Senescent cells are capable of expressing a myriad of inflammatory cytokines and this pro-inflammatory phenomenon is known as senescence-associated secretory phenotype (SASP). The contribution of this phenomenon in brain ischemia was scarce. A mouse model of transient focal cerebral ischemia by compressing the distal middle cerebral artery (tMCAo) for 60 min was used. SASP, pro-inflammatory cytokines and cell cycle mRNAs levels were quantified at 30-min and 72 h post-surgery. Immunohistochemistry in paraffin embedded human brain slides and mouse brain tissue was performed. Our results showed an increase of both p16 and p21 mRNA restricted to the infarct area in the tMCAo brain. Moreover, there was an induction of Il6, Tnfa, Cxc11, and its receptor Cxcr2 mRNA pro-inflammatory cytokines with a high positive correlation with p16/p21 mRNA levels. The p16 was mainly shown in cytoplasm of neurons and cytoplasm/membrane of microglial cells. The p21 was observed in membrane of neurons and also it showed a mixed cytoplasmic and membranous pattern in the microglial cells. In a human stroke patient, an increase of P16 in the perimeter of the MCA infarct area was observed. These suggest a role of SASP in tMCAo mouse model and in human brain tissue. SASP potentially has a physiological role in acute ischemic stroke and neurological function loss.

Remote ischemic conditioning (RIC) is a promising therapeutic approach for ischemic stroke patients. It has been proven that RIC reduces infarct size and improves functional outcomes. RIC can be applied either before ischemia (pre-conditioning; RIPreC), during ischemia (per-conditioning; RIPerC) or after ischemia (post-conditioning; RIPostC). Our aim was to systematically determine the efficacy of RIC in reducing infarct volumes and define the cellular pathways involved in preclinical animal models of ischemic stroke. A systematic search in three databases yielded 50 peer-review articles. Data were analyzed using random effects models and results expressed as percentage of reduction in infarct size (95% CI). A meta-regression was also performed to evaluate the effects of covariates on the pooled effect-size. 95.3% of analyzed experiments were carried out in rodents. Thirty-nine out of the 64 experiments studied RIPostC (61%), sixteen examined RIPreC (25%) and nine tested RIPerC (14%). In all studies, RIC was shown to reduce infarct volume (− 38.36%; CI − 42.09 to − 34.62%) when compared to controls. There was a significant interaction caused by species. Short cycles in mice significantly reduces infarct volume while in rats the opposite occurs. RIPreC was shown to be the most effective strategy in mice. The present meta-analysis suggests that RIC is more efficient in transient ischemia, using a smaller number of RIC cycles, applying larger length of limb occlusion, and employing barbiturates anesthetics. There is a preclinical evidence for RIC, it is safe and effective. However, the exact cellular pathways and underlying mechanisms are still not fully determined, and its definition will be crucial for the understanding of RIC mechanism of action.

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.

Rationale: Remote ischemic perconditioning during cerebral ischemia (RIPerC) refers to the application of brief episodes of transient limb ischemia commonly to a limb, it represents a new safe, simple and low-cost paradigm in neuroprotection. Aim and/or Hypothesis: To evaluate the effects of RIPerC on acute ischemic stroke (AIS) patients, applied in the ambulance, to improve functional outcomes compared with standard of care. Sample Size Estimates: A sample size of 286 patients in each arm achieves 80% power to detect treatment differences of 14% in the outcome, using a two-sided binomial test at significance level of 0.05, assuming that 40% of the control patients will experience good outcome and an initial misdiagnosis rate of 29%. Purroy et al. Remote-Cat Project Study Outcome(s): The primary outcome will be the difference in the proportion of patients with good outcomes as defined by a mRS score of 2 or less at 90 days. Secondary outcomes to be monitored will include early neurological improvement rate, treatment related serious adverse event rates, size of the infarct volume, symptomatic intracranial hemorrhage, metabolomic and lipidomic response to RIPerC and Neuropsychological evaluation at 90 days. Discussion: Neuroprotective therapies could not only increase the benefits of available reperfusion therapies among AIS patients but also provide an option for patients who are not candidates for these treatments. REMOTE-CAT will investigate the clinical benefit of RIC as a new neuroprotective strategy in AIS.