Introduction: Activation of inflammatory cascades after stroke exacerbate acute injury and limit response to rehabilitation (rehab). The complement (C) system is a prominent component of inflammatory injury after stroke, but can also contribute to neuroprotective recovery processes. We investigated the neuroprotective effects of CR2fH, a site-targeted C inhibitor that specifically inhibits the alternative pathway and prevents amplification of the C cascade. We assessed how CR2fH affects chronic outcomes, and how acute C inhibition impacts the response to rehab therapy.
Methods: Mice were subjected to 1hr middle cerebral artery occlusion and 15 days of reperfusion. Mice were treated with CR2fH or vehicle and then randomized to normal housing or an enriched environment (EE) to model cognitive and motor rehab. Animals were assessed for infarct volume using MRI at days 4 and 14 after injury, and for their performance on several motor and cognitive tasks. Expression of inflammatory markers in the brain was assessed using high throughput Nanostring analysis and immunostaining.
Results: Compared to vehicle or EE only, treatment with CR2fH 90 mins after cerebral ischemia significantly reduced infarct volume and improved motor and cognitive performance up to 15 days, as assessed with mNSS scores, corner task, locomotor activity, pasta handling, and passive avoidance tasks (p’s<0.01). Less prominent, although still significant improvement was also achieved when CR2fH was administered 6 or 12 hrs. after ischemia (p’s<0.05). EE alone did not significantly reduce infarct volume or improve performance on motor tasks, but resulted in a significant improvement in cognitive performance compared to vehicle (p’s<0.05). A combination of EE and CR2fH therapy resulted in a significant potentiation of cognitive and motor recovery compared to either single intervention (p’s<0.05). CR2fH related behavioral improvements correlated with reduction in C deposition and inflammatory microglial activation during recovery.
Conclusions: Since a humanized version of CR2fH, TT30, was shown to be safe, tolerated and nonimmunogenic in humans, targeted inhibition of alternative C pathway is a candidate therapy to promote recovery and potentiate response to rehab after stroke.