Laddec® versus Bio-Oss®: The effect on the healing of critical-sized defect - Calvaria rabbit model.

The aim of this study was to evaluate the in vivo performance of two different deproteinized bovine bone (DBB) grafting materials: DBBB (Bio-Oss®) and DBBL (Laddec®), for the regeneration of critically sized (8 mm) defects in rabbit's calvaria. Three round-shaped defects were surgically created in the calvaria of 13 New Zealand White rabbits proximal to the coronal suture in the parietal bone. Two of the defects were filled with one of the grafting materials while a third was left empty to serve as a negative control. Bone regeneration properties were evaluated at 4- and 8-weeks after implantation by means of histological and histomorphometrical analyses. Statistical analyses were performed through a mixed model analysis with fixed factors of time and material. Histological evaluation of the control group evidenced a lack of bridging bone formation across the defect sites at both evaluation time points. For the experimental groups, new bone formation was observed around the defect periphery and to progress radially inwards to the center of the defect site, regardless of the grafting material. Histomorphometric analyses at 4 weeks demonstrated higher amount of bone formation through the defect for DBBB group. However, at 8 weeks, DBBL and DBBB demonstrated osteoconductivity and low resorption rates with evidence of statistically similar bone regeneration through the complete boney defect. Finally, DBBB presented lower soft tissue migration within the defect when compared to DBBL at both evaluation time points. DBBB and DBBL presented similar bone regeneration performance and slow resorption rates. Although both materials promoted bone regeneration through the complete defect, DBBB presented lower soft tissue migration within the defects at 4- and 8-weeks.

Pertussis toxin promotes macrophage survival through inhibition of acid sphingomyelinase and activation of the phosphoinositide 3-kinase/protein kinase B pathway.

Apoptosis is an important mechanism involved in regulating the number of macrophages present at sites of inflammation. Several lines of evidence indicate that blocking macrophage apoptosis can increase atherosclerosis. We previously reported that oxidized LDL can inhibit apoptosis in cultured bone marrow-derived macrophages. We used pertussis toxin (PTX) to test whether G protein coupled receptors are activated by oxLDL. PTX is a bacterial toxin that inhibits Gi activation by ADP-ribosylating the alpha subunit of Gi, preventing the subunit from interacting with receptors. Unexpectedly, we found that PTX by itself selectively blocks macrophage apoptosis in a dose-dependent manner. PTX acts in part by inhibiting acid sphingomyelinase activity which in turn prevents generation of ceramide, which is required for macrophage apoptosis. A Gi activator peptide, mastoparan, increased ceramide levels in macrophage and induced apoptosis, but pre-treatment with PTX partially overrode mastoparan-induced apoptosis. The anti-apoptotic effect of PTX was found to require ADP-ribosylation. PTX failed to prevent A-SMase activation or apoptosis in macrophages lacking TLR4. The anti-apoptotic effect of PTX involved the same signaling pathways as those of oxidized LDL, in that both inhibited acid sphingomyelinase, and activated the phosphoinositide 3 kinase (PI3K)/protein kinase B (PKB) pathway which leads to nuclear localization of the transcription factor NFkappaB and up-regulation of Bcl-XL. These results indicate that Gi proteins, TLR4, A-SMase and the PI3K/PKB pathway are crucial components for regulation of macrophage apoptosis.