Overexpression of COX-2 but not indoleamine 2,3-dioxygenase-1 enhances the immunosuppressive ability of human umbilical cord-derived mesenchymal stem cells

Persistent tailoring of MSC activation through genetic priming

Mesenchymal stem/stromal cells (MSCs) are an attractive platform for cell therapy due to their safety profile and unique ability to secrete broad arrays of immunomodulatory and regenerative molecules. Yet, MSCs are well known to require preconditioning or priming to boost their therapeutic efficacy. Current priming methods offer limited control over MSC activation, yield transient effects, and often induce expression of pro-inflammatory effectors that can potentiate immunogenicity. Here, we describe a 'genetic priming' method that can both selectively and sustainably boost MSC potency via the controlled expression of the inflammatory-stimulus-responsive transcription factor IRF1 (interferon response factor 1). MSCs engineered to hyper-express IRF1 recapitulate many core responses that are accessed by biochemical priming using the proinflammatory cytokine interferon-γ (IFNγ). This includes the upregulation of anti-inflammatory effector molecules and the potentiation of MSC capacities to suppress T cell activation. However, we show that IRF1-mediated genetic priming is much more persistent than biochemical priming and can circumvent IFNγ-dependent expression of immunogenic MHC class II molecules. Together, the ability to sustainably activate and selectively tailor MSC priming responses creates the possibility of programming MSC activation more comprehensively for therapeutic applications.

Human macrophage migration inhibitory factor potentiates mesenchymal stromal cell efficacy in a clinically relevant model of allergic asthma

Current asthma therapies focus on reducing symptoms but fail to restore existing structural damage. Mesenchymal stromal cell (MSC) administration can ameliorate airway inflammation and reverse airway remodeling. However, differences in patient disease microenvironments seem to influence MSC therapeutic effects. A polymorphic CATT tetranucleotide repeat at position 794 of the human macrophage migration inhibitory factor (hMIF) gene has been associated with increased susceptibility to and severity of asthma. We investigated the efficacy of human MSCs in high- vs. low-hMIF environments and the impact of MIF pre-licensing of MSCs using humanized MIF mice in a clinically relevant house dust mite (HDM) model of allergic asthma. MSCs significantly attenuated airway inflammation and airway remodeling in high-MIF-expressing CATT7 mice but not in CATT5 or wild-type littermates. Differences in efficacy were correlated with increased MSC retention in the lungs of CATT7 mice. MIF licensing potentiated MSC anti-inflammatory effects at a previously ineffective dose. Mechanistically, MIF binding to CD74 expressed on MSCs leads to upregulation of cyclooxygenase 2 (COX-2) expression. Blockade of CD74 or COX-2 function in MSCs prior to administration attenuated the efficacy of MIF-licensed MSCs in vivo. These findings suggest that MSC administration may be more efficacious in severe asthma patients with high MIF genotypes (CATT6/7/8).

PGE2 Produced by Exogenous MSCs Promotes Immunoregulation in ARDS Induced by Highly Pathogenic Influenza A through Activation of the Wnt-β-Catenin Signaling Pathway

Acute respiratory distress syndrome is an acute respiratory failure caused by cytokine storms; highly pathogenic influenza A virus infection can induce cytokine storms. The innate immune response is vital in this cytokine storm, acting by activating the transcription factor NF-κB. Tissue injury releases a danger-associated molecular pattern that provides positive feedback for NF-κB activation. Exogenous mesenchymal stem cells can also modulate immune responses by producing potent immunosuppressive substances, such as prostaglandin E2. Prostaglandin E2 is a critical mediator that regulates various physiological and pathological processes through autocrine or paracrine mechanisms. Activation of prostaglandin E2 results in the accumulation of unphosphorylated β-catenin in the cytoplasm, which subsequently reaches the nucleus to inhibit the transcription factor NF-κB. The inhibition of NF-κB by β-catenin is a mechanism that reduces inflammation.

PPARβ/δ-Interfering Peptide Enhanced Mesenchymal Stromal Cell Immunoregulatory Properties

Background

Mesenchymal stem/stromal cells (MSCs) have been widely used for their therapeutic properties in many clinical applications including osteoarthritis. Despite promising preclinical results showing the ability of MSC to reduce the clinical severity of osteoarthritis (OA) in experimental animal models, the benefits of intra-articular injection of MSC in OA patients are limited to the short term. In this regard, it is anticipated that improving the properties of MSC may collectively enhance their long-term beneficial effects on OA.

