All Publications

  • Fluid-structure interaction modeling of blood flow in the pulmonary arteries using the unified continuum and variational multiscale formulation (Rerpinted from vol 107, 103556, 2020) MECHANICS RESEARCH COMMUNICATIONS Liu, J., Yang, W., Lan, I. S., Marsden, A. L. 2021; 112
  • Transcriptomic and Functional Analyses of Mitochondrial Dysfunction in Pressure Overload-Induced Right Ventricular Failure. Journal of the American Heart Association Hwang, H. V., Sandeep, N., Nair, R. V., Hu, D., Zhao, M., Lan, I. S., Fajardo, G., Matkovich, S. J., Bernstein, D., Reddy, S. 2021: e017835


    Background In complex congenital heart disease patients such as those with tetralogy of Fallot, the right ventricle (RV) is subject to pressure overload, leading to RV hypertrophy and eventually RV failure. The mechanisms that promote the transition from stable RV hypertrophy to RV failure are unknown. We evaluated the role of mitochondrial bioenergetics in the development of RV failure. Methods and Results We created a murine model of RV pressure overload by pulmonary artery banding and compared with sham-operated controls. Gene expression by RNA-sequencing, oxidative stress, mitochondrial respiration, dynamics, and structure were assessed in pressure overload-induced RV failure. RV failure was characterized by decreased expression of electron transport chain genes and mitochondrial antioxidant genes (aldehyde dehydrogenase 2 and superoxide dismutase 2) and increased expression of oxidant stress markers (heme oxygenase, 4-hydroxynonenal). The activities of all electron transport chain complexes decreased with RV hypertrophy and further with RV failure (oxidative phosphorylation: sham 552.3±43.07 versus RV hypertrophy 334.3±30.65 versus RV failure 165.4±36.72pmol/(s*mL), P<0.0001). Mitochondrial fission protein DRP1 (dynamin 1-like) trended toward an increase, while MFF (mitochondrial fission factor) decreased and fusion protein OPA1 (mitochondrial dynamin like GTPase) decreased. In contrast, transcription of electron transport chain genes increased in the left ventricle of RV failure. Conclusions Pressure overload-induced RV failure is characterized by decreased transcription and activity of electron transport chain complexes and increased oxidative stress which are associated with decreased energy generation. An improved understanding of the complex processes of energy generation could aid in developing novel therapies to mitigate mitochondrial dysfunction and delay the onset of RV failure.

    View details for DOI 10.1161/JAHA.120.017835

    View details for PubMedID 33522250

  • Mathematical modeling of the vascular system Notices of the American Mathematical Society Liu, J., Lan, I. S., Marsden, A. L. 2021; 68 (5): 707-720

    View details for DOI 10.1090/noti2278

  • A note on the accuracy of the generalized-alpha scheme for the incompressible Navier-Stokes equations INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Liu, J., Lan, I. S., Tikenogullari, O. Z., Marsden, A. L. 2020

    View details for DOI 10.1002/nme.6550

    View details for Web of Science ID 000576764000001

  • 4HNE Impairs Myocardial Bioenergetics in Congenital Heart DiseaseInduced Right Ventricular Failure. Circulation Hwang, H. V., Sandeep, N., Paige, S. L., Ranjbarvaziri, S., Hu, D., Zhao, M., Lan, I. S., Coronado, M., Kooiker, K. B., Wu, S. M., Fajardo, G., Bernstein, D., Reddy, S. 2020


    Background: In patients with complex congenital heart disease, such as those with tetralogy of Fallot, the right ventricle (RV) is subject to pressure overload stress, leading to RV hypertrophy and eventually RV failure. The role of lipid peroxidation, a potent form of oxidative stress, in mediating RV hypertrophy and failure in congenital heart disease is unknown. Methods: Lipid peroxidation and mitochondrial function and structure were assessed in RV myocardium collected from patients with RV hypertrophy with normal RV systolic function (RV FAC 47.3±3.8%) and in patients with RV failure showing decreased RV systolic function (RV FAC 26.6±3.1%). The mechanism of the effect of lipid peroxidation, mediated by 4-hydroxynonenal (4HNE; a byproduct of lipid peroxidation) on mitochondrial function and structure was assessed in HL1 murine cardiomyocytes and human induced pluripotent stem cellderived cardiomyocytes. Results: RV failure was characterized by an increase in 4HNE adduction of metabolic and mitochondrial proteins (16/27 identified proteins), in particular electron transport chain proteins. Sarcomeric (myosin) and cytoskeletal proteins (desmin, tubulin) also underwent 4HNEadduction. RV failure showed lower oxidative phosphorylation [moderate RV hypertrophy 287.6±19.75 vs. RV failure 137.8±11.57 pmol/(sec*ml), p=0.0004], and mitochondrial structural damage. Using a cell model, we show that 4HNE decreases cell number and oxidative phosphorylation (control 388.1±23.54 vs. 4HNE 143.7±11.64 pmol/(sec*ml), p<0.0001). Carvedilol, a known antioxidant did not decrease 4HNE adduction of metabolic and mitochondrial proteins and did not improve oxidative phosphorylation. Conclusions: Metabolic, mitochondrial, sarcomeric and cytoskeletal proteins are susceptible to 4HNE-adduction in patients with RV failure. 4HNE decreases mitochondrial oxygen consumption by inhibiting electron transport chain complexes. Carvedilol did not improve the 4HNE-mediated decrease in oxygen consumption. Strategies to decrease lipid peroxidation could improve mitochondrial energy generation and cardiomyocyte survival and improve RV failure in patients with congenital heart disease.

