Moyamoya disease involves progressive narrowing or occlusion of the terminal internal carotid artery and/or proximal anterior or middle cerebral arteries, together with abnormal basal collateral vessels on vascular imaging. The study included only people without clinically overt ischemic stroke or intracranial hemorrhage before enrollment, making the cohort a model of chronic cerebral hypoperfusion with less interference from major infarction or hemorrhagic injury. The retrospective observational design and complete-case analysis mean that the results cannot establish causation or determine whether either MRI measure predicts subsequent cognitive change. The researchers also noted that asymptomatic moyamoya disease is not necessarily free of structural white-matter injury or subtle cognitive impairment.

Participants had a mean age of 44.22 years, and the cohort included 34 women and 25 men. Mean MoCA and MMSE scores were 22.63 and 26.12, respectively. The mean ALPS index was 1.42, and the mean PVeD index was 0.48. Angiographic involvement was bilateral in 43 patients, or 72.9%, and unilateral in 16, or 27.1%. Maximum hemispheric Suzuki stage ranged from 1 to 4, with a median of 3. Median left and right Suzuki stages were both 2, and a paired Wilcoxon signed-rank test did not show a significant left-right difference in angiographic severity, with P = 0.095. The total white-matter hyperintensity score had a median of 3, an interquartile range of 2–5 and an observed range of 0–9.

MRI was acquired on a 3.0-tesla Siemens MAGNETOM Prisma scanner using a 64-channel head and neck coil. The protocol included three-dimensional T1-weighted imaging, axial T2-weighted imaging, fluid-attenuated inversion recovery, susceptibility-weighted imaging and diffusion tensor imaging. DTI data underwent correction for susceptibility-related distortion, eddy-current effects and participant motion. Tensor maps were then registered to MNI152 standard space for ALPS region-of-interest placement and parameter extraction. Visual quality control excluded images with substantial motion, signal loss, severe distortion, incomplete brain extraction, failed correction or unacceptable registration.

For DTI-ALPS, fixed bilateral regions of interest were placed at the level of the bodies of the lateral ventricles in projection- and association-fiber regions. The left and right indices were calculated as the mean of diffusivity along the x axis in the projection and association regions divided by the mean of y-axis diffusivity in the projection region and z-axis diffusivity in the association region. The mean ALPS index was the arithmetic average of the bilateral values. PVeD was calculated with the automated EstPVeD pipeline in MATLAB R2024a and SPM12. It registers a lateral-ventricle template to diffusion space, constructs an anatomically adaptive periventricular region and uses tissue segmentation to exclude cerebrospinal fluid and non-brain tissue. The transverse tensor ratio was calculated as Dxx divided by the square root of Dxx squared plus Dyy squared plus Dzz squared, with median values extracted from the left and right periventricular regions.

Before adjustment for confounding, mean ALPS was positively correlated with MoCA at Spearman rho = 0.493 and with MMSE at rho = 0.326. The left ALPS index correlated with MoCA at rho = 0.522 and MMSE at rho = 0.372, while right ALPS correlated with MoCA at rho = 0.335 but not MMSE. After adjustment for age and sex, the partial correlation for mean ALPS was 0.494 with MoCA and 0.316 with MMSE. Left ALPS remained associated with both scores, with partial rho values of 0.508 and 0.346, and right ALPS remained associated with MoCA at partial rho = 0.349. Right ALPS was not significantly associated with MMSE after correction, with partial rho = 0.203 and q = 0.2229. These results indicate that the imaging-cognition relationship was stronger and more consistent for ALPS than for PVeD in this sample.

PVeD showed a less consistent pattern in the unadjusted analysis. Left PVeD correlated with MMSE at rho = 0.320, while its association with MoCA was close to the corrected threshold, with q = 0.0526. Mean PVeD had a nominal association with MMSE at rho = 0.257, P = 0.0496, but it did not survive correction, with q = 0.0743. Mean PVeD was not significantly associated with MoCA, with rho = 0.246 and q = 0.0805. Following age and sex adjustment, none of the six PVeD associations met the false-discovery-rate threshold. Mean PVeD had partial rho values of 0.147 with MoCA and 0.182 with MMSE. Left PVeD and MMSE had a partial rho of 0.243, but q = 0.1365, while the other adjusted PVeD correlations were also non-significant after correction.

Multivariable linear regression produced a similar pattern. In models adjusted for age and sex, mean ALPS was associated with MoCA with an unstandardized beta of 11.716, a 95% confidence interval of 4.930 to 18.502, P = 0.0011 and adjusted R-squared of 0.233. Its association with MMSE was also nominally significant, with beta = 5.213, 95% confidence interval 0.619 to 9.807 and P = 0.0269. Mean PVeD was not significantly associated with MoCA, with beta = 34.662, 95% confidence interval −1.697 to 71.022 and P = 0.0613. Its MMSE association was nominal, with beta = 23.944, 95% confidence interval 0.735 to 47.153 and P = 0.0434. The regression P values were exploratory and were not additionally adjusted for multiple testing.

Adding total white-matter hyperintensity burden attenuated the ALPS-MMSE relationship to non-significance, with beta = 3.739, 95% confidence interval −0.897 to 8.375 and P = 0.1117. The ALPS-MoCA association remained statistically significant, with beta = 9.281, 95% confidence interval 2.512 to 16.051, P = 0.0081 and adjusted R-squared of 0.301. Mean PVeD was not associated with either cognitive score after WMH adjustment. In an extended model adding maximum hemispheric Suzuki stage to age, sex and WMH burden, mean ALPS remained associated with MoCA, although the estimate was smaller: beta = 7.790, 95% confidence interval 0.816 to 14.765, P = 0.0293 and adjusted R-squared of 0.317. ALPS-MMSE and both PVeD associations were non-significant in those extended models. The sensitivity analyses therefore suggest that structural white-matter injury and angiographic severity account for part, but not necessarily all, of the imaging-cognition relationships.

