磷酸钙材料在骨软骨缺损修复支架中的应用

背景：磷酸钙材料与天然骨矿物质相似,具有良好的生物活性、骨传导性和可降解性,在金属植入物涂层及骨缺损修复材料中已有大量研究与应用。 目的：综述不同物相磷酸钙材料的特点及在骨软骨支架中的应用。 方法：应用计算机检索PubMed数据库、中国学术期刊网络出版总库、维普数据库2000年1月至2015年2月的有关文章,中文检索词为“骨软骨,磷酸钙(包括羟基磷灰石、磷酸三钙、聚磷酸钙等),组织工程”,英文检索词为“osteochondral;calcium phosphate;tissue engineering”。 结果与结论：由于磷酸钙具有多种物相和晶型,通过不同工艺方法调控磷酸钙的结构尺寸可以得到丰富的材料体系,如羟基磷灰石、磷酸三钙、聚磷酸钙、无定形磷酸钙等,其生物学性能和力学性能均有所差异,其中以羟基磷灰石的应用最为广泛。将磷酸钙与其他材料复合制备多层的复合支架是骨软骨组织工程研究的一个趋势。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

An anti-inflammatory cell-free collagen/resveratrol scaffold for repairing osteochondral defects in rabbits

Inflammatory factor overexpression is the major cause of cartilage and osteochondral damage. Resveratrol (Res) is known for its anti-inflammatory, antioxidant and immunmodulatory properties. However, these effects are hampered by its water insolubility and rapid metabolism in vivo. To optimize its therapeutic efficacy in this study, Res was grafted to polyacrylic acid (PAA, 1000 Da) to obtain a macromolecular drug, PAA-Res, which was then incorporated into atelocollagen (Coll) hydrogels to fabricate anti-inflammatory cell-free (Coll/Res) scaffolds with improved mechanical strengths. The Coll/Res scaffolds demonstrated the ability to capture diphenylpicrylhydrazyl free radicals. Both pure Coll and Coll/Res scaffolds could maintain their original shape for 6 weeks in phosphate buffered saline. The scaffolds were degraded by collagenase over several days, and the degradation rate was slowed down by Res loading. The Coll and Coll/Res scaffolds with excellent cytocompatibility were shown to promote the proliferation and maintain the normal phenotype of the seeded chondrocytes and bone marrow stromal stem cells (BMSCs). In addition, the Coll/Res scaffold exhibited the capacity to protect the chondrocytes and BMSCs against reactive oxygen species. The acellular Coll/Res scaffolds were transplanted into the rabbit osteochondral defects. After implantation for 2, 4 and 6 weeks, the samples were retrieved for quantitative real-time polymerase chain reaction, and the inflammatory related genes interleukin-1β, matrix metalloproteinases-13, COX-2 and bone and cartilage related genes SOX-9, aggrecan, Coll II and Coll I were determined. Compared with the untreated defects, the inflammatory related genes were down-regulated and those bone and cartilage related genes were up-regulated by filling the defect with an anti-inflammatory scaffold. After 12 weeks, the osteochondral defects were completely repaired by the Coll/Res scaffold, and the neo-cartilage integrated well with its surrounding tissue and subchondral bone. Immunohistochemical and glycosaminoglycan staining confirmed the distribution of Coll II and glycosaminoglycans in the regenerated cartilage. The anti-inflammatory acellular Coll/Res scaffolds are convenient to administer in vivo, holding a greater potential for future clinical applications.     

