Design and characterization of a tissue‐engineered bilayer scaffold for osteochondral tissue repair

Treatment of full‐thickness cartilage defects relies on osteochondral bilayer grafts, which mimic the microenvironment and structure of the two affected tissues: articular cartilage and subchondral bone. However, the integrity and stability of the grafts are hampered by the presence of a weak interphase, generated by the layering processes of scaffold manufacturing. We describe here the design and development of a bilayer monolithic osteochondral graft, avoiding delamination of the two distinct layers but preserving the cues for selective generation of cartilage and bone. A highly porous polycaprolactone‐based graft was obtained by combining solvent casting/particulate leaching techniques. Pore structure and interconnections were designed to favour in vivo vascularization only at the bony layer. Hydroxyapatite granules were added as bioactive signals at the site of bone regeneration. Unconfined compressive tests displayed optimal elastic properties and low residual deformation of the graft after unloading (< 3%). The structural integrity of the graft was successfully validated by tension fracture tests, revealing high resistance to delamination, since fractures were never displayed at the interface of the layers (n = 8). Ectopic implantation of grafts in nude mice, after seeding with bovine trabecular bone‐derived mesenchymal stem cells and bovine articular chondrocytes, resulted in thick areas of mature bone surrounding ceramic granules within the bony layer, and a cartilaginous alcianophilic matrix in the chondral layer. Vascularization was mostly observed in the bony layer, with a statistically significant higher blood vessel density and mean area. Thus, the easily generated osteochondral scaffolds, since they are mechanically and biologically functional, are suitable for tissue‐engineering applications for cartilage repair. Copyright © 2012 John Wiley & Sons, Ltd.     

Tissue‐engineered trachea from a 3D‐printed scaffold enhances whole‐segment tracheal repair in a goat model

Traditional treatment therapies for tracheal stenosis often cause severe post‐operative complications. To solve the current difficulties, novel and more suitable long‐term treatments are needed. A whole‐segment tissue‐engineered trachea (TET) representing the native goat trachea was 3D printed using a poly(caprolactone) (PCL) scaffold engineered with autologous auricular cartilage cells. The TET underwent mechanical analysis followed by in vivo implantations in order to evaluate the clinical feasibility and potential. The 3D‐printed scaffolds were successfully cellularized, as observed by scanning electron microscopy. Mechanical force compression studies revealed that both PCL scaffolds and TETs have a more robust compressive strength than does the native trachea. In vivo implantation of TETs in the experimental group resulted in significantly higher mean post‐operative survival times, 65.00 ± 24.01 days (n = 5), when compared with the control group, which received autologous trachea grafts, 17.60 ± 3.51 days (n = 5). Although tracheal narrowing was confirmed by bronchoscopy and computed tomography examination in the experimental group, tissue necrosis was only observed in the control group. Furthermore, an encouraging epithelial‐like tissue formation was observed in the TETs after transplantation. This large animal study provides potential preclinical evidence around the employment of an orthotopic transplantation of a whole 3D‐printed TET.     

Tissue‐engineered constructs based on SPCL scaffolds cultured with goat marrow cells: functionality in femoral defects

This study aims to assess the in vivo performance of cell–scaffold constructs composed of goat marrow stromal cells (GBMCs) and SPCL (a blend of starch with polycaprolactone) fibre mesh scaffolds at different stages of development, using an autologous model. GBMCs from iliac crests were seeded onto SPCL scaffolds and in vitro cultured for 1 and 7 days in osteogenic medium. After 1 and 7 days, the constructs were characterized for proliferation and initial osteoblastic expression by alkaline phosphatase (ALP) activity. Scanning electron microscopy analysis was performed to investigate cellular morphology and adhesion to SPCL scaffolds. Non‐critical defects (diameter 6 mm, depth 3 mm) were drilled in the posterior femurs of four adult goats from which bone marrow and serum had been collected previously. Drill defects alone and defects filled with scaffolds without cells were used as controls. After implantation, intravital fluorescence markers, xylenol orange, calcein green and tetracycline, were injected subcutaneously after 2, 4 and 6 weeks, respectively, for bone formation and mineralization monitoring. Subsequently, samples were stained with Lévai–Laczkó for bone formation and histomorphometric analysis. GBMCs adhered and proliferated on SPCL scaffolds and an initial differentiation into pre‐osteoblasts was detected by an increasing level of ALP activity with the culture time. In vivo experiments indicated that bone neoformation occurred in all femoral defects. The results obtained provided important information about the performance of SPCL–GBMC constructs in an orthotopic goat model that enabled future studies to be designed to investigate in vivo the functionality of SPCL–GBMC constructs in more complex models, viz. critical sized defects, and to evaluate the influence of in vitro cultured autologous cells in the healing and bone regenerative process. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel nanostructured scaffold for osteochondral regeneration: pilot study in horses

