Marc F. Charette

Delayed Treatment with Intravenous Basic Fibroblast Growth Factor Reduces Infarct Size following Permanent Focal Cerebral Ischemia in Rats

Basic fibroblast growth factor (bFGF) is a polypeptide that supports the survival of brain cells (including neurons, glia, and endothelia) and protects neurons against a number of toxins and insults in vitro. This factor is also a potent dilator of cerebral pial arterioles in vivo. In previous studies, we found that intraventricularly administered bFGF reduced infarct volume in a model of focal cerebral ischemia in rats. In the current study, bFGF (45 μg/kg/h) in vehicle, or vehicle alone, was infused intravenously for 3 h, beginning at 30 min after permanent middle cerebral artery occlusion by intraluminal suture in mature Sprague–Dawley rats. After 24 h, neurological deficit (as assessed by a 0- to 5-point scale, with 5 = most severe) was 2.6 ± 1.0 in vehicle-treated and 1.5 ± 1.3 in bFGF-treated rats (mean ± SD; TV = 12 vs. 11; p = 0.009). Infarct volume was 297 ± 65 mm3 in vehicle- and 143 ± 135 mm3 in bFGF-treated animals (p = 0.002). During infusion, there was a modest decrease in mean arterial blood pressure but no changes in arterial blood gases or core or brain temperature in bFGF-treated rats. Autoradiography following intravenous administration of 111In-labeled bFGF showed that labeled bFGF crossed the damaged blood–brain barrier to enter the ischemic (but not the nonischemic) hemisphere. Whether the infarct-reducing effects of bFGF depend on intraparenchymal or intravascular mechanisms requires further study.

Intracisternal osteogenic protein-1 enhances functional recovery following focal stroke

OSTEOGENIC protein-1 (OP-1, BMP-7) is a member of the transforming growth factor-β(TGF-β) superfamily that selectively induces dendritic outgrowth from cultured neurons. We injected human recombinant OP-1 (1 or 10 μg) or vehicle into the cisterna magna of mature male Sprague—Dawley rats 1 and 4 days after focal cerebral infarction induced by middle cerebral artery (MCA) occlusion. OP-1 treatment was associated with a marked enhancement of recovery of sensorimotor function of the impaired forelimb and hindlimb (contralateral to infarcts) as assessed by limb placing tests. This effect appeared to be dose dependent. There was no difference in infarct volume between OP-1 and vehicle-treated rats. The mechanisms of enhanced recovery by intracisternal OP-1 may include promotion of dendritic sprouting in the intact uninjured brain.

Delayed intravenous administration of basic fibroblast growth factor (bFGF) reduces infarct volume in a model of focal cerebral ischemia/reperfusion in the rat

Basic fibroblast growth factor (bFGF) is a potent neurotrophic and vasoactive peptide. Previous studies have shown that intraventricularly-administered bFGF reduces the size of cerebral infarcts following focal ischemia. In the current study, we tested the effects of intravenously-administered bFGF in a model of focal ischemia/reperfusion. The right middle cerebral artery of mature male Wistar rats was occluded by intraluminal suture. After 2 h of occlusion, the suture was removed and intravenous infusion of bFGF in vehicle (45 micrograms/kg/h) or vehicle alone was begun, lasting 3 h. Animals were weighed and evaluated neurologically until sacrifice 7 days after ischemia. The volume of cerebral infarcts was then determined by H and E staining and image analysis. We found a 40% reduction in infarct volume in bFGF- vs. vehicle-treated rats (n = 11 vs. 11, P < 0.05). Reduction in infarct volume was associated with improved neurological outcome and regained body weight in bFGF-treated animals (both P < 0.05). No change in blood pressure was found during bFGF treatment. These results show that the delayed intravenous administration of bFGF reduces infarct size in this model of focal ischemia/reperfusion. The mechanisms of infarct reduction may include direct cytoprotective and/or vasoactive effects.

Time window of intracisternal osteogenic protein-1 in enhancing functional recovery after stroke.

Osteogenic protein-1 (OP-1, BMP-7) is a member of the bone morphogenetic protein subfamily of the TGF-ss superfamily that selectively stimulates dendritic neuronal outgrowth. In previous studies, we found that the intracisternal injection of OP-1, starting at one day after stroke, enhanced sensorimotor recovery of the contralateral limbs following unilateral cerebral infarction in rats. In the current study, we further explored the time window during which intracisternal OP-1 enhances sensorimotor recovery, as assessed by limb placing tests. We found that intracisternal OP-1 (10 microg) given 1 and 3 days, or 3 and 5 days, but not 7 and 9 days after stroke, significantly enhanced recovery of forelimb and hindlimb placing. There was no difference in infarct volume between vehicle- and OP-1-treated animals. The mechanism of OP-1 action might be stimulation of new dendritic sprouting in the remaining uninjured brain.

POTENTIATING INTERACTIONS BETWEEN MORPHOGENETIC PROTEIN AND NEUROTROPHIC FACTORS IN DEVELOPING NEURONS

mRNA for bone morphogenetic protein receptor type II (BMPR‐II) was mapped to different neurons in peripheral ganglia and spinal cord of the chicken embryo. The expression of this serine/threonine kinase receptor partially overlaps with that of tyrosine kinase receptors Trk and Ret. Biological activities of osteogenic protein‐1 (OP‐1), a documented ligand for BMPR‐II, were tested in explanted embryonic chicken ganglia and dissociated ganglionic neurons. OP‐1 had only a limited stimulatory effect on neuronal survival. However, OP‐1 combined with either neurotrophin‐3 (NT‐3, a relative of nerve growth factor) or glial cell line–derived neurotrophic factor (GDNF) potentiated neuronal survival three‐ to fourfold. We also show that OP‐1 strongly potentiates nerve fiber outgrowth from ganglia stimulated with NT‐3 or GDNF. Signaling by BMPR‐II in neurons may potentiate the tyrosine kinase pathway activated by NT‐3 and GDNF. The data suggest that morphogenetic proteins may modulate neurotrophic activities during neuronal development and plasticity. J. Neurosci. Res. 53:559–568, 1998.

BMPR-II expression and OP-1 effects in developing chicken retinal explants

Low-Stringency PCR was used to isolate the chicken homologue of the human bone morphogenetic protein receptor type II (BMPR-II). In situ hybridization localized mRNA expression for this serine/threonine kinase receptor. It was weakly expressed in the vitreal side of the neural retina at E6. In the E7 chicken, fairly strong labelling was found in cells of the internal part of the neural retina. At E9, strong labelling was found in the region of the retinal ganglion cells. Explants of E6 retina exposed to osteogenic protein-1 (OP-1/BMP-7), exhibited dense retinal fibre outgrowth. This suggests that BMPR-II may form a signalling receptor complex important for retinal development. OP-1 and related ligands may serve functions supplementary to those of neurotrophins.