Passaged Goat Costal Chondrocytes Provide a Feasible Cell Source for Temporomandibular Joint Tissue Engineering

Costal cartilage is commonly harvested for various types of facial reconstructive surgery. The ability of costal chondrocytes (CCs) to produce relevant extracellular matrix, including glycosaminoglycans (GAGs) and collagens, makes them an appealing cell source for fibrocartilage engineering. In order to obtain enough cells for tissue engineering, however, cell expansion will likely be necessary. This study examined CCs at passages 0, 1, 3, and 5, as well as temporomandibular (TMJ) disc cells, in a scaffoldless tissue engineering approach. It was hypothesized that earlier passage constructs would have more cartilaginous proteins and less fibrocartilaginous proteins. TMJ disc constructs had over twice the collagen content of any other group, as well as the largest tensile properties; however, the substantial contraction of the constructs and limited cell numbers make it a non-feasible cell source for tissue engineering. In general, statistical differences in mechanical properties or collagen content of the various CC groups were not observed; however, significantly more GAG was produced in the passaged CCs than the primary CCs. More collagen type II was also observed in some of the passaged groups. These results suggest not only feasibility but potential superiority of passaged CCs over primary CCs, which may lead to functional engineered fibrocartilage.     

Tissue engineering the mandibular condyle

Tissue engineering provides the revolutionary possibility for curing temporomandibular joint (TMJ) disorders. Although characterization of the mandibular condyle has been extensively studied, tissue engineering of the mandibular condyle is still in an inchoate stage. The purpose of this review is to provide a summary of advances relevant to tissue engineering of mandibular cartilage and bone, and to serve as a reference for future research in this field. A concise anatomical overview of the mandibular condyle is provided, and the structure and function of the mandibular condyle are reviewed, including the cell types, extracellular matrix (ECM) composition, and biomechanical properties. Collagens and proteoglycans are distributed heterogeneously (topographically and zonally). The complexity of collagen types (including types I, II, III, and X) and cell types (including fibroblast-like cells, mesenchymal cells, and differentiated chondrocytes) indicates that mandibular cartilage is an intermediate between fibrocartilage and hyaline cartilage. The fibrocartilaginous fibrous zone at the surface is separated from hyaline-like mature and hypertrophic zones below by a thin and highly cellular proliferative zone. Mechanically, the mandibular condylar cartilage is anisotropic under tension (stiffer anteroposteriorly) and heterogeneous under compression (anterior region stiffer than posterior). Tissue engineering of mandibular condylar cartilage and bone is reviewed, consisting of cell culture, growth factors, scaffolds, and bioreactors. Ideal engineered constructs for mandibular condyle regeneration must involve two distinct yet integrated stratified layers in a single osteochondral construct to meet the different demands for the regeneration of cartilage and bone tissues. We conclude this review with a brief discussion of tissue engineering strategies, along with future directions for tissue engineering the mandibular condyle.     

Toward tissue engineering of the knee meniscus

This review details current efforts to tissue engineer the knee meniscus successfully. The meniscus is a fibrocartilaginous tissue found within the knee joint that is responsible for shock absorption, load transmission, and stability within the knee joint. If this tissue is damaged, either through tears or degenerative processes, then deterioration of the articular cartilage can occur. Unfortunately, there is a dearth in the amount of work done to tissue engineer the meniscus when compared to other musculoskeletal tissues, such as bone. This review gives a brief overview of meniscal anatomy, biochemical properties, biomechanical properties, and wound repair techniques. The discussion centers primarily on the different components of attempting to tissue engineer the meniscus, such as scaffold materials, growth factors, animal models, and culturing conditions. Our approach for tissue engineering the meniscus is also discussed.     

