Defects In Rabbit Knee Research Articles

Use of polyglycolic acid-hyaluronic acid/β-tricalcium phosphate scaffold with or without mesenchymal stem cells found ineffective in treating osteochondral lesions in rabbit knees.

In this experimental animal study, a novel bilayered scaffold used in the treatment of osteochondral defects in rabbit knees was evaluated. This novel scaffold's upper (cartilage) layer consists of polyglycolic acid and hyaluronic acid, and the lower (bone) layer consists of β-tricalcium phosphate. The purpose of this study was to evaluate the efficacy of this novel scaffold, combined with or without mesenchymal stem cells (MSCs), in the treatment of osteochondral defects in rabbit knees. Osteochondral defects were created in the left femoral trochlea of 30 rabbits. In group A, defects were treated with scaffold combined with MSCs; in group B, defects were treated with cell-free scaffolds; and group C was a control group with defects left untreated. In the 12th week, animals were sacrificed for macroscopic evaluation. The mean International Cartilage Repair Society (ICRS) macroscopic scores were 4.95 for group A, 6.16 for group B, and 8.25 for group C. The mean Oswestry Arthroscopic Scores (OAS) were 1.65 for group A, 3.39 for group B, and 6.05 for group C. The macroscopic scores were significantly higher in group C than group A for ICRS scores and group A and group B for OAS (P < .001, P < .000, P < .022). In essence, our findings indicate that the newly developed osteochondral scaffold, when tested in a rabbit model, is not as effective as expected in repairing full-thickness osteochondral defects, with or without the supplementation of MSCs. Further investigation is required to enhance the effectiveness of this novel combination.

Locally delivered modified citrus pectin - a galectin-3 inhibitor shows expected anti-inflammatory and unexpected regeneration-promoting effects on repair of articular cartilage defect

Treating the concomitant inflammation in the process of injury and repair, and simultaneously promoting cartilage regeneration is very important for the repair of articular cartilage (AC) defects. Nevertheless, this remains a massive challenge. To address this issue, a collagen membrane-based modified citrus pectin (MCP) delivery system (MCP-C) was developed in this study by targeting galectin-3 (Gal-3), an upstream proinflammatory factor. As expected, MCP shows anti-inflammatory effects; it downregulates the expressions of IL-1β, MMP13, Gal-3, and COL1A2, inhibits the degenerative effects of Gal-3 on chondrocytes in vitro, and protects chondrocytes from degeneration and death in vivo. Unexpectedly, MCP promotes the proliferation of chondrocytes, upregulates the expression of COL2A1 and SOX9 in the chondrocytes in vitro, and enhances the repair of AC defect in rabbit knee, especially MCP500-C with a complete release of the loading amount of approximately 500 μg/cm2 in a day. Mechanistically, MCP upregulates the expressions of multiple endogenous growth factors for chondrogenesis via the transcriptome sequencing of MCP-treated chondrocytes, and downregulates the expressions of various inflammatory factors. These findings demonstrate that locally delivered MCP can simultaneously modulate both regenerative and inflammatory responses, and can enhance the repair of AC defects.

Naringin and bone marrow mesenchymal stem cells repair articular cartilage defects in rabbit knees through the transforming growth factor-β superfamily signaling pathway.

