Aims. The purpose of this study was to explore a simple and effective method of preparing human acellular amniotic membrane (HAAM) scaffolds, and explore the effect of HAAM scaffolds with juvenile cartilage fragments (JCFs) on osteochondral defects. Methods. HAAM scaffolds were constructed via trypsinization from fresh human amniotic membrane (HAM). The characteristics of the HAAM scaffolds were evaluated by haematoxylin and eosin (H&E) staining, picrosirius red staining, type II collagen immunostaining, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Human amniotic mesenchymal stem cells (hAMSCs) were isolated, and stemness was verified by multilineage differentiation. Then, third-generation (P3) hAMSCs were seeded on the HAAM scaffolds, and phalloidin staining and SEM were used to detect the growth of hAMSCs on the HAAM scaffolds. Osteochondral defects (diameter: 3.5 mm; depth: 3 mm) were created in the right patellar grooves of 20 New Zealand White rabbits. The rabbits were randomly divided into four groups: the control group (n = 5), the HAAM scaffolds group (n = 5), the JCFs group (n = 5), and the HAAM + JCFs group (n = 5). Macroscopic and histological assessments of the regenerated tissue were evaluated to validate the treatment results at 12 weeks. Results. In vitro, the HAAM scaffolds had a network structure and possessed abundant collagen. The HAAM scaffolds had good cytocompatibility, and hAMSCs grew well on the HAAM scaffolds. In vivo, the macroscopic scores of the HAAM + JCFs group were significantly higher than those of the other groups. In addition, histological assessments demonstrated that large amounts of hyaline-like cartilage formed in the osteochondral defects in the HAAM + JCFs group. Integration with surrounding normal cartilage and regeneration of subchondral bone in the HAAM + JCFs group were better than those in the other groups. Conclusion. HAAM scaffolds combined with JCFs promote the regenerative repair of osteochondral defects. Cite this article: Bone Joint Res 2022;11(6):349–361

Objectives. We sought to determine if a durable bilayer implant composed of trabecular metal with autologous periosteum on top would be suitable to reconstitute large osteochondral defects. This design would allow for secure implant fixation, subsequent integration and remodeling. Materials and Methods. Adult sheep were randomly assigned to one of three groups (n = 8/group): 1. trabecular metal/periosteal graft (TMPG), 2. trabecular metal (TM), 3. empty defect (ED). Cartilage and bone healing were assessed macroscopically, biochemically (type II collagen, sulfated glycosaminoglycan (sGAG) and double-stranded DNA (dsDNA) content) and histologically. Results. At 16 weeks post-operatively, histological scores amongst treatment groups were not statistically different (TMPG: overall 12.7, cartilage 8.6, bone 4.1; TM: overall 14.2, cartilage 9.5, bone 4.9; ED: overall 13.6, cartilage 9.1, bone 4.5). Metal scaffolds were incorporated into the surrounding bone, both in TM and TMPG. The sGAG yield was lower in the neo-cartilage regions compared with the articular cartilage (AC) controls (TMPG 20.8/AC 39.5, TM 25.6/AC 33.3, ED 32.2/AC 40.2 µg sGAG/1 mg respectively), with statistical significance being achieved for the TMPG group (p < 0.05). Hypercellularity of the neo-cartilage was found in TM and ED, as the dsDNA content was significantly higher (p < 0.05) compared with contralateral AC controls (TM 126.7/AC 71.1, ED 99.3/AC 62.8 ng dsDNA/1 mg). The highest type II collagen content was found in neo-cartilage after TM compared with TMPG and ED (TM 60%/TMPG 40%/ED 39%). Inter-treatment differences were not significant. Conclusions. TM is a highly suitable material for the reconstitution of osseous defects. TM enables excellent bony ingrowth and fast integration. However, combined with autologous periosteum, such a biocomposite failed to promote satisfactory neo-cartilage formation. Cite this article: E. H. Mrosek, H-W. Chung, J. S. Fitzsimmons, S. W. O’Driscoll, G. G. Reinholz, J. C. Schagemann. Porous tantalum biocomposites for osteochondral defect repair: A follow-up study in a sheep model. Bone Joint J 2016;5:403–411. DOI: 10.1302/2046-3758.59.BJR-2016-0070.R1

