Mitochondria-containing extracellular vesicles from mouse vs . human brain endothelial cells for ischemic stroke therapy

Ischemic stroke-induced mitochondrial dysfunction in the blood-brain barrier-forming brain endothelial cells ( BECs ) results in long-term neurological dysfunction post-stroke. We previously reported that intravenous administration of human BEC ( hBEC )-derived mitochondria-containing extracellular vesicles ( EVs ) showed a potential efficacy signal in a mouse middle cerebral artery occlusion ( MCAo ) model of stroke. We hypothesized that EVs harvested from donor species homologous to the recipient species ( e.g., mouse) may improve therapeutic efficacy, and therefore, use of mouse BEC ( mBEC )-derived EVs may improve post-stroke outcomes in MCAo mice. We investigated if EVs derived from the same species as the recipient cell (mBEC-EVs and recipient mBECs or hBECs-EVs and recipient hBECs) show a greater EV mitochondria delivery efficiency than cross-species EVs and recipient cells (mBEC-EVs and recipient hBECs or vice versa ). Our results showed that mBEC-EVs outperformed hBEC-EVs in transferring EV mitochondria to the recipient ischemic mBECs, and improved mBEC mitochondrial function via increasing oxygen consumption rate. mBEC-EVs significantly reduced brain infarct volume and improved behavioral recovery compared to vehicle-injected MCAo mice. Our data suggests that mBEC-EVs show superior therapeutic efficacy in a mouse MCAo stroke model compared to hBEC-EVs-supporting the continued use of mBEC-EVs to optimize the therapeutic potential of mitochondria-containing EVs in preclinical studies.

Heterochronic Parabiosis Causes Dacryoadenitis in Young Lacrimal Glands

Aging is associated with inflammation and oxidative stress in the lacrimal gland (LG). We investigated if heterochronic parabiosis of mice could modulate age-related LG alterations. In both males and females, there were significant increases in total immune infiltration in isochronic aged LGs compared to that in isochronic young LGs. Male heterochronic young LGs were significantly more infiltrated compared to male isochronic young LGs. While both females and males had significant increases in inflammatory and B-cell-related transcripts in isochronic and heterochronic aged LGs compared to levels isochronic and heterochronic young LGs, females had a greater fold expression of some of these transcripts than males. Through flow cytometry, specific subsets of B cells were increased in the male heterochronic aged LGs compared to those in male isochronic aged LGs. Our results indicate that serum soluble factors from young mice were not enough to reverse inflammation and infiltrating immune cells in aged tissues and that there were specific sex-related differences in parabiosis treatment. This suggests that age-related changes in the LG microenvironment/architecture participate in perpetuating inflammation, which is not reversible by exposure to youthful systemic factors. In contrast, male young heterochronic LGs were significantly worse than their isochronic counterparts, suggesting that aged soluble factors can enhance inflammation in the young host. Therapies that aim at improving cellular health may have a stronger impact on improving inflammation and cellular inflammation in LGs than parabiosis.

Middle Cerebral Artery Occlusion in Aged Animal Model

Stroke is a devastating brain injury resulting in high mortality and substantial loss of function, affecting >15 million people worldwide annually; the majority of which are over 65 years old (Feigin et al., Lancet 383:245-254, 2014; Feigin et al., Lancet Neurol 2:43-53, 2003; Benjamin et al., Circulation 135:e146-e603, 2017; Writing Group et al., Circulation 133:447-454, 2016; Roy-O'Reilly, McCullough, Endocrinology 159:3120-3131, 2018). Aging is a significant risk factor for stroke, and older patients have higher mortality and poorer functional recovery after stroke compared with younger patients (Arboix et al., J Am Geriatr Soc 48:36-41, 2000; Rojas et al., Eur J Neurol 14:895-899, 2007). Despite the importance of aging in the pathophysiology of stroke, the vast majority of preclinical studies have only used young animals. Understanding the mechanisms underlying stroke-induced brain damage and post-stroke functional recovery in aged animals is an urgent need. This step is essential to the development of therapeutics for treating stroke patients, most of whom are elderly. To understand the pathophysiology of ischemic injury induced by middle cerebral artery occlusion (MCAO), one of the most common type of stroke seen clinically (Writing Group et al., Circulation 133:e38-360, 2016), it is imperative to include older animals in preclinical testing. The purpose of this chapter is to provide insight on successfully reproducing MCAO injury in translationally relevant aged animals.

