Multiple complications are involved after aSAH resulting in deterioration of neurological function and poor prognosis of the patient(45). Additionally, aSAH therapy has limitations that reduce the benefit to patients. In clinical practice, nimodipine and maintenance of euvolemia are fundamental treatments of CV and DCI after aSAH(29). Numerous studies have been conducted on the treatment of CV and DCI, including calcium channel blockers, magnesium, statins, and angioplasty(46). However, only two basic therapies mentioned above were found to improve outcomes. As a result, some researchers have begun to focus on EBI, the pathological mechanism within 72 hours after aSAH. To the data, there is no specific treatment for EBI. In the current situation, even early intervention cannot entirely prevent brain damage following aSAH. Mechanistically, aSAH occurrence risk assessment for patients is the premise of Preventive intervention to avoid aSAH occurrence. Risk assessment of aSAH occurrence has potential clinical application. Previously, Yan et al. have identified seven genes as possible biomarkers of aSAH. In view of this, our study developed and validated a new immune-related model for predicting the risk of intracranial aneurysm rupture leading to SAH.
Through WGCNA and differential expression genes analysis, we identified 3294 and 37 genes, respectively, and identified 22 collective genes related to aSAH occurrence. We suspect that these 22 genes are inextricably related to aSAH. The mechanisms by which several of these genes are involved in disease have been elucidated. Among the up-regulated genes, ARG1 has been shown to be increased in microglia and macrophages in the early stages of CNS (central nervous system) injury(47, 48). S100A12 is constitutively expressed in neutrophils and is implicated in the pathological remodeling of arterial smooth muscles(49, 50). CCR7 is specifically expressed in macrophages of the M1 type, and the number of macrophages M1 expressing CCR7 increased following SAH(51–53). FER1A encodes the alpha subunit of the immunoglobulin E receptor(54). The deletion of FCER1A protects mice from developing abdominal aortic aneurysms(55). IL1R2, IL18RAP, and IL18R have also been identified as key genes in the aSAH regulatory network(56). ARG1, TPST1, S100A12, and PGLYRP1 were identified as key genes for aSAH(57, 58). Of all down-regulated genes, CCR7 and CD27 were also identified as pivotal genes for aSAH(57, 59). Therefore, we suggested that these 22 genes may be associated with immunity and inflammation and involved in the rupture of intracranial aneurysms and thus in the formation of SAH through potential mechanisms.
To more fully explore the possible involvement of DEGs in disease pathways, we performed a DO analysis of 37 DEGs. Next, we performed GO/KEGG enrichment analysis of the 22 key genes intersected, with the aim of exploring their possible involvement in the biological functions and potential mechanisms of aSAH. The results showed that the enriched pathways were mostly involved in immune response and cytokines. Roles of immune and inflammation in aSAH have been widely studied(10, 60). Macrophages, lymphocytes, neutrophils, and various inflammatory factors are involved in the initiation of aSAH. Inflammatory cascades after aSAH begin with the release of products from erythrocyte lysis, such as heme and hemin, and cause brain injury subsequently(61, 62). Aiming to clarify the potential regulatory mechanism of 22 genes in aSAH, we then used PPI network analysis to identify interacting genes of 22 genes and constructed a triple regulatory network consisting of mRNA, transcription factors, and miRNA. The results show that BCL11B interacts with most miRNAs. BCL11B contributes significantly to adaptive immune function. BCL11B regulates the differentiation and function of NK cells and CD8 + T cells(63–65). Moreover, a study found a significant increase in cerebral microbleeds in mice lacking BCL11B in vascular smooth muscle compared with mice with BCL11B(66). Based on these findings, the initiation of aSAH driven by inflammation may be mediated by a triple regulatory network. This may be the future direction of aSAH mechanism research.
Based on the above analyses, we conducted a correlation study on immune cells and function. Immune cell abundance analysis revealed that neutrophils and monocytes accounted for the largest proportion of the samples. The ssGSEA algorithm also indicates that neutrophils have higher scores in the aSAH group than immune cells. We hypothesize that monocytes and neutrophils are the major inflammatory components in the neurological deterioration after aSAH. In the acute phase of aSAH (0–24 h Post Hemorrhage), there is a dynamic infiltration of neutrophils into the CNS(60). In addition, neutrophils may have increased locally prior to the rupture of IA and may have contributed to the rupture by mediating the MMP9 production of cathepsin(67). Xu et al. found that blood-derived monocytes did not enter the CNS until at least 48 hours after SAH, before which the activated microglia take effect(68). Interestingly, lipid-accumulating foam cells were associated with IA rupture(69). This suggests a potential role for macrophages in aSAH initiation and the need to distinguish between central and peripheral sources of macrophages that form foam cells. Additionally, immune correlation analysis reveals that neutrophils are negatively correlated with most immune cells. There has been considerable interest in the predictive role of neutrophil count and neutrophil-to-lymphocyte ratio in aSAH occurrence(70, 71).