Valva mitral de suinos : uma abordagem bioquimica emorfologica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The mitral valve is a complex connective tissue structure, constituted by collagenous proteins, non collagenous proteins and proteoglycans. Structurally the valve leaflets are composed of four main layers: auricularis, fibrosa, spongiosa and ventricularis. The fibrosa layer forms the structural core of the valve, while the spongiosa has an important role in absorption of shock. The chordae tendineae has two distinct layers, a large fibrous core surrounded by a spongenous layer. Several abnormalities of mitral valve have been reported, as the result of injuries caused by degenerative calcium accumulation, infectious endocarditis and disorders associated with collagen content, hyaluronic acid and glycosaminoglycans abnormalities. Among the treatments normally used, have been realized repair techniques of portions of the valve or replacement of these with a prosthetic valve or bioprostheses. Detailed information about organization and composition aspects of the leaflets and chordae tendineae are necessary. For morphological analysis, whole mounts and histological sections of leaflets and chordae tendineae were stained by toluidine blue. Analysis of whole mounts in polarization microscopy showed an intense brightness of the collagen fibrils, demonstrating the high molecular organization of the collagen in the chordae tendineae while in the valve leaflets collagen fiber is multidirectional. In this case, collagen fibrils coming from the chordae tendineae branch cross each other forming a network-like structure. Intense metachromasy was observed in leaflet region of chordae tendineae insertion, with a non uniform distribution. Leaflets transversal sections showed the spongiosa layer with soft connective tissue characteristics, and the fibrosa, where collagens bundles are highly arranged. For the biochemical study extracelular matrix components were extracted with 4M guanidinium chloride, fractionated in DEAE-Sephacel and analysed by SDS-PAGE. The non collagenous proteins found showed Mr values between 19-179kDa and 19-235kDa to the leaflet and chordae tendineae respectively. Several similar proteins were found in both tissues. Polidisperses bands around 70kDa and 80-100kDa which probably correspond to the small proteoglycans fibromodulin and decorin respectively were found. The analysis in agarose-polyacrylamide gel revealed a polydisperse and metachromatic band in the leaflet and chordae tendineae, indicating the presence of proteoglycans of high molecular weight presumables versican. According to our morphological and biochemical studies, it may be concluded that: 1) The chordae tendineae showed larger amounts of proteins and glycosaminoglycans than the leaflet; 2) Small and large proteoglycans are present in both tissues; 3) The collagen bundles are highly organized in the chordae tendineae while in the leaflet they have a multidirectional arrangement; 4) Proteoglycans have a non uniform distribution in the leaflets, probably due to a non uniform action of compressive forces on these structures

ASSUNTO(S)

colageno non-collagenous proteins collagen suino proteinas extracellular matrix matriz extracelular mitral valve valva mitral proteoglicanos proteoglycan

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