The present study aimed to assess the effect of a combination of naringin and rabbit bone marrow mesenchymal stem cells (BMSCs) on the repair of cartilage defects in rabbit knee joints and to assess possible involvement of the transforming growth factor-β (TGF-β) signaling pathway in this process. After establishing an articular cartilage defect model in rabbit knees, 20 New Zealand rabbits were divided into a sham operation group (Sham), a model group (Mod), a naringin treatment group (Nar), a BMSC group (BMSCs) and a naringin + BMSC group (Nar/BMSCs). At 12 weeks after treatment, the cartilage was evaluated using the International Cartilage Repair Society (ICRS)'s macroscopic evaluation of cartilage repair scale, the ICRS's visual histological assessment scale, the Modified O'Driscoll grading system, histological staining (hematoxylin and eosin staining, toluidine blue staining and safranin O staining) and immunohistochemical staining (type-II collagen, TGF-β3 and SOX-9 immunostaining). Using the above grading systems to quantify the extent of repair, histological quantification and macro quantification of joint tissue repair showed that the Nar/BMSCs group displayed repair after treatment in comparison to the untreated Mod group. Among the injury model groups (Mod, Nar, BMSCs and Nar/BMSCs), the Nar/BMSCs group displayed the highest degree of morphological repair. The results of histological and immunohistochemical staining of the repaired region of the joint defect indicated that the BMSCs had a satisfactory effect on the repair of the joint structure but had a poor effect on the repair of cartilage quality. The Nar/BMSCs group displayed satisfactory therapeutic effects on both repair of the joint structure and cartilage quality. The expression level of type-II collagen was high in the Nar/BMSCs group. Additionally, staining of TGF-β3 and SOX-9 in the Nar/BMSCs group was the strongest compared with that of any other group in the present study. Naringin and/BMSCs together demonstrated a more efficient repair effect on articular cartilage defects in rabbit knees than the use of either treatment alone in terms of joint structure and cartilage quality. One potential mechanism of naringin action may be through activation and continuous regulation of the TGF-β superfamily signaling pathway, which can promote BMSCs to differentiate into chondrocytes.

Effect of boric acid on cartilage formation of osteochondral defects in rabbit knee: An experimental study.

The present study aimed to investigate the healing of articular cartilage with boric acid (BA) injection in an experimental cartilage defect model of rabbit knee. Nine skeletally mature female New Zealand White rabbits were used. The right knees of the rabbits were assigned as the study group and injected with the BA solution and the left knees of the rabbits as the control group. Under anesthesia, a cylindrical full-thickness osteochondral defect (4 mm in diameter and 3 mm in depth) was formed using a drill on the anterior side of the articular surface of the medial femur condyle. The BA solution was administered to the right knees of rabbits in the form of an intra-articular injection (8 mg/kg) for 6 weeks, at the same day and hours each week. The animals were euthanized at the end of the 2nd month. In both macroscopic evaluation and microscopic evaluation, statistically significant differences were observed in the BA injection group compared with the control group (p<0.05). In the macroscopic examination of the defect area, statistically significant differences were observed between the groups in terms of degree of defect repair, integration to border zone, and macroscopic appearance (p<0.05). The averaged results of all evaluated parameters of the International Cartilage Repair Society visual histological assessment score were better for the BA group. The healing process of the cartilage injury could be improved by BA injection administration. In future, BA may safely be used as an additional treatment modality in clinical practice to enhance the healing process of cartilage injuries, which are commonly observed orthopedic problem.

Role of the Calcified Cartilage Layer of an Integrated Trilayered Silk Fibroin Scaffold Used to Regenerate Osteochondral Defects in Rabbit Knees.

The repair of osteochondral defects remains challenging, given the complexity of native osteochondral tissue and the limited self-repair capacity of cartilage. Osteochondral tissue engineering is a promising strategy. Here, we fabricated a biomimetic osteochondral scaffold using silk fibroin and hydroxyapatite, including a calcified cartilage layer (CCL). We studied the role played by the CCL in terms of cell viability in vivo. We established osteochondral defects in rabbit knees to investigate the effects of CCL-containing scaffolds with or without adipose tissue-derived stem cells (ADSCs). We evaluated osteochondral tissue regeneration by calculating gross observational scores, via histological and immunohistochemical assessments, by performing quantitative biochemical and biomechanical analyses of new osteochondral tissue, and via microcomputed tomography of new bone at 4, 8, and 12 weeks after surgery. In terms of surface roughness and integrity, the CCL + ADSCs group was better than the CCL and the non-CCL + ADSCs groups at all time points tested; the glycosaminoglycan and collagen type II levels of the CCL + ADSCs group were highest, reflecting the important role played by the CCL in cartilage tissue repair. Subchondral bone smoothness was better in the CCL + ADSCs group than in the non-CCL + ADSCs and CCL groups. The CCL promoted smooth subchondral bone regeneration but did not obviously affect bone strength or quality. In conclusion, a biomimetic osteochondral scaffold with a CCL, combined with autologous ADSCs, satisfactorily regenerated a rabbit osteochondral defect. The CCL enhances cartilage and subchondral bone regeneration.

