Current and Future Engineering Strategies for ECMO Therapy.

Extracorporeal membrane oxygenation (ECMO) is a last resort therapy for patients with respiratory failure where the gas exchange capacity of the lung is compromised. Venous blood is pumped through an oxygenation unit outside of the body where oxygen diffusion into the blood takes place in parallel to carbon dioxide removal. ECMO is an expensive therapy which requires special expertise to perform. Since its inception, ECMO technologies have been evolving to improve its success and minimize the complications associated with it. These approaches aim for a more compatible circuit design capable of maximum gas exchange with minimal need for anticoagulants. This chapter summarizes the basic principles of ECMO therapy with the latest advancements and experimental strategies aiming for more efficient future designs.

Integrin α10ß1-selected mesenchymal stem cells reduced hypercoagulopathy in a porcine model of acute respiratory distress syndrome.

Mesenchymal stem cells (MSCs) have been studied for their potential benefits in treating acute respiratory distress syndrome (ARDS) and have reported mild effects when trialed within human clinical trials. MSCs have been investigated in preclinical models with efficacy when administered at the time of lung injury. Human integrin α10ß1-selected adipose tissue-derived MSCs (integrin α10ß1-MSCs) have shown immunomodulatory and regenerative effects in various disease models. We hypothesized that integrin α10ß1 selected-MSCs can be used to treat a sepsis-induced ARDS in a porcine model when administering cells after established injury rather than simultaneously. This was hypothesized to reflect a clinical picture of treatment with MSCs in human ARDS. 12 pigs were randomized to the treated or placebo-controlled group prior to the induction of mild to moderate ARDS via lipopolysaccharide administration. The treated group received 5 × 106 cells/kg integrin α10ß1-selected MSCs and both groups were followed for 12 h. ARDS was confirmed with blood gases and retrospectively with histological changes. After intervention, the treated group showed decreased need for inotropic support, fewer signs of histopathological lung injury including less alveolar wall thickening and reduction of the hypercoagulative disease state. The MSC treatment was not associated with adverse events over the monitoring period. This provides new opportunities to investigate integrin α10ß1-selected MSCs as a treatment for a disease which does not yet have any definitive therapeutic options.

A Semi-quantitative Scoring System for Green Histopathological Evaluation of Large Animal Models of Acute Lung Injury.

Acute respiratory distress syndrome (ARDS) is a life-threatening, high mortality pulmonary condition characterized by acute lung injury (ALI) resulting in diffuse alveolar damage. Despite progress regarding the understanding of ARDS pathophysiology, there are presently no effective pharmacotherapies. Due to the complexity and multiorgan involvement typically associated with ARDS, animal models remain the most commonly used research tool for investigating potential new therapies. Experimental models of ALI/ARDS use different methods of injury to acutely induce lung damage in both small and large animals. These models have historically played an important role in the development of new clinical interventions, such as fluid therapy and the use of supportive mechanical ventilation (MV). However, failures in recent clinical trials have highlighted the potential inadequacy of small animal models due to major anatomical and physiological differences, as well as technical challenges associated with the use of clinical co-interventions [e.g., MV and extracorporeal membrane oxygenation (ECMO)]. Thus, there is a need for larger animal models of ALI/ARDS, to allow the incorporation of clinically relevant measurements and co-interventions, hopefully leading to improved rates of clinical translation. However, one of the main challenges in using large animal models of preclinical research is that fewer species-specific experimental tools and metrics are available for evaluating the extent of lung injury, as compared to rodent models. One of the most relevant indicators of ALI in all animal models is evidence of histological tissue damage, and while histological scoring systems exist for small animal models, these cannot frequently be readily applied to large animal models. Histological injury in these models differs due to the type and severity of the injury being modeled. Additionally, the incorporation of other clinical support devices such as MV and ECMO in large animal models can lead to further lung damage and appearance of features absent in the small animal models. Therefore, semi-quantitative histological scoring systems designed to evaluate tissue-level injury in large animal models of ALI/ARDS are needed. Here we describe a semi-quantitative scoring system to evaluate histological injury using a previously established porcine model of ALI via intratracheal and intravascular lipopolysaccharide (LPS) administration. Additionally, and owing to the higher number of samples generated from large animal models, we worked to implement a more sustainable and greener histopathological workflow throughout the entire process.

Monitoring lung injury with particle flow rate in LPS- and COVID-19-induced ARDS.

