Gene therapy is the treatment of genetic disorders by replacing, altering or supplementing a gene that is absent or abnormal and whose absence or abnormality is responsible for the disease. Types of gene therapy:
(a) Germ line gene therapy:
1. In this germ cells are modified genetically to correct a genetic defect.
2. Normal gene is introduced into germ cells like sperms, eggs, early embryos.
3. It allows transmission of the modified genetic information to the next generation.
4. Although it is highly effective in treatment of the genetic disorders, its use is not preferred in human beings because of various technical and ethical reasons.
(b) Somatic cell gene therapy:
1. In this somatic cells are modified genetically to correct a genetic defect.
2. Healthy genes are introduced in somatic cells like bone marrow cells, hepatic cells, fibroblasts endothelium and pulmonary epithelial cells, central nervous system, endocrine cells and smooth muscle cells of blood vessel walls.
3. Modification of somatic cells only affects the person being treated and the modified chromosomes cannot be passed on the future generations.
4. Somatic cell gene therapy is the only feasible option and the clinical trials have already employed for the treatment of disorders like cancer, rheumatoid arthritis, SCID, Gaucher’s disease, familial hypercholesterolemia, haemophilia, phenylketonuria, cystic fibrosis, sickle-cell anaemia, Duchenne muscular dystrophy, emphysema, thalassemia, etc.
