The discussion of regeneration below applies to aseptic, experimental injury in mammals. The formation of new tissue needs the development of new cells as shown below. The extent to which cell division is taking place can be determined by radioautographic study using tritiated thymidine, or BrdU-based methods . Radioautography has shown, for example, that smooth muscle has more regenerative ability than the none credited to it previously. Tissue with cells incapable of division, e.g., neurons, is unable to restore the lost cells, although individual neurons can repair some damage to their processes.
Tissues interact inductively and trophically.
Where tissue has been damaged, phagocytosis and lysis of the necrotic tissue make room for the new cells. When the defect has been filled, the cell proliferation is reduced or stopped. This inhibition happens even when the 'wrong' tissue, e.g., fibrous CT, fills the gap. 2 Communication between the participating cells by means of cytokine and other agents. 3 Adequate hormone levels, e.g., thyroid.