The present in vivo preliminary experiment is aimed at testing mechanical and biological behaviour of a new nano‐structured composite multilayer biomimetic scaffold for the treatment of chondral and osteochondral defects. The three‐dimensional biomimetic scaffold (Fin‐Ceramica Faenza S.p.A., Faenza—Italy) was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles, in two configurations, bi‐ and tri‐layered, to reproduce, respectively, chondral and osteochondral anatomy. Chondral defects (lateral condyle) and deep osteochondral defects (medial condyle) were made in the distal epiphysis of the third metacarpal bone of both forelimbs of two adult horses and treated respectively with the chondral and osteochondral grafts. Both animals were euthanised six months follow up. The images obtained at the second look arthroscopy evaluation, performed two months after surgery, demonstrated good filling of the chondral and osteo‐chondral defects without any inflammatory reaction around and inside the lesions. At the histological analysis the growth of trabecular bone in the osteochondral lesion was evident. Only in one case, the whole thickness of the osteochondral lesion was filled by fibrocartilaginous tissue. The formation of a tidemark line was evident at the interface with the newly formed bone. Newly formed fibrocartilaginous tissue was present in the area of the chondral defect. Initial alignment of the collagen fibres was recognisable with polarised light in both groups. The results of the present pilot study showed that this novel osteochondral and chondral scaffold may act as a suitable matrix to facilitate orderly regeneration of bone and hyaline‐like cartilage. Copyright © 2010 John Wiley & Sons, Ltd.     

Cultivation of agarose‐based microfluidic hydrogel promotes the development of large,full‐thickness,tissue‐engineered articular cartilage constructs

The fabrication of tissue‐engineered constructs of clinically relevant sizes continues to be plagued by poor nutrient transport to the interior of the construct. Consequences of poor mass transfer to the construct core include large gradients in cell viability and matrix deposition, as well as inadequate mechanical functionality. Prior literature has shown that embedded microfluidic channels offer the potential to control the spatial and temporal presentation of hydrodynamic and chemical cues within the developing tissue construct toward improved mass transfer. The current state of the art in microfluidic constructs, however, has fallen short of achieving sufficient thickness and robustness of constructs for further development towards translation. Towards this goal, we designed a microfluidic tissue construct and established bioprocessing conditions to meet nutrient transport requirements of a large, full‐thickness, articular cartilage construct over a 2 week culture period. Our microfluidic constructs of 2.5 and 5 mm thicknesses showed enhanced cell proliferation relative to statically cultured constructs. These constructs, which are both thick and robust to culture periods of sufficient length to support extracellular matrix development, represent an important improvement over previously reported constructs which were thinner and lacking in extracellular matrix (most likely attributable to too‐short culture periods). Copyright © 2014 John Wiley & Sons, Ltd.     

Construction of tissue‐engineered osteochondral composites and repair of large joint defects in rabbit

