The effect of repeated remote ischemic postconditioning on infarct size in patients with an ischemic stroke (REPOST): study protocol for a randomized clinical trial

Efficacy and safety of remote ischemic conditioning for acute ischemic stroke: A comprehensive meta-analysis from randomized controlled trials

BACKGROUND AND PURPOSE

Remote ischemic conditioning (RIC) is a remote, transient, and noninvasive procedure providing temporary ischemia and reperfusion. However, there is no comprehensive literature investigating the efficacy and safety of RIC for the treatment of acute ischemic stroke. In the present study, we performed a comprehensive meta-analysis of the available studies.

METHODS

MEDLINE, Embase, the Cochrane Library database (CENTRAL), and ClinicalTrials.gov were searched before Sep 7, 2022. The data were analyzed using Review Manager 5.4.1 software, Stata version 16.0 software, and R 4.2.0 software. Odds ratio (OR), mean difference (MD), and corresponding 95% CIs were pooled using fixed-effects meta-analysis.

RESULTS

We pooled 6392 patients from 17 randomized controlled trials. Chronic RIC could reduce the recurrence of ischemic stroke at the endpoints (OR 0.67, 95% CI [0.51, 0.87]). RIC could also improve the prognosis of patients at 90 days as assessed by mRS score (mRS 0-1: OR 1.29, 95% CI [1.09, 1.52]; mRS 0-2: OR 1.22, 95% CI [1.01, 1.48]) and at the endpoints assessed by NIHSS score (MD -0.99, 95% CI [-1.45, -0.53]). RIC would not cause additional adverse events such as death (p = 0.72), intracerebral hemorrhage events (p = 0.69), pneumonia (p = 0.75), and TIA (p = 0.24) but would inevitably cause RIC-related adverse events (OR 26.79, 95% CI [12.08, 59.38]).

CONCLUSIONS

RIC could reduce the stroke recurrence and improve patients' prognosis. Intervention on bilateral upper limbs, 5 cycles, and a length of 50 min in each intervention might be an optimal protocol for RIC at present. RIC could be an effective therapy for patients not eligible for reperfusion therapy. RIC would not cause other adverse events except for relatively benign RIC-related adverse events.

The effect of repeated remote ischemic postconditioning after an ischemic stroke (REPOST): A randomized controlled trial

BACKGROUND AND AIMS

A potential strategy to treat ischemic stroke may be the application of repeated remote ischemic postconditioning (rIPostC). This consists of several cycles of brief periods of limb ischemia followed by reperfusion, which can be applied by inflating a simple blood pressure cuff and subsequently could result in neuroprotection after stroke.

METHODS

Adult patients admitted with an ischemic stroke in the past 24 h were randomized 1:1 to repeated rIPostC or sham-conditioning. Repeated rIPostC was performed by inflating a blood pressure cuff around the upper arm (4 × 5 min at 200 mm Hg), which was repeated twice daily during hospitalization with a maximum of 4 days. Primary outcome was infarct size after 4 days or at discharge. Secondary outcomes included the modified Rankin Scale (mRS)-score after 12 weeks and the National Institutes of Health Stroke Scale (NIHSS) at discharge.

RESULTS

The trial was preliminarily stopped after we included 88 of the scheduled 180 patients (average age: 70 years, 68% male) into rIPostC (n = 40) and sham-conditioning (n = 48). Median infarct volume was 2.19 mL in rIPostC group and 5.90 mL in sham-conditioning, which was not significantly different between the two groups (median difference: 3.71; 95% CI: -0.56 to 6.09; p = 0.31). We found no significant shift in the mRS score distribution between groups. The adjusted common odds ratio was 2.09 (95% CI: 0.88-5.00). We found no significant difference in the NIHSS score between groups (median difference: 1.00; 95% CI: -0.99 to 1.40; p = 0.51).

CONCLUSION

This study found no significant improvement in infarct size or clinical outcome in patients with an acute ischemic stroke who were treated with repeated remote ischemic postconditioning. However, due to a lower-than-expected inclusion rate, no definitive conclusions about the effectiveness of rIPostC can be drawn.