Chondrocyte Co-cultures with the Stromal Vascular Fraction of Adipose Tissue in Polyhydroxybutyrate/Poly-(hydroxybutyrate-co-hydroxyhexanoate) Scaffolds: Evaluation of Cartilage Repair in Rabbit

Chondral defects are challenging to repair because of the poor self-healing capacity of articular cartilage. The aim of this study was to compare and investigate the cartilage regeneration of stromal vascular fraction (SVF) cells and adipose-derived stem cells (ASCs) co-cultured with chondrocytes seeding on scaffolds composed of polyhydroxybutyrate (PHB)/poly-(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx). In this study, the cellular morphologies and proliferation capabilities on scaffolds were evaluated. Next, scaffolds with 1:1 co-culture of ASCs/SVF and chondrocytes were implanted into the full-thickness cartilage defects in rabbit knee for 10 weeks. Cells seeded on the scaffolds showed better adhesion, migration, and proliferation in vitro. Importantly, implantation with scaffolds with SVF and chondrocytes revealed more desirable in vivo healing outcomes. Our results illustrate a one-step surgical procedure for the regeneration of focal cartilage defects using a mixture of SVF from adipose tissue and uncultured chondrocytes.

Icariin-conditioned serum engineered with hyaluronic acid promote repair of articular cartilage defects in rabbit knees

BackgroundOsteochondral defects mostly occur as a result of trauma or articular degeneration. The poor regenerative ability of articular cartilage remains osteochondral defects are a tricky problem to deal with. The modern treatment strategies mainly focus on cartilage tissue engineering with bioactive materials. In this study, we aimed to develop icariin conditioned serum (ICS) together with hyaluronic acid (HA) and determine their ability in reparing osteochondral tissue in a critical-sized defect in rabbit knees.MethodsPrimary chondrocytes were incubated with serum conditioned with icariin at different concentrations, then cell proliferation rates and glycosaminoglycan (GAG) secretion were detected. Rabbits were treated with intra-articular injection of 0.5 mL normal saline (NS), ICS, HA and ICS + HA in the right knee joint, respectively. ICRS scores were used to assess the macroscopic cartilage regeneration. Histological and immunohistochemical analysis including H&E, Safranin O, toluidine blue and collagen II staining were used to determine the repair of cartilage and the regeneration of chondrocytes.ResultsIcariin at a low dose of 0.94 g/kg was identified to have significantly promoted the proliferation of chondrocytes and enhance the secretion of GAG. Femoral condyle from rabbits treated by ICS together with HA was observed to be integrated with native cartilage and more subchondral bone regeneration. ICS together with HA could promote repair of the cartilage defect and increase the neoformation of cartilage.ConclusionsThese results demonstrated the potential of ICS combined with HA to promote reparative response in cartilage defects and the possible application in bioactive material based cartilage regeneration therapies.

Repair of Osteochondral Defects in Rabbit Knee Using Menstrual Blood Stem Cells Encapsulated in Fibrin Glue: A Good Stem Cell Candidate for the Treatment of Osteochondral Defects.