    View details for DOI 10.1161/CIRCULATIONAHA.120.045470

    View details for PubMedID 32806952

  • Fluid-structure interaction modeling of blood flow in the pulmonary arteries using the unified continuum and variational multiscale formulation. Mechanics research communications Liu, J., Yang, W., Lan, I. S., Marsden, A. L. 2020; 107


    In this work, we present a computational fluid-structure interaction (FSI) study for a healthy patient-specific pulmonary arterial tree using the unified continuum and variational multiscale (VMS) formulation we previously developed. The unified framework is particularly well-suited for FSI, as the fluid and solid sub-problems are addressed in essentially the same manner and can thus be uniformly integrated in time with the generalized-alpha method. In addition, the VMS formulation provides a mechanism for large-eddy simulation in the fluid sub-problem and pressure stabilization in the solid sub-problem. The FSI problem is solved in a quasi-direct approach, in which the pressure and velocity in the unified continuum body are first solved, and the solid displacement is then obtained via a segregated algorithm and prescribed as a boundary condition for the mesh motion. Results of the pulmonary arterial FSI simulation are presented and compared against those of a rigid wall simulation.

    View details for DOI 10.1016/j.mechrescom.2020.103556

    View details for PubMedID 32773906

  • Changes in event-related potential functional networks predict traumatic brain injury in piglets CLINICAL BIOMECHANICS Atlan, L. S., Lan, I. S., Smith, C., Margulies, S. S. 2019; 64: 14–21


    Traumatic brain injury is a leading cause of cognitive and behavioral deficits in children in the US each year. None of the current diagnostic tools, such as quantitative cognitive and balance tests, have been validated to identify mild traumatic brain injury in infants, adults and animals. In this preliminary study, we report a novel, quantitative tool that has the potential to quickly and reliably diagnose traumatic brain injury and which can track the state of the brain during recovery across multiple ages and species.Using 32 scalp electrodes, we recorded involuntary auditory event-related potentials from 22 awake four-week-old piglets one day before and one, four, and seven days after two different injury types (diffuse and focal) or sham. From these recordings, we generated event-related potential functional networks and assessed whether the patterns of the observed changes in these networks could distinguish brain-injured piglets from non-injured.Piglet brains exhibited significant changes after injury, as evaluated by five network metrics. The injury prediction algorithm developed from our analysis of the changes in the event-related potentials functional networks ultimately produced a tool with 82% predictive accuracy.This novel approach is the first application of auditory event-related potential functional networks to the prediction of traumatic brain injury. The resulting tool is a robust, objective and predictive method that offers promise for detecting mild traumatic brain injury, in particular because collecting event-related potentials data is noninvasive and inexpensive.

    View details for DOI 10.1016/j.clinbiomech.2018.05.013

    View details for Web of Science ID 000468249700003

    View details for PubMedID 29933967

    View details for PubMedCentralID PMC6274597

  • Infant skull fracture risk for low height falls. International journal of legal medicine Hajiaghamemar, M. n., Lan, I. S., Christian, C. W., Coats, B. n., Margulies, S. S. 2019; 133 (3): 847–62


    Skull fractures are common injuries in young children, typically caused by accidental falls and child abuse. The paucity of detailed biomechanical data from real-world trauma in children has hampered development of biomechanical thresholds for skull fracture in infants. The objectives of this study were to identify biomechanical metrics to predict skull fracture, determine threshold values associated with fracture, and develop skull fracture risk curves for low-height falls in infants. To achieve these objectives, we utilized an integrated approach consisting of case evaluation, anthropomorphic reconstruction, and finite element simulation. Four biomechanical candidates for predicting skull fracture were identified (first principal stress, first principal strain, shear stress, and von Mises stress) and evaluated against well-witnessed falls in infants (0-6 months). Among the predictor candidates, first principal stress and strain correlated best with the occurrence of parietal skull fracture. The principal stress and strain thresholds associated with 50 and 95% probability of parietal skull fracture were 25.229 and 36.015 MPa and 0.0464 and 0.0699, respectively. Risk curves using these predictors determined that infant falls from 0.3 m had a low probability (0-54%) to result in parietal skull fracture, particularly with carpet impact (0-1%). Head-first falls from 0.9 m had a high probability of fracture (86-100%) for concrete impact and a moderate probability (34-81%) for carpet impact. Probabilities of fracture in 0.6 m falls were dependent on impact surface. Occipital impacts from 0.9 m onto the concrete also had the potential (27-90% probability) to generate parietal skull fracture. These data represent a multi-faceted biomechanical assessment of infant skull fracture risk and can assist in the differential diagnosis for head trauma in children.

    View details for PubMedID 30194647