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Cientistas criam embriões híbridos de porcos e humanos

Cientistas criaram pela primeira vez embriões que contém uma combinação de células-tronco de duas espécies grandes e muito diferentes – humanos e porcos -, um passo importante em direção ao desenvolvimento de órgãos para transplante, revela um estudo nesta quinta-feira.

No entanto, a pesquisa ainda está em uma fase muito precoce e mostrou ser mais difícil do que o esperado, relataram os pesquisadores na revista científica Cell.

“Este é um primeiro passo importante”, disse o autor principal, Juan Carlos Izpisua Belmonte, professor do Laboratório de expressão genética do Instituto Salk para Pesquisas Biológicas, na Califórnia.

“O objetivo final é desenvolver tecidos e órgãos funcionais e transplantáveis, mas estamos longe disso”, acrescentou.

Cientistas implantaram células-tronco adultas humanas – conhecidas como células-tronco pluripotentes induzidas – em embriões de suínos e permitiram que elas crescessem por quatro semanas.

Mais de 150 embriões se desenvolveram em “quimeras” – como a mistura humano-animal é conhecida, em referência à figura híbrida da mitologia grega – que eram principalmente suínos, mas com um pequena contribuição humana.

O trabalho envolveu cerca de 1.500 embriões de porcos e levou quatro anos, muito mais tempo do que inicialmente estimado, devido à natureza complicada das experiências.

A ideia de criar misturas entre humanos e animais alimenta controvérsias e levanta questões éticas, particularmente porque os experimentos poderiam teoricamente levar à criação de animais com qualidades humanas, e possivelmente inteligência.

Mas segundo Jun Wu, cientista do Instituto Salk, o nível de contribuição humana para os embriões de porcos foi “baixo” e não incluiu precursores de células cerebrais.

Bruce Whitelaw, professor de biotecnologia animal da Universidade de Edimburgo, que não participou do estudo, descreveu-o como “emocionante” porque este “abre caminho para avanços significativos”.

De acordo com Darren Griffin, professor de genética na Universidade de Kent, o “trabalho também nos ajudará a entender melhor a evolução, o desenvolvimento e as doenças” e pode eventualmente levar a uma solução para a escassez de órgãos.

“Neste estudo, os autores seguiram as diretrizes legais e éticas existentes, permitindo que os embriões se desenvolvessem pelo tempo máximo permitido”, acrescentou.

“É importante que qualquer pesquisa futura seja conduzida com total transparência, de modo a permitir o escrutínio público e o debate”, disse Griffin.

Fonte: Exame

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