Decoding the resistin-CAP1 pathway in intermediate monocytes mediating liver allograft rejection.

Background & Aims: Lymphocytes are widely recognized as the primary mediators of cellular rejection after liver transplantation. However, conventional immunosuppressive regimens that target lymphocytes, such as calcineurin phosphatase inhibitors, corticosteroids, or lymphocyte-depleting antibodies, can only partially mitigate rejection while inducing severe adverse effects. This necessitates the search for novel immunotherapeutic targets.

Methods: We harnessed the power of single-cell RNA sequencing and spatial transcriptomics in 24 rat transplanted liver and peripheral blood mononuclear cell samples to derive gene expression signatures recapitulating 13 cell phenotypes. We used flow cytometry, multifactor assays and multiple recombinant assays to validate the role of the target protein resistin and the resistin-CAP1 interaction on human T-cell function, in vitro and in vivo. Gold nanoparticles were used to package Retn siRNA sequences to validate the role of Retn knockdown on acute rejection after liver transplantation.

Results: By distinguishing between donor and recipient cells, we delineate the dynamic landscape of immune cells during allograft rejection and their spatial distributions across donors and recipients. Our findings underscore the pivotal role of recipient-derived intermediate monocytes in cellular rejection. Using CellChat ligand-receptor analysis, we identify the resistin-CAP1 pathway as a key mechanism by which intermediate monocytes participate in T cell-mediated rejection reactions. We confirm that resistin knockdown significantly alleviates acute rejection after rat liver transplantation, markedly extending the survival of recipients using innovative nanogold technology.

Conclusion: These findings offer insights into dynamic changes in the alloimmune microenvironment, pinpointing intermediate monocytes as potential diagnostic and immunotherapeutic targets during allograft rejection. This study holds significant importance in advancing non-invasive diagnostic technologies and immunotherapeutic strategies for allogeneic rejection.

Impact And Implications: This study pioneers the application of spatial transcriptomics in liver transplantation, providing a comprehensive analysis of immune cell spatial distribution, complemented by souporcell-based chimerism assessment. We demonstrate that intermediate monocytes play a pivotal role in T cell-mediated acute rejection via the resistin-CAP1 signaling axis. Targeting this pathway using nanogold-siRNA technology effectively mitigates rejection and enhances graft survival. These findings contribute novel insights into the mechanisms of transplant rejection and present promising avenues for the development of targeted therapeutic and diagnostic strategies in liver transplantation.