Evaluation of multiphase implants for repair of focal osteochondral defects in goats

The use of biodegradable scaffolds for articular cartilage repair has been investigated by numerous researchers. The objective of this screening study was to examine how the mechanical and physical properties of four multiphase implants can affect the cartilage healing response. Multiphase implant prototypes were prepared using poly(D,L)lactide-co-glycolide as the base material. PGA fibers (FR), 45S5 Bioglass (BG) and medical grade calcium sulfate (MGCS) were used as additives to vary stiffness and chemical properties. Osteochondral defects (3 mm dia. and 4 mm in depth) were created bilaterally in the medial femoral condyle (high-weight bearing) and the distal medial portion of the patellar groove (low-weight bearing) of 16 Spanish goats. Half of the implants were loaded with autologous costochondral chondrocytes. Defect sites (total n = 64, 4 sites/treatment) were randomly treated and allowed to heal for 16 weeks, fully weight bearing. At euthanasia, gross evaluations and biomechanical testing were conducted. Histological sections of the defect sites were stained with H and E, Safranin O/Fast Green or processed to analyze collagen architecture. Sections were semi-quantitatively scored for repair tissue structure. Qualitative evaluations showed that all groups had a high percentage of hyaline cartilage and good bony restoration, with new tissue integrating well with the native cartilage. Gross and histology scoring indicated a significantly higher score for defect healing in the condyle than in the patellar groove, but no difference in healing for implant types or addition/omission of cells was found. This investigation demonstrates that focal, osteochondral defects in caprine distal femurs treated with various implant constructs were repaired with hyaline-like cartilage and good underlying bone. The multiphase implants show potential for treatment of osteochondral defects and long-term studies need to be undertaken to confirm the longevity of the regenerated tissue.     

A biomimetic multi-layered collagen-based scaffold for osteochondral repair

Cartilage and osteochondral defects pose a significant challenge in orthopedics. Tissue engineering has shown promise as a potential method for the treatment of such defects; however, a long-lasting repair strategy has yet to be realized. This study focuses on the development of a layered construct for osteochondral repair, fabricated through a novel “iterative layering” freeze-drying technique. The process involved repeated steps of layer addition followed by freeze-drying, enabling control over material composition, pore size and substrate stiffness in each region of the construct, while also achieving a seamlessly integrated layer structure. The novel construct developed mimics the inherent gradient structure of healthy osteochondral tissue: a bone layer composed of type I collagen and hydroxyapatite (HA), an intermediate layer composed of type I collagen, type II collagen and HA and a cartilaginous region composed of type I collagen, type II collagen and hyaluronic acid. The material properties were designed to provide the biological cues required to encourage infiltration of host cells from the bone marrow while the biomechanical properties were designed to provide an environment optimized to promote differentiation of these cells towards the required lineage in each region. This novel osteochondral graft was shown to have a seamlessly integrated layer structure, high levels of porosity (>97%), a homogeneous pore structure and a high degree of pore interconnectivity. Moreover, homogeneous cellular distribution throughout the entire construct was evident following in vitro culture, demonstrating the potential of this multi-layered scaffold as an advanced strategy for osteochondral defect repair.     

Evaluation of early-stage osteochondral defect repair using a biphasic scaffold based on a collagen-glycosaminoglycan biopolymer in a caprine model

The aim of this study was to evaluate a new collagen-GAG-calcium phosphate biphasic scaffold for the repair of surgically created osteochondral defects in goats. Comparison of morphological, histological and mechanical performance of the repair tissue was made with defects repaired using a synthetic polymer scaffold. Defects were created in the medial femoral condyle (MFC) and lateral trochlear sulcus (LTS) of Boer Cross goats and evaluated at 12 and 26 weeks. It was found that the total histology score of the collagen-GAG based biomaterial (23.8; SD 1.7) provided a significant improvement (p<0.05) over the biphasic PLGA material (19;3) and the empty control defect (17.3;1.2) in the LTS. The overall trajectory of histological and morphological improvement between 12 and 26 weeks was found to be higher for the collagen-GAG scaffold compared to the PLGA material. The occurrence of sub-chondral bone cysts was lower for the collagen-GAG scaffold with an incidence of 17% of defects, compared to 67% for the PLGA material at 26 weeks. The cartilage repair tissue for both materials evaluated was superior after 26 weeks implantation than the empty control with 75% of the collagen-GAG-treated defects showing markedly more hyaline-like cartilage and 50% of the PLGA sites exhibiting hyaline-like appearances, compared to 17% for the empty control. These early stage data indicate biphasic scaffolds based on collagen-GAG and PLGA both provide indications of satisfactory development of a structural repair to surgically prepared osteochondral defects. Furthermore, the biomaterial composition of the collagen-GAG may provide a more favourable environment for osteochondral repair.     

