Early changes in physiological variables after stroke

Microphysiological Blood-Brain Barrier Systems for Disease Modeling and Drug Development

The blood-brain barrier (BBB) is a highly controlled microenvironment that regulates the interactions between cerebral blood and brain tissue. Due to its selectivity, many therapeutics targeting various neurological disorders are not able to penetrate into brain tissue. Pre-clinical studies using animals and other in vitro platforms have not shown the ability to fully replicate the human BBB leading to the failure of a majority of therapeutics in clinical trials. However, recent innovations in vitro and ex vivo modeling called organs-on-chips have shown the potential to create more accurate disease models for improved drug development. These microfluidic platforms induce physiological stressors on cultured cells and are able to generate more physiologically accurate BBBs compared to previous in vitro models. In this review, different approaches to create BBBs-on-chips are explored alongside their application in modeling various neurological disorders and potential therapeutic efficacy. Additionally, organs-on-chips use in BBB drug delivery studies is discussed, and advances in linking brain organs-on-chips onto multiorgan platforms to mimic organ crosstalk are reviewed.

A Multi-Parametric Approach for Characterising Cerebral Haemodynamics in Acute Ischaemic and Haemorrhagic Stroke

BACKGROUND AND PURPOSE

Early differentiation between acute ischaemic (AIS) and haemorrhagic stroke (ICH), based on cerebral and peripheral hemodynamic parameters, would be advantageous to allow for pre-hospital interventions. In this preliminary study, we explored the potential of multiple parameters, including dynamic cerebral autoregulation, for phenotyping and differentiating each stroke sub-type.

METHODS

Eighty patients were included with clinical stroke syndromes confirmed by computed tomography within 48 h of symptom onset. Continuous recordings of bilateral cerebral blood velocity (transcranial Doppler ultrasound), end-tidal CO2 (capnography), electrocardiogram (ECG), and arterial blood pressure (ABP, Finometer) were used to derive 67 cerebral and peripheral parameters.

RESULTS

A total of 68 patients with AIS (mean age 66.8 ± SD 12.4 years) and 12 patients with ICH (67.8 ± 16.2 years) were included. The median ± SD NIHSS of the cohort was 5 ± 4.6. Statistically significant differences between AIS and ICH were observed for (i) an autoregulation index (ARI) that was higher in the unaffected hemisphere (UH) for ICH compared to AIS (5.9 ± 1.7 vs. 4.9 ± 1.8 p = 0.07); (ii) coherence function for both hemispheres in different frequency bands (AH, p < 0.01; UH p < 0.02); (iii) a baroreceptor sensitivity (BRS) for the low-frequency (LF) bands that was higher for AIS (6.7 ± 4.2 vs. 4.10 ± 2.13 ms/mmHg, p = 0.04) compared to ICH, and that the mean gain of the BRS in the LF range was higher in the AIS than in the ICH (5.8 ± 5.3 vs. 2.7 ± 1.8 ms/mmHg, p = 0.0005); (iv) Systolic and diastolic velocities of the affected hemisphere (AH) that were significantly higher in ICH than in AIS (82.5 ± 28.09 vs. 61.9 ± 18.9 cm/s), systolic velocity (p = 0.002), and diastolic velocity (p = 0.05).

CONCLUSION

Further multivariate modelling might improve the ability of multiple parameters to discriminate between AIS and ICH and warrants future prospective studies of ultra-early classification (<4 h post symptom onset) of stroke sub-types.

Physiological Variability during Prehospital Stroke Care: Which Monitoring and Interventions Are Used?

