Functional response to SDF1α through over-expression of CXCR4 on adult subventricular zone progenitor cells

Abstract

The chemokine receptor CXCR4 and its ligand, stromal cell derived factor-1 alpha (SDF1 alpha) regulate neuroblast migration towards the ischemic boundary after stroke. Using loss- and gain-function, we investigated the biological effect of CXCR4/SDF1 alpha on neural progenitor cells. Neural progenitor cells, from the subventricular zone (SVZ) of the adult rat, were transfected with rat CXCR4-pLEGFP-C1 and pSIREN-RetroQ-CXCR4-siRNA retroviral vectors. Migration assay analysis showed that inhibition of CXCR4 by siRNA significantly reduced cell migration compared to the empty vector, indicating that CXCR4 mediated neural progenitor cell motility. When neural progenitor cells were cultured in growth medium containing bFGF (20 ng/ml), over-expression of CXCR4 significantly reduced the cell proliferation as measured by the number of bromodeoxyuridine+ (BrdU+) cells (26.4%) compared with the number in the control group (54.0%). Addition of a high concentration of SDF1 alpha (500 ng/ml) into the progenitor cells with over-expression of CXCR4 reversed the cell proliferation back to the control levels (57.6%). Immunostaining analysis showed that neither over-expression nor inhibition of CXCR4 altered the population of neurons and astrocytes, when neural progenitor cells were cultured in differentiation medium. These in vitro results suggest that CXCR4/SDF1 alpha primarily regulates adult neural progenitor cell motility but not differentiation, while over-expression of CXCR4 in the absence of SDF1 alpha decreases neural progenitor cell proliferation.

Cellular and Molecular Determinants of Stroke-Induced Changes in Subventricular Zone Cell Migration

“…Reactive astrocytes secrete SDF-1a, and neuroblasts express the corresponding CXCR4 receptor (38, 42, 116). Overexpression of SDF-1a results in increased neuroblast recruitment, while functional blocking antibodies or siRNA to the CXCR4 receptor had the opposite effect (65,95,112). ERK signaling may mediate the effect of SDF-1a on neuroblast migration (69).…”

“…A dult neurogenesis is the generation of new neurons from resident neural stem cell (NSC) populations in the adult brain (65). In many mammalian species, including rodents, higher primates, and humans, heterogeneous neural stem cell populations reside in two distinct neurogenic niches in the adult brain, the subventricular zone (SVZ) surrounding the lateral ventricles (Fig, 1), and the subgranular zone (SGZ) of the hippocampal dentate gyrus (22,24,27,98).…”

Contribution of SDF-1a/CXCR4 Signaling to Brain Development and Glioma Progression

“…Moreover, overexpression of CXCR4 in the presence of bFGF conversely suppresses cell proliferation, but further addition of SDF-1α to the NPCs reverses the cell proliferation back to control levels [175]. In addition, Khan et al [176] found that SDF-1α supports survival and protects from apoptosis of postmitotic neurons through the counteraction of the Rb-E2F pathway.…”

“…As for neural progenitor cells, SDF-1α/CXCR4 mainly regulates not cell differentiation but cell motility, while overexpression of CXCR4 alone without SDF-1α inhibits cell proliferation [175]. Moreover, overexpression of CXCR4 in the presence of bFGF conversely suppresses cell proliferation, but further addition of SDF-1α to the NPCs reverses the cell proliferation back to control levels [175].…”

Inflammatory Regulators of Redirected Neural Migration in the Injured Brain

“…The CXCL12/CXCR4 ligand/receptor pair promotes NPC migration in vitro [64,82,83,84] in a phosphoinositol-3-kinase-dependent manner [85]. Moreover, in vivo studies showed that CXCL12/CXCR4 regulates the migration of NPCs of the SVZ in adult rodent brain [86], with further work suggesting that CXCR7, an alternate CXCL12 receptor, is also involved in this process [87].…”