G-CSF is a potent hematopoietic factor that enhances survival and drives differentiation of myeloid lineage cells, resulting in the generation of neutrophilic granulocytes. Here, we show that G-CSF passes the intact blood-brain barrier and reduces infarct volume in 2 different rat models of acute stroke. G-CSF displays strong anti-apoptotic activity in mature neurons and activates multiple cell survival pathways. Both G-CSF and its receptor are widely expressed by neurons in the CNS, and their expression is induced by ischemia, which suggests an autocrine protective signaling mechanism. Surprisingly, the G-CSF receptor was also expressed by adult neural stem cells, and G-CSF induced neuronal differentiation in vitro. G-CSF markedly improved long-term behavioral outcome after cortical ischemia, while stimulating neural progenitor response in vivo, providing a link to functional recovery. Thus, G-CSF is an endogenous ligand in the CNS that has a dual activity beneficial both in counteracting acute neuronal degeneration and contributing to long-term plasticity after cerebral ischemia. We therefore propose G-CSF as a potential new drug for stroke and neurodegenerative diseases.

Background and Purpose-Both the administration of growth factors and physical therapy such as forced arm use (FAU) are promising approaches to enhance recovery after stroke. We explored the effects of these therapies on behavioral recovery and molecular markers of regeneration after experimental ischemia. Methods-Rats were subjected to photothrombotic ischemia: sham (no ischemia), control (ischemia), brain-derived neurotrophic factor (BDNF; ischemia plus BDNF, 20 g), and FAU (ischemia plus FAU, 1-sleeve plaster cast ipsilateral limb). Animals survived 1 or 6 weeks and underwent behavioral testing (Rotarod, beam balance, adhesive removal, plantar test, neuroscore). After the rats were killed, brain sections were immunostained for semiquantitative analysis of MAP1B, MAP2, synaptophysin, GFAP expression, and quantification of infarct volumes. Results-Infarct volumes were not different between the groups 1 or 6 weeks after ischemia. BDNF-treated animals had better functional motor recovery (Rotarod, beam balance, neuroscore) compared with all other groups (PϽ0.05). There was no significant adverse effect of early FAU treatment on motor recovery, although sensorimotor function (adhesive removal test) was impaired (PϽ0.05). There were no differences between groups as measured by nociception of the left and right forepaw (plantar test). BDNF treatment transiently induced MAP1B expression in the ischemic border zone and synaptophysin expression within the contralateral cortex 6 weeks after ischemia (PϽ0.05

Brain-derived neurotrophic factor (BDNF), acting through the high-affinity receptor tyrosine kinase (TrkB), is widely distributed throughout the central nervous system and displays in vitro trophic effects on a wide range of neuronal cells, including hippocampal, cerebellar, and cortical neurons. In vivo, BDNF rescues motorneurons, hippocampal, and substantia nigral dopaminergic cells from traumatic and toxic brain injury. After transient middle cerebral artery occlusion (MCAO), upregulation of BDNF-mRNA in cortical neurons suggests that BDNF potentially plays a neuroprotective role in focal cerebral ischemia. In the current study, BDNF (2.1 micrograms/d) in vehicle or vehicle alone (controls) was delivered intraventricularly for 8 days, beginning 24 hours before permanent middle cerebral artery occlusion by intraluminal suture in Wistar rats (n = 13 per group). There were no differences in physiological variables recorded during surgery for the two groups. Neurological deficit (0 to 4 scale), which was assessed on a daily basis, improved in BDNF-treated animals compared with controls (P < 0.05; analysis of variance and Scheffe's test). There were no significant differences in weight in BDNF-treated animals and controls during the experiment. After elective killing on day 7 after MCAO, brains underwent 2,3,5-triphenyltetrazolium chloride staining for calculation of the infarct volume and for histology (hematoxylin and eosin and glial fibrillary acid protein). The mean total infarct volume was 83.1 +/- 27.1 mm3 in BDNF-treated animals and 139.2 +/- 56.4 mm3 in controls (mean +/- SD; P < 0.01, unpaired, two-tailed t-test). The cortical infarct volume was 10.8 +/- 7.1 mm3 in BDNF-treated animals and 37.9 +/- 19.8 mm3 in controls (mean +/- SD; P < 0.05; unpaired, two-tailed t-test), whereas ischemic lesion volume in caudoputaminal infarction was not significantly different. These results show that pretreatment with intraventricular BDNF reduces infarct size after focal cerebral ischemia in rats and support the hypothesis of a neuroprotective role for BDNF in stoke.