In recent years, researchers discovered that menstrual blood-derived stem cells (MenSCs) have the potential to differentiate into a wide range of tissues including the chondrogenic lineage. In this study, we aimed to investigate the effect of MenSCs encapsulated in fibrin glue (FG) on healing of osteochondral defect in rabbit model. We examined the effectiveness of MenSCs encapsulated in FG in comparison with FG alone in the repair of osteochondral defect (OCD) lesions of rabbit knees after 12 and 24weeks. Macroscopical evaluation revealed that the effectiveness of MenSCs incorporation with FG is much higher than FG alone in repair of OCD defects. Indeed, histopathological evaluation of FG + MenSCs group at 12weeks post-transplantation demonstrated that defects were filled with hyaline cartilage-like tissue with proper integration, high content of glycosaminoglycan and the existence of collagen fibers especially collagen type II, as well as by passing time (24weeks post-transplantation), the most regenerated tissue in FG + MenSCs group was similar to hyaline cartilage with relatively good infill and integration. As the same with the result of 12weeks post-implantation, the total point of microscopical examination in FG + MenSCs group was higher than other experimental groups, however, no significant difference was detected between groups at 24weeks (p>0.05). In summary, MenSCs as unique stem cell population, is suitable for in vivo repair of OCD defects and promising for the future clinical application.

Similar regeneration of articular cartilage defects with autologous & allogenic chondrocytes in a rabbit model.

Background & objectives:Articular cartilage defects in the knee have a very poor capacity for repair due to avascularity. Autologous chondrocyte transplantation (ACT) is an established treatment for articular cartilage defects. Animal studies have shown promising results with allogenic chondrocyte transplantation since articular cartilage is non-immunogenic. In addition to being economical, allogenic transplantation has less morbidity compared to ACT. This study was undertaken to compare ACT with allogenic chondrocyte transplantation in the treatment of experimentally created articular cartilage defects in rabbit knee joints.Methods:Cartilage was harvested from the left knee joints of six New Zealand white rabbits (R1-R6). The harvested chondrocytes were cultured to confluence and transplanted onto a 3.5 mm chondral defect in the right knees of 12 rabbits [autologous in 6 rabbits (R1-R6) and allogenic in 6 rabbits (R7-R12)]. After 12 wk, the rabbits were euthanized and histological evaluation of the right knee joints were done with hematoxylin and eosin and safranin O staining. Quality of the repair tissue was assessed by the modified Wakitani histological grading scale.Results:Both autologous and allogenic chondrocyte transplantation resulted in the regeneration of hyaline/mixed hyaline cartilage. The total histological scores between the two groups showed no significant difference.Interpretation & conclusions:Allogenic chondrocyte transplantation seems to be as effective as ACT in cartilage regeneration, with the added advantages of increased cell availability and reduced morbidity of a single surgery.

Osteochondral tissue engineering based on biomimetic osteochondral scaffold contained calcified cartilage layer com-pounding with ADSCs in vivo