Introduction and Objective. Several in vitro studies have shed light on the osteogenic and chondrogenic potential of graphene and its derivatives. Now it is possible to combine the different biomaterial properties of graphene and 3D printing scaffolds produced by tissue engineering for cartilage repair. Owing to the limited repair capacity of articular cartilage and bone, it is essential to develop tissue-engineered scaffolds for patients suffering from joint disease and trauma. However, chondral lesions cannot be considered independently of the underlying bone tissue. Both the microcirculation and the mechanical support provided with bone tissue must be repaired. One of the distinctive features that distinguish graphene from other nanomaterials is that it can have an inductive effect on both bone and cartilage tissue. In this study, the effect of different concentrations of graphene on the in vivo performance of single-layer poly-ε-caprolactone based-scaffolds is examined. Our hypothesis is that graphene nanoplatelet- containing, robocast PCL scaffolds can be an effective treatment option for large osteochondral defect treatment. For this purpose, different proportions of graphene- containing (1%,3%,5%,10 wt%) PCL scaffolds were studied in a 5mm diameter osteochondral defect model created in the rabbit knee. Materials and Methods. In the study graphene-containing (1, 3, 5, 10 wt%), porous and oriented poly-ε-caprolactone-based scaffolds were prepared by robocasting method to use in the regeneration of large osteochondral defects. Methods: The scaffolds were implanted into the full-thickness osteochondral defect in a rabbit model to evaluate the regeneration of defect in vivo. For this purpose, twenty female New Zealand white rabbits were used and they were euthanized at 4 and 8 weeks of implantation. The reparative osteochondral tissues were harvested from rabbit distal femurs and then processed for gross appearance assessment, radiographic imaging, histopathological and immunohistochemical examinations. Results. Results revealed that, graphene- containing graft materials caused significant amelioration at the defect areas. Graphene-containing graft materials improved the fibrous, chondroid and osseous tissue regeneration compared to the control group. The expressions of bone morphogenetic protein-2 (BMP-2), collagen-1 (col-1), vascular endothelial growth factor (VEGF) and alkaline phosphatase (ALP) expressions were more prominent in graphene- containing PCL implanted groups. Results also revealed that the ameliorative effect of graphene increased by the elevation in concentration. The most prominent healing was observed in 10 wt% graphene-containing PCL based composite scaffold implanted group. Conclusions. This study demonstrated that graphene- containing, robocast PCL scaffolds has efficacy in the treatment of large osteochondral defect. Subchondral new bone formation and chondrogenesis were observed based on immunohistochemical examinations. 3D printed PCL platforms have great potential for the investigation of the osteochondral regeneration mechanism. The efficacy of graphene-containing PCL scaffolds on osteogenesis, vascularization, and mineralization was shown at different graphene concentrations at 4th and 8th weeks. Immunohistochemical studies showed statistical significance in the 5wt% and 10 wt% graphene-containing groups compared to the 1wt% and 3 wt% graphene-containing groups at the end of the eighth week

As arthroplasty demand grows worldwide, the need for a novel cost-effective treatment option for articular cartilage (AC) defects tailored to individual patients has never been greater. 3D bioprinting can deposit patient cells and other biomaterials in user-defined patterns to build tissue constructs from the “bottom-up,” potentially offering a new treatment for AC defects. The aim of this research was to create bioinks that can be injected or 3D bioprinted to aid osteochondral defect repair using human cells. Novel composite bioinks were created by mixing different ratios of methacrylated alginate (AlgMA) with methacrylated gelatin (GelMA). Chondrocytes or mesenchymal stem cells (MSCs) were then encapsulated in the bioinks and 3D bioprinted using a custom-built extrusion bioprinter. UV and double-ionic (BaCl2 and CaCl2) crosslinking was deployed following bioprinting to strengthen bioink stability in culture. Chondrocyte and MSC spheroids were also produced via 3D culture and then bioprinted to accelerate cell growth and development of ECM in bioprinted constructs. Excellent viability of chondrocytes and MSCs was seen following bioprinting (>95%) and maintained in culture over 28 days, with accelerated cell growth seen with inclusion of MSC or chondrocyte spheroids in bioinks (p<0.05). Bioprinted 10mm diameter constructs maintained shape in culture over 28 days, whilst construct degradation rates and mechanical properties were improved with addition of AlgMA (p<0.05). Composite bioinks were also injected into in vitro osteochondral defects (OCDs) and crosslinked in situ, with maintained cell viability and repair of osteochondral defects seen over a 14-day period. In conclusion we developed novel composite AlgMA/GelMA bioinks that can be triple-crosslinked, facilitating dense chondrocyte and MSC growth in constructs following 3D bioprinting. The bioink can be injected or 3D bioprinted to successfully repair in vitro OCDs, offering hope for a new approach to treating AC defects

