OBJECTIVETo evaluate global genome expression patterns of mitral valve tissues from dogs with degenerative mitral valve disease (DMVD).SAMPLE POPULATIONAnterior mitral valve leaflets of 4 dogs with severe DMVD and 4 healthy control dogs.PROCEDURESTranscriptional activities of 23,851 canine DNA sequences were determined by use of an oligonucleotide microarray. Genome expression patterns of tissue from dogs with DMVD were evaluated by measuring the relative amount of complementary RNA hybridization to the microarray probes and by comparing it with gene expression from healthy control dogs.RESULTS229 transcripts were differentially expressed (>or= 2-fold change). In dogs with DMVD, expression of 159 transcripts was upregulated and expression of 70 transcripts was downregulated. Of the 229 transcripts, 152 genes could be specifically identified. These genes were grouped into 1 of 9 categories on the basis of their primary physiologic function. Grouping revealed that pathways involving cell signaling, inflammation, extracellular matrix, immune function, cell defense, and metabolism were generally upregulated. Inflammatory cytokines and the serotonin-transforming growth factor-beta pathway were identified as contributory to the pathophysiologic aspects of DMVD.CONCLUSIONS AND CLINICAL RELEVANCEEvaluation of global expression patterns provides a molecular portrait of mitral valve disease, yields insight into the pathophysiologic aspects of DMVD, and identifies intriguing genes and pathways for further study.