Presence of vasa vasorum in human intracranial aneurysms

MR Imaging of the Cerebral Aneurysmal Wall for Assessment of Rupture Risk

The evaluation of unruptured intracranial aneurysms requires a comprehensive and multifaceted approach. The comprehensive analysis of aneurysm wall enhancement through high-resolution MRI, in tandem with advanced processing techniques like finite element analysis, quantitative susceptibility mapping, and computational fluid dynamics, has begun to unveil insights into the intricate biology of aneurysms. This enhanced understanding of the etiology, progression, and eventual rupture of aneurysms holds the potential to be used as a tool to triage patients to intervention versus observation. Emerging tools such as radiomics and machine learning are poised to contribute significantly to this evolving landscape of diagnostic refinement.

Decoding the Cell Atlas and Inflammatory Features of Human Intracranial Aneurysm Wall by Single-Cell RNA Sequencing

BACKGROUND

Intracranial aneurysm (IA) is common and occasionally results in life-threatening hemorrhagic strokes. However, the cell architecture and inflammation in the IA dome remain less understood.

METHODS AND RESULTS

Single-cell RNA sequencing was performed on ruptured and unruptured human IA domes for delineating the cell atlas, gene expression perturbations, and inflammation features. Two external bulk mRNA sequencing-based data sets and serological results of 126 patients were collected for validation. As a result, a total of 21 332 qualified cells were captured. Vascular cells, including endothelial cells, smooth muscle cells, fibroblasts, and pericytes, were assigned in extremely sparse numbers (4.84%), and were confirmed by immunofluorescence staining. Pericytes, characterized by ABCC9 and HIGD1B, were identified in the IA dome for the first time. Abundant immune cells were identified, with the proportion of monocytes/macrophages and neutrophils being remarkably higher in ruptured IA. The lymphocyte compartment was also thoroughly categorized. By leveraging external data sets and machine learning algorithms, macrophages were robustly associated with IA rupture, irrespective of their polarization status. The single nucleotide polymorphism rs2280543, which is identified in East Asian populations, was associated with macrophage metabolic reprogramming through regulating TALDO1 expression.

CONCLUSIONS

This study provides insights into the cellular architecture and inflammatory features in the IA dome and may enlighten novel therapeutics for unruptured IA.

Isolation of vasa vasorum endothelial cells from pulmonary artery adventitia: Implementation to vascular biology research

Isolated endothelial cells are valuable in vitro model for vascular research. At present, investigation of disease-relevant changes in vascular endothelium at the molecular level requires established endothelial cell cultures, preserving vascular bed-specific phenotypic characteristics. Vasa vasorum (VV) form a microvascular network around large blood vessels, in both the pulmonary and systemic circulations, that are critically important for maintaining the integrity and oxygen supply of the vascular wall. However, despite the pathophysiological significance of the VV, methods for the isolation and culture of vasa vasorum endothelial cells (VVEC) have not yet been reported. In our prior studies, we demonstrated the presence of hypoxia-induced angiogenic expansion of the VV in the pulmonary artery (PA) of neonatal calves; an observation which has been followed by a series of in vitro studies on isolated PA VVEC. Here we present a detailed protocol for reproducible isolation, purification, and culture of PA VVEC. We show these cells to express generic endothelial markers, (vWF, eNOS, VEGFR2, Tie1, and CD31), as well as progenitor markers (CD34 and CD133), bind lectin Lycopersicon Esculentum, and incorporate acetylated low-density lipoproteins labeled with acetylated LDL (DiI-Ac-LDL). qPCR analysis additionally revealed the expression of CD105, VCAM-1, ICAM-1, MCAM, and NCAM. Ultrastructural electron microscopy and immunofluorescence staining demonstrated that VVEC are morphologically characterized by a developed actin and microtubular cytoskeleton, mitochondrial network, abundant intracellular vacuolar/secretory system, and cell-surface filopodia. VVEC exhibit exponential growth in culture and can be mitogenically activated by multiple growth factors. Thus, our protocol provides the opportunity for VVEC isolation from the PA, and potentially from other large vessels, enabling advances in VV research.

On vasa vasorum: A history of advances in understanding the vessels of vessels

The vasa vasorum are a vital microvascular network supporting the outer wall of larger blood vessels. Although these dynamic microvessels have been studied for centuries, the importance and impact of their functions in vascular health and disease are not yet fully realized. There is now rich knowledge regarding what local progenitor cell populations comprise and cohabitate with the vasa vasorum and how they might contribute to physiological and pathological changes in the network or its expansion via angiogenesis or vasculogenesis. Evidence of whether vasa vasorum remodeling incites or governs disease progression or is a consequence of cardiovascular pathologies remains limited. Recent advances in vasa vasorum imaging for understanding cardiovascular disease severity and pathophysiology open the door for theranostic opportunities. Approaches that strive to control angiogenesis and vasculogenesis potentiate mitigation of vasa vasorum-mediated contributions to cardiovascular diseases and emerging diseases involving the microcirculation.

