophagy-related LC3B, Atg5 and Beclin 1 in renal tubular cells both in vivo and in vitro. Addition of 3-methyladenine suppressed the activity of autophagy and abrogated the renoprotective effects of HMSCs. The renoprotective effect of tubular autophagy was further validated in patients with ischemic AKI. AKI patients with higher renal LC3B expression were associated with better renal recovery.

CONCLUSION

The present study describes that the enhancing effect of MSCs, and especially of HMCSs, on tissue autophagy can be applied to suppress renal tubular apoptosis and attenuate renal impairment during renal I/R injury in the rat. Our findings provide further mechanistic support to HMSCs therapy and its investigation in clinical trials of ischemic AKI.

MSCs and Inflammatory Cells Crosstalk in Regenerative Medicine: Concerted Actions for Optimized Resolution Driven by Energy Metabolism

Mesenchymal stromal cells (MSCs) are currently widely used in cell based therapy regarding to their remarkable efficacy in controlling the inflammatory status in patients. Despite recent progress and encouraging results, inconstant therapeutic benefits are reported suggesting that significant breakthroughs in the understanding of MSCs immunomodulatory mechanisms of action remains to be investigated and certainly apprehended from original point of view. This review will focus on the recent findings regarding MSCs close relationship with the innate immune compartment, i.e. granulocytes and myeloid cells. The review will also consider the intercellular mechanism of communication involved, such as factor secretion, cell-cell contact, extracellular vesicles, mitochondria transfer and efferocytosis. Immune-like-properties of MSCs supporting part of their therapeutic effect in the clinical setting will be discussed, as well as their potentials (immunomodulatory, anti-bacterial, anti-inflammatory, anti-oxidant defenses and metabolic adaptation…) and effects mediated, such as cell polarization, differentiation, death and survival on various immune and tissue cell targets determinant in triggering tissue regeneration. Their metabolic properties in term of sensing, reacting and producing metabolites influencing tissue inflammation will be highlighted. The review will finally open to discussion how ongoing scientific advances on MSCs could be efficiently translated to clinic in chronic and age-related inflammatory diseases and the current limits and gaps that remain to be overcome to achieving tissue regeneration and rejuvenation.

Bone Marrow Mesenchymal Stromal Cells on Silk Fibroin Scaffolds to Attenuate Polymicrobial Sepsis Induced by Cecal Ligation and Puncture

Suitable scaffolds with appropriate mechanical and biological properties can improve mesenchymal stromal cell (MSC) therapy. Because silk fibroins (SFs) are biocompatible materials, they were electrospun and applied as scaffolds for MSC therapy. Consequently, interferon (IFN)-primed human bone marrow MSCs on SF nanofibers were administered into a polymicrobial sepsis murine model. The IL-6 level gradually decreased from 40 ng/mL at 6 h after sepsis to 35 ng/mL at 24 h after sepsis. The IL-6 level was significantly low as 5 ng/mL in primed MSCs on SF nanofibers, and 15 ng/mL in primed MSCs on the control surface. In contrast to the acute response, inflammation-related factors, including HO-1 and COX-2 in chronic liver tissue, were effectively inhibited by MSCs on both SF nanofibers and the control surface at the 5-day mark after sepsis. An in vitro study indicated that the anti-inflammatory function of MSCs on SF nanofibers was mediated through enhanced COX-2-PGE₂ production, as indomethacin completely abrogated PGE₂ production and decreased the survival rate of septic mice. Thus, SF nanofiber scaffolds potentiated the anti-inflammatory and immunomodulatory functions of MSCs, and were beneficial as a culture platform for the cell therapy of inflammatory disorders.

Human nasal septal chondrocytes (NSCs) preconditioned on NSC-derived matrix improve their chondrogenic potential

Background

Extracellular matrix (ECM) has a profound effect on cell behaviors. In this study, we prepare a decellularized human nasal septal chondrocyte (NSC)-derived ECM (CHDM), as a natural (N-CHDM) or soluble form (S-CHDM), and investigate their impact on NSCs differentiation.

Methods

N-CHDM, S-CHDM were obtained from NSC. To evaluate function of NSC cultured on each substrate, gene expression using chondrogenic marker, and chondrogenic protein expression were tested. Preconditioned NSCs-loaded scaffolds were transplanted in nude mice for 3 weeks and analyzed.

Results

When cultivated on each substrate, NSCs exhibited similar cell spread area but showed distinct morphology on N-CHDM with significantly lower cell circularity. They were highly proliferative on N-CHDM than S-CHDM and tissue culture plastic (TCP), and showed more improved cell differentiation, as assessed via chondrogenic marker (Col2, Sox9, and Aggrecan) expression and immunofluorescence of COL II. We also investigated the effect of NSCs preconditioning on three different 2D substrates while NSCs were isolated from those substrates, subsequently transferred to 3D mesh scaffold, then cultivated them in vitro or transplanted in vivo. The number of cells in the scaffolds was similar to each other at 5 days but cell differentiation was notably better with NSCs preconditioned on N-CHDM, as assessed via real-time q-PCR, Western blot, and immunofluorescence. Moreover, when those NSCs-loaded polymer scaffolds were transplanted subcutaneously in nude mice for 3 weeks and analyzed, the NSCs preconditioned on the N-CHDM showed significantly advanced cell retention in the scaffold, more cells with a chondrocyte lacunae structure, and larger production of cartilage ECM (COL II, glycosaminoglycan).

Conclusions

Taken together, a natural form of decellularized ECM, N-CHDM would present an advanced chondrogenic potential over a reformulated ECM (S-CHDM) or TCP substrate, suggesting that N-CHDM may hold more diverse signaling cues, not just limited to ECM component.

The Current Status of Mesenchymal Stromal Cells: Controversies, Unresolved Issues and Some Promising Solutions to Improve Their Therapeutic Efficacy

Mesenchymal stromal cells (MSCs) currently constitute the most frequently used cell type in advanced therapies with different purposes, most of which are related with inflammatory processes. Although the therapeutic efficacy of these cells has been clearly demonstrated in different disease animal models and in numerous human phase I/II clinical trials, only very few phase III trials using MSCs have demonstrated the expected potential therapeutic benefit. On the other hand, diverse controversial issues on the biology and clinical applications of MSCs, including their specific phenotype, the requirement of an inflammatory environment to induce immunosuppression, the relevance of the cell dose and their administration schedule, the cell delivery route (intravascular/systemic vs. local cell delivery), and the selected cell product (i.e., use of autologous vs. allogeneic MSCs, freshly cultured vs. frozen and thawed MSCs, MSCs vs. MSC-derived extracellular vesicles, etc.) persist. In the current review article, we have addressed these issues with special emphasis in the new approaches to improve the properties and functional capabilities of MSCs after distinct cell bioengineering strategies.

