Structural and cellular changes in canine myxomatous mitral valve disease: an image analysis study

Area of Science:

• Veterinary Cardiology
• Comparative Pathology
• Biomedical Imaging

Background:

• Myxomatous mitral valve disease (MMVD) is the most common cardiac condition in dogs, sharing similarities with human degenerative mitral valve disease.
• Quantitative data on cellular and morphological changes in canine MMVD are limited.

Purpose of the Study:

• To quantitatively assess morphological changes in canine MMVD using image analysis.
• To specifically measure alterations in cell numbers within myxomatous regions of the mitral valve.

Main Methods:

• Collected mitral valve complexes from normal dogs and dogs with varying MMVD severity (grades 1-4).
• Utilized ImageJ software for image analysis to measure valve leaflet dimensions, connective tissue characteristics, glycosaminoglycan (GAG) content, and cell morphology.
• Examined both normal and overtly myxomatous valve areas.

Main Results:

• Observed significant lengthening and thickening of mitral valve leaflets, particularly the posterior leaflet, with disease progression.
• Found a statistically significant decrease in cell numbers in myxomatous areas compared to normal valves, irrespective of disease grade.
• Identified connective tissue derangement and reduced density in myxomatous areas, correlating with increased disease severity and age.
• Noted increased glycosaminoglycan (GAG) expression with disease severity.

Conclusions:

• Canine MMVD involves valve leaflet elongation, thickening, loss of connective tissue, and reduced cellularity in specific regions.
• Cell shape (circularity) remained consistent between normal and diseased valves.
• Disease severity and age are associated with specific pathological changes in the mitral valve structure.