Abstract WMP114: Changes In Gut Microbiome Precede Cognitive Impairment In A Mouse Model Of Vascular Cognitive Impairment And Dementia

Introduction: Vascular cognitive impairment (VCI) is the second most common cause of clinical dementia after Alzheimer’s disease. VCI results from injury to the cerebral blood vessels. Cerebral perfusion is diminished in elderly individuals and additional reduction of cerebral blood flow increases the risk of developing VCI. These findings have been successfully modeled in mice with bilateral common carotid artery stenosis (BCAS). Age is associated with gut dysbiosis and transplantation of aged microbiome leads to cognitive decline in young animals. However, there are large gaps in our understanding of the molecular mechanisms induced by chronic hypoperfusion contributes to impaired cognitive function.

Methods: C57Bl6 aged (~18m) male mice were subjected to a sham or a BCAS surgery using 0.18mm titanium coils placed on both common carotid arteries. Mice were followed for 90d after surgery to assess both gut microbial content and behavioral changes. 16S ribosomal RNA (rRNA) sequencing analysis was performed on fecal samples collected from aged baseline, sham and BCAS animals at 7 and 28 days. Cognition was assessed using Y-maze. Tissues were collected at the time of euthanasia for metabolomics and histological analysis.

Results: BCAS resulted in significant reduction of cerebral blood flow, measured using laser speckle (p<0.05; n=4/grp; t test). 16s rRNA analysis revealed BCAS led to a remarkable shift in bacterial diversity as early as day 7 in aged male mice, measured by using unweighted UniFrac analysis. These differences remained significant (p<0.05; n=4/grp) in BCAS compared to sham mice on day 28. In depth analysis revealed significant changes at the genus level between both groups. Interestingly, BCAS mice did not show significant difference in Y-maze at day 14, but significant cognitive impairment was found at day 90 compared to sham mice (n=8-9/grp).

Conclusions: We found that chronic cerebral hypoperfusion is associated with significant changes in gut microbiome and cognitive impairment in aged mice. Importantly, shifts in the microbiome preceded cognitive decline. These findings suggest that targeting these detrimental changes in the gut microbiome might be a novel therapeutic strategy to delay or prevent progression of VCI.

Mitochondria-containing extracellular vesicles (EV) reduce mouse brain infarct sizes and EV/HSP27 protect ischemic brain endothelial cultures

Ischemic stroke causes brain endothelial cell (BEC) death and damages tight junction integrity of the blood-brain barrier (BBB). We harnessed the innate mitochondrial load of BEC-derived extracellular vesicles (EVs) and utilized mixtures of EV/exogenous 27 kDa heat shock protein (HSP27) as a one-two punch strategy to increase BEC survival (via EV mitochondria) and preserve their tight junction integrity (via HSP27 effects). We demonstrated that the medium-to-large (m/lEV) but not small EVs (sEV) transferred their mitochondrial load, that subsequently colocalized with the mitochondrial network of the recipient primary human BECs. Recipient BECs treated with m/lEVs showed increased relative ATP levels and mitochondrial function. To determine if the m/lEV-meditated increase in recipient BEC ATP levels was associated with m/lEV mitochondria, we isolated m/lEVs from donor BECs pre-treated with oligomycin A (OGM, mitochondria electron transport complex V inhibitor), referred to as OGM-m/lEVs. BECs treated with naïve m/lEVs showed a significant increase in ATP levels compared to untreated OGD cells, OGM-m/lEVs treated BECs showed a loss of ATP levels suggesting that the m/lEV-mediated increase in ATP levels is likely a function of their innate mitochondrial load. In contrast, sEV-mediated ATP increases were not affected by inhibition of mitochondrial function in the donor BECs. Intravenously administered m/lEVs showed a reduction in brain infarct sizes compared to vehicle-injected mice in a mouse middle cerebral artery occlusion model of ischemic stroke. We formulated binary mixtures of human recombinant HSP27 protein with EVs: EV/HSP27 and ternary mixtures of HSP27 and EVs with a cationic polymer, poly (ethylene glycol)-b-poly (diethyltriamine): (PEG-DET/HSP27)/EV. (PEG-DET/HSP27)/EV and EV/HSP27 mixtures decreased the paracellular permeability of small and large molecular mass fluorescent tracers in oxygen glucose-deprived primary human BECs. This one-two punch approach to increase BEC metabolic function and tight junction integrity may be a promising strategy for BBB protection and prevention of long-term neurological dysfunction post-ischemic stroke.

