In vivo hematopoietic potential of human neuronal stem cells

Transplantation in primary and secondary fetal sheep recipients was used to access the in vivo hematopoietic potential of human neuronal stem cells (NSC). Eleven primary recipients were transplanted with NSC (8×105 cells/fetus) and analyzed for hematopoietic chimerism at 60 days and at 6, 8 and 15 months post-transplant. At 60 days post-transplant human cells were detected in liver, muscle, spleen, thymus and bone marrow. However, at all later time points flow cytometric analysis of PB and BM revealed the presence of human multilineage hematopoietic engraftment but not CD34+ cells. PCR analysis confirmed the presence of human cells in PB and BM and further demonstrated the presence of human cells in liver, thymus, and spleen. At 6 months post-transplant primary sheep were mobilized with G-CSF (5mcg/Kg). The mobilization pattern of sheep engrafted with NSC different from those engrafted with human BM HSC. Unlike HSC sheep, in NSC animals, except for the appearance of 0.12% CD34+ cells in PB on day 3, human cell activity remained low in both BM and PB throughout mobilization. Clonogenic assay of BM cells at 8 months revealed that of the 53 hematopoietic colonies analyzed on day 19 of culture, 8 colonies were of human origin by both karyotype and PCR. At 15 months post-transplant human CD45+/HLA-DR+ cells were obtained from BM of primary sheep by sorting and transplanted into secondary recipients. FACS and PCR analyses of secondary recipients demonstrated the presence of human cells inthe BM and Spleen. These results demonstrate the hematopoietic potential of human NSC and suggest that their hematopoietic activity may be regulated differently from those of human HSC in this xenogeneic model of human hematopoiesis.