Background: In contrast to arterioles, small arteries appear to be the preferential site of renal vascular smooth muscle cell (VSMC) proliferation under pathophysiological conditions. To date, techniques have been described to isolate renal arterioles and to culture VSMCs. The aim of the present study was to develop a method of culturing VSMCs from isolated small arteries of the rat kidney and to characterize their growth as compared with that of aortic VSMCs.
Methods: Renal vascular trees were isolated from kidneys of male Wistar rats by a sieving technique. VSMCs were grown from explants of collagenase-treated renal vascular trees and thoracic aorta. Growth curves and proliferation of renal and aortic VSMCs in response to fetal bovine serum (FBS) were compared by determination of cell number and DNA synthesis, measured as incorporation of 5-bromo-2'-deoxyuridine.
Results: Renal vascular trees consisted mainly of small arteries with a diameter of 80 to 400 microm (interlobar and arcuate arteries). As compared with total kidney or renal cortex, alkaline phosphatase activity was decreased by 81%, and vasopressin (10 micromol/L) was unable to stimulate adenylyl cyclase in renal vascular trees, indicating little tubular contamination. A homogenous population of spindle-shaped cells was cultured from renal vascular trees, which grew in a hill-and-valley pattern and stained positively for smooth muscle alpha-actin, according to the characteristics of VSMC phenotype. Renal VSMCs proliferated more slowly than aortic VSMCs and reached the plateau of growth at about half of the cell density of aortic VSMCs. Furthermore, proliferation of renal VSMCs depended more heavily on FBS concentration, since about threefold higher concentrations of FBS were needed for renal VSMCs to multiply at the same rate and to similarly stimulate DNA synthesis as compared with aortic VSMCs.
Conclusions: We present a method to culture renal VSMCs from small arteries of the rat kidney, which possess distinct growth characteristics as compared with aortic VSMCs.