Several limitations constrain the findings. The sample was relatively small and cross-sectional, so the associations cannot establish causality, longitudinal predictive value or the direction of any imaging-cognition relationship. APOE genotype and amyloid-beta or tau biomarkers were unavailable, meaning occult Alzheimer’s pathology, mixed vascular-neurodegenerative disease and APOE-related effects could not be excluded. Education level was also unavailable and may have influenced MoCA and MMSE performance. Although WMH burden and maximum hemispheric Suzuki stage were included, potential confounders including ventricular volume, brain atrophy, lacunes, cerebral microbleeds, quantitative cerebral perfusion and cerebrovascular reserve were not quantitatively modeled. MoCA and MMSE are global screening instruments rather than comprehensive neuropsychological tests, so the absence of a PVeD association with global scores does not exclude relationships with executive function, processing speed, attention or memory.

The biological meaning of the two metrics also requires caution. In chronic hypoperfusion, periventricular diffusion may reflect white-matter injury, demyelination, tissue rarefaction, ventricular enlargement, altered tissue water content, ischemia-related changes and potentially interstitial fluid transport. PVeD was introduced as a marker associated with amyloid burden and cognition in the Alzheimer’s disease continuum, but the present study shows that its relationship with global cognition was less consistent in a chronic-ischemic population. ALPS is not a direct measure of glymphatic flow either: it can be influenced by fiber architecture, crossing fibers, region-of-interest placement, scanner parameters and disease-related tissue changes. Agreement between ALPS and tracer-based MRI measures of cerebrospinal fluid distribution and clearance remains limited. The study therefore supports a disease-specific, structurally informed interpretation of diffusion-based markers rather than a claim that one index is a superior measure of true glymphatic function. Prospective studies combining longitudinal cognition, perfusion and vascular-injury measures, Alzheimer’s biomarkers and tracer-based fluid assessments will be needed to clarify what each index reflects and whether either predicts cognitive trajectories.

Subject of Research: Cross-sectional comparison of DTI-ALPS and periventricular diffusivity with cognition in asymptomatic moyamoya disease

Article Title: Disease-context dependence of periventricular diffusivity and DTI-ALPS in asymptomatic moyamoya disease

Article References: Liu, H., Liu, X., Ji, H., Xiao, A., & Liu, Y. (2026). Disease-context dependence of periventricular diffusivity and DTI-ALPS in asymptomatic moyamoya disease. Frontiers in Neurology, 17, 1927018. https://doi.org/10.3389/fneur.2026.1927018

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1927018

Keywords: moyamoya disease, DTI-ALPS, periventricular diffusivity, diffusion MRI, chronic hypoperfusion, brain fluid transport, cognitive impairment, white matter injury, vascular cognitive impairment, glymphatic system, Disease-context, dependence

Now a review published in Molecular Biology Reports by a team of Korean researchers led by Jong-Tae Kim, Dong Hyuk Youn, Jae Jun Lee and Jin Pyeong Jeon of Hallym University College of Medicine maps out how patient-derived induced pluripotent stem cells and organoids are transforming the field. The review traces the evolution of Moyamoya modeling from early studies of circulating endothelial progenitor cells to sophisticated three-dimensional vascular and neurovascular organoids, and argues that these platforms could finally capture the genetic, vascular and neurovascular complexity that conventional models have missed. The work arrives at a moment when the field’s central susceptibility gene, RNF213, is being dissected at molecular resolution, and when organoid technology is mature enough to reproduce vessel-like structures in a dish.

The genetic foundation of the disease was laid in 2011, when genome-wide association studies identified RNF213, which encodes the ring finger protein 213, as the first Moyamoya disease gene. The R4810K variant, a single amino acid substitution in East Asian patients, remains the strongest susceptibility factor, and subsequent genome-wide studies have uncovered additional loci. Yet the genotype-phenotype relationship is far from simple. Not every carrier develops disease, penetrance is incomplete, and European patients often present with Moyamoya angiopathy without the East Asian founder mutation. This complexity has made it clear that RNF213-dependent and RNF213-independent mechanisms both contribute, and that understanding them requires models built on human cells carrying the actual patient genome.

Induced pluripotent stem cells, or iPSCs, offer exactly that opportunity. By reprogramming peripheral blood mononuclear cells or skin fibroblasts from patients back into a pluripotent state, researchers can generate an unlimited supply of genetically matched cells and then differentiate them into any vascular lineage of interest. The first Moyamoya-specific iPSC lines were established in 2016 from patients with ischemic and hemorrhagic forms of the disease, followed in 2021 by a line carrying a confirmed RNF213 mutation. Validation of these lines requires confirming pluripotency markers, normal karyotype, and retention of the disease genotype, and once established, they can be directed toward endothelial cells, vascular smooth muscle cells, and related vascular lineages that constitute the arterial wall.

Two-dimensional iPSC-based models have already yielded concrete mechanistic insights. In 2013, researchers showed that the RNF213 R4810K variant downregulates securin, reducing the angiogenic activity of iPSC-derived vascular endothelial cells from Moyamoya patients, and that the same variant induces genomic instability through mitotic abnormalities. Later work demonstrated that RNF213 regulates endothelial barrier function, that its loss of function promotes pathological angiogenesis through the Hippo pathway, and that RNF213 knockdown combined with inflammation drives angiogenesis and phenotype switching via the JAK2/STAT3 pathway. Studies of iPSC-derived vascular smooth muscle cells revealed abnormal behavior compared with healthy controls, and comparative transcriptomic analysis of endothelial and smooth muscle lineages highlighted disrupted vascular cell interactions. Additional findings point to autophagic impairment, mitochondrial dysfunction, and altered responses to vascular endothelial growth factor and transforming growth factor-beta as contributing factors.

