[The aging of connective tissue. Molecular and cellular aspects].

Connective tissues are made of cells and extra-cellular matrix. The predominant cells in vascular connective tissue are smooth muscle cells, fibroblasts and endothelial cells. All these cells actively synthesize the macromolecules of the extracellular matrix. This matrix comprises four types of macromolecules: collagens (11 types known), proteoglycans (8 to 10 types known); elastin and structural glycoproteins (more than a dozen known). Ageing of the connective tissue concerns therefore ageing of its cells and the extracellular matrix. For all connective tissue cells, the limit of proliferation (limit of Hayflick) was verified. The ageing of the matrix is different according to the macromolecules considered: rigidification (cross-linking) of collagen, degradation of elastin, decrease and alteration of the proteoglycans ratio. Structural glycoproteins such as fibronectin may be increased in the plasma and the tissues. Connective tissues diseases are implanted on these qualitative and quantitative modifications of the connective tissues.