Fishbein Kenneth W, Gluzband Yehezkiel A, Kaku Masaru, Ambia-Sobhan Hasina, Shapses Sue A, Yamauchi Mitsuo, Spencer Richard G
National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Magn Reson Med. 2007 Jun;57(6):1000-11. doi: 10.1002/mrm.21216.
Endogenous collagen cross-links influence cartilage biomechanical properties and resistance to degradation. Formalin fixation modifies collagen residues and forms new cross-links in a dose-dependent manner. We tested the hypothesis that magnetization transfer (MT) effects and T(2) depend on collagen cross-linking in cartilage. These parameters were measured in bovine nasal cartilage (BNC) prior to fixation, after 9 weeks of immersion in formalin solutions ranging in concentration from 0% to 10%, and after NaBH(3)CN reduction and washing. T(2) decreased by 59.4% +/- 1.1% upon fixation in 10% formalin, and was 32.2% +/- 5.2% shorter than initial values after washing. The apparent MT rate increased 25.9% +/- 3.7% and 52.8% +/- 7.1% over baseline under these conditions. Biochemical assays showed no significant differences in water, proteoglycan, natural cross-link, or collagen content between the 0% and 10% formalin-treated samples, while amino acid analysis demonstrated losses in (hydroxy)lysine and tyrosine, and new peaks consistent with methylene cross-links in fixed samples only. We conclude that formalin fixation of cartilage results in significant decreases in T(2) and increases in MT parameters that persist after removal of unreacted formaldehyde. The collagen cross-links thus created are associated with large changes in MT and T(2), indicating that interpretation of T(2) and MT values in terms of cartilage macromolecular content must be made with caution.
内源性胶原交联影响软骨的生物力学特性和抗降解能力。福尔马林固定会改变胶原残基，并以剂量依赖的方式形成新的交联。我们检验了磁化传递（MT）效应和T(2)取决于软骨中胶原交联的假说。在固定前、于浓度范围为0%至10%的福尔马林溶液中浸泡9周后以及在NaBH(3)CN还原和洗涤后，对牛鼻软骨（BNC）的这些参数进行了测量。在10%福尔马林中固定后，T(2)下降了59.4%±1.1%，洗涤后比初始值短32.2%±5.2%。在这些条件下，表观MT率比基线分别增加了25.9%±3.7%和52.8%±7.1%。生化分析表明，0%和10%福尔马林处理的样本在水、蛋白聚糖、天然交联或胶原含量方面没有显著差异，而氨基酸分析显示（羟）赖氨酸和酪氨酸有所损失，且仅在固定样本中出现了与亚甲基交联一致的新峰。我们得出结论，软骨的福尔马林固定会导致T(2)显著降低以及MT参数增加，在去除未反应的甲醛后这些变化仍然存在。由此产生的胶原交联与MT和T(2)的巨大变化相关，这表明在根据软骨大分子含量解释T(2)和MT值时必须谨慎。
