Understanding genomic medicine for thoracic aortic disease through the lens of induced pluripotent stem cells.

Thoracic aortic disease (TAD) is often silent until a life-threatening complication occurs. However, genetic information can inform both identification and treatment at an early stage. Indeed, a diagnosis is important for personalised surveillance and intervention plans, as well as cascade screening of family members. Currently, only 20% of heritable TAD patients have a causative mutation identified and, consequently, further advances in genetic coverage are required to define the remaining molecular landscape. The rapid expansion of next generation sequencing technologies is providing a huge resource of genetic data, but a critical issue remains in functionally validating these findings. Induced pluripotent stem cells (iPSCs) are patient-derived, reprogrammed cell lines which allow mechanistic insights, complex modelling of genetic disease and a platform to study aortic genetic variants. This review will address the need for iPSCs as a frontline diagnostic tool to evaluate variants identified by genomic discovery studies and explore their evolving role in biological insight through to drug discovery.

Management Modalities of Primary Bladder Neck Obstruction in Young Adult Men: A Systematic Review and Meta-analysis.

OBJECTIVE: This systematic review was done to critically appraise the various evidence available in the literature for the presenting symptoms, diagnosis, and management modalities for primary bladder neck obstruction diagnosed on invasive urodynamics in young adult men 18-50 years of age. METHODS: A search was conducted on PubMed, Embase, and Cochrane Central Register of Controlled Trials databases until July 2022 to find English-language studies relevant to the topic. RESULTS: A total of 10 studies were included. The estimated difference in International Prostate Symptom Score between baseline and 3 months in the subgroup of medical and surgical treatment was found to be -8.82 and -11.25, respectively (P = .37), and after 12 months, it was found to be -7.69 and -17.70 respectively (P .001). The pooled estimate for the difference in Qmax between baseline and 3 months after medical and surgical treatments in the subgroup was found to be 2.92 and 7.03, respectively (P = .18), and after 12 months, it was found to be 4.54 and 7.74, respectively (P .001). The pooled estimate of the difference in post-void residue before and after 3 months of medical and surgical treatments in a subgroup was found to be -31.15 and -70, respectively (P .001), and after 12 months, it was found to be -31.49 and -156.00, respectively (P .001). Quality of life scores improved in both subgroups. CONCLUSION: The alpha-blockers are effective in managing primary bladder neck obstruction in the short term, while bladder neck incision is preferred for better longterm outcomes.

Can we predict and manage persistent storage and voiding LUTS following bladder outflow resistance reduction surgery in men? ICI-RS 2023.

AIMS: Lower urinary tract symptoms (LUTS) persist in up to 50% of patients after bladder outflow resistance reduction surgery (BORRS) in men. Our think tank aims to address the predictive factors for persistent LUTS after BORRS and to propose the recommendations for future research to enable improved better patient counseling and selection by more accurate prediction of treatment outcome. METHODS: A think tank of ICI-RS gathered in 2023, Bristol, UK, to discuss the pre and postsurgical clinical and urodynamic evaluation of men undergoing BORRS and whether it is possible to predict which men will have persistent LUTS after BORRS. RESULTS: Our think tank agrees that due to the multifactorial, and still not fully understood, etiology of male LUTS it is not possible to precisely predict in many men who will have persistent LUTS after BORRS. However, severe storage symptoms (overactive bladder, OAB) in association with low volume and high amplitude detrusor overactivity and low bladder capacity in preoperative urodynamics, increase the likelihood of persistent OAB/storage symptoms after BORRS. Furthermore, patients who are clearly obstructed and have good bladder contractility on preoperative pressure flow studies do better postoperatively compared to their counterparts. However, the benefit of pressure flow studies is decreased in patients who do not acceptably void during the study. Poor voiding after BORRS may occur due to persistent obstruction or detrusor underactivity. CONCLUSION: Future research is needed to increase our understanding of why male LUTS persist after surgery, and to enable better patient selection and more precise patient counseling before BORRS.

The Use of Uroflowmetry as a Diagnostic Test.

