Corticosteroids are prescribed for the treatment of many medical conditions and their adverse effects on bone, including steroid-associated osteoporosis and osteonecrosis, are well documented. Core decompression is performed to treat osteonecrosis, but the results are variable. As steroids may affect bone turnover, this study was designed to investigate bone healing within a bone tunnel after core decompression in an experimental model of steroid-associated osteonecrosis. A total of five 28-week-old New Zealand rabbits were used to establish a model of steroid-induced osteonecrosis and another five rabbits served as controls. Two weeks after the induction of osteonecrosis, core decompression was performed by creating a bone tunnel 3 mm in diameter in both distal femora of each rabbit in both the experimental osteonecrosis and control groups. An in vivo micro-CT scanner was used to monitor healing within the bone tunnel at four, eight and 12 weeks postoperatively. At week 12, the animals were killed for histological and biomechanical analysis. In the osteonecrosis group all measurements of bone healing and maturation were lower compared with the control group. Impaired osteogenesis and remodelling within the bone tunnel was demonstrated in the steroid-induced osteonecrosis, accompanied by inferior mechanical properties of the bone. We have confirmed impaired bone healing in a model of bone defects in rabbits with pulsed administration of corticosteroids. This finding may be important in the development of strategies for treatment to improve the prognosis of fracture healing or the repair of bone defects in patients receiving steroid treatment

Objectives. Recent studies have shown that systemic injection of rapamycin can prevent the development of osteoarthritis (OA)-like changes in human chondrocytes and reduce the severity of experimental OA. However, the systemic injection of rapamycin leads to many side effects. The purpose of this study was to determine the effects of intra-articular injection of Torin 1, which as a specific inhibitor of mTOR which can cause induction of autophagy, is similar to rapamycin, on articular cartilage degeneration in a rabbit osteoarthritis model and to investigate the mechanism of Torin 1’s effects on experimental OA. Methods. Collagenase (type II) was injected twice into both knees of three-month-old rabbits to induce OA, combined with two intra–articular injections of Torin 1 (400 nM). Degeneration of articular cartilage was evaluated by histology using the Mankin scoring system at eight weeks after injection. Chondrocyte degeneration and autophagosomes were observed by transmission electron microscopy. Matrix metallopeptidase-13 (MMP-13) and vascular endothelial growth factor (VEGF) expression were analysed by quantitative RT-PCR (qPCR).Beclin-1 and light chain 3 (LC3) expression were examined by Western blotting. Results. Intra-articular injection of Torin 1 significantly reduced degeneration of the articular cartilage after induction of OA. Autophagosomes andBeclin-1 and LC3 expression were increased in the chondrocytes from Torin 1-treated rabbits. Torin 1 treatment also reduced MMP-13 and VEGF expression at eight weeks after collagenase injection. Conclusion. Our results demonstrate that intra-articular injection of Torin 1 reduces degeneration of articular cartilage in collagenase-induced OA, at least partially by autophagy activation, suggesting a novel therapeutic approach for preventing cartilage degeneration and treating OA. Cite this article: N-T. Cheng, A. Guo, Y-P. Cui. Intra-articular injection of Torin 1 reduces degeneration of articular cartilage in a rabbit osteoarthritis model. Bone Joint Res 2016;5:218–224. DOI: 10.1302/2046-3758.56.BJR-2015-0001

Objectives. The purpose of this study was to evaluate chronological changes in the collagen-type composition at tendon–bone interface during tendon–bone healing and to clarify the continuity between Sharpey-like fibres and inner fibres of the tendon. Methods. Male white rabbits were used to create an extra-articular bone–tendon graft model by grafting the extensor digitorum longus into a bone tunnel. Three rabbits were killed at two, four, eight, 12 and 26 weeks post-operatively. Elastica van Gieson staining was used to colour 5 µm coronal sections, which were examined under optical and polarised light microscopy. Immunostaining for type I, II and III collagen was also performed. Results. Sharpey-like fibres comprised of type III collagen in the early phase were gradually replaced by type I collagen from 12 weeks onwards, until continuity between the Sharpey-like fibres and inner fibres of the tendon was achieved by 26 weeks. Conclusions. Even in rabbits, which heal faster than humans, an observation period of at least 12 to 26 weeks is required, because the collagen-type composition of the Sharpey-like fibre bone–tendon connection may have insufficient pullout strength during this period. These results suggest that caution is necessary when permitting post-operative activity in humans who have undergone intra-bone tunnel grafts