Exposure of Mesenchymal Stem Cells to an Alzheimer's Disease Environment Enhances Therapeutic Effects

Mesenchymal stem cells (MSCs) have emerged as a promising tool for the treatment of Alzheimer's disease (AD). Previous studies suggested that the coculture of human MSCs with AD in an in vitro model reduced the expression of amyloid-beta 42 (Aβ42) in the medium as well as the overexpression of amyloid-beta- (Aβ-) degrading enzymes such as neprilysin (NEP). We focused on the role of primed MSCs (human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) exposed to an AD cell line via a coculture system) in reducing the levels of Aβ and inhibiting cell death. We demonstrated that mouse groups treated with naïve MSCs and primed MSCs showed significant reductions in cell death, ubiquitin conjugate levels, and Aβ levels, but the effects were greater in primed MSCs. Also, mRNA sequencing data analysis indicated that high levels of TGF-β induced primed-MSCs. Furthermore, treatment with TGF-β reduced Aβ expression in an AD transgenic mouse model. These results highlighted AD environmental preconditioning is a promising strategy to reduce cell death and ubiquitin conjugate levels and maintain the stemness of MSCs. Further, these data suggest that human WJ-MSCs exposed to an AD environment may represent a promising and novel therapy for AD.

Latest advances to enhance the therapeutic potential of mesenchymal stromal cells for the treatment of immune-mediated diseases

Mesenchymal stromal cells (MSCs) present the capacity to secrete multiple immunomodulatory factors in response to their microenvironment. This property grants them a golden status among the novel alternatives to treat multiple diseases in which there is an unneeded or exaggerated immune response. However, important challenges still make difficult the clinical implementation of MSC-based therapies, being one of the most remarkable the lack of efficacy due to their transient immunomodulatory effects. To overcome this issue and boost the regulatory potential of MSCs, multiple strategies are currently being explored. Some of them consist of ex vivo pre-conditioning MSCs prior to their administration, including exposure to pro-inflammatory cytokines or to low oxygen concentrations. However, currently, alternative strategies that do not require such ex vivo manipulation are gaining special attention. Among them, the recreation of a three dimensional (3D) environment is remarkable. This approach has been reported to not only boost the immunomodulatory potential of MSCs but also increase their in vivo persistence and viability. The present work revises the therapeutic potential of MSCs, highlighting their immunomodulatory activity as a potential treatment for diseases caused by an exacerbated or unnecessary immune response. Moreover, it offers an updated vision of the most widely employed pre-conditioning strategies and 3D systems intended to enhance MSC-mediated immunomodulation, to conclude discussing the major challenges still to overcome in the field.

Therapeutic Potential of Mesenchymal Stem Cells and Their Products in Lung Diseases-Intravenous Administration versus Inhalation

The number of publications studying the therapeutic use of stem cells has steadily increased since 2000. Compared to other applications, there has been little interest in the evaluation of mesenchymal stem cells (MSCs) and MSC-derived products (mostly extracellular vesicles) for the treatment of respiratory diseases. Due to the lack of efficient treatments for acute respiratory distress syndrome caused by infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the action of MSCs has also been studied. This review describes mode of action and use of MSCs and MSC-derived products in the treatment of lung diseases including the respective advantages and limitations of the products. Further, issues related to standardized production are addressed. Administration by inhalation of MSCs, compared to intravenous injection, could decrease cell damage by shear stress, eliminate the barrier to reach target cells in the alveoli, prevent thrombus formation in the pulmonary vasculature and retention in filter for extracorporeal membrane oxygenation. There is more feasible to deliver extracellular vesicles than MSCs with inhalers, offering the advantage of non-invasive and repeated administration by the patient. Major obstacles for comparison of results are heterogeneity of the products, differences in the treatment protocols and small study cohorts.

D-galactose-induced toxicity associated senescence mitigated by alpinate oxyphyllae fructus fortified adipose-derived mesenchymal stem cells

This study addresses the effect of D-galactose-induced toxicity associated senescence mitigated by alpinate oxyphyllae fructus (AOF; Alpinia oxyphylla Miq) extracts fortified with adipose-derived mesenchymal stem cells (ADMSCs) in rats. Male 18 week-old Wistar Kyoto (WKY) rats were used in this study. We analyzed cardiac fibrosis by Masson's trichrome staining. The tissue sections were dyed using hematoxylin and eosin (H&E). Tissue sections were stained for the restoration of Nrf2 expression in treatment groups by immunohistochemistry. Immunohistochemistry and western blotting analysis showed that AOF with ADMSCs could significantly reduce aging-induced oxidative stress in D-galactose-induced aging rat hearts by inducing Nrf2 pathway. Reduction in ROS resulted in the suppression of inflammatory signals (p-NF-κB and IL-6). Histopathological studies were showed an increased interstitium and collagen accumulation in aging-induced heart sections. However, AOF and ADMSCs treated hearts were recovered from cardiac remodeling. Furthermore, hypertrophy and fibrosis associated markers were also significantly reduced (P < .05) in treatment groups. We speculate that ADMSCs might activate certain paracrine factors, which could target the upstream activator of aging associated cardiac complications and AOF might provide homing for these stem cells.

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

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

Hydrogen Peroxide-Preconditioned Human Adipose-Derived Stem Cells Enhance the Recovery of Oligodendrocyte-Like Cells after Oxidative Stress-Induced Damage

Oxidative stress associated with neuroinflammation is a key process involved in the pathophysiology of neurodegenerative diseases, and therefore, has been proposed as a crucial target for new therapies. Recently, the therapeutic potential of human adipose-derived stem cells (hASCs) has been investigated as a novel strategy for neuroprotection. These cells can be preconditioned by exposing them to mild stress in order to improve their response to oxidative stress. In this study, we evaluate the therapeutic potential of hASCs preconditioned with low doses of H₂O₂ (called HC016 cells) to overcome the deleterious effect of oxidative stress in an in vitro model of oligodendrocyte-like cells (HOGd), through two strategies: i, the culture of oxidized HOGd with HC016 cell-conditioned medium (CM), and ii, the indirect co-culture of oxidized HOGd with HC016 cells, which had or had not been exposed to oxidative stress. The results demonstrated that both strategies had reparative effects, oxidized HC016 cell co-culture being the one associated with the greatest recovery of the damaged HOGd, increasing their viability, reducing their intracellular reactive oxygen species levels and promoting their antioxidant capacity. Taken together, these findings support the view that HC016 cells, given their reparative capacity, might be considered an important breakthrough in cell-based therapies.

Daphne mucronata enhances cell proliferation and protects human adipose stem cells against monosodium iodoacetate induced oxidative stress in vitro

Mesenchymal stem cells (MSCs) are being used to treat many diseases as they exhibit great regenerative potential. However, MSC's transplantation sometimes does not yield the maximum regenerative outcome as they are unable to survive in inflammatory conditions. Several approaches including preconditioning are used to improve the survival rate of mesenchymal stem cells. One such recently reported approach is preconditioning MSCs with plant extracts. The present study was designed to evaluate the effect of Daphne mucronata extract on stressed human adipose-derived mesenchymal stem cells (hADMSCs). Isolated hADMSCs were preconditioned with different concentrations of Daphne muconata extract and the protective, proliferative, antioxidant and anti-inflammatory effect was assessed through various assays and expression analysis of inflammatory markers regulated through NF-κB pathway. Results suggest that preconditioning hADMSCs with Daphne mucronata increased the cell viability, proliferative and protective potential of hADMSCs with a concomitant reduction in LDH, ROS and elevation in SOD activity. Moreover, both the ELISA and gene expression analysis demonstrated down regulations of inflammatory markers (IL1-β, TNF-α, p65, p50, MMP13) in Daphne mucronata preconditioned hADMSCs as compared to stress. This is the first study to report the use of MIA induced oxidative stress against hADMSC's and effect of Daphne mucronata on stressed hADMSCs. Results of these studies provided evidence that Daphne mucronata protects the hADMSCs during stress conditions by down regulating the inflammatory markers and hence increase the viability and proliferative potential of hADMSCs that is crucial for transplantation purposes.