As arthroplasty demand grows worldwide, the need for a novel cost-effective treatment option for articular cartilage (AC) defects tailored to individual patients has never been greater. 3D bioprinting can deposit patient cells and other biomaterials in user-defined patterns to build tissue constructs from the “bottom-up,” potentially offering a new treatment for AC defects. The aim of this research was to create bioinks that can be injected or 3D bioprinted to aid osteochondral defect repair using human cells. Novel composite bioinks were created by mixing different ratios of methacrylated alginate (AlgMA) with methacrylated gelatin (GelMA). Chondrocytes or mesenchymal stem cells (MSCs) were then encapsulated in the bioinks and 3D bioprinted using a custom-built extrusion bioprinter. UV and double-ionic (BaCl2 and CaCl2) crosslinking was deployed following bioprinting to strengthen bioink stability in culture. Chondrocyte and MSC spheroids were also bioprinted to accelerate cell growth and development of ECM in bioprinted constructs. Excellent viability of chondrocytes and MSCs was seen following bioprinting (>95%) and maintained in culture over 28 days, with accelerated cell growth seen with inclusion of MSC or chondrocyte spheroids in bioinks (p<0.05). Bioprinted 10mm diameter constructs maintained shape in culture over 28 days, whilst construct degradation rates and mechanical properties were improved with addition of AlgMA (p<0.05). Composite bioinks were also injected into in vitro osteochondral defects (OCDs) and crosslinked in situ, with maintained cell viability and repair of osteochondral defects seen over a 14-day period. In conclusion we developed novel composite AlgMA/GelMA bioinks that can be triple-crosslinked, facilitating dense chondrocyte and MSC growth in constructs following 3D bioprinting. The bioink can be injected or 3D bioprinted to successfully repair in vitro OCDs, offering hope for a new approach to treating AC defects

As arthroplasty demand grows worldwide, the need for a novel cost-effective treatment option for articular cartilage (AC) defects tailored to individual patients has never been greater. 3D bioprinting can deposit patient cells and other biomaterials in user-defined patterns to build tissue constructs from the “bottom-up,” potentially offering a new treatment for AC defects. Novel composite bioinks were created by mixing different ratios of methacrylated alginate (AlgMA) with methacrylated gelatin (GelMA) and collagen. Chondrocytes and mesenchymal stem cells (MSCs) were then encapsulated in the bioinks and 3D bioprinted using a custom-built extrusion bioprinter. UV and double-ionic (BaCl2 and CaCl2) crosslinking was deployed following bioprinting to strengthen bioink stability in culture. Chondrocyte and MSC spheroids were also bioprinted to accelerate cell growth and development of ECM in bioprinted constructs. Excellent viability of chondrocytes and MSCs was seen following bioprinting (>95%) and maintained in culture, with accelerated cell growth seen with inclusion of cell spheroids in bioinks (p<0.05). Bioprinted 10mm diameter constructs maintained shape in culture over 28 days, whilst construct degradation rates and mechanical properties were improved with addition of AlgMA (p<0.05). Composite bioinks were also injected into in vitro osteochondral defects and crosslinked in situ, with maintained cell viability and repair of osteochondral defects seen over a 14-day period. In conclusion, we developed novel composite bioinks that can be triple-crosslinked, facilitating successful chondrocyte and MSC growth in 3D bioprinted scaffolds and in vitro repair of an osteochondral defect model. This offers hope for a new approach to treating AC defects

Aims. Minimally manipulated cells, such as autologous bone marrow concentrates (BMC), have been investigated in orthopaedics as both a primary therapeutic and augmentation to existing restoration procedures. However, the efficacy of BMC in combination with tissue engineering is still unclear. In this study, we aimed to determine whether the addition of BMC to an osteochondral scaffold is safe and can improve the repair of large osteochondral defects when compared to the scaffold alone. Methods. The ovine femoral condyle model was used. Bone marrow was aspirated, concentrated, and used intraoperatively with a collagen/hydroxyapatite scaffold to fill the osteochondral defects (n = 6). Tissue regeneration was then assessed versus the scaffold-only group (n = 6). Histological staining of cartilage with alcian blue and safranin-O, changes in chondrogenic gene expression, microCT, peripheral quantitative CT (pQCT), and force-plate gait analyses were performed. Lymph nodes and blood were analyzed for safety. Results. The results six months postoperatively showed that there were no significant differences in bone regrowth and mineral density between BMC-treated animals and controls. A significant upregulation of messenger RNA (mRNA) for types I and II collagens in the BMC group was observed, but there were no differences in the formation of hyaline-like cartilage between the groups. A trend towards reduced sulphated glycosaminoglycans (sGAG) breakdown was detected in the BMC group but this was not statistically significant. Functional weightbearing was not affected by the inclusion of BMC. Conclusion. Our results indicated that the addition of BMC to scaffold is safe and has some potentially beneficial effects on osteochondral-tissue regeneration, but not on the functional endpoint of orthopaedic interest. Cite this article: Bone Joint Res 2021;10(10):677–689

