Abstract

 Background and Objectives

  Umbilical cord blood (UCB) contains a high number of primitive progenitor cells for transplantation. However, the rate of UCB CD34⁺ stem cell engraftment is low. In this study we examined the effect of human MSCs (mesenchymal stem cell) on engraftment of human UCB-derived CD34⁺ cells in irradiated Balb/c mice.

 Materials and Methods

  Human UCB CD34⁺ cells were obtained from full-term normal deliveries by immunomagnetic techniques and MSCs were isolated by a standard methodology from bone marrow aspirates. Isolated MSCs were evaluated for cell-surface antigens of CD166 and CD105 by flowcytometry. The absolute count of CD34⁺ UCB stem cells was also determined by flowcytometry. Irradiated (7 Gy) Balb/c mice were transplanted intravenously with 0.2 to 1.0 × 10⁶ human UCB CD34⁺ cells in the presence or absence of 0.25 to 1 × 10⁶ human bone marrow-derived MSCs. The mice in every group on day 11 after transplantation were killed and their spleen dissected. In every group, colony assay and H and E staining were performed. To make sure of the presence of human stem cells in spleen colonies, UCB CD34⁺ cells were labeled with super paramagnetic iron oxide (SPIO) before transplantation. The colonies in spleen then underwent Prussian blue staining. In the statistical analyis, Kruskal-Wallis test using SPSS software was employed to determine the number of colonies.

 Results

  Flowcytometry assay showed that after purification, 90% of the cells were CD34⁺ and 96% marker positive for MSCs. Viablity of cells was 100%. Cotransplantation of low doses of UCB CD34⁺ cells (0.2 and 0.3 × 10⁶) and MSC (0.5 and 1 × 10⁶) resulted in a significant increase of the number of colony forming units spleen, in comparison with the engraftment of UCB CD34⁺ stem cells without MSC after 11 days (p<0.01). Prussian blue staining showed the Fe⁺² granules in UCB stem cells. This indicated that cells in the colonies were engrafted UCB CD34⁺ stem cells.

 Conclusions

  The results showed that cotransplantation of MSC with UCB CD34⁺ cells promotes engraftment of UCB CD34⁺ cells.

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  Key words : Stem cell, Cotransplantation, Umbilical cord blood, Mesenchymal stem cell