Fast recovery of platelet production in NOD/SCID mice after transplantation with ex vivo expansion of megakaryocyte from cord blood CD34+ cells

Background: Cord blood transplantation (CBT) can be a life-saving procedure in the treatment of a broad variety of disorders, including hematologic, immune, and genetic diseases. However, delayed platelet recovery hinders the application of CBT. Purpose: The aim of this study was to determine the optimal combination of cytokines to amplify megakaryocyte (Mk). Methods: CB CD34+ cells were obtained by immunomagnetic isolation and amplified under four different cytokine combinations. CD34+ cells of the group with thrombopoietin (TPO), stem cell factor (SCF), Flt-3 ligand (FL), and interleukin-6 (IL-6) were collected on days 0, 3, 7, 10, and 14. Immunophenotype was analyzed by flow cytometry (FCM). Polyploidic Mk cultured cells were collected on days 7 and 14 for colony-forming unit-Mk assay. The NOD/SCID mice were injected with expanded CD34+ cells, and the peripheral blood (PB) and bone marrow (BM) were tested on 3, 7, and 14 days. Results: The group with TPO, SCF, FL, and IL-6 reached the maximal total expansion fold and Mk population at day 7, which was slightly reduced later. After transplantation into NOD/SCID mice with expanded CD34+ cells, the human CD41+ cells were detected in mice PB on day 3 and in BM on day 7, then disappeared after 14 days. The expressing of activated platelet CD 42b+/CD62P+ increased gradually after transplantation. Conclusion: Platelets can recover rapidly in vivo by means of expanded CD34+ cells with various cytokines. In our system, a group of TPO, SCF, FL, and IL-6 represents the best cytokine combination for expansion of Mk progenitor cells from CB CD34+ cells.