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Type-H capillary endothelial cells control bone formation during embryogenesis and postnatal growth but few signalling mechanisms underpinning this influence have been characterised. Here, we identify a highly expressed type-H endothelial cell protein, Clec14a, and explore its role in coordinating osteoblast activity. Expression of Clec14a and its ligand, Mmrn2 are high in murine type-H endothelial cells but absent from osteoblasts. Clec14a -/- mice have premature condensation of the type-H vasculature and expanded distribution of osteoblasts and bone matrix, increased long-bone length and bone density indicative of accelerated skeletal development, and enhanced osteoblast maturation. Antibody-mediated blockade of the Clec14a-Mmrn2 interaction recapitulates the Clec14a -/- phenotype. Endothelial cell expression of Clec14a regulates osteoblast maturation and mineralisation activity during postnatal bone development in mice. This finding underscores the importance of type-H capillary control of osteoblast activity in bone formation and identifies a novel mechanism that mediates this vital cellular crosstalk., (© 2024. The Author(s).)

Introduction: Peri-implantitis is an inflammatory process around dental implants that is characterised by bone loss that may jeopardize the long-term survival of osseo integrated dental implants. The aim of this study was to create a surface coating on titanium abutments that possesses cellular adhesion and anti-microbial properties as a post-implant placement strategy for patients at risk of peri-implantitis., Materials and Methodsmethods: Titanium alloy Grade V stubs were coated with gold particles and then subjected to ceramic conversion treatment (CCT) at 620 °C for 3, 8 and 80 h. The surface characteristics and chemistry were assessed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. The leaching profile was investigated by inductively coupled plasma mass spectroscopy (ICP-MS) for all groups after 7, 14 and 28 days in contact with distilled water. A scratch test was conducted to assess the adhesion of the gold coating to the underlying titanium discs. Two bacterial species (Staphylococcus aureus (SA) & Fusobacterium nucleatum (FN)) were used to assess the antibacterial behaviour of the coated discs using a direct attachment assay test. The potential changes in surface chemistry by the bacterial species were investigated by grazing angle XRD., Results: The gold pre-coated titanium discs exhibited good stability of the coating especially after immersion in distilled water and after bacterial colonisation as evident by XRD analysis. Good surface adhesion of the coating was demonstrated for gold treated discs after scratch test analysis, especially titanium, following a 3-hour (3 H) ceramic conversion treatment. All coated discs exhibited significantly improved antimicrobial properties against both tested bacterial species compared to untreated titanium discs., Conclusions: Ceramic conversion treated titanium with a pre-deposited gold layer showed improved antimicrobial properties against both SA and FN species than untreated Ti-C discs. Scratch test analysis showed good adherence properties of the coated discs the oxide layer formed is firmly adherent to the underlying titanium substrate, suggesting that this approach may have clinical efficacy for coating implant abutments., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Advances in bioprinting have enabled the fabrication of complex tissue constructs with high speed and resolution. However, there remains significant structural and biological complexity within tissues that bioprinting is unable to recapitulate. Bone, for example, has a hierarchical organization ranging from the molecular to whole organ level. Current bioprinting techniques and the materials employed have imposed limits on the scale, speed, and resolution that can be achieved, rendering the technique unable to reproduce the structural hierarchies and cell-matrix interactions that are observed in bone. The shift toward biomimetic approaches in bone tissue engineering, where hydrogels provide biophysical and biochemical cues to encapsulated cells, is a promising approach to enhancing the biological function and development of tissues for in vitro modeling. A major focus in bioprinting of bone tissue for in vitro modeling is creating dynamic microenvironmental niches to support, stimulate, and direct the cellular processes for bone formation and remodeling. Hydrogels are ideal materials for imitating the extracellular matrix since they can be engineered to present various cues whilst allowing bioprinting. Here, recent advances in hydrogels and 3D bioprinting toward creating a microenvironmental niche that is conducive to tissue engineering of in vitro models of bone are reviewed., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Microfluidics have transformed diagnosis and screening in regenerative medicine. Recently, they are showing much promise in biofabrication. However, their adoption is inhibited by costly and drawn-out lithographic processes thus limiting progress. Here, multi-material fibers with complex core-shell geometries with sizes matching those of human arteries and arterioles are fabricated employing versatile microfluidic devices produced using an agile and