CÉLULA DA PELE É TRANSFORMADA EM NEURÔNIO

Segunda-feira, 30 de maio de 2011 - 12h18



SÃO PAULO – Quatro proteínas. Isso foi tudo o que os pesquisadores da Universidade de Stanford precisaram para converter células da pele humana em neurônios.

O feito é significativo, pois elimina a necessidade de se criar primeiro as chamadas células tronco pluripotentes induzidas (iPS) e facilita a fabricação de neurônios em laboratório.


Com isso, os pesquisadores chegam cada vez mais perto de imitar doenças cerebrais ou neurológicas in vitro e, quem sabe um dia, usar esse material para terapias humanas.
A pesquisa é paralela a uma já feita em 2010 pelos próprios pesquisadores de Stanford, na qual células da pele de ratos foram transformadas em neurônios. O sucesso com os roedores fez os cientistas aplicarem uma técnica parecida nas células humanas, cuja primeira etapa foi converter células tronco embrionárias em neurônios. Isso foi feito por meio de uma combinação de proteínas (Brn2, Ascl1 e Myt1l), um tratamento que recebeu o nome de BAM. O mesmo processo funcionou em células tronco pluripotentes induzidas.
O próximo passo foi o grande desafio: fazer o mesmo com células epiteliais. Utilizando células já maduras da pele de fetos e recém nascidos, os pesquisadores descobriram que o tratamento BAM as fazia ficar bastante parecidas com neurônios, porém estes eram incapazes de gerar sinais elétricos e se comunicar. Foi então adicionada uma quarta proteína, a NeuroD; com a nova combinação, as células epiteliais se transformaram em neurônios funcionais em quatro a cinco semanas. Além de expressarem atividade elétrica, eles se integraram e interagiram com neurônios de rato criados nas placas do laboratório.
A pesquisa, embora significativa, ainda possui limitações se comparada à feita com roedores em 2010. Cerca de 20% das células da pele de ratos podem virar neurônios, contra somente 2% a 4% das humanas.  Além disso, em humanos, os neurônios criados a partir de células epiteliais levam mais tempo para se formar e emitem sinais mais fracos.


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