Change with Age of Anisotropic Properties of Collagen Bundles

Abstract

Form birefringence curves and linear dichroic properties of aging rat tendons are different from those of adult controls. The steepness of the form birefringence curves and the increased retardations found in aging tendons are ascribed to an increase in collagen aggregation accompanied by loss of tissue water. Based on increase of retardations due to intrinsic birefringence, a rise in crystallinity levels is suggested for the collagen bundles of aging tendons. The inversion of the dichroism signs and the change in the d_∣∣ (collagen fibers oriented parallel) and d₁ (collagen fibers oriented perpendicular) spectral absorption profiles, mainly at the absorption peaks for sections stained with toluidine blue solutions at pH 4.0 and 5.0, indicate modifications at the acid glycosaminoglycan molecular orientation level with advancing age.