RESUMO
PHOSPHO1 is a phosphoethanolamine/phosphocholine phosphatase that has previously been implicated in generating inorganic phosphate (P(i)) for matrix mineralization. In this study, we have investigated PHOSPHO1 mRNA expression during embryonic development in the chick. Whole-mount in situ hybridization indicated that PHOSPHO1 expression occurred prior to E6.5 and was initially restricted to the bone collar within the mid-shaft of the diaphysis of long bones but by E11.5 expression was observed over the entire length of the diaphysis. Alcian blue/alizarin red staining revealed that PHOSPHO1 expression seen in the primary regions of ossification preceded the deposition of mineral, suggesting that it is involved in the initial events of mineral formation. We isolated MVs from growth plate chondrocytes and confirmed the presence of high levels of PHOSPHO1 by immunoblotting. Expression of PHOSPHO1, like TNAP activity, was found to be up-regulated in MVs isolated from chondrocytes induced to differentiate by the addition of ascorbic acid. This suggests that both enzymes may be regulated by similar mechanisms. These studies provide for the first time direct evidence that PHOSPHO1 is present in MVs, and its developmental expression pattern is consistent with a role in the early stages of matrix mineralization.
Assuntos
Desenvolvimento Ósseo/genética , Matriz Óssea/metabolismo , Osso e Ossos/metabolismo , Calcificação Fisiológica/genética , Monoéster Fosfórico Hidrolases/genética , Animais , Desenvolvimento Ósseo/fisiologia , Matriz Óssea/embriologia , Matriz Óssea/crescimento & desenvolvimento , Osso e Ossos/embriologia , Calcificação Fisiológica/fisiologia , Embrião de Galinha , Galinhas , Condrócitos/citologia , Condrócitos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação Enzimológica da Expressão Gênica/genética , Immunoblotting , Hibridização In Situ , Modelos Biológicos , Monoéster Fosfórico Hidrolases/metabolismo , Fatores de TempoRESUMO
Osteochondrosis/osteoarthrosis (OC/OA) are common terms for various joint pathologies that occur in pigs. Pathologies that may contribute to these disorders have been described, but the primary cause(s) remain unknown. We hypothesised that as OC has some similarities to dyschondroplasia, which involves a failure of growth plate chondrocytes to fully differentiate and hypertrophy, treatment with 25-hydroxyvitamin D3 (25-D) might reduce the incidence and/or severity of lesions in pigs, as it does in chickens with dyschondroplasia. Control pigs were fed a commercial diet ad libitum. In the treated group this diet was supplemented with 25-D at 0.1 mg/kg. Ten pigs from each of the control and treated groups were sampled at 7, 12, 16 and 21 weeks. Treatment with 25-D had no effect on the incidence or severity of OC/OA lesions. Cartilage dry weight, total collagen content and proteoglycan content, and plasma levels oftotal calcium, inorganic phosphorous, vitamin C, insuline-like growth factor-I, parathyroid hormone and tumour necrosis factor alpha were unaffected by treatment. In addition, none of these parameters were correlated with the incidence or severity of OC/OA lesions. The mRNA expression levels of 21 out of 23 genes assayed by RT-PCR were unaltered in articular cartilage from OA lesion samples as compared to normal articular cartilage. However, collagen type II was reduced and collagen type X increased in OA lesion and near lesion samples. These results suggest that OA in pigs may share some features of osteoarthritis in other mammalian species.