Michael Fossel Michael is President of Telocyte

November 1, 2016

Making Things Worse

Imagine a factory which is operating at capacity, with a thousand workers. Some of the workers are doing a great job, but some are ill and not working hard. In fact, they are actively interfering with those who are working hard. In this factory, you can’t hire anyone new, so you have two choices: you can fire the bad workers or you try to improve their health. If you simply fire the bad workers, you have increased the work load for those who remain. Not surprisingly, they begin to get tired and ill as well, so the factory ends up failing even faster and before you know it, everyone is out of a job. On the other hand, if you can improve the health (and the attitude) of the workers who are tired and ill, the factory can become a success.

The factory is human tissue; the workers are your cells.

Let’s look at an example, such as the cells in your knee. Over time, the chondrocytes divide, become gradually more senescent, and begin to fail. The result is osteoarthritis. If you have mild osteoarthritis, you might (naively) consider simply removing senescent cells. This reliefs some of the inflammation and removes the cells that aren’t doing a good job (the tired workers), but the result is that you’ve just asked all the remaining cells to take up the slack (increased the work load for the remaining factory workers). In order to replace the cells that you’ve removed, the remaining cells now have to divide, which accelerates their own senescent changes, and hastens the failure of the entire tissue. In the case of the knee joint, the osteoarthritis improves temporarily, but you’ve just accelerated osteoarthritic changes in the long run. Instead of a slow joint failure, you’ve ensured that it fails even faster.

Several people have, in a charming burst of innocence, recommended that we do just that. Instead of resetting senescent cells and restoring cell and tissue function, they want to remove senescent cells in older tissues. Their hope is understandable, but their understanding is simplistic. Studies show that you may see temporary improvement in inflammation and secretory profiles, but what about long term risks? The problem is that those who want to kill off senescent cells lack a full appreciation of the dynamic pathology and the cellular consequences. They offer a simplistic view, but biology is seldom simplistic.

Why you shouldn't kill senescent cells.

Why you shouldn’t kill senescent cells.


Consider the knee again. A common concern is that of chondrocyte senescence (leading to osteoarthritis) in professional basketball players. Because of repetitive high-impact trauma, they lose chondrocytes at an accelerated rate compared to people whose knees are not subject to traumatic cell loss. The remaining chondrocytes divide to replace the lost chondrocytes, accelerating telomere loss, and accelerating osteoarthritic changes. The clinical result is due to tissue failure at an early age.

Those who are trying to treat tissue senescence by selectively removing senescent cells (instead of resetting them to a normal pattern of gene expression) are causing a transient improvement in tissue function, coincident upon the removal of dysfunctional, senescent cells (temporarily decreasing inflammatory biomarkers, for example), but the longer-term result is to accelerate cell senescence in all remaining cells. The result is a transient hiatus in inflammation and other biomarkers of cell senescence, followed by a more rapid decline in cell and tissue function. In the case of OA, for example, the outcome is to relief symptoms temporarily, only to then ensure a more rapid failure of the joint.

Our analogy remains apt. If you have a group of workers in a factory, some of whom are suffering from fatigue and are no longer producing, you have two possible interventions. Intervention #1 might be to fire all the tired workers, but the long-term result is that you increase the workload and failure rate among the remaining workers. Intervention #2 would be to find a way to restore the energy and interest among those workers who are fatigued. The analogy is a loose one, but the outcomes are predictable. Removing the “tired” cells within a tissue will accelerate pathology. Resetting the “tired” cells within a tissue will resolve pathology.

If you want to cure age-related disease, the solution is not to kill senescent cells, but to reset their gene expression to that of young cells.


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