The Role of TGF-β Signaling and Resident Memory T cells in Aristolochic Acid Induced Kidney Injury

Resident memory T cells (TRMs) are recognized as mediators of autoimmune diseases and other chronic inflammatory diseases. CD4 and CD8 TRMs express adhesion molecules like CD103 (integrin alpha-E) and/or CD49a (integrin alpha-1), which are used as identifying markers and allow them to remain within tissues. A great deal of work has aimed at identifying the cytokines and other factors responsible for TRM differentiation, revealing IL-15, TNF-α, and most prominently TGF-β as major drivers of TRM formation. In cases of immunity, TRMs serve a protective role, guarding against reinfection from the pathogens. However, TRMs also cause chronic inflammation through their secretion of cytokines and cytolytic molecules. Our laboratory previously reported that kidney TRMs expand and become a predominant kidney immune cell population within six weeks of aristolochic acid (AA)-induced kidney injury and do so independently of cognate-antigen presentation. Furthermore, we showed CD4 and CD8 kidney TRMs express a gene signature aligns with those of previously reported skin, lung, and gut TRMs, which were driven by TGF-β signaling, and we found that CD8 TRMs upregulated TNF-α, IFN-γ, perforin, and granzyme B. Thus, we hypothesize that impairing TGF-β signaling in T cells will prevent kidney TRM formation after AA-induced kidney injury, and that doing so will ameliorate kidney injury and fibrosis. To test this hypothesis, we subjected a transgenic mouse line generated from a cross of Lck-Cre and TGF-β receptor 2 (TGFBR2)-Flox, in which TGF-β receptor 2 is specifically deleted in T cells, to AA-induced kidney injury via i.p. injections for 5 consecutive days at 2mg/kg in saline. Six weeks later we evaluated kidney injury and kidney immune cell populations. Flow cytometric analysis revealed that Cre negative AA-injured mice had a significant increase in kidney CD4+ CD103+ TRMs (p=0.0305), but KO mice had significantly lower levels than Cre negative injured mice (p=0.0310) and levels were not elevated about vehicle-treated controls (p>0.9999). Similarly, while kidney CD8+ CD103+ TRMs were elevated in Cre negative AA-injured mice compared to vehicle controls (p=0.0128), KO mice had significantly lower levels compared to injured Cre negative mice (p=0.0087) and did not have elevated levels compared to vehicle controls (p=0.9301). Despite these changes in CD103+ TRM populations, there were no differences in kidney CD45+ immune cell numbers, CD4+ T cell proportions, or CD8+ T cell proportions in injured KO mice compared to injured Cre negative mice. Additionally, there were no differences in kidney CD49a+ TRM proportions in injured KO mice compared to injured Cre negative mice, reinforcing the belief that TGF-β specifically controls the transcriptional signature of CD103+ TRMs. While AA-injury trended towards an increase in serum creatinine (SCr) compared to vehicle treatment (saline) in Cre negative (WT) littermates (p=0.0521), there was no difference between vehicle treated mice and T cell TGFBR2 knockout (KO) mice injured with AA (p=0.9893), suggesting a protective effect of T cell TGF-β KO. Furthermore, histological analysis of H&E stained kidney sections from injured KO mice were remarkably devoid of signs of tubular apoptosis and atrophy, whereas in injured Cre negative mice 25-50% of tubules were atrophied. Despite this improvement in tubular atrophy, injured KO mice appeared to have more interstitial fibrosis (Masson’s Trichrome) compared to injured Cre negative controls. In conclusion, TGF-β signaling controls the fate of CD103+ kidney TRMs in AA-induced kidney injury, although whether or not their depletion is protective or not is a more nuanced question that will require further investigation. F32DK136187, R01DK118932 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.