Effect of cerebral microbleeds on hemorrhagic transformation and functional prognosis after intravenous thrombolysis of cerebral infarction

Cell polarization in ischemic stroke: molecular mechanisms and advances

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as 'cell polarization.' There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations (microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Prevalence and Impact of Cerebral Microbleeds on Clinical and Safety Outcomes in Acute Ischaemic Stroke Patients Receiving Reperfusion Therapy: A Systematic Review and Meta-Analysis

BACKGROUND

Cerebral microbleeds (CMBs), a notable neuroimaging finding often associated with cerebral microangiopathy, demonstrate a heightened prevalence in patients diagnosed with acute ischemic stroke (AIS), which is in turn linked to less favourable clinical prognoses. Nevertheless, the exact prevalence of CMBs and their influence on post-reperfusion therapy outcomes remain inadequately elucidated.

MATERIALS AND METHODS

Through systematic searches of PubMed, Embase and Cochrane databases, studies were identified adhering to specific inclusion criteria: (a) AIS patients, (b) age ≥ 18 years, (c) CMBs at baseline, (d) availability of comparative data between CMB-positive and CMB-negative groups, along with relevant post-reperfusion therapy outcomes. The data extracted were analysed using forest plots of odds ratios, and random-effects modelling was applied to investigate the association between CMBs and symptomatic intracerebral haemorrhage (sICH), haemorrhagic transformation (HT), 90-day functional outcomes, and 90-day mortality post-reperfusion therapy.

RESULTS

In a total cohort of 9776 AIS patients who underwent reperfusion therapy, 1709 had CMBs, with a pooled prevalence of 19% (ES 0.19; 95% CI: 0.16, 0.23, p < 0.001). CMBs significantly increased the odds of sICH (OR 2.57; 95% CI: 1.72; 3.83; p < 0.0001), HT (OR 1.53; 95% CI: 1.25; 1.88; p < 0.0001), as well as poor functional outcomes at 90 days (OR 1.59; 95% CI: 1.34; 1.89; p < 0.0001) and 90-day mortality (OR 1.65; 95% CI: 1.27; 2.16; p < 0.0001), relative to those without CMBs, in AIS patients undergoing reperfusion therapy (encompassing intravenous thrombolysis [IVT], endovascular thrombectomy [EVT], either IVT or EVT, and bridging therapy). Variations in the level of association can be observed among different subgroups of reperfusion therapy.

CONCLUSIONS

This meta-analysis underscores a significant association between CMBs and adverse postprocedural safety outcomes encompassing sICH, HT, poor functional outcome, and increased mortality in AIS patients undergoing reperfusion therapy. The notable prevalence of CMBs in both the overall AIS population and those undergoing reperfusion therapy emphasizes their importance in post-stroke prognostication.

Directional induction of neural stem cells, a new therapy for neurodegenerative diseases and ischemic stroke

Due to the limited capacity of the adult mammalian brain to self-repair and regenerate, neurological diseases, especially neurodegenerative disorders and stroke, characterized by irreversible cellular damage are often considered as refractory diseases. Neural stem cells (NSCs) play a unique role in the treatment of neurological diseases for their abilities to self-renew and form different neural lineage cells, such as neurons and glial cells. With the increasing understanding of neurodevelopment and advances in stem cell technology, NSCs can be obtained from different sources and directed to differentiate into a specific neural lineage cell phenotype purposefully, making it possible to replace specific cells lost in some neurological diseases, which provides new approaches to treat neurodegenerative diseases as well as stroke. In this review, we outline the advances in generating several neuronal lineage subtypes from different sources of NSCs. We further summarize the therapeutic effects and possible therapeutic mechanisms of these fated specific NSCs in neurological disease models, with special emphasis on Parkinson's disease and ischemic stroke. Finally, from the perspective of clinical translation, we compare the strengths and weaknesses of different sources of NSCs and different methods of directed differentiation, and propose future research directions for directed differentiation of NSCs in regenerative medicine.

New Remote Cerebral Microbleeds on T2*-Weighted Echo Planar MRI After Intravenous Thrombolysis for Acute Ischemic Stroke

Background

The main and well-defined complication of intravenous administration of recombinant tissue plasminogen activator (tPA) in patients with acute ischemic stroke (AIS) is symptomatic intracranial hemorrhage (sICH). However, rtPA might also be connected with the formation of cerebral microbleeds (CMBs), located remotely from the ischemic lesions, that may remain clinically silent. This association might be important because the load of CMBs has been associated with cognitive impairment. We investigated whether administration of rtPA in AIS results in the appearance of new CMBs and if the initial load of CMBs is associated with hemorrhagic transformation.

Methods

A total of fifty-nine consecutive patients with AIS treated with rtPA underwent MRI including T2^*-weighted Echo Planar Imaging (T2^*-EPI) shortly before and 7–9 days after rtPA administration. We calculated the load of new CMBs located outside the MR diffusion restriction area in the follow-up imaging and assessed hemorrhagic transformation with ECASS-II scoring.

Results

A total of forty-nine patients were included for the final analysis. On initial T2^*-EPI-GRE, 37 baseline microbleeds (CMBs) were observed in 14 patients (28.6%). On follow-up T2^*-EPI-GRE amount of CMBs increased to a total number of 103. New CMBs were found in 5 (14.3%) of 35 patients without and in 9 (64.3%) of 14 with any baseline CMBs. Multiple logistic regression analysis indicated that presence of baseline CMBs (risk ratio [RR] 5.95, 95% CI 2.69–13.20, p < 0.001) and lower platelets level (risk ratio [RR] 0.992, 95% CI 0.986–0.998, p = 0.007) were independently associated with new CMBs. The baseline load of CMBs was not associated with the risk of hemorrhagic transformation.

Conclusion

In this study, new CMBs were found in nearly 30% of patients with AIS on the 7–9 days after rtPA treatment. Baseline CMBs correlated with a higher risk of new CMBs appearing after the rtPA treatment, independently of other factors. At the same time, in our sample, baseline CMBs did not correlate with an increased risk of hemorrhagic transformation. Since the associations between the CMBs load and cognitive impairment have already been proved, further studies are warranted to investigate possible associations between the thrombolytic treatment of patients with AIS, mainly those with baseline CMBs, and the risk of earlier cognitive decline.