Biology subjects

Humphrey, J. D.

Publications and source records attributed to Humphrey, J. D..

At least 19 recordsLinked to original sources

bioRxiv2026

Blocking Compensatory Matrix Cross-Linking Accelerates ThoracicAortopathy in a Mouse Model of Marfan Syndrome

Mechanical homeostasis plays a central role in promoting and preserving optimal structure and function in the adult aorta. Although pathogenic variants can compromise homeostatic processes, it appears that intramural cells yet attempt to compensate for some genetically induced changes. In particular, lysyl oxidase is higher in the adult Marfan aorta compared with the age-matched control aorta. Here, we block lysyl oxidase in adult Fbn1C1041G/+ Marfan syndrome mice after stimulating aortic disease progression via induced hypertension. Whereas hypertension alone increases aortic dilatation, concurrent blocking of lysyl oxidase results in a dramatic increase in disease severity, driving an otherwise mild aortic phenotype in adult male Fbn1C1041G/+ Marfan mice to aneurysmal dilatations as well as dissection and rupture, with frequent premature death. Deposition and cross-linking of fibrillar collagens, among other extracellular matrix constituents, can represent a protective compensation against severe disease in the Marfan aorta. The present study emphasizes the need clinically to avoid compromising new collagen deposition and suggests that strategies to augment collagen cross-linking could be beneficial.

bioengineering↗

bioRxiv2026

Hydraulic fracturing-induced delamination and extravasation extends medial damage beyond the false lumen in aortic dissection

Aortic dissection is life-threatening due to continued loss of medial integrity that may culminate in secondary rupture within hours to days. While pre-existing defects or hemodynamic loads compound structural deterioration of the aorta, pathological progression from symptomatic dissection channel to lethal transmural tear is poorly understood. We examined the structure of referent and acutely dissected ascending aortas by microscopy. Elastic, collagen, and cellular components of non-dissected media were intricately interconnected. Medial damage in dissection lesions was traced from ingress to central to peripheral areas. Entry tears broke cleanly through successive laminae leading to cavernous false lumens in which medial structure was destroyed. Nearby laminae with widening between flanking elastic lamellae (termed minor delaminations) were filled with blood and showed severe medial damage. Farther laminae without delamination but containing red blood cells (termed blood extravasation) displayed moderate medial damage. More distant, non-delaminated laminae with accumulation of albumin but not red blood cells (termed plasma extravasation) exhibited mild medial damage. Varying medial hemorrhage with scattered sloughing of laminae was observed along the entire false lumen. We conclude that hydraulic fracturing of residual dissected media by pressurized blood via communications from the false lumen contributes to further structural weakening of the aortic wall.

pathology↗

bioRxiv2026

Increased medial collagen enhances aortic resilience against mural delamination from hydraulic fracturing

The aorta, normally resilient to hemodynamic stresses, becomes vulnerable to structural failure due to diverse conditions that weaken the wall. We injected fluid into excised specimens of human ascending aorta with pressure monitoring to quantify the impact of clinical and histological factors on mural damage. Two modes of medial injury emerged with distinct pressure tracings. Extravasation was characterized by diffuse infiltration of fluid with widespread damage of smooth muscle cells and collagen fibers but limited separation of elastic lamellae. By contrast, delamination was characterized by marked separation of elastic lamellae along a single plane with damage to cells and fibrillar matrix restricted to adjacent laminae. Aging, aortic dilatation, and family history associated with lower pressures causing delamination, whereas a diagnosis of hypertension associated with higher pressures suggesting resilience to dissection. Collagen fraction adjacent to delamination correlated with higher pressures as did decreased smooth muscle cell density and increased glycosaminoglycan fraction, although several clinical and histological variables were interrelated. Protein cross-linking strengthened and enzymatic digestion of collagen weakened the aortic wall, while acute cell lysis with detergent had no effect. We conclude that increased functional medial collagen has an adaptive protective role in aortic remodeling rather than signifying medial degeneration.

