James Dixon

University of Nottingham | Notts · Wolfson Centre for Stem Cells, Tissue Engineering and Modelling (STEM)

Background Low back pain (LBP) is predominantly caused by degeneration of the intervertebral disc (IVD) and central nucleus pulposus (NP) region. Conservative treatments fail to restore disc function, motivating the exploration of nucleic acid therapies, such as the use of microRNAs (miRNAs). miRNAs have the potential to modulate expression of disc...

Background/Objectives: Peptide-based treatments represent an expanding area and require innovative approaches to enhance bioavailability. Combination with cell-penetrating peptides (CPPs) is an attractive strategy to improve non-invasive delivery across nasal epithelial barriers for systemic and direct nose-to-brain transport. We previously develop...

Back pain is a global epidemiological and socioeconomic problem affecting up to 80% of people at some stage during their life and is often due to degeneration of the intervertebral disc (IVD). Therapies aimed at restoring the intradiscal space have predominantly focused on delivery of biomaterials, cells, or growth factors, among others, with varia...

Transfection, defined as functional delivery of cell-internalized nucleic acids, is dependent on many factors linked to formulation, vector, cell type, and microenvironmental culture conditions. We previously developed a technology termed glycosaminoglycan (GAG)-binding enhanced transduction (GET) to efficiently deliver a variety of cargoes intrace...

Pluripotency defines the unlimited potential of individual cells of vertebrate embryos, from which all adult somatic cells and germ cells are derived. Understanding how the programming of pluripotency evolved has been obscured in part by a lack of data from lower vertebrates; in model systems such as frogs and zebrafish, the function of the pluripo...

Insulin regulates blood glucose levels, and is the mainstay for the treatment of type-1 diabetes and type-2 when other drugs provide inadequate control. Therefore, effective oral Insulin delivery would be a significant advance in drug delivery. Herein, we report the use of the modified cell penetrating peptide (CPP) platform, Glycosaminoglycan-(GAG...

Insulin regulates blood glucose levels, and is the mainstay for the treatment of type-1 diabetes and type-2 when other drugs provide inadequate control. Therefore, effective oral Insulin delivery would be a significant advance in drug delivery. Herein, we report the use of the modified cell penetrating peptide (CPP) platform, Glycosaminoglycan-(GAG...

The development of treatments to restore damaged cartilage that can provide functional recovery with minimal risk of revision surgery remains an unmet clinical need. Gene therapy shows increased promise as an innovative solution for enhanced tissue repair. Within this study a novel microRNA (miR)‐activated scaffold is developed for enhanced mesench...

Nanotechnologies are being increasing applied as systems for peptide and nucleic acid macromolecule drug delivery. However systemic targeting of these, or efficient topical and localized delivery remains an issue. A controlled release system that can be patterned and locally administered such as topically to accessible tissue (skin, eye, intestine)...

Pluripotency defines the unlimited potential of cells in the primitive ectoderm of vertebrate embryos, from which all adult somatic cells and germ cells are derived. Understanding how the programing of pluripotency evolved has been obscured by the study of early development in models from lower vertebrates in which pluripotency is not conserved. He...

Non-viral gene delivery has become a popular approach in tissue engineering, as it permits the transient delivery of a therapeutic gene, in order to stimulate tissue repair. However, the efficacy of non-viral delivery vectors remains an issue. Our lab has created gene-activated scaffolds by incorporating various non-viral delivery vectors, includin...

The efficacy of vaccines targeting SARS-CoV-2 is becoming apparent now that the mRNA and adenovirus vector vaccines that have been approved for emergency use are showing promise. However, the longevity of the protective immune response and its efficacy against emerging variants remains to be determined. To improve longevity and future protection ag...

Chondrogenic progenitor cells (CPCs) may be used as an alternative source of cells with potentially superior chondrogenic potential compared to mesenchymal stem cells (MSCs), and could be exploited for future regenerative therapies targeting articular cartilage in degenerative diseases such as osteoarthritis (OA). In this study, we hypothesised tha...

Non-viral delivery systems are generally of low efficiency, which limits their use in gene therapy and editing applications. We previously developed a technology termed glycosaminoglycan (GAG)-binding enhanced transduction (GET) to efficiently deliver a variety of cargos intracellularly; our system employs GAG-binding peptides, which promote cell t...