These 2D models, however, have inherent limitations. They flatten the vascular wall into a single layer, remove the mechanical forces of blood flow, and eliminate the cellular heterogeneity and spatial organization that define living vessels. Histopathological studies of Moyamoya arteries show intimal thickening, proliferation and migration of smooth muscle cells, and infiltration of macrophages and T cells, features that a flat culture cannot reproduce. The review therefore highlights the emerging use of three-dimensional vascular organoids, which self-organize into vessel-like networks embedded in an extracellular matrix, and neurovascular organoids, which integrate brain cells with vascular components to model the neurovascular unit, the interface where endothelial cells, pericytes, astrocytes and neurons meet at the blood-brain barrier.

Recent organoid studies are beginning to capture key features of Moyamoya vasculopathy. In 2026, researchers reported that RNF213 deficiency in human iPSC-derived vascular organoids reproduces a central feature of the disease’s vasculopathy, and a separate organoid modeling study combined with single-cell RNA sequencing revealed pathological smooth muscle cell migration, a hallmark of Moyamoya arteriopathy. Vascularized brain organoids, engineered through strategies that co-culture endothelial cells with neural progenitors or embed vascular lineages within brain organoid matrices, now allow researchers to study how Moyamoya-relevant vascular defects interact with brain tissue. These models reproduce cellular heterogeneity, vessel-like organization, and neurovascular unit interactions far more closely than conventional 2D cultures, providing a more integrated platform for investigating the complex vascular pathophysiology of the disease.

The review also points toward future directions that could sharpen these models further. Integration of multi-omics profiling, including single-cell RNA sequencing, proteomics and metabolomics, with patient-derived iPSC and organoid platforms could clarify genotype-phenotype relationships and identify disease-relevant molecular pathways. CRISPR-mediated genome editing offers the ability to introduce or correct RNF213 variants in isogenic cell lines, allowing researchers to isolate the effect of specific mutations against an otherwise identical genetic background. Organ-on-a-chip systems that apply shear stress and pulsatile flow could add the biomechanical dimension that static cultures lack, and adeno-associated viral vectors and lipid nanoparticles could enable therapeutic gene delivery studies within organoid models. Discordant monozygotic twin studies, which have already profiled circulating microRNAs and endothelial microRNA expression using iPSC lines, add another layer of control by isolating genetic from environmental contributions.

With further standardization and validation, iPSC- and organoid-based models could support mechanistic studies, therapeutic screening, and personalized disease modeling, in which a patient’s own cells are used to test drug responses before treatment begins. The review underscores that these technologies are not merely incremental improvements but represent a fundamental shift in how a rare cerebrovascular disorder can be studied, moving from indirect proxies of vascular dysfunction to direct, human, genetically faithful models of the disease itself. For a condition that has resisted mechanistic dissection for more than half a century, the convergence of patient-derived stem cells, organoids, genome editing and multi-omics profiling may finally provide the tools needed to unravel why cerebral arteries narrow, why fragile collaterals form, and how both processes might one day be prevented.

Subject of Research: Moyamoya disease modeling with patient-derived iPSCs and organoids

Article Title: Modeling Moyamoya disease using patient-derived induced pluripotent stem cells and organoids

Article References: Kim, J.-T., Youn, D. H., Jung, H., Lee, J. H., Hong, E. P., Kim, Y., Cho, K.-W., Lee, J. J., & Jeon, J. P. (2026). Modeling Moyamoya disease using patient-derived induced pluripotent stem cells and organoids. Molecular Biology Reports, 53(1), Article 1750. https://doi.org/10.1007/s11033-026-12932-2

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12932-2

Keywords: Moyamoya disease, induced pluripotent stem cells, organoids, RNF213, disease modeling, vascular organoids, brain organoids, endothelial cells, vascular smooth muscle cells, CRISPR genome editing, neurovascular unit, single-cell RNA sequencing

Moyamoya disease is a chronic, progressive occlusion of the terminal internal carotid arteries and their proximal branches, characterised by the development of a fragile network of compensatory collateral vessels at the base of the brain that resembles a puff of smoke on angiographic imaging. When medical therapy alone cannot prevent recurrent ischemic or hemorrhagic events, surgeons turn to revascularization procedures. Indirect bypass, the technique central to the Chen study, involves laying vascularised tissue such as the temporalis muscle directly onto the cortical surface, relying on the patient’s own biological capacity to sprout new arteries from the donor tissue into the ischemic brain over weeks to months. The molecular signals that govern this neoangiogenesis have remained poorly characterised, which is precisely why the transcriptomic profiling approach attracted so much attention.

The Chen team’s central finding was that genes associated with extracellular matrix organisation and collagen deposition were significantly enriched in patients who went on to develop robust collateral circulation after surgery, as graded by the Matsushima angiographic scale. This suggested that the structural scaffold laid down by the transplanted temporal muscle might serve as a permissive microenvironment through which endothelial cells migrate, proliferate, and anastomose with the cortical vasculature. The implication was tantalising: if collagen-rich matrix remodelling is a driver rather than a byproduct of successful collateralisation, then pharmacological modulation of matrix biology could one day enhance surgical outcomes in patients whose native angiogenic response is insufficient.

