AUTHOR=Gu Guangli , Lv Xiaodan , Liu Gengfeng , Zeng Ruizhi , Li Shiquan , Chen Lan , Liang Zhaoliang , Wang Huiqin , Lu Fei , Zhan Lingling , Lv Xiaoping 

TITLE=Tnfaip6 Secreted by Bone Marrow–Derived Mesenchymal Stem Cells Attenuates TNBS-Induced Colitis by Modulating Follicular Helper T Cells and Follicular Regulatory T Cells Balance in Mice

JOURNAL=Frontiers in Pharmacology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2021.734040

DOI=10.3389/fphar.2021.734040

ISSN=1663-9812

ABSTRACT=Objective: To investigate the immunological mechanism of bone marrow-derived mesenchymal stem cells (BM-MSCs) in inflammatory bowel disease (IBD).
Methods: Mice with 2,4,6-trinitro-benzene sulfonic acid (TNBS)-induced colitis were intraperitoneally injected with phosphate-buffered saline, BM-MSCs, BM-MSCs with tumor necrosis factor-induced protein 6 (Tnfaip6) knockdown mediated by RNA interference recombinant adenovirus, and BM-MSCs-infected with control adenovirus or recombinant mouse Tnfaip6. The disease activity index (DAI), weight loss, and histological scores were recorded. Serum levels of Tnfaip6 and pro- and anti-inflammatory cytokines, including interleukin (IL)-21, tumor necrosis factor-alpha (TNF-α), IL-10, and Tnfaip6 were measured by enzyme-linked immunosorbent assay (ELISA). The relative expression levels of these cytokines and BCL-6, master regulators of follicular helper T cells (Tfh), and fork-like transcription factor p3 (Foxp3), and follicular regulatory T cells (Tfr) in colon were determined by real-time quantitative PCR (RT-qPCR). The infiltration of Tfh and Tfr in mesenteric lymph nodes (MLNs) and spleens were analyzed by flow cytometry.
Results: Compared to the normal control group, the expression levels of BCL-6, IL-21 in the colon, Tfh infiltration, and ratios of Tfh/Tfr in MLNs and spleen, and the serum concentrations of IL-21 and TNF-α increased significantly in the colitis model group (P<0.05). Intraperitoneal injection of BM-MSCs or Tnfaip6 ameliorated the weight loss, clinical and histological severity of colitis, downregulated the expression of BCL-6, IL-21, and TNF-α, upregulated the expression of Foxp3, IL-10, and Tnfaip6 (P<0.05), increased Tfr and reduced the infiltration of Tfh in MLNs and spleen, and downregulated Tfh/Tfr ratio (P<0.05). On the other hand, BM-MSCs lost the therapeutic effect and immunoregulatory function on Tfh and Tfr after Tnfaip6 knockdown.
Conclusion: Tfh increase in the inflamed colon, Tfh decrease, and Tfr increase during colitis remission phase, and the imbalance of Tfh/Tfr ratio is closely related to the progression of IBD. Tnfaip6 secreted by BM-MSCs alleviates IBD by inhibiting Tfh differentiation, promoting Tfr differentiation, and improving the imbalance of Tfh/Tfr in mice.