Prehospital care is a fundamental component of stroke care that predominantly focuses on shortening the time between diagnosis and reaching definitive stroke management. With growing evidence of the physiological parameters affecting long-term patient outcomes, prehospital clinicians need to consider the balance between rapid transfer and increased physiological-parameter monitoring and intervention. This systematic review explores the existing literature on prehospital physiological monitoring and intervention to modify these parameters in stroke patients. The systematic review was registered on PROSPERO (CRD42022308991) and conducted across four databases with citation cascading. Based on the identified inclusion and exclusion criteria, 19 studies were retained for this review. The studies were classified into two themes: physiological-monitoring intervention and pharmacological-therapy intervention. A total of 14 included studies explored prehospital physiological monitoring. Elevated blood pressure was associated with increased hematoma volume in intracerebral hemorrhage and, in some reports, with increased rates of early neurological deterioration and prehospital neurological deterioration. A reduction in prehospital heart rate variability was associated with unfavorable clinical outcomes. Further, five of the included records investigated the delivery of pharmacological therapy in the prehospital environment for patients presenting with acute stroke. BP-lowering interventions were successfully demonstrated through three trials; however, evidence of their benefit to clinical outcomes is limited. Two studies investigating the use of oxygen and magnesium sulfate as neuroprotective agents did not demonstrate an improvement in patient's outcomes. This systematic review highlights the absence of continuous physiological parameter monitoring, investigates fundamental physiological parameters, and provides recommendations for future work, with the aim of improving stroke patient outcomes.

Exosome-Coated tPA/Catalase Nanoformulation for Thrombolytic Therapy

Current tissue plasminogen-based therapeutic strategies for stroke suffer from systemic side effects and poor efficacy. Hence, novel drug delivery methods are needed to overcome these shortcomings. Exosome-based drug formulations have been shown to have superior therapeutic outcomes compared to conventional systemic drug delivery approaches. In this paper, we report exosome surface-coated tissue plasminogen activator (tPA)/catalase nanoformulations with improved thrombolytic efficacy compared to free tPA, which also reduce side effects. The results showed that the tPA exosome formulations retained tPA activity, improved tPA stability, exhibited significant fibrinolysis, and showed no significant toxicity effects. Further, when combined with antioxidant enzyme catalase, the formulation was able to inhibit hydrogen peroxide-mediated oxidative stress and toxicity. Hence, exosome-based tPA/catalase nanoformulations could have the potential to offer a safer and effective thrombolytic therapy.

The time dimension to stroke: Circadian effects on stroke outcomes and mechanisms

The circadian system is widely involved in the various pathological outcomes affected by time dimension changes. In the brain, the master circadian clock, also known as the "pacemaker," is present in the hypothalamus's suprachiasmatic nucleus (SCN). The SCN consists of molecular circadian clocks that operate in each neuron and other brain cells. These circadian mechanisms are controlled by the transcription and translation of specific genes such as the clock circadian regulator (Clock) and brain and muscle ARNT-Like 1 (Bmal1). Period (Per1-3) and cryptochrome (Cry1 and 2) negatively feedback and regulate the clock genes. Variations in the circadian cycle and these clock genes can affect stroke outcomes. Studies suggest that the peak stroke occurs in the morning after patients awaken from sleep, while stroke severity and poor outcomes worsen at midnight. The main risk factor associated with stroke is high blood pressure (hypertension). Blood pressure usually dips by 15-20% during sleep, but many hypertensives do not display this normal dipping pattern and are non-dippers. A sleep blood pressure is the primary determinant of stroke risk. This article discusses the possible mechanism associated with circadian rhythm and stroke outcomes.

The Role of Unobtrusive Home-Based Continuous Sensing in the Management of Postacute Sequelae of SARS CoV-2

Amid the COVID-19 pandemic, it has been reported that greater than 35% of patients with confirmed or suspected COVID-19 develop postacute sequelae of SARS CoV-2 (PASC). PASC is still a disease for which preliminary medical data are being collected-mostly measurements collected during hospital or clinical visits-and pathophysiological understanding is yet in its infancy. The disease is notable for its prevalence and its variable symptom presentation, and as such, management plans could be more holistically made if health care providers had access to unobtrusive home-based wearable and contactless continuous physiologic and physical sensor data. Such between-hospital or between-clinic data can quantitatively elucidate a majority of the temporal evolution of PASC symptoms. Although not universally of comparable accuracy to gold standard medical devices, home-deployed sensors offer great insights into the development and progression of PASC. Suitable sensors include those providing vital signs and activity measurements that correlate directly or by proxy to documented PASC symptoms. Such continuous, home-based data can give care providers contextualized information from which symptom exacerbation or relieving factors may be classified. Such data can also improve the collective academic understanding of PASC by providing temporally and activity-associated symptom cataloging. In this viewpoint, we make a case for the utilization of home-based continuous sensing that can serve as a foundation from which medical professionals and engineers may develop and pursue long-term mitigation strategies for PASC.

