Pharmacologic reduction of angiographic vasospasm in experimental subarachnoid hemorrhage: systematic review and meta-analysis

Analysis of animal-to-human translation shows that only 5% of animal-tested therapeutic interventions obtain regulatory approval for human applications

There is an ongoing debate about the value of animal experiments to inform medical practice, yet there are limited data on how well therapies developed in animal studies translate to humans. We aimed to assess 2 measures of translation across various biomedical fields: (1) The proportion of therapies which transition from animal studies to human application, including involved timeframes; and (2) the consistency between animal and human study results. Thus, we conducted an umbrella review, including English systematic reviews that evaluated the translation of therapies from animals to humans. Medline, Embase, and Web of Science Core Collection were searched from inception until August 1, 2023. We assessed the proportion of therapeutic interventions advancing to any human study, a randomized controlled trial (RCT), and regulatory approval. We meta-analyzed the concordance between animal and human studies. The risk of bias was probed using a 10-item checklist for systematic reviews. We included 122 articles, describing 54 distinct human diseases and 367 therapeutic interventions. Neurological diseases were the focus of 32% of reviews. The overall proportion of therapies progressing from animal studies was 50% to human studies, 40% to RCTs, and 5% to regulatory approval. Notably, our meta-analysis showed an 86% concordance between positive results in animal and clinical studies. The median transition times from animal studies were 5, 7, and 10 years to reach any human study, an RCT, and regulatory approval, respectively. We conclude that, contrary to widespread assertions, the rate of successful animal-to-human translation may be higher than previously reported. Nonetheless, the low rate of final approval indicates potential deficiencies in the design of both animal studies and early clinical trials. To ameliorate the efficacy of translating therapies from bench to bedside, we advocate for enhanced study design robustness and the reinforcement of generalizability.

Advanced methods and implementations for the meta-analyses of animal models: Current practices and future recommendations

Meta-analytic techniques have been widely used to synthesize data from animal models of human diseases and conditions, but these analyses often face two statistical challenges due to complex nature of animal data (e.g., multiple effect sizes and multiple species): statistical dependency and confounding heterogeneity. These challenges can lead to unreliable and less informative evidence, which hinders the translation of findings from animal to human studies. We present a literature survey of meta-analysis using animal models (animal meta-analysis), showing that these issues are not adequately addressed in current practice. To address these challenges, we propose a meta-analytic framework based on multilevel (linear mixed-effects) models. Through conceptualization, formulations, and worked examples, we illustrate how this framework can appropriately address these issues while allowing for testing new questions. Additionally, we introduce other advanced techniques such as multivariate models, robust variance estimation, and meta-analysis of emergent effect sizes, which can deliver robust inferences and novel biological insights. We also provide a tutorial with annotated R code to demonstrate the implementation of these techniques.

Angiotensin-(1-7) as a Potential Therapeutic Strategy for Delayed Cerebral Ischemia in Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a substantial cause of mortality and morbidity worldwide. Moreover, survivors after the initial bleeding are often subject to secondary brain injuries and delayed cerebral ischemia, further increasing the risk of a poor outcome. In recent years, the renin-angiotensin system (RAS) has been proposed as a target pathway for therapeutic interventions after brain injury. The RAS is a complex system of biochemical reactions critical for several systemic functions, namely, inflammation, vascular tone, endothelial activation, water balance, fibrosis, and apoptosis. The RAS system is classically divided into a pro-inflammatory axis, mediated by angiotensin (Ang)-II and its specific receptor AT₁R, and a counterbalancing system, presented in humans as Ang-(1-7) and its receptor, MasR. Experimental data suggest that upregulation of the Ang-(1-7)/MasR axis might be neuroprotective in numerous pathological conditions, namely, ischemic stroke, cognitive disorders, Parkinson's disease, and depression. In the presence of SAH, Ang-(1-7)/MasR neuroprotective and modulating properties could help reduce brain damage by acting on neuroinflammation, and through direct vascular and anti-thrombotic effects. Here we review the role of RAS in brain ischemia, with specific focus on SAH and the therapeutic potential of Ang-(1-7).

