Culture of Human Renal Medullary Interstitial Cells

The renal medullary interstitial cell (RMIC) is a unique lipid containing cell found mainly in the renal medulla between the tubular and vascular structures (1 ). These highly specialized fibroblast-like cells are abundant in the inner medulla and papilla (2 ), and are thought to be responsible for the production of both collagenous and noncollagenous extracellular matrix, secretion of vasoactive prostaglandins, and also for degradation of certain components of extracellular material, such as hyaluronic acid (3 ). The lipid droplets of these cells contain polyunsaturated fatty acids, which can serve as precursors for prostaglandins and other lipid-derived hormones (4 ) Ultrastructural studies show that, compared with cortical fibroblasts, the renal medullary interstitial cells are highly differentiated, with abundant rough endoplasmatic reticulum, free ribosomes, and a characteristic mitochondrial profile, suggesting an active secretory function.