Background/Purpose: Umbilical cord (UC) derived mesenchymal stem cells (MSCs) have shown immunoregulation on various immune cells. The aim of this study is to investigate the mechanism of UC-MSCs in the upregulation of peripheral regulatory T cells in patients with systemic lupus erythematosus (SLE).

Methods: Peripheral blood mononuclear cells (PBMC) from 20 SLE patients and normal controls were co-cultured with UC-MSCs at the ratios of 1:1, 10:1 and 50:1 respectively for 72  hours, and the proportions of CD4⁺CD25⁺Foxp3⁺regulatory T cells were analyzed by flowcytometry. PBMC and serum from active SLE patients and normal controls were used to stimulate UC-MSCs, TGF-β1 mRNA expressions on UC-MSCs were detected by real-time PCR. Supernatant TGF-β1 levels were determined by ELISA. The TGF-β1 small interfering RNA (siRNA) was used to interfere TGF-β1 expression on UC-MSCs, then to determine its effect on the regulation of SLE Treg cells. TGF-β1 inhibitor was added in the culture system of UC-MSCs and PBMC from active SLE patients to observe its role on the upregulation of Treg cells by UC-MSCs.

Results: UC-MSCs could dose-dependently upregulate peripheral CD4⁺CD25⁺Foxp3⁺Treg proportion in SLE patients, which was not depended on cell-cell contact. UC-MSCs had no regulatory effect on Treg cells in normal controls. Compared with the non-stimulated group and normal PBMC stimulated group, PBMC from SLE patients significantly promoted TGF-β1 mRNA expression on UC-MSCs (relative gene expression was 1.00 ± 0.09, 1.95 ± 0.62, 4.20 ± 2.34, respectively, both P<0.05). Supernatant TGF-β1 levels were significantly elevated in the presence of SLE PBMC. Serum of SLE patients (5%) enhanced TGF-β1 mRNA expression on UC-MSCs (12.19 ± 4.49), remarkably higher than fetal bovine serum cultured group (1.33 ± 0.06, P<0.01) and normal control serum cultured group (2.53 ± 0.72, P<0.01). Additionally, TGF-β1 siRNA interfered UC-MSCs failed to upregulate Treg cells in SLE patients (SLE PBMC + TGF-β1siRNA UC-MSCs group 2.33% ± 0.99% vs. SLE PBMC group 1.80% ± 0.65%, P>0.05). Furthermore, in the presence of TCR stimulation, TGF-β1 specific inhibitor SB431542 significantly inhibited the regulatory role of UC-MSCs on Treg cells in SLE patients (SLE PBMC+UC-MSCs+SB431542 group 4.58%±2.10% vs. SLE PBMC+UC-MSCs group 7.85%±3.54%, P<0.05).

Conclusion: Immune microenvironment in SLE patients can significantly stimulate TGF-β1 expression on UC-MSCs, which plays an important role in the upregulation of Treg cells in patients. This study provides a new mechanism for the regulation of Treg cells by UC-MSCs in SLE.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-mechanism-of-umbilical-cord-mesenchymal-stem-cells-in-the-upregulation-of-regulatory-t-cells-by-tgf-%ce%b21-in-systemic-lupus-erythematosus/