Valproic Acid Reduces Vasospasm through Modulation of Akt Phosphorylation and Attenuates Neuronal Apoptosis in Subarachnoid Hemorrhage Rats

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating emergent event associated with high mortality and morbidity. Survivors usually experience functional neurological sequelae caused by vasospasm-related delayed ischemia. In this study, male Sprague-Dawley rats were randomly assigned to five groups: sham (non-SAH) group, SAH group, and three groups with SAH treated with different doses of valproic acid (VPA) (10, 20, 40 mg/kg, once-daily, for 7 days). The severity of vasospasm was determined by the ratio of cross-sectional areas to intima-media thickness of the basilar arteries (BA) on the seventh day after SAH. The BA showed decreased expression of phospho-Akt proteins. The dentate gyrus showed increased expression of cleaved caspase-3 and Bax proteins and decreased expression of Bcl-2, phospho-ERK 1/2, phospho-Akt and acetyl-histone H3 proteins. The incidence of SAH-induced vasospasm was significantly lower in the SAH group treated with VPA 40 mg/kg (p < 0.001). Moreover, all groups treated with VPA showed reversal of the above-mentioned protein expression in BA and the dentate gyrus. Treatment with VPA upregulated histone H3 acetylation and conferred anti-vasospastic and neuro-protective effects by enhancing Akt and/or ERK phosphorylation. This study demonstrated that VPA could alleviate delayed cerebral vasospasm induced neuro-apoptosis after SAH.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need

BACKGROUND

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish.

METHODS

Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits.

RESULTS

We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility.

CONCLUSIONS

To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Natural Cerebral Aneurysm and Spontaneous Subarachnoid Hemorrhage in Mammals Other Than Man: Is There a Scope for Comparative Medicine?

BACKGROUND

Concepts that showed substantial efficacy in animal models of subarachnoid hemorrhage (SAH) often failed to improve outcome in humans with aneurysmal SAH. The concept of "comparative medicine," an open-minded comparison across species, might offer an alternative to the "constructed" animal models' approach. Naturally occurring diseases in animals might bear more similarity to human diseases than models. In this context, the question arises whether spontaneous intracranial aneurysms exist in animals or not, and whether they cause SAH or not.

METHODS

A systematic literature search was performed. Only articles dealing with natural aneurysms and/or SAH of mammals other than man were included. All articles dealing with induced aneurysms and/or SAH were removed.

RESULTS

Of 2812 screened articles, 9 articles describing natural intracranial aneurysms and/or SAH were found. In total 1979 individual animals of 29 species were examined. Natural intracranial aneurysms were described in 7 individual animals of 6 species. Spontaneous SAH was described in 3 species. In 1 chimpanzee, a ruptured intracranial aneurysm caused an SAH. Histological descriptions of the aneurysms were strikingly similar to those of humans.

CONCLUSIONS

Although interesting and innovative, the concept of "comparative medicine" seems to be impracticable due to the seemingly ultralow incidence of natural aneurysmal SAH in mammals other than man. The answer to the question "why intracranial aneurysms are less common in animals despite the strong histological similarity of cerebral arteries" might be a key issue. Last but not least, primates likely matter in SAH-related research, as aneurysmal SAH occurs in primates.

Apolipoprotein E mimetic peptide CN-105 improves outcome in a murine model of SAH

Objective

Subarachnoid haemorrhage (SAH) accounts for 3% of all strokes, and is associated with significant morbidity and mortality. There is growing evidence implicating apolipoprotein E (apoE) in mediating adaptive anti-inflammatory and neuroprotective responses following ischaemic and traumatic brain injury. In the current study, we test the efficacy of a small apoE mimetic peptide, CN-105 in a murine model of SAH.

Methods

Mice subjected to SAH received repeated intravenous injections of CN-105 every 12 hours for 3 days, with the first dose given 2 hours after injury. Daily functional outcomes were assessed by rotarod and neurological severity score. Haemorrhage grade and cerebral vascular diameters were measured at 5 days post-SAH. Cerebral microgliosis, neuronal degeneration and survival were analysed at 5 and 35 days post-SAH, respectively.

Results

CN-105 reduces histological evidence of inflammation, reduces vasospasm and neuronal injury and is associated with improved long-term behavioural outcomes in a murine model of SAH.

Conclusions

Given its favourable pharmacokinetic profile, central nervous system penetration and demonstration of clinical safety, CN-105 represents an attractive therapeutic candidate for treatment of brain injury associated with SAH.

