SDF1-A facilitates Lin-/Sca1+ cell homing following murine experimental cerebral ischemia

Background: Hematopoietic stem cells mobilize to the peripheral circulation in response to stroke. However, the mechanism by which the brain initiates this mobilization is uncharacterized. Methods: Animals underwent a murine intraluminal filament model of focal cerebral ischemia and the SDF1-A pathway was evaluated in a blinded manner via serum and brain SDF1-A level assessment, Lin-/Sca1+ cell mobilization quantification, and exogenous cell migration confirmation; all with or without SDF1-A blockade. Results: Bone marrow demonstrated a significant increase in Lin-/Sca1+ cell counts at 24 hrs (272±60%; P<0.05 vs sham). Mobilization of Lin-/Sca1+ cells to blood was significantly elevated at 24 hrs (607±159%; P<0.05). Serum SDF1-A levels were significant at 24 hrs (Sham (103±14), 4 hrs (94±20%, p = NS) and 24 hrs (130±17; p<0.05)). Brain SDF1-A levels were significantly elevated at both 4 hrs and 24 hrs (113±7 pg/ml and 112±10 pg/ml, respectively; p<0.05 versus sham 76611 pg/ml). Following administration of an SDF1-A antibody, Lin-/Sca1+ cells failed to mobilize to peripheral blood following stroke, despite continued up regulation in bone marrow (stroke bone marrow cell count: 536±65, blood cell count: 127±24; p<0.05 versus placebo). Exogenously administered Lin-/Sca1+ cells resulted in a significant reduction in infarct volume: 42±5% (stroke alone), versus 21±15% (Stroke+Lin-/Sca1+ cells), and administration of an SDF1-A antibody concomitant to exogenous administration of the Lin-/Sca1+ cells prevented this reduction. Following stroke, exogenously administered Lin-/Sca1+ FISH positive cells were significantly reduced when administered concomitant to an SDF1-A antibody as compared to without SDF1-A antibody (10±4 vs 0.7±1, p<0.05). Conclusions: SDF1-A appears to play a critical role in modulating Lin-/Sca1+ cell migration to ischemic brain.