Department of Physics, Center for Biomedical Research, Oakland University, Rochester, MI, USA.
Cartilage. 2022 Jan-Mar;13(1):19476035221085143. doi: 10.1177/19476035221085143.
Microscopic magnetic resonance imaging (µMRI) and polarized light microscopy (PLM) are used to characterize the structural variations at different anatomical locations of femoral cartilage in young rabbits (12-14 weeks old).
Four intact knees were imaged by µMRI at 86 µm resolution. Three small cartilage-bone specimens were harvested from each of 2 femoral medial condyles and imaged by quantitative µMRI (T2 anisotropy) at 9.75 µm resolution ( = 6). These specimens, as well as the other 2 intact femoral condyles, were used for histology and imaged by quantitative PLM (retardation and angle) at 0.25 µm to 4 µm resolutions.
Quantitative MRI relaxation data and PLM fibril data revealed collaboratively distinct topographical variations in both cartilage thickness and its collagen organization in the juvenile joint. Cartilage characteristics from the central location have a 3-zone arcade-like fibril structure and a distinct magic angle effect, commonly seen in mature articular cartilage, while cartilage at the anterior location lacks these characteristics. Overall, the lowest retardation values and isotropic T2 values have been found in the distal femur (trochlear ridge), with predominant parallel fibers with respect to the articular surface. Central cartilage is the thickest (~550 µm), approximately twice as thick as the anterior and posterior locations.
Distinctly different characteristics of tissue properties were found in cartilage at different topographical locations on femoral condyle in rabbits. Knowledge of location-specific structural differences in the collagen network over the joint surface can improve the understanding of local mechanobiology and provide insights to tissue engineering and degradation repairs.
微观磁共振成像（µMRI）和偏振光显微镜（PLM）用于表征幼年兔（12-14 周龄）股骨软骨不同解剖位置的结构变化。
4 个完整的膝关节在 86 µm 分辨率下进行 µMRI 成像。从每个股骨内侧髁的 3 个小软骨-骨标本中采集 3 个，并在 9.75 µm 分辨率下进行定量 µMRI（T2 各向异性）成像（ = 6）。这些标本以及另外 2 个完整的股骨髁用于组织学，并在 0.25 µm 至 4 µm 的分辨率下进行定量 PLM（延迟和角度）成像。
定量 MRI 弛豫数据和 PLM 原纤维数据显示，在幼年关节中，软骨厚度及其胶原组织的拓扑变化具有协同性。来自中央位置的软骨特征具有 3 区弧形原纤维结构和明显的魔术角效应，这在成熟的关节软骨中很常见，而前侧位置的软骨则缺乏这些特征。总体而言，在股骨远端（滑车嵴）发现最低的延迟值和各向同性 T2 值，与关节表面平行的纤维占主导地位。中央软骨最厚（约 550 µm），约为前侧和后侧位置的两倍。
在兔股骨髁不同解剖位置的软骨中发现了明显不同的组织特性。了解关节表面胶原网络的位置特异性结构差异可以提高对局部机械生物学的理解，并为组织工程和降解修复提供深入的认识。