Objective The biomimetic osteochondral scaffold contained calcified cartilage layer(CCL) was fabricated us-ing slik fibroin (SF) and hydroxyapatite (HA) for materials. To investigate effects of biomimetic osteochondral scaffold contained CCL compounding with ADSCs on regeneration of the osteochondral defect on the rabbit knee, explore the feasibility of this design as a concept of osteochondral tissue engineering. Methods We fabricated a novel biomimetic osteochondral scaffold with CCL using SF and HA by the combination of paraffin-sphere leaching and modified temperature gradient-guided thermal-induced phase separation (TIPS) technique. The pore size, porosity, and compressive modulus of elasticity of the scaffold cartilage layer and the osteogenic layer were measured by scanning electron microscopy and microscopy CT. The osteochondral defect model on rabbit bi-lateral knees were established, and implanted with the non-CCL group (non-CCL scaffold compounding with ADSCs) and CCL group (CCL scaffold compounding with ADSCs). At 4, 8 and 12 weeks after implantation, the rabbits were euthanized, respectively.Gross observation score, histological and immunohistochemical assessment, biochemical quantitative of new osteochondral tissue, micro-CT scans for new bone, were executed. We evaluated the regeneration of osteochondral defects in each group, and verified the role of CCL in vivo. Results The biomimetic osteochondral scaffold with CCL had a consecutively overlapping trilayer struc-ture with different densities and pore structures, including a chondral layer (top layer), intermediate layer and bony layer (bottom layer). The cartilage layer had a well-oriented microporous structure with a uniform distribution with a pore size of (112.43±12.65) μm and a porosity of 90.25%±2.05%. The subchondral bone layer had a good three-dimensional macroporous structure, good con-nectivity, pore size (362.23±26.52) μm, porosity of osteogenic layer was 85.30%±1.80%. The cartilage regeneration in CCL+AD-SCs group was better than non-CCL+ADSCs group. The content of GAG and type II collagen in new cartilage tissue in CCL+AD-SCs group was much more than non-CCL+ADSCs group. The new bone tissue analysis and biomechanical testing had no signifi-cant differences between the two groups. Conclusion The biomimetic osteochondral SF/HA scaffold contained CCL mimics the structure of normal osteochondral tissue with good 3-dimensional pore structure and biocompatibility. The scaffold complex autolo-gous ADSCs successfully repair osteochondral defects in rabbit knee, and the presence of CCL accelerates the growth of cartilage. Key words: Tissue engineering; Cartilage; Tissue scaffolds; Slik; Hydroxyapatites

Repair of articular cartilage and subchondral defects in rabbit knee joints with a polyvinyl alcohol/nano-hydroxyapatite/polyamide 66 biological composite material

BackgroundThis study sought to prepare a new PVA/n-HA/PA66 composite to investigate the repair of articular cartilage and subchondral defects in rabbit knee joints.MethodsA 5 × 5 × 5 mm-sized defect was created in the patellofemoral joints of 72 healthy adult New Zealand rabbits. The rabbits were then randomly divided into three groups (n = 24): PVA/n-HA+PA66 group, polyvinyl alcohol (PVA) group, and control (untreated) group. Cylindrical PVA/n-HA+PA66, 5 × 5 mm, comprised an upper PVA layer and a lower n-HA+PA66 layer. Macroscopic and histological evaluations were performed at 4, 8, 12, and 24 weeks, postoperatively. Type II collagen was measured by immunohistochemical staining. The implant/cartilage and bone interfaces were observed by scanning electron microscopy.ResultsAt 24 weeks postoperatively, the lower PVA/n-HA+PA66 layer became surrounded by cartilage, with no obvious degeneration. In the PVA group, an enlarged space was observed between the implant and the host tissue that had undergone degeneration. In the control group, the articular cartilage had become calcified. In the PVA/n-HA+PA66 group, positive type II collagen staining was observed between the composite and the surrounding cartilage and on the implant surface. In the PVA group, positive staining was slightly increased between the PVA and the surrounding cartilage, but reduced on the PVA surface. In the control group, reduced staining was observed throughout. Scanning electron microscopy showed increased bone tissue in the lower n-HA+PA66 layer that was in close approximation with the upper PVA layer of the composite. In the PVA group, the bone tissue around the material had receded, and in the control group, the defect was filled with bone tissue, while the superior aspect of the defect was filled with disordered, fibrous tissue.ConclusionThe diphase biological composite material PVA/n-HA+PA66 exhibits good histocompatibility and offers a satisfactory substitute for articular cartilage and subchondral bone.

Matrigel scaffold combined with Ad-hBMP7-transfected chondrocytes improves the repair of rabbit cartilage defect.

