Question

some animals have the ability to regenerate missing organs. to do this many animals need to reinitiate a process that normally only occurs in an embryo.

come up with a couple examples of the barriers or difficulties that must be overcome to use old/differentiated cells to regenerate an organ ( such as a limb, or an eye)

Answer 1

Some animals such as amphibians are able to regenerate the lost body parts such as limbs or eye. The lizard can regenerate its tail. The regeneration is a complex process. In the case of eye regeneration, when the lens is removed from the eye, the differentiated cells from the iris are the ones responsible for the regeneration of lens. The cells in the iris lose their cellular characteristics first. The characteristics are such as the pigmentation. This process is mediated by macrophages. It is difficult to recruit macrophages to do this work. After the work, the iris cells dedifferentiate and cell cycle is initiated. Then the cells elongate and differentiate into primary lens fiber cells.It is at the inner layer and the external layer is constituted by non-dividing secondary fibers.Also, crystallins are produced. After some days, a complete lens is formed with a layer of lens epithilial cells on the outer surface and lens fiber cells on the inside.