Abstract 105: Sex Differences In The Response To Global Cerebral Hypo-Perfusion In A Mouse Model Of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a disease of small and medium-sized vessels, characterized by amyloid deposition. The incidence of CAA increases with age and evidence reveals worsened cognition in females compared to males. Cerebral hypoperfusion, or a decrease in cerebral blood flow (CBF), changes the integrity of the blood brain barrier and contributes to microhemorrhages, cerebral atrophy, and white matter loss. However, the link between vascular amyloid deposition and hypoperfusion remains understudied. We induced global cerebral hypoperfusion with bilateral carotid artery stenosis (BCAS) in CAA mice of both sexes and examined cognitive deficits, white matter loss, and cerebral gliosis. We hypothesize that chronic cerebral hypoperfusion will accelerate cognitive decline in CAA, increase white matter damage, and induce gliotic changes in the brain.Using a mouse model of CAA (Tg-SwDI), male and female mice (3 months of age) were randomized to either BCAS (n=15) or sham (n=11) surgery using 0.18mm coils to induce global cerebral hypoperfusion. Cognitive (Y-maze (YM), NORT, Water Maze (WM)) and motor function (Open Field (OF)) testing was performed by a blinded investigator prior to surgery (baseline) and at regular intervals until tissue harvest 6 months post-BCAS (PB). The brain and brainstem were harvested for immunohistochemical (IHC) analysis (Kluver-Barrera (KB), Iba-1, GFAP, Myelin Basic Protein (MBP)).Sex-specific changes in spatial memory (YM) and learning (NORT/WM) were present in BCAS mice. Female BCAS mice displayed greater deficits in cognition (NORT) at 3 (p=.0028), 4 (YM, p=.0007), and 5-months PB (NORT, p=.0149). Male BCAS mice demonstrated similar cognitive deficits, but at a later timepoint of 5 months PB (NORT, p=.0007). Both female and male BCAS mice had poorer cognition (WM) and motor function (OF, p=.0011/.0055) 6 months PB. IHC demonstrated increased demyelination (MBP) (p=.0038) and atrophy (KB) in the anterior corpus collosum (p=.0447) and significant gliosis (p=.0230).This study shows that chronic global hypoperfusion accelerates cognitive deficits in a CAA model, an effect that is accelerated in female mice. BCAS led to gliotic changes and demyelination associated with white matter damage in the brain.

Abstract TP170: Heterochronic Parabiosis Lowers Microglia Activation And Myeloid Infiltration In Aged Parabiont

Introduction: Of the 795,000 people who suffer strokes annually, 75% are over the age of 65. Aging is a major risk factor for stroke. The risk of stroke doubles every decade after the age of 55. Aging leads to dramatic changes in peripheral myeloid cells and increases the activation state of microglia in the brain. Although age is an important determinant of stroke susceptibility and outcome, the contribution from the aged immune system remains unclear.

Hypothesis: We hypothesize that aged mice (18-22 mo) parabionts paired with a young parabiont (2-3 mo) would have less microglia activation due to exposure to systemic factors from young mice when compared to aged mice paired with aged mice (18-22 mo).

Methods: Young Pep-boy mice (haplotype CD45.1) were surgically paired with aged mice (haplotype CD45.2) for two months. The brains of these mice were then subjected to flow cytometry analysis. Brain single cell suspensions were isolated and immunophenotyped with a microglia specific panel.

Results: Our results show that myeloid infiltration was decreased in the aged parabiont (paired with a young mouse) compared to its naïve counterpart (n=3-6/ grp, p = 0.0036). Microglia activation was assessed utilizing a homeostatic marker, P2RY12, and a microglia specific marker, Tmem119. Interestingly, the expression of Tmem119 on CD45 int CD11b + cells was significantly increased in the aged parabionts compared to aged, naïve mice (n=3-6/ grp, p =0.0006), however, P2RY12 trended upward in the aged parabiont (n=3/6 /grp, p =0.0742). This suggests that the shared circulation created between the heterochronic pair led to a reduction in immune activation in the aged parabiont. Thus, the young parabiont allows the aged parabiont access to rejuvenating factors through the shared flow of blood which reduced neuroinflammation.

Conclusion: Future studies are needed to identify the specific factors contributing to reduced microglial activation and lowered infiltration of peripheral immune cells induced by pairing with young animals. Studies examining the immune response to stroke in young and aged parabionts are needed.

Intra-arterial combination therapy for experimental acute ischemic stroke

Acute ischemic stroke continues to devastate millions of individuals worldwide. Current treatments work to restore blood flow but not rescue affected tissue. Our goal was to develop a combination of neuroprotective agents administered intra-arterially following recanalization to target ischemic tissue. Using C57Bl/6J male mice, we performed tandem transient ipsilateral middle cerebral/common carotid artery occlusion, followed by immediate intra-arterial pharmacotherapy administration through a standardized protocol. Two pharmacotherapy agents, verapamil and lubeluzole, were selected based on their potential to modulate different aspects of the ischemic cascade; verapamil, a calcium channel blocker, works in an acute fashion blocking L-type calcium channels, whereas lubeluzole, an N-methyl-D-aspartate modulator, works in a delayed fashion blocking intracellular glutamate trafficking. We hypothesized that combination therapy would provide complimentary and potentially synergistic benefit treating brain tissue undergoing various stages of injury. Physiological measurements for heart rate and pulse distention (blood pressure) demonstrated no detrimental effects between groups, suggesting that the combination drug administration is safe. Tissue analysis demonstrated a significant difference between combination and control (saline) groups in infarct volume, neuronal health, and astrogliosis. Although a significant difference in functional outcome was not observed, we did note that the combination treatment group had a greater percent change from baseline in forced motor movement as compared with controls. This study demonstrates the safety and feasibility of intra-arterial combination therapy following successful recanalization and warrants further study.

