Adoptive transfer of genetically modified human hematopoietic stem cells into preimmune canine fetuses

To develop a surrogate model system for assaying gene transfer into human h ematopoietic stem cells (HSCs) with in vivo repopulating potential, we inje cted human marrow cells transduced with a reporter retroviral vector in lon g-term marrow cultures (LTMCs), into the yolk sacs of preimmune canine fetu ses, Of eight mid-gestation fetuses injected through the exteriorized uteri ne wall and under ultrasound guidance, seven were born alive. One puppy die d in the neonatal period accidentally. The remaining six puppies are all he althy at 31 months of age, There was no evidence for graft-versus-host dise ase or any untoward effects of in utero adoptive transfer of transduced hum an LTR IC cells, All puppies were chimeras. Human cells? detected by fluore scence in situ hybridization, were present in blood, declining from 38% to 0.05% between 10 and 44 weeks after birth. Corresponding numbers for marrow were from 20% to 0.05%, Human cells were also detected in assays of hemato poietic cell progenitors and in stimulated blood cultures, All six puppies were positive for the presence of proviral DNA at various time-points after birth, In three dogs, provirus was detected up to 41 weeks after birth in blood or marrow, and in one dog up to 49 weeks in blood. These data support the further development of this large-animal model system for studies of h uman hematopoie-sis. (C) 1999 International Society for Experimental Hemato l-ogy, Published by Elsevier Science Inc.