Improving the ischemia-reperfusion injury in vascularized composite allotransplantation: Clinical experience and experimental implications

Long-time ischemia worsening transplant outcomes in vascularized composite allotransplantation (VCA) is often neglected. Ischemia-reperfusion injury (IRI) is an inevitable event that follows reperfusion after a period of cold static storage. The pathophysiological mechanism activates local inflammation, which is a barrier to allograft long-term immune tolerance. The previous publications have not clearly described the relationship between the tissue damage and ischemia time, nor the rejection grade. In this review, we found that the rejection episodes and rejection grade are usually related to the ischemia time, both in clinical and experimental aspects. Moreover, we summarized the potential therapeutic measures to mitigate the ischemia-reperfusion injury. Compare to static preservation, machine perfusion is a promising method that can keep VCA tissue viability and extend preservation time, which is especially beneficial for the expansion of the donor pool and better MHC-matching.

A Narrative Review on Translational Research in Acute Brain Injury

There has been a constant endeavor to reduce the mortality and morbidity associated with acute brain injury. The associated complex mechanisms involving biomechanics, markers, and neuroprotective drugs/measures have been extensively studied in preclinical studies with an ultimate aim to improve the patients' outcomes. Despite such efforts, only few have been successfully translated into clinical practice. In this review, we shall be discussing the major hurdles in the translation of preclinical results into clinical practice. The need is to choose an appropriate animal model, keeping in mind the species, age, and gender of the animal, choosing suitable outcome measures, ensuring quality of animal trials, and carrying out systematic review and meta-analysis of experimental studies before proceeding to human trials. The interdisciplinary collaboration between the preclinical and clinical scientists will help to design better, meaningful trials which might help a long way in successful translation. Although challenging at this stage, the advent of translational precision medicine will help the integration of mechanism-centric translational medicine and patient-centric precision medicine.

Remote Ischemic Conditioning in Ischemic Stroke and Myocardial Infarction: Similarities and Differences

Acute myocardial infarction and ischemic stroke are leading causes of morbidity and mortality worldwide. Although reperfusion therapies have greatly improved the outcomes of patients with these conditions, many patients die or are severely disabled despite complete reperfusion. It is therefore important to identify interventions that can prevent progression to ischemic necrosis and limit ischemia-reperfusion injury. A possible strategy is ischemic conditioning, which consists of inducing ischemia – either in the ischemic organ or in another body site [i.e., remote ischemic conditioning (RIC), e.g., by inflating a cuff around the patient's arm or leg]. The effects of ischemic conditioning have been studied, alone or in combination with revascularization techniques. Based on the timing (before, during, or after ischemia), RIC is classified as pre-, per-/peri-, or post-conditioning, respectively. In this review, we first highlight some pathophysiological and clinical similarities and differences between cardiac and cerebral ischemia. We report evidence that RIC reduces circulating biomarkers of myocardial necrosis, infarct size, and edema, although this effect appears not to translate into a better prognosis. We then review cutting-edge applications of RIC for the treatment of ischemic stroke. We also highlight that, although RIC is a safe procedure that can easily be implemented in hospital and pre-hospital settings, its efficacy in patients with ischemic stroke remains to be proven. We then discuss possible methodological issues of previous studies. We finish by highlighting some perspectives for future research, aimed at increasing the efficacy of ischemic conditioning for improving tissue protection and clinical outcomes, and stratifying myocardial infarction and brain ischemia patients to enhance treatment feasibility.

Emerging Role of microRNAs in Stroke Protection Elicited by Remote Postconditioning

Remote ischemic conditioning (RIC) represents an innovative and attractive neuroprotective approach in brain ischemia. The purpose of this intervention is to activate endogenous tolerance mechanisms by inflicting a subliminal ischemia injury to the limbs, or to another “remote” region, leading to a protective systemic response against ischemic brain injury. Among the multiple candidates that have been proposed as putative mediators of the protective effect generated by the subthreshold peripheral ischemic insult, it has been hypothesized that microRNAs may play a vital role in the infarct-sparing effect of RIC. The effect of miRNAs can be exploited at different levels: (1) as transducers of protective messages to the brain or (2) as effectors of brain protection. The purpose of the present review is to summarize the most recent evidence supporting the involvement of microRNAs in brain protection elicited by remote conditioning, highlighting potential and pitfalls in their exploitation as diagnostic and therapeutic tools. The understanding of these processes could help provide light on the molecular pathways involved in brain protection for the future development of miRNA-based theranostic agents in stroke.