Introduction. The rabbit common calcanean (Achilles) tendon is a compound apparatus frequently used in studies considering novel interventions to facilitate tendon regeneration. These studies often employ complete surgical transection of the apparatus. Due consideration of the translational relevance to human tendinopathy is often lacking and refinement of this injury model, consistent with the principles of the 3Rs, has not been forthcoming. Materials and Methods. Wild rabbit cadavers (n=10) were obtained from a licensed game dealer. For gross anatomy studies the caudal crus was dissected and transverse sections obtained every 5 mm. Ultrasongraphic examination of the entire apparatus was peformed with a 15 Hz transducer in transverse sections. Results. This study reannotates the apparatus and demonstrates that the principal structures, the superficial digital flexor tendon and medial and lateral gastrocnemius tendons, may be clearly identified by ultrasonographic examination. Discussion. Historical descriptions of the rabbit Achilles apparatus are shown to be inaccurate and follow human gross anatomical descriptions. Ultrasonographic identification of the constituent structures in the rabbit are poorly represented in the literature. Reference measurements and qualitative descriptions are provided that may facilitate the development of refined surgical techniques for in vivo studies of tendon regeneration in the rabbit beyond crude transection studies

Meniscus has many important functions in the knee joint such as load bearing, shock absorption, joint stability, joint lubrication and proprioception. In the recent years, meniscus injuries have been the focus of orthopaedic surgeons and musculoskeletal tissue engineering applications because of its avascular nature. In this study, we aimed to compare the regeneration capacities of two composite scaffolds in a New Zealand Rabbit meniscal defect model. The first scaffold consists Poly-Lactic Acid (PLA) + chitosan + loofah and the second PLA + Hydroxyapatite (HAp) + loofah. In order to produce these scaffolds; 4% chitosan, 4% PLA and 4% HAp solutions were seperately prepared. The loofah pieces were saturated with these solutions and vacuum-dried for 14 days and sterilized with ethylene oxide. There were several characterizations performed such as Fourier Transform Infrared Spectroscopy (FTIR) for the investigation of chemical structure, Scanning Electron Microscopy (SEM) for morphological analysis, thermogravimetric differential thermal analysis (TGA/DTA) for thermal properties, mechanical compression and swelling ratio analysis. Moreover, in order to investigate biocompatibility of the scaffolds, WST-1 colorimetric assay at days 3, 7, 10, 14 and 21 was conducted. After these biocompatibility analysis, a 1.5-mm cylindrical defect was created in the avascular portion of the anterior horn of the medial meniscus in 14 New Zealand rabbits (2.5–3 kg weight) which were randomly grouped in two. The scaffolds were implanted at the defect site with the help of a freshly prepared fibrin glue. 8 weeks after the operation, the rabbits were sacrificed and their tissues were kept for further mechanical, radiological and histological analysis. In conclusion, we succeeded to produce a new meniscus scaffold. The proliferation ability of PLA + chitosan + loofah scaffold is higher than PLA + HAp + loofah scaffold. However, there was no statistically significant difference among them