Sex differences in a murine model of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is one of the common causes of lobar intracerebral hemorrhage and vascular cognitive impairment (VCI) in the aging population. Increased amyloid plaque deposition within cerebral blood vessels, specifically the smooth muscle layer, is linked to increased cerebral microbleeds (CMBs) and impaired cognition in CAA. Studies in Alzheimer's disease (AD) have shown that amyloid plaque pathology is more prevalent in the brains of elderly women (2/3rd of the dementia population) compared with men, however, there is a paucity of studies on sex differences in CAA. The objective of this study was to discern the sexual dichotomies in CAA. We utilized male and female Tg-SwDI mice (mouse model of CAA) at 12-14 months of age for this study. We evaluated sex differences in CMBs, cognitive function and inflammation. Cognition was assessed using Y-maze (spatial working memory) and Fear Conditioning (contextual memory). CMBs were quantified by ex vivo brain MRI scans. Inflammatory cytokines in brain were quantified using ELISA. Our results demonstrated that aging Tg-SwDI female mice had a significantly higher burden of CMBs on MRI as compared to males. Interestingly, these aging Tg-SwDI female mice also had significantly impaired spatial and contextual memory on Y maze and Fear Conditioning respectively. Furthermore, female mice had significantly lower circulating inflammatory cytokines, IL-1α, IL-2, IL-9, and IFN-γ, as compared to males. Our results demonstrate that aging female Tg-SwDI mice are more cognitively impaired and have higher number of CMBs, as compared to males at 12-14 months of age. This may be secondary to reduced levels of neural repair cytokines (IL-1α, IL-2, IL-9 and IFN-γ) involved in sex specific inflammatory signaling in CAA.

Abstract MP17: Upregulating E2F1 Mitigates Senescence-Associated Phenotypes in Cultured Primary Endothelial Cells

Vascular contributions to cognitive impairment and dementia (VCID) includes multiple disorders that are identified by cognitive deficits secondary to cerebrovascular pathology. The risk of VCID is higher in people after the age of 70, and, currently, there is no effective treatment. Vascular endothelial cells (VEC) are critical components of the brain vasculature and neurovascular unit and their health is vital to the capacity of the brain vasculature to respond to stressors. However, aged VEC may enter an irreversible replicative-arrest state (senescence), which has been associated with dementia. E2F transcription factor 1 (E2F1) regulates cell cycle progression and DNA damage repair. Importantly, E2F1 deficiency is associated with cell senescence. We hypothesized that E2F1 downregulation contributes to senescence in the cerebral endothelium during aging. We used cultured primary VEC from young (4-months old, mo) and aged (18-mo) male and female mice for RNA sequencing, plasmid-based gene delivery, high-resolution microscopy, and (4-, 12-, and 18-mo) mice of the bilateral carotid artery stenosis (BCAS) model, which produces chronic cerebral hypoperfusion and recapitulates some of the features seen in patients with VCID. We found that overexpression of E2F1 reduced the levels of senescence-associated phenotypes in cultured VEC from young mice that were exposed to oxygen and glucose deprivation (p<0.001), which induces endothelial senescence. Our RNA seq data showed that the expression of E2f1 was reduced (~40%) in cultured primary VEC from aged mouse brains compared with young cells (p<0.001). E2F1 levels were reduced in the brains of aged mice. Interestingly, we found sex differences in E2F1 levels, with less protein levels (~30%) in males vs females (p<0.05), independently of age. Also, aged BCAS mice (1 month after surgery) had more severe senescence phenotypes, reduced cerebral blood flow, and worse memory deficits compared with control mice (p<0.05). The effect of BCAS was more prominent in aged mice compared with younger (4- and 12-mo) mice. In conclusion , our study identifies E2F1 as a potential regulator of endothelial senescence in mice and highlights the contribution of aging as an important factor in losing endothelial resilience.