bioengineering↗

bioRxiv2026

Controlled intramural fluid injection to quantify propensity to thoracic aortic dissection

Dissection of the thoracic aorta includes delamination of medial lamellae and permeation of blood within the media. Quantifying how biaxial loading of a vulnerable wall and fluid mechanics interact to drive dissection remains a central challenge. Here we combine controlled distension-extension testing of intact porcine descending thoracic aortas with forced intramural fluid injection to investigate how axial stretch, injection rate, and needle gauge modulate the initiation and propagation of intramural delamination. Across experiments, injection pressure-volume curves exhibited nonlinear responses characterized by pressure peaks followed by stepwise pressure drops, suggesting progressive micro-delamination events within the medial lamellar networks. Increasing axial stretch significantly elevated peak injection pressure and promoted preferential axial propagation of the permeation / delamination front. Higher injection rates induced abrupt lamellar separation and larger dissected areas, whereas smaller needle gauges generated higher upstream pressures due to increased hydraulic resistance. Synchrotron imaging revealed the microstructural transition from intralamellar fluid permeation and wall swelling to the formation of a large fluid-filled delamination cavity. These results support a mechanistic framework in which the introduction of pressurized fluid within the aortic media behaves as a hydraulic fracture process in a layered poroelastic tissue, governed by balance across fluid pressurization, wall loading, and interlamellar strength. The findings provide quantitative insight into the biomechanical conditions that contribute to the initiation and propagation of aortic dissection.

bioengineering↗

bioRxiv2025

Mechanisms Driving Thoracic Aortic Aneurysm Stability

Thoracic aortic aneurysms (TAAs) arise from a combination of biological and mechanical factors. Current clinical guidelines use size and rate of expansion to stratify risk, but such metrics do not predict if an aneurysm will stabilize, grow, dissect, or rupture. Computational biomechanical models can provide insights into mechanisms of aneurysm behavior that would be difficult or impossible to capture in vivo. Here, we use a constrained mixture theory of growth and remodeling to simulate lesion progression while co-varying rate-dependent parameters that contribute to the natural history of aneurysm growth. This includes insults to the material structure and mechanosensitivity of the vessel. This framework successfully simulates clinically-relevant phenotypes, including cases where lesions with initially similar degrees of dilatation or rates of expansion diverge in behavior later in their progression. By capturing this spectrum of outcomes, our framework lays a foundation for more accurate, patient-specific risk prediction and future integration of machine learning tools to accelerate translation into clinical practice.

bioengineering↗

bioRxiv2025

A Cross-scale Causal Mapping Framework Pinpoints Macrophage Orchestrators of Balanced Arterial Development

Postnatal pulmonary arteries experience an abrupt surge in flow that demands tightly coordinated remodeling of vascular structure and mechanical compliance. However, the cellular programs orchestrating these multiscale adaptation remain poorly defined, partly due to the absence of analytical tools integrating gene-cell-tissue scales. Here, we present CausaLink, a cross-scale causal mapping framework that predicts how altered gene expression propagates through gene-cell-tissue networks by integrating time-course transcriptomic and tissue morpho-mechanical data. We constructed a single-cell transcriptomic atlas of 11,143 proximal pulmonary artery-derived cells from C57BL/6J mice across five developmental stages (P2, P10, P21, P42, and P84), revealing dynamic lineage transitions and transient mesenchymal population specifying into fibroblasts and smooth muscle cells from P2 to P21. Using this framework, we identified Mgl2 macrophages as central regulators promoting lumen expansion while preventing pathological wall thinning or thickening. To validate these predictions, we established a human induced pluripotent stem cell-derived arterial assembloid enriched in MGLhigh macrophages. In this model, MGLhigh macrophages supported lumen enlargement while maintaining overall wall thickness and induced formation of an adventitia-like fibroblast layer that recapitulated approximately 80% of the native adventitial fraction with balanced collagen-elastin remodeling. By linking predictive modeling to human organoid validation, this study establishes a cross-scale workflow for tracing how gene programs shape vascular architecture, offering mechanistic insights and a foundation for predictive regenerative medicine.