Acute confusional state as a prognostic sign of COVID-19 large-vessel occlusion (LVO)

COVID-19 is well known for its respiratory symptoms, but severe presentations can alter haemostasis, causing acute end-organ damage with poor outcomes. Among its various neurological presentations, cerebrovascular events often present as small-vessel strokes. Although uncommon, in predisposed individuals, large-vessel occlusions (LVOs) can occur as a possible consequence of direct viral action (viral burden or antigenic structure) or virus-induced cytokine storm. Subtle presentations and complicated stroke care pathways continue to exist, delaying timely care. We present a unique case of COVID-19 LVO manifesting as an acute confusional state in an elderly man in April 2020. CT angiography revealed 'de novo' occlusions of the left internal carotid artery and proximal right vertebral artery, effectively blocking anterior and posterior circulations. Delirium can lead to inaccurate stroke scale assessments and prolong initiation of COVID-19 stroke care pathways. Future studies are needed to look into the temporal relationship between confusion and neurological manifestations.

Changes of augmentation index early after ischaemic stroke predict functional outcome

Purpose: Outcome after ischaemic stroke (AIS) depends on multiple factors, including values of blood pressure (BP) and arterial stiffness (AS) in the early phase. It is also known that stroke outcome is affected by BP variability; however, the influence of AS oscillations in the early phase of stroke on its prognosis is unknown. The aim of our study was to assess the relationship between changes of AS markers and stroke outcome.Materials and methods: Baseline clinical data, BP parameters, and markers of AS (pulse wave velocity [PWV], augmentation index [AIx]) were assessed 1, 6, and >90 days after AIS. The outcomes were defined using modified Rankin scale (mRS) score: early favourable (EFO) and early poor (EPO), as mRS ≤1 and >2 points at discharge, respectively; late favourable (LFO) and late poor (LPO), as mRS ≤1 and >2 points on day >90, respectively.Results: In the recruited 50 patients (62.2 ± 12.1 years, 68% males), BP and PWV decreased while AIx did not change within 90 days after AIS. Twenty-eight patients (56%) had EFO, 10 (20%) - EPO, 29 (58%) - LFO, and 9 (18%) - LPO. In univariate analysis, rise in AIx in days 1-6 was associated with EFO (odds ratio [OR] = 1.09, 95% confidence interval [CI] = 1.02-1.17, p = 0.01) and LFO (OR = 1.08; 95%CI = 1.01-1.14, p = 0.02), whereas decrease in AIx in days 1-6 was associated with EPO (OR = 1.07, 95%CI = 1.00-1.15, p = 0.05). For EFO and LFO, the relationships remained significant after including confounders (p = 0.03 and p = 0.03, respectively).Conclusions: Rise in AIx within one week after ischaemic stroke may be of additional importance in determining better early and late favourable functional outcome.

Dynamics of inflammatory factors expression in ischemic brain tissue injury

Ischemic stroke is one of the most common cause of mortality and disability in the modern world. Still, therapeutic options remain modest. Aim of the study was to present dynamics of inflammatory factors expression (C reactive protein, procalcitonin, interleukin 10) in patients after ischemic stroke. Our study included 101 patients divided in thrombolised and nonthrombolised groups. Inflammatory factors concentration in serum was determinate at admission, 24, 48 hours and seven days after the initial onset, while neurological assessment was measured at the admission, 24 hours, seven days and three months after the initial onset using National Institute of Health Stroke Scale and Rankin Scale. Certain pattern was observed in dynamics of inflammatory factors: intensive increase in first and second day after the stroke, followed by decrease till day seven in both groups. Additionally, thrombolised group showed significant neurological improvement. Although well investigated, the role of inflammatory factors in the ischemic stroke still stays controversial. High association of C reactive protein and interleukin 10 values suggest potential prognostic role in patient’s follow-up, while the role of procalcitonin values still remains unclear.