Chondrogenic progenitor cells (CPCs) may be used as an alternative source of cells with potentially superior chondrogenic potential compared to mesenchymal stem cells (MSCs), and could be exploited for future regenerative therapies targeting articular cartilage in degenerative diseases such as osteoarthritis (OA). In this study, we hypothesised tha...

Nanoparticles (NPs) are increasingly being developed as biomedical platforms for drug/nucleic acid delivery and imaging. However, in biological fluids, NPs interact with a wide range of proteins that form a coating known as protein corona. Coronae can critically influence self‐interaction and binding of other molecules, which can affect toxicity, p...

Developing non-viral gene therapy vectors that both protect and functionally deliver nucleic acid cargoes will be vital if gene augmentation and editing strategies are to be effectively combined with advanced regenerative medicine approaches. Currently such methodologies utilize high concentrations of recombinant growth factors, which result in tox...

Additive manufacturing processes used to create regenerative bone tissue engineered implants are not biocompatible, thereby restricting direct use with stem cells and usually require cell seeding post-fabrication. Combined delivery of stem cells with the controlled release of osteogenic factors, within a mechanically-strong biomaterial combined dur...

Combating necrosis, by supplying nutrients and removing waste, presents the major challenge for engineering large three-dimensional (3D) tissues. Previous elegant work used 3D printing with carbohydrate glass as a cytocompatible sacrificial template to create complex engineered tissues with vascular networks (Miller et al. 2012, Nature Materials)....

Deficient bone vasculature is a key component in pathological conditions ranging from developmental skeletal abnormalities to impaired bone repair. Vascularisation is dependent upon vascular endothelial growth factor (VEGF), which drives both angiogenesis and osteogenesis. The aim of this study was to examine the efficacy of blood vessel and bone f...

The complement of cell surface proteins, collectively referred to as the surfaceome, is a useful indicator of normal differentiation processes, and the development of pathologies such as osteoarthritis (OA). We employed biochemical and proteomic tools to explore the surfaceome and to define biomarkers in chondrogenic progenitor cells (CPC) derived...

Trans-plasma membrane electron transfer (tMPET) is a process by which reducing equivalents, either electrons or reductants like ascorbic acid, are exported to the extracellular environment by the cell. TPMET is involved in a number of physiological process and has been hypothesised to play a role in the redox regulation of cancer metabolism. Here,...

The complement of cell surface proteins, collectively referred to as the surfaceome, is a useful indicator of normal differentiation processes, and the development of pathologies such as osteoarthritis (OA). We employed biochemical and proteomic tools to explore the surfaceome and to define biomarkers in chondrogenic progenitor cells (CPC) derived...

Background Osteochondral injuries represent a significant clinical problem requiring novel cell-based therapies to restore function of the damaged joint with the use of mesenchymal stromal cells (MSCs) leading research efforts. Pre-clinical studies are fundamental in translating such therapies; however, technologies to minimally invasively assess i...

Ubiquitin specific proteases (USPs) reverse ubiquitination and regulate virtually all cellular processes. Defined non-catalytic domains in USP4 and USP15 are known to interact with E3 ligases and substrate recruitment factors. No such interactions have been reported for these domains in the paralog USP11, a key regulator of DNA double-strand break...

The lung remains an attractive target for the gene therapy of monogenetic diseases such as cystic fibrosis (CF). Despite over 27 clinical trials, there are still very few gene therapy vectors that have shown any improvement in lung function; highlighting the need to develop formulations with improved gene transfer potency and the desirable physioch...

Oral delivery of insulin and other anti-diabetic peptides is inhibited by low intestinal absorption caused by the poor permeability across cellular membranes and the susceptibility to enzymatic degradation in the gastrointestinal tract. Cell-penetrating peptides (CPPs) have been investigated for a number of years as oral absorption enhancers for hy...

Upper Critical Solution Temperature (UCST)-type thermally responsive polypeptides (TRPs) with phase transition temperatures around 37 °C in phosphate-buffered saline (PBS) buffer (pH 7.4, 100 mM) were prepared from poly(l-ornithine) hydrobromide and coated on non-tissue culture-treated plastic plates (nTCP). Cell adhesion was observed at temperatur...

Mesenchymal stem cells (MSCs) are being exploited in regenerative medicine due to their tri-lineage differentiation and immunomodulation activity. Currently, there are two major challenges when directing the differentiation of MSCs for therapeutic applications. First, chemical and growth factor strategies to direct osteogenesis in vivo lack specifi...

