Differential protein expression between normal, early-stage, and late-stage myxomatous mitral valves from dogs.

Valvular heart disease accounts for over 20 000 deaths and 90 000 hospitalizations yearly in the United States. Myxomatous valve disease (MVD) is the most common disease of the mitral valve in humans and dogs. MVD is pathologically identical in these species and its pathogenesis is poorly understood. The objectives of this study were to (i) develop proteomic methodology suitable for analysis of extracellular matrix-rich heart valve tissues and (ii) survey over- and under-expressed proteins that could provide mechanistic clues into the pathogenesis of MVD. Normal, early-stage, and late-stage myxomatous mitral valves from dogs were studied. A shotgun proteomic analysis was used to quantify differential protein expression. Proteins were classified by function and clustered according to differential expression patterns. More than 300 proteins, with 117 of those being differentially expressed, were identified. Hierarchical sample clustering of differential protein profiles showed that early- and late-stage valves were closely related. This finding suggests that proteome changes occur in early degeneration stages and these persist in late stages, characterizing a diseased proteome that is distinct from normal. Shotgun proteome analysis of matrix-rich canine heart valves is feasible, and should be applicable to human heart valves. This study provides a basis for future investigations into the pathogenesis of MVD.