Tissue plasminogen activator followed by antioxidant-loaded nanoparticle delivery promotes activation/mobilization of progenitor cells in infarcted rat brain

Abstract

Inherent neuronal and circulating progenitor cells play important roles in facilitating neuronal and functional recovery post stroke. However, this endogenous repair process is rather limited, primarily due to unfavorable conditions in the infarcted brain involving reactive oxygen species (ROS)-mediated oxidative stress and inflammation following ischemia/reperfusion injury. We hypothesized that during reperfusion, effective delivery of antioxidants to ischemic brain would create an environment without such oxidative stress and inflammation, thus promoting activation and mobilization of progenitor cells in the infarcted brain. We administered recombinant human tissue-type plasminogen activator (tPA) via carotid artery at 3 h post stroke in a thromboembolic rat model, followed by sequential administration of the antioxidants catalase (CAT) and superoxide dismutase (SOD), encapsulated in biodegradable nanoparticles (nano-CAT/SOD). Brains were harvested at 48 h post stroke for immunohistochemical analysis. Ipsilateral brain slices from animals that had received tPA + nano-CAT/SOD showed a widespread distribution of glial fibrillary acidic protein-positive cells (with morphology resembling radial glia-like neural precursor cells) and nestin-positive cells (indicating the presence of immature neurons); such cells were considerably fewer in untreated animals or those treated with tPA alone. Brain sections from animals receiving tPA + nano-CAT/SOD also showed much greater numbers of SOX2- and nestin-positive progenitor cells migrating from subventricular zone of the lateral ventricle and entering the rostral migratory stream than in t-PA alone treated group or untreated control. Further, animals treated with tPA + nano-CAT/SOD showed far fewer caspase-positive cells and fewer neutrophils than did other groups, as well as an inhibition of hippocampal swelling. These results suggest that the antioxidants mitigated the inflammatory response, protected neuronal cells from undergoing apoptosis, and inhibited edema formation by protecting the blood-brain barrier from ROS-mediated reperfusion injury. A longer-term study would enable us to determine if our approach would assist progenitor cells to undergo neurogenesis and to facilitate neurological and functional recovery following stroke and reperfusion injury.

Antioxidant Nanotherapies for the Treatment of Inflammatory Diseases

“…In addition to the conventional small-molecule ROS scavengers, other biological agents, such as natural antioxidant enzymes SOD, CAT, and nucleic acids have been loaded into nanoparticles for anti-oxidative treatment (Kozower et al, 2003;Seshadri et al, 2010;Chen et al, 2013). Petro et al constructed poly (D,L-lactide co-glycolide) (PLGA) nanoparticles separately loaded with SOD, CAT, or their combination (Petro et al, 2016).…”

<p>Nanocarriers for Stroke Therapy: Advances and Obstacles in Translating Animal Studies</p>

“…This had resulted in the migration of neural progenitor cells (NPC) from the subventricular zone and more neurogenesis than the untreated controls and the controls receiving tPA only. 81 Drawing even further resemblances to liposomes, micelle drug delivery across the BBB could be enhanced by altering surface charge or conjugating ligands for specific interactions. One study developed drug-conjugated cationic bovine serum albumin (CBSA) micelles to augment crossing of the BBB, while another study had conjugated ligands onto micelle surfaces to bind to adenosine 2A receptors (A 2A R) on the BBB lumen to improve uptake.…”

Advanced Functional Materials and Cell‐Based Therapies for the Treatment of Ischemic Stroke and Postischemic Stroke Effects

“…Furthermore, a potential amelioration of inflammation by limiting the production of several proinflammatory cytokines can also be achieved . Both antioxidant substances, including curcumin, quercetin, and edaravone, as well as antioxidant enzymes (superoxide dismutase and catalase) were encapsulated inside polymer matrices and were used as curatives for cerebral ischemia. Their encapsulation inhibited limitations such as short half‐life, fast RES clearance, and nonspecific selectivity toward brain tissues, enhancing, as in the case of lipid‐based nanostructures, their therapeutic effect.…”

“…Their encapsulation inhibited limitations such as short half‐life, fast RES clearance, and nonspecific selectivity toward brain tissues, enhancing, as in the case of lipid‐based nanostructures, their therapeutic effect. In all the reported studies, these antioxidants resulted into a reduction of ROS and to therapeutic outcomes such as BBB preservation and reduction of neuroinflammation,33c activation and mobilization of progenitor stem cells, improved axonal remodeling, and inhibition of apoptosis with simultaneous induction of angiogenesis . It has to be noted that surface functionalization with specific moieties has also been performed.…”