Ectopic osteochondral formation of biomimetic porous PVA-n-HA/PA6 bilayered scaffold and BMSCs construct in rabbit

In this work, the novel poly vinyl alcohol/gelatin-nano-hydroxyapatite/polyamide6 (PVA-n-HA/PA6) bilayered scaffold with biomimetic properties for articular cartilage and subchondral bone is developed. Furthermore, when these osteochondral scaffolds were seeded with induced bone mesenchymal stem cells (BMSCs) and implanted at ectopic sites, showed the potential for an engineered cartilage tissue and the corresponding subchondral bone. BMSCs were expanded in vitro and induced to chondrogenic or osteogenic potential by culturing in suitable media for 14 days. Subsequently, these induced cells were seeded into PVA-n-HA/PA6 separately, and the constructs were implanted into the rabbit muscle pouch for upto 12 weeks. Ectopic neocartilage formation in the PVA layer and reconstitution of the subchondral bone which remained confined within the n-HA/PA6 layer with the alteration of the cellular phenotype were identified with Masson's trichrome stain. Simultaneously, the RT-PCR results confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous tissue, such as collagen type II (Col-II), or alternatively, markers for osteoid tissue, such as collagen type I (Col-I) at the corresponding layers. During ectopic implantation, the underlying subchondral bone layer was completely integrated with the cartilage layer. The result from the ectopic osteochondral scaffolds implantation suggests that PVA-n-HA/PA6 with induced BMSCs is a possible substitute with potential in cartilage repair strategies.     

多孔丝素蛋白支架修复兔下颌骨临界性骨缺损

背景：丝素蛋白具有良好的生物相容性和可降解性。 目的：观察多孔丝素蛋白支架原位修复兔下颌骨临界性骨缺损效果。 方法：建立兔双侧下颌骨临界性骨缺损模型,随机选取一侧缺损植入多孔丝素蛋白支架作为实验组,另一侧缺损不作处理作为对照组。 结果与结论：①大体标本：术后12周,实验组骨缺损腔表面完全被新生骨覆盖,材料无脱出;对照组骨缺损腔内充满肉芽组织,骨不连。②X射线骨密度测定：术后2,6,12周,两组骨密度均随着时间延长逐渐增高,组内不同时间点间差异有显著性意义(P < 0.05),且同期实验组高于对照组(P < 0.05)。③组织病理切片苏木精-伊红染色：术后12周,实验组岛状新生骨及骨小梁明显增多,而且粗大而致密,材料内部明显疏松,部分区域塌陷;对照组宿主骨边缘可见散在分布的新生骨组织,但并无粗大骨小梁形成。④骨形态发生蛋白2免疫组织化学染色：术后2,6,12周,两组骨形态发生蛋白2阳性细胞数均随着时间延长逐渐增多,组内不同时间点间差异有显著性意义(P < 0.05),且同期实验组多于对照组 (P < 0.05)。表明多孔丝素蛋白支架用于原位组织工程修复骨缺损具有一定可行性。     

Radially oriented collagen scaffold with SDF-1 promotes osteochondral repair by facilitating cell homing

