Potential Therapeutic Mechanisms and Tracking of Transplanted Stem Cells: Implications for Stroke Treatment

Stem cell therapy is a promising potential therapeutic strategy to treat cerebral ischemia in preclinical and clinical trials. Currently proposed treatments for stroke employing stem cells include the replacement of lost neurons and integration into the existing host circuitry, the release of growth factors to support and promote endogenous repair processes, and the secretion of extracellular vesicles containing proteins, noncoding RNA, or DNA to regulate gene expression in recipient cells and achieve immunomodulation. Progress has been made to elucidate the precise mechanisms underlying stem cell therapy and the homing, migration, distribution, and differentiation of transplanted stem cells in vivo using various imaging modalities. Noninvasive and safe tracer agents with high sensitivity and image resolution must be combined with long-term monitoring using imaging technology to determine the optimal therapy for stroke in terms of administration route, dosage, and timing. This review discusses potential therapeutic mechanisms of stem cell transplantation for the treatment of stroke and the limitations of current therapies. Methods to label transplanted cells and existing imaging systems for stem cell labeling and in vivo tracking will also be discussed.

Safety and Efficacy of Mechanical Thrombectomy in Acute Ischemic Stroke of Anticoagulated Patients-A Prospective Observational Study

BACKGROUND

Anticoagulated patients (APs) are excluded from the acute stroke management with alteplase in Europe, not in the United States. They could benefit from mechanical thrombectomy (MT), which was not undoubtedly proven. There are scarce data about its results in such patients. The authors' aim is to analyze the efficacy and safety of MT in APs presenting with an acute stroke in our institution.

METHODS

Prospective observational study comparing 30 APs and 109 non-anticoagulated patients (N-APs) underwent direct MT without alteplase. Demographic data, clinical severity (National Institutes of Health Stroke Scale [NIHSS]), efficacy (recanalization thrombolysis in cerebral infarction [TICI] ≥ 2b and modified Rankin Scale score ≤ 2 at 3 months), and security (symptomatic intracranial hemorrhage [SICH], mortality at 3 months) were compared between both groups.

RESULTS

In both groups men were more frequent (63.3% of APs were men and 61.5% of N-APs were men). Mean age was 73 in APs and 67.2 in N-APs. Median NIHSS was similar (17 APs; 16 N-APs), also TICI greater than or equal to 2b (93.3% APs; 89.9% N-APs). The 3-month modified Rankin Scale score less than or equal to 2 was 46.7% in APs and 55.2% in N-APs (P = .40). SICH was present in 16.7% of APs and 8.3% of N-APs (P = .15). Mortality at 3 months was 6.7% in APs and 19% in N-APs (P = .08).

CONCLUSIONS

MT is a valid treatment option in APs. It achieves an efficacy as in N-APs with a tendency to suffer more from SICH, but lower mortality. We hypothesize that cardioembolic clots may be easier to be removed than atherotrombotics, and that embolic stroke in APs might be less severe than that in N-APs or might suffer less of other complications than atherotrombotics.

Impact of Collateral Status on Successful Revascularization in Endovascular Treatment: A Systematic Review and Meta-Analysis

BACKGROUND

Pre-treatment collateral status may be associated with the rates of successful revascularization in acute ischemic stroke patients receiving endovascular treatment (EVT). We conducted a systematic review and meta-analysis to synthesize relevant evidence currently available.

METHODS

Relevant full-text articles published in English since January 1, 2000, reporting associations between collateral status and successful reperfusion and/or recanalization in acute ischemic stroke patients receiving EVT in cohort or case-control studies, or randomized clinical trials, were retrieved through search of PubMed. Study selection, data extraction and study quality assessment were carried out by 2 investigators. Risk ratios (RR) were pooled for good vs. poor collaterals for the outcomes of successful reperfusion and recanalization, based on random-effects models. Subgroup analyses were conducted to explore for potential factors that might interfere with the effects of pre-treatment collateral status on reperfusion by EVT.

RESULTS

In total, 27 studies (2,366 subjects) were included in qualitative analysis, among which 24 studies (2,239 subjects) were quantitatively analyzed. Overall, good pre-treatment collaterals significantly increased the rate of both successful reperfusion (RR 1.28, 95% CI 1.17-1.40; p < 0.001) and recanalization (RR 1.23, 95% CI 1.06-1.42; p = 0.006), as compared with poor collaterals. Subgroup analyses revealed that the effects of collateral status on successful reperfusion by EVT might be different between populations with different ethnicities.

CONCLUSIONS

Good pre-treatment collaterals may enhance the rates of successful reperfusion and recanalization in EVT for acute ischemic stroke. This may partly explain the favorable effects of good pre-treatment collaterals on clinical outcomes of stroke patients receiving EVT. Thus, it would be valuable to assess the collateral status prior to EVT in acute ischemic stroke. But studies are needed to further verify if the positive effects of good collaterals on revascularization by EVT are restricted to certain subgroups of patients.

Sex Differences in Long-Term Survival after a First Stroke with Intravenous Thrombolysis: Ebrictus Study

Background

A number of large trials have confirmed the benefits of thrombolysis in acute stroke, but there are gender differences. We sought to examine the relationship between sex and outcome after thrombolysis.

Methods

This was a prospective cohort study including 1,272 incident ischemic strokes (597 in women) from April 1, 2006 to December 31, 2014. Statistical approaches were used for analyzing survival outcomes and their relationship with thrombolysis therapy.

Results

The death rates were lower (p = 0.003) in the thrombolysis therapy group with an incidence ratio of 0.57 (95% CI 0.39-0.83). 113 (8.8%) patients (53 women) received thrombolysis. They were significantly younger (69.2 ± 12.7 vs. 73.9 ± 12.5 years; p < 0.001), had higher NIHSS score (12.7 ± 6.3 vs. 7.3 ± 7.0; p < 0.001), spent more days in hospital (10.4 ± 8.3 vs. 8.3 ± 7.9; p < 0.001), and had a higher average Barthel score at discharge (85.5 ± 24.4 vs. 79.2 ± 28.6; p = 0.023). The male/female incidence ratio showed a significant decrease (p = 0.01) in the incidence of mortality in women and a better Barthel score. The thrombolysis improved the survival in the overall group with thrombolysis versus without thrombolysis (p = 0.028), in women versus in men with thrombolysis (p = 0.023), and in women with thrombolysis versus in those without thrombolysis (p < 0.001) but not in men with thrombolysis versus in those without thrombolysis (p = 0.743). The protective factors as regards mortality were thrombolysis therapy (95% CI 0.37-0.80; p = 0.002), Barthel score ≥60 (95% CI 0.81-0.94; p = 0.002), and cardiovascular secondary prevention 1 year after stroke (0.13, 95% CI 0.06-0.28).

Conclusions

The stroke death rates were lower in women after thrombolysis treatment and suggest significant benefit for women in this setting. The overall benefit on survival of the patients treated with thrombolysis might be explained by the beneficial effect of the thrombolysis on the women.