Microscale Fracture Characteristics are Influenced by Glycation Duration in a Biphasic Manner – an In Vitro Study with Human Cortical Bone

Introduction: Advanced glycation end products (AGEs) accumulate in various tissues, including bone, due to aging and other pathological states, such as diabetes mellitus, however their contribution to fracture properties of bone is yet to be verified. In vitro glycation simulates the ribose-induced formation of AGEs on tissues while avoiding confounding metabolic factors. To assess the direct effects of AGEs on bone material quality and biomechanical properties, a comprehensive controlled in vitro study was undertaken across multiple length scales

Methods: Human tibial bone from an organ donor was sectioned into 90 beams following autopsy, and randomly assigned to three mechanical test groups. Each test group included ribose (c=0.6 M) treatment at 7-, 14-, and 21-day, alongside control groups (n=5 per group). The microstructure of bone samples was determined using microCT. Fluorescent AGE (fAGE) and carboxymethyllysine (CML) levels were assessed through fluorometric analysis and mass spectrometry, while bone matrix composition was characterized using Fourier-transform infrared and Raman spectroscopy. Mechanical properties were determined through tissue level nanoindentation and three-point bending tests on non-notched and notched specimens

Results: The results showed significantly elevated fAGEs levels at 7-, 14-, and 21-day glycation compared to controls (119%, 311%, 404%; p=0.008, p<0.0001, p<0.0001; respectively), CML levels also rose substantially compared to controls (383%, 503%, 647%, p<0.0001, p<0.0001, p<0.0001; respectively). Analysis of bone matrix composition showed greater sugars/Amide I ratio at 21-day glycation compared to controls, 7-day, and 14-day (p=0.001, 0.011, 0.006; respectively); and higher carbonate-to-phosphate ratios in the ribose treatment group compared to controls (p<0.05) in the interstitial bone area. Mechanical testing of notched specimens exhibited a higher yield force, maximum force, and pre-yield toughness, at 14-day glycation compared to controls and to both 7-day and 21-day glycation (p<0.05). Nanoindentation showed that the hardness was lower at 7-day glycation compared to the controls and 21-day glycation (p<0.05)

Discussion: Our experimental study on varying glycation periods has underscored the dynamic connection between glycation duration and mechanical characteristics. Furthermore, our study suggests that the accumulation of AGEs may initially enhance the bone&apos;s ability to resist yielding. However, with an accumulation of AGEs, bone mechanical properties start to be impaired when beyond a certain threshold. Based on our findings, we postulate that exceeding this threshold could lead to adverse effects, indicating a dynamic relationship between glycation duration and mechanical characteristics. This underscores the need for ongoing research to determine this relationship and its potential implications.

Keywords: Glycaion, In vitro, Fracture Charateristic

Korrespondenzadresse: Mei-Chun Lin, University Medical Center Hamburg Eppendorf, Department of Osteology and Biomechanics, Lottestraße 55A, 22529 Hamburg, Germany, E-Mail: [e-mail]

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Artikel online veröffentlicht:
21. März 2025