Cerebrovascular function and mitochondrial bioenergetics after ischemia-reperfusion in male rats

The underlying factors promoting increased mitochondrial proteins, mtDNA, and dilation to mitochondrial-specific agents in male rats following tMCAO are not fully elucidated. Our goal was to determine the morphological and functional effects of ischemia/reperfusion (I/R) on mitochondria using electron microscopy, Western blot, mitochondrial oxygen consumption rate (OCR), and Ca2+ sparks activity measurements in middle cerebral arteries (MCAs) from male Sprague Dawley rats (Naïve, tMCAO, Sham). We found a greatly increased OCR in ipsilateral MCAs (IPSI) compared with contralateral (CONTRA), Sham, and Naïve MCAs. Consistent with our earlier findings, the expression of Mitofusin-2 and OPA-1 was significantly decreased in IPSI arteries compared with Sham and Naïve. Mitochondrial morphology was disrupted in vascular smooth muscle, but morphology with normal and perhaps greater numbers of mitochondria were observed in IPSI compared with CONTRA MCAs. Consistently, there were significantly fewer baseline Ca2+ events in IPSI MCAs compared with CONTRA, Sham, and Naïve. Mitochondrial depolarization significantly increased Ca2+ sparks activity in the IPSI, Sham, Naïve, but not in the CONTRA group. Our data indicate that altered mitochondrial structure and function occur in MCAs exposed to I/R and that these changes impact not only OCR but Ca2+ sparks activity in both IPSI and CONTRA MCAs.

Erythropoietin Pretreatment Effect on Blood Glucose and Its Relationship With Inflammatory Factors After Brain Ischemic-Reperfusion Injury in Rats

Introduction:

Brain Ichemic-Reperfusion Injury (IRI) activates different pathophysiological processes. It also changes physiological parameters such as Blood Glucose (BG) level. An increase in BG after stroke is associated with poor clinical outcomes. Erythropoietin has been shown to be effective on both reducing inflammation and BG level. Therefore, in this study the erythropoietin pretreatment effect on BG and its relationship with inflammatory markers after brain IRI was investigated.

Methods:

Thirty adult male Wistar rats were randomly divided into 5 groups: sham, control and 3 pretreatment groups: single dose, double dose, and triple dose that received 1000 U/kg of erythropoietin before stroke induction in different times intraperitoneally. A rat model of IRI was established by Middle Cerebral Artery Occlusion (MCAO) for 60 minutes. Infarct volume, neurological defects, Interleukin-1α (IL-1α) and IL-6 serum levels were evaluated 24 hours after reperfusion. Also BG was measured after 1, 6, and 24 hours.

Results:

Single dose of erythropoietin significantly decreased infarct volume and improved neurological defects which was associated with decreased serum level of IL-1α and IL-6 but higher doses of erythropoietin administration had adverse effects on histological, neurological, and inflammatory results. In addition, erythropoietin significantly increased BG in a dose-dependent manner.

Conclusion:

Erythropoietin could reduce brain IRI by reducing inflammation and BG stabilization. The results of the present study demonstrated a relationship between inflammatory factors and hyperglycemia after IRI and suggested that erythropoietin may be useful for preventing brain IRI, but its higher doses should be used with caution due to possible side effects.

Breaking up sitting time after stroke (BUST-stroke)

OBJECTIVES

People with stroke sit for long periods each day, which may compromise blood glucose control and increase risk of recurrent stroke. Studies in other populations have found regular activity breaks have a significant immediate (within-day) positive effect on glucose metabolism. We examined the effects of breaking up uninterrupted sitting with frequent, short bouts of light-intensity physical activity in people with stroke on post-prandial plasma glucose and insulin.

METHODS

Randomized within-participant crossover trial. We included people between 3 months and 10 years post-stroke, ambulant with minimal assistance and not taking diabetic medication other than metformin. The three experimental conditions (completed in random order) were: sitting for 8 h uninterrupted, sitting with 3 min bouts of light-intensity exercise while standing every 30 min, or sitting with 3 min of walking every 30 min. Meals were standardized and bloods were collected half- to one-hourly via an intravenous cannula.