Anti-oncogenic activities exhibited by paracrine factors of MSCs can be mediated by modulation of KITLG and DKK1 genes in glioma SCs in vitro

Cancer stem cells (CSCs) use their stemness properties to perpetuate their lineage and survive chemotherapy. Currently cell-based and cell-free therapies are under investigation to develop novel anti-cancer treatment modalities. We designed this study to investigate how cell extracts of mesenchymal stem cells affect the growth of glioma stem cells in vitro. Gliospheres were generated from the U87MG cell line and treated with conditioned media of Wharton’s jelly and bone marrow mesenchymal stem cells. The effects were investigated at the functional and molecular levels. Our results showed that conditioned media from both types of mesenchymal stem cells changed the morphology of spheres and inhibited the proliferation, invasion, and self-renewal ability of glioma stem cells. At the molecular level, metabolism interruption at oxidative phosphorylation, cell cycle arrest, cell differentiation, and upregulation of the immune response were observed. Furthermore, this effect was mediated by the upregulation of the DKK1 gene inhibiting the Wnt pathway mediated by growth factor activity and downregulation of the KITLG gene activated by growth factor and cytokine activity, inhibiting multiple pathways. We conclude that different types of mesenchymal stem cells possess antitumor properties and their paracrine factors, in combination with anti-immune modalities, can provide practical therapeutic targets for glioblastoma treatment.

Progress of Mesenchymal Stem Cell-Derived Exosomes in Tissue Repair

Mesenchymal stem cells (MSCs) are a kind of adult stem cells with self-replication and multidirectional differentiation, which can differentiate into tissue-specific cells under physiological conditions, maintaining tissue self-renewal and physiological functions. They play a role in the pathological condition by lateral differentiation into tissue-specific cells, replacing damaged tissue cells by playing the role of a regenerative medicine , or repairing damaged tissues through angiogenesis, thereby, regulating immune responses, inflammatory responses, and inhibiting apoptosis. It has become an important seed cell for tissue repair and organ reconstruction, and cell therapy based on MSCs has been widely used clinically. The study found that the probability of stem cells migrating to the damaged area after transplantation or differentiating into damaged cells is very low, so the researchers believe the leading role of stem cell transplantation for tissue repair is paracrine secretion, secreting growth factors, cytokines or other components. Exosomes are biologically active small vesicles secreted by MSCs. Recent studies have shown that they can transfer functional proteins, RNA, microRNAs, and lncRNAs between cells, and greatly reduce the immune response. Under the premise of promoting proliferation and inhibition of apoptosis, they play a repair role in tissue damage, which is caused by a variety of diseases. In this paper, the biological characteristics of exosomes (MSCs-exosomes) derived from mesenchymal stem cells, intercellular transport mechanisms, and their research progress in the field of stem cell therapy are reviewed.

Vadadustat, a HIF Prolyl Hydroxylase Inhibitor, Improves Immunomodulatory Properties of Human Mesenchymal Stromal Cells

The therapeutic potential of mesenchymal stromal cells (MSCs) is largely attributed to their immunomodulatory properties, which can be further improved by hypoxia priming. In this study, we investigated the immunomodulatory properties of MSCs preconditioned with hypoxia-mimetic Vadadustat (AKB-6548, Akebia). Gene expression analysis of immunomodulatory factors was performed by real-time polymerase chain reaction (real-time PCR) on RNA isolated from six human bone-marrow derived MSCs populations preconditioned for 6 h with 40 μM Vadadustat compared to control MSCs. The effect of Vadadustat preconditioning on MSCs secretome was determined using Proteome Profiler and Luminex, while their immunomodulatory activity was assessed by mixed lymphocyte reaction (MLR) and Culturex transwell migration assays. Real-time PCR revealed that Vadadustat downregulated genes related to immune system: IL24, IL1B, CXCL8, PDCD1LG1, PDCD1LG2, HIF1A, CCL2 and IL6, and upregulated IL17RD, CCL28 and LEP. Vadadustat caused a marked decrease in the secretion of IL6 (by 51%), HGF (by 47%), CCL7 (MCP3) (by 42%) and CXCL8 (by 40%). Vadadustat potentiated the inhibitory effect of MSCs on the proliferation of alloactivated human peripheral blood mononuclear cells (PBMCs), and reduced monocytes-enriched PBMCs chemotaxis towards the MSCs secretome. Preconditioning with Vadadustat may constitute a valuable approach to improve the therapeutic properties of MSCs.

Mechanically Stretched Mesenchymal Stem Cells Can Reduce the Effects of LPS-Induced Injury on the Pulmonary Microvascular Endothelium Barrier

Mesenchymal stem cells (MSCs) may improve the treatment of acute respiratory distress syndrome (ARDS). However, few studies have investigated the effects of mechanically stretched -MSCs (MS-MSCs) in in vitro models of ARDS. The aim of this study was to evaluate the potential therapeutic effects of MS-MSCs on pulmonary microvascular endothelium barrier injuries induced by LPS. We introduced a cocultured model of pulmonary microvascular endothelial cell (EC) and MSC medium obtained from MSCs with or without mechanical stretch. We found that Wright-Giemsa staining revealed that MSC morphology changed significantly and cell plasma shrank separately after mechanical stretch. Cell proliferation of the MS-MSC groups was much lower than the untreated MSC group; expression of cell surface markers did not change significantly. Compared to the medium from untreated MSCs, inflammatory factors elevated statistically in the medium from MS-MSCs. Moreover, the paracellular permeability of endothelial cells treated with LPS was restored with a medium from MS-MSCs, while LPS-induced EC apoptosis decreased. In addition, protective effects on the remodeling of intercellular junctions were observed when compared to LPS-treated endothelial cells. These data demonstrated that the MS-MSC groups had potential therapeutic effects on the LPS-treated ECs; these results might be useful in the treatment of ARDS.

A comparative study on the cellular stressors in mesenchymal stem cells (MSCs) and pancreatic β-cells under hyperglycemic milieu

β-cell dysfunction is a critical determinant for both type 1 diabetes and type 2 diabetes and β-cells are shown to be highly susceptible to cellular stressors. Mesenchymal stem cells (MSCs) on the other hand are known to have immunomodulatory potential and preferred in clinical applications. However, there is paucity of a comparative study on these cells in relation to several cellular stressors in response to hyperglycemia and this forms the rationale for the present study. INS1 β-cells and MSCs were subjected to high-glucose treatment without and with Metformin, Lactoferrin, or TUDCA and assessed for stress signaling alterations using gene expression, protein expression, as well as functional read-outs. Compared to the untreated control cells, INS1 β-cells or MSCs treated with high glucose showed significant increase in mRNA expressions of ER stress, senescence, and proinflammation. This was accompanied by increased miR146a target genes and decreased levels of SIRT1, NRF2, and miR146a in both the cell types. Consistent with the mRNA results, protein expression levels do reflect the same alterations. Notably, the alterations are relatively less extent in MSCs compared to INS1 β-cells. Interestingly, three different agents, viz., Metformin, Lactoferrin, or TUDCA, were found to overcome the high glucose-induced cellular stresses in a concerted and inter-linked way and restored the proliferation and migration capacity in MSCs as well as normalized the glucose-stimulated insulin secretion in INS1 β-cells. While our study gives a directionality for potential supplementation of metformin/lactoferrin/TUDCA in optimization protocols of MSCs, we suggest that in vitro preconditioning of MSCs with such factors should be further explored with in-depth investigations to harness and enhance the therapeutic capacity/potential of MSCs.