In severe acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO) is a life-prolonging treatment, especially among COVID-19 patients. Evaluation of lung injury progression is challenging with current techniques. Diagnostic imaging or invasive diagnostics are risky given the difficulties of intra-hospital transportation, contraindication of biopsies, and the potential for the spread of infections, such as in COVID-19 patients. We have recently shown that particle flow rate (PFR) from exhaled breath could be a noninvasive, early detection method for ARDS during mechanical ventilation. We hypothesized that PFR could also measure the progress of lung injury during ECMO treatment. Lipopolysaccharide (LPS) was thus used to induce ARDS in pigs under mechanical ventilation. Eight were connected to ECMO, whereas seven animals were not. In addition, six animals received sham treatment with saline. Four human patients with ECMO and ARDS were also monitored. In the pigs, as lung injury ensued, the PFR dramatically increased and a particular spike followed the establishment of ECMO in the LPS-treated animals. PFR remained elevated in all animals with no signs of lung recovery. In the human patients, in the two that recovered, PFR decreased. In the two whose lung function deteriorated while on ECMO, there was increased PFR with no sign of recovery in lung function. The present results indicate that real-time monitoring of PFR may be a new, complementary approach in the clinic for measurement of the extent of lung injury and recovery over time in ECMO patients with ARDS.

Toxicological effects of zinc oxide nanoparticle exposure: an in vitro comparison between dry aerosol air-liquid interface and submerged exposure systems.

Engineered nanomaterials (ENMs) are increasingly produced and used today, but health risks due to their occupational airborne exposure are incompletely understood. Traditionally, nanoparticle (NP) toxicity is tested by introducing NPs to cells through suspension in the growth media, but this does not mimic respiratory exposures. Different methods to introduce aerosolized NPs to cells cultured at the air-liquid-interface (ALI) have been developed, but require specialized equipment and are associated with higher cost and time. Therefore, it is important to determine whether aerosolized setups induce different cellular responses to NPs than traditional ones, which could provide new insights into toxicological responses of NP exposure. This study evaluates the response of human alveolar epithelial cells (A549) to zinc oxide (ZnO) NPs after dry aerosol exposure in the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) system as compared to conventional, suspension-based exposure: cells at ALI or submerged. Similar to other studies using nebulization of ZnO NPs, we found that dry aerosol exposure of ZnO NPs via the NACIVT system induced different cellular responses as compared to conventional methods. ZnO NPs delivered at 1.0 µg/cm2 in the NACIVT system, mimicking occupational exposure, induced significant increases in metabolic activity and release of the cytokines IL-8 and MCP-1, but no differences were observed using traditional exposures. While factors associated with the method of exposure, such as differing NP aggregation, may contribute toward the different cellular responses observed, our results further encourage the use of more physiologically realistic exposure systems for evaluating airborne ENM toxicity.

Extracellular-Matrix-Reinforced Bioinks for 3D Bioprinting Human Tissue.

Recent advances in 3D bioprinting allow for generating intricate structures with dimensions relevant for human tissue, but suitable bioinks for producing translationally relevant tissue with complex geometries remain unidentified. Here, a tissue-specific hybrid bioink is described, composed of a natural polymer, alginate, reinforced with extracellular matrix derived from decellularized tissue (rECM). rECM has rheological and gelation properties beneficial for 3D bioprinting while retaining biologically inductive properties supporting tissue maturation ex vivo and in vivo. These bioinks are shear thinning, resist cell sedimentation, improve viability of multiple cell types, and enhance mechanical stability in hydrogels derived from them. 3D printed constructs generated from rECM bioinks suppress the foreign body response, are pro-angiogenic and support recipient-derived de novo blood vessel formation across the entire graft thickness in a murine model of transplant immunosuppression. Their proof-of-principle for generating human tissue is demonstrated by 3D bioprinting human airways composed of regionally specified primary human airway epithelial progenitor and smooth muscle cells. Airway lumens remained patent with viable cells for one month in vitro with evidence of differentiation into mature epithelial cell types found in native human airways. rECM bioinks are a promising new approach for generating functional human tissue using 3D bioprinting.

Clickable decellularized extracellular matrix as a new tool for building hybrid-hydrogels to model chronic fibrotic diseases in vitro.