The aim of this study was to explore an effective method for the repair of cartilage defects using chitosan/glycerophosphate (C/GP) gel- and Matrigel-engineered human bone morphogenetic protein 7 (hBMP7)-expressing chondrocytes. Rabbit chondrocytes were obtained, cultured in vitro and transfected with an adenovirus containing hBMP7 and green fluorescent protein (Ad-hBMP7-GFP). The expression of hBMP7 in the transfected cells was tested by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The phenotype of the transfected cells was evaluated by detecting the yields of collagen II and hyaluronic acid using RT-PCR and enzyme-linked immunosorbent assay (ELISA). The growth of chondrocytes in the C/GP gel and Matrigel was accessed by measuring the cell growth rate, hematoxylin and eosin (H&E) staining and observation under a scanning microscope. Twelve adult male New Zealand white rabbits were randomly divided into three groups. Two cartilage defects were created in the rabbits' knees by aseptic surgery. Group A (n=4) did not receive any treatment, group B (n=4) were treated with C/GP gel and Matrigel-engineered Ad-mock-GFP-transfected chondrocytes, and group C (n=4) were treated with C/GP gel and Matrigel-engineered Ad-hBMP7-GFP-transfected chondrocytes. Rabbits were sacrificed at 4 weeks after transplantation, and the repair effect was measured by the Wakitani scoring method. On the basis of the RT-PCR and western blot results, hBMP7 was efficiently overexpressed in the Ad-hBMP7-GFP-transfected chondrocytes. The ELISA results showed that the yields of collagen II and hyaluronic acid in Ad-hBMP7-GFP-transfected chondrocytes were significantly higher than those in Ad-mock-GFP-transfected chondrocytes. Chondrocytes have a better morphology and arrangement in a Matrigel scaffold than in C/GP, as assessed by H&E staining and scanning microscopy. According to the Wakitani score, Matrigel combined with Ad-hBMP7-GFP-transfected chondrocytes successfully promoted the repair of cartilage defects in rabbit knees.

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Based Electrospun 3D Scaffolds for Delivery of Autogeneic Chondrocytes and Adipose-Derived Stem Cells: Evaluation of Cartilage Defects in Rabbit.

The management of chondral defects has long been a challenge because of the poor self-healing capacity of articular cartilage. Many approaches ranging from symptomatic treatment to structural cartilage regeneration have obtained very limited satisfactory results. Cartilage tissue engineering, which involves an optimized combination of novel scaffolds, cell sources and growth factors, has emerged as a promising strategy for cartilage regeneration and repair. In this study, the cellular morphologies and the adhesion, migration and proliferation capabilities of adipose-derived stem cells (ASCs) and chondrocytes seeded on 3D scaffolds composed of electrospun poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) were evaluated. Next, TGF-β1/scaffolds with 4:1 co-culture of ASCs and chondrocytes were implanted into the full thickness cartilage defects in rabbit knee for 16 weeks. ASCs and chondrocytes seeded on the scaffolds showed better adhesion, migration and proliferation than that on petri dishes in vitro. Importantly, implantation with TGF-β1/scaffolds with delivery of ASCs and chondrocytes revealed desirable in vivo healing outcomes. These results demonstrate that ASCs have great potential in the field of tissue engineering. It is possible that the improvement in ASC-seeded electrospun 3D P3HB4HB scaffolds may ultimately lead to improved repair of cartilage injuries.

Long-Term Results of Cartilage Repair after Allogeneic Transplantation of Cartilaginous Aggregates Formed from Bone Marrow-Derived Cells for Large Osteochondral Defects in Rabbit Knees.