Statement of significance: The goal for regenerative medicine is to restore functional biological tissue by controlling and augmenting cellular behavior. Either Transcription (TFs) or growth factors (GFs) can be presented to cells in spatio-temporal gradients for programming cell fate and gene expression. Here, we have created a sustained and cont...

Unlabelled: Fundamental behaviour such as cell fate, growth and death are mediated through the control of key genetic transcriptional regulators. These regulators are activated or repressed by the integration of multiple signalling molecules in spatio-temporal gradients. Engineering these gradients is complex but considered key in controlling tiss...

INTRODUCTION: Local neurosurgically-applied drug-delivery systems offer an opportunity to target glioblastoma (GBM) residual disease, but consideration must be given to the uptake of delivered agents once diffused from a drug-delivery depot. We assess the glycosaminoglycan-binding enhanced transduction of nanoparticles coated with genetically-engin...

Significance Efficient delivery of therapeutic molecules inside cells by nontransgenic approaches is key as gene editing/correction, directed differentiation, and in vivo cell modulation/tracking are translated for regenerative medicine applications. Here we describe a peptide-based system engineered to enhance the activity of cell-penetrating pept...

The use of materials to impose tissue-like architecture at cell resolution will be important if engineered functional replacements for damaged cardiovascular, pulmonary, renal or digestive tissues are to be authentically engineered. Here, we demonstrate a coordinated system for the fabrication and subsequent culture of tubular tissues composed of m...

A dual thermoresponsive and magnetic colloidal gel matrix is described for enhanced stem-cell culture. The combined properties of the material allow enzyme-free passaging and expansion of mesenchymal stem cells, as well as isolation of cells postculture by the simple process of lowering the temperature and applying an external magnetic field. The c...

Methodologies to deliver cargo proteins directly into cells are useful tools to elicit changes in cell behaviour and direct stem cell differentiation and self-renewal. Cellular processes such as proliferation, angiogenesis and differentiation are guided and regulated by gradients of different physical and chemical cues . The ability to control the...

5-Methylcytosine (5mC) is an epigenetic modification involved in regulation of gene activity during differentiation. Tet dioxygenases oxidize 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). Both 5fC and 5caC can be excised from DNA by thymine-DNA glycosylase (TDG) followed by regeneration of unmodified...

Electrospinning is a common technique used to fabricate fibrous scaffolds for tissue engineering applications. There is now growing interest in assessing the ability of collector plate design to influence the patterning of the fibres during the electrospinning process. In this study, we investigate a novel method to generate hybrid electrospun scaf...

Significance Stem-cell microenvironment has been identified as an important modulator of plasticity, self-renewal, and differentiation. This work details the development of a hydrogel system tailored to promote human pluripotent stem cell (HPSC) self-renewal with a simple chemical microenvironmental switch to direct differentiation. Furthermore, th...

Reduction in motor neuron axon growth is observed in Ark2C−/− embryos. (A) Confocal image of whole-mount IF with anti-GFP showing forelimb nerves measured in E11.5 HB9-eGFP transgenic embryos. Proximal limb to the left; a, axillary nerve; r, radial nerve; m, median nerve; u, ulnar nerve; t, thoracodorsal; C5–8 and T1, spinal nerves from appropriate...

Motor neuron specification is normal in the absence of Ark2C expression. (A) Diagram summarizing molecular marker expression of motor pools innervating the forelimb and diaphragm. LMC, lateral motor column; MMC, medial motor column [76]. (B) Confocal images from brachial spinal cord cryostat sections stained with IF motor pool marker Pea3 and FoxP1...

Early expression of the novel Arkadia-like gene, Ark2C. (A) Ideogram showing significant alignments of the mouse Arkadia cDNA sequence (blue arrow) in the mouse genome using BLAST. Two alignments on chromosome 3 (green arrows) are Arkadia-like pseudogenes. Ark2 (red arrow) is located on chromosome 18. (B) Whole-mount in situ hybridization with Ark2...

Ark2C interacts with components of the BMP pathway but not with pSmad2/3. (A) IP in 293T-GArk2C cells after 1 h treatment with SB 431542 (SB), an inhibitor of the TGF-β/Activin pathway, or Activin showing no interaction of GArk2C with pSmad2. TL, total lysate; IB, immunoblot; *, nonspecific band. (B) Confocal images taken from Proximity Ligation As...

