Cellular senescence is a response to damage or environmental factors such as toxins, wounds, and oxidative stress. It removes cells from the processes of growth and replication, and probably serves, at least initially, as a way to reduce cancer risk. In this paper, researchers remove mitochondria from senescent cells and see measures of their state improve as a result. The publicity materials head in the wrong direction, I think, by talking about aging versus cellular senescence - these are two very different things, and the aging of individual cells has no direct relationship to aging of the organism.
Growth in the number of senescent cells lingering in tissues is a contributing cause of degenerative aging due to their overall bad behavior, but so is mitochondrial damage. This research could be taken as evidence for one way which mitochondrial damage and dysfunction is important in the mechanisms of aging, but it can also be taken as a straightforward improvement in the understanding of how cells manage their transition into senescence. In either case, we already know that both of these processes are targets for near future rejuvenation therapies.
A team of scientists has for the first time shown that mitochondria, the batteries of the cells, are essential for ageing. The researchers found that when mitochondria were eliminated from ageing, senescent cells they became much more similar to younger cells. This experiment was able for the first time to conclusively prove that mitochondria are major triggers of cell ageing. This brings scientists a step closer to developing therapies to counteract cellular senescence, by targeting mitochondria.
As we grow old, cells in our bodies accumulate different types of damage and have increased inflammation, factors which are thought to contribute to the ageing process. The team carried out a series of genetic experiments involving human cells grown in the laboratory and succeeded in eliminating the majority, if not all, the mitochondria from ageing cells. Cells can normally eliminate mitochondria which are faulty by a process called mitophagy. The scientists were able to "trick" the cells into inducing this process in a grand scale, until all the mitochondria within the cells were physically removed. To their surprise, they observed that the senescent cells, after losing their mitochondria, showed characteristics similar to younger cells, that is they became rejuvenated. The levels of inflammatory molecules, oxygen free radicals and expression of genes which are among the markers of cellular ageing dropped to the level that would be expected in younger cells.
The team also deciphered a new mechanism by which mitochondria contribute to ageing. They identified that as cells grow old, mitochondrial biogenesis, the complex process by which mitochondria replicate themselves, is a major driver of cellular ageing. "This is the first time that a study demonstrates that mitochondria are necessary for cellular ageing. Now we are a step closer to devising therapies which target mitochondria to counteract the ageing of cells."