Methods and Results

Recently, we have shown that PPARβ/δ inhibition using a commercially available antagonist in murine MSC increases their immunoregulatory potential in vitro as well as their therapeutic potential in an experimental murine arthritis model. Here, we relied on an innovative strategy to inhibit PPARβ/δ:NF-κB TF65 subunit interaction in human MSC by designing and synthesizing an interfering peptide, referred to PP11. Through RT-qPCR experiments, we evidenced that the newly synthesized PP11 peptide reduced the expression level of PDK4, a PPARβ/δ target gene, but did not modify the expression levels of ACOX1 and CPT1A, PPARα target genes, and FABP4, a PPARγ target gene compared with untreated human MSC. Moreover, we showed that human MSCs pretreated with PP11 exhibit a significantly higher capacity to inhibit the proliferation of activated PBMC and to decrease the frequency of M1-like macrophages.

Conclusions

We designed and synthesized an interfering peptide that potently and specifically blocks PPARβ/δ activity with concomitant enhancement of MSC immunoregulatory properties.

Pimecrolimus interferes the therapeutic efficacy of human mesenchymal stem cells in atopic dermatitis by regulating NFAT-COX2 signaling

Background

Human mesenchymal stem cells (hMSCs) therapy has recently been considered a promising treatment for atopic dermatitis (AD) due to their immunomodulation and tissue regeneration ability. In our previous studies, we demonstrated that hMSCs alleviate allergic inflammation in murine AD model by inhibiting the activation of mast cells and B cells. Also our phase I/IIa clinical trial showed clinical efficacy and safety of hMSCs in moderate-to-severe adult AD patients. However, hMSCs therapy against atopic dermatitis have had poor results in clinical field. Therefore, we investigated the reason behind this result. We hypothesized that drug–cell interaction could interfere with the therapeutic efficacy of stem cells, and investigated whether coadministration with pimecrolimus, one of the topical calcineurin inhibitors, could influence the therapeutic potential of human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) in AD.

Methods

hUCB-MSCs were subcutaneously injected to AD-induced mice with or without pimecrolimus topical application. To examine whether pimecrolimus influenced the immunomodulatory activity of hUCB-MSCs, hUCB-MSCs were treated with pimecrolimus.

Results

Pimecrolimus disturbed the therapeutic effect of hUCB-MSCs when they were co-administered in murine AD model. Moreover, the inhibitory functions of hUCB-MSCs against type 2 helper T (Th2) cell differentiation and mast cell activation were also deteriorated by pimecrolimus treatment. Interestingly, we found that pimecrolimus decreased the production of PGE₂, one of the most critical immunomodulatory factors in hUCB-MSCs. And we demonstrated that pimecrolimus downregulated COX2-PGE₂ axis by inhibiting nuclear translocation of NFAT3.

Conclusions

Coadministration of pimecrolimus with hMSCs could interfere with the therapeutic efficacy of hMSCs in atopic dermatitis, and this is the first study that figured out the interaction of hMSCs with other drugs in cell therapy of atopic dermatitis. Therefore, this study might give rise to improvement of the clinical application of hMSCs therapy and facilitate the widespread application of hMSCs in clinical field.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02547-8.

Mesenchymal Stromal Cells in Viral Infections: Implications for COVID-19

Mesenchymal stromal cells (MSCs) constitute a heterogeneous population of stromal cells with immunomodulatory and regenerative properties that support their therapeutic use. MSCs isolated from many tissue sources replicate vigorously in vitro and maintain their main biological properties allowing their widespread clinical application. To date, most MSC-based preclinical and clinical trials targeted immune-mediated and inflammatory diseases. Nevertheless, MSCs have antiviral properties and have been used in the treatment of various viral infections in the last years. Here, we revised in detail the biological properties of MSCs and their preclinical and clinical applications in viral diseases, including the disease caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection (COVID-19). Notably, rapidly increasing numbers of MSC-based therapies for COVID-19 have recently been reported. MSCs are theoretically capable of reducing inflammation and promote lung regeneration in severe COVID-19 patients. We critically discuss the rationale, advantages and disadvantages of MSC-based therapies for viral infections and also specifically for COVID-19 and point out some directions in this field. Finally, we argue that MSC-based therapy may be a promising therapeutic strategy for severe COVID-19 and other emergent respiratory tract viral infections, beyond the viral infection diseases in which MSCs have already been clinically applied.