Aims. To explore the efficacy of extracorporeal shockwave therapy (ESWT) in the treatment of osteochondral defect (OCD), and its effects on the levels of transforming growth factor (TGF)-β, bone morphogenetic protein (BMP)-2, -3, -4, -5, and -7 in terms of cartilage and bone regeneration. Methods. The OCD lesion was created on the trochlear groove of left articular cartilage of femur per rat (40 rats in total). The experimental groups were Sham, OCD, and ESWT (0.25 mJ/mm. 2. , 800 impulses, 4 Hz). The animals were euthanized at 2, 4, 8, and 12 weeks post-treatment, and histopathological analysis, micro-CT scanning, and immunohistochemical staining were performed for the specimens. Results. In the histopathological analysis, the macro-morphological grading scale showed a significant increase, while the histological score and cartilage repair scale of ESWT exhibited a significant decrease compared to OCD at the 8- and 12-week timepoints. At the 12-week follow-up, ESWT exhibited a significant improvement in the volume of damaged bone compared to OCD. Furthermore, immunohistochemistry analysis revealed a significant decrease in type I collagen and a significant increase in type II collagen within the newly formed hyaline cartilage following ESWT, compared to OCD. Finally, SRY-box transcription factor 9 (SOX9), aggrecan, and TGF-β, BMP-2, -3, -4, -5, and -7 were significantly higher in ESWT than in OCD at 12 weeks. Conclusion. ESWT promoted the effect of TGF-β/BMPs, thereby modulating the production of extracellular matrix proteins and transcription factor involved in the regeneration of articular cartilage and subchondral bone in an OCD rat model. Cite this article: Bone Joint Res 2024;13(7):342–352

Purpose. Platelet-derived growth factor-BB (PDGF-BB) is a well characterized wound healing protein known to be chemotactic and mitogenic for cells of mesenchymal origin, including osteoblasts and chondrocytes. Biocompatible scaffolds, combined with growth factors such as PDGF-BB, have potential to stimulate regeneration and repair of osseous and cartilaginous tissues. The purpose of this study was to determine the efficacy and safety of recombinant human PDGF-BB (rhPDGF-BB) combined with a collagen implant to augment healing of osteochondral defects. Method. A single osteochondral defect (8mm x 8mm) was created in the medial femoral condyle of 32 adult goats. Collagen implants(8.5mm x 8mm) hydrated with four doses of rhPDGF-BB (0g, 15g, 75g, 500g) were press-fit into the defect. Defects in four animals were left untreated. All goats were sacrificed 12 weeks postoperatively. Macroscopic evaluation and quantitative CT analyses were performed. Histologic sections were stained with Safranin O/Fast Green and assessed with a modified ODriscoll scoring scale for cartilage and bone repair. Significance was determined by One-Way ANOVA or nonparametric Kruskal-Wallis. Results. Macroscopic evaluation indicated significant improvement of the gross cartilage repair score for the rhPDGF-BB treatment groups compared to the 0g rhPDGF-BB control (500g;0g) and empty defect groups (500,75,15g; Empty). MicroCT analysis indicated a significant increase in trabecular number for the 500g group compared to 0g control, 75g, and Empty groups(p=0.004). Average bone volume reconstitution for the 500g group was increased (58.8%) compared to the 0g control. The total cartilage repair score was significantly improved (p=0.048) in the 500g treatment group (14.30.3) compared to the 0g control group (12.10.4). All rhPDGF-BB treatment groups exhibited increased Safranin-O staining of the matrix compared to the 0g control group, and a significantly decreased incidence(p=0.01) of subchondral cyst formation compared to the empty defect group. Conclusion. The results of this study indicate that rhPDGF-BB, combined with a collagen implant, is safe and improves repair of large osteochondral defects located in a high-load bearing region in a caprine model. Increases in gross scoring and histopathologic cartilage repair score for the rhPDGF-BB treatment groups, in addition to the presence of bony bridging, especially for the 500g rhPDGF-BB treatment group, indicate enhanced reconstitution of the subchondral bone and overlying repair tissue. The cartilage repair score was increased, on average, in the empty defect group relative to the 0g rhPDGF-BB group, however this score may be partially inflated due to collapse of the surrounding native tissue into the defect. Combined with a significant decrease in cyst formation in all rhPDGF-BB treatment groups, these results suggest that rhPDGF-BB, combined with a collagen implant, may have promise as a therapeutic agent for osteochondral defect repair

Objectives. The major problem with repair of an articular cartilage injury is the extensive difference in the structure and function of regenerated, compared with normal cartilage. Our work investigates the feasibility of repairing articular osteochondral defects in the canine knee joint using a composite lamellar scaffold of nano-ß-tricalcium phosphate (ß-TCP)/collagen (col) I and II with bone marrow stromal stem cells (BMSCs) and assesses its biological compatibility. Methods. The bone–cartilage scaffold was prepared as a laminated composite, using hydroxyapatite nanoparticles (nano-HAP)/collagen I/copolymer of polylactic acid–hydroxyacetic acid as the bony scaffold, and sodium hyaluronate/poly(lactic-co-glycolic acid) as the cartilaginous scaffold. Ten-to 12-month-old hybrid canines were randomly divided into an experimental group and a control group. BMSCs were obtained from the iliac crest of each animal, and only those of the third generation were used in experiments. An articular osteochondral defect was created in the right knee of dogs in both groups. Those in the experimental group were treated by implanting the composites consisting of the lamellar scaffold of ß-TCP/col I/col II/BMSCs. Those in the control group were left untreated. Results. After 12 weeks of implantation, defects in the experimental group were filled with white semi-translucent tissue, protruding slightly over the peripheral cartilage surface. After 24 weeks, the defect space in the experimental group was filled with new cartilage tissues, finely integrated into surrounding normal cartilage. The lamellar scaffold of ß-TCP/col I/col II was gradually degraded and absorbed, while new cartilage tissue formed. In the control group, the defects were not repaired. Conclusion. This method can be used as a suitable scaffold material for the tissue-engineered repair of articular cartilage defects. Cite this article: Bone Joint Res 2015;4:56–64