inexpensive manufacturing pipeline. The pipeline consists of material extrusion additive manufacturing with an innovative continuously varied extrusion (CONVEX) approach to produce microfluidics with complex seamless geometries including, novel variable-width zigzag (V-zigzag) mixers with channel widths ranging from 100-400 µm and hydrodynamic flow-focusing components. The microfluidic systems facilitated rapid mixing of fluids by decelerating the fluids at specific zones to allow for increased diffusion across the interfaces. Better mixing even at high flow rates (100-1000 µL min -1 ) whilst avoiding turbulence led to high cell cytocompatibility (>86%) even when 100 µm nozzles are used. The presented 3D-printed microfluidic system is versatile, simple and efficient, offering a great potential to significantly advance the microfluidic platform in regenerative medicine., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)

Chronic wounds are a drain on global health services and remain a major area of unmet clinical need. Chronic wounds are characterised by a stable and stubborn bacterial biofilm which hinders innate immune response and delays or prevents wound healing. Bioactive glass (BG) fibres offer a promising novel treatment for chronic wounds by targeting the wound-associated biofilm. In this study, the antimicrobial properties of silver-doped BG fibres were tested against Pseudomonas aeruginosa biofilms, which are commonly found in chronic wound infections. Results showed that BG fibres doped with silver resulted in a 5log10 reduction in biofilm formation whereas silver-free fibres only reduced formation by log10, therefore silver-doped fibres possess stronger antimicrobial effects. Moreover, there appeared to be a synergistic effect between the fibres and the silver as the application of the silver-doped fibres placed directly in contact with the forming biofilm resulted in a higher reduction in biofilm formation compared to treatments either: using the dissolution ions, using BG powder, or when the fibres were placed in an insert above the biofilm, inhibiting physical contact, instead. This suggests that the physical properties of the fibres, as well as silver, influence biofilm formation. Finally, results demonstrated that silver chloride, which is not antimicrobial, forms and the concentrations of antimicrobial silver species, namely silver ions and nanoparticles, reduce over time when fibres are soaked in cell culture media, which partially explains why the silver-doped dissolution ions contained lower antimicrobial activity compared to the fibres. As silver chloride is more likely to form with increased temperature and time, the antimicrobial activity of silver-containing dissolution ions is highly dependent on the length of ageing and storage conditions. Many studies investigate the antimicrobial and cytotoxic properties of biomaterials through their dissolution products. However, instability of antimicrobial silver species due to silver chloride formation and its effect on antimicrobial properties of silver-based biomaterials has not been reported before and could influence past and future dissolution-based assays as results showed that the antimicrobial activity of silver-based dissolution ions can vary greatly depending on post processing steps and can therefore produce misleading data., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Sandeep Shirgill reports financial support was provided by 10.13039/501100000268Biotechnology and Biological Sciences Research Council. Gowsihan Poologasundarampillai reports financial support was provided by 10.13039/501100000266Engineering and Physical Sciences Research Council., (© 2023 The Authors.)

A lack of models that recapitulate the complexity of human bone marrow has hampered mechanistic studies of normal and malignant hematopoiesis and the validation of novel therapies. Here, we describe a step-wise, directed-differentiation protocol in which organoids are generated from induced pluripotent stem cells committed to mesenchymal, endothelial, and hematopoietic lineages. These 3D structures capture key features of human bone marrow-stroma, lumen-forming sinusoids, and myeloid cells including proplatelet-forming megakaryocytes. The organoids supported the engraftment and survival of cells from patients with blood malignancies, including cancer types notoriously difficult to maintain ex vivo. Fibrosis of the organoid occurred following TGFβ stimulation and engraftment with myelofibrosis but not healthy donor-derived cells, validating this platform as a powerful tool for studies of malignant cells and their interactions within a human bone marrow-like milieu. This enabling technology is likely to accelerate the discovery and prioritization of novel targets for bone marrow disorders and blood cancers., Significance: We present a human bone marrow organoid that supports the growth of primary cells from patients with myeloid and lymphoid blood cancers. This model allows for mechanistic studies of blood cancers in the context of their microenvironment and provides a much-needed ex vivo tool for the prioritization of new therapeutics. See related commentary by Derecka and Crispino, p. 263. This article is highlighted in the In This Issue feature, p. 247., (©2022 The Authors; Published by the American Association for Cancer Research.)

