Bone Abstracts

Introduction: Aging, diabetes and other disease conditions are associated with the accumulation of non-enzymatic collagen cross-links (NE-XL) in human tissues. Non-enzymatic cross-links (i.e. advanced glycation end products (AGEs)), occur at the bone collagen level, where they are associated with individuals increased fracture risk caused by bone’s reduced plasticity.

Methods: Here, non-destructive Fourier-transform infrared (FTIR) spectroscopy was used to investigate the two-dimensional spatial distribution of NE-XL in the bone matrix. A cohort of human cortical bone that had been control and ribose-treated to increase the AGE cross-link content in vitro were used to determine the correspondence between the area ratio of the 1678/1692 cm⁻¹ subbands and an increase in AGEs. The method was validated on a specific cohort of bone cores acquired before and after bisphosphonate treatment, which is associated with in vivo AGE accumulation.

Results: The peak area ratio of the amide I subbands at 1678 and 1692 cm⁻¹ shows changes with the increase in AGEs (control: 3.79±0.36, ribation: 4.31±0.45, P<0.05) and its measurement does not require demineralization of the sample. Using this new approach, significant increases in the AGE cross-link ratio were measured in iliac crest biopsies after bisphosphonate treatment (pre-treatment: 3.57±0.19, post-treatment: 3.88±0.26, P<0.05), which is known to increase in vivo AGE cross-links.

Discussion: The method provides a direct quantitative measure of collagen quality in bone. The new defined non-enzymatic cross-link ratio (NE-XLR), allowing a spatial quantitative assessment of AGE cross-links using FTIR, will be highly valuable to investigations of bone quality in cases of aging, disease and treatments.

Clearly, identified area ratio of the amide-I subbands (NE-XLR) are primed for high spatial resolution measures of collagen quality (6.25 μm), which is of crucial importance to understand the role of collagenous cross-links in bone’s mechanical competence.