Neuroprotective effect of granulocyte colony-stimulating factor after focal cerebral ischemia

Ischemic tolerance in the brain

Endogenous tolerance to cerebral ischemia is nature's strategy for neuroprotection. Exploring the physiologic and molecular mechanism of this phenomenon may give us new means of protection against ischemia and other degenerative disorders. This article reviews the currently available experimental methods to induce ischemic tolerance in the brain and gives a brief summary of the potential mode of action.

The hematopoietic factor G-CSF is a neuronal ligand that counteracts programmed cell death and drives neurogenesis

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.

Granulocyte colony-stimulating factor is not protective against selective dopaminergic cell death in vitro

In the present study, we evaluated the potential neuroprotective effect of granulocyte colony-stimulating factor (G-CSF), a hematopoietic growth factor in two different culture models in which dopaminergic (DA) neurons die selectively: first, in a culture model in which death of DA neurons occurs spontaneously and second, in a toxin-based paradigm, the in vitro 1-methyl-4-phenylpyridinium model of PD. In neither of the two models, a treatment with G-CSF, could prevent or halt the progressive neurodegeneration. However, we cannot rule out that G-CSF might exert neuroprotective or even deleterious effects in in vivo models of PD, based on the significant increase in the number of microglial cells observed after G-CSF treatment.

Granulocyte colony-stimulating factor induces sensorimotor recovery in intracerebral hemorrhage

Granulocyte colony-stimulating factor (G-CSF) has been used in the treatment of neutropenia in hematologic disorders. The neuroprotective and anti-inflammatory effects of G-CSF were reported in various neurological disease models. In this study, we examined whether G-CSF induces functional recovery after intracerebral hemorrhage (ICH). ICH was induced using collagenase injection in adult rats. Either G-CSF (50 microg/kg, i.p.) or saline was given from 2 h after ICH and every 24 h for 3 days. 72 h after ICH induction, the rats were sacrificed for histological analysis and measurement of brain edema. Behavioral tests were performed before and 1, 7, 14, 21, 28, and 35 days after ICH. We also measured the blood-brain barrier (BBB) permeability using Evans blue dye injection method. G-CSF-treated rats recovered better on rotarod and limb placing tests, starting from 14 days throughout 5 weeks after ICH. The brain water content and BBB permeability of G-CSF-treated group decreased in the lesioned hemispheres compared with those of ICH-only group. In G-CSF-treated group, the number of TUNEL+, myeloperoxidase+, and OX42+ cells was smaller than that of ICH-only group in the periphery of hematoma. These findings suggest that G-CSF induces long-term sensorimotor recovery after ICH with reduction of brain edema, inflammation, and perihematomal cell death.

G-CSF reduces infarct volume and improves functional outcome after transient focal cerebral ischemia in mice

Growth factors possess neuroprotective and neurotrophic properties in vitro, but few have been extensively studied in vivo after stroke. In the present study, we investigated the potential functional benefits of granulocyte colony-stimulating factor (G-CSF) administration after focal cerebral ischemia. Male mice underwent 60-minute middle cerebral artery occlusion (MCAO) and received G-CSF (50 microg/kg, subcutaneously) or vehicle (saline) at the onset of reperfusion. Granulocyte colony-stimulating factor-treated mice killed at 48 hours after MCAO revealed a >45% reduction (P<0.05) in lesion volume. In terms of body weight recovery, and in tests of motor (grid test and rotarod) and cognitive ability (water maze), MCAO significantly worsened the outcome in vehicle-treated mice as compared with shams (P<0.05). However, G-CSF treatment was beneficial as, compared with vehicle, this significantly improved weight recovery and motor ability. This effect was most apparent on the water maze where G-CSF-treated mice were indistinguishable from shams in terms of acquiring the task. These results indicate long-term beneficial effects of a single dose of G-CSF administered on reperfusion, and illustrate the need to further investigate the mechanisms of G-CSF action.

Mechanisms of Psychopharmacological Effects of Granulocytic Colony-Stimulating Factor during Severe Hypoxia

Granulocytic colony-stimulating factor produced a strong therapeutic effect during encephalopathy of different genesis. The preparation improved the psychoneurological status and increased the number of neural precursors in the paraventricular area of cerebral hemispheres in animals.