Background. Articular cartilage has poor repair properties and poses a significant challenge in orthopaedics. Damage as a result of disease or injury frequently leads to formation of an osteochondral defect. Conventional repair methods, including allograft, autograft and microfracture, have a number of disadvantages in terms of cost, associated technical challenges and the requirement for multiple operations. A novel tri-layered scaffold developed in our lab, addresses this issue as it closely matches the structure and composition of osteochondral tissue. Methods. In vivo assessment was carried out in a caprine model by creating 6 mm × 6 mm defects in the medial femoral condyle and lateral trochlear ridge of each joint. Defects were implanted with the tri-layered scaffold and for comparison also with a market-leading scaffold, while some of defects were left empty, acting as a control. Assessment was carried out at 3 month, 6 month and 12 month time points. The quality of the repair at the various time points was graded macroscopically and microscopically by histological staining of the samples and also assessed using micro-CT (computed tomography) analysis. Results. From 3 to 6 months the tri-layered scaffold group showed improved macroscopic repair compared to the empty defect group. Greater levels of bone formation in the tri-layered scaffold group were evident on micro-CT evaluation, and this was confirmed by histological staining. Finally, at 12 months superior results were seen in the tri-layered scaffold group with formation of hyaline-like cartilage within the defect and regeneration of the subchondral bone. Conclusions. Positive results to date show that the tri-layered to be a promising method for cartilage repair and regeneration by promoting natural cartilage re-growth. It negates the need for other biological agents such as genes and growth factors by stimulating the native tissue osteochondral repair mechanism. Level of evidence. Animal research. Ethics Approval. The Ethics Committee of the University College Dublin (UCD) (AREC-P-11-31) approved this study and the Irish Government Department of Health (B100/4317) granted an animal license

Early detection of knee osteoarthritis (OA) is critical for possible preventive treatment, such as weight loss, physical activity and sports advice and restoring biomechanics, to postpone total knee arthroplasty (TKA). Specific biomarkers for prognosis and early diagnosis of OA are lacking. Therefore, in this study, we analyzed the lipid profiles of different tissue types within Hoffa's fat pad (HFP) of OA and cartilage defect (CD) patients, using matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI). The HFP has already been shown to play an important role in the inflammatory process in OA by prostaglandin release. Additionally, MALDI-MSI allows us to investigate on tissue lipid distribution at molecular level, which makes it a promising tool for the detection of disease specific biomarkers for OA development.

Samples of HFP were obtained of patients undergoing surgical treatment for OA (n=3) (TKA) or CD (n=3) (cartilage repair). In all cases, tissue was obtained without patient harm. HFP samples were washed in phosphate buffered saline (PBS) and snap-frozen directly after surgical dissection to remove redundant blood contamination and to prevent as much tissue degradation as possible. Tissue sections were cut at 15 µm thickness in a cryostat (Leica Microsystems, Wetzlar) and deposited on indium tin oxide glass slides. Norharmane (Sigma-Aldrich) matrix was sublimed onto the tissue using the HTX Sublimator (HTX Technologies, Chapel Hill). µMALDI-MSI was performed using Synapt G2Si (Waters) at 50 µm resolution in positive ion mode. MS/MS fragmentation was performed for lipid identification. Data were processed with in-house Tricks for MATLAB and analyzed using principle component analysis (PCA) and verlan

OA and CD HFP specific lipid profiles were revealed by MALDI-MSI followed by PCA and DA. With these analyses we were able to distinguish different tissue types within HFP of different patient groups. Further discriminant analysis showed HFP intra-tissue heterogeneity with characteristic lipid profiles specific for connective and adipose tissues, but also for synovial tissue and blood vessels, revealing the high molecular complexity of this tissue. As expected, lipid signals were lower at the site of the connective tissue, compared to the adipose tissue. In particular, tri-acyl glycerol, di-acyl glycerol, sphingomyelin and phosphocholine species were differently abundant in the adipose tissue of HFP of OA compared to CD.

To our knowledge, this is the first study comparing lipid profiles in HFP of OA patients with CD patients using MALDI-MSI. Our results show different lipid profiles between OA and CD patients, as well as intra-tissue heterogeneity within HFP, rendering MALDI-MSI as a useful technology for OA biomarker discovery. Future research will focus on expanding the number of subjects and the improvement of lipid detection signals.

