Coralline hydroxyapatite is a suitable bone graft substitute in an intra-articular goat defect model

A New Method for Creating Impact-Induced Intra-Articular Fractures in a Rabbit Model Induces Severe Post-Traumatic Osteoarthritis

OBJECTIVES

The objective of this work was to develop a model of intra-articular fracture (IAF) in a rabbit and document the speed and severity of degenerative joint changes after fracture fixation.

METHODS

With Institutional Animal Care & Use Committee approval, impact-induced IAFs were created in the distal tibia of 16 New Zealand White rabbits. Fractures were fixed with a plate and screws. Pain and function were monitored at regular postoperative intervals with limb loading analysis. Twelve or 26 weeks after fracture, animals were euthanized for histological assessment of cartilage degeneration and micro-computed tomography analysis of bone histomorphometry.

RESULTS

Eleven animals successfully completed the study. Maximum foot force in the fractured limb was 41% ± 21% lower than preoperative values ( P = 0.006) 12 weeks after fracture and remained 25% ± 13% lower ( P = 0.081) after 26 weeks. Cortical bone mineral density in micro-computed tomography images was 34% ± 13% lower 12 weeks after fracture ( P < 0.001) and remained (42% ± 8%) lower 26 weeks after fracture ( P < 0.001). Twelve weeks after fracture, Mankin scores of cartilage degeneration were significantly higher in the medial talus ( P = 0.007), lateral talus ( P < 0.001), medial tibia ( P = 0.017), and lateral tibia ( P = 0.002) of the fractured limb compared with the uninjured contralateral limb. Average Mankin scores in the talus increased from 12 to 26 weeks (5.9 ± 0.9 to 9.4 ± 0.4; P < 0.001 lateral; 5.4 ± 1.8 to 7.8 ± 2.0; P = 0.043 medial), indicating substantial and progressive joint degeneration.

CONCLUSIONS

The ankle joint of the New Zealand White rabbit provides the smallest available model of impact-induced IAF that can be treated with clinically relevant techniques and replicates key features of healing and degeneration found in human patients.

Synthetic Blocks for Bone Regeneration: A Systematic Review and Meta-Analysis

This systematic review is aimed at evaluating the effectiveness of synthetic block materials for bone augmentation in preclinical in vivo studies. An electronic search was performed on Pubmed, Scopus, EMBASE. Articles selected underwent risk-of-bias assessment. The outcomes were: new bone formation and residual graft with histomorphometry, radiographic bone density, soft tissue parameters, complications. Meta-analysis was performed to compare new bone formation in test (synthetic blocks) vs. control group (autogenous blocks or spontaneous healing). The search yielded 214 articles. After screening, 39 studies were included, all performed on animal models: rabbits (n = 18 studies), dogs (n = 4), rats (n = 7), minipigs (n = 4), goats (n = 4), and sheep (n = 2). The meta-analysis on rabbit studies showed significantly higher new bone formation for synthetic blocks with respect to autogenous blocks both at four-week (mean difference (MD): 5.91%, 95% confidence intervals (CI): 1.04, 10.79%, p = 0.02) and at eight-week healing (MD: 4.44%, 95% CI: 0.71, 8.17%, p = 0.02). Other animal models evidenced a trend for better outcomes with synthetic blocks, though only based on qualitative analysis. Synthetic blocks may represent a viable resource in bone regenerative surgery for achieving new bone formation. Differences in the animal models, the design of included studies, and the bone defects treated should be considered when generalizing the results. Clinical studies are needed to confirm the effectiveness of synthetic blocks in bone augmentation procedures.

Synthetic and Marine-Derived Porous Scaffolds for Bone Tissue Engineering

Bone is a vascularized and connective tissue. The cortical bone is the main part responsible for the support and protection of the remaining systems and organs of the body. The trabecular spongy bone serves as the storage of ions and bone marrow. As a dynamic tissue, bone is in a constant remodelling process to adapt to the mechanical demands and to repair small lesions that may occur. Nevertheless, due to the increased incidence of bone disorders, the need for bone grafts has been growing over the past decades and the development of an ideal bone graft with optimal properties remains a clinical challenge. This review addresses the bone properties (morphology, composition, and their repair and regeneration capacity) and puts the focus on the potential strategies for developing bone repair and regeneration materials. It describes the requirements for designing a suitable scaffold material, types of materials (polymers, ceramics, and composites), and techniques to obtain the porous structures (additive manufacturing techniques like robocasting or derived from marine skeletons) for bone tissue engineering applications. Overall, the main objective of this review is to gather the knowledge on the materials and methods used for the production of scaffolds for bone tissue engineering and to highlight the potential of natural porous structures such as marine skeletons as promising alternative bone graft substitute materials without any further mineralogical changes, or after partial or total transformation into calcium phosphate.