PURPOSE OF REVIEW: Uroflowmetry is widely used for initial non-invasive evaluation of lower urinary tract disorders. Current clinical use is mostly restricted to a scrutiny of the maximum flow rate and uroflow pattern recorded by a conventional flowmeter in a health care facility. There are several advancements in our understanding and in available technologies that promise to transform clinical utilization of this simple test. RECENT FINDINGS: Several aspects of the uroflow test in addition to maximum flow rate and uroflow pattern show potential diagnostic utility. This includes flow acceleration, uroflow indices, uroflow-electromyography including lag time, stop uroflow test, and uroflow-based nomograms. There are initial attempts to use artificial intelligence in analysis. There is also new data with regard to factors influencing variability of uroflow testing that might influence the diagnostic value in as yet uncertain ways including diurnal variability, postural variability, locational variability, and operator variability. There are new technologies for uroflow testing in a home environment allowing for easy repetition. However, there are several challenges owing to a paucity of clinical data and standardization. There are also critical lacunae in terminology that need to be addressed. There are exciting new advancements in the field of uroflowmetry. However, there is need to standardize and validate the newer uroflow tracing analyses and technologies.

The impact of time to death in donors after circulatory death on recipient outcome in simultaneous pancreas-kidney transplantation.

The time to arrest donors after circulatory death is unpredictable and can vary. This leads to variable periods of warm ischemic damage prior to pancreas transplantation. There is little evidence supporting procurement team stand-down times based on donor time to death (TTD). We examined what impact TTD had on pancreas graft outcomes following donors after circulatory death (DCD) simultaneous pancreas-kidney transplantation. Data were extracted from the UK transplant registry from 2014 to 2022. Predictors of graft loss were evaluated using a Cox proportional hazards model. Adjusted restricted cubic spline models were generated to further delineate the relationship between TTD and outcome. Three-hundred-and-seventy-five DCD simultaneous kidney-pancreas transplant recipients were included. Increasing TTD was not associated with graft survival (adjusted hazard ratio HR 0.98, 95% confidence interval 0.68-1.41, P = .901). Increasing asystolic time worsened graft survival (adjusted hazard ratio 2.51, 95% confidence interval 1.16-5.43, P = .020). Restricted cubic spline modeling revealed a nonlinear relationship between asystolic time and graft survival and no relationship between TTD and graft survival. We found no evidence that TTD impacts pancreas graft survival after DCD simultaneous pancreas-kidney transplantation; however, increasing asystolic time was a significant predictor of graft loss. Procurement teams should attempt to minimize asystolic time to optimize pancreas graft survival rather than focus on the duration of TTD.

Can we predict whether a man with acute or chronic urinary retention will void after bladder outflow resistance reduction surgery? ICI-RS 2023.

AIMS: To address the predictive factors of a successful voiding after bladder outflow resistance reduction surgery (BORRS) in men presenting with acute or chronic urinary retention (UR). METHODS: A think tank (TT) of ICI-RS was gathered in 2023, Bristol, UK, to discuss several aspects of the problem, such as the pathophysiology of UR, the clinical and urodynamic evaluation of men with UR and whether it is possible to predict which men will be able to successfully void after treatment with contemporary surgical options. RESULTS: The TT agreed that successful voiding after BORRS depends on several factors but that a strong recommendation cannot be made regarding preoperative evaluation and whether there are predictive factors of success because of the heterogeneity of patients and methodology in published trials. The diagnosis of obstruction in men with UR may be challenging when there is apparent reduced detrusor contraction during urodynamic studies. Even in the absence of bladder contractility there is documentation of such cases that have voided adequately after BORRS. Still, detrusor underactivity and inadequate relief of prostatic obstruction are the main causes of an unsuccessful voiding after BORRS. Conventional resection and enucleation methods remain the most successful surgeries in relieving UR in men, whereas the efficacy of minimally invasive surgical treatments needs to be assessed further. CONCLUSION: Research is needed to understand the pathophysiology of UR and the predictors of successful voiding after different types of BORRS in men with UR.

Three-dimensional co-culturing of stem cell-derived cardiomyocytes and cardiac fibroblasts reveals a role for both cell types in Marfan-related cardiomyopathy.

