The newly introduced genes will encode proteins and correct the deficiencies that occur in genetic diseases. Thus, gene therapy primarily involves genetic manipulations in animals or humans to correct a disease and keep them healthy.
There are two approaches to achieve gene therapy.
- Somatic cell gene therapy.
The cells which lack the capacity to reproduce are known as somatic cells. There are the cells of an organism other than egg cells. Examples are skin cells, bone marrow cells, blood cells etc. Somatic cell gene therapy involves the insertion of a fully functional and expressible gene into a target somatic cell to correct a genetic disease permanently.
- Germ cell gene therapy.
The reproductive cells of an organism constitute germ cell line. Gene therapy involving the introduction of DNA into germ cells is passed on to the successive generations. For ethical reasons germ cell gene therapy is presently not attempted.
So somatic gene cell therapy is currently studied and applied extensively with an ultimate objective of correcting human diseases. There are two types of gene therapies.
- Ex vivo gene therapy.
This involves the transfer of genes in cultured cells for example come narrow cells, which are them reintroduced into the human body to correct genetic diseases like sickle cell anaemia. The procedure basically involves the use of the patients own cells for culture and genetic correction and then their return back to the patient. Ex vivo gene therapy is efficient only if the remedial gene is stably incorporated and continuously expressed. This can be achieved by use of vectors.
2. In vivo gene therapy.
The direct delivery of genes into the cells of a particular tissue is referred to as in vivo gene therapy. Many tissues are potential candidates for this approach. These include liver, muscle, spleen, lung, brain and blood cells. Gene delivery can be carried out by viral or non viral vector systems. The success of this therapy is based on the efficiency of the uptake of remedial gene by target cells and the expression capability of the gene. Also the intra cellular degradation of the gene and its uptake by nucleus.