Articular cartilage transplantation

This report describes the biopsy findings in four of 30 patients treated with cadaver osteochondral shell allografts for osteoarthritis in the knee. This study demonstrates that graft cartilage cells can survive in excess of 25 months, and that host bone can completely replace graft bone by creeping substitution. An inflammatory reaction in synovium and bone marrow was found in only one of four cases. Graft failure was related to prolonged down time of donor cartilage in one case and mechanical factors related to osteoarthritis in the apposing femoral surface in other cases. The clinical success of these grafts is attributed to the prolonged viability of cartilage cells, the capacity of host bone to join graft cartilage without histologic reaction, and the host's immunologic tolerance, which obviates the need for immunosuppressive therapy.     

软骨组织工程生物反应器的研究进展

体外软骨构建是软骨组织工程产业化发展及临床应用的重要手段。然而,采用现有的体外构建技术无法构建功能接近正常的软骨。生物反应器能够在一定程度上模拟体内环境,有望弥补现有体外构建技术的弊端。研究发现,流体剪切力、静态液压力和直接压缩力是体内软骨发育和成熟的重要力学因素,常用软骨生物反应器均据此设计而产生。由于不同类型生物反应器各具特点,研究和开发新型复合式生物反应器将成为未来的发展方向。对目前软骨组织工程生物反应器的研究现状做一综述。     

力学参数随深度变化的关节软骨数值模拟

目的在软骨数值模拟中,对由于设置均匀和随深度变化的力学参数而导致的结果差异进行评估。方法利用COMSOL多孔介质模块建立软骨非线性两相多孔介质模型。在静载荷下,分别用均匀和随深度变化的两种软骨力学参数对模型进行了计算,并对两者的计算结果差异进行了分析。结果对于软骨总应力,两种参数设置的结果之间差异很小。但在分析软骨的固相应力、液体压力和流动等较深入细致的问题时,两种参数设置结果之间的差异不能忽略。结论不同的软骨力学参数设置对软骨总应力的结果几乎没有影响,但对软骨内流速场则影响很大。所以均匀的力学参数设置可用来简化计算软骨总应力的问题,而其他一些更细致的分析需要立足于随深度变化的软骨力学参数。这些结论可以为今后的软骨建模和数值计算提供参考,为人工关节的设计和计算奠定基础。     

Articular cartilage defects: study of 25,124 knee arthroscopies

This retrospective study aimed to provide data on the prevalence, epidemiology and etiology of the knee articular cartilage lesions and describe and estimate, on the ground of a large database, the number of patients who might benefit from cartilage repair surgery. The analysis of 25,124 knee arthroscopies performed from 1989 to 2004 was conducted. Information concerning cartilage lesion, associated articular lesions and performed procedure were collected. Cartilage lesions were classified in accordance with the Outerbridge classification. Chondral lesions were found in 60% of the patients. Documented cartilage lesions were classified as localized focal osteochondral or chondral lesion in 67%, osteoarthritis in 29%, osteochondritis dissecans in 2% and other types in 1%. Non-isolated cartilage lesions accounted for 70% and isolated lesions accounted for 30%. The patellar articular surface (36%) and the medial femoral condyle (34%) were the most frequent localization of the cartilage lesions. Grade II according to Outerbridge classification was the most frequent grade of the cartilage lesion (42%). The most common associated articular lesions were the medial meniscus tear (37%) and the injury of the anterior crucial ligament (36%). Articular cartilage lesions are a common pathology of the knee joint. The potential candidates for cartilage repair surgery, patients with one to three localized grade III and IV cartilage lesions, under the age of 40 were found in 7% and under the age of 50 years in 9% of all analysed patients. However, because these patients are a heterogeneous group and the natural history of cartilage lesions remains so far unknown, also the total number of patients in our study, who might benefit from cartilage repair, remains unknown precisely.     

