Histopathological changes and apoptosis detection in canine myxomatous mitral valve disease using tissue microarray technique

Myxomatous mitral valve disease (MMVD) is the most common cardiac disease in dogs. The etiology of MMVD is currently unclear. The cell density has been found increasingly in myxomatous mitral valves. The proliferation is unlikely a major mechanism of increased cell density in diseased valves. Other mechanisms such as anti-apoptosis or cell migration may be involved. The objective of this study was to determine the apoptotic cells within MMVD valves by assessing the immunoreactivity of cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay using tissue microarray technique. Fifteen normal and 40 MMVD valves were included in the study. TUNEL marker and cleaved caspase-3 expressions were significantly decreased in myxomatous valves compared to normal valves (p < 0.05). Apoptotic bodies were hardly seen in normal and diseased valves. These findings suggest a relationship between the anti-apoptotic mechanism and increased cellularity in canine MMVD.