However, Rani and Baig argue that this conclusion rests on a cohort whose internal heterogeneity was never adequately controlled. Their first and most pointed criticism concerns the pooling of paediatric and adult patients without stratification by clinical disease stage, whether measured by the Suzuki angiographic staging system or by hemodynamic assessment of cerebral perfusion reserve. Children with Moyamoya disease possess a dramatically higher native capacity for neoangiogenesis and collateral development than adults, a biological trait that operates independently of any measurable difference in extracellular matrix gene expression. When these two age groups are analysed together, the resulting transcriptomic signature may simply reflect an age-specific baseline angiogenic response rather than a shared molecular mechanism of surgical success.

The letter elaborates on this confounding problem with technical precision. Endogenously generated differential angiogenic signals are themselves associated with advanced disease stage and severe basal hypoperfusion, meaning that the ischemic drive within the brain tissue of a stage IV patient is fundamentally different from that of a stage II patient. Without correcting multi-variable transcriptomic models for pre-operative Suzuki staging and cerebrovascular reserve capacity, the collagen-rich signature identified by Chen and colleagues could be an artifact of mixed disease severity rather than a genuine molecular predictor of collateral formation. Rani and Baig point to prior work by Bao and colleagues, published in Frontiers in Neurology, which demonstrated that the efficacy of indirect revascularization is intrinsic to an exquisite balance between disease stage progression and age-associated neoangiogenic potential, with different patient subsets exhibiting markedly different collateral formation trajectories.

The second major objection concerns the absence of a surgical comparator group. The Chen study included only patients who underwent indirect bypass, with no tissue samples from individuals who received direct bypass procedures, such as superficial temporal artery to middle cerebral artery anastomosis, or combined approaches that pair direct bypass with encephaloduroarteriomyosynangiosis. This distinction is not merely academic. Direct bypass restores hemodynamic function immediately by creating a high-flow surgical connection between extracranial and intracranial circulation, fundamentally altering shear stress and metabolic conditions in the adjacent cortical tissue from the moment the clips are released. Indirect bypass, by contrast, depends entirely on tissue-level angiogenesis unfolding over an extended postoperative period. The molecular programs activated in temporal muscle under these two radically different hemodynamic regimes are unlikely to be identical, yet without comparative tissue from combined or direct bypass patients, the Chen results cannot be generalised across surgical techniques.

Rani and Baig reference a retrospective study by Zhao and colleagues published in Experimental and Therapeutic Medicine, which examined 76 combined direct and indirect bypass procedures in adult Moyamoya patients and found significantly different clinical and angiographic outcomes compared to standalone indirect procedures, along with distinct local tissue perfusion pressures. They argue that the addition of tissue controls from patients undergoing combined direct-indirect bypass would allow future transcriptomic studies to separate expression patterns of extracellular matrix molecules that are specific to the indirect angiogenic process from those that merely reflect general tissue healing under different flow conditions. This is a critical distinction for any researcher hoping to translate collagen biology into a therapeutic target, because a signature that appears in all postoperative temporal muscle regardless of surgical approach is unlikely to be the molecular key to collateral vessel formation.

The third concern addresses clinical phenotyping, or rather the lack thereof. The Chen study grouped patients into binary collateral outcomes using the Matsushima grading system but did not account for the primary clinical presentation, namely whether patients presented with ischemic or hemorrhagic Moyamoya disease. These two phenotypes are not interchangeable variants of the same illness. Ischemic and hemorrhagic Moyamoya differ in their underlying pathophysiological mechanisms, in the degree of vessel wall inflammation, and in the postoperative trajectory of collateral formation. Hemorrhagic Moyamoya is characterised by microvascular fragility and altered expression of matrix metalloproteinases, enzymes that directly degrade extracellular matrix components and are intimately connected to temporal muscle tissue biology and postoperative angiogenesis. The unchecked accumulation of both phenotypes within a single transcriptomic cohort risks blending phenotype-specific molecular drivers of collateralisation into an averaged signal that corresponds to neither group.

Rani and Baig cite work by Ge and colleagues published in BMC Neurology, which specifically examined postoperative collateral formation after indirect bypass in hemorrhagic Moyamoya disease and found that collateral dynamics and angiographic response differ according to aetiology. They call for subgroup analyses of ischemic and hemorrhagic patients to determine whether the collagen-rich extracellular matrix signature identified by Chen and colleagues is preserved across both presentations or whether it is a molecular fingerprint unique to one phenotype. If the signature diverges between ischemic and hemorrhagic Moyamoya, then any future therapeutic strategy aimed at enhancing matrix remodelling would need to be tailored to the specific clinical context, a level of precision that the current mixed-cohort analysis simply cannot support.

In their concluding remarks, Rani and Baig strike a constructive tone, acknowledging that Chen and colleagues have provided a much-needed molecular underpinning of the relationship between extracellular matrix remodelling, collagen deposition in temporal muscle tissue, and successful postoperative collateralisation in Moyamoya disease. They emphasise, however, that angiogenic potential, disease stage, surgical approach variability, and clinical phenotype remain critical variables that must be addressed before these transcriptomic discoveries can be translated into targeted therapeutic tools. Their prescription is clear: multi-centre, phenotype-stratified, prospective cohorts with age-matched paediatric and adult subgroups, corrected for pre-operative Suzuki staging and cerebrovascular reserve, and including tissue comparators from direct and combined bypass procedures. Only through such rigorous design, they argue, can the field determine whether collagen-rich extracellular matrix biology is a genuine driver of collateral vessel formation or a molecular echo of patient heterogeneity.