Articular cartilage glycosaminoglycans inhibit the adhesion of endothelial cells

Articular cartilage undergoes severe loss of proteoglycan and its constituent glycosaminoglycans (GAGs) in osteoarthritis. We hypothesize that the low GAG content of osteoarthritic cartilage renders the tissue susceptible to pathological vascularization. This was investigated using an in vitro angiogenesis model assessing endothelial cell adhesion to GAG-depleted cartilage explants. Bovine cartilage explants were treated with hyaluronidase to deplete GAG content and then seeded with fluorescently tagged human endothelial cells (HMEC-1). HMEC-1 adherence was assessed after 4 hr and 7 days. The effect of hyaluronidase treatment on GAG content, chondrocyte viability, and biochemical composition of the extracellular matrix was also determined. Hyaluronidase treatment reduced the GAG content of cartilage explants by 78 ± 3% compared with that of controls (p < 0.0001). GAG depletion was associated with significantly more HMEC-1 adherence on both the surface (superficial zone) and the underside (deep zone) of the explants (both p < 0.0001). The latter provided a more favorable environment for extended culture of HMEC-1 compared with the articulating surface. Hyaluronidase treatment altered the immunostaining for chondroitin sulfate epitopes, but not for lubricin. Our results support the hypothesis that articular cartilage GAGs are antiadhesive to endothelial cells and suggest that chondroitin sulfate and/or hyaluronan are responsible. The loss of these GAGs in osteoarthritis may allow osteochondral angiogenesis resulting in disease progression.     

Tissue engineering of human cartilage and osteochondral composites using recirculation bioreactors

Chondrocytes isolated from human foetal epiphyseal cartilage were seeded dynamically into polyglycolic acid (PGA) scaffolds and cultured in recirculation column bioreactors to produce tissue-engineered cartilage. Several culture techniques with the potential to provide endogenous growth factors and other conditions beneficial for de novo cartilage synthesis were investigated. Osteochondral composite constructs were generated by seeding separate PGA scaffolds with either foetal chondrocytes or foetal osteoblasts then suturing the scaffolds together before bioreactor cultivation. This type of co-culture system provided direct contact between the tissue-engineered cartilage and developing tissue-engineered bone and yielded significant improvements in cartilage quality. In the cartilage section of the composites, the concentrations of glycosaminoglycan (GAG) and total collagen were increased by 55% and 2.5-fold, respectively, compared with control cartilage cultures, while levels of collagen type II were similar to those in the controls. The osteochondral composites were harvested from the bioreactors as single units with good integration between the cartilage and bone tissues. Only the cartilage layer contained GAG while only the bone layer was mineralised. In other experiments, co-culture of tissue-engineered cartilage with pieces of ex-vivo cartilage or ex-vivo bone did not improve the quality of the cartilage relative to control cultures. Addition of 10(-6) M diacerein to the culture medium also had no effect on the properties of engineered cartilage. This work demonstrates the beneficial effects of generating cartilage tissues in contact with developing bone. It also demonstrates the feasibility of producing composite osteochondral constructs for clinical application using recirculation column bioreactors.     

Review. Articular cartilage chondrons: form, function and failure

The chondrocyte and its pericellular microenvironment together represent the chondron, historically considered the primary structural, functional and metabolic unit of articular and other hyaline cartilages. This review summarises research over the last 10 years to establish the molecular anatomy, functional properties and metabolic contribution of the chondron in articular cartilage homeostasis, and its failure during the initiation and progression of degenerative osteoarthritis.     

Articular chondrocyte culturing for cell-based cartilage repair: needs and perspectives

Articular cartilage displays a limited capacity of self-regeneration after injury. Thus, the biology of this tissue and its cellular components - the chondrocytes - has become the focus of several investigations, driven by tissue engineering and the basic and clinical research fields, aiming to ameliorate the present clinical approaches to cartilage repair. In this work, we present a brief recapitulation of the events that lead to cartilage development during the skeletal embryonal growth. The intrinsic phenotypic plasticity of the mesenchymal precursors and the adult chondrocytes is evaluated, dependent on the cell source, its physiopathological state, and as a function of the donor's age. The phenotypic changes induced by the basic culturing techniques are also taken into account, thus highlighting the phenotypic plasticity of the chondrocyte as the main property which could couple the differentiation process to the repair process. Chondrocyte proliferation and the contemporary maintenance of the chondrogenic differentiation potential are regarded as the two primary goals to be achieved in order to fulfill the quantitative needs of the clinical applications and the qualitative requirements of a properly repaired tissue. In this light, the effects of several growth factors and medium supplements are investigated. Finally, the latest improvements in culturing conditions and their possible clinical applications are presented as well.     

Articular cartilage zonal differentiation via 3D Second-Harmonic Generation imaging microscopy

Abstract

Purpose: The collagen structure throughout the patella has not been thoroughly investigated by 3D imaging, where the majority of the existing data come from histological cross sections. It is important to have a better understanding of the architecture in normal tissues, where this could then be applied to imaging of diseased states.

Methods: To address this shortcoming, we investigated the combined use of collagen-specific Second-Harmonic Generation (SHG) imaging and measurement of bulk optical properties to characterize collagen fiber orientations of the histologically defined zones of bovine articular cartilage. Forward and backward SHG intensities of sections from superficial, middle and deep zones were collected as a function of depth and analyzed by Monte Carlo simulations to extract the SHG creation direction, which is related to the fibrillar assembly.