In this study, a novel three‐dimensional (3D) heterogeneous/bilayered scaffold was constructed to repair large defects in rabbit joints. The scaffold includes two distinct but integrated layers corresponding to the cartilage and bone components. The upper layer consists of gelatin, chondroitin sulphate and sodium hyaluronate (GCH), and the lower layer consists of gelatin and ceramic bovine bone (GCBB). The two form a 3D bilayered scaffold (GCH–GCBB), which mimics the natural osteochondral matrix for use as a scaffold for osteochondral tissue engineering. The purpose of this study was to evaluate the efficacy of this novel scaffold, combined with chondrocytes and bone marrow stem cells (BMSCs) to repair large defects in rabbit joints. Thirty‐six large defects in rabbit femoral condyles were created; 12 defects were treated with the same scaffold combined with cells (group A); another 12 defects were treated with cell‐free scaffolds (group B); the others were untreated (group C). At 6 and 12 weeks, in group A hyaline‐like cartilage formation could be observed by histological examination; the newly formed cartilage, which stained for type II collagen, was detected by RT–PCR at high‐level expression. Most of the GCBB was replaced by bone, while little remained in the underlying cartilage. At 36 weeks, GCBB was completely resorbed and a tidemark was observed in some areas. In contrast, groups B and C showed no cartilage formation but a great amount of fibrous tissue, with only a little bone formation. In summary, this study demonstrated that a novel scaffold, comprising a top layer of GCH, having mechanical properties comparable to native cartilage, and a bottom layer composed of GCBB, could be used to repair large osteochondral defects in joints. Copyright © 2012 John Wiley & Sons, Ltd.     

Utilizing tissue‐engineered cartilage or BMNC‐PLGA composites to fill empty spaces during autologous osteochondral mosaicplasty in porcine knees

The potential empty spaces between cylindrical plugs remaining after autologous osteochondral mosaicplasty rely on fibrous repair, which may constrain the quality and integrity of the repair. Thus, the empty spaces should be repaired, and how to fill the empty spaces is still a problem. In the present study, a standardized full‐thickness defect (diameter, 6 mm) was created in the weight‐bearing area of each medial femoral condyle in both knees of 18 miniature pigs. The 36 knees were randomly assigned to four groups with nine in each group. The defects were initially repaired by autologous osteochondral mosaicplasty. Simultaneously, any empty spaces between the multiple plugs were filled with cell‐free poly(lactide‐co‐glycolide) (PLGA) scaffolds (the scaffold group), tissue‐engineered cartilage (the TE group) or bone marrow mononuclear cell (BMNC)–PLGA composites (the composite group). The empty spaces were left untreated as control (the control group). Six months after surgery, the repair results were assessed via macroscopic observation, histological evaluation, magnetic resonance imaging, biomechanical assessment and glycosaminoglycan content. The results demonstrated that mosaicplasty combined with the treatment of the empty spaces could improve cartilage regeneration. The filling of empty spaces by tissue‐engineered cartilage produced the best result in all the four groups. Meanwhile, utilizing BMNC–PLGA composites achieved a similar repair result. Considering the cost‐effective, time‐saving and convenient performance, the BMNC‐PLGA composite could be an alternative option to fill the empty spaces combined with mosaicplasty. Copyright © 2014 John Wiley & Sons, Ltd.     

Three‐dimensional assembly of tissue‐engineered cartilage constructs results in cartilaginous tissue formation without retainment of zonal characteristics

Articular cartilage has limited regenerative capabilities. Chondrocytes from different layers of cartilage have specific properties, and regenerative approaches using zonal chondrocytes may yield better replication of the architecture of native cartilage than when using a single cell population. To obtain high seeding efficiency while still mimicking zonal architecture, cell pellets of expanded deep zone and superficial zone equine chondrocytes were seeded and cultured in two layers on poly(ethylene glycol)‐terephthalate–poly(butylene terephthalate) (PEGT–PBT) scaffolds. Scaffolds seeded with cell pellets consisting of a 1:1 mixture of both cell sources served as controls. Parallel to this, pellets of superficial or deep zone chondrocytes, and combinations of the two cell populations, were cultured without the scaffold. Pellet cultures of zonal chondrocytes in scaffolds resulted in a high seeding efficiency and abundant cartilaginous tissue formation, containing collagen type II and glycosaminoglycans (GAGs) in all groups, irrespective of the donor (n = 3), zonal population or stratified scaffold‐seeding approach used. However, whereas total GAG production was similar, the constructs retained significantly more GAG compared to pellet cultures, in which a high percentage of the produced GAGs were secreted into the culture medium. Immunohistochemistry for zonal markers did not show any differences between the conditions. We conclude that spatially defined pellet culture in 3D scaffolds is associated with high seeding efficiency and supports cartilaginous tissue formation, but did not result in the maintenance or restoration of the original zonal phenotype. The use of pellet‐assembled constructs leads to a better retainment of newly produced GAGs than the use of pellet cultures alone. Copyright © 2013 John Wiley & Sons, Ltd.     