Objective: The purpose of this study was to evaluate the long-term results of cartilage repair after allogeneic transplantation of cartilaginous aggregates formed from bone marrow–derived cells. Methods: Bone marrow cells were harvested from 12-day-old rabbits. The cells were subjected to a monolayer culture, and the spindle-shaped cells attached to the flask surface were defined as bone marrow–derived mesenchymal cells. After the monolayer culture, a 3-dimensional cartilaginous aggregate was formed using a bioreactor with chondrogenesis. We created osteochondral defects, measuring 5 mm in diameter and 4 mm in depth, at the femoral trochlea of 10-week-old rabbits. Two groups were established, the transplanted group in which the cartilaginous aggregate was transplanted into the defect, and the control group in which the defect was left untreated. Twenty-six and 52 weeks after surgery, the rabbits were sacrificed and their tissue repair status was evaluated macroscopically (International Cartilage Repair Society [ICRS] score) and histologically (O’Driscoll score). Results: The ICRS scores were as follows: at week 26, 7.2 ± 0.5 and 7.6 ± 0.8; at week 52, 7.6 ± 1.1 and 9.7 ± 0.7, for the transplanted and control groups, respectively. O’Driscoll scores were as follows: at week 26, 12.6 ± 1.9 and 10.1 ± 1.9; at week 52, 9.6 ± 3.0 and 14.0 ± 1.4, each for transplanted and control groups, respectively. No significant differences were observed between the groups. Conclusions: This study demonstrates that allogeneic transplantation of cartilaginous aggregates formed from bone marrow–derived cells produces comparable long-term results based on macroscopic and histological outcome measures when compared with osteochondral defects that are left untreated.

Potential of exogenous cartilage proteoglycan as a new material for cartilage regeneration

Although proteoglycan (PG) is one of the major components of cartilage matrices, its biological function is not fully elucidated. The objectives of this study were to investigate the proliferation and differentiation of chondrocytes embedded in atelocollagen gel with exogenous cartilage PG (PG-atelocollagen gel) in vitro, and also to evaluate the repair of cartilage defects by PG-atelocollagen gel in vivo. In the in vitro study, rabbit chondrocytes were cultured in the PG-atelocollagen gel. Cell proliferation and mRNA expression levels were measured, and gels were histologically evaluated. In the in vivo study, cultured PG-atelocollagen gel containing chondrocytes were transplanted into full-thickness articular cartilage defects in rabbit knees, and evaluated macroscopically and histologically. For the in vitro study, chondrocyte proliferation in 5.0 mg/ml PG-atelocollagen gel was enhanced, and the gene expression of Col2a1 and Aggrecan were decreased. In contrast, chondrocyte proliferation in 0.1 and 1.0 mg/ml PG-atelocollagen gel was not enhanced. The gene expression of Aggrecan in 0.1 and 1.0 mg/ml PG-atelocollagen gel was increased. For the in vivo study, the histological average total score of the 0.1 mg/ml PG-atelocollagen gel was significantly better than that of the group without PG. Although the appropriate concentration of PG has not been defined, this study suggests the efficacy of PG for cartilage repair.

Continuous Gradients of Material Composition and Growth Factors for Effective Regeneration of the Osteochondral Interface

Most contemporary biomaterial designs for osteochondral regeneration utilize monolithic, biphasic, or even multiphasic constructs. We have introduced a microsphere-based approach to create a continuous gradient in both material composition and encapsulated growth factors. The gradients were fabricated by filling a cylindrical mold with opposing gradients of two different types of poly(D,L-lactic-co-glycolic acid) microspheres. The chondrogenic microspheres were loaded with transforming growth factor-β1, whereas the osteogenic microspheres contained bone morphogenetic protein-2 with or without nanophase hydroxyapatite. The gradient scaffolds (material gradient only, signal gradient only, or material/signal gradient combination) or blank control scaffolds were implanted in 3.5 mm-diameter defects in rabbit knees for 6 or 12 weeks. This is the first in vivo evaluation of these novel gradient scaffolds in the knee. The gross morphology, MRI, and histology indicated that the greatest extent of regeneration was achieved when both signal and material gradients were included together. This combination resulted in complete bone ingrowth, with an overlying cartilage layer with high glycosaminoglycan content, appropriate thickness, and integration with the surrounding cartilage and underlying bone. The results suggest that osteochondral regeneration may benefit from biomaterials that integrate a continuous gradient in both material composition and encapsulated growth factors.

