Biology subjects

Heise, R. L.

Publications and source records attributed to Heise, R. L..

8 recordsLinked to original sources

bioRxiv2023

Age-dependent ventilator-induced lung injury: Mathematical modeling, experimental data, and statistical analysis

A variety of pulmonary insults can result in the necessity for mechanical ventilation, which, when misused, used for prolonged periods of time, or associated with an excessive inflammatory response, can result in ventilator-induced lung injury. Older patients have been observed to have an increased risk for respiratory distress with ventilation and more recent studies suggest that this could be linked to disparities in the inflammatory response. To address this, we ventilated young (2-3 months) and old (20-25 months) mice for 2 hours using high pressure mechanical ventilation and extracted data for inflammatory cell ratios, namely macrophage phenotypes, and lung tissue integrity. A large difference in naive macrophages at baseline, alternatively-activated (M2) macrophages at baseline, and airspace enlargement after ventilation was observed in the old mice. The experimental data was used to fit a mathematical model for the inflammatory response to lung injury. Model variables include inflammatory markers and cells, namely neutrophils and macrophages, epithelial cells at varying states, and repair mediators. Parameter sampling was performed using an iterative sampling method and parameter sets were selected based on their ability to fit either the old or young macrophage phenotype percentages and epithelial variables at zero and two hours. Classification methods were performed to identify influential parameters separating the old and young parameter sets as well as user-defined health states. Parameters involved in repair and damage to epithelial cells and parameters regulating the pro-inflammatory response were shown to be important. Local sensitivity analysis preformed for the different epithelial cell variables produced similar results. A pseudo-intervention was also performed on the parameter sets. The results were most influential for the old parameter sets, specifically those with poorer lung health. These results indicate potential targets for therapeutic interventions prior to and during ventilation, particularly for old subjects. Author summaryA variety of inhaled pathogens and other pulmonary insults prompt the need for mechanical ventilation; a procedure that has become increasingly necessary following the 2019 coronavirus pandemic. A proportion of patients respond poorly to ventilation, some resulting in ventilator-induced lung injury. Observational data has shown increased instance of severe disease in older patients as well as differences in the inflammatory response to injury, although more research is needed to confirm this. We performed high-pressure ventilation on young (2-3 months) and old (20-25 months) mice and observed large disparities in inflammatory cell ratios at baseline and lung tissue integrity after ventilation. The experimental data was then used to fit a mathematical model of the inflammatory response to lung injury. We used a variety of analysis methods to identify important parameters separating the young and old parameter sets and user-defined health states of the resulting simulations. Parameters involved in damage and repair of epithelial cells in the lung as well as parameters controlling the pro-inflammatory response to injury were important in both classifying between old and young sets and determining predicted health after ventilation. These results indicate potential targets for therapeutic interventions prior to and during ventilation.

systems biology↗

bioRxiv2022

Agent-based vs. equation-based multi-scale modeling for macrophage polarization

Macrophages show high plasticity and result in heterogenic subpopulations or polarized states identified by specific cellular markers. These immune cells are typically characterized as pro-inflammatory, or classically activated M1, and anti-inflammatory, or alternatively activated M2. However, a more precise definition places them along a spectrum of activation where they may exhibit a number of pro- or anti-inflammatory roles. To gain a greater understanding of the mechanisms of the immune response from macrophages and the balance between M1 and M2 activation, we utilized two different modeling techniques, ordinary differential equation (ODE) modeling and agent-based modeling (ABM), to simulate the spectrum of macrophage activation to general pro- and anti-inflammatory stimuli on an individual and multi-cell level. The ODE model includes two hallmark pro- and anti-inflammatory signaling pathways and the ABM incorporates similar M1-M2 dynamics but in a spatio-temporal platform. Both models link molecular signaling with cellular-level dynamics. We then performed simulations with various initial conditions to replicate different experimental setups. Similar results were observed in both models after tuning to a common calibrating experiment. Comparing the two models results sheds light on the important features of each modeling approach. When more data is available these features can be considered when choosing techniques to best fit the needs of the modeler and application.