组织工程化软骨修复界面整合的体外模型

背景：随着组织工程学的发展,自体软骨细胞移植技术经常被用来修复软骨缺损,整合不良是导致修复失败的原因之一。许多体外模型被用来进行这方面的研究。 目的：建立一种组织工程化软骨修复界面整合的体外实验模型并评价其效果。 方法：制备猪体外软骨整合模型,获得21个软骨环,18只琼脂糖凝胶覆盖的软骨环设为琼脂糖凝胶组,剩余3个做无琼脂糖对照组,分别植入分离的软骨细胞,观察近期软骨环边界细胞漏出情况,分别在1,2,4周做切片、染色并行组织学观察,测量新生软骨平均面积并进行比较。 结果与结论：无琼脂糖对照组由于软骨细胞早期从软骨环底部漏出,未能在软骨环中形成软骨细胞聚集,所以未做后期处理,而琼脂糖凝胶组则未发生。琼脂糖凝胶组1,2,4周做切片并行固定后组织切片分别用苏木精-伊红染色、阿利新蓝、番红O、Ⅱ型胶原免疫组化染色,移植的软骨细胞在软骨环内不断增殖,并且产生细胞外基质。在第1,2周的孵育中,新生软骨的面积明显增大,到第4周时,面积也有进一步增加,但是第2-4周的面积增加,差异无显著性意义（P〉0.05）。模型成功模拟了自体软骨细胞移植修复关节软骨缺损的体外整合过程,未来可应用于软骨整合及软骨组织工程的机制研究。     

Biomimetic scaffolds and dynamic compression enhance the properties of chondrocyte‐ and MSC‐based tissue‐engineered cartilage

Adult chondrocytes are surrounded by a protein‐ and glycosaminoglycan‐rich extracellular matrix and are subjected to dynamic mechanical compression during daily activities. The extracellular matrix and mechanical stimuli play an important role in chondrocyte biosynthesis and homeostasis. In this study, we aimed to develop scaffold and compressive loading conditions that mimic the native cartilage micro‐environment and enable enhanced chondrogenesis for tissue engineering applications. Towards this aim, we fabricated porous scaffolds based on silk fibroin (SF) and SF with gelatin/chondroitin sulfate/hyaluronate (SF‐GCH), seeded the scaffolds with either human bone marrow mesenchymal stromal cells (BM‐MSCs) or chondrocytes, and evaluated their performance with and without dynamic compression. Human chondrocytes derived from osteoarthritic joints and BM‐MSCs were seeded in scaffolds, precultured for 1 week, and subjected to compression with 10% dynamic strain at 1 Hz, 1 hr/day for 2 weeks. When dynamic compression was applied, chondrocytes significantly increased expression of aggrecan (ACAN) and collagen X (COL10A1) up to fivefold higher than free‐swelling controls. In addition, dynamic compression dramatically improved the chondrogenesis and chondrocyte biosynthesis cultured in both SF and SF‐GCH scaffolds evidenced by glycosaminoglycan (GAG) content, GAG/DNA ratio, and immunostaining of collagen type II and aggrecan. However, both chondrocytes and BM‐MSCs cultured in SF‐GCH scaffolds under dynamic compression showed higher GAG content and compressive modulus than those in SF scaffolds. In conclusion, the micro‐environment provided by SF‐GCH scaffolds and dynamic compression enhances chondrocyte biosynthesis and matrix accumulation, indicating their potential for cartilage tissue engineering applications.     

An endochondral ossification approach to early stage bone repair: Use of tissue‐engineered hypertrophic cartilage constructs as primordial templates for weight‐bearing bone repair

Mimicking endochondral ossification to engineer constructs offers a novel solution to overcoming the problems associated with poor vascularisation in bone repair. This can be achieved by harnessing the angiogenic potency of hypertrophic cartilage. In this study, we demonstrate that tissue‐engineered hypertrophically primed cartilage constructs can be developed from collagen‐based scaffolds cultured with mesenchymal stem cells. These constructs were subsequently implanted into femoral defects in rats. It was evident that the constructs could support enhanced early stage healing at 4 weeks of these weight‐bearing femoral bone defects compared to untreated defects. This study demonstrates the value of combining knowledge of development biology and tissue engineering in a developmental engineering inspired approach to tissue repair.     

