Natural hydrogels are promising scaffolds to engineer epidermis. Currently, natural hydrogels used to support epidermal regeneration are mainly collagen- or gelatin-based, which mimic the natural dermal extracellular matrix (ECM) but often suffer from insufficient and uncontrollable mechanical and degradation properties. In this study, a photocrosslinkable gelatin (i.e., gelatin methacrylamide (GelMA)) with tunable mechanical, degradation and biological properties is used to engineer the epidermis for skin tissue engineering applications. The results reveal that the mechanical and degradation properties of the developed hydrogels can be readily modified by varying the hydrogel concentration, with elastic and compressive moduli tuned from a few kPa to a few hundred kPa and the degradation times varied from a few days to several months. Additionally, hydrogels of all concentrations displayed excellent cell viability (>90%) with increasing cell adhesion and proliferation with increase in hydrogel concentrations. Furthermore, the hydrogels are found to support keratinocyte growth, differentiation and stratification into a reconstructed multi-layered epidermis with adequate barrier functions. The robust and tuneable properties of GelMA hydrogels have suggested that the keratinocyte laden hydrogels can be used as epidermal substitutes, wound dressings or substrates to construct various in vitro skin models.

A number of different processing techniques have been developed to design and fabricate three-dimensional (3D) scaffolds for tissue-engineering applications. The imperfection of the current techniques has encouraged the use of a rapid prototyping technology known as fused deposition modeling (FDM). Our results show that FDM allows the design and fabrication of highly reproducible bioresorbable 3D scaffolds with a fully interconnected pore network. The mechanical properties and in vitro biocompatibility of polycaprolactone scaffolds with a porosity of 61 +/- 1% and two matrix architectures were studied. The honeycomb-like pores had a size falling within the range of 360 x 430 x 620 microm. The scaffolds with a 0/60/120 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 41.9 +/- 3.5 and 3.1 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 29.4 +/- 4.0 and 2.3 +/- 0.2 MPa, respectively. In comparison, the scaffolds with a 0/72/144/36/108 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 20.2 +/- 1.7 and 2.4 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 21.5 +/- 2.9 and 2.0 +/- 0.2 MPa, respectively. Statistical analysis confirmed that the five-angle scaffolds had significantly lower stiffness and 1% offset yield strengths under compression loading than those with a three-angle pattern under both testing conditions (p < or = 0.05). The obtained stress-strain curves for both scaffold architectures demonstrate the typical behavior of a honeycomb structure undergoing deformation. In vitro studies were conducted with primary human fibroblasts and periosteal cells. Light, environmental scanning electron, and confocal laser microscopy as well as immunohistochemistry showed cell proliferation and extracellular matrix production on the polycaprolactone surface in the 1st culturing week. Over a period of 3-4 weeks in a culture, the fully interconnected scaffold architecture was completely 3D-filled by cellular tissue. Our cell culture study shows that fibroblasts and osteoblast-like cells can proliferate, differentiate, and produce a cellular tissue in an entirely interconnected 3D polycaprolactone matrix.

No abstract

Communicated by A. Jamie CuticchiaWe describe a revised and expanded database on human intermediate filament proteins, a major component of the eukaryotic cytoskeleton. The family of 70 intermediate filament genes (including those encoding keratins, desmins, and lamins) is now known to be associated with a wide range of diverse diseases, at least 72 distinct human pathologies, including skin blistering, muscular dystrophy, cardiomyopathy, premature aging syndromes, neurodegenerative disorders, and cataract. To date, the database catalogs 1,274 manually-curated pathogenic sequence variants and 170 allelic variants in intermediate filament genes from over 459 peer-reviewed research articles. Unrelated cases were collected from all of the six sequence homology groups and the sequence variations were described at cDNA and protein levels with links to the related diseases and reference articles. The mutations and polymorphisms are presented in parallel with data on protein structure, gene, and chromosomal location and basic information on associated diseases. Detailed statistics relating to the variants records in the database are displayed by homology group, mutation type, affected domain, associated diseases, and nucleic and amino acid substitutions. Multiple sequence alignment algorithms can be run from queries to determine DNA or protein sequence conservation. Literature sources can be interrogated within the database and external links are provided to public databases. The database is freely and publicly accessible online at www.interfil.org (last accessed 13 September 2007). Users can query the database by various keywords and the search results can be downloaded. It is anticipated that the Human Intermediate Filament Database (HIFD) will provide a useful resource to study human genome variations for basic scientists, clinicians, and students alike. Hum Mutat 29(3), [351][352][353][354][355][356][357][358][359][360] 2008.