bioengineering↗

bioRxiv2025

Postnatal Pulmonary Artery Development from Transcript to Tissue

Many congenital conditions and surgical interventions perturb the hemodynamics experienced by proximal pulmonary arteries during early postnatal development, thus leading to differential gene expression and associated changes in vascular structure and function. Among these, pathologic conditions include patent ductus arteriosus, pulmonary atresia and stenosis, and hypoxemia-induced pulmonary hypertension while surgical interventions include the placement of a Blalock-Taussig shunt as well as Glenn, Fontan, and Norwood procedures. Despite the significant morbidity associated with these diverse conditions, there has been little attention directed towards understanding natural postnatal development of pulmonary arteries from both biological and mechanical perspectives. With-out such information, we cannot truly understand the phenotype of the affected pulmonary artery, which is fundamental to improving diagnosis, treatment, and prognosis. In this paper, we present novel data from wild-type mice that document normal postnatal changes in select gene expression, vascular wall composition, and biomechanical properties of proximal pulmonary arteries. These findings enabled the establishment of a novel, data-informed computational model of pulmonary artery development capable of simulating outcomes in response to perturbations in the pulmonary artery hemodynamic environment.

bioengineering↗

bioRxiv2024

Short-Term Disruption of TGFβ Signaling in Adult Mice Renders the Aorta Vulnerable to Hypertension-Induced Dissection

Hypertension and transient increases in blood pressure from extreme exertion are risk factors for aortic dissection in patients with age-related vascular degeneration or inherited connective tissue disorders. Yet, the common experimental model of angiotensin II-induced aortopathy in mice appears independent of high blood pressure as lesions do not occur in response to an alternative vasoconstrictor, norepinephrine, and are not prevented by co-treatment with a vasodilator, hydralazine. We investigated vasoconstrictor administration to adult mice 1 week after disruption of TGF{beta} signaling in smooth muscle cells. Norepinephrine increased blood pressure and induced aortic dissection by 7 days and even within 30 minutes that was rescued by hydralazine; results were similar with angiotensin II. Changes in regulatory contractile molecule expression were not of pathological significance. Rather, reduced synthesis of extracellular matrix yielded a vulnerable aortic phenotype by decreasing medial collagen, most dynamically type XVIII, and impairing cell-matrix adhesion. We conclude that transient and sustained increases in blood pressure cause dissection in aortas rendered vulnerable by inhibition of TGF{beta}-driven extracellular matrix production by smooth muscle cells. A corollary is that medial fibrosis, a frequent feature of medial degeneration, may afford some protection against aortic dissection.

pathology↗

bioRxiv2023

A fast, robust method for quantitative assessment of collagen fibril architecture from transmission electron micrographs

Collagen is the most abundant protein in mammals; it exhibits a hierarchical organization and provides structural support to a wide range of soft tissues, including blood vessels. The architecture of collagen fibrils dictates vascular stiffness and strength, and changes therein can contribute to disease progression. While transmission electron microscopy (TEM) is routinely used to examine collagen fibrils under normal and pathological conditions, computational tools that enable fast and minimally subjective quantitative assessment remain lacking. In the present study, we describe a novel semi-automated image processing and statistical modeling pipeline for segmenting individual collagen fibrils from TEM images and quantifying key metrics of interest, including fibril crosssectional area and aspect ratio. For validation, we show illustrative results for adventitial collagen in the thoracic aorta from three different mouse models.

bioengineering↗

bioRxiv2023

Ex Vivo Biomechanical Characterization of Umbilical Vessels: Possible Shunts in Congenital Heart Palliation

