Uncovering the Single-cell Transcriptomic Signatures and Pathogenesis of Mucosal-associated Invariant T cells during Nonalcoholic Steatohepatitis

Background As an inflammatory subtype of nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH) has turned into a major trigger of liver cirrhosis and liver-associated deaths worldwide. Longitudinal studies have indicated the T lymphocyte-associated immunodysfunction in the pathogenesis of NAFLD, yet the detailed information of the subsets including Mucosal-associated Invariant T (MAIT) cells in NASH is largely obscure. Methods In this study, we isolated peripheral blood-derived mononuclear cells (PBMCs) from NASH patients and healthy controls (HC), and dissected the single-cell transcriptomic signatures of immune cell sub-clusters and MAIT cells by conducting multifaceted bioinformatics analyses. Meanwhile, the distribution and expression of MAIT cells and the candidate biomarkers (e.g., GADD45B, STAT1, CCL4, RPL38) in liver tissues or PBMCs was identified by immunostaining (e.g., IHC, IF), qRT-PCR and western-blotting analysis. Additionally, the STAT1-mediated network in MAIT cell-related regulatory mechanism of NASH was explored as well. Results Compared to the HC group, NASH patients revealed multifaceted variations in the distribution of MAIT cells and the relative immune cells in PBMCs. In detail, MAIT cells were collectively accumulated in PBMCs and liver tissues of NASH patients, which revealed a distinct distribution pattern from the HC group according to the 7 sub-clusters. Of the indicated candidate biomarkers for clinical diagnosis, STAT1-T-bet axis served as the pathogenic mechanism of NASH via mediating MAIT cell differentiation and inflammatory response. Conclusion Overall, our data illuminated the single-cell transcriptomic signatures of MAIT cells and the concomitant sub-clusters in NASH patients. Our findings put forward the involvement of MAIT cells in NASH, which would benefit the further dissection of the MAIT cell-related pathogenesis and clinical diagnosis of NASH.