RESUMO
Phenylketonuria (PKU) is a metabolic genetic disease characterized by deficient phenylalanine hydroxylase (PAH) enzymatic activity. Brain hypomyelination has been reported in untreated patients, but its mechanism remains unclear. We therefore investigated the influence of phenylalanine (Phe), phenylpyruvate (PP), and phenylacetate (PA) on oligodendrocytes. We first showed in a mouse model of PKU that the number of oligodendrocytes is not different in corpus callosum sections from adult mutants or from control brains. Then, using enriched oligodendroglial cultures, we detected no cytotoxic effect of high concentrations of Phe, PP, or PA. Finally, we analyzed the impact of Phe, PP, and PA on the myelination process in myelinating cocultures using both an in vitro index of myelination, based on activation of the myelin basic protein (MBP) promoter, and the direct quantification of myelin sheaths by both optical measurement and a bioinformatics method. None of these parameters was affected by the increased levels of Phe or its derivatives. Taken together, our data demonstrate that high levels of Phe, such as in PKU, are unlikely to directly induce brain hypomyelination, suggesting involvement of alternative mechanisms in this myelination defect.
Assuntos
Bainha de Mielina/patologia , Oligodendroglia , Fenilalanina Hidroxilase/genética , Fenilalanina/farmacologia , Fenilcetonúrias , Animais , Células Cultivadas , Corpo Caloso/metabolismo , Corpo Caloso/patologia , Modelos Animais de Doenças , Óperon Lac , Camundongos , Camundongos Mutantes , Camundongos Transgênicos , Proteína Básica da Mielina/genética , Proteína Básica da Mielina/metabolismo , Bainha de Mielina/metabolismo , Oligodendroglia/citologia , Oligodendroglia/efeitos dos fármacos , Oligodendroglia/metabolismo , Fenilalanina/metabolismo , Fenilalanina Hidroxilase/metabolismo , Fenilcetonúrias/metabolismo , Fenilcetonúrias/patologia , Fenilcetonúrias/fisiopatologia , Regiões Promotoras Genéticas/fisiologia , Ratos , Ratos WistarRESUMO
Mesenchymal stem cells (MSCs) are studied as a cellular source for the treatment of various diseases. In this work, we isolated and cultivated murine bone marrow-derived MSCs. After a first observation of a solid tumor in a mouse injected with these cells, we systematically explored their chromosomal stability. We observed in all the cytogenetically analyzed cases gross chromosomal alterations every time the MSCs went through the senescence crisis while the lymphocytes from the same animals showed a normal chromosome count. This observation was confirmed in different mouse strains, with different culture protocols, and even in short-term cultures after a hematopoietic cell negative immunodepletion performed in order to accelerate the isolation procedure. Therefore, we conclude that murine MSCs display high chromosomal instability and can generate tumors, and that care must be taken before using them for the evaluation of MSC therapeutic potential.