The use of nanomaterials has raised safety concerns, as their small size facilitates accumulation in and interaction with biological tissues. Here we show that exposure of endothelial cells to TiO 2 nanomaterials causes endothelial cell leakiness. This effect is caused by the physical interaction between TiO 2 nanomaterials and endothelial cells' adherens junction protein VE-cadherin. As a result, VE-cadherin is phosphorylated at intracellular residues (Y658 and Y731), and the interaction between VE-cadherin and p120 as well as b-catenin is lost. The resulting signalling cascade promotes actin remodelling, as well as internalization and degradation of VE-cadherin. We show that injections of TiO 2 nanomaterials cause leakiness of subcutaneous blood vessels in mice and, in a melanoma-lung metastasis mouse model, increase the number of pulmonary metastases. Our findings uncover a novel non-receptor-mediated mechanism by which nanomaterials trigger intracellular signalling cascades via specific interaction with VE-cadherin, resulting in nanomaterial-induced endothelial cell leakiness.

No abstract

Nanosized hydroxyapatite (nHA) has been proposed as drug delivery vehicles because of its biocompatibility. While the possible risks of nHA inducing inflammation have been highlighted, the specific influence of varying nHA particle morphology is still unclear. In order to establish this understanding, nHA of four different shapes--needle (nHA-ND), plate (nHA-PL), sphere (nHA-SP) and rod (nHA-RD)--were synthesized. The particle effects with the concentration of 10-300 μg/mL on cytotoxicity, oxygen species generation, production of inflammatory cytokines (TNF-α and IL-6), particle-cell association and cellular uptake were evaluated on BEAS-2B and RAW264.7 cells. Results show that nHA-ND and nHA-PL induced the most significant cell death in BEAS-2B cultures compared to nHA-SP and nHA-RD. Necrosis-apoptosis assay by FITC Annexin V and propidium iodide (PI) staining revealed loss of the majority of BEAS-2B by necrosis. No significant cell death was recorded in RAW264.7 cultures exposed to any of the nHA groups. Correspondingly, no significant differences were observed in TNF-α level for RAW264.7 cells upon incubation with nHA of different shapes. In addition, nHA-RD exhibited a higher degree of particle-cell association and internalization in both BEAS-2B and RAW264.7 cells, compared to nHA-ND. The phenomena suggested that higher particle-cell association and increased cellular uptake of nHA need not result in increased cytotoxicity, indicating the importance of particle shape on cytotoxicity. Specifically, needle- and plate-shaped nHA induced the most significant cell-specific cytotoxicity and IL-6 expression but showed the least particle-cell association. Taken collectively, we demonstrated the shape-dependent effects of nHA on cytotoxicity, inflammatory cytokine expression and particle-cell association.

Engineered nanomaterials are increasingly added to foods to improve quality, safety, or nutrition. Here we report the ability of ingested nanocellulose (NC) materials to reduce digestion and absorption of ingested fat. In the small intestinal phase of an acellular simulated gastrointestinal tract, the hydrolysis of free fatty acids (FFA) from triglycerides (TG) in a high-fat food model was reduced by 48.4% when NC was added at 0.75% w/w to the food, as quantified by pH stat titration, and by 40.1% as assessed by fluorometric FFA assay. Furthermore, translocation of TG and FFA across an in vitro cellular model of the intestinal epithelium was significantly reduced by the presence of 0.75% w/w NC in the food (TG by 52% and FFA by 32%). Finally, in in vivo experiments, the postprandial rise in serum TG 1 h after gavage with the high fat food model was reduced by 36% when 1.0% w/w NC was administered with the food. Scanning electron microscopy and molecular dynamics studies suggest two primary mechanisms for this effect: (1) coalescence of fat droplets on fibrillar NC (CNF) fibers, resulting in a reduction of available surface area for lipase binding and (2) sequestration of bile salts, causing impaired interfacial displacement of proteins at the lipid droplet surface and impaired solubilization of lipid digestion products. Together these findings suggest a potential use for NC, as a food additive or supplement, to reduce absorption of ingested fat and thereby assist in weight loss and the management of obesity.