Therapeutic hyaluronan-based hydrogel enables local drug delivery for recovery after stroke

Abstract

Event Abstract Back to Event Therapeutic hyaluronan-based hydrogel enables local drug delivery for recovery after stroke Anup Tuladhar1, 2, Cindi M. Morshead1, 2, 3 and Molly S. Shoichet1, 2, 4, 5 1 University of Toronto, Institute of Biomaterials and Biomedical Engineering, Canada 2 University of Toronto, Donnelly Centre for Cellular and Biomolecular Research, Canada 3 University of Toronto, Department of Surgery, Canada 4 University of Toronto, Department of Chemical Engineering and Applied Chemistry, Canada 5 University of Toronto, Department of Chemistry, Canada Introduction: Local drug delivery to the brain circumvents the blood-brain barrier preventing the use of many drugs to treat brain injury[1]. Unfortunately, the current clinical method causes further tissue damage due to cannula insertion into brain tissue and has an increased infection risk[2]. Our lab has developed a bioactive hydrogel for local drug delivery[3]. The gel, HAMC, is a physical blend of hyaluronan and methylcellulose. HAMC can be implanted onto the brain’s surface without damaging tissue. By mixing drug-loaded polymeric particles into the gel we can locally deliver drugs for several weeks[4]. Herein we investigate local delivery of two neuroactive drugs, cyclosporine (CsA) and erythropoietin (EPO), to stimulate motor recovery and tissue regeneration in stroke-injured rats. Materials and Methods: HAMC hydrogel (1.4wt% hyaluronan, 3wt% methylcellulose) was mixed with CsA-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles and injected it onto the ispilateral brain surface of rats with an endothelin-1 stroke. We measured CsA diffusion over time in dorsoventral brain sections using mass spectrometry. Next, we measured the effects of local CsA delivery from HAMC in the stroke-injured brain after 7 days. Tissue sections from untreated, CsA+HAMC treated and HAMC treated rats were stained for NeuN to determine stroke infarct size, Ki67 to determine cell proliferation in the neural stem/progenitor cell (NSPC) niche and DCX to count migratory neuronal progenitors[5]. Results and Discussion: Local delivery with HAMC successfully provided sustained CsA release to the brain for 14 days, with drug accumulation in the subcortical NSPC niche lining the lateral ventricles. Interestingly, the stroke infarct volume was reduced by HAMC alone compared to untreated controls (p<0.05), revealing a protective effect of the hydrogel (Fig.1). This is likely due to the anti-inflammatory effects of hyaluronan. CsA locally released from HAMC significantly increased the amount of proliferating cells in the NSPC niche relative to untreated controls (p<0.01) (Fig.2). While CsA-treated animals had a 1.6-fold increase in the number of neuronal progenitors relative to untreated and HAMC-only treated animals, no statistically significant differences were found due to large variability. Figure 1. Stroke infarct volume is reduced by hyaluronan-based hydrogel (n=4-5, *p<0.05) Figure 2. Local CsA delivery from HAMC increased the amount of Ki67+ proliferating cells in the lateral ventricles of stroke-injured rats (n=5-7, **p<0.01) To promote motor recovery in stroke-injured rats, the co-delivery of CsA with EPO will be studied. CsA has been shown to stimulate endogenous NSPCs and EPO has been shown to promote neurogenesis in a stroke injury model. In ongoing studies, we are studying the drug release and motor function of stroke-injured rats treated with our local delivery strategy. Conclusions: Local drug delivery to the brain can be achieved using HAMC hydrogel. The gel alone was sufficient to significantly reduce injury after stroke. We showed that sustained CsA delivery to subcortical regions of the brain, in particular the NSPC niche, was possible. Drug accumulation in this niche was sufficient to stimulate endogenous NSPCs in the injured brain. Ongoing work combines local CsA and EPO delivery to promote motor recovery and tissue regeneration in stroke-injured animals. Canadian Institute for Health Research; Ontario Graduate Scholarship; CIHR Training Program in Regenerative Medicine; Heart and Stroke Foundation