The migration of cells from the side and the bottom of the defect is important in osteochondral defect healing. Here, we designed a novel collagen scaffold that possessed channels in both the horizontal and the vertical directions, along with stromal cell-derived factor-1 (SDF-1) to enhance osteochondral regeneration by facilitating cell homing. Firstly we fabricated the radially oriented and random collagen scaffolds, then tested their properties. The radially oriented collagen scaffold had better mechanical properties than the random scaffold, but both supported cell proliferation well. Then we measured the migration of BMSCs in the scaffolds in vitro. The radially oriented collagen scaffold effectively promoted their migration, and this effect was further facilitated by addition of SDF-1. Moreover, we created osteochondral defects in rabbits, and implanted them with random or oriented collagen scaffolds with or without SDF-1, and evaluated cartilage and subchondral bone regeneration at 6 and 12 weeks after surgery. Cartilage regeneration with both the radially oriented scaffold and SDF-1 effectively promoted repair of the cartilage defect. Our results confirmed that the implantation of the radially oriented channel collagen scaffold with SDF-1 could be a promising strategy for osteochondral repair.     

Repair of osteochondral defects in rabbits with ectopically produced cartilage

Cartilage has poor regenerative capacity. Donor site morbidity and interference with joint homeostasis should be considered when applying the autologous chondrocyte transplantation technique. The use of ectopically produced cartilage, derived from periosteum, might be a novel method to heal cartilage defects. Ectopic cartilage was produced by dissecting a piece of periosteum from the tibia of rabbits. After 14 days the reactive tissue at the dissection site was harvested and a graft was cored out and press-fit implanted in an osteochondral defect in the medial condyle of the femur with or without addition of hyaluronan. After 3 weeks and 3 months the repair reaction was evaluated by histology. Thionine- and collagen type II-stained sections were evaluated for graft viability, ingrowth of the graft, and joint surface repair. Empty defects remained empty 3 weeks after implantation, ectopic cartilage filled the defect to the level of the surrounding cartilage. Histologically, the grafts were viable, consisting mainly of cartilage, and showed a variable pattern of ingrowth. Three months after implantation empty defects with or without hyaluronan were filled primarily with fibrocartilaginous tissue. Defects treated with ectopic cartilage contained mixtures of fibrocartilaginous and hyaline cartilage. Sometimes a tidemark was observed in the new articular cartilage and the orientation of the cells resembled that of healthy articular cartilage. Subchondral bone repair was excellent. The modified O'Driscoll scores for empty defects without and with hyaluronan were 12.7 +/- 6.4 and 15.3 +/- 3.2; for treated defects scores were better (15.4 +/- 3.9 and 18.2 +/- 2.9). In this conceptual study the use of ectopic cartilage derived from periosteum appears to be a promising novel method for joint surface repair in rabbits.     

Prediction of the optimal mechanical properties for a scaffold used in osteochondral defect repair

The optimal mechanical properties of a scaffold to promote cartilage generation in osteochondral defects in vivo are not known. During normal daily activities cartilage is subjected to large cyclic loads that not only facilitate nutrient transport and waste removal through the dense tissue but also act as a stimulus to the chondrocytes. In contrast, cartilage tissue is commonly engineered in vitro in a static culture; hence, in many cases, the properties of scaffolds have been tailored to suit this in vitro environment. In this study, a mechanoregulation algorithm for tissue differentiation was used to determine the influence of scaffold material properties on chondrogenesis in a finite element model of an osteochondral defect. It is predicted that increasing the stiffness of the scaffold increases the amount of cartilage formation and reduces the amount of fibrous tissue formation in the defect, but this only holds true up to a certain threshold stiffness above which the amount of cartilage formed is reduced. Reducing the permeability of the scaffold was also predicted to be beneficial. Considering a nonhomogeneous scaffold, an optimal design was determined by parametrically varying the mechanical properties of the scaffold through its depth. The Young's modulus reduced nonlinearly from the superficial region through the depth of the scaffold, while the permeability of the scaffold was lowest in the superficial region. As tissue engineering moves from a science toward a product, engineering design becomes more relevant, and predictive models such as that presented here can provide a scientific basis for design choices.     

