Fig 4. TNFα induces a mesenchymal transition and fibrogenic gene expression in HK-2 cells.

A. Immunofluorescence images of HK-2 cells treated with vehicle control (left) or TNFα (right); Cells were co-stained with anti-vimentin antibodies (green, top panels) and pRelA antibodies (red, bottom panels). Increased nuclear pRelA staining in TNFα-treated cells indicates NFκB activation. Induction of vimentin in TNFα-stimulated cells marks the cell fate transition to a mesenchymal-like phenotype. B. Micrograph of HK-2 cells treated with vehicle control (left) or TNFα (right). The TNFα-stimulated cells display an elongated fibroblastic morphology, characteristic of mesenchymal cells. C. The boxplot shows significantly increased levels of vimentin mRNA expression during kidney aging, using expression data from Rodwell et al. 2004. D. Collagen genes are induced by TNFα stimulation and tend to increase expression during aging. The left column of the heat map shows the log₂-fold-changes in expression of 14 collagen transcripts following stimulation of HK-2 cells with TNFα. The right column of the heat map shows the age-related slope for these genes during kidney aging.