systems biology↗

bioRxiv2022

Mechanical Ventilation induced P21 in an Acute Aging Model of Lung Injury

Acute respiratory distress syndrome (ARDS) is a form of acute lung injury which leads to a paucity of oxygen. To remedy ARDS, patients are put on mechanical ventilators; however, the stretch resulting from the mechanical ventilator can lead to ventilator-induced lung injury or VILI. VILI is exacerbated by age. The combined effects of ARDS and mechanical ventilation can result in a hostile environment which may lead to senescence (stable cell cycle arrest). The role of senescence in VILI is poorly understood. Senescence is characterized by increased cyclin-dependent kinase inhibitors P16 and P21; however, P21 has been shown to occur in early senescence. We hypothesized that mechanical ventilation would lead to DNA damage and senescence-like phenotype. Both in vivo and in vitro models of VILI were used to investigate senescence and its mechanism in VILI. Mechanical ventilation increased senescence-associated markers such as DNA damage marker characterized by {gamma}H2AX, P21, senescence-associated secretory phenotype IL6, and decreased proliferation. Moreover, mechanical ventilation led to increased apoptosis. Lung sections were stained for KRT8 proteins, markers of transiently differentiated alveolar type 2 (AT2) cells which were reported to be more prone to DNA damage. Age and mechanical ventilation increased KRT8 positive cells. Finally, we probed a potential mediator of the stretch induced senescence in vitro by inhibiting P38-MAPK, which can be activated by DNA damage response, leading to increased P21. Inhibiting P38 decreased in P21 but did not decrease {gamma}H2AXThese findings suggest that mechanical ventilation may lead to a senescence-like phenotype involving the P38-MAPK pathway.

cell biology↗

bioRxiv2020

A Two-Step Bioreactor for Lung Recellularization

Bioreactors for reseeding of decellularized lung scaffolds have evolved with a wide variety of advancements. These include biomimetic mechanical stimulation, constant nutrient flow, multi-output monitoring, and large mammal scaling. Although dynamic bioreactors are not new to the field of bioengineered lungs, ideal conditions during cell seeding have not been extensively studied or controlled. To address the lack of cell dispersal in traditional seeding methods, we have designed a two-step bioreactor. The first step rotates a seeded lung every 20 minutes at different angles to ensure 20 percent of cells are anchored to a particular location based on the known rate of attachment. The second step involves perfusion culture to ensure nutrient dispersion and cellular growth. Compared to statically seeded lungs followed by conventional perfusion, rotationally seeded lungs followed by perfusion had significantly increased dsDNA content and more uniform cellular distribution. This new bioreactor system will aid in recellularizing the lung and other geometrically complex organs for tissue engineering.

bioengineering↗

bioRxiv2020

Understanding the Role of Macrophages in Lung Inflammation Through Mathematical Modeling

Respiratory infections, such as the novel coronavirus (SARS-COV-2) and other lung injuries, damage the pulmonary epithelium. In the most severe cases this leads to acute respiratory distress syndrome (ARDS). Due to respiratory failure associated with ARDS, the clinical intervention is the use of mechanical ventilation. Despite the benefits of mechanical ventilators, prolonged or misuse of these ventilators may lead to ventilation-associated/ventilation-induced lung injury (VILI). Damage caused to epithelial cells within the alveoli can lead to various types of complications and increased mortality rates. A key component of the immune response is recruitment of macrophages, immune cells that differentiate into phenotypes with unique pro- and/or anti-inflammatory roles based on the surrounding environment. An imbalance in pro- and anti-inflammatory responses can have deleterious effects on the individuals health. To gain a greater understanding of the mechanisms of the immune response to VILI and post-ventilation outcomes, we develop a mathematical model of interactions between the immune system and site of damage while accounting for macrophage polarization. Through Latin hypercube sampling we generate a virtual cohort of patients with biologically feasible dynamics. We use a variety of methods to analyze the results, including a random forest decision tree algorithm and parameter sensitivity with eFAST. Analysis shows that parameters and properties of transients related to epithelial repair and M1 activation and de-activation best predicted outcome. Using this new information, we hypothesize inter-ventions and use these treatment strategies to modulate damage in select virtual cases.

systems biology↗

bioRxiv2019

Laminin-driven Epac/Rap1 regulation of epithelial barriers on decellularized matrix

