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.

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