Adult Human Blood Leukocytes as an Efficient Source for Tissue-Committed Neural Progenitors.

In the last few years, significant progress has been made in the isolation and characterization of bone marrow stem cell populations and their potential to differentiate into a variety of cellular lineages. We hypothesized that peripheral blood can also be used as a source for precursor cells that can become committed progenitors for a variety of tissues. We report here the generation and characterization in vitro of neural progenitor cells from a newly discovered blood-derived multipotent cell population, named synergetic cell population (SCP). Human blood samples were obtained from the Israeli blood bank and SCP cells were purified based on cellular density. Neural progenitors were generated by culturing SCP cells in medium supplemented with autologous serum, followed by activation in a defined serum-free medium containing the specific differentiation-inducing factors F12, B27, bFGF, BDNF, and NGF.

An average of 13.5x10⁶ neural progenitor cells was generated from 450 ml blood. These cells developed irregular perikarya, from which filamentous extensions spread contacting neighboring cells and forming net-like structures. Immunostaining revealed that some of the cells express the early neuronal progenitor markers nestin and b-tubulin and Neu-N, a nuclear protein present in mature neurons. Other cells expressed glial-specific antigens, such as O4 (a marker of oligodendrocytes) and GFAP (a marker of astrocytes). Flow cytometry analysis showed that 44.4% and 34% of the cells were positive for nestin and b-tubulin, respectively. In addition to exhibiting phenotypic evidence of markers specific for the neural lineage, these progenitor cells also responded to the neurotransmitters glutamate and GABA, as detected by calcium influx through voltage-gated calcium channels, demonstrating functional differentiation.

In this study we show that generation of neural progenitors from peripheral blood is feasible and efficient. Blood-derived angiogenic progenitors produced in our system are already safely and efficiently administrated to severe angina pectoris patients in a clinical trial we are conducting in Thailand (reported in a separate abstract by our group). The newly discovered source of these progenitors, the blood-derived multipotent population which we termed SCP, contains both hematopoietic stem cells as well as supportive cells that enable differentiation into various lineages. The therapeutic potential of these neural progenitors will be further characterized and evaluated in vivo using animal models.