A Comparison Study of Periosteal and Perichondrial Autografts for Full Thickness Articular Cartilage Defects in Rabbit Knees

A Comparison Study of Periosteal and Perichondrial Autografts for Full Thickness Articular Cartilage Defects in Rabbit Knees

A cellular implantation system using an injectable ultra‐purified alginate gel for repair of osteochondral defects in a rabbit model

We developed a novel cellular implantation system using an in situ forming ultra-purified alginate gel with quite low endotoxity. The aims of this study were to determine the superiority of chondrogenic potential of bone marrow stromal cells (BMSCs) cultured in the purified alginate gel compared with a commercial grade gel, and to assess reparative tissues treated with BMSCs implanted using the developed system into cartilage defects in rabbit knees. The effects of each alginate gel on cellular proliferation and chondrogenesis of rabbit BMSCs were determined by in vitro assessments. Using our purified alginate gel, a novel vehicle system for injecting BMSCs into osteochondral defects without periosteal patch was successfully established in this animal models. The in vitro analyses demonstrated that the purification of alginate significantly enhanced the cellular proliferation and chondrogenic differentiation of BMSCs. The in vivo assessments suggested that the implantation of BMSCs with the developed system using the purified alginate gel histologically and mechanically improved the reparative tissue of osteochondral defects. This system using the purified alginate gel shows the clinical potential for arthroscopically injectable implantation of BMSCs for the treatment of cartilaginous lesions.

In vivo outcomes of tissue‐engineered osteochondral grafts

Tissue-engineered osteochondral grafts have been synthesized from a variety of materials, with some success at repairing chondral defects in animal models. We hypothesized that in tissue-engineered osteochondral grafts synthesized by bonding mesenchymal stem cell-loaded hydrogels to a porous material, the choice of the porous scaffold would affect graft healing to host bone, and the quality of cell restoration at the hyaline cartilage surface. Bone marrow-derived allogeneic mesenchymal stem cells were suspended in hydrogels that were attached to cylinders of porous tantalum metal, allograft bone, or a bioactive glass. The tissue-engineered osteochondral grafts, thus created were implanted into experimental defects in rabbit knees. Subchondral bone restoration, defect fill, bone ingrowth-implant integration, and articular tissue quality were compared between the three subchondral materials at 6 and 12 weeks. Bioactive glass and porous tantalum were superior to bone allograft in integrating to adjacent host bone, regenerating hyaline-like tissue at the graft surface, and expressing type II collagen in the articular cartilage.

Blocking of tumor necrosis factor activity promotes natural repair of osteochondral defects in rabbit knee

Background and purpose Osteochondral defects have a limited capacity for repair. We therefore investigated the effects of tumor necrosis factor (TNF) signal blockade by etanercept (human recombinant soluble TNF receptor) on the repair of osteochondral defects in rabbit knees.Material and methods Osteochondral defects (5 mm in diameter) were created in the femoral patellar groove in rabbits. Soon after the procedure, a first subcutaneous injection of etanercept was performed. This single injection or, alternatively, 4 injections in total (twice a week for 2 weeks) were given. Each of these 2 groups was divided further into 3 subgroups: a low-dose group (0.05 μg/kg), an intermediate-dose group (0.4 μ g/kg), and a high-dose group (1.6 μ g /kg) with 19 rabbits in each. As a control, 19 rabbits were injected with water alone. The rabbits in each subgroup were killed 4 weeks (6 rabbits), 8 weeks (6 rabbits), or 24 weeks (7 rabbits) after surgery and repair was assessed histologically.Results Histological examination revealed that the natural process of repair of the osteochondral defects was promoted by 4 subcutaneous injections of intermediate-dose etanercept and by 1 or 4 injections of high-dose etanercept at the various time points examined postoperatively (4, 8, and 24 weeks). Western blot showed that rabbit TNFα had a high affinity for etanercept.Interpretation Blocking of TNF by etanercept enabled repair of osteochondral defects in rabbit knee. Anti-TNF therapy could be a strategy for the use of tissue engineering for bone and cartilage repair.