Tang Tengteng, Zhong Jingxiao, Hu Jingrui, Schemenz Victoria, Davydok Anton, Brunner Roland, Zhou Jun, Wagermaier Wolfgang, Pitsillides Andrew A, Landis William J, Fratzl Peter, Chen Junning
Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany; Department of Mechanical and Aerospace Engineering, Center for Applied Biomechanics, University of Virginia, Charlottesville, USA.
Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany; Department of Engineering, Faculty of Environment, Science and Economy, University of Exeter, Exeter, UK.
Acta Biomater. 2025 Jul 1;201:385-399. doi: 10.1016/j.actbio.2025.06.002. Epub 2025 Jun 3.
Mouse femurs are widely used to study bone development and disorders. The mammalian femoral head epiphysis, located between articular cartilage and a growth plate, critically maintains joint integrity during weight-bearing and supports femoral growth. Murine femoral head epiphyses are unusual in having no secondary ossification center (SOC). In this regard, a key question arises: How is the extracellular matrix (ECM) of the mouse femoral head epiphysis structured to balance the competing demands of mechanical stability and nutrient transport in the absence of a SOC? This study investigates the microstructure and ECM organization of normal young mouse femoral head epiphyses across multiple length scales and identifies distinct gradients in lacunar size, shape, mineral content, and collagen and mineral organization. Chondrocyte lacunae in deep epiphyseal zones are significantly larger, more spherical and interconnected, compared to the lacunae near the tidemark and growth plate. Enlarged lacunae and increased tissue porosity in the deep zones are associated with higher ECM mineralization, compensating for reduced stiffness from the porosity while maintaining compliance that may facilitate fluid flow and nutrient diffusion to enlarged cells. This study highlights an optimization strategy of murine proximal femoral epiphyses driven by mechanical and biological demands and it offers insights for designing engineered constructs. STATEMENT OF SIGNIFICANCE: The mouse femoral head epiphysis lacks a secondary ossification center (SOC) and is instead entirely comprised of calcified cartilage at a young age. Given that the SOC is thought to be essential for joint function in mammals, a key question arises: How does the young mouse femoral head epiphysis sustain chondrocyte viability while supporting mechanical function? Using multiscale 3D structural characterization, we identify unique gradients in chondrocyte lacunar morphology and extracellular matrix (ECM) organization. Our findings reveal a finely tuned balance between porosity-driven nutrient transport and mineralization-enhanced mechanical stability, offering novel insights into cartilage biology and functionality. These structural principles provide a foundation for biomimetic scaffold design in regenerative medicine, making this work highly relevant to the field of biomaterials and orthopedic tissue engineering.
小鼠股骨被广泛用于研究骨骼发育和疾病。哺乳动物的股骨头骨骺位于关节软骨和生长板之间,在负重过程中对维持关节完整性至关重要,并支持股骨生长。鼠类股骨头骨骺的不同寻常之处在于没有次级骨化中心(SOC)。在这方面,出现了一个关键问题:在没有次级骨化中心的情况下,小鼠股骨头骨骺的细胞外基质(ECM)是如何构建的,以平衡机械稳定性和营养物质运输这两种相互竞争的需求?本研究在多个长度尺度上研究了正常幼年小鼠股骨头骨骺的微观结构和细胞外基质组织,并确定了腔隙大小、形状、矿物质含量以及胶原蛋白和矿物质组织中的明显梯度。与潮线和生长板附近的腔隙相比,骨骺深部区域的软骨细胞腔隙明显更大、更呈球形且相互连接。深部区域扩大的腔隙和增加的组织孔隙率与更高的细胞外基质矿化有关,在保持顺应性以促进流体流动和营养物质向扩大的细胞扩散的同时,弥补了孔隙率导致的硬度降低。本研究强调了由机械和生物学需求驱动的鼠类近端股骨骨骺的优化策略,并为设计工程构建体提供了见解。重要性声明:小鼠股骨头骨骺缺乏次级骨化中心,在幼年时完全由钙化软骨组成。鉴于次级骨化中心被认为对哺乳动物的关节功能至关重要,一个关键问题出现了:幼年小鼠股骨头骨骺如何在支持机械功能的同时维持软骨细胞的活力?通过多尺度三维结构表征,我们确定了软骨细胞腔隙形态和细胞外基质(ECM)组织中的独特梯度。我们的研究结果揭示了孔隙率驱动的营养物质运输与矿化增强的机械稳定性之间的精细平衡,为软骨生物学和功能提供了新的见解。这些结构原理为再生医学中的仿生支架设计奠定了基础,使这项工作与生物材料和骨科组织工程领域高度相关。
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