Avaliação histológica, histoquímica e imunoistoquímica da válvula mitral normal e com degeneração mixomatosa de cães e suínos ; Histological, histochemical and immunohistochemical mitral valve with normal and myxomatous degeneration of dogs and pigs

Myxomatous mitral valve degeneration (MMVD) or mitral valve endocardiosis is an endocardial age-related disease characterized by the mucopolysaccharide (MPS) accumulation and by collagen degeneration in mitral valves of many species, especially in humans, dogs and swine. Metalloproteinases (MMP) are proteolytic enzymes responsible for the extracellular matrix (ECM) remodelling in regular and pathological tissue. It has been suggested that the changing of the valvular distribution of these enzymes might be responsible for MMVD genesis. Likewise, vasoactive substances like nitric oxide (NO) played a role in the endocardiosis development. The aim of this study was to evaluate the histological changes, the expression of nitric oxide synthase (NADPH-d) and the immunohistochemical localization of MMP-2 and MMP-9 in the anterior leaflet in dogs and swine with regular mitral valves and those with endocardiosis. For this purpose, two experiments were done. First, 12 mitral valves of dogs and 22 of swine were analyzed. Valves were fixed in a 4% paraformaldehyde, exposed to NADPH-d reaction, processed routinely and microscopically evaluated for the detection of MPS deposition, collagen degeneration and fibrosis. In dogs, very high intensity reaction to NADPH-d was associated with higher endocardiosis degree and with presence of MPS deposition as well as collagen degeneration. There was no alteration in colour during the swine valves reaction to NADPH-d. In conclusion, NO works in canine mitral valves, remodeling MEC and playing a role in dogs mitral endocardiosis disease. In swine, it is suggested that NO has restricted action in MEC or there are major differences on the structures of swine valves because there was no reaction to NADPH-d and absence of macroscopical endocardiosis lesions. For the second study, 25 mitral valves of dogs and 32 valves of swine were also analyzed. Valves were macroscopically evaluated for the occurrence or not of endocardiosis. They were fixed in a 4% paraformaldehyde, routinely processed and ...