Subject of Research: Moyamoya disease transcriptomics and postoperative angiogenesis

Article Title: Letter to Editor on Collagen‐Rich Extracellular Matrix and Postoperative Angiogenesis in Moyamoya Disease: The Need for Phenotype‐Stratified Transcriptomic Analysis

Article References: Rani, E., & Baig, M. F. (2026). Letter to Editor on Collagen‐Rich Extracellular Matrix and Postoperative Angiogenesis in Moyamoya Disease: The Need for Phenotype‐Stratified Transcriptomic Analysis. Journal of Cellular and Molecular Medicine, 30(19), Article e71400. https://doi.org/10.1111/jcmm.71400

Image Credits: AI Generated

DOI: 10.1111/jcmm.71400

Keywords: Moyamoya disease, transcriptomics, collagen, extracellular matrix, angiogenesis, revascularization, cerebrovascular, letter to editor, Letter, Editor, Rich, Extracellular

The researchers started from a deceptively simple premise. Acetylation, a post-translational modification in which acetyl groups are added to proteins, is known to govern vascular development, inflammatory responses, and cellular behavior in disorders ranging from atherosclerosis to thoracic aortic aneurysms. Yet its role in moyamoya disease had barely been explored. To fill that gap, the team mined publicly available transcriptomic datasets from the Gene Expression Omnibus, combining microarray data from 32 middle cerebral artery wall samples and eight superficial temporal artery samples, then intersected the resulting differentially expressed genes with a predefined set of 73 acetylation-regulatory genes.

That intersection yielded 19 acetylation-related differentially expressed genes, including BAZ1B, BRD3, and BRD7. Using consensus clustering, a statistical method that repeatedly reassigns samples to groups to test how stably they cohere, the researchers found that moyamoya disease splits most cleanly into two molecular subtypes when classified by the expression of these acetylation-related genes. The two clusters, labeled C1 and C2, were not merely statistical artifacts. Transcriptome-wide differential expression between them revealed 472 genes that varied by subtype, and pathway enrichment analysis showed that each cluster carried a distinct biological signature involving hypoxic injury, vascular remodeling, angiogenesis, and immune-inflammatory activity.

From this molecular heterogeneity, five candidate genes rose to the top: STK39, NEO1, PKNOX1, GOLT1B, and MTMR12. Each was expressed at lower levels in moyamoya disease than in non-moyamoya surgical controls, though the authors are careful to note that none met the transcriptome-wide false discovery rate threshold in the primary comparison. STK39 did cross that threshold when moyamoya samples were compared specifically with epilepsy controls, giving the team an exploratory but meaningful signal to pursue. STK39 encodes STE20-related proline/alanine-rich kinase, or SPAK, a downstream effector of WNK kinases that regulates cation-chloride cotransport and cellular ion homeostasis, and has previously been implicated in hypertension, Parkinson’s disease susceptibility, and autism risk.

To test whether these candidates were biologically relevant rather than statistical curiosities, the researchers measured serum concentrations of STK39 and MTMR12 by ELISA in a small preliminary cohort of three moyamoya patients and three healthy controls. Both proteins were significantly decreased in the patient group, with P values of 0.0140 and 0.0055 respectively. The authors stress that this sample size is far too small to constitute independent validation, but the concordance between transcriptomic and serum findings provided enough preliminary support to justify moving STK39 into the laboratory for functional testing.

That functional work took place in human brain microvascular endothelial cells, the very cells that line the cerebral microvasculature and bear the brunt of moyamoya pathology. Using siRNA-mediated knockdown, the researchers silenced STK39 and exposed the cells to either normal oxygen levels or hypoxic conditions mimicking the chronic cerebral hypoperfusion that defines the disease. The results were striking. Under hypoxia, STK39 knockdown promoted endothelial cell migration while simultaneously inhibiting proliferation, a combination that hints at the abnormal vascular remodeling seen in moyamoya disease, where vessels proliferate pathologically rather than functionally.

The molecular consequences of losing STK39 were equally revealing. Knockdown increased the expression of HIF-1α, the master transcriptional regulator of the hypoxic response, along with phosphorylated STAT3, cleaved Caspase-3, IL-6, CCL2, and VCAM-1. Together, these markers paint a picture of endothelial cells caught in a state of inflammatory activation and apoptotic stress, precisely the kind of endothelial dysfunction that could drive the intimal hyperplasia and vascular occlusion characteristic of moyamoya disease. The STAT3 pathway in particular is well established as a driver of angiogenesis and vascular smooth muscle cell phenotype switching, and the immune infiltration analysis showed that monocytes and macrophages differed significantly between the two molecular subtypes, linking the kinase to a broader inflammatory ecosystem.

Perhaps the most intriguing therapeutic signal came from trichostatin A, a histone deacetylase inhibitor added to the hypoxic, STK39-deficient cells as an exploratory pharmacological intervention. TSA partially reversed the enhanced migration, restored some of the lost proliferation, reduced the global lysine acetylation signal that had been elevated by the treatment, and dampened the expression of HIF-1α, phosphorylated STAT3, cleaved Caspase-3, IL-6, CCL2, and VCAM-1. While the authors emphasize that this does not establish acetylation-dependent regulation of STK39 itself, the partial rescue suggests that the acetylation machinery sits somewhere in the same pathological circuit and could represent a target for future mechanistic studies.

The study is candid about its limitations. The transcriptomic analysis relied on small, heterogeneous surgical control groups that included patients with intracranial aneurysms and epilepsy rather than perfectly matched healthy vessels. The serum validation involved only six participants. The in vitro hypoxia model represents an acute and simplified reduction in oxygen availability that cannot reproduce the chronic, fluctuating hemodynamic environment, altered shear stress, or the complex interactions among endothelial cells, smooth muscle cells, and immune cells that define moyamoya vascular pathology. The molecular clusters were defined from gene expression rather than direct measurements of protein acetylation, so they should not be read as confirmed high- and low-acetylation states.

