Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100–150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.</p

Incorporating strontium enriched amorphous calcium phosphate granules in collagen/collagen-magnesium-hydroxyapatite osteochondral scaffolds improves subchondral bone repair

Osteochondral defect repair with a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold has demonstrated good clinical results. However, subchondral bone repair remained suboptimal, potentially leading to damage to the regenerated overlying neocartilage. This study aimed to improve the bone repair potential of this scaffold by incorporating newly developed strontium (Sr) ion enriched amorphous calcium phosphate (Sr-ACP) granules (100–150 μm). Sr concentration of Sr-ACP was determined with ICP-MS at 2.49 ± 0.04 wt%. Then 30 wt% ACP or Sr-ACP granules were integrated into the scaffold prototypes. The ACP or Sr-ACP granules were well embedded and distributed in the collagen matrix demonstrated by micro-CT and scanning electron microscopy/energy dispersive x-ray spectrometry. Good cytocompatibility of ACP/Sr-ACP granules and ACP/Sr-ACP enriched scaffolds was confirmed with in vitro cytotoxicity assays. An overall promising early tissue response and good biocompatibility of ACP and Sr-ACP enriched scaffolds were demonstrated in a subcutaneous mouse model. In a goat osteochondral defect model, significantly more bone was observed at 6 months with the treatment of Sr-ACP enriched scaffolds compared to scaffold-only, in particular in the weight-bearing femoral condyle subchondral bone defect. Overall, the incorporation of osteogenic Sr-ACP granules in Col/Col-Mg-HAp scaffolds showed to be a feasible and promising strategy to improve subchondral bone repair.</p

Sacrifice ratio dispersion within the Euro Zone: what can be learned about implementing a single monetary policy?

This article focuses on the comparison of sacrifice ratios as an indicator for structural dispersion within the euro area over the period 1972–2003. Estimates of the sacrifice ratio, defined as the cumulative output cost arising from permanent inflation reduction, are obtained using structural VAR models. Results from sub‐period analysis as well as 10‐year‐period rolling estimates lead to two main conclusions. First, empirical evidence displays a recent increase in the average sacrifice ratio, which can be linked to the simultaneous decrease in the average inflation rate: this negative relationship between the initial level of inflation and the cost of disinflation can be seen as a justification for the choice of an inflation objective close to 2% for the European Central Bank (ECB) rather than a target of perfect price stability, potentially very damaging. Second, we cannot provide evidence of any reduction in European sacrifice ratio dispersion, which would suggest that the nominal convergence triggered by the Maastricht Treaty did not involve a true reduction of structural differences. It is likely to be a problem in the stance of a single monetary policy, because structural differences imply asymmetric responses of real national economies to the same monetary impulse.sacrifice ratio, monetary policy, convergence, Economic and Monetary Union (EMU), C22, E32, E52, E58,

Modelling interest rate volatility: Regime switches and level links

C22, C52,

DO THE PHASES OF THE BUSINESS CYCLE DIE OF OLD AGE?

The paper re-examines the issue of duration dependence in the Australian classical and growth business cycles in light of the somewhat surprising results obtained recently by Cashin and Ouliaris (2004). In so doing the authors use the multinomial logit regime switching modelling approach of Layton and Smith (2003). The paper also represents an extension of the earlier work on the issue undertaken by Bodman (1998); the key extensions being that the issue is framed within an explicit established business cycle chronology, a leading index is also included within the analysis, and the growth cycle, in addition to the classical cycle, is considered. Strong evidence of duration dependence is found for periods of recession within the classical cycle and for both phases of the growth cycle. Moderate evidence of duration dependency is also found for periods of classical cycle expansion. However, the evidence in this regard is significantly reduced once movements in the leading index are included in the analysis with its movements exhibiting strong power in predicting the termination of classical business cycle expansions. For growth cycles, duration dependence symmetry is found across both phases of the cycle. Copyright Blackwell Publishing Ltd/University of Adelaide and Flinders University 2005..

Effectiveness of BMP-2 and PDGF-BB Adsorption onto a Collagen/Collagen-Magnesium-Hydroxyapatite Scaffold in Weight-Bearing and Non-Weight-Bearing Osteochondral Defect Bone Repair: In Vitro, Ex Vivo and In Vivo Evaluation

Despite promising clinical results in osteochondral defect repair, a recently developed bi-layered collagen/collagen-magnesium-hydroxyapatite scaffold has demonstrated less optimal subchondral bone repair. This study aimed to improve the bone repair potential of this scaffold by adsorbing bone morphogenetic protein 2 (BMP-2) and/or platelet-derived growth factor-BB (PDGF-BB) onto said scaffold. The in vitro release kinetics of BMP-2/PDGF-BB demonstrated that PDGF-BB was burst released from the collagen-only layer, whereas BMP-2 was largely retained in both layers. Cell ingrowth was enhanced by BMP-2/PDFG-BB in a bovine osteochondral defect ex vivo model. In an in vivo semi-orthotopic athymic mouse model, adding BMP-2 or PDGF-BB increased tissue repair after four weeks. After eight weeks, most defects were filled with bone tissue. To further investigate the promising effect of BMP-2, a caprine bilateral stifle osteochondral defect model was used where defects were created in weight-bearing femoral condyle and non-weight-bearing trochlear groove locations. After six months, the adsorption of BMP-2 resulted in significantly less bone repair compared with scaffold-only in the femoral condyle defects and a trend to more bone repair in the trochlear groove. Overall, the adsorption of BMP-2 onto a Col/Col-Mg-HAp scaffold reduced bone formation in weight-bearing osteochondral defects, but not in non-weight-bearing osteochondral defects