Remote but not Distant: a Review on Experimental Models and Clinical Trials in Remote Ischemic Conditioning as Potential Therapy in Ischemic Stroke

Stroke is one of the main causes of neurological disability worldwide and the second cause of death in people over 65 years old, resulting in great economic and social burden. Ischemic stroke accounts for 85% of total cases, and the approved therapies are based on re-establishment of blood flow, and do not directly target brain parenchyma. Thus, novel therapies are urgently needed. In this review, limb remote ischemic conditioning (RIC) is revised and discussed as a potential therapy against ischemic stroke. The review targets both (i) fundamental research based on experimental models and (ii) clinical research based on clinical trials and human interventional studies with healthy volunteers. Moreover, it also presents two approaches concerning RIC mechanisms in stroke: (i) description of the underlying cerebral cellular and molecular mechanisms triggered by limb RIC that promote neuroprotection against stroke induced damage and (ii) the identification of signaling factors involved in inter-organ communication following RIC procedure. Limb to brain remote signaling can occur via circulating biochemical factors, immune cells, and/or stimulation of autonomic nervous system. In this review, these three hypotheses are explored in both humans and experimental models. Finally, the challenges involved in translating experimentally generated scientific knowledge to a clinical setting are also discussed.

Impact of repeated remote ischemic conditioning on diabetic foot ulcers: A proof-of-concept study

Patients with a diabetic foot ulcer (DFU) suffer disabilities and are at increased risk for lower extremity amputation. Current standard of care includes debridement, topical antibiotics, and weight off-loading-still resulting in low rates of healing. Previous small-scale research has indicated that repeated remote ischemic conditioning (rRIC) is a novel modality that delivers significantly higher DFU healing rates. This proof-of-concept study was performed to expand the research on the utility of rRIC as an adjunctive treatment in the healing of chronic DFUs. Forty subjects (41 wounds) received rRIC treatment three times weekly in addition to standard of care for 12 weeks. Subjects that did not heal in this time frame but had a significant reduction in wound size were eligible to continue for an 8-week extension period. By the end of the extension period, 31 of the 41 DFU wounds (75.6%) in this study were determined to be healed. This compares favourably to the 25-30% standard of care average healing rate. For additional comparison, another group of patients receiving standard of care alone, by the same investigator, was selected and matched by wound size at baseline and wound location. For this matching cohort, after 20 weeks of treatment, only 15 of the 41 DFU comparison wounds (36.6%) were determined to be healed, in line with other standard of care results. In the rRIC treatment group, the 10 wounds that did not heal, experienced an average reduction in wound area of 54.3%. The results of this proof-of-concept study reinforce earlier evidence that the addition of rRIC to local wound care significantly improves the healing of chronic diabetic foot ulcers.

Remote Ischemic Postconditioning vs. Physical Exercise After Stroke: an Alternative Rehabilitation Strategy?

There remain debates on neuroprotection and rehabilitation techniques for acute ischemic stroke patients. Therapeutic physical exercise following stroke has shown promise but is challenging to apply clinically. Ischemic conditioning, which has several clinical advantages, is a potential neuroprotective method for stroke rehabilitation that is less understood. In the present study, the rehabilitative properties and mechanisms of physical exercise and remote ischemic postconditioning (RIPostC) after stroke were compared and determined. A total of 248 adult male Sprague-Dawley rats were divided into five groups: (1) sham, (2) stroke, (3) stroke with intense treadmill exercise, (4) stroke with mild treadmill exercise, and (5) stroke with RIPostC. Focal ischemia was evaluated by infarct volume and neurological deficit. Long-term functional outcomes were represented through neurobehavioral function tests: adhesive removal, beam balance, forelimb placing, grid walk, rota-rod, and Morris water maze. To further understand the mechanisms underlying neurorehabilitation and verify the presence thereof, we measured mRNA and protein levels of neuroplasticity factors, synaptic proteins, angiogenesis factors, and regulation molecules, including HIF-1α, BDNF, TrkB, and CREB. The key role of HIF-1α was elucidated by using the inhibitor, YC-1. Both exercise intensities and RIPostC significantly decreased infarct volumes and neurological deficits and outperformed the stroke group in the neurobehavioral function tests. All treatment groups showed significant increases in mRNA and protein expression levels of the target molecules for neurogenesis, synaptogenesis, and angiogenesis, with intermittent further increases in the RIPostC group. HIF-1α inhibition nullified most beneficial effects and indicative molecule expressions, including HIF-1α, BDNF, TrkB, and CREB, in both procedures. RIPostC is equally, or superiorly, effective in inducing neuroprotection and rehabilitation compared to exercise in ischemic rats. HIF-1α likely plays an important role in the efficacy of neuroplasticity conditioning, possibly through HIF-1α/BDNF/TrkB/CREB regulation.