Preconditioning mesenchymal stromal cells with flagellin enhances the anti‑inflammatory ability of their secretome against lipopolysaccharide‑induced acute lung injury

Acute lung injury (ALI) is a complex condition frequently encountered in the clinical setting. The aim of the present study was to investigate the effect of conditioned media (CM) from human adipose‑derived mesenchymal stromal cells (MSCs) activated by flagellin (F‑CM), a Toll‑like receptor 5 ligand, on inflammation‑induced lung injury. In the in vitro study, RAW264.7 macrophages treated with F‑CM had a higher proportion of cells with the M2 phenotype, lower expression of pro‑inflammatory factors and stronger expression of anti‑inflammatory genes compared with the CM from normal adipose‑derived MSCs. Furthermore, in vivo experiments were performed in mice with ALI induced by intraperitoneal injection of lipopolysaccharide. F‑CM significantly alleviated the lung exudation, inhibited inflammatory cell recruitment in lung tissues and decreased the concentration of inflammatory factors in the bronchoalveolar lavage fluid. These findings indicated that F‑CM has superior anti‑inflammation ability compared with CM, and that it may represent a promising therapeutic approach to the treatment of inflammation‑induced ALI.

Oxidative Stress and Neuroinflammation as a Pivot in Drug Abuse. A Focus on the Therapeutic Potential of Antioxidant and Anti-Inflammatory Agents and Biomolecules

Drug abuse is a major global health and economic problem. However, there are no pharmacological treatments to effectively reduce the compulsive use of most drugs of abuse. Despite exerting different mechanisms of action, all drugs of abuse promote the activation of the brain reward system, with lasting neurobiological consequences that potentiate subsequent consumption. Recent evidence shows that the brain displays marked oxidative stress and neuroinflammation following chronic drug consumption. Brain oxidative stress and neuroinflammation disrupt glutamate homeostasis by impairing synaptic and extra-synaptic glutamate transport, reducing GLT-1, and system X_c⁻ activities respectively, which increases glutamatergic neurotransmission. This effect consolidates the relapse-promoting effect of drug-related cues, thus sustaining drug craving and subsequent drug consumption. Recently, promising results as experimental treatments to reduce drug consumption and relapse have been shown by (i) antioxidant and anti-inflammatory synthetic molecules whose effects reach the brain; (ii) natural biomolecules secreted by mesenchymal stem cells that excel in antioxidant and anti-inflammatory properties, delivered via non-invasive intranasal administration to animal models of drug abuse and (iii) potent anti-inflammatory microRNAs and anti-miRNAs which target the microglia and reduce neuroinflammation and drug craving. In this review, we address the neurobiological consequences of brain oxidative stress and neuroinflammation that follow the chronic consumption of most drugs of abuse, and the current and potential therapeutic effects of antioxidants and anti-inflammatory agents and biomolecules to reduce these drug-induced alterations and to prevent relapse.

State of the Art Review of Cell Therapy in the Treatment of Lung Disease, and the Potential for Aerosol Delivery

Respiratory and pulmonary diseases are among the leading causes of death globally. Despite tremendous advancements, there are no effective pharmacological therapies capable of curing diseases such as COPD (chronic obstructive pulmonary disease), ARDS (acute respiratory distress syndrome), and COVID-19. Novel and innovative therapies such as advanced therapy medicinal products (ATMPs) are still in early development. However, they have exhibited significant potential preclinically and clinically. There are several longitudinal studies published, primarily focusing on the use of cell therapies for respiratory diseases due to their anti-inflammatory and reparative properties, thereby hinting that they have the capability of reducing mortality and improving the quality of life for patients. The primary objective of this paper is to set out a state of the art review on the use of aerosolized MSCs and their potential to treat these incurable diseases. This review will examine selected respiratory and pulmonary diseases, present an overview of the therapeutic potential of cell therapy and finally provide insight into potential routes of administration, with a focus on aerosol-mediated ATMP delivery.

Intranasal delivery of mesenchymal stem cell-derived extracellular vesicles exerts immunomodulatory and neuroprotective effects in a 3xTg model of Alzheimer's disease

The critical role of neuroinflammation in favoring and accelerating the pathogenic process in Alzheimer's disease (AD) increased the need to target the cerebral innate immune cells as a potential therapeutic strategy to slow down the disease progression. In this scenario, mesenchymal stem cells (MSCs) have risen considerable interest thanks to their immunomodulatory properties, which have been largely ascribed to the release of extracellular vesicles (EVs), namely exosomes and microvesicles. Indeed, the beneficial effects of MSC-EVs in regulating the inflammatory response have been reported in different AD mouse models, upon chronic intravenous or intracerebroventricular administration. In this study, we use the triple-transgenic 3xTg mice showing for the first time that the intranasal route of administration of EVs, derived from cytokine-preconditioned MSCs, was able to induce immunomodulatory and neuroprotective effects in AD. MSC-EVs reached the brain, where they dampened the activation of microglia cells and increased dendritic spine density. MSC-EVs polarized in vitro murine primary microglia toward an anti-inflammatory phenotype suggesting that the neuroprotective effects observed in transgenic mice could result from a positive modulation of the inflammatory status. The possibility to administer MSC-EVs through a noninvasive route and the demonstration of their anti-inflammatory efficacy might accelerate the chance of a translational exploitation of MSC-EVs in AD.

H2O2-preconditioned human adipose-derived stem cells (HC016) increase their resistance to oxidative stress by overexpressing Nrf2 and bioenergetic adaptation

BACKGROUND

Mesenchymal stem cells, including those derived from human adipose tissue (hASCs), are currently being widely investigated for cell therapy. However, when transplanted at the site of injury, the survival and engraftment rates of hASCs are low, mainly due to the harsh microenvironment they encounter, characterized by inflammation and oxidative stress. To overcome these therapeutic limitations, cell preconditioning with low-concentration of hydrogen peroxide (H2O2) has been proposed as a plausible strategy to increase their survival and adaptation to oxidative stress. Nonetheless, the underlying mechanisms of this approach are not yet fully understood. In this study, we analyzed molecular and bioenergetic changes that take place in H2O2 preconditioned hASCs.

METHODS

Long-term exposure to a low concentration of H2O2 was applied to obtain preconditioned hASCs (named HC016), and then, their response to oxidative stress was analyzed. The effect of preconditioning on the expression of Nrf2 and its downstream antioxidant enzymes (HO-1, SOD-1, GPx-1, and CAT), and of NF-κB and its related inflammatory proteins (COX-2 and IL-1β), were examined by Western blot. Finally, the Seahorse XF96 Flux analysis system was used to evaluate the mitochondrial respiration and glycolytic function, along with the total ATP production.

RESULTS

We found that under oxidative conditions, HC016 cells increased the survival by (i) decreasing intracellular ROS levels through the overexpression of the transcription factor Nrf2 and its related antioxidant enzymes HO-1, SOD-1, GPx-1, and CAT; (ii) reducing the secretion of pro-inflammatory molecules COX-2 and IL-1β through the attenuation of the expression of NF-κB; and (iii) increasing the total ATP production rate through the adaption of their metabolism to meet the energetic demand required to survive.

