Causal associations of serum matrix metalloproteinase-8 level with ischaemic stroke and ischaemic stroke subtypes: a Mendelian randomization study

Ultrasound-Targeted Microbubble Destruction Increases BBB Permeability and Promotes Stem Cell-Induced Regeneration of Stroke by Downregulating MMP8

The objective of this study was to evaluate the feasibility, safety, and effectiveness of intravenous stem cell delivery utilizing ultrasound-targeted microbubble destruction (UTMD) in a rat model of middle cerebral artery occlusion (MCAO), while investigating the underlying mechanisms. Acute cerebral infarction (ACI) was induced surgically in adult rats to create the MCAO rat model. Intravenous injection of SonoVue microbubbles and bone marrow-derived mesenchymal stem cells (BMSC) was performed concurrently, with or without ultrasound targeting the stroke. The animals were divided into four groups: sham-operated group, ACI-MCAO rats treated with phosphate-buffered saline (ACI+PBS), rats receiving intravenous delivery of BMSC expressing green fluorescent protein (GFP-BMSC; ACI+BMSC), and rats receiving intravenous GFP-BMSC with simultaneous UTMD exposure (ACI+BMSC+UTMD). The efficacy of the treatments was assessed by evaluating the animals' neurological function using the Longa score and examining histopathological changes such as cerebral infarct volume, cerebral edema, and cell apoptosis. A rat cytokine array was utilized to identify the potential cytokines that may be responsible for the therapeutic effect of UTMD-mediated BMSC treatment. Optimal UTMD parameters resulted in an increase in blood-brain barrier (BBB) permeability after 30 min, which returned to baseline 72 h later without causing any residual injury. UTMD application significantly increased the homing of intravenously delivered BMSC, resulting in a 2.2-fold increase in GFP-BMSC cell count on day 3 and a 2.6-fold increase on day 7 compared with intravenous delivery alone. This effect persisted for up to 6 weeks after injection. Intravenous BMSC delivery significantly reduced the volume of cerebral infarct and decreased cerebral edema, leading to a lower Longa score. Furthermore, this effect was further enhanced by UTMD. Acute cerebral infarction induced by MCAO led to elevated matrix metalloproteinase 8 (MMP8) levels in the cerebrospinal fluid, which were significantly reduced following UTMD-mediated BMSC treatment. Ultrasound-targeted microbubble destruction facilitates the migration and homing of BMSC into the brain, possibly by transiently increasing blood-brain barrier (BBB) permeability, thereby improving therapeutic outcomes in an ACI rat model. The observed effect may be partly attributed to modulation of MMP8 levels.Advances in knowledge: UTMD-mediated intravenously delivered BMSC transplantation led to a significant increase in cell homing and reduction of MMP8 levels, resulting in increased therapeutic effect in an acute ischemic cerebral infarction model.

Exploring the Causality of Type 1 Diabetes and Stroke Risk: A Mendelian Randomization Study and Meta-analysis

Type II diabetes was causally related to stroke, which is a risk factor for stroke. However, the causal relationship between type I diabetes(T1D) and stroke, especially its subtypes, remains unclear. To determine whether T1D has a genetic causal link to stroke and its subtypes, we undertook this mendelian randomization (MR) study. The genome-wide association studies (GWAS) of T1D was the source of exposure. The outcomes were strokes and their subtypes, including ischemic stroke (IS), small vessel stroke (SVS), cardioembolic stroke (CES), large artery atherosclerosis stroke (LAS), intracerebral hemorrhage (ICH), lobar intracerebral hemorrhage (LICH), and non-lobar intracerebral hemorrhage (NLICH). We used outcome GWAS conducted by ISGC consortium for the initial phase and GWAS from MEGASTROKE consortium as the data for the replication phase to confirm the causal association. Besides, we conducted a meta-analysis of the causal association from ISGC and MEGASTROKE databases to confirm robust causality. Inverse-variance weighting (IVW) was utilized as the primary method to estimate the causality between T1D and stroke. The Cochran's Q test and the MR-PRESSO global test were used to examine the sensitivity. We discovered the causal relationship between T1D and SVS (OR = 1.17, 95% CI: 1.07-1.28, p = 6.0 × 10- 4), CES (OR = 1.11, 95%CI: 1.03-1.21, p = 0.0080) in initial stage. The replication phase validated T1D has a causal relationship with SVS (OR = 1.12, 95% CI: 1.06-1.18, p = 4.0 × 10- 5), but not with stroke and other subtypes. The meta-analysis of initial and replication stage again supported the causal link between T1D and SVS (OR = 1.13, 95% CI: 1.08-1.18, p < 0.05). However, no causal relationship was found between T1D and other stroke subtypes. The sensitivity analysis also supported the robust of these results. In conclusion, T1D was causally associated with SVS, but not with other subtypes of stroke. More investigation is needed to understand the underlying biology mechanism.