Neuroprotective Effects of Exercise Postconditioning After Stroke via SIRT1-Mediated Suppression of Endoplasmic Reticulum (ER) Stress

While it is well-known that pre-stroke exercise conditioning reduces the incidence of stroke and the development of comorbidities, it is unclear whether post-stroke exercise conditioning is also neuroprotective. The present study investigated whether exercise postconditioning (PostE) induced neuroprotection and elucidated the involvement of SIRT1 regulation on the ROS/ER stress pathway. Adult rats were subjected to middle cerebral artery occlusion (MCAO) followed by either: (1) resting; (2) mild exercise postconditioning (MPostE); or (3) intense exercise postconditioning (IPostE). PostE was initiated 24 h after reperfusion and performed on a treadmill. At 1 and 3 days thereafter, we determined infarct volumes, neurological defects, brain edema, apoptotic cell death through measuring pro- (BAX and Caspase-3) and anti-apoptotic (Bcl-2) proteins, and ER stress through the measurement of glucose-regulated protein 78 (GRP78), inositol-requiring 1α (IRE1α), protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), Caspase-12, and SIRT1. Proteins were measured by Western blot. ROS production was detected by flow cytometry.Compared to resting rats, both MPostE and IPostE significantly decreased brain infarct volumes and edema, neurological deficits, ROS production, and apoptotic cell death. MPostE further increased Bcl-2 expression and Bcl-2/BAX ratio as well as BAX and Caspase-3 expressions and ROS production (*p < 0.05). Both PostE groups saw decreases in ER stress proteins, while MPostE demonstrated a further reduction in GRP78 (***p < 0.001) and Caspase-12 (*p < 0.05) expressions at 1 day and IRE1α (**p < 0.01) and CHOP (*p < 0.05) expressions at 3 days. Additionally, both PostE groups saw significant increases in SIRT1 expression.In this study, both mild and intense PostE levels induced neuroprotection after stroke through SIRT1 and ROS/ER stress pathway. Additionally, the results may provide a base for our future study regarding the regulation of SIRT1 on the ROS/ER stress pathway in the biochemical processes underlying post-stroke neuroprotection. The results suggest that mild exercise postconditioning might play a similar neuroprotective role as intensive exercise and could be an effective exercise strategy as well.

Remote Ischemic Post-Conditioning may Improve Post-Stroke Cognitive Impairment: A Pilot Single Center Randomized Controlled Trial

BACKGROUND AND PURPOSE

We aimed to demonstrate the tolerability and feasibility and the effect of remote ischemic post-conditioning on cognitive functioning in patients with post-stroke cognitive impairment.

METHODS

This was a single-center, randomized, outcome-blinded, placebo-controlled trial, randomized 1:1 to receive 4 cycles of remote ischemic post-conditioning or a sham procedure for 7 days. The primary outcome measure was tolerability and feasibility of remote ischemic post-conditioning. Secondary outcomes to measure the neurological function with national institute of health stroke scale and the cognitive impairment with Montreal Cognitive Assessment scale and Alzheimer's disease assessment scale-cognitive (at baseline, 90 days, 180 days).