Even with those caveats, the findings add a genuinely new dimension to moyamoya research. The disease has traditionally been framed through the lens of RNF213, the best-established susceptibility gene, and through vascular smooth muscle cell abnormalities. This study suggests that the molecular pathology extends beyond a single genetic determinant into a network of post-translational modification regulators, immune cell interactions, and hypoxia-driven endothelial responses. STK39, sitting at the intersection of ion homeostasis, blood pressure regulation, nitric oxide signaling, and now endothelial inflammatory activation, emerges as a candidate gene worth pursuing in larger, independent cohorts. If future work confirms its role and clarifies its relationship with acetylation pathways, it could open a path toward targeted interventions for a disease whose effective diagnosis and treatment remain limited precisely because its pathogenesis has stayed hidden for so long.

Subject of Research: Moyamoya disease

Article Title: STK39 is associated with endothelial dysfunction and inflammatory activation under hypoxic conditions in moyamoya disease

Article References: Liang, R., Zhou, Z., Chang, Y., Ye, X., Tang, Y., He, S., & Zhao, Y. (2026). STK39 is associated with endothelial dysfunction and inflammatory activation under hypoxic conditions in moyamoya disease. Frontiers in Human Neuroscience, 20, Article 1854099. https://doi.org/10.3389/fnhum.2026.1854099

Image Credits: AI Generated

DOI: 10.3389/fnhum.2026.1854099

Keywords: moyamoya disease, STK39, acetylation, endothelial dysfunction, hypoxia, inflammation, cerebrovascular disease, STAT3, HIF-1α, trichostatin A, associated, endothelial

The classical definition of moyamoya disease rests on two features: progressive stenosis and occlusion of the terminal portion of the internal carotid artery, where it enters the circle of Willis, and the appearance of abnormal basal collateral networks that resemble a puff of smoke on angiography, the meaning of the Japanese word moyamoya. When the same angiographic pattern occurs in patients with identifiable associated conditions, such as neurofibromatosis or prior radiation therapy, it is traditionally labeled moyamoya syndrome. Ota contends that this dichotomy, while clinically convenient, does not correspond to consistent differences in vascular pathology. Radiological patterns and disease progression are often indistinguishable between the two groups, and unilateral or secondary cases can evolve into bilateral phenotypes identical to idiopathic disease.

The historical analysis at the heart of the review is revealing. Before the term moyamoya was coined by Suzuki and Takaku in 1969, Japanese investigators described these patients under a broader anatomical heading, and early national consensus documents were titled Guidelines for the Diagnosis of Occlusive Disease of the Circle of Willis. In that original framing, steno-occlusive disease of the circle of Willis was a descriptive category encompassing heterogeneous non-atherosclerotic intracranial arteriopathies, without assuming a single underlying mechanism. Over time, the striking and reproducible moyamoya phenotype absorbed the broader concept, particularly in East Asian clinical practice, until the two became implicitly equated. Western classification systems took a different path, generally interpreting moyamoya-like collateral networks as nonspecific responses to chronic arterial occlusion. The result has been a phenotype-centered framework in Japan and an etiology-centered approach in Western practice, with little common ground between them.

To restore that common ground, the review proposes an operational definition of steno-occlusive disease of the circle of Willis with explicit anatomical boundaries: progressive steno-occlusive disease involving the supraclinoid or terminal internal carotid artery, the proximal anterior cerebral artery, the proximal middle cerebral artery, and the origin of the posterior communicating artery, while excluding isolated distal branch disease and primary basilar atherosclerosis. Within this territory, moyamoya vasculopathy is repositioned as the predominant but non-exclusive angiographic phenotype. The review also describes early or precollateral stages, in which focal stenosis of the terminal carotid artery occurs without established moyamoya vessels, and non-moyamoya or mixed patterns, in which circle-of-Wilis-centered stenosis fails to fulfill classical criteria. These categories describe vascular phenotypes rather than etiologic disease entities, and they may evolve or overlap over time.

A key insight of the framework is the temporal dissociation between arterial narrowing and collateral formation. The basal collaterals that give moyamoya its name have long been treated as disease-defining, but the review argues they are better understood as adaptive vascular responses to chronic arterial narrowing, appearing only after hemodynamic compensation becomes necessary. Early-stage cases presenting with isolated stenosis are difficult to classify under phenotype-based criteria, yet within the location-defined framework they can be interpreted as early disease, supporting serial imaging and longitudinal assessment over rigid categorical labeling. This perspective may reduce diagnostic uncertainty at initial presentation, when the angiographic picture is incomplete.

Genetic evidence provides some of the strongest support for this reconceptualization. Genome-wide association studies identified RNF213, particularly the p.R4810K variant, as the major susceptibility factor for moyamoya disease, with the association most pronounced in Japanese and Korean patients and less frequent in Chinese patients. The marked geographic distribution of p.R4810K supports a founder effect rather than a universally shared moyamoya-associated variant. In European-ancestry patients, p.R4810K is extremely rare or absent, yet sequencing studies have identified multiple heterogeneous rare RNF213 variants, including p.D4013N, p.R4062Q, and p.A4399T, that preferentially cluster within the C-terminal region encompassing the RING-finger domain, although the pathogenic significance of individual variants remains incompletely established. No single RNF213 variant, in other words, accounts for the shared vascular phenotype across populations.

