KLF4 Drives Fibroblast Activation to Promote Kidney Fibrosis via YAP Signaling

Background: Fibroblasts are the primary cellular sources of scar-forming myofibroblasts, which synthesize excessive quantities of extracellular matrix (ECM) and contribute to kidney fibrosis. KLF4, one of the Yamanaka transcription factors, controls various essential cellular functions, including proliferation, differentiation, and embryonic development, and has been implicated in kidney diseases. However, the role and mechanism of KLF4 in regulating fibroblast phenotype transition and kidney fibrogenesis remain undefined. Methods: In our study, we examined the expression of Klf4 in renal biopsy tissue samples from patients with chronic kidney disease (CKD), as well as in two murine models of kidney fibrosis: unilateral ureteral obstruction (UUO) and ischemia-reperfusion (IR)-induced kidney fibrosis. We generated conditional knockout mice in which KLF4 gene was selectively and inducibly ablated in fibroblasts, and subjected these mice to UUO or IR. Additionally, we treated mice with a KLF4 inhibitor after UUO or IR. Results: In this study, we initially observed the induction of KLF4 in interstitial myofibroblasts from mouse and human fibrotic kidneys. In in vitro experiments, KLF4 expression in NRK-49F cells was induced after exposure to TGFβ1. Blocking KLF4 signaling by siRNA or KLF4 inhibitor Kenpaullone attenuated TGFβ1-induced fibroblast activation. Conversely, the KLF4 agonist Apto253 enhanced fibroblast activation induced by TGFβ1. Further in vitro studies indicated that activation of KLF4 signaling induced upregulation of Yes-associated protein (YAP) signaling in response to TGFβ1, which was reversed by KLF4 silencing. Mice with fibroblast-specific deletion of KLF4 showed reduced ECM deposition and downregulation of YAP-related signaling components compared to WT mice in both fibrotic models. Treatment with KLF4 inhibitor Kenpaullone ameliorated kidney ECM deposition in fibrotic nephropathy induced by UUO or IRI. Additionally, treatment with the YAP inhibitor VTP further reduced ECM deposition and ameliorated fibrotic nephropathy in knockout mice after UUO. Conclusion: These findings suggest that KLF4 significantly promotes fibroblast activation and kidney fibrogenesis potentially through activating the YAP singling pathway. Targeting this singling pathway may shine light on ways to protect against kidney fibrosis in patients with chronic kidney diseases. Funding: Government Support – Non-U.S.