Abstract P740: Late Effects of Bilateral Carotid Artery Stenosis in an Aged Mouse Model

Bilateral carotid artery stenosis (BCAS) or global hypoperfusion is an experimental model of vascular dementia known to effect cognition. Chronic global hypoperfusion increases astrogliosis within the cortex and hippocampus, leading to reduced cognition. It is unknown if global hypoperfusion leads to respiratory deficits that could contribute to cognitive decline. We hypothesized that chronic global hypoperfusion in cerebral blood flow will lead to brain stem gliosis, respiratory dysfunction and progressive cognitive impairment. Female C57Bl/6 mice aged 18 months underwent BCAS (n=8) or sham (n=8) surgery to investigate changes in respiration (frequency, tidal volume, apneas), cognition (y-maze-spatial working memory and fear conditioning-contextual working memory), and changes in cortical and brain stem astrogliosis. Results demonstrated BCAS mice had decreased respiratory frequency and apneas (p<0.05), decreased cognition in both spatial and contextual working memory (p<0.05), and increased astrogliosis (p<0.01) within the cortex and brain stem. To determine if increased astrogliosis within the cortex and brain stem contributes to changes in respiration and delayed cognitive deficits, we administered a TGF-β inhibitor (Gw788388 Hydrate) through an osmotic pump 7 days post-BCAS or sham surgery and followed the mice for 56 days post-surgery. Results demonstrated a reduction in periodic apneas (p<0.01), cognitive deficits (p<0.05), and amelioration in gliosis (p<0.01) when comparing BCAS and sham mice. In conclusion, this study demonstrated global hypoperfusion leads to disrupted respiratory function, late cognitive deficits, and increased brain stem gliosis, that can be rescued through administration of TGF-β inhibitor. Respiratory instability may contribute to post-stroke cognitive deficits, and could be a therapeutic target to improve outcomes in patients with vascular dementia.

Interleukin 1 alpha administration is neuroprotective and neuro-restorative following experimental ischemic stroke

Background

Stroke remains a leading cause of death and disability worldwide despite recent treatment breakthroughs. A primary event in stroke pathogenesis is the development of a potent and deleterious local and peripheral inflammatory response regulated by the pro-inflammatory cytokine interleukin-1 (IL-1). While the role of IL-1β (main released isoform) has been well studied in stroke, the role of the IL-1α isoform remains largely unknown. With increasing utilization of intravenous tissue plasminogen activator (t-PA) or thrombectomy to pharmacologically or mechanically remove ischemic stroke causing blood clots, respectively, there is interest in pairing successful cerebrovascular recanalization with neurotherapeutic pharmacological interventions (Fraser et al., J Cereb Blood Flow Metab 37:3531–3543, 2017; Hill et al., Lancet Neurol 11:942–950, 2012; Amaro et al., Stroke 47:2874–2876, 2016).

Methods

Transient stroke was induced in mice via one of two methods. One group of mice were subjected to tandem ipsilateral common carotid artery and middle cerebral artery occlusion, while another group underwent the filament-based middle cerebral artery occlusion. We have recently developed an animal model of intra-arterial (IA) drug administration after recanalization (Maniskas et al., J Neurosci Met 240:22–27, 2015). Sub groups of the mice were treated with either saline or Il-1α, wherein the drug was administered either acutely (immediately after surgery) or subacutely (on the third day after stroke). This was followed by behavioral and histological analyses.

Results

We now show in the above-mentioned mouse stroke models (transient tandem ipsilateral common carotid artery (CCA) and middle cerebral artery occlusion (MCA) occlusion, MCA suture occlusion) that IL-1α is neuroprotective when acutely given either intravenously (IV) or IA at low sub-pathologic doses. Furthermore, while IV administration induces transient hemodynamic side effects without affecting systemic markers of inflammation, IA delivery further improves overall outcomes while eliminating these side effects. Additionally, we show that delayed/subacute IV IL-1α administration ameliorates functional deficit and promotes neurorepair.

Conclusions

Taken together, our present study suggests for the first time that IL-1α could, unexpectedly, be an effective ischemic stroke therapy with a broad therapeutic window.

Transforming growth factor-β promotes basement membrane fibrosis, alters perivascular cerebrospinal fluid distribution, and worsens neurological recovery in the aged brain after stroke

Aging and stroke alter the composition of the basement membrane and reduce the perivascular distribution of cerebrospinal fluid and solutes, which may contribute to poor functional recovery in elderly patients. Following stroke, TGF-β induces astrocyte activation and subsequent glial scar development. This is dysregulated with aging and could lead to chronic, detrimental changes within the basement membrane. We hypothesized that TGF-β induces basement membrane fibrosis after stroke, leading to impaired perivascular CSF distribution and poor functional recovery in aged animals. We found that CSF entered the aged brain along perivascular tracts; this process was reduced by experimental stroke and was rescued by TGF-β receptor inhibition. Brain fibronectin levels increased with experimental stroke, which was reversed with inhibitor treatment. Exogenous TGF-β stimulation increased fibronectin expression, both in vivo and in primary cultured astrocytes. Oxygen-glucose deprivation of cultured astrocytes induced multiple changes in genes related to astrocyte activation and extracellular matrix production. Finally, in stroke patients, we found that serum TGF-β levels correlated with poorer functional outcomes, suggesting that serum levels may act as a biomarker for functional recovery. These results support a potential new treatment strategy to enhance recovery in elderly stroke patients.