Even more consequential is the question of penetrance. Many heterozygous carriers of RNF213 variants remain asymptomatic throughout life, indicating that the gene alone is insufficient to determine disease expression. Conversely, increasing genetic burden appears to influence severity: homozygous individuals tend to present with earlier onset, more severe steno-occlusive changes, broader vascular involvement, more rapid progression, posterior circulation involvement, and increased frequency of extracranial manifestations such as pulmonary artery stenosis. Recent evidence also suggests additional modifiers, with the HAPLN3 p.T34A variant proposed as a factor associated with increased penetrance among carriers of p.R4810K, supported by whole-exome sequencing and endothelial-cell experiments, though these findings remain preliminary. RNF213 variants have also been linked to non-moyamoya arteriopathies, including intracranial atherosclerotic disease and large-artery ischemic stroke, further undermining the idea of a disease-defining gene.

Functionally, RNF213 encodes a protein with ATPase and ubiquitin ligase activity implicated in angiogenesis, endothelial function, and vascular remodeling, with emerging roles in immune and inflammatory pathways including interferon signaling and host defense. This supports a model in which RNF213 acts as a context-dependent modifier that amplifies vascular vulnerability under inflammatory or environmental stress. But genetic factors alone cannot explain the most puzzling feature of the condition: its remarkably consistent localization to the terminal internal carotid artery and circle of Willis across diverse clinical contexts. To address this, the review turns to developmental biology, noting that mural cells such as vascular smooth muscle cells and pericytes arise from heterogeneous embryological origins, with cephalic neural crest cells contributing to the forebrain vasculature in a regionally restricted manner. The concept of vascular cephalic neurocristopathy has been proposed as a possible explanation for the preferential involvement of the terminal carotid region, although the review is careful to note that direct lineage mapping of human cerebral arteries remains limited and the hypothesis remains unproven.

The resulting multi-hit model integrates three dimensions: developmental and anatomical features that define the disease-prone territory, genetic factors such as RNF213 that influence susceptibility and phenotypic expression, and environmental or inflammatory processes that act as triggers of onset and progression. This formulation separates lesion localization from genetic determinants and offers a coherent explanation for anatomical specificity, phenotypic variability, and incomplete penetrance, though it remains hypothetical and requires validation through integrated genetic, developmental, and longitudinal studies. Clinically, the framework does not alter established treatment strategies at present. Surgical revascularization remains the principal treatment for symptomatic disease with impaired cerebral perfusion, and decisions should continue to rest on clinical presentation, progression, and objective hemodynamic evidence rather than on the new label. The potential value lies instead in the precollateral stage: stenosis centered on the circle of Willis without established moyamoya vessels should not automatically be dismissed as unrelated or nonspecific, and longitudinal imaging with hemodynamic assessment may help identify progression toward a classical phenotype, justifying closer surveillance without extending surgical indications beyond current evidence.

The review acknowledges its own limitations candidly. The proposed anatomical boundaries remain partially arbitrary, overlap with other intracranial arteriopathies may occur, and genetic associations are influenced by population structure and phenotypic heterogeneity. No biomarker is currently specific enough for diagnosis, and emerging candidates such as circulating inflammatory mediators, endothelial markers, microRNAs, and angiogenic factors remain clinically unestablished. No disease-modifying therapy or gene therapy targeting RNF213 variants is available, although patient-derived induced pluripotent stem cell and gene-editing platforms offer preclinical routes toward therapeutic targets. The framework is presented as an iterative model rather than a fixed taxonomy, one whose value lies in providing an anatomical basis for integrating emerging genetic, imaging, and biological insights. If future prospective studies confirm that the proposed phenotypes represent biologically meaningful subgroups, the field may move toward classification systems built not on a single angiographic pattern or a single gene, but on the shared territory where the disease begins.

Subject of Research: Reconceptualizing moyamoya vasculopathy within steno-occlusive disease of the circle of Willis

Article Title: Reframing moyamoya vasculopathy within steno-occlusive disease of the circle of Willis

Article References: Ota, T. (2026). Reframing moyamoya vasculopathy within steno-occlusive disease of the circle of Willis. Frontiers in Stroke, 5, Article 1890618. https://doi.org/10.3389/fstro.2026.1890618

Image Credits: AI Generated

DOI: 10.3389/fstro.2026.1890618

Keywords: moyamoya disease, circle of Willis, RNF213, stroke, intracranial arteriopathy, genetic susceptibility, neural crest, cerebral revascularization, vascular remodeling, moyamoya syndrome, steno-occlusive disease, neurovascular imaging

Moyamoya vasculopathy is an umbrella term covering two related but distinct conditions. Moyamoya disease is a chronic, progressive narrowing of the terminal internal carotid arteries and the proximal segments of the anterior and middle cerebral arteries, accompanied by a hazy network of tiny collateral vessels at the base of the brain that resembles a puff of smoke on angiography, the meaning of the Japanese word moyamoya. Moyamoya syndrome, by contrast, produces a similar vascular picture but arises secondarily, most often when intracranial atherosclerosis mimics the appearance of the idiopathic disease. Distinguishing the two matters enormously, because their underlying biology, prognosis, and treatment strategies diverge, yet conventional angiography alone often cannot separate them reliably.

The research team, led by investigators at a major Chinese hospital registry, enrolled 398 consecutive adults with radiologically confirmed moyamoya vasculopathy between September 2017 and April 2025. Every patient underwent imaging on the same 3.0-Tesla MR scanner using a standardized protocol that included T1-weighted, T2-weighted, FLAIR, diffusion-weighted, and time-of-flight angiographic sequences, along with high-resolution vessel wall imaging. By scanning all participants on a single machine, the investigators eliminated the interscanner variability that often plagues multicenter imaging studies, allowing vessel wall measurements to be compared directly across the cohort.

