Discussion
In the present study, a few (0.5%) Chinese patients with AIS or TIA carried the RNF213 p.R4810K variant, rarer than in Japanese and Korean populations.1 8 19 The p.R4810K variant was related to LAA, anterior circulation stenosis and ECAS in Chinese patients. Given the low-carrying rate and only 1-year follow-up information, caution should be taken to interpret our findings of no statistically significant association between the p.R4810K variant and stroke prognosis in Chinese patients.
A previous study reported that the prevalence of the RNF213 p.R4810K variant in the normal Chinese population is 0.5%, which is similar to the prevalence of the p.R4810K variant in Chinese stroke patients (0.5%), but slightly lower than the prevalence in LAA (0.8%) and in ICAS (0.7%).4 The wide discrepancy in the prevalence between our study and prior investigations may be attributed to genetic heterogeneity.8 9 Numerous epidemiological studies have demonstrated notable ethnic differences in the prevalence of the p.R4810K variant among Japanese, Korean and Chinese patients with MMD.20 Although sizeable clinical evidence confirmed a strong association of the RNF213 p.R4810K variant with ischaemic stroke, especially with LAA, in the Japanese and Korean populations, recent literature has also found other RNF213 variants closely related to the high prevalence of ICAS in Chinese patients, such as p.A5021V (rs138130613, c.15062C>T).8 19 21 It suggests that ICAS and MMD may have a similar frequency spectrum of the RNF213 variants in different ethnicities, that is, the variant sites in the RNF213 gene among the Japanese and Korean populations are concentrated in the p.R4810K, but among the Chinese population are scattered, and among other populations are few.22 23
Previous studies have demonstrated that patients with the RNF213 p.R4810K variant exhibit earlier onset age and had a higher rate of women.24 The variant carriers were younger than non-carriers in our participants. Nevertheless, there was no sex difference between the two groups. Recent findings from high-resolution MRI (HR-MRI) have provided evidence that the pathological mechanism underlying ICAS in patients with the RNF213 p.R4810K variant was not only non-atherosclerotic but also atherosclerotic.25 Given no difference in atherosclerotic risk factors between patients with and without variants in our study, the contradiction may be potentially elucidated by a higher prevalence of atherosclerosis in Chinese patients with the RNF213 p.R4810K variant, which may be linked to a greater proportion of male patients.26
Our study first demonstrated that the RNF213 p.R4810K variant was associated with an elevated risk of LAA among Chinese patients with ischaemic cerebrovascular disease. Besides, the p.R4810K variant was related to anterior circulation stenosis in Chinese patients, which bears similarity to the characteristics of vascular stenosis in Japanese patients.1 However, the trend towards a higher proportion of ICAS in Chinese patients with the p.R4810K variant did not reach statistical significance. Previous meta-analysis and systematic review explored the critical roles of the RNF213 p.R4810K in Chinese patients with ICAS.27 An early study demonstrated that the carriers in Chinese patients with ICAS were comparatively less symptomatic and more likely to possess collateral vessels.28 Considering our study mainly included hospitalised patients, there exists a possibility that individuals with mild symptoms carrying the p.R4810K variant related to ICAS may have been overlooked. It is necessary to verify the correlation between p.R4810K polymorphism and ICAS in the asymptomatic and symptomatic Chinese ICAS population.
The novel findings in the present study were the high rate of peripheral vascular disease history in carriers and a strong association of the p.R4810K variant with ECAS. A recent study verified that the p.R4810K variant carriers exhibit smaller outer diameters of the cervical arteries compared with non-carriers with ischaemic stroke.29 In addition, some previous cases have demonstrated that the RNF213 p.R4810K variant impacts arteries throughout the body, such as the abdominal aorta, renal artery and pulmonary artery.30–32 The evidence suggests that the variant of RNF213 might play an essential role in the multiple circulatory systems. However, the clinical phenotypes displayed may vary owing to interindividual variations. In-depth and methodical research on the spectrum of RNF213-related vasculopathy holds the potential to shed novel insights into the aetiology and progression of vascular disease.2 8 30
The RNF213 p.R4810K variant showed a tendency to increase the risk of stroke recurrence in Chinese patients while reducing the risk of poor functional outcome after 1 year. However, these observations did not attain statistical significance. Although we did not distinguish between atherosclerosis and non-atherosclerosis using HR-MRI or pathological examination, given the disparity in sample size between the two groups, we could not directly conclude that conventional secondary prevention is helpful for all variant carriers. A recent case report discovered that patients with atherosclerotic moyamoya syndrome exhibit the development of new moyamoya vessels despite receiving antiplatelet and statin therapy.33 Besides, many studies have reported that the RNF213 p.R4810K variant carriers with ICAS or intracranial artery dissection gradually developed into MMD.34 35 Screening for the RNF213 polymorphism, completing HR-MRI to evaluate stenosis and receiving long-term imaging follow-up is of great significance for enhancing individualised treatment and improving stroke prognosis.
The pathological mechanism underlying the effect of the RNF213 variant on abnormal angiogenesis remains unknown. Preclinical research has found that the loss of RNF213 function did not trigger the spontaneous development of smog-like vessels but caused irregular vascular wall formation as a critical regulator of cerebral endothelium integrity.22 36 According to research conducted on mice deficient in RNF213, several metabolites have been found to be associated with the occurrence of abnormal angiogenesis, such as matrix metalloproteinase—9 and caveolin-1.37 38 Besides, some basic studies have demonstrated that biological agents, such as microRNAs and interferon—β, are capable of regulating the expression of RNF213.39 40 The present evidence suggests that RNF213 is implicated in the multifaceted pathogenesis of anomalous vascular structures. Further investigation into the upstream and downstream pathways of RNF213 is warranted to enhance comprehension of the underlying mechanism and identify new targets for the prevention and treatment of RNF213-related vasculopathy.
This study has several limitations. First, due to the low prevalence of the RNF213 p.R4810K variant, there may be a deviation in the statistical analysis between the two groups. However, the differences in sample size between the two subgroups may be closer to the real-world’s situation in China and provide more contributing information for clinical applications. Second, because some patients have contraindications to MRA or CTA, the imaging methods for evaluating arterial conditions are not uniform, which may affect classification accuracy. Third, a lack of HR-MRI or pathological analysis might dilute the effect of the variant on non-atherosclerotic blood vessels. Fourth, the present study is limited by its enrolment of only Chinese patients, which raises concerns regarding the generalisability of the findings to other populations. Fifth, this study solely discussed the relationship between the RNF213 p.R4810K variant and ischaemic cerebrovascular disease. More comprehensive genetic analysis, such as the whole genome sequencing analysis, is essential to discuss whether patients with large artery stenosis have an association with other variants of the RNF213 or other genes. Sixth, the assessment of the involved vessels remains confined to a cross-sectional result. Further longitudinal studies are necessary to confirm whether the ICAS with variant has progressed to MMD.