Brain cells made from skin cells, bypassing stem cell phase

Mouse skin cells have been converted directly into neural precursor cells (NPCs) which go on to form the major cells in the brain.

In the study, published in PNAS, the scientists from Stanford University School of Medicine in the US skipped the stem cell stage normally required during the process. Having induced the skin cells, called fibroblasts, to become NPCs, the Stanford team were able to grow these cells on to become the three distinct types of brain cell.

Direct conversion of cell types has been achieved several times over recent years but the difference here is the successful conversion to NPCs. As NPCs can be grown in the laboratory into large numbers they are potentially useful should they be used in therapy.

Dr Marius Wernig, who led the research, said he was 'thrilled about the prospects for potential medical use of these cells'.

He added that his team had also shown that the cells could be successfully implanted into the mouse brain and produce a missing protein essential for brain cells to transmit electrical impulses: 'This is important because the mouse model we used mimics that of a human genetic brain disease. However, more work needs to be done to generate similar cells from human skin cells and assess their safety and efficacy'.

NPCs have previously been generated from induced pluripotent stem (iPS) cells, but they were generated with low efficiency and could not self-renew or develop into oligodendrocytes, one of the important brain cell types. In addition, iPS cells can cause cancers when transplanted into animals or humans.

'Direct conversion has a number of advantages', said Ernesto Lujan, the first author of the paper. 'It occurs with relatively high efficiency and it generates a fairly homogenous population of cells. In contrast, cells derived from iPS cells must be carefully screened to eliminate any remaining pluripotent cells'.

A separate team at Stanford University reported on a similar study last year (reported in BioNews 616) but the authors of the PNAS study say that the cell conversion on that occasion may have in fact transiently included the pluripotent stem cell state.