High-resolution MRI has emerged in recent years as the decisive tool for separating the two etiologies. In moyamoya disease, the affected arteries typically show concentric, uniform wall thickening, a reduction in the outer diameter of the vessel, and negative or constrictive remodeling, meaning the artery wall shrinks inward as the disease progresses rather than expanding outward. Atherosclerosis-associated moyamoya vasculopathy displays the opposite signature: irregular, eccentric thickening caused by lipid-rich or hemorrhagic plaques, and positive or expansive remodeling, in which the vessel enlarges to accommodate plaque growth. Applying these criteria, the researchers classified 279 patients as having moyamoya disease and 61 as having the atherosclerosis-associated form.

The clinical profiles of the two groups differed in telling ways. Patients with moyamoya disease were more frequently female, consistent with the well-established female predominance of the idiopathic condition, and were significantly more likely to report a family history of early-onset stroke in first-degree relatives, a hallmark of the genetic predisposition linked to the RNF213 susceptibility gene. They also showed more frequent involvement of the posterior cerebral arteries, reflecting the diffuse, whole-circle-of-Willis nature of the disease. The atherosclerosis-associated group, though similar in age, lacked these familial and posterior-circulation signatures, reinforcing the view that it represents a secondary, plaque-driven process rather than a genetically driven arteriopathy.

To determine which imaging features actually tracked with stroke, the team took an unusually granular approach: they analyzed each cerebral hemisphere separately. Of the 558 hemispheres in the moyamoya disease group, 169 had suffered middle cerebral artery territory infarcts, visible as acute or chronic lesions on MRI, while 389 remained asymptomatic. Because the two hemispheres of the same patient are statistically correlated, the researchers used generalized estimating equations, a regression framework that treats each patient as a cluster, adjusting for age, sex, hypertension, diabetes, hyperlipidemia, smoking, alcohol use, and family history of early stroke. This design allowed each hemisphere to serve, in effect, as its own internal comparison.

The results in moyamoya disease were strikingly consistent. Ischemic hemispheres were independently associated with greater middle cerebral artery stenosis, more advanced Suzuki stage, and higher stenosis scores on the internal carotid, middle cerebral, and posterior cerebral arteries. The posterior cerebral artery score carried the strongest effect, with each one-point increase more than doubling the odds of ischemia. Intriguingly, the remodeling index of the middle cerebral artery showed the opposite relationship: hemispheres with more constrictive remodeling were more likely to be ischemic, suggesting that for a given degree of luminal narrowing, the inward shrinkage of the vessel wall compounds hemodynamic compromise, while better-preserved or compensating vessels maintain perfusion.

In the atherosclerosis-associated group, the picture inverted almost completely. Here, the degree of middle cerebral artery stenosis, the Suzuki stage, and the carotid and posterior circulation scores all lost their statistical significance after adjustment. What remained significant were the remodeling index of the middle cerebral artery, which was positively associated with ischemia, and involvement of the anterior cerebral artery. This pattern suggests that in plaque-driven moyamoya vasculopathy, it is not the raw percentage of narrowing that matters but how the vessel wall remodels around the plaque and whether the anterior circulation can still serve as a collateral pathway. Positive remodeling, long recognized as a marker of vulnerable atherosclerotic plaques, appears to signal danger rather than compensation in this group.

The authors are careful to frame these findings as cross-sectional associations rather than proven predictors of future stroke, noting that their definition of ischemic hemispheres included both acute and old infarcts, and that the retrospective, single-center design and the relatively small atherosclerotic subgroup impose limits on generalizability. They also acknowledge that a small fraction of patients lacked internal carotid artery involvement on angiography, a population that the revised 2022 diagnostic criteria would technically exclude, though sensitivity analyses excluding these patients left the results qualitatively unchanged. Even so, the hemisphere-level, cluster-adjusted analysis represents one of the most detailed noninvasive characterizations of moyamoya vasculopathy published to date.

The clinical implications are potentially far-reaching. For patients with moyamoya disease, quantitative measures such as stenosis severity, Suzuki stage, and combined arterial scores, together with evidence of constrictive remodeling, could help identify which hemisphere is at highest risk and guide the timing of revascularization surgery. For those with the atherosclerosis-associated form, attention should shift toward plaque behavior and anterior circulation collateral integrity rather than stenosis percentage alone, aligning management more closely with modern intracranial atherosclerosis care, where recent long-term evidence has questioned the value of stenting and pointed instead toward bypass options in selected cases. The study’s core lesson is that moyamoya vasculopathy is not one disease but two, and the artery wall itself, imaged at high resolution, tells clinicians which one they are treating.

Subject of Research: Etiology-specific associations between high-resolution MRI vessel wall features and cerebral infarction in adult moyamoya vasculopathy

Article Title: High‐Resolution MRI Revealed Different Etiology‐Specific Associations With Cerebral Infarction in Adult Moyamoya Vasculopathy

Article References: Han, G., Pan, J., Hong, Y., Fan, X., Yao, M., Zhou, L., Zhu, Y., Feng, F., & Ni, J. (2026). High‐Resolution MRI Revealed Different Etiology‐Specific Associations With Cerebral Infarction in Adult Moyamoya Vasculopathy. Annals of Clinical and Translational Neurology, 13(10), 2057-2067. https://doi.org/10.1002/acn3.70380

Image Credits: AI Generated

DOI: 10.1002/acn3.70380

Keywords: moyamoya disease, moyamoya vasculopathy, high-resolution MRI, vessel wall imaging, cerebral infarction, intracranial atherosclerosis, remodeling index, Suzuki stage, collateral circulation, stroke risk, RNF213, revascularization