CONCLUSIONS

H2O2 preconditioning enhances hASC survival under oxidative stress conditions by stimulating their antioxidant response and bioenergetic adaptation. Therefore, this preconditioning strategy might be considered an excellent tool for strengthening the resistance of hASCs to harmful oxidative stress.

Quality control and immunomodulatory potential for clinical-grade equine bone marrow-derived mesenchymal stromal cells and conditioned medium

This study aimed to assess the safety and reproducibility of cell therapy for its use in clinical practice. We performed immunophenotypic characterization of equine bone marrow-derived mesenchymal stromal cells (BMMSCs) by flow cytometry using CD90, CD19, CD14, CD105, CD45, and HLA-DR markers (n = 4); GTG banding cytogenetic analysis (n = 3); and microbiological quality control (n = 4). The immunomodulatory potentials of BMMSCs (n = 4) and its conditioned medium (CM, n = 3) were investigated by in vitro lymphocyte inhibition assay using phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs). BMMSCs populations isolated from all animals showed high expression of CD90 and CD105, and low expression of CD19, CD4, CD45, and HLA-DR. Of the 60 metaphases analyzed, 5% presented aneuploidy on random chromosomes and no contamination was found based on microbiological analyses. Both treatments significantly inhibited lymphocyte proliferation (> 50%), compared with PHA-stimulated PBMCs (p < 0.0001). These promising results for BMMSCs and CM justify their potential as a therapeutic approach for inflammatory diseases. The techniques used in this study were effective in assessing the quality and determining the minimum criteria for the clinical use of BMMSCs in veterinary medicine.

Umbilical Cord-Derived Mesenchymal Stem Cells Are Able to Use bFGF Treatment and Represent a Superb Tool for Immunosuppressive Clinical Applications

Mesenchymal stem cells (MSCs) have become a promising tool in cellular therapy for restoring immune system haemostasis; however, the success of clinical trials has been impaired by the lack of standardized manufacturing processes. This study aims to determine the suitability of source tissues and culture media for the production of MSC-based advanced therapy medicinal products (ATMPs) and to define parameters to extend the set of release criteria. MSCs were isolated from umbilical cord (UC), bone marrow and lipoaspirate and expanded in three different culture media. MSC phenotype, proliferation capacity and immunosuppressive parameters were evaluated in normal MSCs compared to primed MSCs treated with cytokines mimicking an inflammatory environment. Compared to bone marrow and lipoaspirate, UC-derived MSCs (UC-MSCs) showed the highest proliferative capacity, which was further enhanced by media supplemented with bFGF, while the cells maintained their immunosuppressive characteristics. Moreover, UC-MSCs expanded in the bFGF-enriched medium were the least sensitive to undesirable priming-induced changes in the MSC phenotype. Surface markers and secreted factors were identified to reflect the cell response to inflammatory priming and to be variable among MSCs from different source tissues. This study demonstrates that UC is a favorable cell source for manufacturing MSC-based ATMPs for immunosuppressive applications. UC-MSCs are able to use the bFGF-enriched medium for higher cell yields without the impairment of immunosuppressive parameters and undesirable phenotype changes after inflammatory preconditioning of MSCs before transplantation. Additionally, immunosuppressive parameters were identified to help finding predictors of clinically efficient MSCs in the following clinical trials.

Fibrinogen-Depleted Equine Platelet Lysate Affects the Characteristics and Functionality of Mesenchymal Stem Cells

Fetal bovine serum (FBS) is widely used to culture mesenchymal stem cells (MSCs) in the laboratory; however, FBS has been linked to adverse immune-mediated reactions prompting the search for alternative cell culture medium. Platelet lysate (PL) as an FBS substitute has been shown to promote MSCs growth without compromising their functionality. Fibrinogen contained in PL has been shown to negatively impact the immune modulating properties of MSCs; therefore, we sought to deplete fibrinogen from PL and compare proliferation, viability, and immunomodulatory capacities of MSCs in FBS or PL without fibrinogen. We depleted fibrinogen from equine platelet lysate (ePL) and measured platelet-derived growth factor-beta (PDGF-β), transforming growth factor-beta (TGF-β) and tumor necrosis factor-alpha (TNF-α) through ELISA. First, we determined the ability of 10% ePL or fibrinogen-depleted lysate (fdePL) compared with 10% FBS to suppress monocyte activation by measuring TNF-α from culture supernatants. We then evaluated proliferation, viability, and immunomodulatory characteristics of bone marrow-derived MSCs (BM-MSCs) cultured in FBS or ePL with or without fibrinogen. Growth factor concentrations decreased in ePL after fibrinogen depletion. Lipopolysaccharide (LPS)-stimulated monocytes exposed to ePL and fdePL produced less TNF-α than LPS-stimulated monocytes in 10% FBS. BM-MSCs cultured in fdePL exhibited lower proliferation rates, but similar viability compared with BM-MSCs in ePL. BM-MSCs in fdePL did not effectively suppress TNF-α expression from LPS-stimulated monocytes compared with BM-MSCs in FBS. Depleting fibrinogen results in a lysate that suppresses TNF-α expression from LPS-stimulated monocytes, but that does not support proliferation and immune-modulatory capacity of BM-MSCs as effectively as nondepleted lysate.

The Exposure to Osteoarthritic Synovial Fluid Enhances the Immunomodulatory Profile of Adipose Mesenchymal Stem Cell Secretome

Objective

Several clinical studies have proposed the infusion of adipose mesenchymal stem cells (AMSCs) as an alternative therapy for joint diseases with inflammatory components, such as osteoarthritis. Indeed, AMSCs are able to stimulate tissue repair through a paracrine activity and the interaction with the inflammatory microenvironment seems to have a critical role.

Design

To reproduce the inflammatory microenvironment, AMSCs were exposed to osteoarthritic synovial fluid (SF) for 48 h and the effect of their secretome on differentiation of monocytes (M0) into macrophages M1-like and mature dendritic cells (mDCs) was evaluated. Furthermore, the effect of the secretome of AMSCs exposed to SF was evaluated on the T cell population in terms of T cell proliferation and expansion of T regulatory cells (T reg).

Results

Our data show that the exposure of AMSCs to SF activates cells and promotes the release of immunosuppressive factors, which induce macrophage polarization of M0 into the M2-like phenotype and inhibit differentiation of monocytes into mature dendritic cells (mDCs). Only the secretome of exposed AMSCs was able to inhibit T cell proliferation and promote T reg expansion.

Conclusions

Our results suggest that the microenvironment plays a fundamental role for the development of anti-inflammatory and immunomodulatory properties of AMSCs.

Mechanisms behind the Immunoregulatory Dialogue between Mesenchymal Stem Cells and Th17 Cells

Mesenchymal stem cells (MSCs) exhibit potent immunoregulatory abilities by interacting with cells of the adaptive and innate immune system. In vitro, MSCs inhibit the differentiation of T cells into T helper 17 (Th17) cells and repress their proliferation. In vivo, the administration of MSCs to treat various experimental inflammatory and autoimmune diseases, such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and bowel disease showed promising therapeutic results. These therapeutic properties mediated by MSCs are associated with an attenuated immune response characterized by a reduced frequency of Th17 cells and the generation of regulatory T cells. In this manuscript, we review how MSC and Th17 cells interact, communicate, and exchange information through different ways such as cell-to-cell contact, secretion of soluble factors, and organelle transfer. Moreover, we discuss the consequences of this dynamic dialogue between MSC and Th17 well described by their phenotypic and functional plasticity.

