Large differences in collateral blood vessel abundance among individuals arise from multiple genetic variants

Collateral Circulation and Rabep2 Polymorphisms in Large Artery Occlusion: Impacts on Short- and Long-Term Prognosis

BACKGROUND

Intracranial anterior circulation large artery occlusion (AC-LAO) is a predominant cause of ischemic stroke. Although collateral circulation plays a critical role in stroke outcomes, the genetic and environmental factors affecting collateral development are not fully understood. This study aimed to elucidate the associations between Rabep2 gene polymorphisms, collateral circulation, and both short- and long-term prognoses in patients with anterior circulation large artery occlusion.

METHODS AND RESULTS

We recruited 449 patients with anterior circulation large artery occlusion with cerebral infarction. Collateral circulation was assessed using single-phase computed tomography angiography, and stroke outcomes were evaluated at 1 month and 1 year using the modified Rankin Scale. A subset of 180 patients underwent genetic analysis for Rabep2 polymorphisms. Multivariable logistic regression was employed to identify predictors of short-term and long-term outcomes. Enhanced collateral circulation (P<0.001), lower high-density lipoprotein levels (P=0.019), and the absence of complications (P<0.001) were significantly correlated with favorable short-term outcomes. In the long term, age (P=0.039) and diabetes (P=0.006) were independent predictors of poor prognosis, whereas complications demonstrated a protective effect (P=0.016). The rs11645302 polymorphism of Rabep2 was linked to poorer collateral circulation among patients with the CC genotype (odds ratio [OR], 0.498 [95% CI, 0.270-0.918], P=0.025).

CONCLUSIONS

Collateral circulation, high-density lipoprotein levels, Rabep2 gene polymorphisms, age, and diabetes are significant predictors of outcomes in patients with anterior circulation large artery occlusion. These findings underscore the potential to integrate genetic and vascular factors into personalized risk stratification and therapeutic strategies for ischemic stroke.

REGISTRATION

URL: https://www.ClinicalTrials.gov; Unique Identifier: NCT04091412.

Collateral blood vessels in stroke and ischemic disease: Formation, physiology, rarefaction, remodeling

Collateral blood vessels are unique, naturally occurring endogenous bypass vessels that provide alternative pathways for oxygen delivery in obstructive arterial conditions and diseases. Surprisingly however, the capacity of the collateral circulation to provide protection varies greatly among individuals, resulting in a significant fraction having poor collateral circulation in their tissues. We recently reviewed evidence that the presence of naturally-occurring polymorphisms in genes that determine the number and diameter of collaterals that form during development (ie, genetic background), is a major contributor to this variation. The purpose of this review is to summarize current understanding of the other determinants of collateral blood flow, drawing on both animal and human studies. These include the level of smooth muscle tone in collaterals, hemodynamic forces, how collaterals form during development (collaterogenesis), de novo formation of additional new collaterals during adulthood, loss of collaterals with aging and cardiovascular risk factor presence (rarefaction), and collateral remodeling (structural lumen enlargement). We also review emerging evidence that collaterals not only provide protection in ischemic conditions but may also serve a physiological function in healthy individuals. Primary focus is on studies conducted in brain, however relevant findings in other tissues are also reviewed, as are questions for future investigation.

Genetic determinants of insufficiency of the collateral circulation

It has been estimated that approximately two million neurons, sixteen billion synapses and twelve kilometers of axons are lost each minute following anterior large-vessel stroke. The level of collateral blood flow has become recognized as a primary determinant of the pace of this loss and an important factor in clinical decision-making. Many of the topics in this review cover recent developments that have not been reviewed elsewhere. These include that: the number and diameter of collaterals and collateral blood flow vary greatly in the brain and other tissues of healthy individuals; a large percentage of individuals are deficient in collaterals; the underlying mechanism arises primarily from naturally occurring polymorphisms in genes/genetic loci within the pathway that drives collateral formation during development; evidence indicates collateral abundance does not exhibit sexual dimorphism; and that collaterals-besides their function as endogenous bypass vessels-may have a physiological role in optimizing oxygen delivery. Animal and human studies in brain and other tissues, where available, are reviewed. Details of many of the studies are provided so that the strength of the findings and conclusions can be assessed without consulting the original literature. Key questions that remain unanswered and strategies to address them are also discussed.

Evolucollateral dynamics in stroke: Evolutionary pathophysiology, remodelling and emerging therapeutic strategies

Leptomeningeal collaterals (LMCs) are crucial in mitigating the impact of acute ischemic stroke (AIS) by providing alternate blood flow routes when primary arteries are obstructed. This article explores the evolutionary pathophysiology of LMCs, highlighting their critical function in stroke and the genetic and molecular mechanisms governing their development and remodelling. We address the translational challenges of applying animal model findings to human clinical scenarios, emphasizing the need for further research to validate emerging therapies-such as pharmacological agents, gene therapy and mechanical interventions-in clinical settings, aimed at enhancing collateral perfusion. Computational modelling emerges as a promising method for integrating experimental data, which requires precise parameterization and empirical validation. We introduce the 'Evolucollateral Dynamics' hypothesis, proposing a novel framework that incorporates evolutionary biology principles into therapeutic strategies, offering new perspectives on enhancing collateral circulation. This hypothesis emphasizes the role of genetic predispositions and environmental influences on collateral circulation, which may impact therapeutic strategies and optimize treatment outcomes. Future research must incorporate human clinical data to create robust treatment protocols, thereby maximizing the therapeutic potential of LMCs and improving outcomes for stroke patients.

The Updated Mouse Universal Genotyping Array Bioinformatic Pipeline Improves Genetic QC in Laboratory Mice

The MiniMUGA genotyping array is a popular tool for genetic QC of laboratory mice and genotyping of samples from most types of experimental crosses involving laboratory strains, particularly for reduced complexity crosses. The content of the production version of the MiniMUGA array is fixed; however, there is the opportunity to improve array's performance and the associated report's usefulness by leveraging thousands of samples genotyped since the initial description of MiniMUGA in 2020. Here we report our efforts to update and improve marker annotation, increase the number and the reliability of the consensus genotypes for inbred strains and increase the number of constructs that can reliably be detected with MiniMUGA. In addition, we have implemented key changes in the informatics pipeline to identify and quantify the contribution of specific genetic backgrounds to the makeup of a given sample, remove arbitrary thresholds, include the Y Chromosome and mitochondrial genome in the ideogram, and improve robust detection of the presence of commercially available substrains based on diagnostic alleles. Finally, we have made changes to the layout of the report, to simplify the interpretation and completeness of the analysis and added a table summarizing the ideogram. We believe that these changes will be of general interest to the mouse research community and will be instrumental in our goal of improving the rigor and reproducibility of mouse-based biomedical research.