Histological and immunohistochemical analyis of calcified and non-calcified valves from dialysis patients. Von Kossa staining was strongly positive in calcified valves from dialysis patients (Ai) and completely negative in all non-calcified control valves (Aii). Immunhistochemical staining for sclerostin revealed a strong expression in the calcified areas (arrows in Bi, calcification marked with asterisk) and a faint sclerostin expression in non-calcified areas (Ci, arrows) of the calcified valves from dialysis patients. The immunohistochemistry for sclerostin was negative in all non-calcified valves (Bii, Cii). Qt-RT PCR for sclerostin expression showed a highly significant upregulation of sclerostin expression in the calcified valves compared to the non-calcified valves (D). Gene expression in the non-calcified control valves was set as 1. All scale bars 50 ηm.