Macrophages and nociceptor neurons form a sentinel unit around fenestrated capillaries to defend the synovium from circulating immune challenge.

A wide variety of systemic pathologies, including infectious and autoimmune diseases, are accompanied by joint pain or inflammation, often mediated by circulating immune complexes (ICs). How such stimuli access joints and trigger inflammation is unclear. Whole-mount synovial imaging revealed PV1 fenestrated capillaries at the periphery of the synovium in the lining-sublining interface.

The Effects of Chronological Age on the Chondrogenic Potential of Mesenchymal Stromal Cells: A Systematic Review.

Tissue engineering and cell therapy for regenerative medicine have great potential to treat chronic disorders. In musculoskeletal disorders, mesenchymal stromal cells (MSCs) have been identified as a relevant cell type in cell and regenerative strategies due to their multi-lineage potential, although this is likely to be a result of their trophic and immunomodulatory effects on other cells. This PRISMA systematic review aims to assess whether the age of the patient influences the chondrogenic potential of MSCs in regenerative therapy.

Mechanical-Stress-Related Epigenetic Regulation of Transcription Factor in the Etiology of Postmenopausal Osteoporosis.

Mechanical loading exerts a profound influence on bone density and architecture, but the exact mechanism is unknown. Our study shows that expression of the neurological transcriptional factor zinc finger of the cerebellum 1 () is markedly increased in trabecular bone biopsies in the lumbar spine compared with the iliac crest, skeletal sites of high and low mechanical stress, respectively. Human trabecular bone transcriptome analyses revealed a strong association between mRNA levels and gene transcripts characteristically associated with osteoblasts, osteocytes and osteoclasts.

Co-localisation of intra-nuclear membrane type-1 matrix metalloproteinase and hypoxia inducible factor-2α in osteosarcoma and prostate carcinoma cells.

Increased membrane type-1 matrix metalloproteinase (MT1-MMP) expression in osteosarcoma is predictive of poor prognosis and directs bone metastasis in prostate carcinoma. MT1-MMP subcellular localisation varies with oxygen tension, and, therefore, the aim of the present study was to assess protein interactions between MT1-MMP and the hypoxia inducible factors (HIF-1α and HIF-2α). MT1-MMP protein expression was investigated across a panel of cancer cell lines, including a positive and negative control.

Albumin-Enriched Fibrin Hydrogel Embedded in Active Ferromagnetic Networks Improves Osteoblast Differentiation and Vascular Self-Organisation.

Porous coatings on prosthetic implants encourage implant fixation. Enhanced fixation may be achieved using a magneto-active porous coating that can deform elastically in vivo on the application of an external magnetic field, straining in-growing bone. Such a coating, made of 444 ferritic stainless steel fibres, was previously characterised in terms of its mechanical and cellular responses.

Stimulation of Human Osteoblast Differentiation in Magneto-Mechanically Actuated Ferromagnetic Fiber Networks.

There is currently an interest in "active" implantable biomedical devices that include mechanical stimulation as an integral part of their design. This paper reports the experimental use of a porous scaffold made of interconnected networks of slender ferromagnetic fibers that can be actuated in vivo by an external magnetic field applying strains to in-growing cells. Such scaffolds have been previously characterized in terms of their mechanical and cellular responses.

Engineered mosaic protein polymers; a simple route to multifunctional biomaterials.

Background: Engineered living materials (ELMs) are an exciting new frontier, where living organisms create highly functional materials. In particular, protein ELMs have the advantage that their properties can be manipulated via simple molecular biology. Caf1 is a protein ELM that is especially attractive as a biomaterial on account of its unique combination of properties: bacterial cells export it as a massive, modular, non-covalent polymer which is resistant to thermal and chemical degradation and free from animal material.

Multi-length scale bioprinting towards simulating microenvironmental cues.

It is envisaged that the creation of cellular environments at multiple length scales, that recapitulate in vivo bioactive and structural roles, may hold the key to creating functional, complex tissues in the laboratory. This review considers recent advances in biofabrication and bioprinting techniques across different length scales. Particular focus is placed on 3D printing of hydrogels and fabrication of biomaterial fibres that could extend the feature resolution and material functionality of soft tissue constructs.

miR-324-5p is up regulated in end-stage osteoarthritis and regulates Indian Hedgehog signalling by differing mechanisms in human and mouse.

The Hedgehog (Hh) signalling pathway plays important roles during embryonic development and in adult tissue homeostasis, for example cartilage, where its deregulation can lead to osteoarthritis (OA). microRNAs (miRNAs) are important regulators of gene expression, and have been implicated in the regulation of signalling pathways, including Hh, thereby impacting upon development and disease. Our aim was to identify the function of miRNAs whose expression is altered in OA cartilage.

