Inflammatory licensed equine MSCs are chondroprotective and exhibit enhanced immunomodulation in an inflammatory environment

Abstract

BackgroundInflammatory licensed mesenchymal stem cells (MSCs) have the ability to promote functional tissue repair. This study specifically sought to understand how the recipient tissue environment reciprocally affects MSC function. Inflammatory polarized macrophages, modeling an injured tissue environment, were exposed to licensed MSCs, and the resultant effects of MSC immunomodulation and functionality of the MSC secretome on chondrocyte homeostasis were studied.MethodsInflammatory licensed MSCs were generated through priming with either IFN-γ or polyinosinic:polycytidylic acid (poly I:C). Macrophages were polarized to an inflammatory phenotype using IFN-γ. Licensed MSCs were co-cultured with inflammatory macrophages and immunomodulation of MSCs was assessed in a T-cell proliferation assay. MSC gene expression was analyzed for changes in immunogenicity (MHC-I, MHC-II), immunomodulation (IDO, PTGS2, NOS2, TGF-β1), cytokine (IL-6, IL-8), and chemokine (CCL2, CXCL10) expression. Macrophages were assessed for changes in cytokine (IL-6, IL-10, TNF-α, IFN-γ) and chemokine (CCL2, CXCL10) expression. Conditioned medium representing the secretome from IFN-γ or poly I:C-primed MSCs was applied to IL-1β-stimulated chondrocytes, which were analyzed for catabolic (IL-6, TNF-α, CCL2, CXCL10, MMP-13, PTGS2) and matrix synthesis (ACAN, COL2A1) genes.ResultsIFN-γ-primed MSCs had a superior ability to suppress T-cell proliferation compared to naïve MSCs, and this ability was maintained following exposure to proinflammatory macrophages. In naïve and licensed MSCs exposed to inflammatory macrophages, MHC-I and MHC-II gene expression was upregulated. The secretome from licensed MSCs was chondroprotective and downregulated inflammatory gene expression in IL-1β-stimulated chondrocytes.ConclusionsIn-vitro inflammatory licensing agents enhanced the immunomodulatory ability of MSCs exposed to inflammatory macrophages, and the resultant secretome was biologically active, protecting chondrocytes from catabolic stimulation. Use of licensing agents produced a more consistent immunomodulatory MSC population compared to exposure to inflammatory macrophages. The clinical implications of this study are that in-vitro licensing prior to therapeutic application could result in a more predictable immunomodulatory and reparative response to MSC therapy compared to in-vivo inflammatory licensing by the recipient environment.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-0840-2) contains supplementary material, which is available to authorized users.

Pluripotency and Immunomodulatory Signatures of Canine Induced Pluripotent Stem Cell-derived Mesenchymal Stromal Cells Are Similar to Harvested Mesenchymal Stromal Cells

“…That cAT-MSCs did not show an increase in iNOS expression beyond constitutive levels, and cBM-MSCs expressed very low levels in response to cTNF-α/cIFN-γ, is in keeping with the observations by Chow et al [72] that cAT-MSCs and cBM-MSCs do not employ the iNOS/NO-mediated pathway for immunosuppression. In contrast, the strong upregulation of iNOS expression in ciMSCs is similar to observations in the horse where priming of equine bone marrow-derived MSCs with IFN-γ or TNF-α/IFN-γ similarly induced an upregulation of iNOS [83]. Expression of iNOS signi cantly decreased in ciMSCs co-cultured with mitogen-stimulated lymphocytes.…”

“…ciMSCs showed the strongest response to all three treatments, particularly to cTNF-α. The induced upregulation of IL-8 by in ammatory stimuli has also been reported in human [95] and equine MSCs [83,96].…”

The Potential of Mesenchymal Stem Cells to Treat Systemic Inflammation in Horses

“…In vitro, priming equine MSCs with IFN-γ showed better ability to suppress T-cell proliferation when compared to naïve MSCs. This effect was also maintained following exposure to inflammatory macrophages (43). Priming MSCs prior to injection may ensure that the best response is achieved as some treatment environments may not adequately activate the cells.…”

Mechanisms of Action of Multipotent Mesenchymal Stromal Cells in Tendon Disease

“…These studies provide preliminary insight into the modulation of inflammatory tenocyte activation by MSC, while they also suggest that their immunomodulatory potential may be higher when not tenogenically differentiated. Yet, MSC immunomodulation is highly contextspecific and influenced by a variety of factors including three-dimensional culture environments as well as inflammatory priming/licensing [172,173]. Therefore, it remains crucial to perform further studies specifically mimicking aspects of tendon pathophysiology.…”