Children born with single ventricle defects undergo staged palliative surgeries to reconstruct the circulation to improve transport of deoxygenated blood to the lungs. As part of the first surgery, a temporary shunt (Blalock-Thomas-Taussig) is often created in neonates to connect a systemic and a pulmonary artery. Standard-of-care shunts are synthetic, which can lead to thrombosis, and much stiffer than the two host vessels, which can cause adverse mechanobiological responses. Moreover, the neonatal vasculature can undergo significant changes in size and structure over a short period, thus constraining the use of a non-growing synthetic shunt. Recent studies suggest that autologous umbilical vessels could serve as improved shunts, but there has not been a detailed biomechanical characterization of the four primary vessels - subclavian artery, pulmonary artery, umbilical vein, and umbilical artery. Herein, we biomechanically phenotype umbilical veins and arteries from prenatal mice (E18.5) and compare them to subclavian and pulmonary arteries harvested at two critical postnatal developmental ages (P10, P21). Comparisons include age-specific physiological conditions and simulated surgical-like shunt conditions. Results suggest that the intact umbilical vein is a better choice as a shunt than the umbilical artery due to concerns with lumen closure and constriction related-intramural damage in the latter. Yet, decellularization of umbilical arteries may be a viable alternative, with the possibility of host cellular infiltration and subsequent remodeling. Given recent efforts using autologous umbilical vessels as Blalock-Thomas-Taussig shunts in a clinical trial, our findings highlight aspects of the associated biomechanics that deserve further investigation.

bioengineering↗

bioRxiv2022

Fibronectin-integrin α5 signaling promotes thoracic aortic aneurysm in a mouse model of Marfan syndrome

BackgroundMarfan syndrome, caused by mutations in the gene for the extracellular matrix (ECM) glycoprotein fibrillin-1, leads to thoracic aortic aneurysms (TAAs). Phenotypic modulation of vascular smooth muscle cells (SMCs) and ECM remodeling are characteristics of both non-syndromic and Marfan aneurysms. The ECM protein fibronectin (FN) is elevated in the tunica media of TAAs and amplifies inflammatory signaling in endothelial and SMCs through its main receptor, integrin 5{beta}1. We investigated the role of integrin 5-specific signals in Marfan mice in which the cytoplasmic domain of integrin 5 was replaced with that of integrin 2 (denoted 5/2 chimera). MethodsWe used 5/2 chimera mouse crossed with Fbn1mgR/mgR genetic background (mgR, a mouse model of Marfan syndrome) to compare the survival rate and pathogenesis of TAAs among wild type, 5/2, mgR and 5/2; mgR mice. Further biochemical and microscopic analysis of porcine and mouse aortic SMCs allowed us to identify the molecular mechanisms by which FN affects SMCs and subsequent development of TAAs. ResultsFN was elevated in the thoracic aortas from Marfan patients, in non-syndromic aneurysms and in the mgR mouse model of Marfan syndrome. The 5/2 mutation greatly prolonged survival of Marfan mice, with improved elastic fiber integrity, mechanical properties, SMC density, and SMC contractile gene expression. Furthermore, in vitro, plating of wild-type, but not 5/2, SMCs on FN decreased contractile gene expression and activated inflammatory pathways. These effects correlated with increased NF-kB activation and immune cell infiltration in the mgR aortas, which was rescued in the 5/2 mgR aortas. ConclusionsFN-integrin 5 signaling is a significant driver of TAA in the mgR mouse model. This pathway warrants further investigation as a therapeutic target.

pathology↗

bioRxiv2022

Compensatory aortic remodeling in Marfan syndrome protects against sexually dimorphic rupture during a BAPN challenge

Transmural rupture of the aorta is responsible for significant morbidity and mortality; it occurs when wall stress exceeds local wall strength. Amongst other conditions, the aortic root and ascending aorta become vulnerable to dissection and rupture in Marfan syndrome, a connective tissue disorder that results in a progressive fragmentation and degradation of the elastic fibers of the aortic wall. Whereas competent elastic fibers are critical for aortic functionality, cross-linked collagen fibers endow the aorta with its stiffness and strength. In this paper, we contrast progressive degeneration of the ascending aorta in male and female Marfan and wild-type mice, with and without chronic exposure to a potent inhibitor of lysyl oxidase ({beta}-aminopropionitrile, or BAPN), to examine effects of extracellular matrix cross-linking in aortic dilatation and rupture. We found a strong sexual dimorphism in aortic dilatation in Marfan mice and aortic rupture in wild-type mice, but also a compensatory remodeling of the aorta that protected the Marfan aorta against lethal rupture despite a strong BAPN challenge. This compensation appears to be mediated via increased lysyl oxidase in the female and especially male Marfan aorta, resulting in improved collagen fiber stability and integrity, particularly of fibril bundles in the adventitia.