Abstract TMP35: Perivascular Astrocytes Alter the Basement Membrane Through TGF-Beta in an Aged Brain Post-Stroke

Individuals over 65 make up the majority of stroke patients in the United States. Post-stroke recovery within the elderly population maybe impeded through enhanced glial scarring and reduced glymphatic flow. Following stroke, reactive astrocytes remodel the basement membrane through transforming growth factor-beta (B) signaling (TGF-B), altering glymphatic flow. Impaired glymphatic flow leads to a buildup of waste products, such as amyloid-beta, further inhibiting post-stroke recovery.

We hypothesize that post-stroke astrogliosis and basement membrane fibrosis are induced through TGF-B signaling, resulting in chronic glymphatic impairment in aged mice. To test this hypothesis, we used an in vivo model of ischemia to measure TGF-B signaling and reactive astrogliosis. In vivo studies used young (3 month, n=5-8) and aged (20-month, n=5-8) male C57/Bl6 mice that underwent distal middle cerebral artery occlusion (DMCAO). Outcome measurements included TGF-B signaling, reactive astrogliosis within the glymphatic system, and impaired glymphatic flow. As a potential therapy, an implantable subcutaneous osmotic pump was inserted post-stroke with a TGF-B antagonist (GW788388 Hydrate-10mg/kg/day) to determine the impact on astrogliosis, glymphatic flow, and functional outcome. Results for in vivo studies using immunohistochemistry demonstrated a significant increase (p<0.05) in TGF-B expression in aged sham/DMCAO compared to young sham/DMCAO. There was a significant (p<0.01) increase in astrogliosis in aged sham/DMCAO compared to young sham/DMCAO. Glymphatic flow was assessed using an injected dextran dye, results demonstrated a significant (p<0.05) reduction in glymphatic flow for aged DMCAO compared to naïve mice. Functional measurements demonstrated that aged DMCAO had a significant reduction (p<0.05) in Paw Area/Time (Digigait) compared to naïve. Following TGF-B antagonist treatment, there was no difference between aged DMCAO and naïve mice in astrogliosis, glymphatic flow, or Paw Area/Time. This demonstrates that TGF-B impairs post-stroke recovery through astrogliosis, and impaired glymphatic flow. While this study demonstrated positive effects post-stroke, future studies should target downstream pathways of TGF-B.

Abstract TP95: Intra-arterial Interleukin-1 alpha is Well Tolerated and Neuroprotective After Experimental Ischemic Stroke

Endovascular thrombectomy combined with t-PA is the current standard of care for emergent large vessel occlusion (ELVO) stroke. Unfortunately, despite rising recanalization rates, stroke remains the leading cause of long-term disability worldwide suggesting that additional therapies are needed. Severe stroke morbidity may be due, partially, to the acute and sustained inflammatory stroke response. Preclinical research has shown some promise with anti-inflammatory agents in limiting brain injury and improving functional outcome; however, the post-stroke inflammatory cascade appears to have both beneficial and deleterious effects making the translation of such anti-inflammatory approaches perilous. We aim to show that the inflammatory cytokine interleukin-1alpha (IL-1α) is well-tolerated, neuroprotective, and conveys functional benefit after ischemic stroke. 3-month-old C57/BL6 mice were subjected to MCAo and given IL-1α via IV injection or IA infusion upon recanalization. Mice were allowed to recover for 7 days before sacrifice. Brains were flash frozen for IHC and serum for high sensitivity ELISA. We noted that IV IL-1α (1 ng) is neuroprotective (as measured by cresyl violet stained infarct volumes) and significantly improved functional recovery in open field behavioral tests. When given IV, IL-1α showed transient hemodynamic side effects that are typical of IL-1α’s known physiologic functions (fever, sterile inflammation, etc.) These effects are short lived with systemic (IV) administration and IA IL-1α (0.1 ng) administration showed neuroprotection without the side effects seen with IV treatment. Additionally, we noted that IL-1α is directly neuroprotective of primary mouse cortical neurons exposed to oxygen and glucose deprivation conditions in vitro . IL-1α’s profound, direct neuroprotective effects and its functional benefit, make IL-1α an attractive target for future study in ischemic stroke.