Effect of granulocyte colony-stimulating factor on functional and histopathologic outcome after traumatic brain injury in mice

OBJECTIVE

Granulocyte colony-stimulating factor has been used to reduce the risk of sepsis in patients with traumatic brain injury. However, granulocyte colony-stimulating factor exerts potent pro- and anti-inflammatory effects that could influence secondary injury, and outcome, after traumatic brain injury. Our objective was to determine the effect of granulocyte colony-stimulating factor on histopathologic, motor, and cognitive outcome after experimental traumatic brain injury in mice.

DESIGN

Experimental study.

SETTING

Research laboratory at the Massachusetts General Hospital, Boston, MA.

SUBJECTS

Forty-eight adult male C57Bl/6 mice.

INTERVENTIONS

Mice (8 wks of age, n = 16/group) were administered granulocyte colony-stimulating factor or saline subcutaneously twice per day for 7 days after controlled cortical impact or sham injury (n = 16). Absolute neutrophil counts, motor function, Morris water maze performance, and lesion volume were determined after controlled cortical impact or sham injury.

MEASUREMENTS AND MAIN RESULTS

At the time of controlled cortical impact, body weight, brain and body temperature, and systemic absolute neutrophil counts did not differ between groups. Compared with control, systemic absolute neutrophil count was increased more than ten-fold in granulocyte colony-stimulating factor-treated mice on posttrauma days 2 and 7 (p < .05, repeated-measures analysis of variance) but did not differ between groups by day 14. There were no differences between groups in tests of motor function or histopathologic outcome. However, compared with control, mice given granulocyte colony-stimulating factor had improved Morris water maze performance after controlled cortical impact (p < .05, repeated-measures analysis of variance) but not sham injury.

CONCLUSIONS

The data suggest a small beneficial effect of granulocyte colony-stimulating factor on functional outcome after traumatic brain injury in adult mice but do not show differences in histopathology or motor outcome between treated and control groups.

Adult stem cell therapy in stroke

PURPOSE OF REVIEW

Acute cerebral infarction causes irreversible locally restricted loss of the neuronal circuitry and supporting glial cells with consecutive functional deficits and disabilities. The currently available and effective therapy targets fast vessel recanalization accompanied by symptomatic measures. Research activities focusing on stem cells, which represent a promising source for organotypic cell replacement and functional recovery after stroke, have gained momentum in recent years, making regenerative cell-based therapies a much more feasible realistic approach. This review provides an update about preclinical and clinical cell-based studies in stroke focusing on stem cells derived from the adult central nervous and hematopoetic systems.

RECENT FINDINGS

Endogenous neural stem cells, which have been shown to reside throughout life in the central nervous system, have the capacity to replace lost neurons in models for numerous disorders, including cerebral ischemia. Considering adult neural stem cell transplantation as a regenerative strategy after stroke, progress has been made in isolating human adult neural stem cells and demonstrating the feasibility of autologous neural stem cell transplantation. An increasing number of studies provide evidence that hematopoietic stem cells, either after stimulation of endogenous stem cell pools or after exogenous hematopoietic stem cell application (transplantation), improve functional outcome after ischemic brain lesions. Various underlying mechanisms such as transdifferentiation into neural lineages, neuroprotection through trophic support, and cell fusion have been deciphered.

SUMMARY

Many preclinical studies employing adult stem cell-based strategies hold great promise. For endogenous approaches the correlate of cell replacement underlying functional improvement needs to be demonstrated. Transplantation approaches on the experimental level need further development before clinical application can be considered.

A hematopoietic growth factor, thrombopoietin, has a proapoptotic role in the brain

Central nervous and hematopoietic systems share developmental features. We report that thrombopoietin (TPO), a stimulator of platelet formation, acts in the brain as a counterpart of erythropoietin (EPO), a hematopoietic growth factor with neuroprotective properties. TPO is most prominent in postnatal brain, whereas EPO is abundant in embryonic brain and decreases postnatally. Upon hypoxia, EPO and its receptor are rapidly reexpressed, whereas neuronal TPO and its receptor are down-regulated. Unexpectedly, TPO is strongly proapoptotic in the brain, causing death of newly generated neurons through the Ras-extracellular signal-regulated kinase 1/2 pathway. This effect is not only inhibited by EPO but also by neurotrophins. We suggest that the proapoptotic function of TPO helps to select for neurons that have acquired target-derived neurotrophic support.