Background

The gradient structure of osteochondral tissue, with bone, calcified and cartilage regions, challenges the design of biomaterials for defect repair. A novel biomimetic tri-layered collagen-based scaffold, designed to replicate these 3 anatomical layers, has been developed within our group and has shown success as an off-the-shelf product in treatment of focal defects in several animal models by recruiting host cells and directing them to form bone and cartilage in the requisite layers. This study aimed to elucidate the mechanism by which the extracellular matrix macromolecules in the scaffold directed stem cell differentiation in each layer.

Aims. The present study investigates the effectiveness of platelet-rich plasma (PRP) gel without adjunct to induce cartilage regeneration in large osteochondral defects in a rabbit model. Methods. A bilateral osteochondral defect was created in the femoral trochlear groove of 14 New Zealand white rabbits. The right knees were filled with PRP gel and the contralateral knees remained untreated and served as control sides. Some animals were killed at week 3 and others at week 12 postoperatively. The joints were harvested and assessed by Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) MRI scoring system, and examined using the International Cartilage Repair Society (ICRS) macroscopic and ICRS histological scoring systems. Additionally, the collagen type II content was evaluated by the immunohistochemical staining. Results. After 12 weeks post-surgery, the defects of the PRP group were repaired by hyaline cartilage-like tissue. However, incomplete cartilage regeneration was observed in the PRP group for three weeks. The control groups showed fibrocartilaginous or fibrous tissue, respectively, at each timepoint. Conclusion. Our study proved that the use of PRP gel without any adjuncts could successfully produce a good healing response and resurface the osteochondral defect with a better quality of cartilage in a rabbit model. Cite this article: Bone Joint Res 2021;10(3):192–202

Joint surface restoration of deep osteochondral defects represents a significant unmet clinical need. Moreover, untreated lesions lead to a high rate of osteoarthritis. The current strategies to repair deep osteochondral defects such as osteochondral grafting or sandwich strategies combining bone autografts with ACI/MACI fail to generate long-lasting osteochondral interfaces. Herein, we investigated the capacity of juvenile Osteochondral Grafts (OCGs) to repair osteochondral defects in skeletally mature animals. With this regenerative model in view, we set up a new biological, bilayered, and scaffold-free Tissue Engineered (TE) construct for the repair of the osteochondral unit of the knee. Skeletally immature (5 weeks old) and mature (11 weeks old) Lewis rats were used. Cylindrical OCGs were excised from the intercondylar groove of the knee of skeletally immature rats and transplanted into osteochondral defects created in skeletally mature rats. To create bilayered TE constructs, micromasses of human periosteum-derived progenitor cells (hPDCs) and human articular chondrocytes (hACs) were produced in vitro using chemically defined medium formulations. These constructs were subsequently implanted orthotopically in vivo in nude rats. At 4 and 16 weeks after surgery, the knees were collected and processed for subsequent 3D imaging analysis and histological evaluation. Micro-computed tomography (µCT), H&E and Safranin O staining were used to evaluate the degree of tissue repair. Our results showed that the osteochondral unit of the knee in 5 weeks old rats exhibit an immature phenotype, displaying active subchondral bone formation through endochondral ossification, the absence of a tidemark, and articular chondrocytes oriented parallel to the articular surface. When transplanted into skeletally mature animals, the immature OCGs resumed their maturation process, i.e., formed new subchondral bone, partially established the tidemark, and maintained their Safranin O-positive hyaline cartilage at 16 weeks after transplantation. The bilayered TE constructs (hPDCs + hACs) could partially recapitulate the cascade of events as seen with the immature OCGs, i.e., the regeneration of the subchondral bone and the formation of the typical joint surface architecture, ranging from non-mineralized hyaline cartilage in the superficial layers to a progressively mineralized matrix at the interface with a new subchondral bone plate. Cell-based TE constructs displaying a hierarchically organized structure comprising of different tissue forming units seem an attractive new strategy to treat osteochondral defects of the knee

Aims. Implantation of ultra-purified alginate (UPAL) gel is safe and effective in animal osteochondral defect models. This study aimed to examine the applicability of UPAL gel implantation to acellular therapy in humans with cartilage injury. Methods. A total of 12 patients (12 knees) with symptomatic, post-traumatic, full-thickness cartilage lesions (1.0 to 4.0 cm. 2. ) were included in this study. UPAL gel was implanted into chondral defects after performing bone marrow stimulation technique, and assessed for up to three years postoperatively. The primary outcomes were the feasibility and safety of the procedure. The secondary outcomes were self-assessed clinical scores, arthroscopic scores, tissue biopsies, and MRI-based estimations. Results. No obvious adverse events related to UPAL gel implantation were observed. Self-assessed clinical scores, including pain, symptoms, activities of daily living, sports activity, and quality of life, were improved significantly at three years after surgery. Defect filling was confirmed using second-look arthroscopy at 72 weeks. Significantly improved MRI scores were observed from 12 to 144 weeks postoperatively. Histological examination of biopsy specimens obtained at 72 weeks after implantation revealed an extracellular matrix rich in glycosaminoglycan and type II collagen in the reparative tissue. Histological assessment yielded a mean overall International Cartilage Regeneration & Joint Preservation Society II score of 69.1 points (SD 10.4; 50 to 80). Conclusion. This study provides evidence supporting the safety of acellular UPAL gel implantation in facilitating cartilage repair. Despite being a single-arm study, it demonstrated the efficacy of UPAL gel implantation, suggesting it is an easy-to-use, one-step method of cartilage tissue repair circumventing the need to harvest donor cells. Cite this article: Bone Joint J 2023;105-B(8):880–887