Enhanced treatment of articular cartilage defect of the knee by intra‐articular injection of Bcl‐xL‐engineered mesenchymal stem cells in rabbit model

Direct intra‐articular injection of mesenchymal stem cells (MSCs) has been proposed as a potential cell therapy for cartilage defects. This cell therapy relies on the survival of the implanted MSCs. However, the arduous local environment may limit cell viability after implantation, which would restrict the cells' regenerative capacity. Thus, it is necessary to reinforce the implanted cells against the unfavourable microenvironment in order to improve the efficacy of cell therapy. We examined whether the transduction of an anti‐apoptotic protein, Bcl‐xL, into MSCs could prevent cell death and improve the implantation efficiency of MSCs in a rabbit model. Our current findings demonstrate that the group treated with Bcl‐xL‐engineered MSCs could improve cartilage healing both morphologically and histologically when compared with the controls. These results suggest that intra‐articular injection of Bcl‐xL‐engineered MSCs is a potential non‐invasive therapeutic method for effectively treating cartilage defects of the knee. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of cell seeding concentration on the quality of tissue engineered constructs loaded with adult human articular chondrocytes

Many aspects of the process of in vitro differentiation of chondrocytes in three-dimensional (3D) scaffolds need to be further investigated. Chitosan scaffolds were produced by freeze-drying 3% w/v 90% DDA chitosan gels. The effect of the cell seeding concentration was evaluated by culturing human adult chondrocytes in chitosan scaffolds After the first passage, cells were seeded into chitosan scaffolds with a diameter of 8 mm. The final cell seeding concentration per cm3 of chitosan scaffold was: Group A, 3 x 10(6); Group B, 6 x 10(6); Group C, 12 x 10(6); and Group D, 25 x 10(6) cells. After 14 and 28 days in 3D culture, the constructs were assesed for collagen, glucosaminoglycans and DNA content. The mechanical properties of the constructs were determined using a dynamic oscillatory shear test. The histological aspect of the constructs was evaluated using the Bern score. The collagen and GAG concentration increased, varying the cell seeding concentration. There was a significant increase in proteoglycan and hydroxyproline production between groups C and D. The sulphated GAG content increased significantly in the group D as compared to the other groups. The mechanical properties of the different constructs increased over time, from 9.6 G'/kPa at 14 days of 3D culture to 14.6 G'/kPa at 28 days under the same culture conditions. In this study we were able to determine that concentrations of 12-25 million cells/cm2 are needed to increase the matrix production and mechanical properties of human adult chondrocytes under static conditions.     

PGA‐associated heterotopic chondrocyte cocultures: implications of nasoseptal and auricular chondrocytes in articular cartilage repair

The availability of autologous articular chondrocytes remains a limiting issue in matrix assisted autologous chondrocyte transplantation. Non‐articular heterotopic chondrocytes could be an alternative autologous cell source. The aims of this study were to establish heterotopic chondrocyte cocultures to analyze cell‐cell compatibilities and to characterize the chondrogenic potential of nasoseptal chondrocytes compared to articular chondrocytes. Primary porcine and human nasoseptal and articular chondrocytes were investigated for extracellular cartilage matrix (ECM) expression in a monolayer culture. 3D polyglycolic acid‐ (PGA) associated porcine heterotopic mono‐ and cocultures were assessed for cell vitality, types II, I, and total collagen‐, and proteoglycan content. The type II collagen, lubricin, and Sox9 gene expressions were significantly higher in articular compared with nasoseptal monolayer chondrocytes, while type IX collagen expression was lower in articular chondrocytes. Only β1‐integrin gene expression was significantly inferior in humans but not in porcine nasoseptal compared with articular chondrocytes, indicating species‐dependent differences. Heterotopic chondrocytes in PGA cultures revealed high vitality with proteoglycan‐rich hyaline‐like ECM production. Similar amounts of type II collagen deposition and type II/I collagen ratios were found in heterotopic chondrocytes cultured on PGA compared to articular chondrocytes. Quantitative analyses revealed a time‐dependent increase in total collagen and proteoglycan content, whereby the differences between heterotopic and articular chondrocyte cultures were not significant. Nasoseptal and auricular chondrocytes monocultured in PGA or cocultured with articular chondrocytes revealed a comparable high chondrogenic potential in a tissue engineering setting, which created the opportunity to test them in vivo for articular cartilage repair. Copyright © 2011 John Wiley & Sons, Ltd.     