RESULTS

A total of 19 participants (9 female, mean [SD] age 68.2 [10.2]) completed the trial. The majority ( n = 12, 63%) had mild stroke symptoms (National Institutes of Stroke Scale score 0-13). There was no significant effect of experimental condition on glucose (mean [SD] positive incremental area [+iAUC] mmol·L·h-1 under the curve during sitting 42.3 [29.5], standing 47.4 [23.1], walking 44.6 [26.5], p = 0.563) or insulin (mean + iAUC pmol·L·h-1 sitting 14,161 [7,560], standing 14,043 [8,312], walking 14,008 [8,269], p = 0.987).

CONCLUSION

Frequent, short bouts of light-intensity physical activity did not have a significant effect on post-prandial plasma glucose and insulin in this sample of people with stroke. Further studies are needed to identify strategies that improve inactivity-related glucose metabolism after stroke.

Queue-based modelling and detection of parameters involved in stroke outcome

We designed a queue-based model, and investigated which parameters are of importance when predicting stroke outcome. Medical record forms have been collected for 57 ischemic stroke patients, including medical history and vital sign measurement along with neurological scores for the first twenty-four hours of admission. The importance of each parameter is identified using multiple regression combined with a circular queue to iteratively fit outcome. Out of 39 parameters, the model isolated 14 which combined could estimate outcome with a root mean square error of 1.69 on the Scandinavian Stroke Scale, where outcome for patients were 36.75 ± 10.99. The queue-based model integrating multiple linear regression shows promising results for automatic selection of significant medically relevant parameters.

Mortality in ischemic stroke score: A predictive score of mortality for acute ischemic stroke

OBJECTIVE:

This prospective study was planned to formulate and evaluate a predictive score for in-hospital mortality in cases of acute ischemic stroke.

MATERIALS AND METHODS:

In this study, 188 consecutive patients of ischemic stroke were included over 19 months. Only patients with renal failure and malignancy were excluded from the study. All patients were subjected to clinical evaluation along with Glasgow Coma Scale (GCS), National Institute of Health Science scale (NIHSS) score, and modified Rankin score (mRS). Investigations total leukocyte count (TLC), capillary blood sugar at admission, high-sensitivity C-reactive protein (HS-CRP), and troponin I, electrocardiogram, and neuroimaging were performed. The patients were followed up till their outcome in the hospital, and patients who expired were grouped as “mortality group” and the rest as “discharged group.” One-way anova analysis was carried out among the significant parameters to identify independent predictors of mortality in cases of ischemic stroke.

RESULTS:

After statistical analysis, it was found that late presentation to the hospital, pyrexia (temperature >99F), low diastolic blood pressure at the time of admission, hypoxia (saturation of oxygen <94%), NIHSS score >15, mRS >3, GCS <8, hyperglycemia (random blood sugar >200 mg/dL), raised TLC, and HS-CRP (>10 mg/L) are positive predictive factors of mortality in cases of ischemic stroke. Based on the above findings, a simple and easily applicable mortality in ischemic stroke (MIS) score is developed.

CONCLUSION:

This MIS score system will help the clinicians in better management of the patient and improved counseling the relatives of patients with ischemic stroke.

White matter damage and glymphatic dysfunction in a model of vascular dementia in rats with no prior vascular pathologies

We investigated cognitive function, axonal/white matter (WM) changes and glymphatic function of vascular dementia using a multiple microinfarction (MMI) model in retired breeder (RB) rats. The MMI model induces significant (p < 0.05) cognitive decline that worsens with age starting at 2 weeks, which persists until at least 6 weeks after MMI. RB rats subjected to MMI exhibit significant axonal/WM damage identified by decreased myelin thickness, oligodendrocyte progenitor cell numbers, axon density, synaptic protein expression in the cortex and striatum, cortical neuronal branching, and dendritic spine density in the cortex and hippocampus compared with age-matched controls. MMI evokes significant dilation of perivascular spaces as well as water channel dysfunction indicated by decreased Aquaporin-4 expression around blood vessels. MMI-induced glymphatic dysfunction with delayed cerebrospinal fluid penetration into the brain parenchyma via paravascular pathways as well as delayed waste clearance from the brain. The MMI model in RB rats decreases Aquaporin-4 and induces glymphatic dysfunction which may play an important role in MMI-induced axonal/WM damage and cognitive deficits.

