Department of Biomedical Engineering, University of California, Irvine, Irvine, California, USA.
Tissue Eng Part A. 2023 Aug;29(15-16):439-448. doi: 10.1089/ten.TEA.2023.0011. Epub 2023 May 29.
The temporomandibular joint (TMJ) disc complex (i.e., the TMJ disc and its six attachments) is crucial to everyday functions such as mastication and speaking. The TMJ can be afflicted by many conditions, including disc displacement and defects. Pathologies of the TMJ disc complex most commonly present first as anterior disc displacement, which the field hypothesizes may implicate the two posterior attachments. As a result of anterior disc displacement, defects may develop in the lateral disc complex. Tissue engineering is poised to improve treatment paradigms for these indications of the TMJ disc complex by engineering biomimetic implants, but, first, gold-standard design criteria for such implants should be established through characterization studies. This study's objective was to characterize the structural, mechanical, biochemical, and crosslinking differences among the two posterior attachments and the lateral disc in the Yucatan minipig, a well-accepted TMJ animal model. In tension, it was found that the posterior inferior attachment (PIA) was significantly stiffer and stronger by 2.13 and 2.30 times, respectively, than the posterior superior attachment (PSA). It was found that collagen in both attachments was primarily aligned mediolaterally; however, the lateral disc was much more aligned and anisotropic than either attachment. Among the three locations, the PSA exhibited the greatest degree of heterogeneity and highest proportion of fat vacuoles. The PIA and lateral disc were 1.93 and 1.91 times more collagenous, respectively, by dry weight (DW) than the PSA. The PIA also exhibited 1.78 times higher crosslinking per DW than the PSA. Glycosaminoglycan per DW was significantly higher in the lateral disc by 1.48 and 5.39 times than the PIA and PSA, respectively. Together, these results establish design criteria for tissue-engineering of the TMJ disc complex and indicate that the attachments are less fibrocartilaginous than the disc, while still significantly contributing to the mechanical stability of the TMJ disc complex during articulation. These results also support the biomechanical function of the PIA and PSA, suggesting that the stiffer PIA anchors the disc to the mandibular condyle during articulation, while the softer PSA serves to allow translation over the articular eminence. Impact Statement Characterization of the temporomandibular joint (TMJ) disc complex (i.e., the disc and its attachments) has important implications for those aiming to tissue-engineer functional replacements and can help elucidate its biomechanical function. For example, the findings shown here suggest that the stiffer posterior inferior attachment anchors the disc during articulation, while the softer posterior superior attachment allows translation over the articular eminence.
颞下颌关节（TMJ）盘复合体（即 TMJ 盘及其六个附着点）对于咀嚼和说话等日常功能至关重要。TMJ 可能会受到许多疾病的影响，包括盘移位和缺陷。TMJ 盘复合体的病理学最初最常见的表现为前盘移位，该领域假设这可能涉及两个后附着点。由于前盘移位，外侧盘复合体可能会出现缺陷。组织工程有望通过工程仿生植入物来改善 TMJ 盘复合体这些适应症的治疗模式，但首先，应该通过特征研究为这些植入物建立黄金标准设计标准。本研究的目的是表征 Yucatan 小型猪 TMJ 动物模型中两个后附着点和外侧盘的结构、力学、生化和交联差异。在拉伸时，发现后下附着点（PIA）比后上附着点（PSA）分别硬 2.13 倍和强 2.30 倍。发现两个附着点中的胶原主要呈中侧排列；然而，外侧盘比任何附着点都更规则且各向异性。在这三个位置中，PSA 表现出最大程度的异质性和最高比例的脂肪空泡。PIA 和外侧盘的胶原含量分别比 PSA 高出 1.93 倍和 1.91 倍，以干重（DW）计。PIA 的交联度也比 PSA 高 1.78 倍。以 DW 计，PIA 的糖胺聚糖分别比 PSA 和 PIA 高 1.48 倍和 5.39 倍。总的来说，这些结果为 TMJ 盘复合体的组织工程建立了设计标准，并表明附着点比盘的纤维软骨含量少，但在关节时仍对 TMJ 盘复合体的机械稳定性有显著贡献。这些结果还支持 PIA 和 PSA 的生物力学功能，表明更硬的 PIA 在关节时将盘锚定在下颌骨髁突上，而较软的 PSA 则有助于在关节隆起上进行平移。