Tissue‐engineered nanoclay‐based 3D in vitro breast cancer model for studying breast cancer metastasis to bone

Breast cancer (BrCa) preferentially spreads to bone and colonises within the bone marrow to cause bone metastases. To improve the outcome of patients with BrCa bone metastasis, we need to understand better the mechanisms underlying bone metastasis. Researchers have relied heavily upon in vivo xenografts due to limited availability of human bone metastasis samples. A significant limitation of these is that they do not have a human bone microenvironment. To address this issue, we have developed a nanoclay‐based 3D in vitro model of BrCa bone metastasis using human mesenchymal stem cells (MSCs) and human BrCa cells mimicking late stage of BrCa pathogenesis at the metastatic site. This 3D model can provide a microenvironment suitable for cell–cell and cell–matrix interactions whilst retaining the behaviour of BrCa cells with different metastasis potential (i.e., highly metastatic MDA‐MB‐231 and low metastatic MCF‐7) as shown by the production of alkaline phosphatase and matrix metalloproteinase‐9. The sequential culture of MSCs with MCF‐7 exhibited 3D tumouroids formation and also occurrence of mesenchymal to epithelial transition of cancer metastasis as evidenced by gene expression and immunocytochemistry. The unique and distinct behaviour of highly metastatic MDA‐MB‐231 and the low metastatic MCF‐7 was observed at the bone metastasis site. The changes to migratory capabilities and invasiveness in MDA‐MB‐231 in comparison with tumour growth with MCF‐7 was observed. Together, a novel bone‐mimetic 3D in vitro BrCa model has been developed that could be used to study mechanisms governing the later stage of cancer pathogenesis in bone.     

Boron nitride nanotube‐functionalised myoblast/microfibre constructs: a nanotech‐assisted tissue‐engineered platform for muscle stimulation

In this communication, we introduce boron nitride nanotube (BNNT)‐functionalised muscle cell/microfibre mesh constructs, obtained via tissue engineering, as a three‐dimensional (3D) platform to study a wireless stimulation system for electrically responsive cells and tissues. Our stimulation strategy exploits the piezoelectric behaviour of some classes of ceramic nanoparticles, such as BNNTs, able to polarize under mechanical stress, e.g. using low‐frequency ultrasound (US). In the microfibre scaffolds, C2C12 myoblasts were able to differentiate into viable myotubes and to internalize BNNTs, also upon US irradiation, so as to obtain a nanotech‐assisted 3D in vitro model. We then tested our stimulatory system on 2D and 3D cellular models by investigating the expression of connexin 43 (Cx43), as a molecule involved in cell crosstalk and mechanotransduction, and myosin, as a myogenic differentiation marker. Cx43 gene expression revealed a marked model dependency. In control samples (without US and/or BNNTs), Cx43 was upregulated under 2D culture conditions (10.78 ± 1.05‐fold difference). Interactions with BNNTs increased Cx43 expression in 3D samples. Cx43 mRNA dropped in 2D under the ‘BNNTs + US’ regimen, while it was best enhanced in 3D samples (3.58 ± 1.05 vs 13.74 ± 1.42‐fold difference, p = 0.0001). At the protein level, the maximal expressions of Cx43 and myosin were detected in the 3D model. In contrast with the 3D model, in 2D cultures, BNNTs and US exerted a synergistic depletive effect upon myosin synthesis. These findings indicate that model dimensionality and stimulatory regimens can strongly affect the responses of signalling and differentiation molecules, proving the importance of developing proper in vitro platforms for biological modelling. Copyright © 2014 John Wiley & Sons, Ltd.     

