Data/hora: 09/06/2024 06:38:36

Provedor de dados: | 56
País: | Brazil
Título: | Contribution of matrix vesicles and alkaline phosphatase to ectopic bone formation
Autores: | Ciancaglini,P.; Simão,A.M.S.; Camolezi,F.L.; Millán,J.L.; Pizauro,J.M.
Data: | 2006-05-01
Ano: | 2006
Palavras-chave: | Matrix vesicles; Endochondral ossification; Osseous plate; Alkaline phosphatase; Ectopic mineralization; Calcification.
Resumo: | Endochondral calcification involves the participation of matrix vesicles (MVs), but it remains unclear whether calcification ectopically induced by implants of demineralized bone matrix also proceeds via MVs. Ectopic bone formation was induced by implanting rat demineralized diaphyseal bone matrix into the dorsal subcutaneous tissue of Wistar rats and was examined histologically and biochemically. Budding of MVs from chondrocytes was observed to serve as nucleation sites for mineralization during induced ectopic osteogenesis, presenting a diameter with Gaussian distribution with a median of 306 ± 103 nm. While the role of tissue-nonspecific alkaline phosphatase (TNAP) during mineralization involves hydrolysis of inorganic pyrophosphate (PPi), it is unclear how the microenvironment of MV may affect the ability of TNAP to hydrolyze the variety of substrates present at sites of mineralization. We show that the implants contain high levels of TNAP capable of hydrolyzing p-nitrophenylphosphate (pNPP), ATP and PPi. The catalytic properties of glycosyl phosphatidylinositol-anchored, polidocanol-solubilized and phosphatidylinositol-specific phospholipase C-released TNAP were compared using pNPP, ATP and PPi as substrates. While the enzymatic efficiency (k cat/Km) remained comparable between polidocanol-solubilized and membrane-bound TNAP for all three substrates, the k cat/Km for the phosphatidylinositol-specific phospholipase C-solubilized enzyme increased approximately 108-, 56-, and 556-fold for pNPP, ATP and PPi, respectively, compared to the membrane-bound enzyme. Our data are consistent with the involvement of MVs during ectopic calcification and also suggest that the location of TNAP on the membrane of MVs may play a role in determining substrate selectivity in this micro-compartment.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2006000500006
Editor: | Associação Brasileira de Divulgação Científica
Relação: | 10.1590/S0100-879X2006000500006
Formato: | text/html
Fonte: | Brazilian Journal of Medical and Biological Research  v.39 n.5 2006
Fonte: | info:eu-repo/semantics/openAccess