可控释淫羊藿苷的羟基磷灰石/壳聚糖缓释支架修复骨缺损*

 背景：如何将中药有效活性化合物通过生物支架材料的缓释作用更好的应用于骨科临床尚需大量的研究。目的：通过文献检索和综合分析,客观评估中药活性成分复合淫羊藿苷的缓释支架在骨修复领域应用的可行性。方法：分别用英文检索词“bone defect,icariin,release bracket,chitosan,hydroxyapatite”;中文检索词“骨缺损,淫羊藿苷,壳聚糖,羟基磷灰石,缓释支架”检索CNKI及PubMed数据库1995-01/2010-12相关文章,纳入和研究目的相关的文章进行分析综述。结果与结论：共纳入相关文献24篇,已有研究表明中药淫羊藿苷可促进成骨细胞的生成,抑制骨吸收。而纳米羟基磷灰石-壳聚糖复合支架具有良好的理化性质和细胞相容性,可以应用于组织工程骨的构建。因此在进一步完善纳米级晶体合成工艺的基础上,对淫羊藿苷的释放速度和释放模式加以控制,达到持续、稳定的药物缓释是可行的。     

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.     

Repair of osteochondral defects with autologous chondrocytes seeded onto bioceramic scaffold in sheep

At present, the most popular biomaterials used in cartilage tissue engineering are synthetic polymers. However, problems-such as acidic by-product accumulation and side effects in local or systemic inflammatory reactions during in vivo degradation-are drawing much attention. The polymers are also highly hydrophobic and degrade within 4 weeks, allowing insufficient time to support neocartilage formation. All these have made polymers less promising in clinical application. In this study, we tested a new bioceramic scaffold made of artificial synthesized powder of beta-tricalcium phosphate (beta-TCP) in a sheep model. Osteochondral defects were filled with a bioceramic-chondrocyte construct and neocartilage tissue completely resurfaced the cartilage defects after 24 weeks. Typical hyaline cartilage structure was generated in the engineered cartilage. Biodegradation of bioceramic was notable, leading to bioceramic fragmentation and particle formation. Numerous ceramic particles (size, 0.5-1.9 microm) and numerous macrophages were observed at the ceramic-tissue interface as well as in the marrow tissue. No macrophages were visible in the neocartilage tissue. Although long-term in vivo study is needed to further determine the pathological sequences of the beta-TCP-based cartilage construct, this study suggests that this bioceramic might be used to repair chondral or osteochondral defects and could be used as a scaffold for cartilage tissue engineering.     

羟基丁酸-羟基辛酸共聚体/胶原骨软骨一体化支架修复膝关节软骨损伤

BACKGROUND: Due to the complex physiological characteristics of the osteochondral tissue, the clinical repair of knee cartilage injury often has dissatisfied outcomes. Tissue engineering methods and tools provide a new idea for osteochondral repair. OBJECTIVE: To observe the effect of poly(hydroxybutyrate-co-hydroxyoctanoate/collagen) osteochondral tissue-engineered scaffold on the repair of articular cartilage injury in a rabbit. METHODS: The poly(hydroxybutyrate-co-hydroxyoctanoate/collagen) osteochondral tissue-engineered scaffold was prepared by solvent casting/particle leaching method. Then, seed cells were isolated and cultured on the scaffold. Twenty-four healthy New Zealand white rabbits, 4 weeks of age, were used for the study. Under balanced anesthesia, an articular cartilage defect (4.5 mm in diameter, 5 mm in depth) was created on the rabbit’s femoral condyle using a bone drill. After modeling, rabbits were randomized into three groups and given direct suture in blank group, pure scaffold implantation in control group and implantation of the scaffold-cell complex in experimental group. Femoral condyle of each rabbit was taken out for gross and histological observations at 8, 20 weeks after surgery. RESULTS AND CONCLUSION: At 8 weeks after surgery, transparent film-covered defects and small/irregular cells were found in the experimental group; the defects were filled with fibrous tissues in the control group; while there was no repair in the blank group. Until the 20th week, the defects were covered with hyaline cartilage-like tissues, accompanied by regular cell arrangement in the experimental group; in the control group, the defects were covered with white membranous tissues, and many chondrocytes were found at the basement and edge; in the blank group, some newborn tissues were visible at the defect region. These findings suggest that the poly (hydroxybutyrate-co- hydroxyoctanoate/collagen) osteochondral tissue-engineered scaffold carrying seed cells contributes to articular cartilage repair.     

