Stroke and related vascular events can cause widespread damage to the central nervous system (CNS) and result in significant motor and cognitive impairments. It has been suggested that trophic factor treatment may reduce the extent of damage and restore damaged neurons following the injury. We have previously tested the effects of bone morphogenetic protein-7 (BMP-7), a member of the transforming growth factor-B superfamily of growth factors, in focal brain ischemic injury. We found BMP-7 to have profound neuroprotective effects after intraventricular administration. We have now proceeded to test its distribution in the ischemic brain, in order to determine how rapidly BMP-7 may diffuse through brain parenchyma. We also determined whether it has effects on expression of intermediate filaments in neurons short-term after the injury as a partial basis for its restorative activity. Finally we examined effects on motor behavior after stroke. Adult male Sprague-Dawley rats were subjected to a 60-minute occlusion of the right middle cerebral artery, and 24 hours thereafter, injections of BMP-7 or vehicle into the lateral ventricle on the ipsilateral side, at a dose of 25 ul (1 ug/ul), were performed. The animals were sacrificed 1, 3, 6, and 24 hours following the BMP-7 administration. In terms of localization in the brain parenchyma, we found that BMP-7 was mostly present in the ependyma 1 hour following injection, while it extended to a few adjacent neurons at 3 hours post-injection. However, the 6- and 24-hour groups both had significant BMP-7-immunoreactive labeling in neurons, primarily in the striatum and thalamus. Neurofilament expression appeared to be fairly weak on the injected side in animals that had received the vehicle injection, whereas a significant upregulation in neurofilament staining was observed at 6- and 24 hours post-injection of BMP-7. Significant neurite outgrowth, with obvious growth cones, was observed at 24 hours, particularly in the ventral striatum and accumbens. These results suggest that BMP-7 injection may aid in the expression of intermediate neuronal filaments following an ischemic injury, and furthermore that the injected factor can become incorporated into neurons located several millimeters from the lateral ventricle. Adult Sprague-Dawley rats were anesthetized with chloral hydrate. The middle cerebral artery (MCA) was transiently occluded by a filament, inserted through the right internal carotid artery. The filament was removed after 60-min ischemia to allow reperfusion. Some animals were killed 24 hours after MCA occlusion (MCAo) to examine BMP-7 mRNA expression. Other animals received a single dose of intravenous BMP-7 or vehicle at 24 hours after MCA occlusion and were used for subsequent behavioral studies and BMP-7 immunostaining. BMP-7 mRNA was upregulated 24 hours after MCAo in non-treated animals. BMP-7-immunoreactivity was dose-dependently increased on the ischemic side hippocampus/dentate on the 6th day after MCAo in animals receiving intravenous injection of BMP-7. Animals receiving BMP-7 also showed a decrease in body asymmetry from days 7 to day 14 and an increase in locomotor activity on day 14 after MCAo. Our data indicate that BMP-7, given parenterally after stroke, can pass through the blood brain barrier on the ischemic side and induce behavioral recovery in stroke animals at longer testing times.
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