A group of Spanish researchers, including Dr. Maria Blasco and others at the CNIO, have published a new study that examines the consequences of short telomeres and telomerase deficiency on the brain [1].

This study addresses an aspect of telomere attrition, one of the primary hallmarks of aging. Telomeres are repeating sequences of DNA (TTAGGG) that can can reach a length of 15,000 base pairs and appear at the ends of chromosomes, acting as protective caps. They prevent damage, stop chromosomes from fusing with each other, and prevent chromosomes from losing base pair sequences at their end during cell replication.

The past year or so has seen an energetic debate over whether or not new neurons are generated in the adult human brain, a process known as neurogenesis. This process is well known and well studied in mice, and thought to be very important in the resilience and maintenance of brain tissue. The human data has always been limited, however, due to the challenges inherent in working with brain tissue in living people, and it was assumed was that the mouse data was representative of the state of neurogenesis in other mammals. In this environment, the publication of a careful study that seemed to rule out the existence of neurogenesis in adult humans produced some upheaval, and spurred many other teams to assess the human brain with greater rigor than was previously the case.

So far, all of the following studies published so far do in fact show evidence of adult neurogenesis in humans. This is the better of the two outcomes, as the regenerative medicine community has based a great deal of work on the prospect of being able to upregulate neurogenesis in order to better repair injuries to the central nervous system, or partially reverse the decline of cognitive function in the aging brain. The study here is particularly reassuring, as it shows that even in very late life there are signs that new neurons are being generated in the brain.

Imagine a simple and effective treatment for restoring the sense of smell in people who have lost it or never had it in the first place – that could one day be possible as a result of early stage research on mice, in which olfactory nerves were replenished using stem cells.

Using droplets of globose basal cells – the same cells that naturally replace damaged and ageing neurons related to smell – scientists were able to get them to develop into full nerve cells, stretching right into the brain.

Ultimately a few squirts of stem cells were able to reconnect the axons leading to the olfactory signalling in the brains of the mice. Scientists are still a long way from repeating the trick with human beings, but it’s a very promising start.