Acute respiratory distress syndrome (ARDS) is a devastating critical illness disproportionately affecting the elderly population, with both higher incidence and mortality. The integrity of the lung endothelial cell (EC) monolayer is critical for preservation of lung function. However, mechanisms mediating EC barrier regulation in the context of aging remain unclear. We assessed the severity of acute lung injury (ALI) in young (2 mo) and aged (18 mo) mice using a two-hit preclinical model. Compared with young cohorts, aged mice exhibited increased ALI severity, with greater vascular permeability characterized by elevated albumin influx and levels of bronchoalveolar lavage (BAL) cells (neutrophils) and protein. Aged/injured mice also demonstrated elevated levels of reactive oxygen species (ROS) in the BAL, which was associated with upregulation of the ROS-generating enzyme, Nox4. We evaluated the role of aging in human lung EC barrier regulation utilizing a cellular model of replicative senescence. Senescent EC populations were defined by increases in β-galactosidase activity and p16 levels. In response to lipopolysaccharide (LPS) challenge, senescent ECs demonstrate exacerbated permeability responses compared with control "young" ECs. LPS challenge led to a rapid induction of Nox4 expression in both control and senescent ECs, which was posttranslationally mediated via the proteasome/ubiquitin system. However, senescent ECs demonstrated deficient Nox4 ubiquitination, resulting in sustained expression of Nox4 and alterations in cellular redox homeostasis. Pharmacological inhibition of Nox4 in senescent ECs reduced LPS-induced alterations in permeability. These studies provide insight into the roles of Nox4/senescence in EC barrier responses and offer a mechanistic link to the increased incidence and mortality of ARDS associated with aging.
Sepsis remains the leading cause of death in the surgical intensive care unit. Prior studies have demonstrated a survival benefit of remote ischemic conditioning (RIC) in many disease states. The aim of this study was to determine the effects of RIC on survival in sepsis in an animal model and to assess alterations in inflammatory biochemical profiles. We hypothesized that RIC alters inflammatory biochemical profiles resulting in decreased mortality in a septic mouse model.
The evolution of the lungs and circulatory systems in vertebrates ensured the availability of molecular oxygen (O2; dioxygen) for aerobic cellular metabolism of internal organs in large animals. O2 serves as the physiologic terminal acceptor of mitochondrial electron transfer and of the NADPH oxidase (Nox) family of oxidoreductases to generate primarily water and reactive oxygen species (ROS), respectively.
Research in the area of cardiac tissue engineering is focused on the development of functional 3-dimensional cardiac muscle tissue in vitro, which includes bioengineered cardiac patches, pumps and ventricles. One of the major challenges in the field of cardiovascular tissue engineering is determining how to support the increased metabolic demands of 3-dimensional tissue constructs, due to the increase in both cellular mass and density compared to monolayer cultures. Traditional culture systems rely on passive diffusion for the delivery of oxygen and soluble factors. However, perfusion systems can provide continuous delivery of cell culture media to 3D tissue constructs, which promotes more active delivery of oxygen, soluble factors, and shear stress, which can be utilized to guide tissue maturation and functional remodeling of bioengineered tissues. We have previously described a perfusion system and demonstrated compatibility over short time periods (approximately hours) with 2-dimensional monolayer cell culture and 3-dimensional tissue constructs. The objectives of our current study were to: introduce CO2 buffering to stabilize media pH in order to achieve long term culture within the system, incorporate sensors capable of recording high media oxygen concentrations, and to increase the culture time of bioengineered heart muscle within the perfusion system in order to increase their functional performance. We showed that exposure of bioengineered heart muscle to perfusion for a period of 24 h increased their functional performance, as measured by cellular viability, total protein, total RNA, spontaneous contractility, twitch force, and specific force.