Osteochondral glenoid loss is associated with recurrent shoulder instability. The critical threshold for surgical stabilization is multidimensional and conclusively unknown. The aim of this work was to provide a well- measurable surrogate parameter of an unstable shoulder joint for the frequent anterior-inferior dislocation direction. The shoulder stability ratio (SSR) of 10 paired human cadaveric glenoids was determined in anterior-inferior dislocation direction. Osteochondral defects were simulated by gradually removing osteochondral structures in 5%-stages up to 20% of the intact diameter. The glenoid morphological parameters glenoid depth, concavity gradient, and defect radius were measured at each stage by means of optical motion tracking. Based on these parameters, the osteochondral stability ratio (OSSR) was calculated. Correlation analyses between SSR and all morphological parameters, as well as OSSR were performed. The loss of SSR, concavity gradient, depth and OSSR with increasing defect size was significant (all p<0.001). The loss of SSR strongly correlated with the losses of concavity gradient (PCC = 0.918), of depth (PCC = 0.899), and of OSSR (PCC = 0.949). In contrast, the percentage loss based on intact diameter (defect size) correlated weaker with SSR (PCC=0.687). Small osteochondral defects (≤10%) led to significantly higher SSR decrease in small glenoids (diameter <25mm) compared to large (≥ 25mm) ones (p ≤ 0.009). From a biomechanical perspective, the losses of concavity gradient, glenoid depth and OSSR correlate strong with the loss of SSR. Therefore, especially the loss of glenoidal depth may be considered as a valid and reliable alternative parameter to describe shoulder instability. Furthermore, smaller glenoids are more vulnerable to become unstable in case of small osteochondral loosening. On the other hand, the standardly used percentage defect size based on intact diameter correlates weaker with the magnitude of instability and may therefore not be a valid parameter for judgement of shoulder instability

Introduction. Homogenous and consistent preparations of mesenchymal stem cells (MSCs) can be acquired by selecting them for integrin α10β1 (integrin a10-MSCs). Safety and efficacy of intra-articular injection of allogeneic integrin a10-MSCs were shown in two post-traumatic osteoarthritis horse studies. The current study investigated immunomodulatory capacities of human integrin a10-MSCs in vitro and their cell fait after intra-articular injection in rabbits. Method. The concentration of produced immunomodulatory factors was measured after licensing integrin a10-MSCs with pro-inflammatory cytokines. Suppression of T-cell proliferation was determined in co-cultures with carboxyfluorescein N-succinimidyl ester (CFSE) labelled human peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3/CD28 and measuring the CFSE intensity of CD4+ cells. Macrophage polarization was assessed in co-cultures with differentiated THP-1 cells stimulated with lipopolysaccharide and analysing the M2 macrophage cell surface markers CD163 and CD206. In vivo homing and regeneration were investigated by injecting superparamagnetic iron oxide nanoparticles conjugated with Rhodamine B-labeled human integrin a10-MSCs in rabbits with experimental osteochondral defects. MSC distribution in the joint was followed by MRI and fluorescence microscopy. Result. The production of the immunomodulatory factors indoleamine 2,3-dioxygenase and prostaglandin E2 was increased after inflammatory licensing integrin a10-MSCs. Co-cultures with integrin a10-MSCs suppressed T-cell proliferation and increased the frequency of M2 macrophages. In vivo injected integrin a10-MSCs homed to osteochondral defects and were detected in the repair tissue of the defects up to 10 days after injection, colocalized with aggrecan and type II collagen. Conclusion. This study showed that human integrin a10-MSCs have immunomodulatory capacities and in vivo can home to the site of osteochondral damage and directly participate in cartilage regeneration. This suggests that human integrin α10β1-selected MSCs may be a promising therapy for osteoarthritis with dual mechanisms of action consisting of immunomodulation and homing to damage followed by early engraftment and differentiation into chondrocyte-like cells that deposit hyaline cartilage matrix molecules

