Prostaglandin E2 Potentiates Mesenchymal Stem Cell–Induced IL-10+IFN-γ+CD4+ Regulatory T Cells To Control Transplant Arteriosclerosis

Abstract

Mesenchymal stem cells (MSCs) are known for their immunomodulatory functions. We previously demonstrated that bone marrow–derived MSCs effectively control transplant arteriosclerosis (TA) by enhancing IL-10+ and IFN-γ+ cells. The objective of this study is to elucidate the mechanism by which MSCs induce IL-10+IFN-γ+CD4+ regulatory T type 1 (TR1)–like cells. In an MLR system using porcine PBMCs, MSC-induced IL-10+IFN-γ+CD4+ cells, which confer resistance to allogeneic proliferation in an IL-10–dependent manner, resemble TR1-like cells. Both cyclooxygenase-derived PGE2 and IDO help to induce TR1-like cells by MSCs. MSCs constitutively secrete PGE2, which is augmented in allogeneic reactions. However, TR1-like cells were deficient in PGE2 and 4-fold less potent than were MSCs in suppressing MLR. PGE2 mimetic supplements can enhance the immunosuppressive potency of TR1-like cells. In a porcine model of allogeneic femoral arterial transplantation, MSC-induced TR1-like cells combined with PGE2, but not either alone, significantly reduced TA at the end of 6 wk (percentage of luminal area stenosis: TR1-like cells + PGE2: 11 ± 10%; PGE2 alone: 93 ± 8.7%; TR1-like cells alone: 88 ± 2.4% versus untreated 94 ± 0.9%, p < 0.001). These findings indicate that PGE2 helps MSC-induced IL-10+IFN-γ+CD4+ TR1-like cells inhibit TA. PGE2 combined with MSC-induced TR1-like cells represents a new approach for achieving immune tolerance.