Regional fibrocartilage variations in human anterior cruciate ligament tibial insertion: a histological three-dimensional reconstruction

Abstract

Purpose: We studied anterior cruciate ligament (ACL) tibial insertion architecture in humans and investigated regional differences that could suggest unequal force transmission from ligament to bone. Materials and methods: ACL tibial insertions were processed histologically. With Photoshop software, digital images taken from the histological slides were collaged, contour lines were drawn, and different gray values were filled based on the structure. The data were exported to Amira software for three-dimensional reconstruction. Results: The uncalcified fibrocartilage (UF) layer was divided into three regions: lateral, medial and posterior according to the architecture. The UF zone was significantly thicker laterally than medially or posteriorly (p?<?0.05). Similarly, the calcified fibrocartilage (CF) thickness was significantly greater in the lateral part of the enthesis compared to the medial and posterior parts (p?<?0.05). Conclusions: The UF quantity (more UF laterally) corresponding to the CF quantity (more CF laterally) at the ACL tibial insertion provides further evidence suggesting that the load transferred from the ACL to the tibia was greater laterally than medially and posteriorly.     

Protective effects of tumor necrosis factor-α blockade by adalimumab on articular cartilage and subchondral bone in a rat model of osteoarthritis

We aimed to investigate the effects of an anti-tumor necrosis factor-α antibody(ATNF) on cartilage and subchondral bone in a rat model of osteoarthritis.Twenty-four rats were randomly divided into three groups: sham-operated group (n=8);anterior cruciate ligament transection (ACLT)+normal saline (NS) group (n=8); andACLT+ATNF group (n=8). The rats in the ACLT+ATNF group received subcutaneousinjections of ATNF (20 μg/kg) for 12 weeks, while those in the ACLT+NS group receivedNS at the same dose for 12 weeks. All rats were euthanized at 12 weeks after surgeryand specimens from the affected knees were harvested. Hematoxylin and eosin staining,Masson''s trichrome staining, and Mankin score assessment were carried out to evaluatethe cartilage status and cartilage matrix degradation. Matrix metalloproteinase(MMP)-13 immunohistochemistry was performed to assess the cartilage molecularmetabolism. Bone histomorphometry was used to observe the subchondral trabecularmicrostructure. Compared with the rats in the ACLT+NS group, histological and Mankinscore analyses showed that ATNF treatment reduced the severity of the cartilagelesions and led to a lower Mankin score. Immunohistochemical and histomorphometricanalyses revealed that ATNF treatment reduced the ACLT-induced destruction of thesubchondral trabecular microstructure, and decreased MMP-13 expression. ATNFtreatment may delay degradation of the extracellular matrix via a decrease in MMP-13expression. ATNF treatment probably protects articular cartilage by improving thestructure of the subchondral bone and reducing the degradation of the cartilagematrix.     

Ultrastructural change of the subchondral bone increases the severity of cartilage damage in osteoporotic osteoarthritis of the knee in rabbits

Osteoporotic osteoarthritis is a phenotype of osteoarthritis (OA) manifested as fragile and osteoporotic subchondral bone. However, the ultrastructural features of subchondral bone in osteoporosis OA have not been determined. The study was aimed to investigate the ultrastructural dynamic changes of subchondral bone in osteoporotic OA model and how the ultrastructural damage in the subchondral bone caused by osteoporosis deteriorated the cartilage damage in OA. Eighteen rabbits were equally randomized to three groups, including the control, the OA and the osteoporotic OA groups. The structural changes of cartilage were evaluated by HE and safranin-O fast green staining, the Mankin’s grading system was used to assess the stage of OA progression. And microstructural or ultrastructural changes in subchondral bone were assessed by micro-computed tomography or by scanning electron microscopy. According to the changes of cartilage histopathology, the OA group was in the early pathological stage of OA while the osteoporotic OA group was in the middle stage of OA based on Mankin’s grading system. In addition, the damage of cartilage surface, reduction in the number of chondrocytes and the matrix staining were more increased in the osteoporotic OA group compared to the OA group. Compared to the OA group, the subchondral bone in the microstructure and ultrastructure in the osteoporotic OA group showed more microfracture changes in trabecular bone with more destructions of the tree-like mesh. Moreover, the collagen fibers were random rough with a fewer amount of bone lacunae in subchondral cortical plate in the osteoporotic OA group compared to the OA group. These findings indicated that the subchondral bone ultrastructure in the osteoporotic OA model was characterized by the destruction of the network structure and collagen fibers. The subchondral bone ultrastructural damage caused by osteoporosis may change mechanical properties of the upper cartilage and aggravate OA cartilage. Therefore, early diagnosis and treatment of osteoporosis is of great significance to prevent early OA from further developing osteoporotic OA.     

