Collagen fibrils in bone are crosslinked with

Collagen fibrils in bone are crosslinked with?
A. Osteopontin
B. Laminin
C. Fibrillin
D. Pyridinium

Correct answer : D. Pyridinium

Molecular structure of pyridinium

Collagen fibrils in bone are cross-linked with pyridinium.
It increases bone strength.
During bone resorption by osteoclasts, these cross-links are released.
They act as biochemical markers of bone resorption.
Pyridinium cross-links can be detected in urine.

Collagen fibers – Electron microscopy

Ref: Davidson’s Principles and Practice of Medicine, 22nd Edition, p1062.

Related journal article: Urinary excretion of pyridinium crosslinks of collagen in patients with osteoporosis and the effects of bone fracture. A M McLaren, L D Hordon, H A Bird and S P Robins. Ann Rheum Dis. 1992 May; 51(5): 648–651.