Brittle Bones

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Science  13 Mar 2009:
Vol. 323, Issue 5920, pp. 1406
DOI: 10.1126/science.323.5920.1406c

Osteoarthritis occurs when the cartilage that covers the surface of bones at joints becomes degraded, resulting in pain and decreased mobility. The biomechanical properties of cartilage come from an extracellular matrix comprising proteoglycans embedded in a meshwork of collagen fibrils. Pathological changes in cartilage start at the molecular level and eventually lead to macroscopic structural and functional damage. Early detection of cartilage damage is important, both for diagnosis and to understand the mechanisms involved in disease progression with the goal of developing therapies. Indentation-type atomic force microscopy (IT-AFM) can measure the compressive stiffness of porcine articular cartilage at the micrometer and nanometer scales. Now Stolz et al. have used IT-AFM to monitor the development of an osteoarthritis-like condition in collagen-IX knockout mice. At the micrometer scale, no morphological changes were observed in articular cartilage of mutant as compared to control mice until 6 months of age. However, nanometer-scale IT-AFM showed disease-associated changes in fibril thickness and nanostiffness in mice as young as 1 month old. The biomechanical changes that occur during normal aging are distinct from pathological changes associated with disease progression. The success of IT-AFM in detecting these early changes suggests that it could serve as a useful diagnostic nanotool; the next step will be to develop such a minimally invasive surgical tool. — VV

Nat. Nanotechnol. 10.1038/nnano.2008.410 (2009).

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