Seminar in Biological Mechanisms of Aging and Cancer/Cell senescence

Cellular senescence is the inability for a cell to divide. When a cell reaches this stage, in the cell cycle, it does not mean that the cell is dead. In fact, these cells can still function and perform their specific functions, they are, however, arrested in a stage in the cellular cycle in which they cannot progress into replication and division. In aging the amount of cells that have reached this senescence stage increases and with this increase comes increased issues with regards to cellular function. Since these cells cannot divide their organelles become worn out and with division and replication they cannot be replenished. Along these same lines protein synthesis, which relies upon correct reading of DNA. Therefore if the DNA is damaged and hasn't been repaired then proteins being created would also have mistakes which could lead to a repressed or a complete lack of function.

Research into the senescence of cells has been limited until recent years. With research like that of Wang, et. al. in 2009, there has been a greater exploration into how and where cellular senescence occurs. With this paper the researchers looked at the proliferation on cells that had reached senescence with a comparison between young and old mice. In their research they examined cells and the damage of DNA. With this damage they were able to tag a histone, that was used in DNA repair, with immunohistochemistry (IHC). With this method they accurately tracked DNA damage and cellular senescence within cells. They then compared the amount of histones between young and old mice and came to the conclusion that cellular senescence occurred where there were higher levels of oxidation phosphorylation. They also concluded that telomere shortening was independent of cellular senescence and thus not a main cause of aging within cells and in the organism overall.