Brain endothelial cell junctions after cerebral hemorrhage: Changes, mechanisms and therapeutic targets

Vascular disruption is the underlying cause of cerebral hemorrhage, including intracerebral, subarachnoid and intraventricular hemorrhage. The disease etiology also involves cerebral hemorrhage-induced blood-brain barrier (BBB) disruption, which contributes an important component to brain injury after the initial cerebral hemorrhage. BBB loss drives vasogenic edema, allows leukocyte extravasation and may lead to the entry of potentially neurotoxic and vasoactive compounds into brain. This review summarizes current information on changes in brain endothelial junction proteins in response to cerebral hemorrhage (and clot-related factors), the mechanisms underlying junction modification and potential therapeutic targets to limit BBB disruption and, potentially, hemorrhage occurrence. It also addresses advances in the tools that are now available for assessing changes in junctions after cerebral hemorrhage and the potential importance of such junction changes. Recent studies suggest post-translational modification, conformational change and intracellular trafficking of junctional proteins may alter barrier properties. Understanding how cerebral hemorrhage alters BBB properties beyond changes in tight junction protein loss may provide important therapeutic insights to prevent BBB dysfunction and restore normal function.

Severity assessment and scoring for neurosurgical models in rodents

The most important acute neurological diseases seen at neurosurgery departments are traumatic brain injuries (TBI) and subarachnoid hemorrhages (SAH). In both diseases the pathophysiological sequela are complex and have not been fully understood up to now, and rodent models using rats and mice are most suitable for the investigation of the pathophysiological details. In both models, surgery is performed under anesthesia, followed by assessment of their functional outcome and behavioral testing before brain tissue analysis after euthanasia. Postoperative analgesia is mandatory, and supplementary care is highly recommended for refinement purposes. Pain and stress assessment is mainly based on clinical and behavioral signs, and further research is needed to improve the evaluation of severity in these models.

Effect of endothelin receptor antagonists on clinically relevant outcomes after experimental subarachnoid hemorrhage: a systematic review and meta-analysis

In clinical trials, endothelin receptor antagonists (ETRAs) reduced vasospasm but did not improve functional outcome after subarachnoid hemorrhage (SAH). We assessed the effects of treatment with ETRAs on clinically relevant outcomes in animal studies modelling SAH by performing a systematic review of the literature for controlled animal studies of ETRAs for the treatment of SAH. Primary outcomes were neurobehavioral outcomes and case fatality. Secondary outcomes were cerebral vasospasm and cerebral blood flow. Summary estimates were calculated using normalized mean difference random effects meta-analysis. We included 27 studies (55 experiments, 639 animals). Neurobehavioral scores were reported in none of the experiments, and case fatality in 8 (15%). Treatment with ETRAs was associated with a pooled odds ratio for case fatality of 0.61 (95% confidence interval (CI), 0.27 to 1.39); a 54% increase (95% CI, 39 to 69) in cerebral arterial diameter; and a 93% increase (95% CI, 58 to 129) in cerebral blood flow. We conclude that there is no evidence from animal studies that treatment with an ETRA improves clinically relevant outcomes after SAH. The reduction in cerebral vasospasm observed in animal studies is consistent with that observed in clinical trials, an effect that is not associated with better functional outcome in patients.

Hydrogen-Rich Saline Attenuated Subarachnoid Hemorrhage-Induced Early Brain Injury in Rats by Suppressing Inflammatory Response: Possible Involvement of NF-κB Pathway and NLRP3 Inflammasome

