Roger Guindon Hall, Rm. Cellular homeostasis in a highly differentiated tissue such as the liver is maintained by a precise balance between cell proliferation and removal of damaged or non functional cells via the process of programmed cell death or apoptosis. The balance between cell proliferation and apoptosis can be purturbed in various ways. Increased workload, which can be induced experimentally by partial hepatectomy results in rapid cell renewal by hyperplasia.
Hepatotoxic agents cause a significant proportion of hepatocytes to die by apoptosis.
Several extracellular and intracellular signals, such as growth factors and an ubiquitous family of protein kinases, known as protein kinase C participate in the coupling between proliferation and apoptosis that maintains cellular homeostasis in the liver. We have developed a model whereby one stimulus, epidermal growth factor, initially induces cell proliferation. As cells become overcrowded, they return to the normal cell number due to increased apoptosis.