What is the difference between cell division and cell ageing?

Cell division (also known as mitosis or cell proliferation) is the process by which a cell splits into two new cells. It is indispensable for growth, tissue repair and maintaining the correct number of cells in your body. All body cells can do this, driven by a tightly regulated programme called the cell cycle.

Cell ageing in the sense of programmed cell death is called apoptosis. This is something entirely different: a cell is not created but actively cleared away. Apoptosis removes damaged, dangerous or redundant cells in a controlled manner. It is therefore not a cell simply grinding to a halt, but a deliberate act of self-destruction.

Cell division and apoptosis are two sides of the same balance. The same molecular switches that drive cell division also regulate apoptosis. When that balance tips, problems arise. Too little apoptosis combined with too much division is a classic starting point for cancer. Certain chemical substances can disturb that balance by directly stimulating cell division, or by damaging cells so that the tissue divides excessively to compensate for the loss.

The environment of a cell also plays a role. Laboratory research with liver and skin cells shows that the surrounding scaffolding system of proteins and fibres around cells co-determines how quickly cells divide and what shape they take. Cells are therefore not autonomous: their behaviour depends strongly on the context in which they find themselves.

For completeness: 'cell ageing' in everyday language sometimes also refers to senescence, in which a cell stops dividing but does not die either. That state falls outside the studies provided and is not discussed here.