27 February 2012

Dr Lux Fatimathas By

Appeared in BioNews 646

Researchers in the US have used gene therapy to reduce the severity of seizures in a rat model of epilepsy.

The gene injected into the rats codes for somatostatin, a hormone that is normally found at lower levels in people with epilepsy. Levels of this hormone in the brain have been shown to drop during an epileptic seizure.

The findings may help in the development of new therapies targeting the prevention of epileptic seizures, potentially benefiting people with epilepsy who do not respond to current methods of drug treatment.

'For years people have focused only on treating the disease, not preventing the disease', said Professor Paul Carney of the University of Florida's School of Medicine and lead author of the study. 'Gene therapy, as well as other forms of treatment, is emerging, and there is the hope and promise they will offer more effective and novel treatments for people with drug-resistant epilepsy'.

Over 450,000 people in the UK have epilepsy, a condition where the electrical impulses between nerve cells become disrupted, often resulting in seizures. The most common form of this condition is temporal lobe epilepsy (TLE), and around 30 percent of patients with TLE do not respond to conventional drug treatment. It was this variant of the disease which was mimicked in the rats in this experiment.

The gene for somatostatin was encoded in a harmless virus before being injected into the hippocampus, a region of the brain. The hippocampus contains many somatostatin-producing nerve cells.

Following the injection, electrical stimulations were used to induce seizures in the rats. The gene injections enabled scientists to reduce both the duration and strength of the seizures. None of the rats that received the injections suffered the highest level of seizure and the therapy seemed to work without producing any notable negative side effects.

'Being able to restore somatostatin up to normal levels allows the brain to heal itself and that is the idea here. We're putting something back in that is normally there and allowing the brain to pick it up as part of its normal machinery. We're not putting in a drug', said Professor Carney.

Extensive further research is required before any similar therapy could be used in humans. Among other challenges, scientists would need to find a suitable method to deliver the gene to the brain. There is also the question of where in the brain to target the hormone.

Dr Edward Bertram of the University of Virginia, who was not involved in the study, pointed out that 'What effect a compound is going to have partly depends on where in the seizure circuit that new compound or gene is being placed – where should we be putting this to have the best effect?' Nonetheless, Dr Bertram called the study 'a great first step'.

This study was published in the journal Neuroscience Letters.