ER-stressed MSC displayed more effective immunomodulation in RA CD4CXCR5ICOS follicular helper-like T cells through higher PGE2 binding with EP2/EP4.

To analyze the further immunomodulatory effects of endoplasmic reticulum (ER)-stressed umbilical cord-derived mesenchymal stem cells MSCs (UC-MSCs) on rheumatoid arthritis (RA) CD4CXCR5ICOS T (follicular helper-like T, Tfh) cells. MSCs were isolated from umbilical cord and surface markers were identified by flow cytometry. CD4 T cells were purified from RA patients' peripheral blood mononuclear cells (PBMCs) using immunomagnetic beads. Thapsigargin (Tg)-stimulated or unstimulated MSCs were co-cultured with RA CD4 T cells. CD4CXCR5ICOS T cells were analyzed with fluorescence activating cell sorter (FACS) and major soluble factors secreted by MSCs were detected by qRT-PCR as well as ELISA. Receptors of prostanoid E2 (PGE2), known as EP1-4, on CD4 T cells were tested with RT-PCR and FACS. Proportion of CD4CXCR5ICOS T cells was determined after EP2/EP4 antagonists and anti-IL-6R antibody was added into co-cultured system, respectively. ER-stressed MSCs further down-regulated peripheral CD4CXCR5ICOS T cells compared with Tg-stimulated MSCs and CD4 T co-cultured group. PGE2 and IL-6 increased obviously in the supernatants. EP2/EP4 could be detected on CD4 T cells and frequencies of CD4CXCR5ICOS T cells were upregulated when EP2 and/or EP4 antagonists rather than anti-IL-6R antibody were added. ER-stressed MSCs exhibited better inhibition effect on RA CD4CXCR5ICOS T cells by releasing PGE2, indicating the immunosuppressive effect of MSCs could be enhanced by induction of ER stress.