Gene therapy may help cure degenerative brain disorders
the threat of neurological diseases may not persist for long in the wake of scientific advances in gene therapy. Some of the most ambitious research in neurology focuses on replacing cells lost in damaged tissue. This can be achieved by transplanting neurones (nerve cells) or by delivering growth factors -- chemicals that simulate surviving neurones to awaken the cells' dormant ability to regenerate ( Scientific American , Vol 276, No 6).
The reason of slow progress in neurological research is that unlike other cells, neurones in the central nervous system are unable to divide. So the injured nerve tissue of the brain cannot be expected to repair itself.
Recent research has revealed how neurones succumb to various diseases or medical emergencies such as strokes, seizures, and head injuries. Studies suggest that the threatened neurones may be protected by administering drugs or lowering the temperature of the brain. This has raised the possibility of protecting these cells by modifying their genes.
Genes instruct cells to make specific proteins, such as enzymes that catalyse various chemical reactions. These enzymes help neurotransmitters -- substances that carry chemical signals across the tiny gaps between neurones. Gene therapy targeted at failing neurones could provide them with a gene-specific protein that shields the cells from damage.
It is possible to devise methods of administering genes into brain tissue, say Dora Y Ho, a researcher in the department of biological sciences at the Standford University and Robert M Sapolsky, a professor of biological sciences and neuroscience at Standford. A gene containing appropriately coded segments of dna can be directly injected into the brain. But this method is not very successful as neurones are not efficient at picking up such dna . A better alternative is to use a virus. Viruses insert their genetic material into the cells of an infected organism. This added genetic code directs the synthesis of various molecules needed to make new viral particles. Though viruses can prove to be destructive, scientists can tame and convert some of them into microscopic 'Trojan horses'. These viruses can carry a gene and deposit it inside a cell without causing any damage.
For gene therapy in the central nervous system, researchers are focusing on viral types such as adenoviruses (which cause the common cold) and herpes viruses. Experiments with these viral vectors have shown that they can effectively administer a gene into the nerve cells.
Gene therapy for the nervous system can also help patients in overcoming Parkinson's disease. The disease arises after a part of the brain, called substantia nigra , starts degenerating. The destruction of the region makes it hard for a person to initiate movements or execute complex coordinated motion. Gene therapy could immensely benefit those suffering from the debilitating condition. However, it would take a few years for the therapy to have wide ranging applications.
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