Promising study: new Alzheimer’s therapy should improve memory

Alzheimer’s – also called Alzheimer’s dementia or Alzheimer’s disease – is the most common form of dementia, accounting for about two-thirds of cases. It is an incurable disease of the brain in which nerve cells die over time. As a result, people who develop Alzheimer’s disease become increasingly forgetful, confused and disoriented.

American researchers have now succeeded in stimulating the formation of new nerve cells in the brains of adult mice with Alzheimer’s disease and thus improving memory. This is the conclusion of a study by the University of North Carolina in the US, which was published in the scientific journal Cell Stem Cell.

That certain neurons can renew themselves throughout life is a relatively recent discovery and is referred to as mature neurogenesis. For a long time, scientists assumed that new nerve cells could not arise after the end of childhood.

However, neurogenesis in adults mainly takes place in a small part of the brain – the hippocampus, where memory is also formed. In Alzheimer’s disease, this formation of new nerve cells is disrupted at an early stage, which explains the increasing memory loss in patients.

The research team led by Juan Song has now succeeded in improving the memory performance of mice through two genetic modifications of a specific brain region (supramamillary nucleus).

In the first step, gene therapy stimulated the formation of new brain cells in the hippocampus of the mice. The new gene caused the nerve cells to form a specific visual pigment on their surface. The nerve cells could then be stimulated by a small light probe inserted into the brain. As a result, the number of nerve cells increased.

In the second step, the new nerve cells were activated. This was done via a second gene therapy, in which a specific enzyme multiplies in the nerve cells. This enzyme is essential for memory.

The result: the mice recognized objects in their cage and were less anxious in experiments. This was possible with two different mouse models – ie with two groups of mice in which the animals developed Alzheimer’s disease as a result of different genetic changes.

The treatment had another benefit: the therapy started certain immune cells in the brain, called microglia, to break down harmful protein deposits in the brain (amyloid beta). They are considered the main causative agents of Alzheimer’s disease and other dementias.

The therapy cannot simply be transferred to humans, because the genetic material must be modified for the first step of the therapy. However, studies have shown that neurogenesis still occurs, at least to some extent, in humans as they enter adulthood. The authors of the study therefore hope that a similar effect can be achieved in humans by means of deep brain stimulation, a so-called brain pacemaker. Brain pacemakers have been used successfully for years in Parkinson’s disease.

According to the authors of the study, the second step of the therapy could in principle also be performed in people with Alzheimer’s disease. However, the new therapeutic approach is not yet ready for clinical use in humans. The next step is experiments on larger animals. (t online)