Woolley William, Chin Naomi, Yu S Michael, Acevedo Claire
Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla 92093, CA, USA.
Department of Biomedical Engineering, University of Utah, Salt Lake City 84112, UT, USA.
Bone Rep. 2025 Jun 26;26:101855. doi: 10.1016/j.bonr.2025.101855. eCollection 2025 Sep.
Bone fracture risk is clinically assessed with bone mineral density (BMD); however, individuals with normal BMD also experience fractures, highlighting the need for complementary fracture risk assessment tools. While BMD remains the clinical gold standard, it fails to capture bone quality factors that contribute to fragility. Among these, collagen quality is essential for bone toughness, as it allows collagen to dissipate energy via stretching and uncoiling. When collagen is denatured, it loses its ability to deform, increasing fracture risk. This process is particularly relevant in aging, osteoporosis, and metabolic conditions such as diabetes, yet no clinical methods exist to quantify or localize denatured collagen in mineralized bone. This study introduces Collagen Hybridizing Peptide (CHP) as a tool to quantify denatured collagen in cortical bone. Here, we show that CHP fluorescence correlates strongly with collagen denaturation measured by established trypsin-hydroxyproline assay (r = 0.99) when applied to mineralized tissue subjected to heat treatment or mechanical loading. Confocal microscopy revealed a 55 % increase in collagen denaturation when tissue strain exceeded the yield point ( 0.05). Our findings demonstrate that fluorescent CHP localizes high-strain regions to collagen denaturation on bone fracture surfaces, indicating that collagen damage occurs during post-yield failure. This non-destructive technique offers a powerful tool for assessing collagen quality, with potential applications in osteoporosis, diabetic bone fragility, and aging research. By advancing our ability to evaluate bone quality in cortical bone, R-CHP provides new method to study how denatures collagen affects bone resistance to fracture.
临床上通过骨密度（BMD）评估骨折风险；然而，骨密度正常的个体也会发生骨折，这凸显了需要补充性骨折风险评估工具。虽然骨密度仍然是临床金标准，但它未能捕捉到导致骨脆性的骨质量因素。其中，胶原蛋白质量对于骨韧性至关重要，因为它能使胶原蛋白通过拉伸和展开来消散能量。当胶原蛋白变性时，它失去变形能力，增加骨折风险。这一过程在衰老、骨质疏松以及糖尿病等代谢性疾病中尤为相关，但目前尚无临床方法来量化或定位矿化骨中的变性胶原蛋白。本研究引入胶原蛋白杂交肽（CHP）作为一种量化皮质骨中变性胶原蛋白的工具。在此，我们表明，当将CHP应用于经过热处理或机械加载的矿化组织时，其荧光与通过既定的胰蛋白酶 - 羟脯氨酸测定法测得的胶原蛋白变性密切相关（r = 0.99）。共聚焦显微镜显示，当组织应变超过屈服点（ε = 0.05）时，胶原蛋白变性增加55%。我们的研究结果表明，荧光CHP可将高应变区域定位到骨折表面的胶原蛋白变性处，这表明胶原蛋白损伤发生在屈服后失效过程中。这种非破坏性技术为评估胶原蛋白质量提供了一种强大的工具，在骨质疏松症、糖尿病性骨脆性和衰老研究中具有潜在应用价值。通过提高我们评估皮质骨骨质量的能力，R-CHP为研究变性胶原蛋白如何影响骨抗骨折能力提供了新方法。
