Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan.
Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Science, Okazaki, Aichi, Japan.
PLoS One. 2023 Jan 19;18(1):e0280649. doi: 10.1371/journal.pone.0280649. eCollection 2023.
Both Achilles and masticatory muscle tendons are large load-bearing structures, and excessive mechanical loading leads to hypertrophic changes in these tendons. In the maxillofacial region, hyperplasia of the masticatory muscle tendons and aponeurosis affect muscle extensibility resulting in limited mouth opening. Although gene expression profiles of Achilles and patellar tendons under mechanical strain are well investigated in rodents, the gene expression profile of the masticatory muscle tendons remains unexplored. Herein, we examined the gene expression pattern of masticatory muscle tendons and compared it with that of Achilles tendons under tensile strain conditions in the Japanese macaque Macaca fuscata. Primary tenocytes isolated from the masticatory muscle tendons (temporal tendon and masseter aponeurosis) and Achilles tendons were mechanically loaded using the tensile force and gene expression was analyzed using the next-generation sequencing. In tendons exposed to tensile strain, we identified 1076 differentially expressed genes with a false discovery rate (FDR) < 10-10. To identify genes that are differentially expressed in temporal tendon and masseter aponeurosis, an FDR of < 10-10 was used, whereas the FDR for Achilles tendons was set at > 0.05. Results showed that 147 genes are differentially expressed between temporal tendons and masseter aponeurosis, out of which, 125 human orthologs were identified using the Ensemble database. Eight of these orthologs were related to tendons and among them the expression of the glycoprotein nmb and sphingosine kinase 1 was increased in temporal tendons and masseter aponeurosis following exposure to tensile strain. Moreover, the expression of tubulin beta 3 class III, which promotes cell cycle progression, and septin 9, which promotes cytoskeletal rearrangements, were decreased in stretched Achilles tendon cells and their expression was increased in stretched masseter aponeurosis and temporal tendon cells. In conclusion, cyclic strain differentially affects gene expression in Achilles tendons and tendons of the masticatory muscles.
跟腱和咀嚼肌肌腱都是大的承重结构，过度的机械负荷会导致这些肌腱发生肥大性改变。在颌面区域，咀嚼肌肌腱和腱膜的增生会影响肌肉的伸展性，导致张口受限。虽然在啮齿动物中已经很好地研究了机械应变下跟腱和髌腱的基因表达谱，但咀嚼肌肌腱的基因表达谱仍未被探索。在此，我们研究了咀嚼肌肌腱在拉伸应变下的基因表达模式，并将其与日本猕猴 Macaca fuscata 中跟腱的基因表达模式进行了比较。从咀嚼肌肌腱（颞肌腱和咬肌腱膜）和跟腱中分离出原代肌腱细胞，通过拉伸力对其进行机械加载，并使用下一代测序分析基因表达。在暴露于拉伸应变的肌腱中，我们鉴定出 1076 个具有 FDR < 10-10 的差异表达基因。为了鉴定在颞肌腱和咬肌腱膜中差异表达的基因，我们使用 FDR < 10-10，而在跟腱中使用 FDR > 0.05。结果表明，147 个基因在颞肌腱和咬肌腱膜之间差异表达，其中 125 个人类同源物使用 Ensemble 数据库进行了鉴定。这 125 个同源物中有 8 个与肌腱有关，其中糖蛋白 nmb 和鞘氨醇激酶 1 的表达在颞肌腱和咬肌腱膜暴露于拉伸应变后增加。此外，促进细胞周期进程的微管蛋白 β 3 类 III 和促进细胞骨架重排的 septin 9 的表达在拉伸的跟腱细胞中减少，而在拉伸的咬肌腱膜和颞肌腱细胞中增加。总之，循环应变对跟腱和咀嚼肌肌腱的基因表达有不同的影响。