Cell factory‐derived bioactive molecules with polymeric cryogel scaffold enhance the repair of subchondral cartilage defect in rabbits

We have explored the potential of cell factory‐derived bioactive molecules, isolated from conditioned media of primary goat chondrocytes, for the repair of subchondral cartilage defects. Enzyme‐linked immunosorbent assay (ELISA) confirms the presence of transforming growth factor‐β1 in an isolated protein fraction (12.56 ± 1.15 ng/mg protein fraction). These bioactive molecules were used alone or with chitosan–agarose–gelatin cryogel scaffolds, with and without chondrocytes, to check whether combined approaches further enhance cartilage repair. To evaluate this, an in vivo study was conducted on New Zealand rabbits in which a subchondral defect (4.5 mm wide × 4.5 mm deep) was surgically created. Starting after the operation, bioactive molecules were injected at the defect site at regular intervals of 14 days. Histopathological analysis showed that rabbits treated with bioactive molecules alone had cartilage regeneration after 4 weeks. However, rabbits treated with bioactive molecules along with scaffolds, with or without cells, showed cartilage formation after 3 weeks; 6 weeks after surgery, the cartilage regenerated in rabbits treated with either bioactive molecules alone or in combinations showed morphological similarities to native cartilage. No systemic cytotoxicity or inflammatory response was induced by any of the treatments. Further, ELISA was done to determine systemic toxicity, which showed no difference in concentration of tumour necrosis factor‐α in blood serum, before or after surgery. In conclusion, intra‐articular injection with bioactive molecules alone may be used for the repair of subchondral cartilage defects, and bioactive molecules along with chondrocyte‐seeded scaffolds further enhance the repair. Copyright © 2015 John Wiley & Sons, Ltd.     

Enamel matrix derivative inhibits proteoglycan production and articular cartilage repair,delays the restoration of the subchondral bone and induces changes of the synovial membrane in a lapine osteochondral defect model in vivo

Improving the structural qualities of the new tissue that fills osteochondral defects is critical to enhance articular cartilage repair. Enamel matrix derivative (EMD) modulates chondrocyte proliferation and differentiation. In the present study, we assessed the effect of EMD on early chondrogenesis and bone repair in an osteochondral defect model in vivo. Standardized osteochondral defects were established in the trochlear groove of rabbits. EMD or the carrier substance without EMD activity was applied to the blood clot that was forming within the defect. After 3 weeks in vivo, the quality of articular cartilage repair was evaluated using a semiquantitative scoring system and biochemical assays for proteoglycan and DNA contents. The extent of formation of the subchondral bone within the original osteochondral defect was measured. Application of EMD resulted in an inferior histological articular cartilage repair. The total proteoglycan content of the repair tissue as well as the proteoglycan production standardized to the cell proliferative activities within the defects were reduced following treatment with EMD. Restoration of the subchondral bone within the osteochondral defect was delayed when EMD was applied. Significant changes of the synovial membrane were present, reflected in an increased villus thickening and changes in villus architecture. These data suggest that EMD inhibits the early repair of the osteochondral unit in vivo. Copyright © 2012 John Wiley & Sons, Ltd.     

动物源性骨软骨支架复合骨髓间充质干细胞/软骨细胞修复兔膝关节骨软骨复合缺损

背景:以往支架材料修复骨软骨的实验大都存在骨软骨耦合界面修复不良的情况.目的:观察骨髓间充质干细胞/软骨细胞复合动物源性骨软骨支架修复兔膝关节骨软骨复合缺损的可行性.方法:将新西兰大白兔随机抽签分为实验组、对照组、空白组,制作单侧膝关节骨软骨复合缺损后,实验组于骨缺损处植入自体骨髓间充质干细胞/诱导分化的软骨细胞与同种异体动物源性骨软骨复合支架,对照组于骨缺损处植入同种异体动物源性骨软骨支架、空白组未植入任何材料.术后4,8,12周行大体观察、苏木精-伊红染色、甲苯胺蓝染色.结果与结论:实验组大体观察见复合缺损区完全修复,局部无凹陷,新生组织和周围组织融合,苏木精-伊红染色和甲苯胺蓝染色见软骨缺损区由新生的透明软骨样组织修复,细胞柱状排列,极性好,软骨陷窝明显,骨缺损区由骨样组织修复,新生软骨和软骨下骨以及宿主骨界面耦合良好,甲苯胺蓝染色阳性率和组织学评分优于对照组、空白组(P < 0.05).说明诱导分化的自体软骨细胞和骨髓间充质干细胞共培养复合动物源性骨软骨支架所构建的细胞-支架复合体能成功修复兔膝关节软骨和软骨下骨的复合缺损,是一种理想的骨软骨复合缺损修复方法.