Angiotensin-Receptor Blocker, Angiotensin-Converting Enzyme Inhibitor, and Risks of Atrial Fibrillation: A Nationwide Cohort Study

Both angiotensin-receptor blockers (ARB) and angiotensin-converting enzyme inhibitors (ACEI) have protective effects against atrial fibrillation (AF). The differences between ARB and ACEI in their effects on the primary prevention of AF remain unclear. This study compared ARB and ACEI in combined antihypertensive medications for reducing the risk of AF in patients with hypertension, and determined which was better for AF prevention in a nationwide cohort study.Patients aged ≥55 years and with a history of hypertension were identified from Taiwan National Health Insurance Research Database. Medical records of 25,075 patients were obtained, and included 6205 who used ARB, 8034 who used ACEI, and 10,836 nonusers (no ARB or ACEI) in their antihypertensive regimen. Cox regression models were applied to estimate the hazard ratio (HR) for new-onset AF.During an average of 7.7 years' follow-up, 1619 patients developed new-onset AF. Both ARB (adjusted HR: 0.51, 95% CI 0.44-0.58, P < 0.001) and ACEI (adjusted HR: 0.53, 95% CI 0.47-0.59, P < 0.001) reduced the risk of AF compared to nonusers. Subgroup analysis showed that ARB and ACEI were equally effective in preventing new-onset AF regardless of age, gender, the presence of heart failure, diabetes, and vascular disease, except for those with prior stroke or transient ischemic attack (TIA). ARB prevents new-onset AF better than ACEI in patients with a history of stroke or TIA (log-rank P = 0.012).Both ARB and ACEI reduce new-onset AF in patients with hypertension. ARB prevents AF better than ACEI in patients with a history of prior stroke or TIA.

Vitamin D deficiency and its characteristics among patients with acute stroke at a national referral hospital in Kampala Uganda

BACKGROUND

Vitamin D deficiency has been associated with acute stroke and other cardiovascular diseases in the developed world. Low 25-hydroxyvitamin D (25OHD) has been described in some populations in Sub-Saharan Africa (SSA) in spite of adequate sunshine all year round. There is no information on the magnitude of vitamin D deficiency among patients with stroke and other cardiovascular diseases in Uganda or SSA. The aim of this study was to determine the burden and characteristics of vitamin D deficiency among patients with acute stroke, the most common form of cardiovascular events in SSA.

METHODS

We conducted a cross-sectional study between October 2012 and March 2013. We consecutively recruited 142 subjects with acute stroke admitted to the medical wards of Mulago hospital. We administered a pre-tested questionnaire to the study participants, and did a detailed physical examination and laboratory evaluation. Serum levels of 25OHD were determined using an electrochemiluminescence assay. Data were analyzed using STATA version 12 software.

RESULTS

The prevalence of vitamin D deficiency (25OHD < 20 ng/ml) was 15 %. Longer hours of sunshine exposure decreased the likelihood vitamin D deficiency significantly (adjusted OR 0.85, p = 0.03). Higher HDL cholesterol had a significant inverse association with vitamin D deficiency (adjusted OR 0.15, p = 0.02). In addition, the likelihood of vitamin D deficiency increased with rising age (adjusted OR 1.03, p = 0.05).

CONCLUSIONS

There was a relatively low burden of vitamin D deficiency among patients with acute stroke in Uganda. With increasing longevity and indoor lifestyles vitamin D deficiency may assume a greater role in stroke and other cardiovascular diseases in tropical sub Saharan Africa. Future studies on the mechanisms of vitamin D deficiency and its relationship to outcomes among patients with stroke may be necessary.