The collagenous nature of amianthoid degeneration of human costal cartilage

Our plain-English summary of The collagenous nature of amianthoid degeneration of human costal cartilage, by A.J. Hough, F.C. Mottram, L. Sokoloff (The American Journal of Pathology, 1973).

The study

• Authors: A.J. Hough, F.C. Mottram, L. Sokoloff
• Journal: The American Journal of Pathology
• Published: 1973;73(1):201-16
• Cited by: 56 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

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.

In plain English

This laboratory study is not about asbestos exposure or asbestos-related disease. "Amianthoid" or "asbestoid" is the name for an age-related change in rib (costal) cartilage, where the tissue develops coarse fibers that look like asbestos. The authors examined costal cartilage taken at autopsy from 8 patients aged 19 to 50, and compared it with one sample each of other human connective tissues. They used stains, electron microscopy and enzyme digestion. Purified collagenase, an enzyme that breaks down collagen, removed the amianthoid fibers in 5 hours. The fibers resisted hyaluronidase, trypsin and guanidinium chloride. The fibers were broad, straight and lay parallel to each other. They were 6 to 10 times wider than the collagen fibrils in the comparison tissues, and their banding repeated every 560 to 620 angstroms. Nearby cartilage spaces had no cartilage cells. The authors concluded that amianthoid fibers are collagen. They wrote that the fibers' shape suggests they are rigid, and that their stability during preparation suggests cohesive forces hold their fibrils together. They noted that the exact type of collagen could not yet be identified.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (pathology) study of autopsy tissue using light microscopy stains, electron microscopy and enzyme digestion
• Who was studied: Costal (rib) cartilage obtained at autopsy from 8 patients aged 19 to 50 years. Controls were one sample each of human quadriceps tendon, dermis, synovium, articular cartilage and semilunar cartilage.
• Main results:
  • Purified clostridial collagenase removed the amianthoid fibers in 5 hours. The rest of the cartilage matrix disintegrated in 12 hours.
  • Amianthoid fibers resisted digestion by hyaluronidase and trypsin, and were not dissolved by guanidinium chloride.
  • Amianthoid fibers were 6 to 10 times wider than the collagen fibrils of the control tissues. They had straight sides and were arranged parallel to each other.
  • The banding period of amianthoid fibers varied between 560 and 620 angstroms. Normal costal cartilage collagen showed cross-striations at 640-angstrom intervals.
  • Cartilage spaces (lacunae) near amianthoid bundles contained no cartilage cells (chondrocytes).
• The authors' conclusion: The authors concluded that amianthoid fibers are collagenous, based on their electron microscopic appearance and their removal by collagenase. They said the fibers' thickness, straightness and parallel arrangement suggest the fibers are rigid. They also said the fibers' stability during preparation suggests that cohesive forces, rather than simple close packing, hold the component fibrils together. These forces may or may not arise from covalent cross-links.
• Limitations the authors state:
  • The authors noted that the clostridial collagenase used does not distinguish cartilage collagen from other collagens. The exact molecular type of amianthoid collagen could therefore not be identified, and might be if a collagenase specific for cartilage collagen became available.

Topics

Medical terms in this study, explained in our Lexicon: Collagen, Fibril.

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