Comment Re:old news (Score 1) 187
I agree that the article makes it sound recent and I got misled too before reading TFA.
But can you explain why you differentiate between cell aging and human aging? Isn't human aging a consequence of cell aging?
cell aging is different than organism aging. Cells, by and large, are cheap to produce and are expendable. You produce cells via binary cell division; one cell becomes two new cells. However, most cell lineages can divide only a finite number of times. When cells from a lineage have undergone a certain number of divisions, they lose the ability to divide further. This is what is generally meant by "aged cells". Of course, each cell has a limited useful lifespan as well. Some cells (red blood cells) only last a few months, whereas others (neurons) last a lifetime. But whereas it is easy to replace a RBC (because of stem cells that do not have a limited number of cell divisions), it is somewhat harder to replace a neuron.
The number of times a cell can divide is limited by how long telomeres are. Each time a cell divides, its telomeres get shorter. The cell has mechanisms in place that measures telomere length. Once they are below a certain threshold, cell division stops. This is because (for reasons too detailed to get into here) sufficiently long telomeres are essential for replication of chromosome ends. Without such long telomeres, chromosome ends would fail to replicate. Normal cells do not express active telomerase, the enzyme needed to maintain telomere length during DNA replication. Stem cells and cancer cells have active telomerase.