Early brain injury (EBI), highlighted with inflammation and apoptosis, occurring within 72 h after subarachnoid hemorrhage (SAH), is associated with the prognosis of SAH. Recent studies have revealed that hydrogen-rich saline (HS) exerted multiple neuroprotective properties in many neurological diseases including SAH, involved to anti-oxidative and anti-apoptotic effect. We have previously reported that HS could attenuate neuronal apoptosis as well as vasospasm. However, the underlying mechanism of HS on inflammation in SAH-induced EBI remains unclear. In this study, we explored the influence of HS on nuclear factor-κB (NF-κB) pathway and nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome at early stage after SAH, by injecting HS intraperitoneally to SAH rats. One hundred and twenty-nine SD rats were randomly divided into four groups: sham group, SAH group, SAH+vehicle group, and SAH+HS group. SAH model was conducted using endovascular perforation method; all rats were sacrificed at 24 h after SAH. Protein level of pIκBα, cytosolic and nuclear p65, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, interleukin-1β (IL-1β), and cleaved caspase-3 were measured by western blot. mRNA level of IL-1β, interleukin-6 (IL-6), tumor necrosis factor-c (TNF-α) were evaluated by RT-PCR. Cellular injury and death was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Nissl staining, respectively. Our results showed that pIκBα, nuclear p65, NLRP3, ASC, caspase-1, IL-1β, cleaved caspase-3 proteins, as well as the mRNA of IL-1β, IL-6, and TNF-ɑ increased at 24 h after SAH, while cytosolic p65 decreased. TUNEL and Nissl staining presented severe cellular injury at 24 h post-SAH. However, after HS administration, the changes mentioned above were reversed. In conclusion, HS may inhibit inflammation in EBI and improve neurobehavioral outcome after SAH, partially via inactivation of NF-κB pathway and NLRP3 inflammasome. Graphical Abstract Schematic representation of the mechanism of HS-mediated anti-inflammatory effect in EBI after SAH. The NF-κB inflammatory pathway and NLRP3 inflammasome are involved in the anti-neuroinflammatory effect of HS post-SAH. SAH-induced oxidative stress enhances the activation of NF-κB, thus promoting the translocation of p65 subunit into nucleus and increasing the mRNA level of its downstream proinflammatory cytokines (IL-1β, IN-6, TNF-α) and NLRP3. Elevated expression of NLRP3 mRNA increases the assembly of NLRP3 inflammasome. In addition, oxidative stress after SAH stimulates the activation of NLRP3 inflammasome, therefore, promoting caspase-1 activation and the cleavage of pro-IL-1β into mature IL-1β. Finally, activation of NF-κB pathway and NLRP3 inflammasome contribute to the inflammation response and cellular injury in EBI after SAH. HS treatment reversed the detrimental effect mentioned above via inactivation of NF-κB pathway and NLRP3 inflammasome. NF-κB nuclear factor-κB, IκB inhibitor of NF-κB, IKK Iκ kinase, NLRP3 nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3, ASC apoptosis-associated speck-like protein containing a caspase recruitment domain.

MEK1/2 inhibitor U0126 but not endothelin receptor antagonist clazosentan reduces upregulation of cerebrovascular contractile receptors and delayed cerebral ischemia, and improves outcome after subarachnoid hemorrhage in rats

Cerebral vasospasm and late cerebral ischemia (LCI) remain leading causes of mortality in patients experiencing a subarachnoid hemorrhage (SAH). This occurs typically 3 to 4 days after the initial bleeding and peaks at 5 to 7 days. The underlying pathophysiology is still poorly understood. Because SAH is associated with elevated levels of endothelin-1 (ET-1), focus has been on counteracting endothelin receptor activation with receptor antagonists like clazosentan, however, with poor outcome in clinical trials. We hypothesize that inhibition of intracellular transcription signaling will be an effective approach to prevent LCI. Here, we compare the effects of clazosentan versus the MEK1/2 blocker U0126 in a rat model of SAH. Although clazosentan directly inhibits the contractile responses in vivo to ET-1, it did not prevent SAH-induced upregulation of ET receptors in cerebral arteries and did not show a beneficial effect on neurologic outcome. U0126 had no vasomotor effect by itself but counteracts SAH-induced receptor upregulation in cerebral arteries and improved outcome after SAH. We suggest that because SAH induces elevated expression of several contractile receptor subtypes, it is not sufficient to block only one of these (ET receptors) but inhibition of transcriptional MEK1/2-mediated upregulation of several contractile receptors may be a viable way towards alleviating LCI.

