TGF-β2 Reduces the Cell-Mediated Immunogenicity of Equine MHC-Mismatched Bone Marrow-Derived Mesenchymal Stem Cells Without Altering Immunomodulatory Properties.

Alix K Berglund,Lauren V Schnabel,Julie M Long,James B Robertson

doi:10.3389/fcell.2021.628382

Abstract

Allogeneic mesenchymal stem cells (MSCs) are a promising cell therapy for treating numerous diseases, but major histocompatibility complex (MHC)-mismatched MSCs can be rejected by the recipient’s immune system. Pre-treating MSCs with transforming growth factor-β2 (TGF-β2) to downregulate surface expression of MHC molecules may enhance the ability of allogeneic MSCs to evade immune responses. We used lymphocyte proliferation assays and ELISAs to analyze the immunomodulatory potential of TGF-β2-treated equine bone marrow-derived MSCs. T cell activation and cytotoxicity assays were then used to measure the in vitro cell-mediated immunogenicity. Similar to untreated MSCs, TGF-β2-treated MSCs inhibited T cell proliferation and did not stimulate MHC-mismatched T cells to proliferate. Additionally, similar quantities of prostaglandin E2 and TGF-β1 were detected in assays with untreated and TGF-β2-treated MSCs supporting that TGF-β2-treated MSCs retain their strong immunomodulatory properties in vitro. Compared to untreated MSCs, TGF-β2-treated MSCs induced less T cell activation and had reduced cell-mediated cytotoxicity in vitro. These results indicate that treating MSCs with TGF-β2 is a promising strategy to reduce the cell-mediated immunogenicity of MHC-mismatched MSCs and facilitate allogeneic MSC therapy.

Highlights

Mesenchymal stem cells (MSCs) are currently being investigated in clinical trials for the treatment of musculoskeletal, immune-mediated, and degenerative diseases (Squillaro et al, 2016; Galipeau and Sensébé, 2018)
T cell proliferation was detected in the negative control (MHC-matched Peripheral blood leukocytes (PBLs) stimulator cells) by the presence of live CD3+CFSElow cells and as expected, an increased number of live CD3+ CFSElow cells were detected in the positive control (MHC-mismatched with PBL stimulator cells) (Figure 1C)
T cell proliferation was significantly reduced in all Mixed lymphocyte reactions (MLRs) with MSC stimulator cells compared to assays with major histocompatibility complex (MHC)-mismatched PBL stimulator cells as measured by both the relative division index (Figure 1D) and relative GMFI of proliferating cells (Figure 1E)

Summary

Introduction

Mesenchymal stem cells (MSCs) are currently being investigated in clinical trials for the treatment of musculoskeletal, immune-mediated, and degenerative diseases (Squillaro et al, 2016; Galipeau and Sensébé, 2018). MSCs are strongly immunomodulatory in vitro, which initially led investigators to conclude that MSCs were immune privileged and that allogeneic cells could be used without risk of rejection (Le Blanc et al, 2003). Donor MHC I-specific CD8+ T cell and cytotoxic alloantibody responses have been detected following in vivo administration of allogeneic MSCs (Zangi et al, 2009; Berglund and Schnabel, 2017). Rejection of donor MSCs may lead to increased risk of adverse events and decreased therapeutic potential and must be prevented to realize the full clinical potential of allogeneic MSC therapy (Berglund et al, 2017b)

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