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a Division of Clinical Research, Fred
Hutchinson Cancer Research Center, Seattle, Washington, USA;
b Department of Pediatrics, University of
Washington School of Medicine, Seattle, Washington, USA;
c Amgen, Inc., Thousand Oaks, California, USA;
d University of Washington Regional Primate
Research Center, Seattle, Washington, USA, and
e Bone Marrow Transplant Program, University
of Colorado Health Science Center, Denver, Colorado,
USA
Key Words. CD34 • Expansion • Hematopoietic progenitors • MGDF • SCF • Transplantation
Dr. Robert G. Andrews, Pediatric Oncology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., P.O. Box 19024, Seattle, Washington 98109-1024, USA.
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
g/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
vivo-expanded 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 post-transplant. Thrombocytopenia was not decreased
despite evidence of expansion of megakaryocytes in cultured
CD34+ populations. Stem Cells
1999;17:210-218
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