Could neural stem cells regenerate memory in the aging brain?
Researchers from the Texas A&M Health Science Center College of Medicine (TX, USA) have successfully implanted neural stem cells into the hippocampus of aged mice, which could have implications for the future treatment of neurodegenerative disorders.
Researchers from the Texas A&M Health Science Center College of Medicine (TX CoM; TX, USA) have successfully implanted neural stem cells into the hippocampus of aged mice. After observing multiple cell divisions in the grafted cells, the team suggest that the success of the transplant could have implications for the future treatment of neurodegenerative disorders.
The team, led by Ashok Shetty (TX CoM), transplanted neural stem cells into the hippocampus, a key region in memory formation that experiences particular volume loss and degeneration during aging. Shetty explained: “We’re interested in understanding aging in the brain, especially in the hippocampus, which seems particularly vulnerable to age-related changes.”
The graft was successful – co-lead author Bharathi Hattiangady (TX CoM) commented: “We’re very excited to see that the aged hippocampus can accept grafted neural stem cells as superbly as the young hippocampus does and this has implications for treating age-related neurodegenerative disorders. It’s interesting that even neural stem cell niches can be formed in the aged hippocampus.”
The older animal models were equivalent to, in human terms, approximately 70 years old. Even in the older animals, the team observed that the grafted cells divided multiple times.
“They had at least three divisions after transplantation,” Shetty added. “So the total yield of graft-derived neurons and glia (a type of brain cell that supports neurons) were much higher than the number of implanted cells, and we found that in both the young and aged hippocampus, without much difference between the two.”
Furthermore, a small percentage of grafted cells retained their stem cell nature in both young and old brains to continually produce new neurons, forming a new ‘niche’ of stem cells. Hattiangady commented: “[The niches] are still producing new neurons at least three months after implantation, and these neurons are capable of migrating to different parts of the brain.”
Unlike fetal neurons that have previously been utilized for brain regeneration investigations, the neuronal stem cells are able to tolerate hypoxia and the trauma of the grafting. “We have a new technique of preparing the donor neural stem cells,” Shetty said. “That’s why this result has never been seen before.”
In this study, the donor stem cells were taken from the subventricular zone. While only a small biopsy is required due to the capability of the cells to divide in culture, the scientists hope that cells could be obtained from the skin in the future, then reprogrammed to pluripotent stem cells.
Next, the team hope to determine whether the implanted cells have any effect on behaviour and if they have the potential to reverse age-related learning and memory deficits. Shetty concluded: “That’s an area that we’d like to study in the future. I’m always interested in ways to rejuvenate the aged brain to promote successful aging, which we see when elderly persons exhibit normal cognitive function and the ability to make memories.”
Sources: Shetty AK, Hattiangady B. Grafted subventricular zone neural stem cells display robust engraftment and similar differentiation properties and form new neurogenic niches in the young and aged hippocampus. Stem Cells Transl. Med. doi: 10.5966/sctm.2015-0270 (2016) (Epub ahead of print); www.newswise.com/articles/regenerating-memory-with-neural-stem-cells