On the useful role of OH free radicals in differentiation of cultured human fibroblasts

The working hypothesis assuming that oxygen free radicals cannot be considered only as harmful by-products of the oxidative metabolism has been experimentally tested. Human fibroblasts were grown in culture from the following five types of tissues: (1) normal orbital fat; (2) orbital fat of patients with endocrine ophtalmopathy (EOP); (3) normal orbital muscle; (4) orbital muscle of EOP patients; (5) skin. These fibroblasts (second to 12th passages) were treated for 2×72 h with the Fenton reactants: ADP-Fe2+-complex (0.1 mM for iron) and H2O2 (0.055 mM), final concentrations. This treatment caused a slowing down of the cell proliferation, induced various morphological signs of differentiation, and significantly increased (40–150%) the total superoxide dismutase (SOD) and catalase (CAT) activities of the fibroblasts. Authors suggest that the increased expression of these enzymes may play a general role in the cell differentiation mechanisms, meaning that the generation of oxygen free radicals is an essential, useful factor even during the early phases of development, and may not be taken only as a harmful process during aging.