Fibrotic disorders account for over one third of mortalities worldwide. Despite great efforts to study the cellular and molecular processes underlying fibrosis, there are currently few effective therapies. Dual-stage polymerization reactions are an innovative tool for recreating heterogeneous increases in extracellular matrix (ECM) modulus, a hallmark of fibrotic diseases in vivo. Here, we present a clickable decellularized ECM (dECM) crosslinker incorporated into a dynamically responsive poly(ethylene glycol)-α-methacrylate (PEGαMA) hybrid-hydrogel to recreate ECM remodeling in vitro. An off-stoichiometry thiol-ene Michael addition between PEGαMA (8-arm, 10 kg mol-1) and the clickable dECM resulted in hydrogels with an elastic modulus of E = 3.6 ± 0.24 kPa, approximating healthy lung tissue (1-5 kPa). Next, residual αMA groups were reacted via a photo-initiated homopolymerization to increase modulus values to fibrotic levels (E = 13.4 ± 0.82 kPa) in situ. Hydrogels with increased elastic moduli, mimicking fibrotic ECM, induced a significant increase in the expression of myofibroblast transgenes. The proportion of primary fibroblasts from dual-reporter mouse lungs expressing collagen 1a1 and alpha-smooth muscle actin increased by approximately 60% when cultured on stiff and dynamically stiffened hybrid-hydrogels compared to soft. Likewise, fibroblasts expressed significantly increased levels of the collagen 1a1 transgene on stiff regions of spatially patterned hybrid-hydrogels compared to the soft areas. Collectively, these results indicate that hybrid-hydrogels are a new tool that can be implemented to spatiotemporally induce a phenotypic transition in primary murine fibroblasts in vitro.

Increased particle flow rate from airways precedes clinical signs of ARDS in a porcine model of LPS-induced acute lung injury.

Acute respiratory distress syndrome (ARDS) is a common cause of death in the intensive care unit, with mortality rates of ~30-40%. To reduce invasive diagnostics such as bronchoalveolar lavage and time-consuming in-hospital transports for imaging diagnostics, we hypothesized that particle flow rate (PFR) pattern from the airways could be an early detection method and contribute to improving diagnostics and optimizing personalized therapies. Porcine models were ventilated mechanically. Lipopolysaccharide (LPS) was administered endotracheally and in the pulmonary artery to induce ARDS. PFR was measured using a customized particles in exhaled air (PExA 2.0) device. In contrast to control animals undergoing mechanical ventilation and receiving saline administration, animals who received LPS developed ARDS according to clinical guidelines and histologic assessment. Plasma levels of TNF-α and IL-6 increased significantly compared with baseline after 120 and 180 min, respectively. On the other hand, the PFR significantly increased and peaked 60 min after LPS administration, i.e., ~30 min before any ARDS stage was observed with other well-established outcome measurements such as hypoxemia, increased inspiratory pressure, and lower tidal volumes or plasma cytokine levels. The present results imply that PFR could be used to detect early biomarkers or as a clinical indicator for the onset of ARDS.

Organ-restricted vascular delivery of nanoparticles for lung cancer therapy.

Nanoparticle-based targeted drug delivery holds promise for treatment of cancers. However, most approaches fail to be translated into clinical success due to ineffective tumor targeting in vivo. Here, the delivery potential of mesoporous silica nanoparticles (MSN) functionalized with targeting ligands for EGFR and CCR2 is explored in lung tumors. The addition of active targeting ligands on MSNs enhances their uptake in vitro but fails to promote specific delivery to tumors in vivo, when administered systemically via the blood or locally to the lung into immunocompetent murine lung cancer models. Ineffective tumor targeting is due to efficient clearance of the MSNs by the phagocytic cells of the liver, spleen, and lung. These limitations, however, are successfully overcome using a novel organ-restricted vascular delivery (ORVD) approach. ORVD in isolated and perfused mouse lungs of Kras-mutant mice enables effective nanoparticle extravasation from the tumor vasculature into the core of solid lung tumors. In this study, ORVD promotes tumor cell-specific uptake of nanoparticles at cellular resolution independent of their functionalization with targeting ligands. Organ-restricted vascular delivery thus opens new avenues for optimized nanoparticles for lung cancer therapy and may have broad applications for other vascularized tumor types.

Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases 2017. An Official American Thoracic Society Workshop Report.

The University of Vermont Larner College of Medicine, in collaboration with the National Heart, Lung, and Blood Institute (NHLBI), the Alpha-1 Foundation, the American Thoracic Society, the Cystic Fibrosis Foundation, the European Respiratory Society, the International Society for Cell & Gene Therapy, and the Pulmonary Fibrosis Foundation, convened a workshop titled "Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases" from July 24 through 27, 2017, at the University of Vermont, Burlington, Vermont. The conference objectives were to review and discuss current understanding of the following topics: 1) stem and progenitor cell biology and the role that they play in endogenous repair or as cell therapies after lung injury, 2) the emerging role of extracellular vesicles as potential therapies, 3) ex vivo bioengineering of lung and airway tissue, and 4) progress in induced pluripotent stem cell protocols for deriving lung cell types and applications in disease modeling. All of these topics are research areas in which significant and exciting progress has been made over the past few years. In addition, issues surrounding the ethics and regulation of cell therapies worldwide were discussed, with a special emphasis on combating the growing problem of unproven cell interventions being administered to patients with lung diseases. Finally, future research directions were discussed, and opportunities for both basic and translational research were identified.

