Regression and persistence: remodelling in a tissue engineered axial vascular assembly.

In later stages of vasculoangiogenesis a vascular network is going through a metamorphosis for optimal perfusion and economy of energy. In this study we make a quantitative approach to phenomena of remodelling in a bioartificial neovascular network and suggest variance of calibre as a parameter of neovascular maturation. For this study, 18 male Lewis rats were subjected to the AV loop operation in combination with a hard porous biogenic matrix and an isolation chamber. The animals were allocated into three groups for different explantation intervals set to 2, 4 and 8 weeks, respectively. Collective attributes like vascular density, percent fractional area and variance of calibre were evaluated for a predefined region of interest (ROI). Late morphogenesis was evaluated by means of scanning electron microscopy. After the fourth week the absolute number of vessels within the ROI decreased (P < 0.03) whereas, on the contrary, the fractional area of all segments increased (P < 0.02). The variance in calibre was significantly increased in the 8-week group (P < 0.05). Lymphatic growth after week 4, early pericyte migration as well as intussusceptive angiogenesis were identified immunohistologically. Phenomena of remodelling were evaluated quantitatively in a neovascular network and variance could be proposed as a parameter of net vascular maturation.

Influence of magnesium doping on the phase transformation temperature of beta-TCP ceramics examined by Rietveld refinement.

The influence of Mg doping in Ca(3)(PO(4))(2) on the transformation temperature of beta-tricalcium phosphate (beta-TCP) to alpha-tricalcium phosphate (alpha-TCP) was examined. A maximum substitution by 14 mol% of Mg(2+) on Ca(2+) sites in the beta-TCP structure was determined for powders calcinated at 1025+/-10 degrees C. X-ray powder diffraction analysis (XRPD) in combination with Rietveld method (TOPAS 2.1) was employed for quantitative phase analysis and structural refinement. The synthesized and characterized Mg-doped samples were sintered in air atmosphere in a vertical tube furnace at suitable temperatures ranging from 1460 to 1680 degrees C and subsequently quenched to room temperature, in order to stabilize alpha-TCP. The beta to alpha transformation temperatures were determined by differential temperature analysis and XRPD analysis.

Induction of bone formation in biphasic calcium phosphate scaffolds by bone morphogenetic protein-2 and primary osteoblasts.

Bone tissue engineering strategies mainly depend on porous scaffold materials. In this study, novel biphasic calcium phosphate (BCP) matrices were generated by 3D-printing. High porosity was achieved by starch consolidation. This study aimed to characterise the porous BCP-scaffold properties and interactions of osteogenic cells and growth factors under in vivo conditions. Five differently treated constructs were implanted subcutaneously in syngeneic rats: plain BCP constructs (group A), constructs pre-treated with BMP-2 (group B; 1.6 µg BMP-2 per scaffold), seeded with primary osteoblasts (OB) (group C), seeded with OB and BMP-2 (group D) and constructs seeded with OB and pre-cultivated in a flow bioreactor for 6 weeks (group E). After 2, 4 and 6 weeks, specimens were explanted and subjected to histological and molecular biological analyses. Explanted scaffolds were invaded by fibrovascular tissue without significant foreign body reactions. Morphometric analysis demonstrated significantly increased bone formation in samples from group D (OB + BMP-2) compared to all other groups. Samples from groups B-E displayed significant mRNA expression of bone-specific genes after 6 weeks. Pre-cultivation in the flow bioreactor (group E) induced bone formation comparable with group B. In this study, differences in bone distribution between samples with BMP-2 or osteoblasts could be observed. In conclusion, combination of osteoblasts and BMP-2 synergistically enhanced bone formation in novel ceramic scaffolds. These results provide the basis for further experiments in orthotopic defect models with a focus on future applications in orthopaedic and reconstructive surgery.

The venous graft as an effector of early angiogenesis in a fibrin matrix.

