Gene Transfer into Fetal Baboon Hematopoietic Progenitor Cells

Abstract

We studied hematopoietic progenitors from fetal baboon blood, marrow, and liver at four time points (125, 140, 160, and 175 days) during the third trimester (gestation approximately 180 days) to determine if fetal baboons might be an appropriate model for in utero gene therapy of hematopoietic stem cells (HSCs). Cells were studied for expression of CD34, CD33, CD38, and HLA-DR, for progenitor content in colony-forming cell assays, and for susceptibility of CD34+ progenitors to retrovirus-mediated gene transfer. Throughout the third trimester, the frequency of CD34+ progenitors in blood and marrow appears to remain unchanged at approximately 0.6 and 5.0%, respectively. In liver, progenitors progressively decrease to undetectable levels by day 175. The proportion of fetal baboon bone marrow and liver CD34+ cells expressing CD38 and HLA-DR appears to increase with increasing fetal age, similar to changes reported for human cord blood CD34+ cells. In fetal baboon blood the proportion of CD34+ cells expressing CD33 appears to decrease with increasing gestational age, also similar to changes reported for human cord blood cells. Progenitors from human cord blood and baboon fetal tissues were similarly susceptible to transduction by the gibbon ape leukemia pseudotyped retroviral vector LAPSN(PG13) containing the genes for human placental alkaline phosphatase (AP) and the bacterial neomycin phosphotransferase (neo). Fetal baboon and human hematopoietic progenitor cells undergo similar phenotypic changes during the third trimester of fetal development and are similarly susceptible to retrovirus-mediated gene transfer. The fetal baboon may be a model in which approaches to mobilization and gene transfer into fetal HSCs can be studied.

Effect of Age on the Frequency, Cell Cycle, and Lineage Maturation of Rhesus Monkey (Macaca mulatta) CD34+ and Hematopoietic Progenitor Cells

“…Similar to findings in humans and baboons (34,35,71,72), these results suggest that bone marrow CD34 ϩ cells from young rhesus monkeys retain higher self-renewal and proliferative potential than those obtained from older animals. The rhesus monkey model will be crucial for assessing differences in stem cell biology with advancing age and for exploring unique needs that may arise in the use of cell-and gene-based therapies in older compared with younger individuals.…”

High-Efficiency Retroviral Transduction of Fetal Liver CD38–CD34++ Cells: Implications for in utero and ex utero Gene Therapy

“…Since the techniques required for fetal blood transfusion are well established, it may be feasible to isolate fetal blood stem cells, transduce these cells ex utero and then return them to the fetus [42,43]. A study using fetal baboons has provided encouraging data supporting such an approach [44], yet further investigation is required to optimize the collection and transduction of fetal stem cells. We are motivated to further pursue fetal gene therapy by the pioneering efforts at fetal stem cell transduction made by Humeau et al [8] and the refinements that we have been able to make to the process.…”

Prospects for prenatal gene therapy in disorders causing mental retardation

“…Both groups demonstrated longterm transduction of the offspring for 2-5 years. Winkler et al [1999] studied fetal baboon hematopoietic progenitor cells and noted significant phenotypic and functional homology between baboons and humans. Specifically, the frequency of progenitor cells in the bone marrow and blood remained constant during the third trimester, while fetal liver showed a decline in progenitor cells.…”