The collagenous nature of amianthoid degeneration of human costal cartilage.

Amianthoid (asbestoid) fibers in aging human costal cartilage are shown to be collagenous both by their electron microscopic appearance and solubilization by clostridial collagenase. The fibers differ morphologically from collagen of dermis, synovium, tendon, fibrocartilage and hyaline articular cartilage in dimension, contour and arrangement. They measure up to 1 mu in width, and their period length is 560 to 620 A. Their thickness, straightness and parallel organization suggest that amianthoid fibers are rigid. Their stability in the face of the preparative technics suggests that cohesive forces rather than spatial apposition through depletion of ground substance operate to hold the component fibrils together. These forces may or may not arise from covalent cross-links.