Abstract
Purpose :
Mesenchymal stem cells (MSCs) regulate adaptive immune responses in various inflammatory disorders. Here, we investigate whether MSCs directly interact with T regulatory cells (Tregs) to promote their suppressive function in corneal transplantation.
Methods :
Bone marrow MSCs (CD45-CD34-SCA1+CD29+) and CD4+CD25+ Tregs (purity: >95% Foxp3+) from spleen and lymph nodes (LNs) of Balb/c mice were used. MSC-Treg co-cultures were set up in the presence or absence of Transwells (1 μm pore size) for 48h. Flow cytometry was performed to assess (i) Tregs for Foxp3 levels and frequencies of Foxp3high Tregs and (ii) MSCs for CD80 expression. Results were calculated as fold change from normal controls. To evaluate the contribution of MSC-expressed CD80 on Treg function, MSC-Treg co-cultures were neutralized with anti-CD80 antibody (1 mg/ml), and CD80-silenced MSCs were intravenously administered to transplanted allogeneic mice (Balb/c grafted with B6 corneas). Corneal opacity was evaluated to assess graft survival.
Results :
A significant increase was observed in frequencies of Foxp3high Tregs (fold change: 4.8 ± 0.6; p<0.01) and their FoxP3 expression (fold change in MFI: 3.4 ± 0.7; p<0.01) in direct co-cultures of MSCs and Tregs compared to Tregs cultured alone. Inhibition of cell-cell contact via Transwell mitigated this effect (p<0.05). Data showed significant expression of CD80 on MSCs, and neutralization of CD80 in the co-cultures resulted in a decrease of Foxp3high Treg frequencies (fold change: 2.8 ± 0.8; p<0.04) and levels of Foxp3 in Tregs (fold change in MFI: 1.6 ± 0.6; p<0.05). Mice treated with CD80-silenced MSCs did not show augmented frequencies of Tregs with high Foxp3 levels (fold change: 1.3 ± 0.3) and enhanced graft survival (p<0.02) compared to control shRNA/MSC-treated controls (fold change: 2.4 ± 0.3; p<0.03).
Conclusions :
MSC-expressed CD80 directly amplifies function of regulatory T cells and promotes corneal graft survival.
This is a 2021 ARVO Annual Meeting abstract.