Cell-based therapy in the repair of osteochondral defects: a novel use for adipose tissue

Mesenchymal stem cells are currently procured from periosteum and bone marrow. The procurement of stem cells from these sources is tedious and gives a low yield of cells. This study was aimed at circumventing these problems and allowing for a method that would be more acceptable in the clinical setting. Tissue for transplantation was harvested from a single New Zealand White rabbit. Cells were more readily obtained from adipose tissue than from bone marrow or periosteum. The present method also provided a better yield of cells through culture. In vitro studies were performed to assess the differentiation potential of these cells. Successful in vitro transformation into alternative mesenchymal cell lines including cardiomyocytes revealed these cells to have wide differentiation potential. Further characterization morphologically, immunohistochemically, and via gene transfection showed features consistent with mesenchymal stem cells. Cultured cells were then transplanted into defects created in the left medial femoral condyle. The femora were harvested at various intervals and the repair tissue was assessed. Gross osteochondral defect reconstitution and histological grading was superior to periosteum-derived stem cell repair and repair by native mechanisms. Biomechanically, the repair tissue approximated intact cartilage and was superior to osteochondral autografts and repair by innate mechanisms.     

丝素蛋白支架修复颊黏膜缺损

BACKGROUND: Fibroin is a natural macromolecular material with Arg-Gly-Asp peptide structure that is a special tripeptide structure closely related to cell adhesion, and it can promote cell migration, adhesion, and proliferation and influence cell morphology and function. OBJECTIVE: To compare the effects of different silk fibroin scaffolds to repair buccal mucosa defects in rats. METHODS: Ninety Sprague-Dawley rats were selected to make unilateral buccal mucosa defect models, and randomly divided into three groups, 30 rats in each group: porous silk fibroin scaffold was implanted into the buccal mucosa defect in experimental group, multi-layered crosslinked silk fibroin film was implanted into the buccal mucosa defect in control group, and vaseline gauze was used to cover the buccal mucosa defect followed by suturing in blank control group. After 15 days, wound diameter was detected; after 30 days, bone defect tissues were taken for hematoxylin-eosin staining. RESULTS AND CONCLUSION: At postoperative 15 days, the wound diameter was significantly smaller in the experimental group than the control and blank control groups (P < 0.05), as well as smaller in the control group than the blank control group (P < 0.05). Hematoxylin-eosin staining showed that at 30 days after operation, there were more epithelial spikes and fibroblasts, but less inflammatory cells in the experimental group than the other two groups (P < 0.05), and fibroin fibers were partially absorbed and degraded in the experimental group. These findings indicate that porous silk fibroin scaffold for buccal mucosa defect repair can accelerate epithelialization and wound healing.       

组织工程骨膜包被双相陶瓷磷酸钙修复兔尺骨缺损

BACKGROUND: Periosteum has been shown to play an important role in bone defect repair, but large bone defects are often accompanied by the loss of periosteum. Therefore, tissue-engineered periosteum constructed by tissue engineering technology is attracting more attention. OBJECTIVE: To investigate the effect of the tissue-engineered periosteum which is constructed by mesenchymal stem cells from the peripheral blood and procine small intestinal submucosa and biphasic calcium phosphates on the repair of bone defects in rabbits. METHODS: Mesenchymal stem cells from peripheral blood were seeded onto the procine small intestinal submucosa to construct the tissue-engineered periosteum, and then the cell growth was observed through live/dead staining. The bone defect model of 15 mm in length in the left ulna was created in the 30 healthy New Zealand rabbits, followed by randomly assigned to 3 groups, and then treated with biphasic calcium phosphates and tissue-engineered periosteum-coated biphasic calcium phosphates, respectively. The remaining rabbits received no treatment as controls. Therapeutic effects were compared by X-ray and histological examinations among groups. RESULTS AND CONCLUSION: Live/dead staining found that the mesenchymal stem cells grew well and the cell number increased gradually. X-ray Lane-Sandhu scores of the group treated with tissue-engineered periosteum-coated biphasic calcium phosphates were highest, followed by the biphasic calcium phosphates group and the control group at postoperative 4 and 8 weeks (P < 0.05). Histological examination showed that the group treated with tissue-engineered periosteum-coated biphasic calcium phosphates had more osteoblasts, compared with the other two groups. In conclusion, the biphasic calcium phosphate scaffold coated by the tissue-engineered periosteum that is constructed by mesenchymal stem cells from peripheral blood and procine small intestinal submucosa is feasible to repair bone defects.      

