Somatic cell therapy and Germ line therapy

In somatic cell therapy, healthy gene is introduced into the somatic cells.

somatic cell therapy

Somatic cell therapy is of 4 types

1) Embryo therapy or foetal gene therapy: Here healthy remedial gene is introduced into cells of 2-10 days old embryo.

The method was developed by Handyside et al for treating cysytic fibrosis a single gene defect due to mutation in CFTR gene. He constructed remedial gene by rDNA technology and introduced into a cell of 8 celled embryo. This recombinant cell is reimplanted back into the uterus of the women. The resulting baby was free from cystic fibrosis.

2) Ex Vivo therapy, transplantation or tissue grafting:

In this method, the cells, tissues or organ is removed from the patient, cultured in vitro, tranfected with remedial gene and placed back into the body. This method is promising in treating inherited blood diseases like Haemophilia.

Examples include

• bone marrow transplantation
• Liver transplantation
• Kidney transplantation
• Bone marrow transplantation

3) In vivo gene therapy:

Here the healthy gene is directly delivered into the proper organ of the patient to correct the genetic defect.

Alizheimers disease, Duchenne muscular dystrophy are the candidate diseases for this method.

Adeno virus vector

Viral delivery systems like Adeno virus and Herpes simplex virus are generally used.

4) Antisense therapy or gene inhibition therapy:

The method of treating genetic diseases by introducing a remedial gene that prevents the expression of a specific defective gene.

This method is especially useful for the treatment of cancer where the reason is over expression of some genes.

Liposomes

Common gene transfer methods for targeting genes to target cells

• Microinjection
• Elecroporation
• Calcium phosphate mediated transfection
• Use of retroviral vectors
• Liposome mediated gene transfer

In germ line therapy, healthy genes are introduces to the germ cells like sperm, egg or zygote.

Here, fertilized egg is provided with the correct version of the defective gene and reimplanted back into the mother. If successful, the resulting individual has the correct gene in whole cells. This is usually carried out by microinjection of DNA into the isolated egg cell. Theoretically, this method is highly promising and could treat any inherited disease, but practically not so.