THE PATTERN OF FIBRILLIN DEPOSITION CORRELATES WITH MICROFIBRIL-ASSOCIATED GLYCOPROTEIN 1 (MAGP-1) EXPRESSION IN CULTURED BLOOD AND LYMPHATIC ENDOTHELIAL CELLS

Abstract

Fibrillins constitute the major structural components of 10-12nm microfibrils of theextracellular matrix of several elastic and non elastic tissues and of initial lymphatic vesselanchoring filaments. Microfibril-Associated Glycoprotein-1 (MAGP-1) binds fibrillin totropoelastin during elastogenesis. We recently reported that cultured blood endothelial cellsdeposit fibrillin in a honeycomb pattern, whereas lymphatic endothelial cells form an irregularweb. The aim of this immunohistochemical study was to verify whether the deposition pattern offibrillin is related to the expression of MAGP-1 in confluent and post-confluent cultures ofbovine aortic (AEC), pulmonary artery (PAEC) and lymphatic endothelial cells (LEC). In AECand PAEC, MAGP-1 and fibrillin co-localized and their deposition increased with time inculture. In AEC, both proteins formed a honeycomb pattern. In LEC, MAGP-1 deposition wasstill negligible when fibrillin formed an irregular web covering the entire surface. PAEC, whichin vivo are exposed to physiological conditions intermediate between AEC and LEC, had anintermediate pattern of deposition of fibrillin and MAGP-1. Assuming that early elastogenesis isan intrinsic functional need for the aorta but not for the thoracic duct, we propose that delayedappearance of MAGP-1 in LEC may correlate with their irregular fibrillin deposition. Differentfibrillin scaffolds could in turn account for the specificity of elastic fibers in compliance with thespecific functional requirements of the tissue.