Neuronal co-expression of EGFP and beta-galactosidase in mice causes neuropathology and premature death

Dose-dependent co-expression of enhanced green fluorescent protein (EGFP) and beta-galactosidase (beta-gal) in the cytoplasm of forebrain neurons of two independent mouse lines resulted in growth retardation, weakness, and premature lethality. In primary motor cortex and striatum, apoptosis, glial fibrillary acidic protein proliferation, and cell loss were found. In addition, we observed aggregations of EGFP and beta-gal that colocalized with ubiquitin. GFP is unlikely to be toxic per se, as a third mouse line that expressed twice as much GFP in the cytoplasm of forebrain neurons as the two affected lines was normal. Cytoplasmic aggregations of EGFP and beta-gal occurred in affected and phenotypically normal mice suggesting a storage function rather than being detrimental. We successfully prolonged survival of affected mice with granulocyte colony-stimulating factor (GCSF) and the antibiotic minocycline. These compounds could protect neurons from EGFP and beta-gal-induced dysfunction, as demise of mice started after treatment was discontinued.

Nonmyeloablative allogeneic bone marrow transplantation for treatment of myelodysplastic syndrome complicated by recent intracerebral hemorrhage

A patient with intracerebral hemorrhage is considered ineligible for hematopoietic stem cell transplantation (HSCT). We report a 49-year-old woman with myelodysplastic syndrome (MDS) complicated by refractoriness to platelet transfusion and intracerebral hemorrhage, who underwent allogeneic bone marrow transplantation from an HLA-identical unrelated male donor. Nine days before the scheduled transplantation, she developed dysarthria and right hemiparesis; computed tomography (CT) of the brain disclosed an acute hematoma in the left parietal lobe exceeding 3 cm in diameter. She underwent conditioning with reduced-intensity, including fludarabine (30 mg/m2/day on days -8 to -3), busulfan (4 mg/kg/day on days -6 and -5), and total body irradiation (4 Gy on day -2). Two weeks after transplantation, dysarthria and right hemiparesis began to resolve, and CT showed spontaneous resolution of the hematoma. Simultaneously, engraftment was confirmed. Thus, recent stroke may be not an absolute contraindication for HSCT.

Induction of granulocyte colony-stimulating factor mRNA by focal cerebral ischemia and cortical spreading depression

Granulocyte colony-stimulating factor (G-CSF) is a hematopoietic growth factor with neuroprotective and antiinflammatory properties. By real-time polymerase chain reaction we show that G-CSF transcripts are induced 485-fold at 4 h and 65-fold at 16 h in ischemic lesions after middle cerebral artery occlusion compared to control brains. Further analysis in photochemically induced focal ischemia revealed that G-CSF induction involved both the infarct area and remote nonischemic brain regions. Remote responses could be blocked by the noncompetitive NMDA receptor antagonist MK-801, suggesting periinfarct depolarizations as a trigger. To further confirm this notion, cortical spreading depression (CSD) was induced by focal application of KCl to the brain surface. CSD led to a 90-fold increase in G-CSF mRNA. Contrastingly, the induction of granulocyte-monocyte (GM)-CSF, another member of the hematopoietic growth factor family, was only moderate (sixfold) and restricted to ischemic brain lesions. In conclusion, G-CSF induction in the brain may be part of an intrinsic stress response aimed at limitation of neuronal damage.

Stroke and neurodegenerative disorders. 1. acute stroke evaluation, management, risks, prevention, and prognosis11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated

This self-directed learning module highlights recent developments in the acute care of stroke patients, prediction of outcome after stroke, evaluation of risk factors, secondary prevention of stroke, and the evaluation of the young adult with stroke. It is part of the study guide on stroke and neurodegenerative disorders in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article contains sections on the acute evaluation and management of the stroke patient, prediction of functional outcome after stroke, and secondary prevention of stroke. Special emphasis is given to the evaluation of the young adult with stroke.

OVERALL ARTICLE OBJECTIVES

(a) To summarize the acute evaluation and management of stroke, particularly in the young stroke patient; and (b) to review the risk factors for stroke and secondary prevention measures.