Histopathological and immunohistochemical characteristics of chordae tendineae affected by degenerative processes in canine myxomatous mitral valve disease

Myxomatous mitral valve disease is a major problem in canine cardiology. Degenerative changes extend from the valve leaflets to reach the rest of the subvalvular apparatus. The chordae tendineae (CT) play a key role in the mechanics of the mitral valve and ensure unidirectional blood flow through the heart. Degenerative changes within the chordae tendineae can severely disrupt their function, ultimately leading to an episode of chordae rupture. The study aimed to analyse the structure of healthy and degenerated CTs via histopathology and immunohistochemistry. The mitral valve was assessed macroscopically using the Whitney scale to identify degenerative changes. The chordae tendineae were classified on a four-grade scale (0-3) on the basis of structural changes and subsequently analysed through immunohistochemical staining with antibodies targeting collagens I, III, and IV, as well as fibronectin, chondroitin, and tenascin. The findings revealed alterations in the extracellular matrix in degenerated chordae tendineae.