OBJECTIVE: HCaRG codes for an intracellular protein highly expressed in the kidney and its mRNA levels negatively correlate with the proliferation rate of different cell types. HCaRG overexpression was shown to inhibit the proliferation of embryonic kidney cells and to induce their differentiation into renal epithelial cells. The aim of this study was to investigate the role of HCaRG on kidney repair by assessing its effect on renal cell migration.

METHODS: HEK293 cells were transfected with either plasmid alone (N1) or plasmid containing HCaRG (H9). Cell migration in Boyden chambers with different extracellular matrix and wound healing motility assays were used to assess the migratory potential of cells overexpressing HCaRG.

RESULTS: Immunofluorescence microscopy showed that H9 cells exhibited multiple lamellipodia and colocalisation of HCaRG with F-actin. In contrast, N1 cells did not exhibit morphological changes compared to untransfected HEK293 cells. In vitro wound healing assay showed 48% for H9 compared to 5% for N1 wound closure after 24h. HCaRG overexpression also increased the migration potential of H9 cells by 6 times on collagen matrix and 5 times on laminin matrix. Abundant vinculin-containing focal adhesions were detected only in H9 cells suggesting that these cells exhibit a strong adhesion to substratum. Microarray analysis revealed higher expression in HCaRG-transfected cells of 12 genes involved in cell migration and formation of lamellipodia including TGF-alpha (13 fold), galectins (6 fold) and autotaxins (2.3 fold). Furthermore, H9 conditioned medium collected after 12 h increased three times the N1 cells migration over 24 h.

CONCLUSIONS: HCaRG incrased the migration potentiel of renal cells together with their differention into renal epithelial cells. The stimulatory effect of HCaRG on migration could be due to F-actin reorganisation. This phenomenon coupled to an overexpression of several genes implicated in cell motility and the secretion of motility activating factors in the H9 conditioned medium suggest a role for HCaRG in kidney repair after injury.

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