Effects of Initial Cell Seeding Density for the Tissue Engineering of the Temporomandibular Joint Disc

Tissue engineering may provide a better treatment modality for postoperative discectomy patients. The TMJ disc is an ideal candidate for tissue engineering approaches because of its lack of an intrinsic regenerative ability. Unfortunately, basic knowledge related to TMJ disc tissue engineering is still at an infancy level and not on par to that related to articular cartilage tissue engineering. The objective of this study was to examine the effects of initial cell density of TMJ disc cells seeded in nonwoven poly-glycolic acid (PGA) scaffolds on the biochemical and biomechanical properties of constructs examined at 0, 3, and 6 weeks after seeding. Low, medium, and high seeding densities were chosen to be 15, 30, and 120 million cells per ml of scaffold, which were seeded using a spinner flask. Significant differences were found temporally and as a function of seeding density in morphology, total collagen, GAG content, and permeability of the constructs, but not in aggregate modulus. The high seeding density group outperformed the low and medium groups in collagen and GAG content at all time points measured. The high-density group produced a total of 55.37 ± 3.56 μg of collagen per construct, maintained 15.77 ± 1.86 μg of GAG per construct, and only shrunk to 50% of the original scaffold size. Permeability of the constructs at 6 weeks was decreased by 70% compared to 0 weeks.     

Novel strategies for enhancing tissue integration in cartilage repair

Introduction Articular cartilage is unable to initiate a spontaneous repair response when injured due to its avascular and aneural properties. Within adult cartilage, chondrocytes are entrapped within an extensive extracellular matrix and are unable to migrate to sights of injury to regulate tissue repair. Injury to this tissue therefore inevitably leads to degeneration of the cartilage and the development of degenerative diseases such as osteoarthritis. The surgical technique of autologous chondrocyte transplantation (ACT) was developed for the treatment of full‐thickness cartilage defects ( Brittberg et al. 1994 ). Implantation of chondrocytes into the defect site repairs the injury site with a mixture of fibrocartilaginous and hyaline‐like tissue that poorly integrates with the existing cartilage and frequently degenerates with time. In this current study, we have developed an in vitro model to investigate methods for enhancing this integration and the development of a more biomechanically stable repair tissue. Materials and methods Bovine articular cartilage explants from the metacarpalphalangeal joint were experimentally injured using a stainless steel trephine and cultured for a period of 28 days. Autologous chondrocytes in an agarose suspension were injected into the interface region at the injury site. Media was collected and analysed for proteoglycan and collagen content using the DMMB and hydroxyproline assays, respectively. Matrix metalloproteinase (MMP) expression was also analysed using zymography and an adapted collagen fibril assay. Results Morphological analyses indicate attempts at repair and integration within both control and experimental treatment groups, although the presence of autologous chondrocytes appeared to amplify this repair response. Although not statistically significant, considerable differences in proteoglycan release between injured explants and the intact control group were seen. Collagen release into the media was only seen at day 28 within experimental cultures. An up‐regulation of MMP‐2 and MMP‐9 was seen within the experimental cultures compared to the controls. Preliminary data also suggest up‐regulation of collagenases in the experimental group when compared to controls. Discussion As seen with clinical ACT treatment, the presence of autologous chondrocytes appears to enhance repair and integration attempts; however, morphologically, this repair tissue appears to be fibrocartilaginous. Further analysis will establish whether the repair tissue is true hyaline cartilage and monitor the synthesis and turnover of macromolecules within the established culture system.     

Multilayered silk scaffolds for meniscus tissue engineering

Removal of injured/damaged meniscus, a vital fibrocartilaginous load-bearing tissue, impairs normal knee function and predisposes patients to osteoarthritis. Meniscus tissue engineering solution is one option to improve outcomes and relieve pain. In an attempt to fabricate knee meniscus grafts three layered wedge shaped silk meniscal scaffold system was engineered to mimic native meniscus architecture. The scaffolds were seeded with human fibroblasts (outside) and chondrocytes (inside) in a spatial separated mode similar to native tissue, in order to generate meniscus-like tissue in vitro. In chondrogenic culture in the presence of TGF-b3, cell-seeded constructs increased in cellularity and extracellular matrix (ECM) content. Histology and Immunohistochemistry confirmed maintenance of chondrocytic phenotype with higher levels of sulfated glycosaminoglycans (sGAG) and collagen types I and II. Improved scaffold mechanical properties along with ECM alignment with time in culture suggest this multiporous silk construct as a useful micro-patterned template for directed tissue growth with respect to form and function of meniscus-like tissue.     