The cytotoxicity of advanced glycation end products was attenuated by UCMSCs in human vaginal wall fibroblasts by inhibition of an inflammatory response and activation of PI3K/AKT/PTEN

Pelvic organ prolapse (POP) occurs when the pelvic organs (bladder, bowel or uterus) herniate into the vagina, causing incontinence, voiding, and bowel and sexual dysfunction, negatively impacting upon a woman's quality of life. Intermediate intermolecular cross-links and advanced glycation cross-links increase in prolapsed tissue. Stem cells are able to participate in tissue repair due to their ability to differentiate into multiple lineages, and thus into various types of connective tissue cells, so they therefore hold great promise for treating pelvic floor dysfunction. The current study found that advanced glycation end products (AGEs) inhibited the viability and proliferation of human vaginal wall fibroblasts (VWFs), were cytotoxic to VWFs, and also induced the apoptosis of VWFs. In contrast, umbilical cord-derived mesenchymal stem cells (UCMSCs) secreted anti-inflammation cytokines to protect against the cytotoxic effects of fibroblasts induced by AGEs and attenuated the cytotoxic effect of AGE on fibroblasts by activation of the PI3K/Akt-PTEN pathway. This study demonstrated that UCMSCs inhibited the cytotoxic effect of AGE in cells from patients with POP by inducing an anti-inflammatory reaction and activating the PI3K/AKT/PTEN signaling pathway. The current results provide important insights into use of stem cells to treat POP.

TGF-β1-Licensed Murine MSCs Show Superior Therapeutic Efficacy in Modulating Corneal Allograft Immune Rejection In Vivo

Mesenchymal stromal cells (MSCs) are a promising therapeutic option for multiple immune diseases/disorders; however, efficacy of MSC treatments can vary significantly. We present a novel licensing strategy to improve the immunosuppressive capacity of MSCs. Licensing murine MSCs with transforming growth factor-β1 (TGF-β MSCs) significantly improved their ability to modulate both the phenotype and secretome of inflammatory bone marrow-derived macrophages and significantly increased the numbers of regulatory T lymphocytes following co-culture assays. These TGF-β MSC-expanded regulatory T lymphocytes also expressed significantly higher levels of PD-L1 and CD73, indicating enhanced suppressive potential. Detailed analysis of T lymphocyte co-cultures revealed modulation of secreted factors, most notably elevated prostaglandin E2 (PGE2). Furthermore, TGF-β MSCs could significantly prolong rejection-free survival (69.2% acceptance rate compared to 21.4% for unlicensed MSC-treated recipients) in a murine corneal allograft model. Mechanistic studies revealed that (1) therapeutic efficacy of TGF-β MSCs is Smad2/3-dependent, (2) the enhanced immunosuppressive capacity of TGF-β MSCs is contact-dependent, and (3) enhanced secretion of PGE2 (via prostaglandin EP4 [E-type prostanoid 4] receptor) by TGF-β MSCs is the predominant mediator of Treg expansion and T cell activation and is associated with corneal allograft survival. Collectively, we provide compelling evidence for the use of TGF-β1 licensing as an unconventional strategy for enhancing MSC immunosuppressive capacity.

Can Stem Cells Beat COVID-19: Advancing Stem Cells and Extracellular Vesicles Toward Mainstream Medicine for Lung Injuries Associated With SARS-CoV-2 Infections

A number of medicines are currently under investigation for the treatment of COVID-19 disease including anti-viral, anti-malarial, and anti-inflammatory agents. While these treatments can improve patient's recovery and survival, these therapeutic strategies do not lead to unequivocal restoration of the lung damage inflicted by this disease. Stem cell therapies and, more recently, their secreted extracellular vesicles (EVs), are emerging as new promising treatments, which could attenuate inflammation but also regenerate the lung damage caused by COVID-19. Stem cells exert their immunomodulatory, anti-oxidant, and reparative therapeutic effects likely through their EVs, and therefore, could be beneficial, alone or in combination with other therapeutic agents, in people with COVID-19. In this review article, we outline the mechanisms of cytokine storm and lung damage caused by SARS-CoV-2 virus leading to COVID-19 disease and how mesenchymal stem cells (MSCs) and their secreted EVs can be utilized to tackle this damage by harnessing their regenerative properties, which gives them potential enhanced clinical utility compared to other investigated pharmacological treatments. There are currently 17 clinical trials evaluating the therapeutic potential of MSCs for the treatment of COVID-19, the majority of which are administered intravenously with only one clinical trial testing MSC-derived exosomes via inhalation route. While we wait for the outcomes from these trials to be reported, here we emphasize opportunities and risks associated with these therapies, as well as delineate the major roadblocks to progressing these promising curative therapies toward mainstream treatment for COVID-19.

Toll-Like Receptor 3 Activator Preconditioning Enhances Modulatory Function of Adipose‑Derived Mesenchymal Stem Cells in a Fully MHC-Mismatched Murine Model of Heterotopic Heart Transplantation

Background

Donor-specific tolerance is the ultimate goal in organ transplantation. Diverse approaches, including the use of mesenchymal stem cells (MSCs), have been investigated to induce graft tolerance. Non-stimulated MSCs showed limited regulatory functions through interaction with multiple immune-regulatory cells, such as regulatory T cells (Tregs). To augment their functions, MSCs have been preconditioned with toll-like receptor (TLR3/4) agonist in autoimmune disease models, but results were conflicting.

Material/Methods

We evaluated the immunomodulatory effects of mouse adipose-derived mesenchymal stem cells (ADSCs) preconditioned with various combinations of TLR3/4 agonist and antagonists, including polyinosinic-polycytidylic acid poly(I:C)-TLR3 agonist, lipopolysaccharide (LPS) -TLR4 agonist, and TAK242-TLR4 antagonist. In vitro and in vivo experiments including mixed lymphocyte reaction, cytokines measurement, Tregs analysis, and a fully mismatched MHC heterotopic heart transplantation in mice (BALB/c to C57BL/6) were conducted.

Results

ADSCs preconditioned with poly(I:C) showed the highest efficiency in inhibiting lymphocyte proliferation, which was correlated with the upregulation of fibrinogen-like protein 2 (FGL2), an effector molecule of Tregs. The mean survival of cardiac allografts was extended from 8 to 12 days by intravenous injection of a single dose of ADSCs preconditioned with TLR3 agonist. The proportion of Tregs in the recipient’s spleen was significantly increased by injecting the poly(I:C)-stimulated ADSCs.

Conclusions

These results show that short-term TLR3 agonist preconditioning enhances the immunomodulatory efficacy of ADSCs, which can induce the generation of Tregs and upregulate the expression of FGL2, thereby improving the outcome of patients receiving organ transplantation.

Human umbilical cord-mesenchymal stem cells: a promising strategy for corneal epithelial regeneration

Aim: As a strategy to improve the outcome of ex vivo cultivated corneal epithelial transplantation, the role of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) is investigated in promoting corneal epithelial growth and functions. Materials & methods: Human telomerase-immortalized corneal epithelial cells were characterized and its functions evaluated by scratch migration assay, cellular senescence, HLA expression and spheres formation with hUC-MSC. Results: Expression of corneal epithelial markers was influenced by the duration and method of co-culture. Indirect co-culture improved cellular migration and delayed senescence when treated after 3 and 5 days. hUC-MSC downregulated expression of HLA Class I and II in IFN-γ-stimulated human telomerase-immortalized corneal epithelial cells. Conclusion: hUC-MSC promote corneal epithelial growth and functions after treatment with hUC-MSC.