The arteriovenous loop (AV loop) model is gaining importance as a means of initiating and sustaining perfusion in tissue engineering constructs in vivo. This study represents an attempt to dissect the morphology of early arterialization and angiogenesis in the AV loop in a fibrin matrix with special focus on the interpositional venous graft (IVG) segment. An AV loop was constructed in 30 rats using the femoral vessels and an IVG. The AV loop was encased in an isolation chamber filled with a fibrin matrix. Evaluation methods included scanning electron microscopy (SEM) of corrosion casts, immune histology and micro magnetic resonance angiography (MRA). Direct luminal neovascular sprouting was evident between day 10 and day 14 from the vein and the IVG but not from the arterial segment. Arterialization of the IVG manifested itself on the corrosion casts as a gradual reduction in luminal caliber with onset after day 7. Microdissection of the microvascular replicas could demonstrate for the first time the presence of direct luminal sprouts from the IVG. MRA was used to display the shunt pattern of perfusion in the patent AV loop. From the three segments of the vascular axis in the AV loop the IVG is the most versatile for applications in the clinical as well as the experimental setting. Kinetics of angiogenesis warrant further investigation in the IVG.

Sonochemical synthesis of calcium phosphate powders.

beta-tricalcium phosphate (beta-TCP) and biphasic calcium phosphate powders (BCP), consisting of hydroxyapatite (HA) and beta-TCP, were synthesized by thermal decomposition of precursor powders obtained from neutralization method. The precursor powders with a Ca/P molar ratio of 1.5 were prepared by adding an orthophosphoric acid (H(3)PO(4)) solution to an aqueous suspension containing calcium hydroxide (Ca(OH)(2)). Mixing was carried out by vigorous stirring and under sonochemical irradiation at 50 kHz, respectively. Glycerol and D-glucose were added to evaluate their influence on the precipitation of the resulting calcium phosphate powders. After calcination at 1000 degrees C for 3 h BCP nanopowders of various HA/beta-TCP ratio were obtained.

Evaluation of subsurface damage in CAD/CAM machined dental ceramics.

Commercial ceramics for dental computer aided design/computer aided manufacture (CAD/CAM) restorations suffer from surface chipping defects and microcracking. The influence of CAD/CAM machining of dental materials on the mechanical strength and extension of the damage zone was studied. Two different commercial dental ceramics, a feldspathic porcelain and a glass-ceramic, were CAD/CAM machined according to dental practice. The extension of the damage zone was analysed by a stepwise erosion of the surface, and the biaxial flexural strength was measured. To simulate the adhesive fixing of ceramic inlays, the specimens were sealed using a light-curing monomer. The different machining behaviour is dominated by the microstructure of the investigated materials. Owing to the high amount of glassy phase, the feldspathic porcelain shows extensive microcracking and chipping defects. The extent of the damage zone can be determined as 40-60 microm. Sealing of the surface did not affect the flexural strength of the machined samples. The dominating response to machining of the glass-ceramic is crushing and crumbling with a major contribution of plastic deformation on a microscopic scale. The extent of the damage zone is less than 20 microm. These cracks can be bridged by sealing of the surface, resulting in a substantial increase in strength.

[Evaluation of the treatment of aneurysmal meningeal hemorrhage with antifibrinolytic agents, calcium inhibitors and maintenance of effective blood volume]. / Bilan du traitement des hémorragies méningées anévrysmales par antifibrinolytique, inhibiteur calcique et maintien d'une volémie efficace.

To prevent and treat the ischemic complications due to the vasospasm, this report suggest the management of aneurysmal subarachnoid haemorrhage by the association of antifibrinolytics (tranexamic acid) to lower the risk of rebleeding, calcium channel blockers (nimodipine), and the keeping of an effective total blood volume (thanks to volume expansion and dopamine). From 88 patients aged from 4 to 73, two thirds were admitted at latest 48 h after the aneurysmal rupture Emergency surgery was carried out in the case of a compressive hematoma, early surgery (between the first and the third day) on the grades I, II and III of Hunt and Hess without any signs of angiographic vasospasms (40% of this series), delayed surgery for the others (27.5%), 10% didn't undergo any surgery. Only three patients (3.4%) presented rebleeding leading to death. The features of the whole series are: 51% recovered without any after effects, 22% had mild neurological deficiency, 10% had severe neurological deficiency and 17% died after their release from hospital. This protocol allowed a decrease in the ischemic complications due to the vasospasm and in the rate of rebleeding during the waiting interval when an angiographic or a clinical vasospasm allowed no surgery.