RESUMO
Activin A is a growth factor released by mature osteoblasts that has a critical effect on bone formation. We investigated the effect of bone morphogenetic protein (BMP)-4 on activin A gene expression during in vitro osteogenic differentiation of mouse embryonic stem (ES) cells. Embryoid bodies were cultured in retinoic acid (RA) for three days and then without RA for two days. Seeded cells received osteogenic medium with ß-glycerophosphate, L-ascorbic acid 2-phosphate and dexamethasone during 19 days, with or without BMP-4. Six independent experiments were carried out. Real-time PCR was used to detect gene expression of activin A, Oct-4, Nanog, osteocalcin, RUNX2 and bone alkaline phosphatase. Immunofluorescence was used to co-localize activin A with the undifferentiation marker stage-specific embryonic antigen 1. Cells treated with BMP-4 had an increased gene expression of activin A, osteocalcin and bone alkaline phosphatase (p < 0.05). In conclusion, BMP-4 increases activin A gene expression during mouse ES cell differentiation into bone precursors.
Assuntos
Ativinas/metabolismo , Proteína Morfogenética Óssea 4/farmacologia , Regulação da Expressão Gênica no Desenvolvimento , Células-Tronco Embrionárias Murinas/citologia , Osteogênese/efeitos dos fármacos , Animais , Ácido Ascórbico/administração & dosagem , Ácido Ascórbico/análogos & derivados , Diferenciação Celular , Meios de Cultura , Primers do DNA/genética , Dexametasona/química , Fibroblastos/metabolismo , Glicerofosfatos/química , Camundongos , Microscopia de Fluorescência , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Tretinoína/químicaRESUMO
The technique of body composition by dual-energy X-ray absorptiometry (DXA) has been used for several years in the research environment. Its ability to accurately and precisely measure lean, fat, and mineral composition in various body compartments has been well validated. Furthermore, the technique is widely available to clinical patients on existing DXA instruments throughout the world through the use of specific software packages and scanning algorithms. There have been few clear statements regarding the clinical indications for body composition measurement in patients outside the research setting. This is in part because of the lack of specific documented interventions that would be affected by body composition test results, beyond usual clinical advice. We have examined a few of the most common, specific scenarios (HIV therapy, sarcopenia, bariatric surgery, obesity) and proposed indications for body composition assessment. We have also discussed contraindications to body composition testing.