Manipulated Mesenchymal Stem Cells Applications in Neurodegenerative Diseases

Mesenchymal stem cells (MSCs) are multipotent stem cells that have multilinear differentiation and self-renewal abilities. These cells are immune-privileged as they express no or low level of class-II major histocompatibility complex (MHC-II) and other costimulatory molecules. Having neuroprotective and regenerative properties, MSCs can be used to ameliorate several intractable neurodegenerative disorders by affecting both innate and adaptive immune systems. Several manipulations like pretreating MSCs with different conditions or agents, and using molecules derived from MSCs or genetically manipulating them, are the common and practical ways that can be used to strengthen MSCs survival and potency. Improved MSCs can have significantly enhanced impacts on diseases compared to MSCs not manipulated. In this review, we describe some of the most important manipulations that have been exerted on MSCs to improve their therapeutic functions and their applications in ameliorating three prevalent neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and Huntington's disease.

Pro-Inflammatory Priming of Umbilical Cord Mesenchymal Stromal Cells Alters the Protein Cargo of Their Extracellular Vesicles

Umbilical cord mesenchymal stromal cells (UCMSCs) have shown an ability to modulate the immune system through the secretion of paracrine mediators, such as extracellular vesicles (EVs). However, the culture conditions that UCMSCs are grown in can alter their secretome and thereby affect their immunomodulatory potential. UCMSCs are commonly cultured at 21% O₂ in vitro, but recent research is exploring their growth at lower oxygen conditions to emulate circulating oxygen levels in vivo. Additionally, a pro-inflammatory culture environment is known to enhance UCMSC anti-inflammatory potential. Therefore, this paper examined EVs from UCMSCs grown in normal oxygen (21% O₂), low oxygen (5% O₂) and pro-inflammatory conditions to see the impact of culture conditions on the EV profile. EVs were isolated from UCMSC conditioned media and characterised based on size, morphology and surface marker expression. EV protein cargo was analysed using a proximity-based extension assay. Results showed that EVs had a similar size and morphology. Differences were found in EV protein cargo, with pro-inflammatory primed EVs showing an increase in proteins associated with chemotaxis and angiogenesis. This showed that the UCMSC culture environment could alter the EV protein profile and might have downstream implications for their functions in immunomodulation.

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.

Improved therapeutics of modified mesenchymal stem cells: an update

Background

Mesenchymal stromal cells (MSCs) have attracted intense interest due to their powerful intrinsic properties of self-regeneration, immunomodulation and multi-potency, as well as being readily available and easy to isolate and culture. Notwithstanding, MSC based therapy suffers reduced efficacy due to several challenges which include unfavorable microenvironmental factors in vitro and in vivo.

Body

In the quest to circumvent these challenges, several modification techniques have been applied to the naïve MSC to improve its inherent therapeutic properties. These modification approaches can be broadly divided into two groups to include genetic modification and preconditioning modification (using drugs, growth factors and other molecules). This field has witnessed great progress and continues to gather interest and novelty. We review these innovative approaches in not only maintaining, but also enhancing the inherent biological activities and therapeutics of MSCs with respect to migration, homing to target site, adhesion, survival and reduced premature senescence. We discuss the application of the improved modified MSC in some selected human diseases. Possible ways of yet better enhancing the therapeutic outcome and overcoming challenges of MSC modification in the future are also elaborated.

Conclusion

The importance of prosurvival and promigratory abilities of MSCs in their therapeutic applications can never be overemphasized. These abilities are maintained and even further enhanced via MSC modifications against the inhospitable microenvironment during culture and transplantation. This is a turning point in MSC-based therapy with promising preclinical studies and higher future prospect.

Preconditioning of canine adipose tissue-derived mesenchymal stem cells with deferoxamine potentiates anti-inflammatory effects by directing/reprogramming M2 macrophage polarization

Preconditioning with hypoxia or hypoxia-mimetic agents has been tried with mesenchymal stem cells (MSCs) to improve the secretion of anti-inflammatory factors. These preconditioning procedures upregulate hypoxia inducible factor (HIF) 1-alpha leading to the transcription of HIF-dependent tissue protective and anti-inflammatory genes. Due to the limited number of studies exploring the activity of deferoxamine (DFO)-a hypoxia-mimetic agent-in MSCs, we aimed to determine whether DFO can enhance the secretion of anti-inflammatory substances in canine adipose tissue-derived (cAT)-MSCs. Furthermore, we investigated whether this activity of DFO could affect macrophage polarization and activate anti-inflammatory reactions. cAT-MSCs preconditioned with DFO exhibited enhanced secretion of anti-inflammatory factors such as prostaglandin E2 and tumor necrosis factor-α-stimulated gene-6. To evaluate the interaction between DFO preconditioned cAT-MSCs and macrophages, RAW 264.7 cells were co-cultured with cAT-MSCs using the Transwell system, and changes in the expression of factors related to macrophage polarization were analyzed using the quantitative real-time PCR and western blot assays. When RAW 264.7 cells were co-cultured with DFO preconditioned cAT-MSCs, the expression of M1 and M2 markers decreased and increased, respectively, compared to co-culturing with non-preconditioned cAT-MSCs. Thus, cAT-MSCs preconditioned with DFO can more effectively direct and reprogram macrophage polarization into the M2 phase, an anti-inflammatory state.

Haemin pre-treatment augments the cardiac protection of mesenchymal stem cells by inhibiting mitochondrial fission and improving survival

The cardiac protection of mesenchymal stem cell (MSC) transplantation for myocardial infarction (MI) is largely hampered by low cell survival. Haem oxygenase 1 (HO‐1) plays a critical role in regulation of cell survival under many stress conditions. This study aimed to investigate whether pre‐treatment with haemin, a potent HO‐1 inducer, would promote the survival of MSCs under serum deprivation and hypoxia (SD/H) and enhance the cardioprotective effects of MSCs in MI. Bone marrow (BM)‐MSCs were pretreated with or without haemin and then exposed to SD/H. The mitochondrial morphology of MSCs was determined by MitoTracker staining. BM‐MSCs and haemin‐pretreated BM‐MSCs were transplanted into the peri‐infarct region in MI mice. SD/H induced mitochondrial fragmentation, as shown by increased mitochondrial fission and apoptosis of BM‐MSCs. Pre‐treatment with haemin greatly inhibited SD/H‐induced mitochondrial fragmentation and apoptosis of BM‐MSCs. These effects were partially abrogated by knocking down HO‐1. At 4 weeks after transplantation, compared with BM‐MSCs, haemin‐pretreated BM‐MSCs had greatly improved the heart function of mice with MI. These cardioprotective effects were associated with increased cell survival, decreased cardiomyocytes apoptosis and enhanced angiogenesis. Collectively, our study identifies haemin as a regulator of MSC survival and suggests a novel strategy for improving MSC‐based therapy for MI.

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.