Objectives. Sustained intra-articular delivery of pharmacological agents is an attractive modality but requires use of a safe carrier that would not induce cartilage damage or fibrosis. Collagen scaffolds are widely available and could be used intra-articularly, but no investigation has looked at the safety of collagen scaffolds within synovial joints. The aim of this study was to determine the safety of collagen scaffold implantation in a validated in vivo animal model of knee arthrofibrosis. Materials and Methods. A total of 96 rabbits were randomly and equally assigned to four different groups: arthrotomy alone; arthrotomy and collagen scaffold placement; contracture surgery; and contracture surgery and collagen scaffold placement. Animals were killed in equal numbers at 72 hours, two weeks, eight weeks, and 24 weeks. Joint contracture was measured, and cartilage and synovial samples underwent histological analysis. Results. Animals that underwent arthrotomy had equivalent joint contractures regardless of scaffold implantation (-13.9° versus -10.9°, equivalence limit 15°). Animals that underwent surgery to induce contracture did not demonstrate equivalent joint contractures with (41.8°) or without (53.9°) collagen scaffold implantation. Chondral damage occurred in similar rates with (11 of 48) and without (nine of 48) scaffold implantation. No significant difference in synovitis was noted between groups. Absorption of the collagen scaffold occurred within eight weeks in all animals. Conclusion. Our data suggest that intra-articular implantation of a collagen sponge does not induce synovitis or cartilage damage. Implantation in a native joint does not seem to induce contracture. Implantation of the collagen sponge in a rabbit knee model of contracture may decrease the severity of the contracture. Cite this article: J. A. Walker, T. J. Ewald, E. Lewallen, A. Van Wijnen, A. D. Hanssen, B. F. Morrey, M. E. Morrey, M. P. Abdel, J. Sanchez-Sotelo. Intra-articular implantation of collagen scaffold carriers is safe in both native and arthrofibrotic rabbit knee joints. Bone Joint Res 2016;6:162–171. DOI: 10.1302/2046-3758.63.BJR-2016-0193

Growth plates taken from five- to 20-week-old Japanese white rabbits were immunostained for c-Myc protein. This was localised both in the proliferating zone and upper hypertrophic zone at five weeks, whereas after ten weeks it was found mostly in the lower hypertrophic zone. The proliferating chondrocytes tended to show nuclear staining and the hypertrophic cells cytoplasmic staining, although the terminal hypertrophic chondrocytes sometimes expressed the protein in their nuclei. In the younger rabbits, c-Myc co-localised with proliferating cell nuclear antigen, whereas in the hypertrophic zone of older rabbits, it was present in some chondrocytes the nuclei of which also contained DNA breaks. Our study suggests that, in the rabbit growth plate, c-Myc is associated with different cellular processes, depending on the age and the developmental stage of the chondrocytes

Summary Statement. The implantation of scaffold-free CTE from suspension culture into growth-plate defects resulted in a significant reduction in growth arrest of the rabbit tibia. Introduction. In childhood and adolescence, the growth plate injury can cause partial premature arrest of growth plate, which can make problems such as leg length discrepancy and angular deformity. Bone bridge resection and variable implantation materials such as fat, bone wax, silastic and craniopalst has been investigated. However, those procedures may show limitations including the control of bone growth and long term safety of implant materials in vivo. As an alternative, homogeneous or heterogeneous cartilage cells and stem cell transplants have been tried. In this method, scaffold for cell transplantation is needed. But, so far the most suitable scaffold has not been established. Recently, some authors generated a cartilage tissue equivalent (CTE) using a suspension culture with biophysical properties similar to native hyaline cartilage. Therefore we are able to transplant the CTE without scaffold to the physeal defect. The purpose of this study was to investigated the effects of a transplantation of a vitro-generated scaffold-free tissue-engineered cartilage tissue equivalent (CTE) using a suspension chondrocyte culture in a rabbit growth arrest model. Material and Method. Cartilage tissue equivalent culture. The CTE was generated by the suspension culture of chondrocytes (2 × 10. 7. /well/1 mL) which was isolated from articular cartilage of 5 weeks New Zealand white rabbit on a 24-well plate (2.4 cm. 2. /well) treated with poly HEMA (nunc, Roskide, Denmark) for up to 8 and 16 weeks. (2)Partial growth arrest animal model. An experimental model for growth arrest was created by excising the growth plate at the proximal medial side of tibia with the 4 mm in diameter and 4 mm in depth from 6-week-old New Zealand white rabbits. Two experimental groups were set to evaluate CTE implantation; group I, no implantation as controls; group II, implantation of CTE. (3) Evaluation of effect of the transplantation of CTE. Serial plain radiographs were performed at one week. The medial proximal tibial angle (MPTA) was measured for assessing the degree of angular deformity. Histologic examination using HE stain, Alcian bule and immunohistochemistry was done at 4 and 8 weeks after surgery. Results. Radiographic results: In group I, all damaged growth plates were arrested and angular deformities appeared 4 weeks later. In groups II, angular deformities were much less than in the control group. Histologic result: In group I, bone bridge formation was shown at the damaged growth plate at 4 weeks after surgery. In group II, regeneration of growth plates was recognised at 4 and 8 week after surgery. However, the thickness of regenerated growth plate at 8 weeks specimen was thinner than that of 4 weeks specimen. Discussion and Conclusion. The implantation of scaffold-free CTE from suspension culture into growth-plate defects resulted in a significant reduction in growth arrest of the rabbit tibia