Engineering functional anisotropy in fibrocartilage neotissues

The knee meniscus, intervertebral disc, and temporomandibular joint (TMJ) disc all possess complex geometric shapes and anisotropic matrix organization. While these characteristics are imperative for proper tissue function, they are seldom recapitulated following injury or disease. Thus, this study's objective was to engineer fibrocartilages that capture both gross and molecular structural features of native tissues. Self-assembled TMJ discs were selected as the model system, as the disc exhibits a unique biconcave shape and functional anisotropy. To drive anisotropy, 50:50 co-cultures of meniscus cells and articular chondrocytes were grown in biconcave, TMJ-shaped molds and treated with two exogenous stimuli: biomechanical (BM) stimulation via passive axial compression and bioactive agent (BA) stimulation via chondroitinase-ABC and transforming growth factor-β1. BM + BA synergistically increased Col/WW, Young's modulus, and ultimate tensile strength 5.8-fold, 14.7-fold, and 13.8-fold that of controls, respectively; it also promoted collagen fibril alignment akin to native tissue. Finite element analysis found BM stimulation to create direction-dependent strains within the neotissue, suggesting shape plays an essential role toward driving in vitro anisotropic neotissue development. Methods used in this study offer insight on the ability to achieve physiologic anisotropy in biomaterials through the strategic application of spatial, biomechanical, and biochemical cues.     

Mechanical properties of hyaline and repair cartilage studied by nanoindentation

Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.     

A chondroitinase-ABC and TGF-β1 treatment regimen for enhancing the mechanical properties of tissue-engineered fibrocartilage

The development of functionally equivalent fibrocartilage remains elusive despite efforts to engineer tissues such as knee meniscus, intervertebral disc and temporomandibular joint disc. Attempts to engineer these structures often fail to create tissues with mechanical properties on a par with native tissue, resulting in constructs unsuitable for clinical applications. The objective of this study was to engineer a spectrum of biomimetic fibrocartilages representative of the distinct functional properties found in native tissues. Using the self-assembly process, different co-cultures of meniscus cells and articular chondrocytes were seeded into agarose wells and treated with the catabolic agent chondroitinase-ABC (C-ABC) and the anabolic agent transforming growth factor-β1 (TGF-β1) via a two-factor (cell ratio and bioactive treatment), full factorial study design. Application of both C-ABC and TGF-β1 resulted in a beneficial or positive increase in the collagen content of treated constructs compared to controls. Significant increases in both the collagen density and fiber diameter were also seen with this treatment, increasing these values by 32 and 15%, respectively, over control values. Mechanical testing found the combined bioactive treatment to synergistically increase the Young’s modulus and ultimate tensile strength of the engineered fibrocartilages compared to controls, with values reaching the lower spectrum of those found in native tissues. Together, these data demonstrate that C-ABC and TGF-β1 interact to develop a denser collagen matrix better able to withstand tensile loading. This study highlights a way to optimize the tensile properties of engineered fibrocartilage using a biochemical and a biophysical agent together to create distinct fibrocartilages with functional properties mimicking those of native tissue.     

Novel composite hyaluronan/type I collagen/fibrin scaffold enhances repair of osteochondral defect in rabbit knee

A new composite scaffold containing type I collagen, hyaluronan, and fibrin was prepared with and without autologous chondrocytes and implanted into a rabbit femoral trochlea. The biophysical properties of the composite scaffold were similar to native cartilage. The macroscopic, histological, and immunohistochemical analysis of the regenerated tissue from cell-seeded scaffolds was performed 6 weeks after the implantation and predominantly showed formation of hyaline cartilage accompanied by production of glycosaminoglycans and type II collagen with minor fibro-cartilage production. Implanted scaffolds without cells healed predominantly as fibro-cartilage, although glycosaminoglycans and type II collagen, which form hyaline cartilage, were also observed. On the other hand, fibro-cartilage or fibrous tissue or both were only formed in the defects without scaffold. The new composite scaffold containing collagen type I, hyaluronan, and fibrin, seeded with autologous chondrocytes and implanted into rabbit femoral trochlea, was found to be highly effective in cartilage repair after only 6 weeks. The new composite scaffold can therefore enhance cartilage regeneration of osteochondral defects, by the supporting of the hyaline cartilage formation.     