Pathogenic variants in the FBN1 gene, which encodes the extracellular matrix protein fibrillin-1, cause Marfan syndrome (MFS), which affects multiple organ systems, including the cardiovascular system. Myocardial dysfunction has been observed in a subset of patients with MFS and in several MFS mouse models. However, there is limited understanding of the intrinsic consequences of FBN1 variants on cardiomyocytes (CMs). To elucidate the CM-specific contribution in Marfan's cardiomyopathy, cardiosphere cultures of CMs and cardiac fibroblasts (CFs) are used. CMs and CFs were derived by human induced pluripotent stem cell (iPSC) differentiation from MFS iPSCs with a pathogenic variant in FBN1 (c.3725G>A; p.Cys1242Tyr) and the corresponding CRISPR-corrected iPSC line (Cor). Cardiospheres containing MFS CMs show decreased FBN1, COL1A2 and GJA1 expression. MFS CMs cultured in cardiospheres have fewer binucleated CMs in comparison with Cor CMs. 13% of MFS CMs in cardiospheres are binucleated and 15% and 16% in cardiospheres that contain co-cultures with respectively MFS CFs and Cor CFs, compared to Cor CMs, that revealed up to 23% binucleation when co-cultured with CFs. The sarcomere length of CMs, as a marker of development, is significantly increased in MFS CMs interacting with Cor CF or MFS CF, as compared to monocultured MFS CMs. Nuclear blebbing was significantly more frequent in MFS CFs, which correlated with increased stiffness of the nuclear area compared to Cor CFs. Our cardiosphere model for Marfan-related cardiomyopathy identified a contribution of CFs in Marfan-related cardiomyopathy and suggests that abnormal early development of CMs may play a role in the disease mechanism.

Establishing initial resting abdominal pressure in children undergoing urodynamics.

INTRODUCTION: The International Continence Society recommends zeroing of transducers to the atmospheric pressure for invasive urodynamics. The range of abdominal pressure relative to atmospheric pressure is well-known in adults but has not been described in children. This prospective observational study was carried out to establish baseline abdominal in children. MATERIALS AND METHODS: Prospective, multicenter, observational study of 100 children aged 0-18 years undergoing invasive urodynamics using water-filled systems. Initial resting abdominal pressure, intravesical pressure and detrusor pressure were recorded in supine, sitting, and standing position (as age- and diagnosis-appropriate). This data was analyzed using SPSS 20.0.0 with regard to age, gender, height, weight, body mass index, and underlying diagnosis (classified as neurogenic or non-neurogenic). Nonparametric tests were used (2-sided p < 0.05, significant). RESULTS: Initial resting abdominal pressure (inter-quartile range) in children was between 5 and 15 cmH2 O in the supine, 13-20 cmH2 O in the sitting, and 15-21 cmH2 O in the standing position. These pressures were not consistently influenced by age, gender, height, weight or underlying diagnosis. The initial resting detrusor pressure was noted to be 0-4 cmH2 O without any difference based on posture. Limitations include use of two-tube technique, relatively small number of subjects across each age group, wide range of underlying diagnoses and need for manual smoothing of some traces. CONCLUSION: This study defines initial resting abdominal pressure at urodynamics in children and notes that, as with adults, it is possible to define widely applicable ranges regardless of individual characteristics. These pressures appear lower than those noted historically in adults.

How do we make progress in phenotyping patients with lower urinary tract such as overactive bladder and underactive detrusor, including using urine markers and microbiome data, to personalize therapy? ICI-RS 2023-Part 2.

INTRODUCTION: Overactive bladder (OAB) and underactive bladder (UAB) could be associated with metabolic syndrome, affective disorders, sex hormone deficiency, changes in urinary microbiota, functional gastrointestinal disorders, or autonomic nervous system dysfunction. OBJECTIVES: The aim of this Think Tank was to provide a guide on how to investigate OAB and/or detrusor underactivity (DU) patients to better clarify the underlying pathophysiology and possibly personalize the treatment. METHODS: A compendium of discussion based on the current evidence related to phenotyping patients with OAB or DU using urodynamic tests, functional neuro-imaging, urinary markers, and microbiome. RESULTS AND CONCLUSIONS: The article emphasizes the critical significance of adopting a comprehensive yet tailored approach to phenotyping patients with lower urinary tract (LUT) symptoms, such as OAB and UAB. The intricate interplay between the LUT and various factors, metabolic, neurological, psychological, and gastrointestinal can define unique LUT profiles, enabling personalized therapies to replace the one-size-fits-all approach.

How do we make progress in phenotyping patients with LUT such as OAB and underactive detrusor, including using urine markers and microbiome data, in order to personalize therapy? ICI-RS 2023: Part 1.

