Engraftment of Primates with G‐CSF Mobilized Peripheral Blood CD34 ⁺ Progenitor Cells Expanded in G‐CSF, SCF and MGDF Decreases the Duration and Severity of Neutropenia

Abstract

We used a primate model of autologous peripheral blood progenitor cell (PBPC) transplantation to study the effect of in vitro expansion on committed progenitor cell engraftment and marrow recovery after transplantation. Four groups of baboons were transplanted with enriched autologous CD34 + PBPC collected by apheresis after five days of G-CSF administration (100 µg/kg/day). Groups I and III were transplanted with cryopreserved CD34 + PBPC and Groups II and IV were transplanted with CD34 + PBPC that had been cultured for 10 days in Amgen-defined (serum free) medium and stimulated with G-CSF, megakaryocyte growth and development factor (MGDF), and stem cell factor each at 100 ηg/ml. Group III and IV animals were administered G-CSF (100 µg/kg/day) and MGDF (25 µg/kg/day) after transplant, while animals in Groups I and II were not. For the cultured CD34 + PBPC from groups II and IV, the total cell numbers expanded 14.4 ± 8.3 and 4.0 ± 0.7-fold, respectively, and CFU-GM expanded 7.2 ± 0.3 and 8.0 ± 0.4-fold, respectively. All animals engrafted. If no growth factor support was given after transplant (Groups II and I), the recovery of WBC and platelet production after transplant was prolonged if cells had been cultured prior to transplant (Group II). Administration of post-transplant G-CSF and MGDF shortened the period of neutropenia (ANC < 500/µL) from 13 ± 4 (Group I) to 10 ± 4 (Group III) days for animals transplanted with non-expanded CD34 + PBPC. For animals transplanted with ex vivoexpanded CD34 + PBPC, post-transplant administration of G-CSF and MGDF shortened the duration of neutropenia from 14 ± 2 (Group II) to 3 ± 4 (Group IV) days. Recovery of platelet production was slower in all animals transplanted with expanded CD34 + PBPC regardless of post-transplant growth factor administration. Progenitor cells generated in vitro can contribute to early engraftment and mitigate neutropenia when growth factor support is administered posttransplant. Thrombocytopenia was not decreased despite evidence of expansion of megakaryocytes in cultured CD34 + populations.

Impact of CD34 subsets on engraftment kinetics in allogeneic peripheral blood stem cell transplantation

“…However, the phenotypic characterization of primitive cells as CD34 þ is far from sufficient and more accurate characterization of progenitors with stem cell potential within the CD34 þ population is needed. 1,2 In general, the higher the count of CD34 þ cells, the more rapid the engraftment and transplanters tend to infuse all the available CD34 þ cells even if in very high numbers. Recently, however, infusion of high number of CD34 þ cells was shown to be associated with increased risk of chronic GVHD, a highly morbid sequel of BMT.…”

Clinical application of hematopoietic progenitor cell expansion: current status and future prospects

“…33,53 Whether in vitro-cultured cells require continuous exposure to exogenous cytokines after transplantation is unclear, but data in baboons suggest this maneuver will be required to optimize hematopoietic recovery. 94 The appropriate combination of exogenous cytokines for this purpose is unknown and clinical trials are hindered by a lack of reagents due, in part, to commercial considerations.…”

Stem Cells - Clinical Application and Perspectives

“…In the mid 80s, Andrews et al [26] described a monoclonal antibody with which primitive colony forming precursor cells could be enriched from bone marrow. The clustered antigen later termed CD34 (Myo 10) is expressed on hematopoietic stem and progenitor cells.…”