Use of hydrodynamic forces to engineer cartilaginous tissues resembling the non-uniform structure and function of meniscus

The aim of this study was to demonstrate that differences in the local composition of bi-zonal fibrocartilaginous tissues result in different local biomechanical properties in compression and tension. Bovine articular chondrocytes were loaded into hyaluronan-based meshes (HYAFF-11) and cultured for 4 weeks in mixed flask, a rotary Cell Culture System (RCCS), or statically. Resulting tissues were assessed histologically, immunohistochemically, by scanning electron microscopy and mechanically in different regions. Local mechanical analyses in compression and tension were performed by indentation-type scanning force microscopy and by tensile tests on punched out concentric rings, respectively. Tissues cultured in mixed flask or RCCS displayed an outer region positively stained for versican and type I collagen, and an inner region positively stained for glycosaminoglycans and types I and II collagen. The outer fibrocartilaginous capsule included bundles (up to 2 microm diameter) of collagen fibers and was stiffer in tension (up to 3.6-fold higher elastic modulus), whereas the inner region was stiffer in compression (up to 3.8-fold higher elastic modulus). Instead, molecule distribution and mechanical properties were similar in the outer and inner regions of statically grown tissues. In conclusion, exposure of articular chondrocyte-based constructs to hydrodynamic flow generated tissues with locally different composition and mechanical properties, resembling some aspects of the complex structure and function of the outer and inner zones of native meniscus.     

点种法移植软骨细胞修复关节软骨缺损

背景：生物性的重建虽能达到修复缺损,重建关节面的目的,但功能上难以与正常软骨一致。应用可降解的聚合物把移植的软骨细胞包埋起来进行移植,可能获得真正意义上的透明软骨。 目的：观察以同种异体兔软骨细胞胶原包埋后,点种法移植软骨细胞修复关节软骨缺损的效果。 方法：新西兰纯种兔制备膝关节全层软骨缺损后分为3组：分别进行胶原包埋软骨细胞点种法移植、单纯软骨细胞点种法移植和仅在大面积软骨缺损的软骨下钻孔。 结果与结论：术后2,4,12,24周观察组织学动态变化,发现胶原包埋软骨细胞点种法移植组能获得透明软骨修复,而软骨细胞点种法组和单纯软骨下骨钻孔组缺损区仅为纤维组织填充,并且胶原包埋软骨细胞点种法移植组兔各期平均组织学和组织化学得分均高于其他两组(P < 0.01)。说明胶原包埋点种法软骨细胞移植能获得透明软骨修复,尤其适用于大面积软骨缺损。     

Stem cell-based meniscus tissue engineering

Knee meniscus, a fibrocartilaginous tissue, is characterized by heterogeneity in extracellular matrix (ECM) and biomechanical properties, and critical for orthopedic stability, load transmission, shock absorption, and stress distribution within the knee joint. Most damage to the meniscus cannot be effectively healed by the body due to its partial avascular nature; thus, damage caused by injury or age impairs normal knee function, predisposing patients to osteoarthritis. Meniscus tissue engineering offers a possible solution to this problem by generating replacement tissue that may be implanted into the defect site to mimic the function of natural meniscal tissue. To address this need, a multiporous, multilamellar meniscus was formed using silk protein scaffolds and stem cells. The silk scaffolds were seeded with human bone marrow stem cells and differentiated over time in chondrogenic culture in the presence of transforming growth factor-beta 3 to generate meniscus-like tissue in vitro. High cellularity along with abundant ECM leading to enhanced biomechanics similar to native tissue was found. Higher levels of collagen type I and II, sulfated glycosaminoglycans along with enhanced collagen 1-α1, aggrecan, and SOX9 gene expression further confirmed differentiation and matured cell phenotype. The results of this study are a step forward toward biomechanically competent meniscus engineering, reconstituting both form and function of the native meniscus.     