bioengineering↗

bioRxiv2021

Lonafarnib improves cardiovascular function and survival in a mouse model of Hutchinson-Gilford Progeria Syndrome

Clinical trials have demonstrated that lonafarnib, a farnesyltransferase inhibitor, extends lifespan in patients afflicted by Hutchinson-Gilford progeria syndrome, a devastating condition that accelerates many characteristics of aging and results in premature death due to cardiovascular sequelae. The US Food and Drug Administration approved Zokinvy (lonafarnib) in November 2020 for treating these patients, yet a detailed examination of drug-associated effects on cardiovascular structure, properties, and function has remained wanting. In this paper, we report encouraging outcomes of daily post-weaning treatment with lonafarnib on the composition and biomechanical phenotype of elastic and muscular arteries as well as associated cardiac function in a well-accepted mouse model of progeria that exhibits severe end-stage cardiovascular disease. Lonafarnib resulted in 100% survival of the treated progeria mice to the study end-point (time of 50% survival of untreated mice), with associated improvements in arterial structure and function working together to significantly reduce pulse wave velocity and improve left ventricular diastolic function. By contrast, dual treatment with lonafarnib and rapamycin did not improve outcomes over that achieved with lonafarnib monotherapy.

pathology↗

bioRxiv2021

Critical Pressure of Intramural Delamination in Aortic Dissection

Computational models of aortic dissection can examine mechanisms by which this potentially lethal condition develops and propagates. We present results from phase-field finite element simulations that are motivated by a classical but seldom repeated experiment. Initial simulations agreed qualitatively and quantitatively with data, yet because of the complexity of the problem it was difficult to discern trends. Simplified analytical models were used to gain further insight. Together, simplified and phase-field models reveal power-law-based relationships between the pressure that initiates an intramural tear and key geometric and mechanical factors - insult surface area, wall stiffness, and tearing energy. The degree of axial stretch and luminal pressure similarly influence the pressure of tearing, which was [~]88 kPa for healthy and diseased human aortas having sub-millimeter-sized initial insults, but lower for larger tear sizes. Finally, simulations show that the direction a tear propagates is influenced by focal regions of weakening or strengthening, which can drive the tear towards the lumen (dissection) or adventitia (rupture). Additional data on human aortas having different predisposing disease conditions will be needed to extend these results further, but the present findings show that physiologic pressures can propagate initial medial defects into delaminations that can serve as precursors to dissection.

bioengineering↗

bioRxiv2021

Uncertainty quantification in subject-specific estimation of local vessel mechanical properties

Quantitative estimation of local mechanical properties remains critically important in the ongoing effort to elucidate how blood vessels establish, maintain, or lose mechanical homeostasis. Recent advances based on panoramic digital image correlation (pDIC) have made high-fidelity 3D reconstructions of small-animal (e.g., murine) vessels possible when imaged in a variety of quasi-statically loaded configurations. While we have previously developed and validated inverse modeling approaches to translate pDIC-measured surface deformations into biomechanical metrics of interest, our workflow did not heretofore include a methodology to quantify uncertainties associated with local point estimates of mechanical properties. This limitation has compromised our ability to infer biomechanical properties on a subject-specific basis, such as whether stiffness differs significantly between multiple material locations on the same vessel or whether stiffness differs significantly between multiple vessels at a corresponding material location. In the present study, we have integrated a novel uncertainty quantification and propagation pipeline within our inverse modeling approach, relying on empirical and analytic Bayesian techniques. To demonstrate the approach, we present illustrative results for the ascending thoracic aorta from three mouse models, quantifying uncertainties in constitutive model parameters as well as circumferential and axial tangent stiffness. Our extended workflow not only allows parameter uncertainties to be systematically reported, but also facilitates both subject-specific and group-level statistical analyses of the mechanics of the vessel wall.