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.     

Autologous chondrocyte implantation with collagen bioscaffold for the treatment of osteochondral defects in rabbits

Osteochondral injury is therapeutically irreversible within current treatment parameters. Autologous chondrocyte implantation (ACI) promises to regenerate hyaline articular cartilage, but conventional ACI is plagued by complications determined by periosteal grafting. Here we propose the utilization of collagen membrane in ACI as an effective bioscaffold for the regeneration of osteochondral lesions. Using a rabbit model of osteochondral injury, we have inoculated autologous chondrocytes onto a type I/III collagen scaffold [so-called matrix-induced ACI (MACI)] and implanted into 3-mm osteochondral knee defects. All untreated defect histology showed inferior fibrocartilage and/or fibrous tissue repair. In our time-course study, ACI with type I/III collagen membrane regenerated cartilage with healthy osteochondral architecture in osteochondral defects at 6 weeks. At 12 weeks, articular cartilage regeneration was maintained, with reduced thickness and proteoglycan compared with the adjacent cartilage. Both 6-week (p < 0.01) and 12-week (p < 0.05) ACI with collagen membrane showed significant improvement as compared with untreated controls. To further examine the efficacy of cartilage regeneration by ACI, we conducted a dose-response study, using chondrocytes at various cell densities between 10(4) and 10(6) cells/cm(2). The results showed that cell density had no effect on outcome histology, but all cell densities were significantly better than untreated controls (p < 0.01) and cell-free collagen membrane treatment (p < 0.05). In short, our data suggest that autologous chondrocyte-seeded type I/III collagen membrane is an effective method for the treatment of focal osteochondral knee injury in rabbits.     

PEOT/PBT based scaffolds with low mechanical properties improve cartilage repair tissue formation in osteochondral defects

The aim of our study was to compare the healing response of biomechanically and biochemically different scaffolds in osteochondral defects created in rabbit medial femoral condyles. A block copolymer comprised of poly(ethylene oxide terephthalate) and poly(butylene terephthalate) was used to prepare porous scaffolds. The 70/30 scaffold (70 wt % poly(ethylene oxide terephthalate)) was compared to the stiffer 55/45 (55 wt % poly(ethylene oxide terephthalate)) scaffold. Nine 6-month-old rabbits were used. Osteochondral defects were filled with 55/45 scaffolds (n = 6); 70/30 scaffolds (n = 6); or left empty (n = 6). Defect sites were allowed to heal for 12 weeks. Condyles were macroscopically evaluated and analysed histologically using the O'Driscoll score for evaluating repair of osteochondral defects. Repair tissue in 70/30 scaffolds consisted of cartilage-like tissue on top of trabecular bone, whereas the tissue within the 55/45 scaffolds consisted predominantly of trabecular bone. O'Driscoll scores for 70/30 scaffolds were significantly better (p = 0.024) in comparison to untreated osteochondral defects and 55/45 scaffolds. This study reveals that the biomechanical and biochemical properties of the scaffold play an important role by themselves, and can affect the healing response of osteochondral defects. Scaffolds with low mechanical properties were superior in cartilage repair tissue formation.