Leddy Holly A, Guilak Farshid
Duke University Medical Center, Department of Surgery, Orthopaedic Research Laboratories, 375 MSRB, Box 3093, Durham, NC 27710, USA.
Ann Biomed Eng. 2003 Jul-Aug;31(7):753-60. doi: 10.1114/1.1581879.
Diffusive transport of solutes is critical to the normal function of articular cartilage. The diffusion of macromolecules through cartilage may be affected by the local composition and structure, which vary with depth from the tissue surface. We hypothesized that the diffusion coefficient of uncharged molecules also varies with depth and molecular size. We used fluorescence recovery after photobleaching (FRAP) to measure site-specific diffusion coefficients of fluorescent dextran molecules (3, 40, 70, and 500 kDa) in porcine articular cartilage. The diffusion coefficients measured using FRAP exhibited an inverse size dependence and were in general agreement with those measured using other techniques. The diffusion coefficients for all molecules varied significantly with depth in a manner that depended upon the size of the diffusing molecule. The diffusion coefficients for the 3 and 500 kDa dextrans were 1.6 and 2.4 times greater, respectively, in the surface zone as compared to the middle and deep zones, whereas the diffusion coefficients of the 40 and 70 kDa dextrans were 0.3 and 0.2 times lower in the surface zone as compared to the middle and deep zones. These differences may reflect variations in the structure and composition of collagen, proteoglycans, and other macromolecules among the zones.
溶质的扩散运输对于关节软骨的正常功能至关重要。大分子在软骨中的扩散可能会受到局部组成和结构的影响，这些因素会随着距组织表面深度的不同而变化。我们推测不带电分子的扩散系数也会随深度和分子大小而变化。我们使用光漂白后荧光恢复（FRAP）技术来测量荧光葡聚糖分子（3、40、70和500 kDa）在猪关节软骨中的位点特异性扩散系数。使用FRAP测量的扩散系数呈现出与分子大小成反比的关系，并且总体上与使用其他技术测量的结果一致。所有分子的扩散系数随深度变化显著，其变化方式取决于扩散分子的大小。与中间层和深层相比，3 kDa和500 kDa葡聚糖在表层的扩散系数分别大1.6倍和2.4倍，而40 kDa和70 kDa葡聚糖在表层的扩散系数与中间层和深层相比分别低0.3倍和0.2倍。这些差异可能反映了各层中胶原蛋白、蛋白聚糖和其他大分子在结构和组成上的变化。
