A major challenge in bone tissue engineering is to amplify cell numbers with maintaining the desired phenotype. As a crucial element in bone tissue engineering,the field of scaffold is in the forefront of developments. Due to superiority in both cell expansion and conveyance,the approach of microspherical scaffold has latterly been adopted as the substrate of cell propagation,carrier of expanded cells,as well as scaffold of regenerated bone tissue. Combined with injectable matrices after cell encapsulation or attachment,the microsphere-based system provides an attractive method for highly efficient cell amplification and minimally invasive cell delivery for bone tissue engineering.

Objective To investigate the influence of FTY720 on the lymphocytes and their recovery after withdrawal of FTY720,and on the changes in T cell subsets of inbred mice so as to direct the administration of FTY720. Methods Male inbred C57/bl mice were given FTY720 at the dose of 3 mg/kg per day by oral gavage once a day for 14 days. The PBLs were counted and T cell subsets were analyzed by flow cytometry at the selected time points. Results When FTY720 was administrated, the PBLs showed a sharp decrease and reached the minimum 4 hours later.Then the PBLs remained stable during the whole pe- riod of administration.The PBLs didn’t restore immediately when the reagent was withdrawn,but increased slowly 2 weeks later and completely recovered 6 weeks later.The changes of T cells were similar to PBLs.CD - 8 subsets showed relatively higher sensitivity to FTY720. Conclusions FTY720 is a safe reagent which has rapid and specific effects on PBLs,and the changes in PBLs are reversible.The effect of FTY720 on T cell subsets is similar to that on PBLs.CD - 8 T cells are relatively more sensitive to FTY720.

Objective:To investigate the pahtogengesis and pathology of delayed xenograft rejection (DXR) after pig to rhesus monkey heart xenotransplantation.Methods:Heterotopic xenogeneic heart transplantation in the abdominal cavity was performed using piglet as donors.4 monkeys were used as recipients.Complete complement depletion was achieve in the recipients treated with repetitive doses of a high activity cobra venom factor (Y CVF).The recipients were immunosuppressed with a combination of cyclosporine A,cyclophosphamide and steroids.Sera were analyzed for C3,C4 levels and complement activity and anti pig endotheliocyte xenoantibody.The graft were examined histopathologically and immunohistochemically for C3,C4,C5b 9,IgM,IgG,necrosis factor alpha (TNF alpha),intercellular adhesion molecule 1 (ICAM 1),CD57 (NK cells),CD68 (macrophages),CD4 and CD8.Results:The xenografts survived 8,10,13,13 days respectively and all grafts occoured DXR.Venular thrombosis was outstanding feature within DXR xenografts,complicated with interstitial edma,local hemorrhage and myocardial necrosis,with mild to moderate cellular infiltration.The serum C3 levels and complement activity almost decreased to 0 from the day of transplantation due to Y CVF,the C4 level began to decrease 2 4 days before the cardic xenografts losing their function.The anti pig endotheliocyte xenoantibody also decreased after transplantation,and slightly increased during DXR,all rejected xenografts showed C3,C4,C5b 9,IgG and IgM deposits in different degree.Large numbers of macrophages (50% of total leukocytes) were found infiltrating the entire xenograft,a few natural killer cells (8%～10%),some of CD4+T cells (15%) and CD8+T cells (25%) were detcted also,up regulation of ICAM 1 on the graft endothelial cells and TNF alpha in the interstitial were demonstrated in the rejected heart.Conclusion:Both Humor and cell mediated immunologic reaction may play an important role in pahtogengesis of DXR. [