Wild-type forelimb motor innervation. Movie generated from confocal images of whole-mount IF with anti-GFP showing forelimb innervation at E13.5 in a wt HB9-eGFP transgenic embryo projected in 3D rotating around the proximal-distal axis. (MPEG)

Ark2C-null forelimb motor innervation. Movie generated from confocal images of whole-mount IF with anti-GFP showing forelimb innervation at E13.5 in an Ark2C−/− HB9-eGFP transgenic embryo projected in 3D rotating around the proximal–distal axis. (MP4)

Ark2C enhances the phosphorylation of Smad1/5/8 and degradation of negative regulators of the pathway during treatment with BMP4. (A–B) IB showing pSmad1/5/8 in 293T cells transfected with FLAG-Ark2N or FLAG-Ark2C and treated as indicated. Protein levels of pSmad1/5/8 were quantified, normalized to PCNA, and the relative protein levels are shown in...

BMP ligands are expressed in the periphery where innervation defects are observed in the absence of Ark2C. (A) Semiquantitative RT-PCR showing expression of BMP2, 4, 6, and 7 in diaphragms from four individual E15.5 embryos. At this developmental stage the phrenic nerve has entered the muscle and is forming terminal branches. (B) In situ hybridizat...

Innervation defects are observed in Ark2C+/−Smad8−/− dorsal forelimb. (A) Schematic representation of the major phenotypes seen in Ark2C+/−Smad8−/− embryos at E13.5. Using the same key for the partition of the radial nerve and the corresponding muscle groups that they innervate as shown in Figure 4F: Blue (1) and red (2) arrows show branches innerv...

Quantitative PCR primers. Sequences of primers used in all quantitative and semiquantitative RT-PCR. (TIF)

NSC-34 express Ark2C and MN marker. (A) QPCR showing expression of exon7–8 of Ark2C (including RING domain) in NSC-34 cells in 10% and 1% FBS. Expression of Ark2C in wt and Ark2C−/− in early embryonic brain was used as controls. Error bars represent ±SD. (B) IF showing Isl1 expression (red) in NSC-34 but not in mouse embryonic fibroblasts (MEF). Sc...

Survival rates of offspring from genetic interactions with Ark2C. (A) Ark2C+/−:BmprII+/−×Ark2C+/− cross and (B) Ark2C+/−:Smad8+/−×Ark2C+/−:Smad8+/− cross. Tables show expected percentage of total births (according to Mendelian ratios) for each genotype, the actual percentage of total births observed (all animals alive less than 24 h after birth), a...

Little is known about extrinsic signals required for the advancement of motor neuron (MN) axons, which extend over long distances in the periphery to form precise connections with target muscles. Here we present that Rnf165 (Arkadia-like; Arkadia2; Ark2C) is expressed specifically in the nervous system and that its loss in mice causes motor innerva...

AimsLong-QT syndromes (LQTS) are mostly autosomal-dominant congenital disorders associated with a 1:1000 mutation frequency, cardiac arrest, and sudden death. We sought to use cardiomyocytes derived from human-induced pluripotency stem cells (hiPSCs) as an in vitro model to develop and evaluate gene-based therapeutics for the treatment of LQTS.Meth...

Many cell therapy approaches aim to deliver high-density single-cell suspensions to diseased or injured sites in the body. Long term clinical success will in part be dependent on the cells that remain viable and that assume correct functionality post-administration. The research presented in this paper focuses on the potential of cell aggregate del...

Tissue function during development and in regenerative medicine completely relies on correct cell organization and patterning at micro and macro scales. We describe a rapid method for patterning mammalian cells including human embryonic stem cells (HESCs) and induced pluripotent stem cells (iPSCs) on elastomeric membranes such that micron-scale con...

The limited ability of the heart to regenerate has prompted development of new systems to produce cardiomyocytes for therapeutics. While differentiation of human embryonic stem cells (hESCs) into cardiomyocytes has been well documented, the process remains inefficient and/or expensive, and progress would be facilitated by better understanding the e...

Breast cancer is a disease characterised by both genetic and epigenetic alterations. Epigenetic silencing of tumour suppressor genes is an early event in breast carcinogenesis and reversion of gene silencing by epigenetic reprogramming can provide clues to the mechanisms responsible for tumour initiation and progression. In this study we apply the...