Brain cells that control ageing discovered

The feeling of growing old is all in your head, is a truth that has just been proved. Scientists from Albert Einstein College of Medicine, New York, USA, have identified brain cells that control the process of ageing. A new study — published in the journal Nature — has uncovered the presence of small clusters of adult stem cells within the hypothalamus, that control the process of ageing. Hypothalamus is a small almond-shaped structure that is present in the centre of the brain and is responsible for synchronising the functions of the body’s nervous system with the endocrine system. It is also involved in carrying out many key functions related to growth, memory, reproduction, and metabolism.
The triggers
Previous studies on the hypothalamus pointed towards the role it might play in controlling ageing of the body, but the mechanism behind it remained unknown until now. In experiments conducted on laboratory mice, it was observed that as the mice grew older, the number of stem cells in their brains reduced in number and signs related to ageing began to appear. “Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal and this decline accelerates ageing,” explains Professor Dongsheng Cai, who headed this study.
Laboratory mice normally have a lifespan of two years. It was seen that the number of stem cells in the hypothalamus started to decrease around the time the mice were around 11 months old, and completely disappeared by the time they were two years old. To reaffirm this finding, scientists altered the number of stem cells in young mice and observed that removal of these cells advanced the onset of age related signs and ailments. Their lifespans also decreased by nearly 27%.
If deletion of the stem cells speeds ageing, can its addition stall the process? Hypothalamic stem cells extracted from new born mice were injected into middle-age mice. This was found to deaccelerate the signs of ageing and also extend the lifespans of the individuals by an additional four months. Inflammation and stress within the hypothalamus were the reason behind the decline of the stem cells. This in turn disrupted the functions of the hypothalamus, thereby triggering the ageing process. The new stem cells therefore had to be genetically tweaked to make them resistant to stress and inflammation, before being implanted into the hypothalamus of middle-age mice.
Gene expression
Stem cells are unspecialised cells that have the potential to develop into many different cell types. They serve as an internal repair system. The stem cells found in the hypothalamus help in the formation of new nerve cells of the brain, and secrete small molecules called microRNAs, which help control cell functions.
It is these molecules that are responsible for the anti-ageing effect of the stem cells and help in regulating gene expression. MicroRNAs are enclosed in packets called exosomes, that carry and release them into the celebro-spinal fluids found within the brain. These exosomes were extracted and directly injected into the brains of middle-age mice whose hypothalamic stem cells had diminished. The treatment not only slowed down ageing, but also brought about positive changes in terms of the mice’s muscle strength, coordination, social behaviour and learning ability. 
“By replenishing these stem cells or the molecules they produce, it is possible to slow and even reverse various aspects of ageing throughout the body,” adds Dongsheng. The process of ageing is more than just the appearance of wrinkles. It is characterised by wearing out of cells, DNA damage, decline in learning ability, degeneration of muscles, loss of memory and the onset of ailments like diabetes, arthritis and Alzheimer’s. Scientists hope that the results of this study will lead to the discovery of new treatments in the future, that would help reverse or halt the ageing process and probably extend further the lifespan of an individual.