Poly(I:C) Enhances Mesenchymal Stem Cell Control of Myeloid Cells From COVID-19 Patients

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

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

Activation of Toll-like receptor 2 promotes mesenchymal stem/stromal cell-mediated immunoregulation and angiostasis through AKR1C1

Background: Mesenchymal stem/stromal cells (MSCs) maintain tissue homeostasis in response to microenvironmental perturbations. Toll-like receptors (TLRs) are key sensors for exogenous and endogenous signals produced during injury. In this study, we aimed to investigate whether TLRs affect the homeostatic functions of MSCs after injury. Methods: We examined the expression of TLR2, TLR3 and TLR4 in MSCs, and analyzed the functional significance of TLR2 activation using single-cell RNA sequencing. Additionally, we investigated the effects and mechanisms of TLR2 and its downstream activation in MSCs on the MSCs themselves, on monocytes/macrophages, and in a mouse model of sterile injury-induced inflammatory corneal angiogenesis. Results: MSCs expressed TLR2, which was upregulated by monocytes/macrophages. Activation of TLR2 in MSCs promoted their immunoregulatory and angiostatic functions in monocytes/macrophages and in mice with inflammatory corneal angiogenesis, whereas TLR2 inhibition attenuated these functions. Single-cell RNA sequencing revealed AKR1C1, a gene encoding aldo-keto reductase family 1 member C1, as the most significantly inducible gene in MSCs upon TLR2 stimulation, though its stimulation did not affect cell compositions. AKR1C1 protected MSCs against ferroptosis, increased secretion of anti-inflammatory cytokines, and enhanced their ability to drive monocytes/macrophages towards immunoregulatory phenotypes, leading to the amelioration of inflammatory corneal neovascularization in mice. Conclusion: Our findings suggest that activation of TLR2-AKR1C1 signaling in MSCs serves as an important pathway for the survival and homeostatic activities of MSCs during injury.

Key quality parameter comparison of mesenchymal stem cell product cryopreserved in different cryopreservation solutions for clinical applications

Introduction

Cryopreservation is a critical process of cell products for achieving a commercial viability through wide scale adoption. By preserving cells in a lower temperature, cryopreservation enables a product to be off-the-shelf and ready for infusion. An optimized cryopreservation strategy can maintain the viability, phenotype, and potency of thawed mesenchymal stromal/stem cells (MSCs) while being regulatory compliant. We compared three clinical-ready formulations with one research cryopreservation solutions and evaluated key quality parameters of post thawed MSCs.

Method and result

MSCs were cryopreserved at 3, 6, and 9 million cells/mL (M/mL) in four different cryopreservation solutions: NutriFreez (10% dimethyl sulfoxide [DMSO]), Plasmalyte A (PLA)/5% human albumin (HA)/10% DMSO (PHD10), CryoStor CS5 (5% DMSO), and CryoStor CS10 (10% DMSO). To establish post thaw viability, cells were evaluated with no dilution of DMSO (from 3 M/mL), 1:1 dilution (from 6 M/mL), or 1:2 dilution (from 9 M/mL) with PLA/5% HA, to achieve uniform concentration at 3 M/mL. Cell viability was measured at 0-, 2-, 4-, and 6-h post thaw with Trypan blue exclusion and Annexin V/PI staining. Dilution (1:2) of final cell products from 9M/mL resulted in an improvement of cell viability over 6 h but showed a trend of decreased recovery. MSCs cryopreserved in solutions with 10% DMSO displayed comparable viabilities and recoveries up to 6 h after thawing, whereas a decreasing trend was noted in cell viability and recovery with CS5. Cells from all groups exhibited surface marker characteristics of MSCs. We further evaluated cell proliferation after 6-day recovery in culture. While cells cryopreserved in NutriFreez and PHD10 presented similar cell growth post thaw, MSCs cryopreserved in CS5 and CS10 at 3 M/mL and 6M/mL showed 10-fold less proliferative capacity. No significant differences were observed between MSCs cryopreserved in NutriFreez and PHD10 in their potency to inhibit T cell proliferation and improve monocytic phagocytosis.

