Stem cells introduced

The in vitro approach entails initial removal of the target cells from the body. These are then cultured in vitro and incubated with a vector containing the nucleic acid to be delivered. The genetically altered cells are then re-introduced into the patient s body. This approach represents the most commonly adopted protocol to date. In order to be successful, however, the target cells must be relatively easy to remove from the body and reintroduce into the body. Such in vitro approaches have successfully been undertaken, utilizing various body cell types, including blood cells, stem cells, epithelial cells, muscle cells and hepatocytes. 

Last, the surgical procedures such as keratoprosthe-sis [24] surgery and comeal and limbal transplantations are on the way to be developed. Yet, the transfer of cultured stem cells is a problem due to the need of mouse-derived feeder cells these might introduce new risks of disease transfer. Until those problems are not solved, these techniques are not applicable on humans, but these problems are likely to be solved in the near future [25]. 

The best demonstration that the loss of active normal p53 explains the oncogenic behavior of mutant p53 comes from studies in which a null mutation was introduced into the gene by homologous recombination in murine embryonic stem cells. Mice homozygous for the null allele appear to be normal but are prone to the development of a variety of neoplasms by 6 months of age. These observations suggest that a normal p53 gene is dispensable for embryonic development but that its absence predisposes the animal to neoplastic disease. 

Toneguzzo F, Keating A (1986), Stable expression of selectable genes introduced into human hematopoietic stem cells by electric field-mediated DNA transfer, Proc. Natl Acad. Sci. USA 83 3496-3499. 

In a recent study, scientists directed mouse embryonic stem cells to differentiate into DA neurons by introducing the gene Nurr 1. When transplanted into the brains of a rat model of Parkinson s disease, these stem cell-derived DA neurons reinnervated the brains of the mouse Parkinson s disease model, released dopamine, and improved motor function. 

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