Ischemic stroke of unclear aetiology: a case-by-case analysis and call for a multi-professional predictive, preventive and personalised approach

Due to the reactive medical approach applied to disease management, stroke has reached an epidemic scale worldwide. In 2019, the global stroke prevalence was 101.5 million people, wherefrom 77.2 million (about 76%) suffered from ischemic stroke; 20.7 and 8.4 million suffered from intracerebral and subarachnoid haemorrhage, respectively. Globally in the year 2019 — 3.3, 2.9 and 0.4 million individuals died of ischemic stroke, intracerebral and subarachnoid haemorrhage, respectively. During the last three decades, the absolute number of cases increased substantially. The current prevalence of stroke is 110 million patients worldwide with more than 60% below the age of 70 years. Prognoses by the World Stroke Organisation are pessimistic: globally, it is predicted that 1 in 4 adults over the age of 25 will suffer stroke in their lifetime. Although age is the best known contributing factor, over 16% of all strokes occur in teenagers and young adults aged 15–49 years and the incidence trend in this population is increasing. The corresponding socio-economic burden of stroke, which is the leading cause of disability, is enormous. Global costs of stroke are estimated at 721 billion US dollars, which is 0.66% of the global GDP.

Clinically manifested strokes are only the “tip of the iceberg”: it is estimated that the total number of stroke patients is about 14 times greater than the currently applied reactive medical approach is capable to identify and manage. Specifically, lacunar stroke (LS), which is characteristic for silent brain infarction, represents up to 30% of all ischemic strokes. Silent LS, which is diagnosed mainly by routine health check-up and autopsy in individuals without stroke history, has a reported prevalence of silent brain infarction up to 55% in the investigated populations. To this end, silent brain infarction is an independent predictor of ischemic stroke. Further, small vessel disease and silent lacunar brain infarction are considered strong contributors to cognitive impairments, dementia, depression and suicide, amongst others in the general population. In sub-populations such as diabetes mellitus type 2, proliferative diabetic retinopathy is an independent predictor of ischemic stroke.

According to various statistical sources, cryptogenic strokes account for 15 to 40% of the entire stroke incidence. The question to consider here is, whether a cryptogenic stroke is fully referable to unidentifiable aetiology or rather to underestimated risks. Considering the latter, translational research might be of great clinical utility to realise innovative predictive and preventive approaches, potentially benefiting high risk individuals and society at large.

In this position paper, the consortium has combined multi-professional expertise to provide clear statements towards the paradigm change from reactive to predictive, preventive and personalised medicine in stroke management, the crucial elements of which are:

Consolidation of multi-disciplinary expertise including family medicine, predictive and in-depth diagnostics followed by the targeted primary and secondary (e.g. treated cancer) prevention of silent brain infarction

Application of the health risk assessment focused on sub-optimal health conditions to effectively prevent health-to-disease transition

Application of AI in medicine, machine learning and treatment algorithms tailored to robust biomarker patterns

Application of innovative screening programmes which adequately consider the needs of young populations

Stroke is a severe brain disease which has reached an epidemic scale worldwide: in 2019, the global stroke prevalence was 101.5 million people. The World Stroke Organisation predicted that globally, 1 in 4 adults over the age of 25 will get a stroke in their lifetime. Not only old people but also teenagers and young adults are affected. Current global costs of stroke are estimated at 721 billion US dollars. Due to undiagnosed so-called “silent” brain infarction, the number of affected individuals is about 14 times greater in the population than clinically recorded. If it remains untreated, silent brain infarction may cause many severe and fatal disorders such as dementia, depression and even suicide. In this position paper, the consortium describes how the rudimental approach to treating severely diseased people could be replaced by an innovative predictive and preventive one to protect people against the health-to-disease transition.

