Analysis of osteopontin levels for the identification of asymptomatic patients with calcific aortic valve disease

Calcific aortic valve disease (CAVD) is the most common cause of acquired valve disease. Initial phases of CAVD include thickening of the cusps, whereas advanced stages are associated with biomineralization and reduction of the aortic valve area. These conditions are known as aortic valve sclerosis (AVSc) and aortic valve stenosis (AVS), respectively. Because of its asymptomatic presentation, little is known about the molecular determinants of AVSc. The aim of this study was to correlate plasma and tissue osteopontin (OPN) levels with echocardiographic evaluation for the identification of asymptomatic patients at risk for CAVD. In addition, our aim was to analyze the differential expression and biological function of OPN splicing variants as biomarkers of early and late stages of CAVD. From January 2010 to February 2011, 310 patients were enrolled in the study. Patients were divided into 3 groups based on transesophageal echocardiographic (TEE) evaluation: controls (56 patients), AVSc (90 patients), and AVS (164 patients). Plasma and tissue OPN levels were measured by immunohistochemical evaluation, enzyme-linked immunosorbent assay (ELISA), and real-time quantitative polymerase chain reaction (qPCR). Patients with AVSc and AVS have higher OPN levels compared with controls. OPN levels are elevated in asymptomatic patients with AVSc with no appearance of calcification during TEE evaluation. OPN splicing variants OPN-a, OPN-b, and OPN-c are differentially expressed during CAVD progression and are able to inhibit biomineralization in a cell-based biomineralization assay. The analysis of the differential expression of OPN splicing variants during CAVD may help in developing diagnostic and risk stratification tools to follow the progression of asymptomatic aortic valve degeneration.