Types of Gene Therapy

Types of Gene Therapy Explained

Gene therapy inserts genes into cells and tissues in order to treat diseases. It is mainly used for hereditary diseases. The inserted genes may seek to alter or replace faulty genes that are
responsible for the disease. There are two types of gene therapy; somatic gene therapy
(gene therapy that is used on adult cells) and germline gene therapy (gene therapy that targets egg and sperm cells).


Somatic - A Unique Type of Gene Therapy

Somatic gene therapy treats somatic cells by inserting an agent containing a modified gene (known as a vector) into a person's body. Somatic cells are cells that form the body and cannot produce offspring. Gene therapy, in its present stage, only treats somatic cells in humans. There are two types of somatic gene therapy, ex vivo and in vivo. Ex vivo modifies cells outsides the body and then transplants them back into the body. In vivo changes the cells while they are still in the body; Somatic gene therapy does not affect any offspring of the person being treated.


Applications of Somatic Gene Therapy

Somatic gene therapy has been used to treat genetic diseases and disorders. Scientists first used gene therapy on single-gene defects, like cystic fibrosis, hemophilia, muscular dystrophy, sickle cell anemia and ADA deficiency. Theoretically, these various types of gene therapy could be used to treat any disease that is caused from gene disorders. Some of the diseases that have been mentioned as possible candidates for somatic gene therapy include cancer, AIDS, Alzheimer's diseases, Lou Gehrig's disease, cardiovascular disease and arthritis.


Regulations in Somatic Gene Therapy

Legislation regarding somatic gene therapy varies from country to country and from state to state. Some countries limit the use of gene therapy to certain diseases, including diseases that may not be cured with other methods and that may cause an early death. Some countries require that any research that takes place follow certain regulations, including the establishment of committees and organizations to monitor. Many countries will require research to be approved by national or state committees that have been established to deal with somatic gene therapy research.

The use of somatic gene therapy is also usually subject to regulations, including approval by a committee set up for this purpose. Committees will often look at the probably benefits and harms. They will also ensure that the public is advised of any new research and applications and listen to their views on the subject.

Morals and ethics play an important role when it comes to certain types of gene therapy. Somatic gene therapy is not as affected by ethics when compared to the germline gene therapy. As somatic gene therapy only treats body cells, instead of reproduction cells, many people believe it does not compromise ethics as much as germline gene therapy, which treats egg and sperm cells and has the ability to affect future generations. However, there are some ethical concerns. Ethical standards vary from country to country. Some ethical organizations have released recommendations. These recommendations include:
Establishing a national ethics body in each country to look at somatic gene therapy;
Supporting somatic gene therapy research that follows the recommendations;
Asking researchers, organizations and governments to listen and respond to public concerns about gene therapy research;
Asking that research follow quality and safety controls.


Germline Gene Therapy

Germline gene therapy involves making changes to the cells that are used in the reproductive process. Germline gene manipulation can change sperm cells, oval or stem cells
precursors. In order for germline therapy to produce changes that will be transmitted to
offspring, the genes need to be inserted into chromosomes. Germline therapy has so far mainly been used in animals.

Germline Genetic Engineering and Specially Altered Animals

Germline genetic engineering has been used successfully to specially alter animals. When altered cells are implanted in a surrogate mother, the two types of cells in the hybrid blastocyst contribute to the final animal. This has been used to produce animals such as cows with elevated milk production, sheep that secrete a valuable hormone or enzyme in the udder, mice that have specific genes inactivated in order to analyze the gene's function and mice with a genetically engineered deficiency that is similar to human diseases.


Ethical Considerations in Germline Gene Therapy

Out of the two types of gene therapy, germline gene therapy poses the most ethical problems. Many people protest against the use of germline gene therapy in all scenarios, and the use of germline gene therapy moral in humans is a very contentious issue. Some people want this technology to be used in humans, so that certain diseases may be eradicated. Others believe that this sets some people up as "playing God" and opens the way to many future problems, including "designer babies" and the rejection of certain normal traits. It has only provoked questions about how it should be used and when it is ethical to use germline gene therapy. Germline gene therapy institutes are concerned with the ethical problems relating to germline gene therapy.

Differences between Somatic and Germline Gene Therapy

There is one main difference between somatic and germline gene therapy. Somatic gene therapy alters body cells and has no effect on the reproduction cells or any future offspring. Germline gene therapy, on the other hand, targets cells of the reproductive system and can be used to change the cells of future generations. Both types of gene therapy have ethical considerations.