Decellularized tissues offer a unique tool for developing regenerative biomaterials or in vitro platforms for the study of cell-extracellular matrix (ECM) interactions. One main challenge associated with decellularized lung tissue is that ECM components can be stripped away or altered by the detergents used to remove cellular debris. Without characterizing the composition of lung decellularized ECM (dECM) and the cellular response caused by the altered composition, it is difficult to utilize dECM for regeneration and specifically, engineering the complexities of the alveolar-capillary barrier. This study takes steps towards uncovering if dECM must be enhanced with lost ECM proteins to achieve proper epithelial barrier formation. To achieve this, epithelial barrier function was assessed on dECM coatings with and without the systematic addition of several key basement membrane proteins. After comparing barrier function on collagen, fibronectin, laminin, and dECM in varying combinations as an in vitro coating, the alveolar epithelium exhibited superior barrier function when dECM was supplemented with laminin as evidenced by trans-epithelial electrical resistance (TEER) and permeability assays. Increased barrier resistance with laminin addition was associated with upregulation of Claudin-18, E- cadherin, and junction adhesion molecule (JAM)-A, and stabilization of zonula occludens (ZO)-1 at junction complexes. The Epac/Rap1 pathway was observed to play a role in the ECM-mediated barrier function determined by protein expression and Epac inhibition. These findings reveal potential ECM coatings and molecular therapeutic targets for improved regeneration with decellularized scaffolds or edema related pathologies.

bioinformatics↗

bioRxiv2019

Mechanochemical coupling and junctional forces during collective cell migration

Cell migration, a fundamental physiological process in which cells sense and move through their surrounding physical environment, plays a critical role in development and tissue formation, as well as pathological processes, such as cancer metastasis and wound healing. During cell migration, dynamics are governed by the bidirectional interplay between cell-generated mechanical forces and the activity of Rho GTPases, a family of small GTP-binding proteins that regulate actin cytoskeleton assembly and cellular contractility. These interactions are inherently more complex during the collective migration of mechanically coupled cells, due to the additional regulation of cell-cell junctional forces. In this study, we present a minimal modeling framework to simulate the interactions between mechanochemical signaling in individual cells and interactions with cell-cell junctional forces during collective cell migration. We find that migration of individual cells depends on the feedback between mechanical tension and Rho GTPase activity in a biphasic manner. During collective cell migration, waves of Rho GTPase activity mediate mechanical contraction/extension and thus synchronization throughout the tissue. Further, cell-cell junctional forces exhibit distinct spatial patterns during collective cell migration, with larger forces near the leading edge. Larger junctional force magnitudes are associated with faster collective cell migration and larger tissue size. Simulations of heterogeneous tissue migration exhibit a complex dependence on the properties of both leading and trailing cells. Computational predictions demonstrate that collective cell migration depends on both the emergent dynamics and interactions between cellular-level Rho GTPase activity and contractility, and multicellular-level junctional forces.

biophysics↗

bioRxiv2017

The Influence of Aging and Mechanical Stretch in Alveolar Epithelium ER Stress and Inflammation

Ventilator-Induced lung injury (VILI) is a form of acute lung injury that is initiated or exacerbated by mechanical ventilation. The aging lung is more susceptible to lung injury. Harmful mechanical stretch of the alveolar epithelium is a recognized mechanism of VILI, yet little is known about how mechanical stretch affects aged epithelial cells. An activated response known as Endoplasmic Reticulum (ER) Stress occurs at the cellular level, which is increased with aging. The disrupted ER function results in disruption in cellular homeostasis, apoptosis, and inflammation. We hypothesized that age and mechanical stretch increase proinflammatory gene expression that is mediated by ER stress. Type II alveolar epithelial cells (ATII) were harvested from C57Bl6/J mice 8 weeks (young) and 20 months (old) of age. The cells were cyclically mechanically stretched at 15% change in surface area for up to 24 hours. Prior to stretch, groups were administered 4-PBA or vehicle as a control. Mechanical stretch upregulated both ER stress and proinflammatory gene expression in ATIIs. Age-matched and mis-matched monocyte recruitment by ATII conditioned media was quantified. Administration of 4-PBA attenuated both the ER stress and proinflammatory increases from stretch and/or age and significantly reduced monocyte migration to ATII conditioned media. Age increases susceptibility to stretch-induced ER stress and downstream inflammation in a primary ATII epithelial cell model.

bioengineering↗