The effect of nanofiber alignment on the maturation of engineered meniscus constructs

The fibrocartilaginous menisci are load-bearing tissues vital to the normal functioning of the knee. Removal of damaged regions of the meniscus subsequent to injury impairs knee function and predisposes patients to osteoarthritis. In this study, we employed biodegradable nanofibrous scaffolds for the tissue engineering of the meniscus. Non-aligned (NA) or fiber-aligned (AL) nanofibrous scaffolds were seeded with meniscal fibrochondrocytes (MFCs) or mesenchymal stem cells (MSCs) to test the hypothesis that fiber-alignment would augment matrix content and organization, resulting in improved mechanical properties. Additionally, we proposed that MSCs could serve as an alternative to MFCs. With time in culture, MSC- and MFC-seeded NA and AL constructs increased in cellularity and extracellular matrix (ECM) content. Counter our initial hypothesis, NA and AL constructs contained comparable amounts of ECM, although a significantly larger increase in mechanical properties was observed for AL compared to NA constructs seeded with either cell type. Cell-seeded NA constructs increased in modulus by approximately 1MPa over 10 weeks while cell-seeded AL construct increased by >7MPa. Additionally, MSC-constructs yielded greater amounts of ECM and demonstrated comparable increases in mechanical properties, thereby confirming the utility of MSCs for meniscus tissue engineering. These results demonstrate that cell-seeded fiber-aligned nanofibrous scaffolds may serve as an instructive micro-pattern for directed tissue growth, reconstituting both the form and function of the native tissue.     

Transplantation of chondrocytes seeded on collagen-based scaffold in cartilage defects in rabbits

Recent success in tissue engineering by restoring cartilage defects by transplanting autologous chondrocyte cells on a three-dimensional scaffold has prompted the improvement of this therapeutic strategy. Here we describe a new approach investigating the healing of rabbit cartilage by means of autologous chondrocytes seeded on a biomaterial made of an equine collagen type I-based scaffold. Full-thickness defects were created bilaterally in the weight-bearing surface of the medial femoral condyle of both femora of New Zealand male rabbits. The wounds were then repaired by using both chondrocytes seeded on the biomaterial and biomaterial alone. Controls were similarly treated but received either no treatment or implants of the delivery substance. Histological examination of the reconstructed tissues at 1, 3, 6, and 12 months after transplantation showed that at 1 and 3 months there was no formation of reconstructed tissue in any of the groups evaluated; after 6 months there was evidence of a newly regenerated tissue with some fibrocartilaginous features only in the group treated with biomaterial-seeded cells, and at 12 months a more organized tissue was evident in the same group. With regards to the group transplanted with biomaterial alone and the untreated control group, there was no evidence of new tissue production. These results advocate the use of this collagen-based scaffold for further in vivo studies on large size animals and, finally, in human clinical trials for the treatment of knee cartilage defects.     

The maturity of tissue-engineered cartilage in vitro affects the repairability for osteochondral defect

Cartilage tissue engineering using cells and biocompatible scaffolds has emerged as a promising approach to repair of cartilage damage. To date, however, no engineered cartilage has proven to be equivalent to native cartilage in terms of biochemical and compression properties, as well as histological features. An alternative strategy for cartilage engineering is to focus on the in vivo regeneration potential of immature engineered cartilage. Here, we used a rabbit model to evaluate the extent to which the maturity of engineered cartilage influenced the remodeling and integration of implanted extracellular matrix scaffolds containing allogenous chondrocytes. Full-thickness osteochondral defects were created in the trochlear groove of New Zealand white rabbits. Left knee defects were left untreated as a control (group 1), and right knee defects were implanted with tissue-engineered cartilage cultured in vitro for 2 days (group 2), 2 weeks (group 3), or 4 weeks (group 4). Histological, chemical, and compression assays of engineered cartilage in vitro showed that biochemical composition became more cartilagenous, and biomechanical property for compression gradually increased with culture time. In an in vivo study, gross imaging and histological observation at 1 and 3 months after implanting in vitro-cultured engineered cartilage showed that defects in groups 3 and 4 were repaired with hyaline cartilage-like tissue, whereas defects were only partially filled with fibrocartilage after 1 month in groups 1 and 2. At 3 months, group 4 showed striking features of hyaline cartilage tissue, with a mature matrix and a columnar arrangement of chondrocytes. Zonal distribution of type II collagen was most prominent, and the International Cartilage Repair Society score was also highest at this time. In addition, the subchondral bone was well ossified. In conclusion, in vivo engineered cartilage was remodeled when implanted; however, its extent to maturity varied with cultivation period. Our results showed that the more matured the engineered cartilage was, the better repaired the osteochondral defect was, highlighting the importance of the in vitro cultivation period.     

