Influence of microvascular endothelial cells on transcriptional regulation of proximal tubular epithelial cells.

In the renal cortex the peritubular capillary network and the proximal tubular epithelium cooperate in solute and water reabsorption, secretion, and inflammation. However, the mechanisms by which these two cell types coordinate such diverse functions remain to be characterized. Here we investigated the influence of microvascular endothelial cells on proximal tubule cells, using a filter-based, noncontact, close-proximity coculture of the human microvascular endothelial cell line HMEC-1 and the human proximal tubular epithelial cell line HK-2. With the use of DNA microarrays the transcriptomes of HK-2 cells cultured in mono- and coculture were compared. HK-2 cells in coculture exhibited a differential expression of 99 genes involved in pathways such as extracellular matrix (e.g., lysyl oxidase), cell-cell communication (e.g., IL-6 and IL-1 beta), and transport (e.g., GLUT3 and lipocalin 2). HK-2 cells also exhibited an enhanced paracellular gating function in coculture, which was dependent on HMEC-1-derived extracellular matrix. We identified a number of HMEC-1-enriched genes that are potential regulators of epithelial cell function such as extracellular matrix proteins (e.g., collagen I, III, IV, and V, laminin-alpha IV) and cytokines/growth factors (e.g., hepatocyte growth factor, endothelin-1, VEGF-C). This study demonstrates a complex network of communication between microvascular endothelial cells and proximal tubular epithelial cells that ultimately affects proximal tubular cell function. This coculture model and the data described will be important in the further elucidation of microvascular endothelial and proximal tubular epithelial cross talk mechanisms.