Internal carotid artery stenosis: A novel surgical model for moyamoya syndrome

Moyamoya is a cerebrovascular disorder characterized by progressive stenosis of the intracranial internal carotid arteries. There are two forms: Disease and Syndrome, with each characterized by the sub-population it affects. Moyamoya syndrome (MMS) is more prominent in adults in their 20's-40's, and is often associated with autoimmune diseases. Currently, there are no surgical models for inducing moyamoya syndrome, so our aim was to develop a new animal model to study this relatively unknown cerebrovascular disease. Here, we demonstrate a new surgical technique termed internal carotid artery stenosis (ICAS), to mimic MMS using micro-coils on the proximal ICA. We tested for Moyamoya-like vasculopathies by fluorescently labelling the mouse cerebrovasculature with Di I for visualization and analysis of vessel diameter at the distal ICA and anastomoses on the cortical surface. Results show a significant narrowing of the distal ICA and anterior cerebral artery (ACA) in the Circle of Willis, as observed in humans. There is also a significant decrease in the number of anastomoses between the middle cerebral artery (MCA) and the ACA in the watershed region of the cortex. While further characterization is needed, this ICAS model can be applied to transgenic mice displaying co-morbidities as observed within the Moyamoya syndrome population, allowing a better understanding of the disease and development of novel treatments.

Abstract TP101: Intra-arterial IL-1α is Well Tolerated and Neuroprotective After Experimental Ischemic Stroke

Endovascular thrombectomy and t-PA are the only current standard of care treatments for emergent large vessel occlusion (ELVO) stroke. Despite rising recanalization rates, stroke remains the leading cause of long-term disability worldwide suggesting that additional therapies are needed. Severe stroke morbidity may be due, in part, to the acute and sustained inflammatory stroke response. Preclinical research has supported anti-inflammatory agents in limiting brain injury and improving functional outcome; however, the post-stroke inflammatory cascade appears to have both beneficial and deleterious effects, necessitating careful therapeutic translation. We have recently demonstrated that delayed (3 day) post-stroke intravenous (IV) administration of the interleukin (IL)-1α (one of the two major isoforms of the pro-inflammatory family of cytokine IL-1), promoted, rather than suppressed, post-stroke angiogenesis in the transient middle cerebral artery occlusion (MCAo) mouse model. In this study, we aimed to show a therapeutic efficacy of IL-1α in neuroprotection. We investigated the potential for IL-1α, administered acutely IV or intra-arterial (IA) (n=5) after mouse MCAo, to also be neuroprotective. We noted that IV IL-1α (1 ng) is neuroprotective (as measured by cresyl violet stained infarct volumes) with mild, transient side effects (blunted hypertension and bradycardia) that were well tolerated, and with better functional recovery in free motion behavioral tests. IA IL-1α (0.1 ng) administration was even more neuroprotective without the systemic changes seen with IV treatment. Additionally, we noted that IL-1α is directly neuroprotective of primary mouse cortical neurons exposed to oxygen and glucose deprivation conditions in vitro . Taken together, these results suggest that IL-1α could be therapeutic after stroke when administered IV or IA, and the latter may eliminate potentially harmful hemodynamic side effects.

Intra-arterial nitroglycerin as directed acute treatment in experimental ischemic stroke

BACKGROUND

Nitroglycerin (also known as glyceryl trinitrate (GTN)), a vasodilator best known for treatment of ischemic heart disease, has also been investigated for its potential therapeutic benefit in ischemic stroke. The completed Efficacy of Nitric Oxide in Stroke trial suggested that GTN has therapeutic benefit with acute (within 6 hours) transdermal systemic sustained release therapy.

OBJECTIVE

To examine an alternative use of GTN as an acute therapy for ischemic stroke following successful recanalization.

METHODS

We administered GTN IA following transient middle cerebral artery occlusion in mice. Because no standard dose of GTN is available following emergent large vessel occlusion, we performed a dose-response (3.12, 6.25, 12.5, and 25 µg/µL) analysis. Next, we looked at blood perfusion (flow) through the middle cerebral artery using laser Doppler flowmetry. Functional outcomes, including forced motor movement rotor rod, were assessed in the 3.12, 6.25, and 12.5 µg/µL groups. Histological analysis was performed using cresyl violet for infarct volume, and glial fibrillary activating protein (GFAP) and NeuN immunohistochemistry for astrocyte activation and mature neuron survival, respectively.

RESULTS

Overall, we found that acute post-stroke IA GTN had little effect on vessel dilatation after 15 min. Functional analysis showed a significant difference between GTN (3.12 and 6.25 µg/µL) and control at post-stroke day 1. Histological measures showed a significant reduction in infarct volume and GFAP immunoreactivity and a significant increase in NeuN.

CONCLUSIONS

These results demonstrate that acute IA GTN is neuroprotective in experimental ischemic stroke and warrants further study as a potentially new stroke therapy.

