What Is Germ Line Gene Therapy?

Gene therapy refers to the introduction of foreign normal genes into target cells to correct or compensate for diseases caused by defective and abnormal genes to achieve therapeutic purposes. This also includes the application of transgene technology, that is, inserting foreign genes into the appropriate recipient cells of patients through gene transfer technology, so that the products made by foreign genes can treat a certain disease. Broadly speaking, gene therapy can also include measures and new technologies to treat certain diseases from the DNA level.

Gene therapy

(Medical Terminology)

Gene therapy refers to the introduction of foreign normal genes

1. Gene transfer method

(1) Isolation and cloning of specific normal genes: application

Gene therapy for tumors

Gene therapy for AIDS

Gene therapy for genetic diseases

Gene therapy research generally meets the following requirements

is a single-gene deficiency disease that has been identified;

Limited to somatic cells;

affinity and operability of target cells;

Have obvious curative effect and no or low harm;

The expression level is stable for a long time;

Must have animal experimental basis.

Clinical trials of human cellular gene therapy have begun. The following conditions must be met for gene therapy:

Select the appropriate disease, and understand its pathogenesis and the structural function of the corresponding gene;

The gene to correct the disease has been cloned, and understand the mechanism and conditions of the gene expression and regulation;

The gene has suitable recipient cells and can be effectively expressed in vitro;

Have safe and effective transfer vectors and methods, and available

In 1991, Chinese scientists conducted the world's first clinical trial of gene therapy for hemophilia B. At present, 4 patients with hemophilia have received gene therapy. After treatment, the concentration of factor IX in the body increased, bleeding symptoms reduced, and safety was achieved Effective treatment effect. Subsequently, our scientists used

1. Stable and efficient expression of introduced genes

The first is related to the transfer method. Chemical and physical methods introduce inefficient genes and poor natural expression. The selection of appropriate recipient cells is also for the stable and efficient expression of introduced genes. Bone marrow is used the most as a recipient cell. Retroviral vector-mediated genes can only infect cells in the dividing state. Therefore, treatment such as 5-FU can be used to enhance cell division, and infection with viral particles containing the target gene can achieve better results. Therefore, bone marrow cell culture, stem cell purification, and the use of hematopoietic factors during culture can increase stable and efficient gene expression.

2. The safety of gene introduction The safety of gene therapy should ensure that no new harmful genetic variation is caused by the introduction of a foreign gene of interest, which is caused by the use of retroviral vectors. Therefore, a relatively safe retroviral vector should be constructed. As for the insertion mutation that may inactivate an important gene or more severely activate a proto-oncogene, it is still unclear how dangerous the problem is, but practice so far has shown that no obvious serious problems have been seen.

In order to carry out gene therapy safely and effectively, the implementation of any plan must be approved and implemented by the relevant administrative department in accordance with strict technical procedures and standards.

Related to safety is germ cell gene therapy. Although it has not been implemented in humans, it has been successful in animal experiments, and this is the emergence of transgenic animals. This fact not only brings hope to human germ cell gene therapy, but also makes people worry that this genetic change will be passed down from generation to generation, and it will bring good or bad to humans. As a result, many scientists are not only cautious, but also objectionable, which is the potential danger of gene therapy.

3 Gene therapy and social ethics. Somatic cell gene therapy is ethical, but trying to correct genetic defects in germ cells or changing the genetic characteristics of normal people through genetic engineering is a controversial area. Historically, scientific inventions and creations have had a profound impact on human survival and development, so genetics has developed to this day, and gene therapy can be performed, which should be said to be ethical. The important issue is to get the understanding and cooperation of society. The first is the cooperation of patients and their relatives. Therefore, it is necessary to publicize the science and safety of gene therapy and the importance of human health in order to raise people's awareness. At the same time, it is necessary to establish and improve the medical legal system and measures.

For safety reasons, prior to clinical trials, three basic requirements must be met in animal research: foreign genes can be introduced into target cells and maintained long-term and effective; the genes should be expressed in cells at sufficient levels; the Genes should be harmless to cells.

History of gene therapy

(1) In 1962, Szybalski and other human DNA were used to transform human cells, and Ca2 was found to stimulate the transfer of DNA into cells. This was the first step for the artificial transfer of genetic material.

(2) In 1967, Nirenberg proposed that genetic engineering should be used for human gene therapy.

(3) In 1968, Burnett et al. Introduced the virus into cultured cells by DEAE synergistic transfer method.

(4) In 1972, Grahant et al. Carried out a detailed study of calcium phosphate-mediated DNA transfer, making this technology generally accepted and applied.

(5) In the early 1970s, Graessman and Dicumak laid the foundation for transferring genes by microinjection.

(6) In 1973, American scientists and several doctors conducted the first gene therapy experiment in Germany. The patients were a pair of sister researchers who lacked a rare enzyme in the body. The researchers injected a patient with a virus that can restore the patient's own enzyme secretion, the Chopped papilloma virus. The experiment had no effect and no side effects.

(7) In 1980, American doctors performed gene therapy on two patients with severe thalassemia, but also failed.

(8) In 1988, the National Institutes of Health's Recombinant DNA Advisory Committee approved the implementation of the introduction of marker genes into tumor-infiltrating lymphocytes for the first time. The result is harmless to the patient. Gene therapy is gradually lifted.

(9) In September 1990, researchers transferred the rod dehydrogenase gene into patients, and the symptoms were significantly relieved and the treatment was successful.

(10) In 1991, researchers at Fudan University in China carried out the "fibroblast gene therapy for hemophilia B" project. In addition, they also carried out gene therapy for tumors and blood diseases.

(11) In September 2000, an 18-year-old young man died of gene therapy in Philadelphia, USA. The US "Science" magazine has successively published reports that the US Food and Drug Administration (FDA) has temporarily banned a university from conducting gene therapy trials.

(12) As of July 2005, 1076 clinical trials of gene therapy have been approved worldwide, of which 66% are for cancer treatment.

After more than ten years of development, many advances have been made in gene therapy research. However, they are still in the early stages of clinical trials, and stable efficacy and safety cannot be guaranteed. Despite many obstacles, the trend of gene therapy is still encouraging. Perhaps as the founders of gene therapy say, gene therapy is the new technology that will drive the 21st century medical revolution. ^[2-3]