Willard Vincent P, Kalpakci Kerem N, Reimer Andrew J, Athanasiou Kyriacos A
Department of Bioengineering, Rice University, Houston, TX 77005, USA.
J Biomech Eng. 2012 Jan;134(1):011011. doi: 10.1115/1.4005763.
Understanding structure-function relationships in the temporomandibular joint (TMJ) disc is a critical first step toward creating functional tissue replacements for the large population of patients suffering from TMJ disc disorders. While many of these relationships have been identified for the collagenous fraction of the disc, this same understanding is lacking for the next most abundant extracellular matrix component, sulfated glycosaminoglycans (GAGs). Though GAGs are known to play a major role in maintaining compressive integrity in GAG-rich tissues such as articular cartilage, their role in fibrocartilaginous tissues in which GAGs are much less abundant is not clearly defined. Therefore, this study investigates the contribution of GAGs to the regional viscoelastic compressive properties of the temporomandibular joint (TMJ) disc. Chondroitinase ABC (C-ABC) was used to deplete GAGs in five different disc regions, and the time course for >95% GAG removal was defined. The compressive properties of GAG depleted regional specimens were then compared to non-treated controls using an unconfined compression stress-relaxation test. Additionally, treated and non-treated specimens were assayed biochemically and histologically to confirm GAG removal. Compared to untreated controls, the only regions affected by GAG removal in terms of biomechanical properties were in the intermediate zone, the most GAG-rich portion of the disc. Without GAGs, all intermediate zone regions showed decreased tissue viscosity, and the intermediate zone lateral region also showed a 12.5% decrease in modulus of relaxation. However, in the anterior and posterior band regions, no change in compressive properties was observed following GAG depletion, though these regions showed the highest compressive properties overall. Although GAGs are not the major extracellular matrix molecule of the TMJ disc, they are responsible for some of the viscoelastic compressive properties of the tissue. Furthermore, the mechanical role of sulfated GAGs in the disc varies regionally in the tissue, and GAG abundance does not always correlate with higher compressive properties. Overall, this study found that sulfated GAGs are important to TMJ disc mechanics in the intermediate zone, an important finding for establishing design characteristics for future tissue engineering efforts.
了解颞下颌关节（TMJ）盘的结构-功能关系是为大量患有颞下颌关节盘紊乱的患者创建功能性组织替代物的关键第一步。虽然已经确定了这些关系中的许多与盘的胶原部分有关，但对于下一个最丰富的细胞外基质成分硫酸化糖胺聚糖（GAGs），同样缺乏这种认识。尽管已知GAGs在维持富含GAGs的组织（如关节软骨）的压缩完整性方面起主要作用，但其在GAGs含量少得多的纤维软骨组织中的作用尚不清楚。因此，本研究调查了GAGs对颞下颌关节（TMJ）盘区域粘弹性压缩特性的贡献。使用软骨素酶ABC（C-ABC）去除五个不同盘区域中的GAGs，并确定>95%的GAG去除的时间进程。然后使用无侧限压缩应力松弛试验将GAG耗尽的区域标本的压缩特性与未处理的对照进行比较。此外，对处理过和未处理的标本进行生化和组织学分析，以确认GAG的去除。与未处理的对照相比，就生物力学性能而言，受GAG去除影响的唯一区域是中间区，即盘中GAG含量最高的部分。没有GAGs，所有中间区区域的组织粘度均降低，中间区外侧区域的松弛模量也降低了12.5%。然而，在前带和后带区域，GAG耗尽后未观察到压缩特性的变化，尽管这些区域总体上显示出最高的压缩特性。尽管GAGs不是颞下颌关节盘的主要细胞外基质分子，但它们负责组织的一些粘弹性压缩特性。此外，硫酸化GAGs在盘中的机械作用在组织中因区域而异，并且GAG丰度并不总是与较高的压缩特性相关。总体而言，本研究发现硫酸化GAGs对中间区的颞下颌关节盘力学很重要，这一重要发现为未来组织工程工作建立设计特征提供了依据。
