Identification of an Ultrathin Osteochondral Interface Tissue with Specific Nanostructure at the Human Knee Joint
Xiaozhao Wang, Junxin Lin, Zonghao Li, Yuanzhu Ma, Xianzhu Zhang, Qiulin He, Qin Wu, Yiyang Yan, Wei Wei, Xudong Yao, Chenglin Li, Wenyue Li, Shaofang Xie, Yejun Hu, Shufang Zhang, Yi Hong, Xu Li, Weiqiu Chen, Wangping Duan, Hongwei Ouyang
Abstract
Cartilage adheres to subchondral bone via a specific osteochondral interface tissue where forces are transferred from soft cartilage to hard bone without conferring fatigue damage over a lifetime of load cycles. However, the fine structure and mechanical properties of the osteochondral interface tissue remain unclear. Here, we identified an ultrathin ∼20-30 μm graded calcified region with two-layered micronano structures of osteochondral interface tissue in the human knee joint, which exhibited characteristic biomolecular compositions and complex nanocrystals assembly. Results from finite element simulations revealed that within this region, an exponential increase of modulus (3 orders of magnitude) was conducive to force transmission. Nanoscale heterogeneity in the hydroxyapatite, coupled with enrichment of elastic-responsive protein-titin, which is usually present in muscle, endowed the osteochondral tissue with excellent mechanical properties. Collectively, these results provide novel insights into the potential design for high-performance interface materials for osteochondral interface regeneration.