Stroke neuroprotection revisited: Intra-arterial verapamil is profoundly neuroprotective in experimental acute ischemic stroke

While clinical trials have now solidified the role of thrombectomy in emergent large vessel occlusive stroke, additional therapies are needed to optimize patient outcome. Using our previously described experimental ischemic stroke model for evaluating adjunctive intra-arterial drug therapy after vessel recanalization, we studied the potential neuroprotective effects of verapamil. A calcium channel blocker, verapamil is often infused intra-arterially by neurointerventionalists to treat cerebral vasospasm. Such a direct route of administration allows for both focused targeting of stroke-impacted brain tissue and minimizes potential systemic side effects. Intra-arterial administration of verapamil at a flow rate of 2.5 µl/min and injection volume of 10 µl immediately after middle cerebral artery recanalization in C57/Bl6 mice was shown to be profoundly neuroprotective as compared to intra-arterial vehicle-treated stroke controls. Specifically, we noted a significant (P ≤ 0.05) decrease in infarct volume, astrogliosis, and cellular apoptosis as well as a significant increase in neuronal survival and functional outcome over seven days. Furthermore, intra-arterial administration of verapamil was well tolerated with no hemorrhage, systemic side effects, or increased mortality. Thus, verapamil administered intra-arterially immediately following recanalization in experimental ischemic stroke is both safe and neuroprotective and merits further study as a potential therapeutic adjunct to thrombectomy.

Abstract W MP6: SAVER I: Superselective Administration of VErapamil during Recanalization in Acute Ischemic Stroke. A Phase I Feasibility Study

Large vessel occlusive ischemic stroke results in high rates of morbidity and mortality. While intravenous t-PA and intra-arterial (IA) thrombectomy are mainstays in acute stroke therapy, clinical outcomes lag significantly behind improving rates of acute revascularization. Thus, there is a critical need for a novel adjunctive therapy to reduce stroke burden and to improve outcome. Previous neuroprotective drug studies failed due to long intervals between symptom onset and drug administration, lack of concordant thrombolytic revascularization, and lack of targeted administration to the affected vessel. Through a retro-engineered mouse model of large vessel stroke allowing concomitant recanalization and selective intra-arterial (IA) administration we previously evaluated verapamil, a calcium channel blocker (CCB) that is already safely injected intra-arterially (IA) for vasospasm. In this clinically relevant model, verapamil was highly neuroprotective when combined with vessel recanalization. Based on this data, we conducted a single-institution Phase I study to evaluate the feasibility and safety of superselective IA verapamil (10mg) administration immediately following mechanical thrombectomy. We collected information about demographics, location of the occlusion, last known normal time, time to and recanalization. Evaluation of CTA collateralization was performed using a previously a published grading scale (Souza et al. AJNR. 2012). The primary endpoint was symptomatic intracranial hemorrhage (ICH) within 24 hours post-procedure as defined by the Interventional Management Stroke (IMS) III Trial (Broderick et al. NEJM. 2013). Patients were monitored and graded at 3 months with the modified Rankin Score (mRS). Of the enrolled patients, none had a significant ICH, and none died as a direct result of the procedure. Clinical outcome results for patients were encouraging, and warrant further study. These results will be used to support a Phase II dose selection study.

Abstract W P259: Selective Intra-arterial Administration of Verapamil is Neuroprotective in Acute Ischemic Stroke

Despite the urgent need for better stroke therapies, experimental stroke treatments have largely failed to translate to stroke patients. In an effort to bridge this translational gap, we have concentrated our efforts on drugs that are already FDA approved and associated with treating stroke-associated pathophysiology, such as cerebral artery vasospasm, with the goal of repurposing them to protect brain tissue from ischemic injury. Verapamil, a calcium channel blocker, is one such drug that is often infused intra-arterially by neurosurgeons treating vasospasm that results in ischemia. In demonstrating a reliable and reproducible stroke mouse model ( transient middle cerebral artery occlusion, MCAo) with the addition of a retro-engineered IA drug delivery model mimicking the human condition, we were able to optimize the injection volume and flow rate for pharmacotherapy administration of verapamil. Through this direct route of administration we have shown a significant decrease (P<0.001) in infarct volume and trending towards significance an increase in behavioral outcome when comparing treated animals versus control. Perfusion studies did not show significant differences in perfusion to account for vasomotor changes as the likely mechanism for ischemia reduction. To further explore this, after 1 hour MCAo in three month old C57/Bl6 mice, we examined the potential neuroprotective effects of verapamil on post stroke day 3. Whole brains were harvested and flash frozen for cryostat sectioning and cellular staining to compare apoptosis, appearance of mature neurons, astrocyte activation and synaptic stability. Results suggest that IA administration of verapamil, more specifically than reducing infarct volume, is directly neuroprotective on brain parenchymal tissue at risk.