Agitation in a Microcarrier-based Spinner Flask Bioreactor Modulates Homeostasis of Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSCs) are well known in cell therapy due to their secretion of trophic factors, multipotent differentiation potential, and ability for self-renewal. As a result, the number of clinical trials has been steadily increasing over the last decade highlighting the need for in vitro systems capable of producing large quantities of cells to meet growing demands. However, hMSCs are highly sensitive to microenvironment conditions, including shear stress caused by dynamic bioreactor systems, and can lead to alteration of cellular homeostasis. In this study, hMSCs were expanded on microcarriers within a 125 mL spinner flask bioreactor system. Our results demonstrate a three-fold expansion over seven days. Furthermore, our results show that culturing hMSCs in the microcarrier-based suspension bioreactor (compared to static planar culture) results in smaller cell size and higher levels of reactive oxidative species (ROS) and ROS regulator Sirtuin-3, which have implications on the nicotinamide adenine dinucleotide metabolic pathway and metabolic homeostasis. In addition, hMSCs in the bioreactor showed the increased Prostaglandin E₂ secretion as well as reduced the Indoleamine-pyrrole 2,3-dioxygenase secretion upon stimulus with interferon gamma. The results of this study provide understanding of potential hMSC physiology alterations impacted by bioreactor microenvironment during scalable production of hMSCs for biomanufacturing and clinical trials.

Harnessing Dental Stem Cell Immunoregulation Using Cell-Laden Biomaterials

Successful tissue engineering therapies rely on the appropriate selection of the cell source, biomaterial, and regulatory factors. To be applied in a wide range of clinical applications, the ideal cell source needs to be easily accessible and abundant. Human orofacial tissues and teeth harbor several populations of mesenchymal stem cells (MSCs) with self-renewal and multilineage differentiation capabilities. The ease of access, relative abundance, and minimally invasive isolation procedures needed to harvest most types of the dental-derived MSCs render them a promising cell source for tissue engineering applications. A growing body of evidence has reported the profound immunoregulatory potential of dental-derived MSCs as compared with their bone marrow counterparts. Biomaterials can act as a physical barrier protecting the MSCs from the invasion of the immune system by hindering penetration of proinflammatory cells/cytokines, leading to higher viability of the encapsulated MSCs and improved tissue regeneration. Besides their protective capabilities, biomaterials can actively contribute to the immunoregulatory potential of the MSCs through their physical and chemical properties, including porosity and elasticity. However, despite recent advancement, the therapeutic capability of biomaterials to regulate the MSC-host immune system crosstalk and the mechanism underlying this immunoregulation has been poorly understood. It has been reported that biomaterials can regulate the viability and determine the fate of the encapsulated MSCs through modulation of the NF-kB pathway and the caspase-3 and caspase-8 proapoptotic cascades. Additionally, the physiomechanical properties of the encapsulating biomaterial have been shown to modulate clustering of TNF-α receptors on the encapsulated MSCs while regulating the production of anti-inflammatory factors such as indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE₂) through activation of the P38 MAPK pathway. In the current review, we sought to provide a thorough overview of the immunomodulatory functions of dental-derived MSCs and the role of biomaterials in their interplay with the host immune system.

Effects of Placenta-Derived Mesenchymal Stem Cells on the Particulate Matter-Induced Damages in Human Middle Ear Epithelial Cells

This study was aimed at investigating the effects of placenta-derived mesenchymal stem cells (PL-MSCs) on particulate matter- (PM-) exposed human middle ear epithelial cells (HMEECs). HMEECs were treated with 300 μg/ml PM for 24 hours. The PL-MSCs were cocultured with PM-treated HMEECs. Cells were harvested on days 0, 1, and 4, and the expression of the inflammatory genes TNFα, COX2, IL1β, IL6, and MUC5B in HMEECs and anti-inflammatory genes PTGES, TGFβ, and VEGF in PL-MSCs was examined by qRT-PCR. The culture media were collected to measure the secreted PGE2 level using an enzyme-linked immunosorbent assay. The mRNA expression of TNFα, COX2, IL1β, IL6, and MUC5B in HMEECs increased following PM treatment. PM-treated HMEECs cocultured with PL-MSCs showed alleviated inflammatory reactions represented by lower mRNA expression levels of MUC5B, TNFα, IL1β, and IL6 compared to monocultured PM-treated HMEECs. The mRNA expression levels of PGE2, TGFβ, and VEGF were elevated in cocultured PL-MSCs compared to those of control PL-MSCs. The medium of PM-treated HMEECs cocultured with PL-MSCs exhibited increased PGE2 levels. The increased inflammatory response in PM-treated HMEECs was reversed using PL-MSCs. The PGE2, TGFβ, and VEGF were the mediators of the anti-inflammatory effects of PL-MSCs.