Results: Our results revealed differences in SHG forward–backward response between the three zones, where these are consistent with a previously developed model of SHG emission. Some of the findings are consistent with that from other modalities; however, SHG analysis showed the middle zone had the most organized fibril assembly. While not distinct, we also report bulk optical property values for these different zones within the patella.

Conclusions: Collectively, these results provide quantitative measurements of structural changes at both the fiber and fibril assembly of the different cartilage zones and reveals structural information not possible by other microscope modalities. This can provide quantitative insight to the collagen fiber network in normal cartilage, which may ultimately be developed as a biomarker for osteoarthritis.     

Articular cartilage changes in experimental osteoarthritis in rabbits: MRI and morphological findings

The objective of the present study was to determine the magnetic resonance imaging (MRI) and gross pathological findings of articular cartilage in osteoarthritis experimentally induced in rabbit as an animal model. Ten adult Dutch male rabbits were randomly divided into two equal groups. In group one, in the left knee (stifle), the cranial (anterior) cruciate ligament (CCL) was sectioned [transected group (TG)], and in the second group, only arthrotomy was performed through the same approach, but the CCL was left intact [arthrotomy group (AG)]. In both groups, the right knees were considered as controls. Thirty days after operation, MRI was performed under general anesthesia, and then the animals were sacrificed for gross pathological study. MRI was performed by a 1.5-T scanner with a wrist coil to evaluate the coronal and sagittal gradient echo T2-weighted proton density and T1- and T2-weighted sequences. A magnification loupe was used to inspect the menisci, femoral and tibial cartilages, and synovium. The results revealed that the measured mean articular cartilage thickness by MRI was less in TG in comparison to AG and control groups (p < 0.05), whereas the difference between AG and control was not significant. Statistical analysis of the results revealed that the measured mean articular cartilage thickness by MRI was less in TG than those of AG and control groups, whereas the difference between AG and control was not significant. There were no significant differences in meniscal degeneration, joint effusion, and MRI overall grades between AG and the control groups. The difference was significant between TG with AG and the controls in relation to MRI findings. The gross examination revealed that there were no gross abnormalities in AG but there were also significant differences between the TG and AG, and between TG and the controls. Changes were localized primarily to the distal aspect of the medial femoral condylar cartilage. It was concluded that the MRI findings in early osteoarthritis process consisted of articular cartilage loss and meniscal degeneration. The quantitative alterations in articular cartilage thickness measured by MRI can be a noninvasive way to predict osteoarthritis. The MRI findings were also well correlated with the results of pathological study.     

间充质干细胞源性微囊泡和诱导性多潜能干细胞促进关节软骨修复的进展

背景：间充质干细胞源性微囊泡和诱导性多潜能干细胞在多个领域的组织修复作用已被证实,两者有望成为修复关节软骨损伤更有效、更安全的治疗方法。 目的：综述间充质干细胞源性微囊泡和诱导性多潜能干细胞促进软骨修复的研究进展。 方法：由第一作者应用计算机检索PubMed、中国期刊全文数据库(CNKI)2003年至2015年8月相关文献,英文检索词为“Articular cartilage injury,Bone marrow mesenchymal stem cells”,中文检索词为“软骨损伤,骨髓间充质干细胞”。选择文章内容与干细胞治疗骨关节炎有关者,同一领域文献则选择近期发表在权威杂志文章。 结果与结论：关节软骨损伤仍是骨科领域的一大难题,虽然修复方法很多,但均有局限性,而间充质干细胞源性微囊泡与诱导性多潜能干细胞的发现为软骨修复创造了可能性,同时给广大关节软骨损伤患者带来新的希望。但是,间充质干细胞源性微囊泡与诱导性多潜能干细胞大量提取及纯化方法、增殖分化潜能、在软骨修复中的作用机制等很多问题仍需要进一步解决。 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程     

Articular cartilage biomechanics: theoretical models, material properties, and biosynthetic response

Articular cartilage has unique material properties that enable the cartilage to perform its physiological functions over a lifetime and under a wide range of loading conditions. Numerous studies have investigated the relationship between cartilage properties and composition/structure. For cartilage transplantation and regeneration, it is necessary to know how cartilage maintains its functionality and how cartilage responds to the ever-changing mechanical environment. In this review, we discuss theoretical and experimental studies on the behavior of articular cartilage to load. In the first part, the composition and structure of articular cartilage is presented. In the second part, theoretical models of the mechanical behavior of cartilage, experimental methods for the determination of cartilage properties, and material properties for normal, pathologic, and repair cartilage are summarized. In the third part, the relationship between mechanical loading of the cells and their corresponding biological responses are discussed. The goal for treating joint degeneration in the future lies in cartilage regeneration rather than prosthetic replacement. In order to achieve this goal, it has to be understood how structure and function, metabolic and biochemical properties, and biomechanical performance of articular cartilage can be restored.     