How cell culture conditions affect the microstructure and nanomechanical properties of extracellular matrix formed by immortalized human mesenchymal stem cells: An experimental and modelling study.

This paper presents an investigation of how different culture media (i.e. basal and osteogenic media) affect the nanomechanical properties and microstructure of the mineralized matrix produced by the human mesenchymal stem cell line Y201, from both an experimental and theoretical approach.

Novel bioglasses for bone tissue repair and regeneration: Effect of glass design on sintering ability, ion release and biocompatibility.

Eight novel silicate, phosphate and borate glass compositions (coded as NCLx, where x = 1 to 8), containing different oxides ( MgO, MnO, AlO, CaF, FeO, ZnO, CuO, CrO) were designed and evaluated alongside apatite-wollastonite (used as comparison material), as potential biomaterials for bone tissue repair and regeneration. Glass frits of all the formulations were processed to have particle sizes under 53 μm, with their morphology and dimensions subsequently investigated by scanning electron microscopy (SEM). In order to establish the nature of the raw glass powders, X-ray diffraction (XRD) analysis was also performed.

Three-dimensional printing of porous load-bearing bioceramic scaffolds.

This article reports on the use of the binder jetting three-dimensional printing process combined with sintering to process bioceramic materials to form micro- and macroporous three-dimensional structures. Three different glass-ceramic formulations, apatite-wollastonite and two silicate-based glasses, have been processed using this route to create porous structures which have Young's modulus equivalent to cortical bone and average bending strengths in the range 24-36 MPa. It is demonstrated that a range of macroporous geometries can be created with accuracies of ±0.

Impact of Collagen/Heparin Multilayers for Regulating Bone Cellular Functions.

Bone cell interaction with extracellular matrix (ECM) microenvironment is of critical importance when engineering surface interfaces for bone regeneration. In this work layer-by-layer films of type I collagen (coll), the major constituent of bone ECM, and heparin (hep), a glycosaminoglycan, were assembled on poly(l-lactic acid) (PLLA) substrates to evaluate the impact of the biomacromolecular coating on cell activity. The surface modification of PLLA demonstrated that the hep/coll multilayer is stable after 10 bilayers (confirmed by contact angle, infrared spectroscopy, and morphological analysis).

Reversible non-stick behaviour of a bacterial protein polymer provides a tuneable molecular mimic for cell and tissue engineering.

Yersina pestis, the bubonic plague bacterium, is coated with a polymeric protein hydrogel for protection from host defences. The protein, which is robust and non-stick, resembles structures found in many eukaryotic extracellular-matrix proteins. Cells grown on the natural polymer cannot adhere and grow poorly; however, when cell-adhesion motifs are inserted into the protein, the cells proliferate.

Microporous "honeycomb" films support enhanced bone formation in vitro.

Substrate topography influences cell adhesion, proliferation, and differentiation. In this study, poly (ε-caprolactone) (PCL) films with a well-defined honeycomb structure of porosity 3-4, 5-6, 10-11, or 15-16 μm were contrasted with flat surfaces for their ability to support primary rat osteoblast adhesion and mineralized extracellular matrix deposition in vitro. Immunofluorescent visualization of vinculin and rhodamine phalloidin binding of actin were used to investigate cell adhesion and morphology.

Real-time activity bioassay of single osteoclasts using a silicon nanocrystal-impregnated artificial matrix.

The lack of an in vitro real-time osteoclast (OC) activity assay has hampered mechanistic studies of bone resorption. Such an assay is developed, employing a hydroxyapatite matrix impregnated with alkyl-capped silicon nanocrystals, which is capable of monitoring the time-course of resorption by single osteoclasts. Resorption of the matrix by OC releases the nanocrystals, which are internalized by the cell and detected as an increase in OC luminescence.

Controlled spatial and conformational display of immobilised bone morphogenetic protein-2 and osteopontin signalling motifs regulates osteoblast adhesion and differentiation in vitro.

Background: The interfacial molecular mechanisms that regulate mammalian cell growth and differentiation have important implications for biotechnology (production of cells and cell products) and medicine (tissue engineering, prosthetic implants, cancer and developmental biology). We demonstrate here that engineered protein motifs can be robustly displayed to mammalian cells in vitro in a highly controlled manner using a soluble protein scaffold designed to self assemble on a gold surface.