Exosomes derived from pro-inflammatory bone marrow-derived mesenchymal stem cells reduce inflammation and myocardial injury via mediating macrophage polarization

Exosomes are served as substitutes for stem cell therapy, playing important roles in mediating heart repair during myocardial infarction injury. Evidence have indicated that lipopolysaccharide (LPS) pre-conditioning bone marrow-derived mesenchymal stem cells (BMSCs) and their secreted exosomes promote macrophage polarization and tissue repair in several inflammation diseases; however, it has not been fully elucidated in myocardial infarction (MI). This study aimed to investigate whether LPS-primed BMSC-derived exosomes could mediate inflammation and myocardial injury via macrophage polarization after MI. Here, we found that exosomes derived from BMSCs, in both Exo and L-Exo groups, increased M2 macrophage polarization and decreased M1 macrophage polarization under LPS stimulation, which strongly depressed LPS-dependent NF-κB signalling pathway and partly activated the AKT1/AKT2 signalling pathway. Compared with Exo, L-Exo had superior therapeutic effects on polarizing M2 macrophage in vitro and attenuated the post-infarction inflammation and cardiomyocyte apoptosis by mediating macrophage polarization in mice MI model. Consequently, we have confidence in the perspective that low concentration of LPS pre-conditioning BMSC-derived exosomes may develop into a promising cell-free treatment strategy for clinical treatment of MI.

Reparative and Regenerative Effects of Mesenchymal Stromal Cells-Promising Potential for Kidney Transplantation?

Mesenchymal stromal cells (MSCs) possess reparative, regenerative and immunomodulatory properties. The current literature suggests that MSCs could improve kidney transplant outcome via immunomodulation. In many clinical domains, research has also focussed on the regenerative and reparative effects of therapies with MSCs. However, in the field of transplantation, data on this subject remain scarce. This review provides an overview of what is known about the regenerative and reparative effects of MSCs in various fields ranging from wound care to fracture healing and also examines the potential of these promising MSC properties to improve the outcome of kidney transplantations.

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

BACKGROUND

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

OBJECTIVE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Adipose Mesenchymal Extracellular Vesicles as Alpha-1-Antitrypsin Physiological Delivery Systems for Lung Regeneration

Accumulating evidence shows that Mesenchymal Stem/Stromal Cells (MSCs) exert their therapeutic effects by the release of secretome, made of both soluble proteins and nano/microstructured extracellular vesicles (EVs). In this work, for the first time, we proved by a proteomic investigation that adipose-derived (AD)-MSC-secretome contains alpha-1-antitrypsin (AAT), the main elastase inhibitor in the lung, 72 other proteins involved in protease/antiprotease balance, and 46 proteins involved in the response to bacteria. By secretome fractionation, we proved that AAT is present both in the soluble fraction of secretome and aggregated and/or adsorbed on the surface of EVs, that can act as natural carriers promoting AAT in vivo stability and activity. To modulate secretome composition, AD-MSCs were cultured in different stimulating conditions, such as serum starvation or chemicals (IL-1β and/or dexamethasone) and the expression of the gene encoding for AAT was increased. By testing in vitro the anti-elastase activity of MSC-secretome, a dose-dependent effect was observed; chemical stimulation of AD-MSCs did not increase their secretome anti-elastase activity. Finally, MSC-secretome showed anti-bacterial activity on Gram-negative bacteria, especially for Klebsiellapneumoniae. These preliminary results, in addition to the already demonstrated immunomodulation, pave the way for the use of MSC-secretome in the treatment of AAT-deficiency lung diseases.

Mesenchymal Stromal Cells Are More Effective Than Their Extracellular Vesicles at Reducing Lung Injury Regardless of Acute Respiratory Distress Syndrome Etiology

Although mesenchymal stromal cells (MSCs) have demonstrated beneficial effects on experimental acute respiratory distress syndrome (ARDS), preconditioning may be required to potentiate their therapeutic effects. Additionally, administration of cell-free products, such as extracellular vesicles (EVs) obtained from MSC-conditioned media, might be as effective as MSCs. In this study, we comparatively evaluated the effects of MSCs, preconditioned or not with serum collected from mice with pulmonary or extrapulmonary ARDS (ARDSp and ARDSexp, respectively), and the EVs derived from these cells on lung inflammation and remodeling in ARDSp and ARDSexp mice. Administration of MSCs (preconditioned or not), but not their EVs, reduced static lung elastance, interstitial edema, and collagen fiber content in both ARDSp and ARDSexp. Although MSCs and EVs reduced alveolar collapse and neutrophil cell counts in lung tissue, therapeutic responses were superior in mice receiving MSCs, regardless of preconditioning. Despite higher total cell, macrophage, and neutrophil counts in bronchoalveolar lavage fluid in ARDSp than ARDSexp, MSCs and EVs (preconditioned or not) led to a similar decrease. In ARDSp, both MSCs and EVs, regardless of preconditioning, reduced levels of tumor necrosis factor- (TNF-) α, interleukin-6, keratinocyte chemoattractant (KC), vascular endothelial growth factor (VEGF), and transforming growth factor- (TGF-) β in lung homogenates. In ARDSexp, TNF-α, interleukin-6, and KC levels were reduced by MSCs and EVs, preconditioned or not; only MSCs reduced VEGF levels, while TGF-β levels were similarly increased in ARDSexp treated either with saline, MSCs, or EVs, regardless of preconditioning. In conclusion, MSCs yielded greater overall improvement in ARDS in comparison to EVs derived from the same number of cells and regardless of the preconditioning status. However, the effects of MSCs and EVs differed according to ARDS etiology.

Membrane TLR9 Positive Neutrophil Mediated MPLA Protects Against Fatal Bacterial Sepsis

Sepsis is a major cause of patient mortality and morbidity from bacterial infections. Although neutrophils are known to be important in the development of sepsis, how distinctive neutrophil subtypes regulate inflammatory processes involved in septicemia remains unclear. Preconditioning protects organisms against subsequent higher-dose exposures to the same, or even different, stimuli. Several studies have reported various effects of preconditioning on immune cells. However, the detailed mechanisms underlying neutrophil-mediated protection through preconditioning in sepsis remain unknown.

Methods: Flow cytometry was conducted to sort the mice peritoneal lavage cells and the blood samples from patients with sepsis. Western blotting and ELISA were carried out to elucidate the expression of TLR9 signal transduction pathway proteins. Histological analysis was used to assess the effect of InP on intestine and liver structure in tlr9^-/- and cav-1^-/- mice. Fluorescence microscopy, Co-IP, and FRET were carried out to determine the association of TLR9 with Cav-1.

Results: We show that membrane toll-like receptor-9 positive (mTLR9⁺) neutrophils exert a protective effect against fatal bacterial infections through the process of inflammatory preconditioning (InP). InP, which occurs in the setting of a low-dose bacterial challenge, active ingredient is Monophosphoryl lipid A (MPLA), triggers the membrane translocation of TLR9 from the neutrophil cytosol, where it binds to Cav-1. Our findings showed that InP enables TLR9 to facilitate MyD88-mediated TRAF3 and IRF3 signal transduction. Depletion of either TLR9 or Cav-1 largely eliminates the neutrophil-mediated InP effect in sepsis models in vitro and in vivo. Further, examination of clinical samples from patients with sepsis showed that clinical outcomes and likelihood of recovery are closely correlated with mTLR9 and Cav-1 expression in circulating neutrophils.

Conclusion: These results demonstrate that the TLR9-Cav-1 axis is a critical signaling pathway involved in the regulation of neutrophil-dependent MPLA mediated InP, and the presence of mTLR9⁺ neutrophils could be an attractive indicator of clinical outcomes in bacterial sepsis that could be further explored as a potential therapeutic target.