Optical trapping enables the real-time manipulation and observation of morphological evolution of individual particles during reaction chemistry. Here, optical trapping was used in combination with Raman spectroscopy to conduct airborne assembly and kinetic experiments. Micro-droplets of alkoxysilane were levitated in air prior to undergoing either acid- or base-catalyzed sol-gel reaction chemistry to form silica particles. The evolution of the reaction was monitored in real-time; Raman and Mie spectroscopies confirmed the in situ formation of silica particles from alkoxysilane droplets as the product of successive hydrolysis and condensation reactions, with faster reaction kinetics in acid catalysis. Hydrolysis and condensation were accompanied by a reduction in droplet volume and silica formation. Two airborne particles undergoing solidification could be assembled into unique 3D structures such as dumb-bell shapes by manipulating a controlled collision. Our results provide a pipeline combining spectroscopy with optical microscopy and nanoscale FIB-SEM imaging to enable chemical and structural insights, with the opportunity to apply this methodology to probe structure formation during reactive inkjet printing., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Skin has excellent capacity to regenerate, however, in the event of a large injury or burn skin grafts are required to aid wound healing. The regenerative capacity further declines with increasing age and can be further exacerbated with bacterial infection leading to a chronic wound. Engineered skin substitutes can be used to provide a temporary template for the damaged tissue, to prevent/combat bacterial infection and promote healing. In this study, the sol-gel process and electrospinning were combined to fabricate 3D cotton-wool-like sol-gel bioactive glass fibers that mimic the fibrous architecture of skin extracellular matrix (ECM) and deliver metal ions for antibacterial (silver) and therapeutic (calcium and silica species) actions for successful healing of wounds. This study investigated the effects of synthesis and process parameters, in particular sintering temperature on the fiber morphology, the incorporation and distribution of silver and the degradation rate of fibers. Silver nitrate was found to decompose into silver nanoparticles within the glass fibers upon calcination. Furthermore, with increasing calcination temperature the nanoparticles increased in size from 3 nm at 600 °C to ~25 nm at 800 °C. The antibacterial ability of the Ag-doped glass fibers decreased as a function of the glass calcination temperature. The degradation products from the Ag-doped 3D non-woven sol-gel glass fibers were also found to promote fibroblast proliferation thus demonstrating their potential for use in skin regeneration., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We propose a novel image analysis framework to automate analysis of X-ray microtomography images of sintering ceramics and glasses, using open-source toolkits and machine learning. Additive manufacturing (AM) of glasses and ceramics usually requires sintering of green bodies. Sintering causes shrinkage, which presents a challenge for controlling the metrology of the final architecture. Therefore, being able to monitor sintering in 3D over time (termed 4D) is important when developing new porous ceramics or glasses. Synchrotron X-ray tomographic imaging allows in situ, real-time capture of the sintering process at both micro and macro scales using a furnace rig, facilitating 4D quantitative analysis of the process. The proposed image analysis framework is capable of tracking and quantifying the densification of glass or ceramic particles within multiple volumes of interest (VOIs) along with structural changes over time using 4D image data. The framework is demonstrated by 4D quantitative analysis of bioactive glass ICIE16 within a 3D-printed scaffold. Here, densification of glass particles within 3 VOIs were tracked and quantified along with diameter change of struts and interstrut pore size over the 3D image series, delivering new insights on the sintering mechanism of ICIE16 bioactive glass particles in both micro and macro scales., (© 2021 The Authors. Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society.)