In this study, we developed biocompatible adhesive which enables implanted chondrogenic-enhanced hASCs being strongly fixed to the lesion site of defected cartilage. The bioengineered mussel adhesive protein (MAP) was produced and purified using a bacterial expression system as previously reported. The cell encapsulated coacervate was formulated with two polyelectrolyte, the MAP and 723kDa hyaluronic acid (HA). MAP formed liquid microdroplets with HA and subsequently gelated into microparticles, which is highly viscous and strongly adhesive. The MAP with chondro-induced hASCs were implanted on the osteochondral defect created in the patellar groove/condyle of OA-induced rabbits. Rabbits were allocated to three different groups as follows: Group1 – Fibrin only; Group2 – Fibrin with hASCs (1.5×10. 6. chondro-induced hASCs); Group3; MAP with hASCs. The implanted cells were labeled with a fluorescent dye for in vivo visualization. After 35 days, fluorescent signals were more potently detected for MAP with hASCs group than Fibrin with hASCs group in osteochondral defect model. Moreover, histological assessment showed that MAP with hASCs group had the best healing and covered with hyaline cartilage-like tissue. The staining image shows that MAP with hASCs group were filled with perfectly differentiated chondrocytes. Although Fibrin with hASCs group had better healing than fibrin only group, it was filled with fibrous cartilage which owes its flexibility and toughness. As MAP with hASCs group has higher possibility of differentiating to complete cartilage, Fibrin only group and Fibrin with hASCs group have failed to treat OA by rehabilitating cartilage. In order to clarify the evidence of remaining human cell proving efficacy of newly developed bioadhesive, human nuclear staining was proceeded with sectioned rabbit cartilage tissue. The results explicitly showed MAP with hASCs group have retained more human cells than Fibrin only and Fibrin with hASCs groups. We investigated the waterproof bioadhesive supporting transplanted cells to attach to defect lengthily in harsh environment, which prevents cells from leaked to other region of cartilage. Collectively, the newly developed bio-adhesive, MAP, could be successfully applied in OA treatment as a waterproof bioadhesive with the capability of the strong adhesion to target defect sites

Osteochondral (OC) defects of the knee are associated with pain and significant limitation of activity. Studies have demonstrated the therapeutic efficacy of mesenchymal stem cell (MSC) therapies in treating osteochondral defects. There is increasing evidence that the efficacy of MSC therapies may be a result of the paracrine secretion, particularly exosomes. Here, we examine the effects of MSC exosomes in combination with Hyaluronic Acid (HA) as an injectable therapy on functional osteochondral regeneration in a rabbit osteochondral defect model. Exosomes were purified from human MSC conditioned medium by size fractionation. A circular osteochondral defect of 4.5 mm diameter and 2.5 mm depth was surgically created in the trochlear grooves of 16 rabbit knees. Thereafter, eight knees received three weekly injections of 200 µg of exosomes in one ml of 3% HA, and the remaining eight knees received three weekly injections of one ml of 3% HA only. The rabbits were sacrificed at six weeks. Analyses were performed by macroscopic and histological assessments, and functional competence was analysed via Young Modulus calculation at five different points (central, superior, inferior, medial and lateral) of the repaired osteochondral defect site. MSC exosomes displayed a modal size of 100 nm and expressed exosome markers (CD81, TSG101 and ALIX). When compared to HA alone, MSC exosomes in combination with HA showed significantly better repair histologically and biomechanically. The Young Modulus was higher in 4 out of the 5 points. In the central region, the Young Modulus of MSC exosome and HA combination therapy was significantly higher: 5.42 MPa [SD=1.19, 95% CI: 3.93–6.90] when compared to HA alone: 2.87 MPa [SD=2.10, 95% CI: 0.26–5.49], p < 0 .05. The overall mean peripheral region was also significantly higher in the MSC exosome and HA combination therapy group: 5.87 MPa [SD=1.19, 95% CI: 4.40–7.35] when compared to HA alone: 2.70 MPa [SD=1.62, 95% CI: 0.79–4.71], p < 0 .05. The inferior region showed a significantly higher Young Modulus in the combination therapy: 7.34 MPa [SD=2.14, 95% CI: 4.68–10] compared to HA alone: 2.92 MPa [SD=0.98, 95% CI: 0.21–5.63], p < 0.05. The superior region showed a significantly higher Young Modulus in the combination therapy: 7.31 MPa [SD=3.29, 95% CI: 3.22–11.39] compared to HA alone: 3.59 MPa [SD=2.55, 95% CI: 0.42–6.76], p < 0.05. The lateral region showed a significantly higher Young Modulus in the combination therapy: 8.05 MPa [SD=2.06, 95% CI: 5.49–10.61] compared to HA alone: 3.56 MPa [SD=2.01, 95% CI: 1.06–6.06], p < 0.05. The medial region showed a higher Young Modulus in the combination therapy: 6.68 MPa [SD=1.48, 95% CI: 4.85–8.51] compared to HA alone: 3.45 MPa [SD=3.01, 95% CI: −0.29–7.19], but was not statistically significant. No adverse tissue reaction was observed in all the immunocompetent animals treated with MSC exosomes. Three weekly injections of MSC exosomes in combination with HA therapy results in a more functional osteochondral regeneration as compared to HA alone