Gene Therapy: Mechanisms, Types, and Medical Applications

What is Gene Therapy?

Gene therapy is a technique that involves the replacement of defective genes with healthy ones to treat genetic disorders. It is an artificial method that introduces DNA into the cells of the human body. The first successful gene therapy was accomplished in the year 1989.

In the figure, the cell with the defective gene is injected with a normal gene, which aids in the normal functioning of the cell. This technique is employed mainly to fight against diseases in the human body and also to treat genetic disorders. Damaged proteins in the cell are replaced by the insertion of DNA into that cell. Generally, improper protein production in the cell leads to diseases. These diseases are treated using gene therapy techniques. For example, cancer cells contain faulty cells that differ from normal cells and possess defective proteins. Hence, if these proteins are not replaced, this disease would prove to be fatal.

Types of Gene Therapy

Basically, there are two main types of gene therapy:

Somatic Gene Therapy

This type usually occurs in the somatic cells of the human body. It relates to a single person, and only the person who has the damaged cells will receive the replacement with healthy cells. In this method, therapeutic genes are transferred into the somatic cells or the stem cells of the human body. This technique is considered one of the safest methods of gene therapy.

Germline Gene Therapy

It occurs in the germline cells of the human body. Generally, this method is adopted to treat genetic, disease-causing variations of genes that are passed from parents to their children. The process involves introducing healthy DNA into the cells responsible for producing reproductive cells, eggs, or sperm. Germline gene therapy is not legal in many places as the risks often outweigh the potential rewards.

Applications of Gene Therapy

Gene therapy can potentially offer a long-term treatment benefit with just one dose for some patients. Some of the applications and the diseases targeted include:

Genetic Disorders

• It is used to address genetic conditions like ADA-SCID, haemophilia, muscular dystrophy, sickle cell anaemia, and retinitis pigmentosa.
• Replacing defective genes with functional copies offers significant treatment hope.

Cancer

• Genes manipulating the immune system, such as CAR-T therapy, are being applied against cancers.
• Other applications include inhibiting tumour growth promoters, targeting cancer-specific antigens, and stopping angiogenesis.

Neurodegenerative Diseases

• Delivering nerve growth factors through gene therapy is being trialed for Alzheimer’s, Parkinson’s, and Amyotrophic Lateral Sclerosis (ALS).
• Gene-edited stem cell therapy also holds promise for these conditions.