We produced large full-thickness articular cartilage defects in 33 rabbits in order to evaluate the effect of joint distraction and autologous culture-expanded bone-marrow-derived mesenchymal cell transplantation (ACBMT) at 12 weeks. After fixing the knee on a hinged external fixator, we resected the entire surface of the tibial plateau. We studied three groups: 1) with and without joint distraction; 2) with joint distraction and collagen gel, and 3) with joint distraction and ACBMT and collagen gel. The histological scores were significantly higher in the groups with ACBMT collagen gel (p < 0.05). The area of regenerated soft tissue was smaller in the group allowed to bear weight (p < 0.05). These findings suggest that the repair of large defects of cartilage can be enhanced by joint distraction, collagen gel and ACBMT

In a rabbit model we investigated the efficacy of a silk fibroin/hydroxyapatite (SF/HA) composite on the repair of a segmental bone defect. Four types of porous SF/HA composites (SF/HA-1, SF/HA-2, SF/HA-3, SF/HA-4) with different material ratios, pore sizes, porosity and additives were implanted subcutaneously into Sprague-Dawley rats to observe biodegradation. SF/HA-3, which had characteristics more suitable for a bone substitite based on strength and resorption was selected as a scaffold and co-cultured with rabbit bone-marrow stromal cells (BMSCs). A segmental bone defect was created in the rabbit radius. The animals were randomised into group 1 (SF/HA-3 combined with BMSCs implanted into the bone defect), group 2 (SF/HA implanted alone) and group 3 (nothing implanted). They were killed at four, eight and 12 weeks for visual, radiological and histological study. The bone defects had complete union for group 1 and partial union in group 2, 12 weeks after operation. There was no formation of new bone in group 3. We conclude that SF/HA-3 combined with BMSCs supports bone healing and offers potential as a bone-graft substitute

Introduction. The objective of this study was to identify fat emboli in the arterioles of the femoral bone marrow by Scanning Electron Microscopy (SEM) after glucocorticoid administration. Methods. Female adult rabbits weighing 3.5 to 4.0 kg received a single injection of prednisolone at a dose of 4 mg/kg body weight. The day after injection was designated as day 1. Control rabbits were injected with only physiological saline and euthanized on day 14. The femoral bone marrow was obtained on days 5, 8, and 14, and processed for SEM. Aortic blood serum was passed through a filter, and the filter was processed for SEM. Some SEM specimens were embedded in a plastic resin and sectioned for correspondence of SEM-photomicroscopy or SEM-TEM. Results. In the controls, small fat globules were present in sinusoids and venules, but were absent from the arterioles. On day 5, fat globules were found in the lumina of both sinusoids and arterioles. Complete arteriolar occlusion was not found. On day 8, fat globules were often encountered in the venous and arteriolar lumina. Some small arterioles were completely occluded by fat emboli. On day 14, fat globules were present in the arterioles and some small and large arterioles were completely occluded. Blood drawn from the aorta contained fat globules in both the controls and rabbits injected with prednisolone. Conclusion. A small amount of prednisolone induced the presence of fat globules in arterioles as early as day 5, complete occlusion of small arterioles on day 8, and occlusion of large arterioles on day 14. The source of fat globules and the mechanism of arteriolar occlusion were discussed

