Relevance of in vitro studies for in vivo aging

Cell cultures have allowed some fundamental mechanisms of cellular biology relevant to the aging process to be studied. The deregulation of events such as cell migration, response to growth stimuli, and inductive interactions between different cell systems have been analyzed and some of the underlying molecular mechanisms were identified. A genome reorganization taking place in the hierarchical structures of DNA during cellular aging could be ascertained. The remodeling occurring in organs, tissues, and cells during aging can be now seen as the result of the structural reorganization observed at the molecular level that progresses continuously from fertilization of the egg to the extinction of the organism. This remodeling occurs in such a way as to decrease the capacity for subsequent change, approaching a condition of equilibrium; aging can be seen as the tendency to reach this limit.