INTRODUCTION: Overactive bladder (OAB) and Underactive bladder (UAB) could be associated with metabolic syndrome, affective disorders, sex hormone deficiency, changes in urinary microbiota, functional gastrointestinal disorders, or autonomic nervous system dysfunction. OBJECTIVES: The aim of this Think Tank was to provide a guide on how to investigate OAB and/or detrusor underactivity (DU) patients to better clarify the underlying pathophysiology and possibly personalize the treatment. METHODS: A compendium of discussion based on the current evidence related to phenotyping patients with OAB or DU investigating metabolic, neurogical, psychological and gastrointestinal aspects with the aim to personalize the treatment. RESULTS AND CONCLUSIONS: The article emphasizes the critical significance of adopting a comprehensive yet tailored approach to phenotyping patients with lower urinary tract symptoms, such as OAB and UAB. The intricate interplay between the lower urinary tract and various factors, metabolic, neurological, psychological, and gastrointestinal can define unique LUT profiles, enabling personalized therapies to replace the one-size-fits-all approach.

Lifelong LUTS: Understanding the bladder's role and implications across transition phases, a comprehensive review.

INTRODUCTION: Lower urinary tract symptoms (LUTSs) are a diverse array of urinary and pelvic dysfunctions that can emerge from childhood, extend through adulthood, and persist into older age. This narrative review aims to provide a comprehensive perspective on the continuum of LUTS and shed light on the underlying mechanisms and clinical implications that span across the lower urinary tract. METHODS: A panel of five experts from Belgium, the Netherlands, India, Denmark, and the United States participated in an intensive research to explore and pinpoint existing insights into the lifelong concept of LUTS, particularly at the pelvic level. The experts reviewed the existing literature and held a webinar to discuss their findings. RESULTS: Childhood LUTS can persist, resolve, or progress into bladder underactivity, dysfunctional voiding, or pain syndromes. The Lifelong character can be explained by pelvic organ cross-talk facilitated through complex neurological and nonneurological interactions. At the molecular level, the role of vasopressin receptors in the bladder's modulation and their potential relevance to therapeutic strategies for LUTS are explored. Frailty emerges as a parallel concept to lifelong LUTS, with a complex and synergistic relationship. Frailty, not solely an age-related condition, accentuates LUTS severity with insufficient evidence regarding the effectiveness and safety profile of the available therapeutic modalities. CONCLUSION: Understanding lifelong LUTSs offers insights into genetic, anatomical, neurological, and molecular mechanisms. Further research could identify predictive biomarkers, elucidate the role of clinically translatable elements in pelvic cross-talk, and uncover molecular signatures for personalized management.

Exploring lifelong overactive bladder: Transitions, evidence, and clinical implications; A modified Delphi process.

INTRODUCTION: Overactive bladder (OAB) is a prevalent urological condition characterized by urinary urgency, with or without urgency urinary incontinence, accompanied by increased daytime frequency and nocturia. However, the current definition of OAB lacks a specified time frame, hindering our understanding of the temporal aspects and transitions that occur within the OAB spectrum. METHODS: A modified Delphi study was conducted in three rounds, involving a panel of international experts in functional urology, urogynaecology, geriatrics, transitional medicine, and pediatric urology. The study took place between February 2023 and June 2023 and employed two sequential rounds of online surveys, followed by a final hybrid group discussion session in June 2023. RESULTS: The Delphi process resulted in a consensus definition of lifelong OAB as a persistent and continuous condition that may manifest differently from birth and evolve over time, with varying levels of clinical perception. The course of its progression is influenced by transition periods and modifying factors, mainly anatomical, hormonal, and psychosocial/stressors. Three main transition periods were identified: achievement of daytime continence, adulthood to elderly, and transition to frail elderly. The panel also considered the therapeutic and diagnostic implications of lifelong OAB, as well as future research prospects in terms of importance and feasibility. CONCLUSIONS: Future longitudinal research is needed to develop this concept and further identify transitions and temporal dynamics.

Can apparently transient life events trigger long-term lower urinary tract symptoms?