Summary Statement. We observed that severe muscle weakness leads to OA, whereas a transient inflammatory stimulus did not have a significant effect on cartilage degradation. This arises the thought that a severe but transient inflammation may not be an independent risk factor for OA. Introduction. Biomechanical disturbances and joint inflammation are known risk factors, which may provoke or advance osteoarthritis (OA). However, the effect of interactions of such risk factors on the onset and progression of OA are still poorly understood. Therefore, the goal of this study was to investigate the in vivo effects of muscle weakness, joint inflammation, and the combination of these two risk factors, on the onset and progression of OA in the rabbit knee. Patients & Methods. Thirty 1-year-old skeletally mature female New Zealand White rabbits (weight: average 5.7kg, range 4.8–6.6kg) were used in this study. The animals were divided into four experimental groups: (i) surgical transection of the nerve branch of the common femoral nerve leading to the vastus lateralis muscle; (ii) muscle weakness of the quadriceps muscle induced by a chronic intramuscular injection of Botulinum toxin A (BTX-A) (3); (iii) intraarticular injection in the experimental knee joint with commercially available sterile Carrageenan solution to induce a transient severe inflammatory reaction (4); (iv) administration of both intraarticular injection of Carrageenan and intramuscular injection of BTX-A. In each animal, one hind limb was randomly assigned to the experimental intervention, while the contralateral side acted as its own control. Ninety days following intervention, muscle mass, joint diameter and cartilage histology of the femur, femoral groove, tibia and patella were assessed and microscopically analyzed using the OARSI histology score. Results. Transection of the femoral branch leading to the vastus lateralis as well as the administration of BTX-A led to a significant muscle mass loss for the vastus lateralis and the total quadriceps group, respectively. Similar results were seen in the combined Carrageenan/BTX-A group. There were no changes in total quadriceps muscle mass in the Carrageenan group. Knee joint diameters of the experimental limb were significantly increased in the Carrageenan and Carrageenan/BTX groups. VL transection and BTX-A injection did not cause significant increases in joint diameter. Histologic assessment of the cartilage showed that weakness of the vastus lateralis resulted in significantly higher OARSI scores in the patella and femoral groove, but not the tibiofemoral articulation. The administration of BTX-A caused significant cartilage damage in all 4 compartments (patella, femur, tibia, femoral groove). Intraarticular injection of Carrageenan did not cause significant cartilage damage in any compartment compared to the contralateral side. The combination of BTX-A and Carrageenan resulted in severe cartilage damage in the patella in all four compartments of the knee. The most severe damage was found on the medial side of the tibiofemoral joint and the lateral side of the patellofemoral joint. Conclusion. Severe muscle weakness over a three months period leads to the onset and progression of OA in the rabbit knee. A transient local inflammatory stimulus did not promote cartilage degradation, nor did it enhance cartilage degradation when it was combined with muscle weakness. This result is surprising and adds to the literature the idea that a severe but transient inflammation may not be an independent risk factor for OA

Objectives. The aim of this experimental study on New Zealand’s white rabbits was to investigate the transplantation of autogenous growth plate cells in order to treat the injured growth plate. They were assessed in terms of measurements of radiological tibial varus and histological characteristics. . Methods. An experimental model of plate growth medial partial resection of the tibia in 14 New Zealand white rabbits was created. During this surgical procedure the plate growth cells were collected and cultured. While the second surgery was being performed, the autologous cultured growth plate cells were grafted at the right tibia, whereas the left tibia was used as a control group. . Results. Histological examinations showed that the grafted right tibia presented the regular shape of the plate growth with hypertrophic maturation, chondrocyte columniation and endochondral calcification. Radiological study shows that the mean tibial deformity at the left angle was 20.29° (6.25 to 33) and 7.21° (5 to 10) in the right angle. . Conclusion. This study has demonstrated that grafting of autogenous cultured growth plate cells into a defect of the medial aspect of the proximal tibial physis can prevent bone bridge formation, growth arrest and the development of varus deformity. Cite this article: Bone Joint Res 2014;3:310–16

