Quantitation of collagen fibril cross-section profiles in aging human veins

The cross-section profiles and the diameter distribution of collagen fibrils were examined quantitatively in normal human internal jugular veins at different ages (first, fifth, and eighth decades). All fibrils showed a regular cross-striation pattern of native-type collagen fibrils irrespective of their cross-section profiles. Irregularly outlined (“dysplastic”) fibrillar profiles were observed among the normally occurring circular crosssection profiles. The frequency of such unusual fibrils significantly increased with age. This increase was more pronounced in the tunica media as compared with the tunica adventitia. In the tunica media diameters of collagen fibrils also generally increased with age. In the tunica adventitia, on the other hand, fibrillar diameters were not significantly altered at different ages. The results of this study indicate that the frequency of both the irregularly outlined fibrillar cross-section profiles and increased fibrillar diameters depends on age in normal vascular walls. Therefore, it is concluded that the occurrence of “dysplastic” fibrils is a physiologic age-related phenomenon rather than a morphologic sign of pathologic alteration of collagen. The higher frequency of irregularly outlined collagen fibrils in the tunica media may indicate a higher and/or altered synthetic behavior of smooth muscle cells when compared with fibroblasts of the tunica adventitia.