Homologous recombination in embryonic stem cells was used to prepare transgenic mice with an inactivated Col2a1 gene for collagen 11, the major protein component of the extracellular matrix of cartilage. Heterozygous mice had a minimal phenotype. Homozygous mice developed into fetuses that were delivered vaginally but died either just before or shortly after birth. The cartilage in the mice consisted of highly disorganized chondrocytes with a complete lack of extracellular fibrils discernible by electron microscopy. There was no endochondrial bone or epiphyseal growth plate in long bones. However, many skeletal structures such as the cranium and ribs were normally developed and mineralized. The results demonstrate that a well-organized cartilage matrix is required as a primary tissue for development of some components of the vertebrate skeleton, but it is not essential for others.

Article type : Original Research Enamel matrix derivative promotes new bone formation in xenograft assisted maxillary anterior ridge preservation -a randomized controlled clinical trial.

No abstract

The scapholunate interosseous ligament (SLIL) is a frequently torn wrist ligament, and current surgical options for SLIL tears are suboptimal. This research aims to develop a novel multiphasic bone–ligament–bone scaffold (BLB) with a porous interface using 3D‐printing and cell sheet technology for the reconstruction of the dorsal scapholunate interosseous ligament. The BLB comprises two bone compartments bridged by aligned polycaprolactone fibers mimicking the architecture of the native tissue. Mechanical testing of the BLBs shows their ability to withstand physiological forces. Combination of the BLB with human bone marrow mesenchymal stem cell sheet demonstrates that the harvesting did not compromise cell viability, while allowing homogeneous distribution in the ligament compartment. The BLBs are loaded with cell sheets and bone morphogenetic protein‐2 in the ligament and bone compartment respectively prior to ectopic implantation into athymic rats. The histology demonstrates rapid tissue infiltration, high vascularization, and more importantly the maintenance of the compartmentalization as bone formation remains localized to the bone compartment despite the porous interface. The cells in the ligament compartment become preferentially aligned, and this proof‐of‐concept study demonstrates that the BLB can provide sufficient compartmentalization and fiber guiding properties necessary for the regeneration of the dorsal SLIL.

Hemoderivatives have utilized in an empirical manner, driven by clinical considerations, leading to the development of a plethora of manufacturing protocols. The purpose of this study was to investigate the composition and bioactivity of four common clinical-grade hemoderivates prepared using standardised methods. Four different hemoderivatives were obtained from sheep blood and divided into two groups: A-PRF/i-PRF (fresh) and P-PRP/L-PRP (anticoagulated). Thrombus (CLOT) was used as a control. Thrombocyte quantification, growth factor composition (IGF-I, VEGF, PDGF-BB, BMP-2), cell viability, migration and mineralization assay were evaluated. Platelet recovery was superior for L-PRP followed by P-PRP. A significant cumulative release of IGF-I and PDGF-BB was noted for A-PRF and L-PRP groups at early time points. Similar release profiles of BMP-2 and VEGF were noted in all protocols. Cell viability and migration assay have demonstrated a detrimental effect when the concentration was ≥60%. Moreover, at Day 21, i-PRF have demonstrated superior mineralisation properties when compared to all groups. A negative impact of A-PRF was demonstrated at high concentrations. Despite its low content in growth factors, i-PRF was the best performing blood product for inducing osteoblast mineralisation, and therefore could be the candidate of choice for utilisation in bone tissue engineering applications.

Neurogenic heterotopic ossifications (NHOs) are incapacitating heterotopic bones in periarticular muscles that frequently develop following traumatic brain or spinal cord injuries (SCI). Using our unique model of SCI-induced NHO, we have previously established that mononucleated phagocytes infiltrating injured muscles are required to trigger NHO via the persistent release of the proinflammatory cytokine oncostatin M (OSM). Because neutrophils are also a major source of OSM, we investigated whether neutrophils also play a role in NHO development after SCI. We now show that surgery transiently increased granulocyte colony-stimulating factor (G-CSF) levels in blood of operated mice, and that G-CSF receptor mRNA is expressed in the hamstrings of mice developing NHO. However, mice defective for the G-CSF receptor gene Csf3r, which are neutropenic, have unaltered NHO development after SCI compared to C57BL/6 control mice. Because the administration of recombinant human G-CSF (rhG-CSF) has been trialed after SCI to increase neuroprotection and neuronal regeneration and has been shown to suppress osteoblast function at the endosteum of skeletal bones in human and mice, we investigated the impact of a 7-day rhG-CSF treatment on NHO development. rhG-CSF treatment significantly increased neutrophils in the blood, bone marrow, and injured muscles. However, there was no change in NHO development compared to saline-treated controls. Overall, our results establish that unlike monocytes/macrophages, neutrophils are dispensable for NHO development following SCI, and rhG-CSF treatment post-SCI does not impact NHO development. Therefore, G-CSF treatment to promote neuroregeneration is unlikely to adversely promote or affect NHO development in SCI patients.

Objectives This study investigates the design, workflow, and manufacture of highly porous, resorbable additively manufactured, 3‐dimensional (3D) custom scaffolds for the regeneration of large volume alveolar bone defects. Materials and Methods Computed tomography (CT) scans of 5 posterior mandibular vertical bone defects were obtained. Surface masks (3D surface contours) of the recipient site were first isolated using a contrast threshold, transformed into 3D objects, and used to guide the formation of custom implant template models. To determine model accuracy and fit, the gap and overlap between the patient geometry models and the idealized template 3D models were quantified. Models were 3D printed from medical grade polycaprolactone (PCL) into porous scaffolds. For scaffold dimensional quantification, scaffolds were scanned using a micro‐computed tomography (µCT) scanner. Results The design and printing processes each achieved dimensional errors of <200 µm on average. The average gap between the template implant model and the scanned scaffold model was found to be 74 ± 14 µm. The printed scaffold was confirmed as having a porosity of 83.91%, a mean polymer or filament thickness of 200 ± 46 µm, and a mean pore size of 590 ± 243 µm. Conclusion The approach described in this study is straightforward, adaptable to a range of patient geometries, and results in the formation of reproducible, dimensionally accurate custom implants. These highly porous 3D structures manufactured from resorbable medical grade material represent a potentially transformative technology toward the clinical implementation of scaffold‐guided bone regeneration procedures.

The scapholunate interosseous ligament (SLIL) is a frequently torn wrist ligament and current surgical options for SLIL tears are suboptimal. This research aims to develop a novel multiphasic bone-ligament-bone scaffold (BLB) with a porous interface using 3D-printing and cell sheet technology for the reconstruction of the dorsal scapholunate interosseous ligament. The BLB scaffold comprised two bone compartments bridged by aligned polycaprolactone fibers mimicking the architecture of the native tissue. Mechanical testing of the BLBs showed their ability to withstand physiological forces. The BLBs were further combined with human bone marrow This article is protected by copyright. All rights reserved.3 mesenchymal stem cell sheet and this demonstrated that the harvesting did not compromise cell viability, while allowing homogeneous distribution in the ligament compartment. The BLBs were loaded with cell sheets and Bone Morphogenetic Protein-2 in the ligament and bone compartment respectively and implanted ectopically into athymic rats. The histology demonstrated a rapid tissue infiltration, high vascularization and more importantly, the maintenance of the compartmentalization as bone formation remained localized to the bone compartment despite the porous interface. The cells in the ligament compartment became preferentially aligned and this proof-of-concept study demonstrated that the BLB can provide sufficient compartmentalization and fiber guiding properties necessary for the regeneration of the dorsal SLIL.