We investigated the effects of low-intensity pulsed ultrasound on distraction osteogenesis in a rabbit model. Callotasis of the right tibia was performed in 70 male Japanese white rabbits using mini-external fixators. In the first part of the study in 64 animals using normal distraction (waiting period seven days; distraction rate 0.5 mm/12 hours; distraction period ten days), we evaluated the distraction site by radiography, measurement of the bone mineral density (BMD), mechanical testing, and histology. In the second part in six rabbits using fast distraction (waiting period 0 days; distraction rate 1.5 mm/12 hours; distraction period seven days) the site was evaluated radiologically. Half of the animals (35) had received ultrasound to their right leg (30mW/cm. 2. ) for 20 minutes daily after ceasing distraction (ultrasound group), while rigid fixation only was maintained in the other half (control group). With normal distraction, the hard callus area, as shown by radiography, the BMD, and the findings on mechanical testing, were significantly greater in those receiving ultrasound than in the control group. Histological analysis showed no tissue damage attributable to exposure to ultrasound. With fast distraction, immature bone regeneration was observed radiologically in the control group, while bone maturation was achieved in the ultrasound group. We conclude that ultrasound can accelerate bone maturation in distraction osteogenesis in rabbits, even in states of poor callotasis

Introduction. The mechanism for development of corticosteroid-induced osteonecrosis of the femoral head remains to be understood. Elucidation of the mechanism and the establishment of preventive methods have been critical issues. To establish a clinical method for prevention of corticosteroid-induced osteonecrosis, we have examined the suppressive effect of reduced glutathione (GSH) in a corticosteroid-induced rabbit model. Methods. Female Japanese white rabbits were separated into five groups: Group S4, a single intramuscular 4 mg/kg methyl prednisolone acetate (MPSL) administration in the gluteus; Group G4, administration of a 5 mg/kg regular dose GSH for 5 consecutive days starting on the day of a single 4 mg/kg MPSL administration; Group S20, a single intramuscular administration of 20 mg/kg MPSL in the gluteus; Group G20, administrations of 5 mg/kg GSH for 5 consecutive days starting on the day of a single 20 mg/kg MPSL administration; and Group N, control group with no treatment. All rabbits were sacrificed 14 days after MPSL administration. Histopathological analyses were performed by hematoxylin-eosin staining. Immunohistological analyses were performed using anti-lectinlike oxidized LDL reseptor-1 antibody (anti-LOX-1 antibody). Results. Osteonecrosis occurred in 70% of the animals in Group S4, whereas, no osteonecrosis was observed in Group G4, showing a significant suppression. Osteonecrosis was observed in 90% of the animals in Group S20, and it was significantly suppressed in Group G20, with only 30% of the animals affected. The expression of LOX-1 was significantly elevated in Groups S4 and S20. In Group N, no osteonecrosis was observed in all cases, while the expression of LOX-1 was only marginally detected. Conclusion. Abnormal expression of LOX-1 which was examined in the present study is used as an indicator of tissue hyperoxidation. GSH is known to be an enzyme which protect tissues and the vascular endothelium. In the present study, significant suppression of osteonecrosis was observed in Groups G4 and G20 which received GSH administrations, in which osteonecrosis occurred in 0 and 30%, respectively. In addition, LOX-1 expression was also reduced. These results showed that GSH at the regular dose suppressed oxidative stress and development of osteonecrosis, suggesting an effective clinical application of GSH