INTRODUCTION: One-time life events such as neurological injury can result in lifelong lower urinary tract symptoms (LUTS). However, it is unclear whether an apparently transient life event can also trigger long-term LUTS. This review examines the possibility of an association and hypothesizes the pathogenesis. METHODS: A pubmed search was conducted using the MeSH words "life change events," "child abuse," or "stress disorders, Posttraumatic", and LUTS. Additional manuscripts were identified by a hand and citation search. RESULTS: Long-term LUTS was noted following temporally remote childhood sexual abuse, adverse childhood experiences, and stressful experiences in adults. There was evidence for an association of childhood sexual abuse and adverse childhood events with both storage as well as voiding LUTS. There was limited evidence that the number of adverse childhood events might increase the risk and severity of LUTS. There was evidence of an association between post-traumatic stress disorder in adults and LUTS. The finding of mental health disorders in such patients could explain some but not all of the observed association suggesting that other factors might also be important. CONCLUSIONS: There is an association noted between apparently transient lifetime events and the subsequent reporting of LUTS. The timing of these adverse experiences might be important in determining the propensity for clinical manifestation. There is a need to explore this association, establish causality, and determine the underlying etiopathogenesis.

Should hormone replacement therapy (any route of administration) be considered in all postmenopausal women with lower urinary tract symptoms? Report from the ICI-RS 2023.

AIMS: This International Consultation on Incontinence-Research Society report aims to summarize the evidence and uncertainties regarding the use of hormone replacement therapy by any route in the management of lower urinary tract symptoms (LUTS) including recurrent urinary tract infections (rUTI), with a review of special considerations for the elderly. Research question proposals to further this field have been highlighted. METHODS: An overview of the existing evidence, guidelines, and consensus regarding the use of topical or systemic estrogens in the management of LUTS. RESULTS: There are currently evidence and recommendations to offer topical estrogens to postmenopausal women with overactive bladder symptoms as well as postmenopausal women with rUTIs. Systemic estrogens however have been shown in a meta-analysis to have a negative effect on LUTS and, therefore are not currently recommended. CONCLUSIONS: Although available evidence and recommendations exist for the use of topical estrogens, few women are commenced on these in primary care. There remain large gaps still within our knowledge of the use of estrogens within the management of LUTS, particularly on when it should be commenced, the length of time treatment should be continued for, and barriers to prescribing.

British Transplantation Society guidelines on abdominal organ transplantation from deceased donors after circulatory death.

The British Transplantation Society (BTS) 'Guideline on transplantation from deceased donors after circulatory death' has recently been updated and this manuscript summarises the relevant recommendations in abdominal organ transplantation from Donation after Circulatory Death (DCD) donors, encompassing the chapters on liver, kidney, pancreas and islet cell transplantation.

Proinflammatory cytokines driving cardiotoxicity in Covid-19.

AIMS: Cardiac involvement is common in patients hospitalised with COVID-19 and correlates with an adverse disease trajectory. While cardiac injury has been largely attributed to direct viral cytotoxicity, serum-induced cardiotoxicity secondary to serological hyperinflammation constitutes a potentially amenable mechanism that remains largely unexplored. METHODS AND RESULTS: To investigate serological drivers of cardiotoxicity in COVID-19 we have established a robust bioassay that assessed the effects of serum from COVID-19 confirmed patients on human embryonic stem cell (hESC)-derived cardiomyocytes. We demonstrate that serum from COVID-19 positive patients significantly reduced cardiomyocyte viability independent of viral transduction, an effect that was also seen in acute respiratory distress syndrome (ARDS). Serum from patients with greater disease severity led to worse cardiomyocyte viability and this significantly correlated with levels of key inflammatory cytokines, including IL-6, TNF-α, IL1-ß, IL-10, CRP and neutrophil to lymphocyte ratio with a specific reduction of CD4+ and CD8+ cells. Combinatorial blockade of IL-6 and TNF-α partly rescued the phenotype and preserved cardiomyocyte viability and function. Bulk RNA sequencing of serum-treated cardiomyocytes elucidated specific pathways involved in the COVID-19 response impacting cardiomyocyte viability, structure and function. The observed effects of serum-induced cytotoxicity were cell-type selective as serum exposure did not adversely affect microvascular endothelial cell viability but resulted in endothelial activation and a procoagulant state. CONCLUSION: These results provide direct evidence that inflammatory cytokines are at least in part responsible for the cardiovascular damage seen in COVID-19 and characterise the downstream activated pathways in human cardiomyocytes. The serum signature of patients with severe disease indicates possible targets for therapeutic intervention.

Selenoprotein deficiency disorder predisposes to aortic aneurysm formation.