腺病毒携带骨形态发生蛋白14基因转染脂肪干细胞修复损伤关节软骨

背景：关节软骨损伤后自我修复能力较弱,主要是由于其缺乏滋养血管并且细胞代谢缓慢等组织特性,目前的治疗方法都不能恢复软骨组织的原有功能,近年来软骨组织工程已引起了越来越多的关注。 目的：观察Ⅰ型胶原海绵支架搭载骨形态发生蛋白14基因转染脂肪干细胞修复兔膝关节软骨损伤的效果。 方法：取兔皮下脂肪组织分离培养脂肪干细胞,用腺病毒真核表达载体Ad-CMV-BMP-14-IRES-hrGFP-1转染脂肪干细胞。Ⅰ型胶原海绵支架搭载转染后的脂肪干细胞,待细胞吸附后对兔膝关节全层软骨缺损进行修复。术后12周取手术关节,从大体方面、组织学方面综合评估缺损修复状况。 结果与结论：骨形态发生蛋白14转染后的脂肪干细胞骨形态发生蛋白14和Ⅱ型胶原蛋白表达及Sox-9基因表达明显高于普通脂肪干细胞。术后12周,支架搭载经骨形态发生蛋白14转染的脂肪干细胞组软骨组织修复良好,平整光滑,光洁度、质地及颜色良好,交界区整合良好。支架搭载脂肪干细胞组软骨组织部分修复,有正常软骨光泽,质地与颜色接近正常,修复组织与正常软骨组织界限明显。单纯支架组几乎崩解塌陷,未见透明样软骨结构形成。结果可见腺病毒携带骨形态发生蛋白14基因转染后脂肪干细胞修复软骨缺损的能力有大幅提升。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;组织工程全文链接：     

Evaluation of three-dimensional scaffolds prepared from poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) for growth of allogeneic chondrocytes for cartilage repair in rabbits

Articular cartilage repair using tissue engineering approach generally requires the use of an appropriate scaffold architecture that can support the formation of cartilage tissue. In this investigation, the potential of three-dimensional scaffolds made of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was evaluated in rabbit articular cartilage defect model. Engineered PHBHHx cartilage constructs inoculated in vitro with rabbit chondrocytes for 30 days were examined. Subsequently the constructs inoculated with chondrocytes for 10 days were selected for transplantation into rabbits. After 16 weeks of in vivo implantation, both the engineered cartilage constructs and the bare scaffolds were found to be filled the defects with white cartilaginous tissue, with the engineered constructs showing histologically good subchondral bone connection and better surrounding cartilage infusion. Owing to pre-seeded chondrocytes in the PHBHHx scaffolds, better surface integrality and more accumulation of extracellular matrix (ECM) including type II collagen and sGAG were achieved in the engineered cartilage constructs. The repaired tissues possessed an average compressive modulus of 1.58MPa. For comparison, the defects without repair treatments still showed defects with fibrous tissues. These results demonstrated that PHBHHx is a useful material for cartilage tissue engineering.     

Relationship between ultrastructure and biomechanical properties of the knee meniscus

The purpose of this study was to determine the biomechanical properties of the knee meniscus and to relate them to its ultrastructure. The knee joint menisci are semicircular, fibrocartilaginous structures interposed between the femoral and tibial condyles. For a long time, they were considered to be embryologic vestiges. This study describes the response of the knee joint meniscus to circumferential, radial and axial compressive forces. The results show an anisotropic response of the knee joint meniscus to unconfined compression. The Young’s modulus increased approximately twofold between vertical and circumferential or radial directions with a 10 mm/min-compression rate. This response is probably a direct consequence of the orientation of collagen fibres.