Results: A protein was engineered to contain a C-terminal cysteine that would allow chemisorption to gold, followed by 12 amino acids that form a water soluble coil that could switch to a hydrophobic helix in the presence of alkane thiols.

Zic1 transcription factor in bone: neural developmental protein regulates mechanotransduction in osteocytes.

A transcriptome analysis compared gene expression in human bone biopsy samples taken from lumbar spine and iliac crest, sites that experience high and low levels of mechanical stress, respectively. The analysis revealed that the zinc finger protein of cerebellum (Zic) family member transcription factor Zic1 was the most up-regulated gene in the lumbar spine (202-fold; P<10(-7)) in comparison with the iliac crest. Software analysis of differential gene expression in the biopsy samples identified the ciliary-related proteins PATCH1 and GLI-Kruppel family members Gli1 and Gli3 as part of a potential molecular network associated with Zic1.

A novel in vitro model to investigate behavior of articular chondrocytes in osteoarthritis.

Objective: To investigate in vivo simulation of the microenvironment in which osteoarthritis (OA) chondrocytes are cultured in vitro.

Methods: Human articular chondrocytes were cultured under normoxic and hypoxic conditions. Cells were cultured on standard culture plastic or a porous polyHEMA surface that closely resembles the in vivo cartilage microarchitecture.

Microfabricated grooved substrates influence cell-cell communication and osteoblast differentiation in vitro.

Implant topography influences osteointegration, but the architectural parameters that dictate cell behavior and the molecular mechanisms remain unclear. Polycarbonate grooved substrates 10, 15, or 30 microm wide and 7 microm deep with an inter-groove distance of 2 microm were contrasted for their ability to influence osteoblasts in vitro. Osteoblasts grew well on the substrates and became alkaline phosphatase-positive under osteogenic conditions, although extensive mineralization of bone-like nodules was only observed on flat surfaces.

A generic expression system to produce proteins that co-assemble with alkane thiol SAM.

Surface biology aims to observe and control biological processes by combining bio-, surface, and physical chemistry. Self-assembled monolayers (SAM) on gold surfaces have provided excellent methods for nanoscale surface preparation for such studies. However, extension of this work requires the specific immobilization of whole protein domains and the direct incorporation of recombinant proteins into SAM is still problematic.

ASARM-truncated MEPE and AC-100 enhance osteogenesis by promoting osteoprogenitor adhesion.

Matrix extracellular phosphoglycoprotein (MEPE) is a member of the SIBLING (Small Integrin-Binding Ligand, N-linked Glycoprotein) family of secreted glycophosphoproteins. Several previous studies have demonstrated that MEPE and its peptide motif, AC-100, may regulate bone mass and influence osteoblast activity, suggesting its potential for inclusion in novel therapeutic strategies aimed at increasing osteogenesis. Our study uses in vitro approaches to assess how adhesion of nonadherent cells is influenced by MEPE and whether response to MEPE is dependent on the maturity of osteoblastic cells.

ADAMTS-1 increases the three-dimensional growth of osteoblasts through type I collagen processing.

The multi-domain neutral endopeptidase, ADAMTS-1 (a disintegrin and metalloprotease with thrombospondin repeats) is induced by parathyroid hormone (PTH) in rat osteoblasts and has therefore been suggested to be involved in initiation of bone remodeling. However, its function(s) in bone cells have not been studied. Here, we first establish that ADAMTS-1 protein is rapidly and transiently produced by human primary osteoblasts in response to PTH (1-34).

Purification of an insect derived recombinant human ADAMTS-1 reveals novel gelatin (type I collagen) degrading activities.

ADAMTS-1 (A Disintegrin And Metalloprotease with ThromboSpondin repeats) is a member of a family of secreted proteolytic enzymes with a complex modular structure. These enzymes are characterised by an N-terminal metalloproteinase domain, a disintegrin-like domain and a carboxyl terminal region containing variable numbers of a repeat sequence with homology to thrombospondin-1. The expression of the gene for ADAMTS-1 has been associated with inflammation, ovulation, angiogenesis, cellular proliferation and bone formation.

The enhancement of osteoblast growth and differentiation in vitro on a peptide hydrogel-polyHIPE polymer hybrid material.

The objective of this study was to investigate the effect of combining two biomaterials on osteoblast proliferation, differentiation and mineralised matrix formation in vitro. The first biomaterial has a well-defined architecture and is known as PolyHIPE polymer (PHP). The second biomaterial is a biologically inspired self-assembling peptide hydrogel (RAD16-I, also called PuraMatrix) that produces a nanoscale environment similar to native extracellular matrix (ECM).