Conclusion

MSCs can be cryopreserved up to 9 M/mL without losing notable viability and recovery, while exhibiting comparable post thaw potency with NutriFreez and PHD10. These results highlight the importance of key parameter testing for selecting the optimal cryopreservation solution for MSC-based therapy.

Mesenchymal stem cells induce dynamic immunomodulation of airway and systemic immune cells in vivo but do not improve survival for mice with H1N1 virus-induced acute lung injury

Introduction: Influenza A virus (IAV)-induced acute lung injury (ALI) is characterized by pronounced proinflammatory activation and respiratory lung dysfunction. In this study, we performed deep immune profiling on airway and circulating immune cells to examine the effect of immunomodulation and therapeutic outcomes of mesenchymal stem cells (MSCs) therapy in mice with IAV-induced ALI. Methods: Animals were inoculated intranasally with H1N1 IAV, followed by intravenous administration of vehicle, or human clinical-grade, bone marrow-derived MSCs 24-h later, and monitored for six days to evaluate the survival. In another set of animals, bronchoalveolar lavage (BAL) fluid and whole blood were collected three days after infection for flow or mass cytometry (CyTOF) immune profiling analysis. Results: Immune cell population and phenotypic shifts in blood were mapped by CyTOF. Increases were observed in granulocytes and myeloid-derived cells in blood from vehicle-treated animals. While MSC treatment accentuated changes in these populations, naïve B, antibody-secreting B cells, and T cells were decreased in MSC-treated animals at day 3. Compared to sham animals, IAV infection induced a significant 5.5-fold increase in BAL total cell counts, including CD4⁺ and CD8⁺ T cells, CD19⁺ B cells, CD11b + Ly6G + neutrophils, and CD11b + Ly6C + monocytes. MSC treatment significantly decreased BAL total cell counts in IAV-infected mice, specifically the number of infiltrating CD4⁺ T cells and CD11b + Ly6G + neutrophils. In contrast, there were increases in CD8⁺ T cells, B cells, and monocytes in the alveolar space in MSC-treated animals. Phenotypic immune cell profiling of blood and BAL revealed a significantly higher proportion of the monocyte population with the M2 phenotype (CD206) in MSC-treated animals; however, this failed to confer protective effects in the survival of infected mice or reduce viral titer in the lung. Further investigation revealed that MSCs were susceptible to IAV infection, leading to increased cell death and potentially affecting their efficacy. Conclusion: These findings provided in vivo evidence that MSCs promote the selective recruitment of immune cells to the site of infection during IAV infection, with reductions in proinflammatory phenotypes. However, MSCs offered no survival benefit in IAV-infected animals, possibly due to MSCs' H1N1 IAV susceptibility and subsequent cell death.

Interleukin-18-primed human umbilical cord-mesenchymal stem cells achieve superior therapeutic efficacy for severe viral pneumonia via enhancing T-cell immunosuppression

Coronavirus disease 2019 (COVID-19) treatments are still urgently needed for critically and severely ill patients. Human umbilical cord-mesenchymal stem cells (hUC-MSCs) infusion has therapeutic benefits in COVID-19 patients; however, uncertain therapeutic efficacy has been reported in severe patients. In this study, we selected an appropriate cytokine, IL-18, based on the special cytokine expression profile in severe pneumonia of mice induced by H1N1virus to prime hUC-MSCs in vitro and improve the therapeutic effect of hUC-MSCs in vivo. In vitro, we demonstrated that IL-18-primed hUC-MSCs (IL18-hUCMSC) have higher proliferative ability than non-primed hUC-MSCs (hUCMSCcon). In addition, VCAM-1, MMP-1, TGF-β1, and some chemokines (CCL2 and CXCL12 cytokines) are more highly expressed in IL18-hUCMSCs. We found that IL18-hUCMSC significantly enhanced the immunosuppressive effect on CD3⁺ T-cells. In vivo, we demonstrated that IL18-hUCMSC infusion could reduce the body weight loss caused by a viral infection and significantly improve the survival rate. Of note, IL18-hUCMSC can also significantly attenuate certain clinical symptoms, including reduced activity, ruffled fur, hunched backs, and lung injuries. Pathologically, IL18-hUCMSC transplantation significantly enhanced the inhibition of inflammation, viral load, fibrosis, and cell apoptosis in acute lung injuries. Notably, IL18-hUCMSC treatment has a superior inhibitory effect on T-cell exudation and proinflammatory cytokine secretion in bronchoalveolar lavage fluid (BALF). Altogether, IL-18 is a promising cytokine that can prime hUC-MSCs to improve the efficacy of precision therapy against viral-induced pneumonia, such as COVID-19.

