The human meniscus plays a crucial role for transmission and distribution of load across the knee, as well as shock absorption, joint stability, lubrication, and congruity. The aim of this study was to compare the complex geometry, and unique ultrastructure and tissue composition of the meniscus in healthy (control) and pathological conditions to provide understanding of structural changes that could be helpful in the future design of targetted therapies and improvement of treatment indications. We analyzed meniscus samples collected from 3 healthy multi-organ donors (median age, 66 years), 5 patients with traumatic meniscal tear (median age, 41 years) and 3 patients undergoing total knee replacement (TKR) for end-stage osteoarthritis (OA) (median age, 72 years). We evaluated the extracellular matrix (ECM) organization, the appearance and distribution of areas of calcification, and modifications of cellular organization and structure by electron microscopy and histology. The ECM structure was similar in specimens from traumatic meniscus tears compared to those from patients with late-stage OA, showing disorganization of collagen fibers and increased proteoglycan content. Cells of healthy menisci showed mainly diffuse chromatin and well preserved organelles. Both in traumatic and in OA menisci, we observed increased chromatin condensation, organelle degeneration, and cytoplasmic vacuolization, a portion of which contained markers of autophagic vacuoles. Areas of calcification were also observed in both traumatic and OA menisci, as well as apoptotic-like features that were particularly prominent in traumatic meniscal tear samples. We conclude that meniscal tissue from patients with traumatic meniscal injury demonstrate pathological alterations characteristic of tissue from older patients undergoing TKR, suggesting that they have high susceptibility to develop OA.

中文翻译：

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正常，受伤和骨关节炎的人类半月板的形态和​​超微结构分析。

人的半月板对于在膝盖上传递和分配负荷以及减震，关节稳定性，润滑性和合体性起着至关重要的作用。这项研究的目的是比较健康（对照）和病理情况下半月板的复杂几何形状，独特的超微结构和组织组成，以提供对结构变化的了解，这可能有助于将来靶向治疗和治疗改善的设计适应症。我们分析了从3位健康的多器官捐献者（中位年龄为66岁），5位半月板创伤性撕裂患者（中位年龄为41岁）和3位因终末期骨关节炎（OA）接受全膝关节置换术（TKR）的患者收集的半月板样品）（年龄中位数为72岁）。我们评估了细胞外基质（ECM）的组织，钙化区域的外观和分布，以及通过电子显微镜和组织学对细胞组织和结构的修改。与患有晚期OA的患者相比，创伤半月板撕裂的标本中的ECM结构相似，显示胶原纤维紊乱和蛋白聚糖含量增加。健康的半月板细胞主要表现出弥散的染色质和保存良好的细胞器。在创伤性半月板和OA半月板中，我们都观察到染色质浓缩，细胞器变性和细胞质空泡增加，其中一部分包含自噬空泡的标志物。在创伤性和半月板损伤中也观察到钙化区域，以及在创伤性半月板撕裂样品中尤为突出的类似凋亡的特征。