RESULTS

48 patients (24 RIPC and 24 Control) were recruited. remote ischemic post-conditioning was well tolerated with 90 out of 96 cycles completed in full. 4 patients experienced vascular events in the control group: 3 cerebrovascular and 1 cardiovascular event versus only 2 cerebrovascular events in the RIPC group. We showed the similar result in the neurological function with national institute of health stroke scale score with no statistically significant differences between RIPC and control group at baseline (P = 0.796) and 90 days (P = 0.401) and 180 days (P = 0.695). But compare with baseline, it was significantly difference in the control and RIPC group at 90 days (P < 0.05) and 180 days (P < 0.05). The comparison of Montreal Cognitive Assessment scale between two groups both showed that P > 0.05 at baseline which was no statistical difference, but P < 0.05 at 90 days and 180 days which were significant statistical difference. The comparison of Alzheimer's disease assessment scale-cognitive between two groups showed that P > 0.05 at baseline (P = 0.955) and 90 days (P = 0.138) was no statistical difference, but P = 0.005<0.05 at 180 days was significant statistical difference.

CONCLUSIONS

The remote ischemic post-conditioning for post-stroke cognitive impairment was well tolerated, safe and feasible. The remote ischemic post-conditioning may improve neurological and cognitive outcomes in patients with post-stroke cognitive impairment. A larger trial is warranted. (Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: ChiCTR1800015231.).

Remote Ischemic Conditioning in Acute Ischemic Stroke - A Clinical Trial Design

Remote ischemic conditioning represents an intervention based on blood flow reduction applied at a distance from the lesion. The mechanism is supposed to elicit neurovascular protection, anti-inflammatory action, reduced excitotoxicity and metabolic protection. This study aims to explore the efficiency and safety of remote ischemic conditioning during the first five days following in patients who are ineligible for reperfusion treatment (intravenous thrombolysis or/and mechanical thrombectomy). We hypothesized that this intervention would reduce the infarct size (neuroprotection in the reperfusion window) and improve functional recovery. We aim to conduct a double-blind controlled trial, multicenter in two hospitals in Romania. Two hundred patients with acute ischemic stroke randomly divided into an experimental group and a control group will be included. The subjects in the experimental group will be subjected to remote ischemic conditioning twice daily with a maximum of 180 mmHg for 5 days, and a guideline- based treatment as well. The subjects in the control group will receive cuff inflation to 30 mmHg, which will induce sham preconditioning. The primary outcome measure will be radiological - the difference between baseline brain infarct volume and the volume at 180 days in the experimental group versus the control group. The second outcome considers clinical scores such as NIHSS, mRS, IADL, ADL, MOCA, PHQ-9 at baseline, 90 and 180 days; tolerance and side effects of remote ischemic conditioning; the reccurence of stroke or other vascular events at 180 days; incidence of stroke-associated comorbidities and the proportion of death of any cause within 180 days.

Induced neuroprotection by remote ischemic perconditioning as a new paradigm in ischemic stroke at the acute phase, a systematic review

BACKGROUND

Remote ischemic conditioning during cerebral ischemia (remote ischemic perconditioning, RIPerC) refers to the application of several cycles of brief ischemia and reperfusion (I/R) commonly to a limb, and it represents a new paradigm in neuroprotection with multiple mechanisms of action in ischemic stroke (IS) patients during acute phase. Some clinical trials just finished, and a few others are still ongoing; gather the current knowledge and pull it down to influence the present and future studies was the goal of this paper.

METHODS

A systematic review of published research papers and/or registered clinical trials since 2000 was performed.

RESULTS

Nineteen studies were identified and only four studies were completed. All of them have demonstrated that RIPerC is safe, feasible and well tolerated in IS patients. However, a high heterogeneity of clinical trial characteristics was observed: five (26.3%) randomized clinical trials (RCTs) included only thrombolytic-treated patients, three (15.8%) RCTs only thrombectomy-treated patients, and five (26.3%) RCTs required radiological confirmation of IS. Temporal inclusion criteria vary from 4 h to 48 h. Most of the clinical trials used 4 cycles of RIPerC in the upper non-affected limb. Interestingly, only three (16.7%) RCTs applied RIPerC during the transportation in the ambulance. Neuroimaging outputs were the main endpoints when endovascular therapy was applied; functional outcome is also the main endpoint in large-medium size studies.

CONCLUSIONS

This review summarizes the completed and ongoing clinical trials on RIPerC in IS patients, where RIPerC has been used alone or in combination with recanalization therapies. Ongoing clinical trials will provide new information on the best RIPerC intervention strategy and potentially improve the functional outcome of IS patients; definition of new RIPerC strategies would ideally aim at enhancing tissue preservation, promoting neurological recovery, and stratify patients to improve treatment feasibility.