Aging of connective tissues: experimental facts and theoretical considerations

In this chapter, we describe in detail the age-dependent modifications of connective tissues, separately for their cellular and extracellular compartments. Cell aging was studied by the in vitro method established by Hayflick as well as by ex vivo explant cultures, and results with both methods are discussed. Follows then the description of age changes of macromolecular components of extracellular matrix as well as the decline with age of receptor-mediated cell-matrix interactions. These interactions mediated by several types of receptors, as integrins, the elastin receptor and others, play a crucial role for the definition and regulation of the differentiated cell phenotype. Age-related modifications of both matrix components and receptors are discussed in order to explain the mechanisms of the age-dependent modulations of cell-matrix interactions. Finally, we discuss the relations between age changes of matrix components and the onset of age-related diseases, especially cardiovascular pathologies mostly involved in age-dependence of functions and limitation of longevity.