Platelet Platelet-Derived Microparticles Stimulate The Proliferation Of Human Umibilical Cord Blood Hematopoietic Stem Cells

Objective: An attempt was made to investigate the preparation of platelet-derived microparticles (PMPs) and the effect of PMPs on stimulating the proliferation of progenitors of human umibilical cord blood hematopoietic stem cells. Methods :Different concentrations of thrombin were adopted to activate the platelets to release PMPs. Flow cytometry was adopted to evaluate the efficiencies of different concentrations of thrombin to produce PMPs. Scan electron microscopy was adopted to oberserve the morphological changes of platelets activated by thrombin in different phases. Umbilical cord blood mononuclear cells (MNCs) were obtained from healthy donors and isolated the MNCs by Ficoll density gradient centrifugation. MNCs were cultured in 2.7% methylcellulose containing different concentrations of PMPs(10μg/ml,50μg/ml and 100μg/ml) or platelet(200×109/L) and colonies were counted under an inverted microscope after 7 days. MNCs were cultured in serum-free medium containing 50μg/ml PMPs and flow cytometry was adopted to evaluate the ratio of CD34 of MNCs after 7 days.Results: The efficiencies of PMPs activated by 2.0 U/ml, 1.5 U/ml,1.0 U/ml and 0.5 U/ml thrombin were 28.7%, 47.7%, 50.1% and 43.9% respectively. The colony formation was enhanced with PMPs and was dependently stimulated with PMPs and platelet. The number of colonies per 2×105 MNCs in the group of PMPs (10μg/ml, 50μg/ml and 100μg/ml) and platelet(200×109/L) were 119.8±32.2, 142.9±45.2, 180.8±85.1 and 136.5±43.6 respectively. The number of colonies in the group of PMPs 100μg/ml,50μg/ml and platelet(200×109/L) were statistically significant when compared with control group (103.0±24.8) (p<0.05). The number of colonies per 2×105 MNCs in the group of PMPs(10μg/ml) was 119.8±32.2 which was slight higher than control group, but there was no statistical significance between two groups. The ratio of CD34 of MNCs in the group of PMPs 50μg/ml was 0.733%±0.743% compared with control group(0.433±0.538)(p<0.05).Conclusion: 1.0U/ml thrombin activated platelet could get the best efficiency of PMPs and PMPs could stimulate the proliferation progenitors of granulocyte-macrophage of umbilical cord blood and the expression of umbilical cord blood MNCs'CD34.