Since the use of stem cells in medicine first entered the mainstream consciousness, there has been talk of their ability to slow down, or even eventually stop the ageing process.
The main reason for this was initially their ability to regenerate and repair failing organs and tissues. Although this has, and still is, being used as an application in various circumstances such as repairing heart tissue and restoring vision, scientists have found a greater application in modelling disease for drug discovery and in targeting treatment for personalised medicine.
But could stem cells still be used to slow down, halt or even reverse the ageing process?
Stem cells are an important part of the body’s repair system, but they too, lose regenerative ability as we age.
“The hypothesis is that stem cell function deteriorates with age, driving events we know occur with aging, like our limited ability to fully repair or regenerate healthy tissue following injury.”
Professor David Scadden, co-director of the Harvard Stem Cell Institute
It appears that particular tissues and chemical pathways send signals to others that it is time to age. Therefore if these specific tissues, such as nerve cells and insulin pathways, were targeted, could this halt ageing for the entire body?
Reducing the insulin signaling pathway, which helps the hormone insulin metabolize glucose, has been shown to greatly extend life span in flies and worms.
Stem cells within blood have been targeted as a place to look for molecules that could prompt ageing. Studies carried out on mice have shown that the blood of a young mouse rejuvenates the organs of an older mouse when the circulatory systems of two mice were joined. Improvements in brain function were also found, prompting a Californian stem cell company – Alkahast – to begin experiments giving Alzheimer’s patients plasma from young blood in hopes of improving cognition and brain function.
A Change in Understanding
Two decades in to stem cell research, and the understanding of the field has undoubtedly changed.
“Much of stem cell medicine is ultimately going to be ‘medicine,’” Scadden said. “Even here, we thought stem cells would provide mostly replacement parts. I think that’s clearly changed very dramatically. Now we think of them as contributing to our ability to make disease models for drug discovery.”
The difference in the understanding of stem cell biology has also changed. The lack of plasticity of certain stem cells within stem cell subpopulations could explain the variation in ageing.