Articular cartilage repair in rabbits by using suspensions of allogenic chondrocytes in alginate

The feasibility of allogenic implants of chondrocytes in alginate gels was tested for the reconstruction in vivo of artificially full-thickness-damaged articular rabbit cartilage. The suspensions of chondrocytes in alginate were gelled by the addition of calcium chloride solution directly into the defects giving in situ a construct perfectly inserted and adherent to the subchondral bone and to the walls of intact cartilage. The tissue repair was controlled at 1, 2, 4 and 6 months after the implant by NMR microscopy, synchrotron radiation induced X-ray emission to map the sulfur of glycosaminoglycans and by histochemistry. Practically a complete repair of the defect was observed 4-6 months from the implant of the chondrocytes with the recovery of a normal tissue structure. Controls in which Ca-alginate alone was implanted developed only a fibrous cartilage.     

Articular cartilage of the rabbit knee after synovectomy: a scanning electron microscopy study

We sought to study the effect of synovectomy on the surface morphology of articular cartilages of the rabbit knee using scanning electron microscopy (SEM). Fifteen rabbits were surgically synovectomised and allowed to regenerate their synovia during time intervals ranging from 3 to 44 wk. Cartilage specimens were shaved from 5 distinct articular sectors of synovectomised, contralateral and sham-operated knees and prepared for SEM using tannic acid. Applying structural reinforcement by tannic acid was found to secure the in vivo surface morphology of the cartilages and thus production of surface irregularities during preparation was excluded. The surface morphology of cartilages both from the synovectomised and contralateral joints was found to differ from that of intact healthy rabbits. A 'chaotic' nature of the altered cartilaginous morphology persisted as late as 44 wk postsynovectomy. Cartilages from sham-operated joints did not differ detectably from normal cartilages.     

Articular calcified cartilage canals in the third metacarpal bone of 2-year-old thoroughbred racehorses

We describe morphological aspects of the articular calcified cartilage mineralizing front 'tidemark' in the distal joint surface of the third metacarpal bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the 'wedges' intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at one site on the sagittal ridge in all the horses. The site is one that is relatively less loaded during joint function. These canals through calcified cartilage result from osteoclastic resorption (cutting cones) penetrating from bone through to the non-mineralized hyaline articular cartilage. Their presence may indicate a pathway for connection between bone and cartilage extracellular fluid. In one horse, repair of such canals by plugging with new calcified cartilage was demonstrated. Differences in the degree of mineralization of regions of cartilage were seen in the combined compositional-cum-topographical backscattered SEM images of the macerated 'tidemark' front. More-or-less circular patches of lower mineralization density were frequently centred on (and may possibly originate from) canals. These microanatomical features should be searched for in other joints, at other ages and in other species to discover their frequency and significance.     

Articular cartilage chondrocytes in type I and type II collagen-GAG matrices exhibit contractile behavior in vitro

Natural healing of articular cartilage defects generally does not occur, and untreated lesions may predispose the joint to osteoarthritis. To promote healing of cartilage defects, many researchers are turning toward a tissue engineering approach involving cultured cells and/or porous, resorbable matrices. This study investigated the contractile behavior of cultured canine chondrocytes seeded in a porous collagen-glycosaminoglycan (GAG) scaffold. Chondrocytes isolated from the knee joints of adult canines and expanded in monolayer culture were seeded into porous collagen-GAG scaffolds. Scaffolds were of two different compositions, with the predominant collagen being either type I or type II collagen, and of varying pore diameters. Over the 4-week culture period, the seeded cells contracted all of the type I and type II collagen-based matrices, despite a wide range of stiffness (145 +/- 23 Pa, for the type I scaffold, to 732 +/- 35 Pa, for the type II material). Pore diameter (25-85 microm, type I; and 53-257 microm, type II) did not affect cell-mediated contraction. Immunohistochemical staining revealed the presence of alpha-smooth muscle actin, an isoform responsible for contraction of smooth muscle cells and myofibroblasts, in the cytoplasm of the seeded cells and in chondrocytes in normal adult canine articular cartilage.