Abstract

Arterial medial calcification is an independent risk factor for mortality in chronic kidney disease. We previously reported that knock-down of PKC expression increases high phosphate-induced mineral deposition by vascular smooth muscle cells in vitro. This new study tests the hypothesis that PKC regulates uremia-induced medial calcification in vivo. Female wild-type and PKC-/- mice underwent a two-stage subtotal nephrectomy and were fed a high phosphate diet for 8 weeks. X-ray micro computed tomography demonstrated that uremia-induced medial calcification was increased in the abdominal aorta and aortic arch of PKC-/- mice compared to wild-types. Blood urea nitrogen was also increased in PKC-/- mice compared to wild-types; there was no correlation between blood urea nitrogen and calcification in PKC-/- mice. Phosphorylated SMAD2 immunostaining was detected in calcified aortic arches from uremic PKC-/- mice; the osteogenic marker Runx2 was also detected in these areas. No phosphorylated SMAD2 staining were detected in calcified arches from uremic wild-types. PKC knock-down increased TGF-{beta}1-induced SMAD2 phosphorylation in vascular smooth muscle cells in vitro, whereas the PKC activator prostratin decreased SMAD2 phosphorylation. In conclusion, loss of PKC increases uremia-induced medial calcification. The PKC/TGF-{beta} signaling axis could therefore represent a new therapeutic target for arterial medial calcification in chronic kidney disease.