Effect of filler surface morphology on the impact behaviour of hydroxyapatite reinforced high density polyethylene composites

The anti-angiogenic role of discoidin domain receptor 2 (DDR2) in laser-induced choroidal neovascularization

Choroidal neovascularization (CNV), an aberrant growth of blood vessels in the choroid layer of the eye, is a major cause of vision loss. In view of our recent finding that discoidin domain receptor 2 (DDR2), a collagen-binding receptor tyrosine kinase, is involved in control of vascular endothelial activity and tumor angiogenesis, the present study aims to investigate whether and how DDR2 affects the pathogenesis of CNV. We initially found that a spontaneous DDR2 mutant mouse colony (slie) exhibited enhanced amplitude of laser-induced CNV. The inhibitory role of DDR2 in CNV development was further confirmed by experiments through intravitreous injection of DDR2 small interference RNA (siRNA) or DDR2-expressing adenovirus. Quantitative real-time polymerase chain reaction (qPCR) and immunoblot analysis showed that DDR2 regulates the expression of several major pro-angiogenic factors in the laser-injured choroid as well as in retinal pigment epithelium (RPE) cells. In addition, it was demonstrated that the CNV-induced increases in the phosphorylation levels of Akt and mTOR were affected by the upregulation or downregulation of DDR2. Thus, the data from this study for the first time revealed that DDR2 negatively regulates the development of experimental CNV in vivo, which may provide a novel target for preventing human pathological ocular neovascularization. Key messages: DDR2 does not affect retinal development. DDR2 inhibits laser-induced CNV. DDR2 regulates angiogenic factor expression in CNV lesion as well as in RPE cells. DDR2 is involved in modulation of CNV-induced activation of PI3K pathway.

Bioactive ceramic-reinforced composites for bone augmentation

Biomaterials have been used to repair the human body for millennia, but it is only since the 1970s that man-made composites have been used. Hydroxyapatite (HA)-reinforced polyethylene (PE) is the first of the 'second-generation' biomaterials that have been developed to be bioactive rather than bioinert. The mechanical properties have been characterized using quasi-static, fatigue, creep and fracture toughness testing, and these studies have allowed optimization of the production method. The in vitro and in vivo biological properties have been investigated with a range of filler content and have shown that the presence of sufficient bioactive filler leads to a bioactive composite. Finally, the material has been applied clinically, initially in the orbital floor and later in the middle ear. From this initial combination of HA in PE other bioactive ceramic polymer composites have been developed.

Nanostructured polymer scaffolds for tissue engineering and regenerative medicine

The structural features of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation and differentiation. The scaffold acts as an interim synthetic extracellular matrix (ECM) that cells interact with prior to forming a new tissue. In this review, bone tissue engineering is used as the primary example for the sake of brevity. We focus on nanofibrous scaffolds and the incorporation of other components including other nanofeatures into the scaffold structure. Since the ECM is comprised in large part of collagen fibers, between 50 and 500 nm in diameter, well-designed nanofibrous scaffolds mimic this structure. Our group has developed a novel thermally induced phase separation (TIPS) process in which a solution of biodegradable polymer is cast into a porous scaffold, resulting in a nanofibrous pore-wall structure. These nanoscale fibers have a diameter (50-500 nm) comparable to those collagen fibers found in the ECM. This process can then be combined with a porogen leaching technique, also developed by our group, to engineer an interconnected pore structure that promotes cell migration and tissue ingrowth in three dimensions. To improve upon efforts to incorporate a ceramic component into polymer scaffolds by mixing, our group has also developed a technique where apatite crystals are grown onto biodegradable polymer scaffolds by soaking them in simulated body fluid (SBF). By changing the polymer used, the concentration of ions in the SBF and by varying the treatment time, the size and distribution of these crystals are varied. Work is currently being done to improve the distribution of these crystals throughout three-dimensional scaffolds and to create nanoscale apatite deposits that better mimic those found in the ECM. In both nanofibrous and composite scaffolds, cell adhesion, proliferation and differentiation improved when compared to control scaffolds. Additionally, composite scaffolds showed a decrease in incidence of apoptosis when compared to polymer control in bone tissue engineering. Nanoparticles have been integrated into the nanostructured scaffolds to deliver biologically active molecules such as growth and differentiation factors to regulate cell behavior for optimal tissue regeneration.