Direct Cell Reprogramming

Direct Cell Reprogramming-if it could be done-would be like taking any cell in the human body and "hitting rewind," essentially sending that cell's nucleus back to a state which would render the cell "pluripotent", capable of producing any tissue type in the human body, equivalent in versatility to human embryonic stem cells. Furthermore, these stem cells would be genetically matched to the person who donated the body cells. They could then be used to grow tissues for future use in tissue replacement therapies (everything from regeneration of damaged heart tissue to Parkinson's to spinal chord injury) . A perfect genetic match, these tissues w ould not be rejected by the donor's immune system. Most importantly, there would be no embryo created, destroyed, damaged or used in any way at any point in the process.

The basic scientific principle underlying direct cell reprogramming is the fact that the DNA sequence (genome) of different cell types is the same, regardless of the cell type. Thus, skin cells from an adult have the same genome as nerve cells or as embryonic stem cells. The key difference between the cell types is not their DNA sequence, but which parts of the genome are used and which are not. There are an estimated 35,000 genes in the human genome and only 1/3 of these are used in any given cell type. Thus, an almost endless combination of different genes being on and off can be envisioned. The pattern in which genes are turned on and off in a cell is called their epigenetic state. The reversal or "deprogramming" of the epigenetic state of adult cells should allow the generation of embryonic stem cell-like cells that immunologically match a patient and do not require the manipulation or destruction of embryos.