The feasibility of bone transport with bone substitute and the factors which are essential for a successful bone transport are unknown. We studied six groups of 12 Japanese white rabbits. Groups A to D received cylindrical autologous bone segments and groups E and F hydroxyapatite prostheses. The periosteum was preserved in group A so that its segments had a blood supply, cells, proteins and scaffold. Group B had no blood supply. Group C had proteins and scaffold and group D had only scaffold. Group E received hydroxyapatite loaded with recombinant human bone morphogenetic protein-2 and group F had hydroxyapatite alone. Distraction osteogenesis occurred in groups A to C and E which had osteo-conductive transport segments loaded with osteo-inductive proteins. We conclude that scaffold and proteins are essential for successful bone transport, and that bone substitute can be used to regenerate bone

In 16 mature New Zealand white rabbits mesenchymal stem cells were aspirated from the bone marrow, cultured in monolayer and implanted on to a full-thickness osteochondral defect artificially made on the patellar groove of the same rabbit. A further 13 rabbits served as a control group. The rabbits were killed after 14 weeks. Healing of the defect was investigated histologically using haematoxylin and eosin and Safranin-O staining and with immunohistochemical staining for type-II collagen. We also used a reverse transcription-polymerase chain reaction (RT-PCR) to detect mRNA of type-I and type-II collagen. The semiquantitative histological scores were significantly higher in the experimental group than in the control group (p < 0.05). In the experimental group immunohistochemical staining on newly formed cartilage was more intense for type-II collagen in the matrix and RT-PCR from regenerated cartilage detected mRNA for type-II collagen in mature chondrocytes. These findings suggest that repair of cartilage defects can be enhanced by the implantation of cultured mesenchymal stem cells

We attempted to repair full-thickness defects in the articular cartilage of the trochlear groove of the femur in 30 rabbit knee joints using allogenic cultured chondrocytes embedded in a collagen gel. The repaired tissues were examined at 2, 4, 8, 12 and 24 weeks after operation using histological and histochemical methods. The articular defect filling index measurement was derived from safranin-O stained sections. Apoptotic cellular fractions were derived from analysis of apoptosis in situ using TUNEL staining, and was confirmed using caspase-3 staining along with quantification of the total cellularity. The mean articular defect filling index decreased with time. After 24 weeks it was 0.7 (. sd. 0.10), which was significantly lower than the measurements obtained earlier (p < 0.01). The highest mean percentage of apoptotic cells were observed at 12 weeks, although the total cellularity decreased with time. Because apoptotic cell death may play a role in delamination after chondrocyte transplantation, anti-apoptotic gene therapy may protect transplanted chondrocytes from apoptosis

We studied bone-tendon healing using immunohistochemical methods in a rabbit model. Reconstruction of the anterior cruciate ligament was undertaken using semitendinosus tendon in 20 rabbits. Immunohistochemical evaluations were performed at one, two, four and eight weeks after the operation. The expression of CD31, RAM-11, VEGF, b-FGF, S-100 protein and collagen I, II and III in the bone-tendon interface was very similar to that in the endochondral ossification. Some of the type-III collagen in the outer layer of the graft, which was deposited at a very early phase after the operation, was believed to have matured into Sharpey-like fibres. However, remodelling of the tendon grafted into the bone tunnel was significantly delayed when compared with this ossification process. To promote healing, we believe that it is necessary to accelerate remodelling of the tendon, simultaneously with the augmentation of the ossification

We have investigated in vitro the release kinetics and bioactivity of fibroblast growth factor-2 (FGF-2) released from a carrier of fibrin sealant. In order to evaluate the effects of the FGF-2 delivery mechanism on the repair of articular cartilage, full-thickness cylindrical defects, 5 mm in diameter and 4 mm in depth, which were too large to undergo spontaneous repair, were created in the femoral trochlea of rabbit knees. These defects were then filled with the sealant. Approximately 50% of the FGF-2 was released from the sealant within 24 hours while its original bioactivity was maintained. The implantation of the fibrin sealant incorporating FGF-2 successfully induced healing of the surface with hyaline cartilage and concomitant repair of the subchondral bone at eight weeks after the creation of the defect. Our findings suggest that this delivery method for FGF-2 may be useful for promoting regenerative repair of full-thickness defects of articular cartilage in humans