Aortic aneurysms, which may dissect or rupture acutely and be lethal, can be a part of multisystem disorders that have a heritable basis. We report four patients with deficiency of selenocysteine-containing proteins due to selenocysteine Insertion Sequence Binding Protein 2 (SECISBP2) mutations who show early-onset, progressive, aneurysmal dilatation of the ascending aorta due to cystic medial necrosis. Zebrafish and male mice with global or vascular smooth muscle cell (VSMC)-targeted disruption of Secisbp2 respectively show similar aortopathy. Aortas from patients and animal models exhibit raised cellular reactive oxygen species, oxidative DNA damage and VSMC apoptosis. Antioxidant exposure or chelation of iron prevents oxidative damage in patient's cells and aortopathy in the zebrafish model. Our observations suggest a key role for oxidative stress and cell death, including via ferroptosis, in mediating aortic degeneration.

How should we assess the cardiovascular system in patients presenting with bothersome nocturia? ICI-RS 2023.

AIMS: The link between nocturia and cardiovascular disease (CVD) is frequently discussed in literature, yet the precise nature of this relationship remains poorly characterized. The existing literature was reviewed in order to address issues concerning the origin, diagnosis, management, and implications of the co-occurrence of CVD and nocturia. METHODS: This review summarizes literature and recommendations regarding the link between CVD and nocturia discussed during a think-tank meeting held at the 2023 International Consultation on Incontinence-Research Society. RESULTS: Cardiovascular disorders are often underestimated contributors to nocturia, with various potential mechanisms influencing nighttime urination, such as impact on fluid retention, atrial natriuretic peptide, and glomerular filtration rate. The redistribution of fluid from leg edema in supine position can lead nocturnal polyuria (NP). Additionally, sleep disturbances due to nocturia in itself may lead to CVD through an increase in blood pressure, insulin resistance, and inflammation. Disrupted circadian rhythms (e.g., in sleep pattern and urine production) were identified as critical factors in most etiologies of nocturia, and their contribution is deemed imperative in future research and treatment approaches, particularly in the aging population. NP can be detected through a simple bladder diary and can even be used to distinguish cardiac from noncardiac causes of nocturia. For the treatment of NP, desmopressin can be effective in select patients, however, caution and close monitoring is warranted for those with CVD due to increased risk of side effects. CONCLUSIONS: Gaps were identified in the available evidence and clear cut recommendations were put forth for future research. It is essential to gain a deeper understanding of the mechanisms linking nocturia and CVD to develop optimal management strategies.

Mimicking Transmural Helical Cardiomyofibre Orientation Using Bouligand-like Pore Structures in Ice-Templated Collagen Scaffolds.

The helical arrangement of cardiac muscle fibres underpins the contractile properties of the heart chamber. Across the heart wall, the helical angle of the aligned fibres changes gradually across the range of 90-180°. It is essential to recreate this structural hierarchy in vitro for developing functional artificial tissue. Ice templating can achieve single-oriented pore alignment via unidirectional ice solidification with a flat base mould design. We hypothesise that the orientation of aligned pores can be controlled simply via base topography, and we propose a scalable base design to recapitulate the transmural fibre orientation. We have utilised finite element simulations for rapid testing of base designs, followed by experimental confirmation of the Bouligand-like orientation. X-ray microtomography of experimental samples showed a gradual shift of 106 ± 10°, with the flexibility to tailor pore size and spatial helical angle distribution for personalised medicine.

A novel human iPSC model of COL4A1/A2 small vessel disease unveils a key pathogenic role of matrix metalloproteinases.

Cerebral small vessel disease (SVD) affects the small vessels in the brain and is a leading cause of stroke and dementia. Emerging evidence supports a role of the extracellular matrix (ECM), at the interface between blood and brain, in the progression of SVD pathology, but this remains poorly characterized. To address ECM role in SVD, we developed a co-culture model of mural and endothelial cells using human induced pluripotent stem cells from patients with COL4A1/A2 SVD-related mutations. This model revealed that these mutations induce apoptosis, migration defects, ECM remodeling, and transcriptome changes in mural cells. Importantly, these mural cell defects exert a detrimental effect on endothelial cell tight junctions through paracrine actions. COL4A1/A2 models also express high levels of matrix metalloproteinases (MMPs), and inhibiting MMP activity partially rescues the ECM abnormalities and mural cell phenotypic changes. These data provide a basis for targeting MMP as a therapeutic opportunity in SVD.