Targeted Inhibition of Matrix Metalloproteinase-8 Prevents Aortic Dissection in a Murine Model

Aortic dissection (AD) is a lethal aortic pathology without effective medical treatments since the underlying pathological mechanisms responsible for AD remain elusive. Matrix metalloproteinase-8 (MMP8) has been previously identified as a key player in atherosclerosis and arterial remodeling. However, the functional role of MMP8 in AD remains largely unknown. Here, we report that an increased level of MMP8 was observed in 3-aminopropionitrile fumarate (BAPN)-induced murine AD. AD incidence and aortic elastin fragmentation were markedly reduced in MMP8-knockout mice. Importantly, pharmacologic inhibition of MMP8 significantly reduced the AD incidence and aortic elastin fragmentation. We observed less inflammatory cell accumulation, a lower level of aortic inflammation, and decreased smooth muscle cell (SMC) apoptosis in MMP8-knockout mice. In line with our previous observation that MMP8 cleaves Ang I to generate Ang II, BAPN-treated MMP8-knockout mice had increased levels of Ang I, but decreased levels of Ang II and lower blood pressure. Additionally, we observed a decreased expression level of vascular cell adhesion molecule-1 (VCAM1) and a reduced level of reactive oxygen species (ROS) in MMP8-knockout aortas. Mechanistically, our data show that the Ang II/VCAM1 signal axis is responsible for MMP8-mediated inflammatory cell invasion and transendothelial migration, while MMP8-mediated SMC inflammation and apoptosis are attributed to Ang II/ROS signaling. Finally, we observed higher levels of aortic and serum MMP8 in patients with AD. We therefore provide new insights into the molecular mechanisms underlying AD and identify MMP8 as a potential therapeutic target for this life-threatening aortic disease.

Evaluating the Causal Effects of TIMP-3 on Ischaemic Stroke and Intracerebral Haemorrhage: A Mendelian Randomization Study

Aim: Since tissue inhibitors of matrix metalloproteinase 3 (TIMP-3) was reported to be a potential risk factor of atherosclerosis, aneurysm, hypertension, and post-ischaemic neuronal injury, it may also be a candidate risk factor of stress. Therefore, this study was designed to explore the causal role of TIMP-3 in the risk of ischaemic stroke (IS) and intracerebral haemorrhage (ICH), which are the two main causes of stress via this Mendelian Randomisation (MR) study. Methods: The summarised data of TIMP-3 level in circulation was acquired from the Cooperative Health Research in the Region of Augsburg public database and the outcome of IS and ICH was obtained from genome-wide association studies conducted by MEGASTROKE and the International Stroke Genetics Consortium, respectively. Five statistical methods including inverse-variance weighting, weighted-median analysis, MR-Egger regression, MR Pleiotropy RESidual Sum and Outlier test, and MR-Robust Adjusted Profile Score were applied to evaluate the causal role of TIMP-3 in the occurrence of IS and ICH. Inverse-variance weighting was applied for assessing causality. Furthermore, heterogeneity and pleiotropic tests were utilised to confirm the reliability of this study. Results: We found that TIMP-3 could be a positively causal relationship with the incidence of IS (OR = 1.026, 95% CI: 1.007-1.046, p = 0.0067), especially for the occurrence of small vessel stroke (SVS; OR = 1.045, 95% CI: 1.016-1.076, p = 0.0024). However, the causal effects of TIMP-3 on another IS subtype cardioembolic stroke (CES; OR = 1.049, 95% CI: 1.006-1.094, p = 0.024), large artery stroke (LAS; OR = 1.0027, 95% CI: 0.9755-1.0306, p = 0.849) and ICH (OR = 0.9900, 95% CI: 0.9403-1.0423, p = 0.701), as well as ICH subtypes were not observed after Bonferroni corrections (p = 0.00714). Conclusion: Our results revealed that high levels of circulating TIMP-3 causally increased the risk of developing IS and SVS, but not CES, LAS, ICH, and all ICH subtypes. Further investigation is required to elucidate the underlying mechanism.