The Preparation of Decellularized Mouse Lung Matrix Scaffolds for Analysis of Lung Regenerative Cell Potential.

Lung transplantation is the only option for patients with end-stage lung disease, but there is a shortage of available lung donors. Furthermore, efficiency of lung transplantation has been limited due to primary graft dysfunction. Recent mouse models mimicking lung disease in humans have allowed for deepening our understanding of disease pathomechanisms. Moreover, new techniques such as decellularization and recellularization have opened up new possibilities to contribute to our understanding of the regenerative mechanisms involved in the lung. Stripping the lung of its native cells allows for unprecedented analyses of extracellular matrix and sets a physiologic platform to study the regenerative potential of seeded cells. A comprehensive understanding of the molecular pathways involved for lung development and regeneration in mouse models can be translated to regeneration strategies in higher organisms, including humans. Here we describe and discuss several techniques used for murine lung de- and recellularization, methods for evaluation of efficacy including histology, protein/RNA isolation at the whole lung, as well as lung slices level.

How to build a lung: latest advances and emerging themes in lung bioengineering.

Chronic respiratory diseases remain a major cause of morbidity and mortality worldwide. The only option at end-stage disease is lung transplantation, but there are not enough donor lungs to meet clinical demand. Alternative options to increase tissue availability for lung transplantation are urgently required to close the gap on this unmet clinical need. A growing number of tissue engineering approaches are exploring the potential to generate lung tissue ex vivo for transplantation. Both biologically derived and manufactured scaffolds seeded with cells and grown ex vivo have been explored in pre-clinical studies, with the eventual goal of generating functional pulmonary tissue for transplantation. Recently, there have been significant efforts to scale-up cell culture methods to generate adequate cell numbers for human-scale bioengineering approaches. Concomitantly, there have been exciting efforts in designing bioreactors that allow for appropriate cell seeding and development of functional lung tissue over time. This review aims to present the current state-of-the-art progress for each of these areas and to discuss promising new ideas within the field of lung bioengineering.

Validating Metal-Organic Framework Nanoparticles for Their Nanosafety in Diverse Biomedical Applications.

Metal-organic frameworks (MOFs) are promising platforms for the synthesis of nanoparticles for diverse medical applications. Their fundamental design principles allow for significant control of the framework architecture and pore chemistry, enabling directed functionalization for nanomedical applications. However, before applying novel nanomaterials to patients, it is imperative to understand their potential health risks. In this study, the nanosafety of different MOF nanoparticles is analyzed comprehensively for diverse medical applications. The authors first evaluate the effects of MOFs on human endothelial and mouse lung cells, which constitute a first line of defense upon systemic blood-mediated and local lung-specific applications of nanoparticles. Second, we validated these MOFs for multifunctional surface coatings of dental implants using human gingiva fibroblasts. Moreover, biocompatibility of MOFs is assessed for surface coating of nerve guidance tubes using human Schwann cells and rat dorsal root ganglion cultures. The main finding of this study is that the nanosafety and principal suitability of our MOF nanoparticles as novel agents for drug delivery and implant coatings strongly varies with the effector cell type. We conclude that it is therefore necessary to carefully evaluate the nanosafety of MOF nanomaterials with respect to their particular medical application and their interacting primary cell types, respectively.

Protease-mediated release of chemotherapeutics from mesoporous silica nanoparticles to ex vivo human and mouse lung tumors.

Nanoparticles allow for controlled and targeted drug delivery to diseased tissues and therefore bypass systemic side effects. Spatiotemporal control of drug release can be achieved by nanocarriers that respond to elevated levels of disease-specific enzymes. For example, matrix metalloproteinase 9 (MMP9) is overexpressed in tumors, is known to enhance the metastatic potency of malignant cells, and has been associated with poor prognosis of lung cancer. Here, we report the synthesis of mesoporous silica nanoparticles (MSNs) tightly capped by avidin molecules via MMP9 sequence-specific linkers to allow for site-selective drug delivery in high-expressing MMP9 tumor areas. We provide proof-of-concept evidence for successful MMP9-triggered drug release from MSNs in human tumor cells and in mouse and human lung tumors using the novel technology of ex vivo 3D lung tissue cultures. This technique allows for translational testing of drug delivery strategies in diseased mouse and human tissue. Using this method we show MMP9-mediated release of cisplatin, which induced apoptotic cell death only in lung tumor regions of Kras mutant mice, without causing toxicity in tumor-free areas or in healthy mice. The MMP9-responsive nanoparticles also allowed for effective combinatorial drug delivery of cisplatin and proteasome inhibitor bortezomib, which had a synergistic effect on the (therapeutic) efficiency. Importantly, we demonstrate the feasibility of MMP9-controlled drug release in human lung tumors.