Endovascular perforation subarachnoid hemorrhage fails to cause Morris water maze deficits in the mouse

Cognitive dysfunction is the primary driver of poor long-term outcome in aneurysmal subarachnoid hemorrhage (SAH) survivors; modeling such deficits preclinically is thus key for mechanistic and translational investigation. Although rat SAH causes long-term deficits in learning and memory, it remains unknown whether similar deficits are seen in the mouse, a species particularly amenable to powerful, targeted genetic manipulation. We thus subjected mice to endovascular perforation SAH and assessed long-term cognitive outcome via the Morris water maze (MWM), the most commonly used metric for rodent neurocognition. No significant differences in MWM performance (by either of two protocols) were seen in SAH versus sham mice. Moreover, SAH caused negligible hippocampal CA1 injury. These results undercut the potential of commonly used methods (of SAH induction and assessment of long-term neurocognitive outcome) for use in targeted molecular studies of SAH-induced cognitive deficits in the mouse.

The cross-talk between canonical and non-canonical Wnt-dependent pathways regulates P-glycoprotein expression in human blood-brain barrier cells

In this work, we investigate if and how transducers of the 'canonical' Wnt pathway, i.e., Wnt/glycogen synthase kinase 3 (GSK3)/β-catenin, and transducers of the 'non-canonical' Wnt pathway, i.e., Wnt/RhoA/RhoA kinase (RhoAK), cooperate to control the expression of P-glycoprotein (Pgp) in blood-brain barrier (BBB) cells. By analyzing human primary brain microvascular endothelial cells constitutively activated for RhoA, silenced for RhoA or treated with the RhoAK inhibitor Y27632, we found that RhoAK phosphorylated and activated the protein tyrosine phosphatase 1B (PTP1B), which dephosphorylated tyrosine 216 of GSK3, decreasing the GSK3-mediated inhibition of β-catenin. By contrast, the inhibition of RhoA/RhoAK axis prevented the activation of PTP1B, enhanced the GSK3-induced phosphorylation and ubiquitination of β-catenin, and reduced the β-catenin-driven transcription of Pgp. The RhoAK inhibition increased the delivery of Pgp substrates like doxorubicin across the BBB and improved the doxorubicin efficacy against glioblastoma cells co-cultured under a BBB monolayer. Our data demonstrate that in human BBB cells the expression of Pgp is controlled by a cross-talk between canonical and non-canonical Wnt pathways. The disruption of this cross-talk, e.g., by inhibiting RhoAK, downregulates Pgp and increases the delivery of Pgp substrates across the BBB.

Aneurysmal subarachnoid hemorrhage models: do they need a fix?

The discovery of tissue plasminogen activator to treat acute stroke is a success story of research on preventing brain injury following transient cerebral ischemia (TGI). That this discovery depended upon development of embolic animal model reiterates that proper stroke modeling is the key to develop new treatments. In contrast to TGI, despite extensive research, prevention or treatment of brain injury following aneurysmal subarachnoid hemorrhage (aSAH) has not been achieved. A lack of adequate aSAH disease model may have contributed to this failure. TGI is an important component of aSAH and shares mechanism of injury with it. We hypothesized that modifying aSAH model using experience acquired from TGI modeling may facilitate development of treatment for aSAH and its complications. This review focuses on similarities and dissimilarities between TGI and aSAH, discusses the existing TGI and aSAH animal models, and presents a modified aSAH model which effectively mimics the disease and has a potential of becoming a better resource for studying the brain injury mechanisms and developing a treatment.

The role of magnesium in the management of cerebral vasospasm

Subarachnoid hemorrhage (SAH) is characterized by bleeding into the subarachnoid space, often caused by ruptured aneurysm. Aneurysmal rupture occurs in 700,000 individuals per year worldwide, with 40,000 cases taking place in the United States. Beyond the high mortality associated with SAH alone, morbidity and mortality are further increased with the occurrence of cerebral vasospasm, a pathologic constriction of blood vessels that can lead to delayed ischemic neurologic deficits (DIND). Treatment of cerebral vasospasm is a source of contention. One extensively studied therapy is Magnesium (Mg) as both a competitive antagonist of calcium at the N-methyl D-aspartate (NMDA) receptor, and a noncompetitive antagonist of both IP3 and voltage-gated calcium channels, leading to smooth muscle relaxation. In our literature review, several animal and human studies are summarized in addition to two Phase III trials assessing the use of intravenous Mg in the treatment of SAH (IMASH and MASH-2). Though many studies have shown promise for the use of Mg in SAH, there has been inconsistency in study design and outcomes. Furthermore, the results of the recently completed clinical trials have shown no significant benefit from using intravenous Mg as adjuvant therapy in the treatment of cerebral vasospasm.