Proposed Definition of Experimental Secondary Ischemia for Mouse Subarachnoid Hemorrhage

Secondary Ischemia Assessment in Murine and Rat Preclinical Subarachnoid Hemorrhage Models: A Systematic Review

BACKGROUND

Delayed cerebral ischemia represents a significant contributor to death and disability following aneurysmal subarachnoid hemorrhage. Although preclinical models have shown promising results, clinical trials have consistently failed to replicate the success of therapeutic strategies. The lack of standardized experimental setups and outcome assessments, particularly regarding secondary vasospastic/ischemic events, may be partly responsible for the translational failure. The study aims to delineate the procedural characteristics and assessment modalities of secondary vasospastic and ischemic events, serving as surrogates for clinically relevant delayed cerebral ischemia, in recent rat and murine subarachnoid hemorrhage models.

METHODS AND RESULTS

We conducted a systematic review of rat and murine in vivo subarachnoid hemorrhage studies (published: 2016-2020) using delayed cerebral ischemia/vasospasm as outcome parameters. Our analysis included 102 eligible studies. In murine studies (n=30), the endovascular perforation model was predominantly used, while rat studies primarily employed intracisternal blood injection to mimic subarachnoid hemorrhage. Particularly, the injection models exhibited considerable variation in injection volume, rate, and cerebrospinal fluid withdrawal. Peri-interventional monitoring was generally inadequately reported across all models, with body temperature and blood pressure being the most frequently documented parameters (62% and 34%, respectively). Vasospastic events were mainly assessed through microscopy of large cerebral arteries. In 90% of the rat and 86% of the murine studies, only male animals were used.

CONCLUSIONS

Our study underscores the substantial heterogeneity in procedural characteristics and outcome assessments of experimental subarachnoid hemorrhage research. To address these challenges, drafting guidelines for standardization and ensuring rigorous control of methodological and experimental quality by funders and journals are essential.

REGISTRATION

URL: https://www.crd.york.ac.uk/prospero/; Unique identifier: CRD42022337279.

ASK1 inhibitor NQDI‑1 decreases oxidative stress and neuroapoptosis via the ASK1/p38 and JNK signaling pathway in early brain injury after subarachnoid hemorrhage in rats

Oxidative stress and neuroapoptosis are key pathological processes after subarachnoid hemorrhage (SAH). The present study evaluated the anti‑oxidation and anti‑apoptotic neuroprotective effects of the apoptosis signal‑regulating kinase 1 (ASK1) inhibitor ethyl‑2,7‑dioxo‑2,7‑dihydro‑3H‑naphtho(1,2,3‑de)quinoline‑1‑carboxylate (NQDI‑1) in early brain injury (EBI) following SAH in a rat model. A total of 191 rats were used and the SAH model was induced using monofilament perforation. Western blotting was subsequently used to detect the endogenous expression levels of proteins. Immunofluorescence was then used to confirm the nerve cellular localization of ASK1. Short‑term neurological function was assessed using the modified Garcia scores and the beam balance test 24 h after SAH, whereas long‑term neurological function was assessed using the rotarod test and the Morris water maze test. Apoptosis of neurons was assessed by TUNEL staining and oxidative stress was assessed by dihydroethidium staining 24 h after SAH. The protein expression levels of phosphorylated (p‑)ASK1 and ASK1 rose following SAH. NQDI‑1 was intracerebroventricularly injected 1 h after SAH and demonstrated significant improvements in both short and long‑term neurological function and significantly reduced oxidative stress and neuronal apoptosis. Injection of NQDI‑1 caused a significant decrease in protein expression levels of p‑ASK1, p‑p38, p‑JNK, 4 hydroxynonenal, and Bax and significantly increased the protein expression levels of heme oxygenase 1 and Bcl‑2. The use of the p38 inhibitor BMS‑582949 or the JNK inhibitor SP600125 led to significant decreases in the protein expression levels of p‑p38 or p‑JNK, respectively, and a significant reduction in oxidative stress and neuronal apoptosis; however, these inhibitors did not demonstrate an effect on p‑ASK1 or ASK1 protein expression levels. In conclusion, treatment with NQDI‑1 improved neurological function and decreased oxidative stress and neuronal apoptosis in EBI following SAH in rats, possibly via inhibition of ASK1 phosphorylation and the ASK1/p38 and JNK signaling pathway. NQDI‑1 may be considered a potential agent for the treatment of patients with SAH.

The impairment of intramural periarterial drainage in brain after subarachnoid hemorrhage

Interstitial fluid (ISF) from brain drains along the basement membranes of capillaries and arteries as Intramural Periarterial Drainage (IPAD); failure of IPAD results in cerebral amyloid angiopathy (CAA). In this study, we test the hypothesis that IPAD fails after subarachnoid haemorrhage (SAH). The rat SAH model was established using endovascular perforation method. Fluorescence dyes with various molecular weights were injected into cisterna magna of rats, and the pattern of IPAD after SAH was detected using immunofluorescence staining, two-photon fluorescent microscope, transmission electron microscope and magnetic resonance imaging tracking techniques. Our results showed that fluorescence dyes entered the brain along a periarterial compartment and were cleared from brain along the basement membranes of the capillaries, with different patterns based on individual molecular weights. After SAH, there was significant impairment in the IPAD system: marked expansion of perivascular spaces, and ISF clearance rate was significantly decreased, associated with the apoptosis of endothelial cells, activation of astrocytes, over-expression of matrix metalloproteinase 9 and loss of collagen type IV. In conclusion, experimental SAH leads to a failure of IPAD, clinically significant for long term complications such as CAA, following SAH.

Hippocampal Transcriptome Changes After Subarachnoid Hemorrhage in Mice

After subarachnoid hemorrhage (SAH), up to 95% of surviving patients suffer from post-SAH syndrome, which includes cognitive deficits with impaired memory, executive functions, and emotional disturbances. Although these long-term cognitive deficits are thought to result from damage to temporomesial-hippocampal areas, the underlying mechanisms remain unknown. To fill this gap in knowledge, we performed a systematic RNA sequencing screen of the hippocampus in a mouse model of SAH. SAH was induced by perforation of the circle of Willis in mice. Four days later, hippocampal RNA was obtained from SAH and control (sham perforation) mice. Next-generation RNA sequencing was used to determine differentially expressed genes in the whole bilateral hippocampi remote from the SAH bleeding site. Functional analyses and clustering tools were used to define molecular pathways. Differential gene expression analysis detected 642 upregulated and 398 downregulated genes (false discovery rate <0.10) in SAH compared to Control group. Functional analyses using IPA suite, Gene Ontology terms, REACTOME pathways, and MsigDB Hallmark gene set collections revealed suppression of oligodendrocytes/myelin related genes, and overexpression of genes related to complement system along with genes associated with innate and adaptive immunity, and extracellular matrix reorganization. Interferon regulatory factors, TGF-β1, and BMP were identified as major orchestrating elements in the hippocampal tissue response. The MEME-Suite identified binding motifs of Krüppel-like factors, zinc finger transcription factors, and interferon regulatory factors as overrepresented DNA promoter motifs. This study provides the first systematic gene and pathway database of the hippocampal response after SAH. Our findings suggest that damage of the entorhinal cortex by subarachnoid blood may remotely trigger specific hippocampal responses, which include suppression of oligodendrocyte function. Identification of these novel pathways may allow for development of new therapeutic approaches for post-SAH cognitive deficits.