Effect of ischemic preconditioning on skeletal tissue tolerance after warm venous ischemia.

PURPOSE: Free muscular flaps are commonly used in plastic surgery. The main reason of failure is thrombosis induced by a phenomenon called ischemia reperfusion. Preconditioning showed an interest to prevent ischemia reperfusion injury in transplantation surgery. The aim of the study is to evaluate the effect of ischemic preconditioning on skeletal tissue tolerance after warm venous ischemia. MATERIALS AND METHODS: We realized an experimental study with latissimus dorsi flaps of 12 pigs, divided in 6 groups in function of their time of preconditioning and duration of warm venous ischemia. A morphologic analysis was performed measuring cell's diameter and interstitial tissue area and notifying the presence or absence of neutrophils, necrosis or intravascular thrombosis. To detect inflammation, necrosis or hypoxia, immunohistochemistry was effectuated using the follow primary antibodies, AIF, HIF1 alpha, caspase 3, SOD 1 and PKC epsilon. TUNEL assay showed apoptosis cells, were realized. One way Anova test was performed to compare the quantitative evolution over time of histological parameters and rate of apoptosis. RESULTS: Preconditioning of 40min or 1hour allowed to reduced ischemia reperfusion lesions: no cellular or interstitial oedema, reduction of neutrophils infiltrate and intravascular thrombus. TUNEL assay showed a higher rate of apoptosis nucleus for the control group E compared to preconditioning group C and D. Immunohistochemistry results were no relevant. CONCLUSION: We showed a diminution of lesions of ischemia reperfusion for experimental groups with preconditioning: diminution of interstitial oedema, of cellular oedema, diminution of neutrophils infiltrated and level of apoptosis cells. Preconditioning of 40minutes were as efficient as one hour.

In-vitro and in-vivo design and validation of an injectable polysaccharide-hydroxyapatite composite material for sinus floor augmentation.

OBJECTIVE: Polysaccharide-based composite matrices consisting of natural polysaccharides, pullulan and dextran supplemented with hydroxyapatite (Matrix-HA) have recently been developed. The principal objective of this study was to evaluate the capacities of this composite material to promote new bone formation in a sinus lift model in the sheep. Secondary objectives were to evaluate in vitro properties of the material regarding cell adhesion and proliferation. METHODS: In this report, once such composite matrix was prepared as injectable beads after dispersion in a physiological buffer, and evaluated using a large animal model (sheep) for a sinus lift procedure. RESULTS: In vitro studies revealed that these microbeads (250-550µm in diameter) allow vascular cell adhesion and proliferation of Endothelial Cells (EC) after 1 and 7 days of culture. In vivo studies were performed in 12 adult sheep, and newly formed tissue was analyzed by Cone Beam Computed Tomography (CBCT scanning electron microscopy (SEM) and by histology 3 and 6 months post-implantation. CBCT analyses at the implantation time revealed the radiolucent properties of these matrices. Quantitative analysis showed an increase of a dense mineralized tissue in the Matrix-HA group up to 3 months of implantation. The mineralized volume over total volume after 6 months reached comparable values to those obtained for Bio-Oss® used as positive control. Histological examination confirmed that the Matrix-HA did not induce any long term inflammatory events, and promoted direct contact between the osteoid tissue and lamellar bone structures and beads. After 6 months, we observed a dense network of osteocytes surrounding both biomaterials as well as a newly vascularized formed tissue in close contact to the biomaterials. SIGNIFICANCE: In conclusion, the absence of animal components in Matrix-HA, the osteoconductive property of Matrix-HA in sheep, resulting in a dense bone and vascularized tissue, and the initial radiolucent property to follow graft integration offer great promises of this composite material for clinical use.