Senescent (zombie) cells and aging

               Senescent cells are cells with mutations or loss of function that deem themselves unhealthy.  These cells stop reproducing and send out a signal to the immune system to be degraded.  This signal causes inflammation in nearby cells and if the immune system cannot keep up with the degradation, senescent cells build up.  This build-up has been directly related to aging.  One experiment using mice with a BubR1 knockout, a gene related to the degradation of senescent cells, found that the mice had severe hair loss, weight loss, cataracts and heart problems at just three months of age. 

               Over the past seven years, methods of killing senescent cells have been tested on mice with some having up to a 20% increase in age.  As medicine advances and diseases are cured, age related degradation of cells becomes a larger reason for death. Getting rid of senescent cells can dramatically slow the rate of aging in humans.  Large drug companies are hoping to start human trials in the very near future.

               Although getting rid of these cells is correlated with living longer, as always, it is not that easy.  The mice that lived longer in the experiments mentioned above had slower rates of injury healing.  Senescent cells might build up at sites of damage and cause inflammation to promote the healing process.  Also, in humans, each cell type has different senescent cells.  This means that a drug can only target one tissue type at a time.  More research must be done to develop medicine that can target senescent cells in all tissue types. 

               Is the possibility of slower wound healing worth slowing down aging? People who eventually receive senescent cell treatments should be aware of certain risks like these before deciding to participate to protect their autonomy.  Hopefully one day, this mechanism can be better understood so that patients can enjoy a longer life without the side effects to maximize beneficence and minimize malfeasance.  Maybe only certain tissue types should be targeted at a time, like skin for wrinkles and muscles for athletes.  This might lessen aging in certain areas but still keep a healthy healing response.  


Works Cited:

Callaway, E. (2016). Destroying worn-out cells makes mice live longer. Nature. doi:10.1038/nature.2016.19287