Injured proximal tubular epithelial cells lose HNF4A expression crucial for brush border formation and transport.

Abstract

Recent studies have demonstrated that the transcription factor hepatocyte nuclear factor 4α (HNF4A) drives epithelial differentiation in the renal proximal tubules (PT) and is critical for maintaining a mature PT phenotype. Furthermore, HNF4A downregulation has been observed following kidney injury in mouse models. The aim of the present work was to investigate the role of HNF4A during acute and chronic human kidney disease and the loss of the mature PT phenotype in cultured PT cells. By immunohistochemistry, we discovered that loss of HNF4A expression and gain of vimentin expression is reciprocal and gradual during both acute and chronic kidney disease. Healthy human kidneys demonstrated partial or total loss of HNF4A expression in vimentin-positive scattered tubular cells. Primary cell isolation and subculture of PT cells recapitulated HNF4A-associated loss of the PT phenotype. Re-expression of HNF4A in cultured PT cells by adenoviral transduction increased transcripts related to brush border formation as well as absorptive and transport processes, as shown by RNA sequencing and gene set enrichment analyses. Thus, the reduction of HNF4A and increase of vimentin expression is connected to both acute and chronic kidney disease and represent a stereotypic injury response of the PT, resulting in dedifferentiation. HNF4A re-expression in cultured primary PT cells could provide a more reliable and predictive in vitro model to study PT function and injury.