Gene Therapy Corrects Defective Genes Causing Genetic Diseases

Gene Therapy
Offers Cure For Many Genetic Diseases

Gene therapy is the most exciting advance in the field of modern medicine practice. Although yet in its infancy, it has shown promising results in some of the genetic disorders.

Therapeutic genetics involves insertion, modification, or removal of genes in an affected individual.

However, there are many ethical, social and legal issues associated with altering an individual’s specific genetic representation.

This makes the human genes modification therapy also the most controversial therapy.

Vectors used as Gene Carriers

Harmless viruses are the carrier (vector) of choice in most of the gene therapies.
There is up coming preference for non-viral gene delivery technique with efficiency similar to those of viruses, and low host immunogenicity.
Stem cells are also being used to achieve desired gene modification.

Single gene mutations are the best candidates for gene replacement therapy, where the mutated nonfunctional gene in a cell is replaced by a normal gene through a vector.

The principle for the safety of gene induction therapy is that the hereditary information moves from genes to body cells (germline cells to somatic cells) and never in the reverse direction.

Any unintentional breach in this principle could jeopardise the safety by spreading to the testes/ovaries and therefore would infect the germline against the intentions of the therapy.

Classification of gene therapy

Germ-line modification therapy
Functional genes are introduced into the human reproductive cells. These new genes then get integrated into the genome of the reproductive cells and the changes incurred can be passed on to the future generations.

This technique mainly targets the carriers of some chronic disorders like Cystic Fibrosis, Parkinsonism and some cancers. This frees the future generation from the dreaded disorders and helps the society at large.
Somatic cells gene modification therapy
Therapeutic genes are transferred to body cells of a patient. Therefore the benefit of the therapy in this procedure is restricted only to an individual.

The modifications achieved are short lived and therefore demands repeated cycles for good clinical results.

Cons of gene therapy

Short-lived nature of the effects of somatic cells gene modification therapy demands multiple cycles of gene manipulation.
Triggered Immune response in the host leads to rejection of foreign gene material introduced. This reduces gene therapy effectiveness. Furthermore, the immune system's enhanced response against the foreign material that it has seen before makes it worse for further cycles of gene therapy in the same host.
Viral vectors have potential risks to the recipient, such as toxicity, immune and inflammatory responses.
Multi-gene disorders are difficult to treat effectively'.
Safety of gene therapy is yet uncertain.
Watch animations on "Problems in Gene Therapy"

i. Insertional Mutagenesis: A chance of inducing tumor

ii. Virus may turn virulent once in the body of recipient.

iii. Unintentional faulty spread of the introduced genes to the recipient’s reproductive cells.

iv. Yet too new.

v. Potential to be misused.

vi. Has excess to personal information.

vii. Can be fatal.

Stem Cells

Ability to preserve stem cells and to culture them when needed has been a great breakthrough in regenerative medicine.

Stem cells have unique capacity for unlimited self renewal. They divide (mitosis) and form large number of well differentiated cells of our body.

This potential of stem cells is used to repair and replenish any damaged or missing cells of the body.

Types of stem cells:

Embryonic stem cells

Controversies surround the use of embryonic stem cells. Moreover, their use can also lead to some undesirable side effects.

Embryonic Stem Cells

High malleability

Potential for undesired development
ex. Teratoma

Infinite life span

Unlimited supply

High ethical burden

Legal controversies associated

Adult Stem Cells

Limited developmental potential

Better behaved and easy to manage

Differentiates in the culture medium after some time

Lose the ability to proliferate after some time

Less moral binding

Less legal controversies

Adult stem cells

There use is less controversial and they have less negative side effects. Own stem cells can be preserved and used in time of necessity. Most successful medical therapies are done with autologous adult stem cells for example bone marrow transplant in Leukemia. They are available both in adults and children.