bioengineering↗

bioRxiv2020

Vascular dimorphism ensured by regulated proteoglycan dynamics favors rapid umbilical artery closure at birth

The umbilical artery lumen occludes rapidly at birth, preventing blood loss, whereas the umbilical vein remains patent, providing the newborn with a placental infusion. Here, we identify differential arterial-venous proteoglycan dynamics as a determinant of these contrasting vascular responses. We show that the umbilical artery, unlike the vein, has an inner layer enriched in the hydrated proteoglycan aggrecan, external to which lie contraction-primed smooth muscle cells (SMC). At birth, SMC contraction drives inner layer buckling and centripetal displacement to occlude the arterial lumen, a mechanism elicited by biomechanical and computational analysis. Vascular dimorphism arises from spatially regulated proteoglycan expression and breakdown in umbilical vessels. Mice lacking aggrecan or the metalloprotease ADAMTS1, which degrades proteoglycans, demonstrated their opposing roles in umbilical cord arterial-venous dimorphism and contrasting effects on SMC differentiation. Umbilical vessel dimorphism is conserved in mammals, suggesting that their differential proteoglycan dynamics were a positive selection step in mammalian evolution.Competing Interest StatementThe authors have declared no competing interest.View Full Text

developmental biology↗

bioRxiv2020

Fast, Rate-Independent, Finite Element Implementation of a 3D Constrained Mixture Model of Soft Tissue Growth and Remodeling

Constrained mixture models of soft tissue growth and remodeling can simulate many evolving conditions in health as well as in disease and its treatment, but they can be computationally expensive. In this paper, we derive a new fast, robust finite element implementation based on a concept of mechanobiological equilibrium that yields fully resolved solutions and allows computation of quasi-equilibrated evolutions when imposed perturbations are slow relative to the adaptive process. We demonstrate quadratic convergence and verify the model via comparisons with semi-analytical solutions for arterial mechanics. We further examine the enlargement of aortic aneurysms for which we identify new mechanobiological insights into factors that affect the nearby non-aneurysmal segment as it responds to the changing mechanics within the diseased segment. Because this new 3D approach can be implemented within many existing finite element solvers, constrained mixture models of growth and remodeling can now be used more widely.

bioengineering↗

bioRxiv2019

Paradoxical Aortic Stiffening and Subsequent Cardiac Dysfunction in Hutchinson-Gilford Progeria Syndrome

Hutchinson-Gilford Progeria Syndrome (HGPS) is an ultra-rare disorder with devastating sequelae resulting in early death, presently believed to stem primarily from heart failure secondary to central arterial stiffening. We analyze novel longitudinal cardiovascular data from a mouse model of HGPS (LmnaG609G/G609G) using allometric scaling and advanced computational modelling and show that a late-stage increase in pulse wave velocity, with associated diastolic dysfunction but preserved systolic function, emerges with a loss of aortic function, independent of sex. Specifically, there is a dramatic late-stage loss of smooth muscle function and cells and an excessive accumulation of proteoglycans along the entire aorta, which result in a loss of biomechanical function (contractility and elastic energy storage) and marked structural stiffening despite a distinctly low intrinsic material stiffness that is consistent with the lack of functional lamin A. Importantly, vascular function appears to be normal within the low stress environment of development, only to succumb progressively to pressure-related effects of the lamin A mutation and become extreme in the peri-morbid period. Because the dramatic life-threatening aortic phenotype manifests during the last quarter of life there may be a therapeutic window in maturity that could alleviate concerns with therapies administered during early periods of arterial development.\n\nDisclosuresD.T.B is an equity holder in, and receives research and consulting support from, Inozyme Pharma, Inc. for therapeutics for ENPP1 deficiency. None of the other authors declare any conflict, financial or otherwise.

bioengineering↗