Cryopreserved Cord Blood Progenitors and Their Cell Adhesion Molecules Are Increased by Coculture With Osteoblasts and Parathyroid Hormone

Abstract

Despite advantages of cord blood (CB) cells, such as their high capacity for proliferation and low immunogenicity, CB transplantation is also associated with delayed neutrophil and platelet recovery relative to bone marrow transplantation. These limitations arise from the reduced abundances of primitive hematopoietic stem cells expressing adhesion molecules in CB relative to bone marrow. To address this limitation, we evaluated whether human parathyroid hormone (hPTH) could increase the number of primitive hematopoietic stem cells with adhesion molecules in cryopreserved CB. When cryopreserved CB cells were cocultured with differentiated osteoblasts in the presence of hPTH, numbers of CD34(+)CD38(-) cells increased 4-fold after 7 days. Exposure to hPTH promoted clonogenic cell expansion and significantly increased the expression of adhesion molecules, such as CD44(+) (a cell surface glycoprotein) and VLA-4(+) (4 integrin) in CD34(+) cells. This result shows that short-term coculture of cryopreserved CB with differentiated osteoblasts in the presence of hPTH may improve the rate of engraftment of CD34(+) cells through increasing the abundances of primitive cells bearing adhesion molecules.