Abstract Body: Background: Clinical and preclinical studies show that CD4+ T-cells infiltrate the failing hearts (HF) and undergo a pro-inflammatory phenotypic switch promoting left ventricle (LV) remodeling. However, the molecular signals that mediate this pro-inflammatory transition in CD4+ T-cells are unknown.
Methods and Results: We analyzed single-cell and -nuclear RNA sequencing data and identified Kruppel-like factor 6 (KLF6), a transcription factor regulating cell proliferation and apoptosis, as one of the significantly upregulated genes in CD4+ T-cells present in the hearts of dilated cardiomyopathy (DCM) patients as compared to the T-cells from control hearts (padj = 0.020). Furthermore, weighted gene co-expression network analysis showed KLF6 to be one of the most interconnected genes, indicating a significant role in mediating CD4+ T-cell pathogenicity. Studies using myocardial infarction (MI) mouse model validated these and showed upregulation of KLF6 in CD4+ T-cells present in the failing hearts (8 wks post-MI). Also, circulating CD4+ T-cells in DCM patients had significantly higher KLF6, as measured by mean fluorescence intensity (MFI; 4838±879 vs 3962±873 in controls; p = 0.049). Additionally, cardiac KLF6+CD4+ T-cells in DCM patients displayed significantly higher expression of CD44 (2297±168 vs 1782±95 MFI; p = 0.043), a marker for antigen-experienced T-cells and Ki67 (825±879 vs 487±165 MFI; p = 0.014), a proliferation marker than KLF6-CD4+ T-cells suggesting that higher KLF6 expression is associated with antigen experienced and proliferative CD4+ T-cells. To further characterize KLF6’s role, we activated mouse splenic and human circulating CD4+ T-cells using anti-CD3/CD28 antibodies and measured KLF6 expression. Following stimulation, KLF6 increased significantly in both mouse (~4.5 fold increase, p < 0.001) and human (~3.8-fold increase, p < 0.001) CD4+ T-cells. Importantly, KLF6+CD4+ T-cells had higher CD69 and TNFα expression as compared to KLF6-CD4+ T-cells suggesting a pro-inflammatory phenotype of KLF6 expressing CD4+ T-cells.
Conclusions: Our data suggest that KLF6 is a crucial transcription factor driving pathogenic and pro-inflammatory CD4+ T-cell transitioning, potentially contributing to HF.