A role for Toll-like receptor 3 in lung vascular remodeling associated with SARS-CoV-2 infection

Cardiovascular sequelae of severe acute respiratory syndrome (SARS) coronavirus-2 (CoV-2) disease 2019 (COVID-19) contribute to the complications of the disease. One potential complication is lung vascular remodeling, but the exact cause is still unknown. We hypothesized that endothelial TLR3 insufficiency contributes to lung vascular remodeling induced by SARS-CoV-2. In the lungs of COVID-19 patients and SARS-CoV-2 infected Syrian hamsters, we discovered thickening of the pulmonary artery media and microvascular rarefaction, which were associated with decreased TLR3 expression in lung tissue and pulmonary artery endothelial cells (ECs). In vitro , SARS-CoV-2 infection reduced endothelial TLR3 expression. Following infection with mouse-adapted (MA) SARS-CoV-2, TLR3 knockout mice displayed heightened pulmonary artery remodeling and endothelial apoptosis. Treatment with the TLR3 agonist polyinosinic:polycytidylic acid reduced lung tissue damage, lung vascular remodeling, and endothelial apoptosis associated with MA SARS-CoV-2 infection. In conclusion, repression of endothelial TLR3 is a potential mechanism of SARS-CoV-2 infection associated lung vascular remodeling and enhancing TLR3 signaling is a potential strategy for treatment.

Comparison of freshly cultured versus cryopreserved mesenchymal stem cells in animal models of inflammation: A pre-clinical systematic review

Background:

Mesenchymal stem cells (MSCs) are multipotent cells that demonstrate therapeutic potential for the treatment of acute and chronic inflammatory-mediated conditions. Although controversial, some studies suggest that MSCs may lose their functionality with cryopreservation which could render them non-efficacious. Hence, we conducted a systematic review of comparative pre-clinical models of inflammation to determine if there are differences in in vivo measures of pre-clinical efficacy (primary outcomes) and in vitro potency (secondary outcomes) between freshly cultured and cryopreserved MSCs.

Methods:

A systematic search on OvidMEDLINE, EMBASE, BIOSIS, and Web of Science (until January 13, 2022) was conducted. The primary outcome included measures of in vivo pre-clinical efficacy; secondary outcomes included measures of in vitro MSC potency. Risk of bias was assessed by the SYRCLE ‘Risk of Bias’ assessment tool for pre-clinical studies.

Results:

Eighteen studies were included. A total of 257 in vivo pre-clinical efficacy experiments represented 101 distinct outcome measures. Of these outcomes, 2.3% (6/257) were significantly different at the 0.05 level or less; 2 favoured freshly cultured and 4 favoured cryopreserved MSCs. A total of 68 in vitro experiments represented 32 different potency measures; 13% (9/68) of the experiments were significantly different at the 0.05 level or less, with seven experiments favouring freshly cultured MSC and two favouring cryopreserved MSCs.

Conclusions:

The majority of preclinical primary in vivo efficacy and secondary in vitro potency outcomes were not significantly different (p<0.05) between freshly cultured and cryopreserved MSCs. Our systematic summary of the current evidence base may provide MSC basic and clinical research scientists additional rationale for considering a cryopreserved MSC product in their pre-clinical studies and clinical trials as well as help identify research gaps and guide future related research.

Funding:

Ontario Institute for Regenerative Medicine