Semiautomated 3D mapping of aneurysmal wall enhancement with 7T-MRI

Aneurysm wall enhancement (AWE) after the administration of contrast gadolinium is a potential biomarker of unstable intracranial aneurysms. While most studies determine AWE subjectively, this study comprehensively quantified AWE in 3D imaging using a semi-automated method. Thirty patients with 33 unruptured intracranial aneurysms prospectively underwent high-resolution imaging with 7T-MRI. The signal intensity (SI) of the aneurysm wall was mapped and normalized to the pituitary stalk (PS) and corpus callosum (CC). The CC proved to be a more reliable normalizing structure in detecting contrast enhancement (p < 0.0001). 3D-heatmaps and histogram analysis of AWE were used to generate the following metrics: specific aneurysm wall enhancement (SAWE), general aneurysm wall enhancement (GAWE) and focal aneurysm wall enhancement (FAWE). GAWE was more accurate in detecting known morphological determinants of aneurysm instability such as size ≥ 7 mm (p = 0.049), size ratio (p = 0.01) and aspect ratio (p = 0.002). SAWE and FAWE were aneurysm specific metrics used to characterize enhancement patterns within the aneurysm wall and the distribution of enhancement along the aneurysm. Blebs were easily identified on 3D-heatmaps and were more enhancing than aneurysm sacs (p = 0.0017). 3D-AWE mapping may be a powerful objective tool in characterizing different biological processes of the aneurysm wall.

The Silk Vista Baby - The UK experience

BACKGROUND

The Silk Vista Baby (SVB) flow diverter (FDS) is the only FDS deliverable via a 0.017 inch microcatheter and is specifically designed for the distal vasculature. We sought to evaluate the safety and efficacy of the SVB.

MATERIALS AND METHODS

We performed a retrospective review to identify SVB cases at 4 tertiary neurosurgical centres within the U.K. Clinical, procedural, angiographic and follow-up data were collected.

RESULTS

We identified 60 patients (35 female, 58%) of average age 54 ± 10.5 (range 30-72) with 61 aneurysms, 50 (81.9%) located in the anterior circulation. The majority of the aneurysms treated were unruptured (46, 75.4%) and saccular (46, 75.4%). Dome size was 6.2 ± 6.2 mm (range 1-36mm) and parent vessel diameter was 2.3 ± 0.4 mm (range 1.2-3.3 mm).An average number of 1.07 devices were implanted. Coils or other devices were implanted in 14 aneurysms (23.3%). At last angiographic follow-up (n = 55), 7.5 ± 4.2 months post-procedure, 32 aneurysms (57.1%) were graded as RRC I, 7 (12.5%) RRC II, and 17 RRC III (30.4%).Clinical complications, excluding death, were seen in 4 patients (6.8%) including 1 delayed aneurysm rupture and 3 symptomatic ischaemic events. Only one patient had permanent morbidity (mRS 1). 3 patients died during follow-up (5.1%); 2 deaths were related to the aneurysms (3.4%) - one ruptured dissecting MCA aneurysm, and one giant partially thrombosed posterior circulation aneurysm. 93% of patients were mRS ≤ 2 at last follow-up.

CONCLUSION

The SVB has high rates of technical success and an acceptable safety profile. Distal aneurysms may occlude slower due to relative oversizing of the devices.

Comparison of clinical and histopathological characteristics of short-term progressive and non-progressive blood blister-like aneurysms

BACKGROUND

Many blood blister aneurysms (BBAs) have been documented with a rapid progression history in repeated angiography. The underlying mechanism and clinical significance remained elusive. This current study aims to clarify the clinical and histopathological differences between short-term progressive BBA and non-progressive BBAs.

METHODS AND MATERIALS

Eighty-one patients with BBAs were consecutively included for this single-center retrospective analysis. Clinical and radiological data on these patients were retrieved from 2017 to 2019. BBAs were defined as either progressive or non-progressive based on observed growth based on repeated imaging. Histopathological examinations of a saccular aneurysm, a progressive BBA, and a non-progressive BBA were conducted using representative aneurysm samples.

RESULTS

Among all enrolled patients, 26 of the them were identified with progressive BBAs, while the other 55 with non-progressive BBAs. Progressive BBAs were diagnosed significantly earlier in angiography (3.36 ± 0.61 vs. 6.53 ± 1.31 days, p < 0.05) and showed a higher presence rate of daughter sacs (61.5 vs. 38.2%, p < 0.05). Three different progression patterns were identified. BBAs that developed daughter sac enlargement are diagnosed significantly later than BBAs exhibiting other progression patterns. Patients with progressive and non-progressive BBAs exhibited similar overall clinical outcomes and incidence for complications. For patients with non-progressive BBAs, microsurgery appears to be inferior to endovascular treatment, while for patients with progressive BBAs, the short-term outcomes between microsurgery and endovascular treatment were identical. Histopathological analysis revealed that both subtypes shared a similar pseudoaneurysms structure, but non-progressive BBAs had more histologically destructed aneurysm wall with less remnant fibrillar collagen in adventitia.

CONCLUSIONS

Progressive and non-progressive BBAs may not be distinct pathological lesions but represent different stages during the BBA development. Early intervention, regardless of treatment methods, is recommended for salvageable patients with progressive BBAs, but microsurgery should be performed with caution for non-progressive BBAs due to increased surgical risk.