Molecular Profiles of Cell-to-Cell Variation in the Regenerative Potential of Mesenchymal Stromal Cells

Cell-to-cell variation in the regenerative potential of mesenchymal stromal cells (MSCs) impedes the translation of MSC therapies into clinical practice. Cellular heterogeneity is ubiquitous across MSC cultures from different species and tissues. This review highlights advances to elucidate molecular profiles that identify cell subsets with specific regenerative properties in heterogeneous MSC cultures. Cell surface markers and global signatures are presented for proliferation and differentiation potential, as well as immunomodulation and trophic properties. Key knowledge gaps are discussed as potential areas of future research. Molecular profiles of MSC heterogeneity have the potential to enable unprecedented control over the regenerative potential of MSC therapies through the discovery of new molecular targets and as quality attributes to develop robust and reproducible biomanufacturing processes. These advances would have a positive impact on the nascent field of MSC therapeutics by accelerating the development of therapies with more consistent and effective treatment outcomes.

Valproic acid enforces the priming effect of sphingosine-1 phosphate on human mesenchymal stem cells

Engraftment and homing of mesenchymal stem cells (MSCs) are modulated by priming factors including the bioactive lipid sphingosine-1-phosphate (S1P), by stimulating CXCR4 receptor signaling cascades. However, limited in vivo efficacy and the remaining priming molecules prior to administration of MSCs can provoke concerns regarding the efficiency and safety of MSC priming. Here, we showed that valproic acid (VPA), a histone deacetylase inhibitor, enforced the priming effect of S1P at a low dosage for human umbilical cord-derived MSCs (UC-MSCs). A DNA-methylation inhibitor, 5-azacytidine (5-Aza), and VPA increased the expression of CXCR4 in UC-MSCs. In particular, UC-MSCs primed with a suboptimal dose (50 nM) of S1P in combination with 0.5 mM VPA (VPA+S1P priming), but not 1 µM 5-Aza, significantly improved the migration activity in response to stromal cell-derived factor 1 (SDF-1) concomitant with the activation of both MAPKp42/44 and AKT signaling cascades. Both epigenetic regulatory compounds had little influence on cell surface marker phenotypes and the multi-potency of UC-MSCs. In contrast, VPA+S1P priming of UC-MSCs potentiated the proliferation, colony forming unit-fibroblast, and anti-inflammatory activities, which were severely inhibited in the case of 5-Aza treatment. Accordingly, the VPA+S1P-primed UC-MSCs exhibited upregulation of a subset of genes related to stem cell migration and anti-inflammation response. Thus, the present study demonstrated that VPA enables MSC priming with S1P at a low dosage by enhancing their migration and other therapeutic beneficial activities. This priming strategy for MSCs may provide a more efficient and safe application of MSCs for treating a variety of intractable disorders.

Bioactive molecules derived from umbilical cord mesenchymal stem cells

Umbilical cord mesenchymal stem cells (UCMSCs) retain their intrinsic stem cell potential while at the same time displaying high proliferation rates, powerful differentiation capacity, and low immunogenicity. They can also secrete multiple bioactive molecules that exert specific physiological functions. Thus, UCMSCs represent excellent candidates for cell therapy in regenerative medicine and tissue engineering. Abundant preclinical research on different disease models has shown that UCMSCs can accelerate wound or nerve damage recovery and suppress tumor progression. In fact, UCMSCs are thought to possess a higher therapeutic potential than MSCs derived from other tissues. Increasing evidence suggests that the mechanism underlying UCSMCs efficacy depends mostly on cell secretions, in contrast to the early paradigm of cell replacement and differentiation. In this review, we discuss UCMSCs biological characteristics, their secretome-based therapeutic mechanism, and potential applications.