Osteogenic Potential of Human Umbilical Cord Mesenchymal Stem Cells on Coralline Hydroxyapatite/Calcium Carbonate Microparticles

Coralline hydroxyapatite/calcium carbonate (CHACC) is a biodegradable and osteoconductive bone graft material with promising clinical performance. CHACC has been shown to support proliferation and osteogenic differentiation of human bone marrow mesenchymal stem cells (MSCs) in vitro and demonstrated to work as a functional scaffold for bone formation in vivo. Umbilical cord matrix is a more accessible and abundant tissue source of MSCs, but its osteogenic capacity in comparison to human bone marrow when cultured on CHACC has not yet been demonstrated. In this study, we assessed the osteogenic differentiation capacity of human MSCs, isolated from bone marrow and umbilical cord matrix and characterised by flow cytometry, when cultured on 200–300 μm CHACC granules. The 3D cultures were characterised by brightfield and scanning electron microscopy (SEM). Osteogenic potential was assessed by immunocytochemistry and qPCR for key markers of bone differentiation (alkaline phosphatase, runx2, type I collagen, and osteocalcin). By day 1, the MSCs had enveloped the surface of the CHACC granules to form organoids, and by day 7, cells had proliferated to bridge nearby organoids. Extracellular matrix deposition and osteogenic differentiation were demonstrated by MSCs from both tissue sources at day 21. However, MSCs from bone marrow demonstrated superior osteogenic differentiation capability compared to those from umbilical cord matrix. In conclusion, it is possible to culture and induce osteogenic differentiation of umbilical cord matrix MSCs on CHACC. Further research is required to optimise the osteogenicity of umbilical cord matrix MSCs to release their full potential as a readily available, accessible, and abundant tissue source for bone tissue engineering.

The healing of alveolar bone defects with novel bio-implants composed of Ad-BMP9-transfected rDFCs and CHA scaffolds

Cells, scaffolds, and growth factors play important roles in bone regeneration. Bone morphogenetic protein 9 (BMP9), a member of BMP family, could facilitate osteogenesis by regulating growth factors and promoting angiogenesis. Similar to other stem cells, rat dental follicle stem cells (rDFCs), the precursor cells of cementoblasts, osteoblasts and periodontal ligament cells, can self-renew and exhibit multipotential capacity. Coralline hydroxyapatite (CHA) has good biocompatibility and conductivity required for bone tissue engineering. Here, we reported that BMP9 could enhance the osteogenic differentiation of rDFCs in cell culture. Moreover, our results suggested that BMP9 acted through the Smad1/5/8 signaling pathway. We also produced a novel scaffold that encompasses bio-degradable CHA seeded with recombinant adenoviruses expressing BMP9-transfected rDFCs (Ad-BMP9-transfected rDFCs). With this implant, we achieved more alveolar bone regeneration in the alveolar bone defect compared to blank group, CHA group and rDFCs group. Our results provided a novel bio-implants composed of Ad-BMP9-transfected rDFCs and CHA scaffolds and its mechanism is regarding the activation of Smad1/5/8 signaling pathway in BMP9-induced rDFCs osteogenesis.

Bone defect animal models for testing efficacy of bone substitute biomaterials

Large bone defects are serious complications that are most commonly caused by extensive trauma, tumour, infection, or congenital musculoskeletal disorders. If nonunion occurs, implantation for repairing bone defects with biomaterials developed as a defect filler, which can promote bone regeneration, is essential. In order to evaluate biomaterials to be developed as bone substitutes for bone defect repair, it is essential to establish clinically relevant in vitro and in vivo testing models for investigating their biocompatibility, mechanical properties, degradation, and interactional with culture medium or host tissues. The results of the in vitro experiment contribute significantly to the evaluation of direct cell response to the substitute biomaterial, and the in vivo tests constitute a step midway between in vitro tests and human clinical trials. Therefore, it is essential to develop or adopt a suitable in vivo bone defect animal model for testing bone substitutes for defect repair. This review aimed at introducing and discussing the most available and commonly used bone defect animal models for testing specific substitute biomaterials. Additionally, we reviewed surgical protocols for establishing relevant preclinical bone defect models with various animal species and the evaluation methodologies of the bone regeneration process after the implantation of bone substitute biomaterials. This review provides an important reference for preclinical studies in translational orthopaedics.

Angiogenesis and bone regeneration of porous nano-hydroxyapatite/coralline blocks coated with rhVEGF165 in critical-size alveolar bone defects in vivo

To improve the regenerative performance of nano-hydroxyapatite/coralline (nHA/coral) block grafting in a canine mandibular critical-size defect model, nHA/coral blocks were coated with recombinant human vascular endothelial growth factor(165) (rhVEGF) via physical adsorption (3 μg rhVEGF165 per nHA/coral block). After the nHA/coral blocks and VEGF/nHA/coral blocks were randomly implanted into the mandibular box-shaped defects in a split-mouth design, the healing process was evaluated by histological observation and histomorphometric and immunohistological analyses. The histological evaluations revealed the ingrowth of newly formed blood vessels and bone at the periphery and cores of the blocks in both groups at both 3 and 8 weeks postsurgery, respectively. In the histomorphometric analysis, the VEGF/nHA/coral group exhibited a larger quantity of new bone formation at 3 and 8 weeks postsurgery. The percentages of newly formed bone within the entire blocks in the VEGF/nHA/coral group were 27.3% ± 8.1% and 39.3% ± 12.8% at 3 weeks and 8 weeks, respectively, and these values were slightly greater than those of the nHA/coral group (21.7% ± 3.0% and 32.6% ± 10.3%, respectively), but the differences were not significant (P>0.05). The immunohistological evaluations revealed that the neovascular density in the VEGF/nHA/coral group (146 ± 32.9 vessel/mm(2)) was much greater than that in the nHA/coral group (105 ± 51.8 vessel/mm(2)) at the 3-week time point (P<0.05), but no significant difference was observed at the 8-week time point (341 ± 86.1 and 269 ± 50.7 vessel/mm(2), respectively, P>0.05). The present study indicated that nHA/coral blocks might be optimal scaffolds for block grafting in critical-size mandibular defects and that additional VEGF coating via physical adsorption can promote angiogenesis in the early stage of bone healing, which suggests that prevascularized nHA/coral blocks have significant potential as a bioactive material for bone regeneration in large-scale alveolar defects.