Seeing old friends from a different angle: Novel properties of hematopoietic growth factors in the healthy and diseased brain

Hematopoietic growth factors are known for their bolstering effects on the growth, survival, and differentiation of blood progenitor cells. Several of these cytokines also influence the proliferation of neural stem/progenitor cells, paralleling cellular mechanisms in analogy to their function in the hematopoietic system. Erythropoietin (EPO), granulocyte-colony stimulating factor (G-CSF), thrombopoietin (TPO), and their respective receptors are all expressed in the hippocampus of the mammalian brain. Recent studies have confirmed EPO and G-CSF as vital neurotrophic and neuroprotective factors, and ascertained their role in neuroprotection and neuroregeneration as pertaining to the most prominent neurodegenerative diseases. The aims of this review are to discuss newly discovered properties of G-CSF, EPO, and TPO beyond their known functions in the hematopoietic system, to create an overview of the accumulating data on the role of these factors in hippocampal function, and to highlight any potential clinical implications. (C) 2010 Wiley Periodicals, Inc.