Cloyd Jordan M, Elliott Dawn M
McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA 19104-6081, USA.
Spine (Phila Pa 1976). 2007 Aug 1;32(17):1826-31. doi: 10.1097/BRS.0b013e3181132a9d.
Quantitative study of elastin content in nondegenerate and degenerate human intervertebral discs.
To measure the site-specific changes in elastin content that accompany disc degeneration using a quantitative, dye-binding assay to assess elastin levels.
Recently, an abundant and organized network of elastic fibers was observed in nondegenerated human disc using immunostaining histochemistry, suggesting a functional role for elastin. While degenerative changes in the disc extracellular matrix composition are well known, changes in elastin content that may accompany degeneration have not been reported.
Human discs were assigned a degenerative grade by 3 independent orthopedic surgeons based on gross morphology. Samples were taken from the outer anulus fibrosus (OAF), inner AF (IAF) and nucleus pulposus (NP). Elastin content was measured using a specific, dye-binding assay and normalized to dry weight and collagen content, which was measured via a hydroxyproline assay. Samples were divided into 2 groups: nondegenerate (Grades 1-2.5) and degenerate (Grades 2.6-4.0). A 2-way analysis of variance was used to test for statistical significance where the 2 factors were disc location and degeneration. Correlations of composition with degeneration and age were analyzed.
In nondegenerate tissue, elastin by dry weight was on average 2.0% +/- 0.3%, and there were no differences in elastin content among the locations of OAF, IAF, or NP. With degeneration, there was a significant increase in total disc elastin per dry weight at each location. The degenerate IAF had the largest amount of elastin (9.3% +/- 2.3%), significantly greater than the NP and OAF. Elastin content correlated with degenerative grade and age at each site.
Based on the location-dependent degenerative changes, with highest increases in the IAF, elastin may function to restore lamellar structure under radial loads that potentially cause delamination. Future work will focus on distinguishing the changes in elastin orientation with degeneration and understanding the mechanical functional role of elastin in the disc.
对非退变和退变的人类椎间盘弹性蛋白含量进行定量研究。
采用定量染料结合法评估弹性蛋白水平，以测量椎间盘退变过程中弹性蛋白含量的位点特异性变化。
最近，通过免疫染色组织化学在未退变的人类椎间盘中观察到丰富且有组织的弹性纤维网络，提示弹性蛋白具有功能作用。虽然椎间盘细胞外基质组成的退变变化已为人熟知，但尚未有关于退变可能伴随的弹性蛋白含量变化的报道。
3名独立的骨科医生根据大体形态为人类椎间盘评定退变等级。样本取自纤维环外层（OAF）、纤维环内层（IAF）和髓核（NP）。使用特定的染料结合法测量弹性蛋白含量，并将其归一化至干重和胶原蛋白含量，后者通过羟脯氨酸测定法测量。样本分为2组：非退变组（1 - 2.5级）和退变组（2.6 - 4.0级）。采用双向方差分析检验统计学意义，其中两个因素为椎间盘位置和退变情况。分析成分与退变及年龄的相关性。
在非退变组织中，按干重计算弹性蛋白平均为2.0%±0.3%，OAF、IAF或NP各部位的弹性蛋白含量无差异。随着退变，每个部位椎间盘每干重的总弹性蛋白显著增加。退变的IAF弹性蛋白含量最高（9.3%±2.3%），显著高于NP和OAF。各部位弹性蛋白含量与退变等级和年龄相关。
基于位置依赖性退变变化，IAF中增加最为显著，弹性蛋白可能在潜在导致分层的径向载荷下发挥恢复层状结构的作用。未来的工作将集中于区分弹性蛋白取向随退变的变化，并了解弹性蛋白在椎间盘中的机械功能作用。