Development of the human Achilles tendon enthesis organ

The attachment of the Achilles tendon is part of an ‘enthesis organ’ that reduces stress concentration at the hard–soft tissue interface. The organ also includes opposing sesamoid and periosteal fibrocartilages, a bursa and Kager's fat pad. In addition, the deep crural and plantar fasciae contribute to Achilles stress dissipation and could also be regarded as components. Here we describe the sequence in which these various tissues differentiate. Serial sections of feet from spontaneously aborted foetuses (crown rump lengths 22–322 mm) were examined. All slides formed part of an existing collection of histologically sectioned embryological material, obtained under Spanish law and housed in the Universidad Complutense, Madrid. From the earliest stages, it was evident that the Achilles tendon and plantar fascia had a mutual attachment to the calcaneal perichondrium. The first components of the enthesis organ to appear (in the 45‐mm foetus) were the retrocalcaneal bursa and the crural fascia. The former developed by cavitation within the mesenchyme that later gave rise to Kager's fat pad. The tip of the putative fat pad protruded into the developing bursa in the 110‐mm foetus and fully differentiated adipocytes were apparent in the 17‐mm foetus. All three fibrocartilages were first recognisable in the 332‐mm foetus – at which time adipogenesis had commenced in the heel fat pad. The sequence in which the various elements became apparent suggests that bursal formation and the appearance of the crural fascia may be necessary to facilitate the foot movements that subsequently lead to fibrocartilage differentiation. The later commencement of adipogenesis in the heel than in Kager's pad probably reflects the non‐weight environment in utero. The direct continuity between plantar fascia and Achilles tendon that is characteristic of the adult reflects the initial attachment of both structures to the calcaneal perichondrium rather than to the skeletal anlagen itself.     

三角纤维软骨复合体的大体解剖和腕关节镜对比观察研究

目的观察腕尺侧三角纤维软骨复合体的大体结构和腕关节镜下相对应部位的结构的表现,为腕关节镜下组织结构辨认提供解剖学上的依据。方法 采用正常新鲜冷冻人尸体上肢标本5只,先在腕关节镜下,分别通过＂桡腕关节入路＂和＂远侧桡尺关节表面直接入路＂,观察三角纤维软骨复合体的远侧和近侧组成结构（三角纤维软骨,掌侧和背侧桡尺韧带）的外观、起止点和走行。然后,切开腕关节囊,肉眼大体观察以上各个组成的形态;并在开放状态下,再次用关节镜观察,对比辨认相应位置的组织结构。最后,将三角纤维软骨复合体从尺桡骨远端切下,测量、记录。结果 大体解剖测量表明,三角纤维软骨延续于桡骨远端关节面月骨窝的尺侧部分,覆盖于尺骨小头的表面,中间菲薄,呈三角形,其掌侧和背侧部分增厚,形成远侧桡尺韧带。该韧带的桡侧起点处融为一体,向尺侧走行,逐渐分开形成浅部和深部,浅部包绕止于在尺骨茎突根部,深部汇聚止于尺骨茎突基底的小凹处。通过和大体观察的对比,腕关节镜经常规的＂桡腕关节入路＂,可以清楚地观察到三角纤维软骨复合体平滑地起于桡骨远端关节面的尺侧月骨窝的尺侧缘,三角纤维软骨与月骨窝的关节软骨没有明显的界限,三角纤维软骨的掌侧和背侧部分增厚,形成掌侧和背侧桡尺韧带的浅部,与尺侧关节囊融为一体。通过＂远侧桡尺关节表面直接入路＂,可以较为＂自由＂地观察到三角纤维软骨的近侧面、远侧桡尺韧带的深部、尺骨小头和桡骨的乙状切迹,三角纤维软骨复合体呈＂穹窿状＂从桡侧走向尺侧。结论 腕关节镜是观察三角纤维软骨复合体的有效工具,＂远侧桡尺关节表面直接入路＂可以用作观察三角纤维软骨复合体的近侧组成结构。镜下结构的表现和大体相应部位的对比观察,可以提高关节镜下组织结构辨认的准确性,为进一步的病理诊疗提供帮助。     

Expression of matrix metalloproteinase-2 in osteoarthritic fibrocartilage from human mandibular condyle

Matrix metalloproteinase (MMP)-2 is expressed in osteoarthritic cartilage and synovial fluid and is thought to be involved in the degradation of cartilage extracellular matrix. However, MMP-2 expression and osteoarthritic changes in internal derangement of the temporomandibular joint are unknown. In the present study, we have examined the histological relationship between osteoarthritic changes on articular cartilage with or without articular disc perforation, and MMP-2 expression, in 85 mandibular condyles from cadavers. The expression and tissue immunolocalization of MMP-2 in fibrocartilages from these condyles was examined histochemically. The Mankin grade of histological criteria for specimens with disc perforation was significantly higher than that of specimens without perforation. MMP-2 immunostaining was positive in the cytoplasm of chondrocytes and in their surrounding matrix. There was a linear correlation between MMP-2-positive cell rates and Mankin grade. Our data suggest that MMP-2 plays an important role in fibrocartilage degradation in internal derangement of the temporomandibular joint.