Abnormal gene expression in skin fibroblasts from a Hutchinson-Gilford patient

We had the opportunity to investigate a new case of Hutchinson-Gilford progeria, a rare disease commonly regarded as a model in the study of aging. Two strains of fibroblasts (strains 1 and 2) were derived from two pieces of a skin biopsy. These two populations multiplied as normal cells at low population doubling level but senesced rapidly and stopped proliferating after 14 or 15 population doubling levels. Interestingly, an unusual pattern of growth in clusters was observed for strain 1. The level of collagen and noncollagen protein synthesis of both strains of affected fibroblasts was similar to that of normal fibroblasts as determined by [3H]proline incorporation measurement and was similarly affected by varying serum concentrations. The pattern of the main types of newly synthesized collagen polypeptides analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was similar in normal and progeria cells. The steady-state level of mRNAs coding for macromolecules of the extracellular matrix did not provide any differences between affected and control fibroblasts except for a strong increase of elastin and of alpha 1 and alpha 2 type IV procollagen mRNA mainly in strain 1 and less marked in strain 2. Interestingly, senescent progeria fibroblasts exhibited a reduced level of all the tested mRNAs, whereas collagen type IV and elastin mRNAs remained elevated. As suggested by immunofluorescence and immunoblotting studies, the increased amount of type IV mRNAs was paralleled by an enhanced production of type IV collagen by fibroblasts in vitro. Histologic examination of the skin revealed a superabundant network of abnormal elastic fibers in the reticular dermis and a thickening of basement membranes. The relationship between these alterations and aging in progeria is discussed.