The development of the bioartificial lung

An overview of the production of tissue extracellular matrix and decellularization process

Thousands of patients need an organ transplant yearly, while only a tiny percentage have this chance to receive a tissue/organ transplant. Nowadays, decellularized animal tissue is one of the most widely used methods to produce engineered scaffolds for transplantation. Decellularization is defined as physically or chemically removing cellular components from tissues while retaining structural and functional extracellular matrix (ECM) components and creating an ECM-derived scaffold. Then, decellularized scaffolds could be reseeded with different cells to fabricate an autologous graft. Effective decellularization methods preserve ECM structure and bioactivity through the application of the agents and techniques used throughout the process. The most valuable agents for the decellularization process depend on biological properties, cellular density, and the thickness of the desired tissue. ECM-derived scaffolds from various mammalian tissues have been recently used in research and preclinical applications in tissue engineering. Many studies have shown that decellularized ECM-derived scaffolds could be obtained from tissues and organs such as the liver, cartilage, bone, kidney, lung, and skin. This review addresses the significance of ECM in organisms and various decellularization agents utilized to prepare the ECM. Also, we describe the current knowledge of the decellularization of different tissues and their applications.

Epidemiology and Long-Term Outcomes in Thoracic Transplantation

Over the past five decades, outcomes for lung transplantation have significantly improved in the early post-operative period, such that lung transplant is now the gold standard treatment for end-stage respiratory disease. The major limitation that impacts lung transplant survival rates is the development of chronic lung allograft dysfunction (CLAD). CLAD affects around 50% of lung transplant recipients within five years of transplantation. We must also consider other factors impacting the survival rate such as the surgical technique (single versus double lung transplant), along with donor and recipient characteristics. The future is promising, with more research looking into ex vivo lung perfusion (EVLP) and bioengineered lungs, with the hope of increasing the donor pool and decreasing the risk of graft rejection.

The evolution of the global COVID-19 epidemic in Morocco and understanding the different therapeutic approaches of chitosan in the control of the pandemic

In 2020, Coronavirus disease (COVID-19), a new viral respiratory disease caused by a virus that belongs to Coronaviridae family, has been identified. It is a very severe flu that negatively affects the functions of the lung and other respiratory organs. COVID-19 virus can be transmitted between people either by touching an infected person or by direct contact with their respiratory droplets. Therefore, the COVID-19 virus has become a global concern due to its rapid spread and severity. Based on the World Health Organization report from 2 March 2020 to 24 October 2022, the total infected cases and deaths in Morocco are around 1,265,389 (3.46%) and 16,280 (0.04%), respectively. Recently, some scientists have found that chitosan, a polymer existed in nature, can inhibit COVID-19 infection and repair damaged tissue. Therefore, understanding chitosan mechanisms in controlling COVID-19, might lead to innovative strategies in the medical field, such as developing drugs against SARS-CoV-2, and replacing vaccines, which have negative side effects. This review aims to show the evolution of the COVID-19 pandemic worldwide, specifically in Morocco, its pathophysiology, and its ability to silence the immune system. This review also provides an overview of the treatments and measures applied to protect human beings and how chitosan acts and controls COVID-19.

Emerging Paradigms in Bioengineering the Lungs

In end-stage lung diseases, the shortage of donor lungs for transplantation and long waiting lists are the main culprits in the significantly increasing number of patient deaths. New strategies to curb this issue are being developed with the help of recent advancements in bioengineering technology, with the generation of lung scaffolds as a steppingstone. There are various types of lung scaffolds, namely, acellular scaffolds that are developed via decellularization and recellularization techniques, artificial scaffolds that are synthesized using synthetic, biodegradable, and low immunogenic materials, and hybrid scaffolds which combine the advantageous properties of materials in the development of a desirable lung scaffold. There have also been advances in the design of bioreactors in terms of providing an optimal regenerative environment for the maturation of functional lung tissue over time. In this review, the emerging paradigms in the field of lung tissue bioengineering will be discussed.

Cellular Immunotherapy and the Lung

The new era of cellular immunotherapies has provided state-of-the-art and efficient strategies for the prevention and treatment of cancer and infectious diseases. Cellular immunotherapies are at the forefront of innovative medical care, including adoptive T cell therapies, cancer vaccines, NK cell therapies, and immune checkpoint inhibitors. The focus of this review is on cellular immunotherapies and their application in the lung, as respiratory diseases remain one of the main causes of death worldwide. The ongoing global pandemic has shed a new light on respiratory viruses, with a key area of concern being how to combat and control their infections. The focus of cellular immunotherapies has largely been on treating cancer and has had major successes in the past few years. However, recent preclinical and clinical studies using these immunotherapies for respiratory viral infections demonstrate promising potential. Therefore, in this review we explore the use of multiple cellular immunotherapies in treating viral respiratory infections, along with investigating several routes of administration with an emphasis on inhaled immunotherapies.

Hemodynamic Assessment of Hollow-Fiber Membrane Oxygenators Using Computational Fluid Dynamics in Heterogeneous Membrane Models

Extracorporeal membrane oxygenation (ECMO) has been used clinically for more than 40 years as a bridge to transplantation, with hollow-fiber membrane (HFM) oxygenators gaining in popularity due to their high gas transfer and low flow resistance. In spite of the technological advances in ECMO devices, the inevitable contact of the perfused blood with the polymer hollow-fiber gas-exchange membrane, and the subsequent thrombus formation, limits their clinical usage to only 2–4 weeks. In addition, the inhomogeneous flow in the device can further enhance thrombus formation and limit gas-transport efficiency. Endothelialization of the blood contacting surfaces of ECMO devices offers a potential solution to their inherent thrombogenicity. However, abnormal shear stresses and inhomogeneous blood flow might affect the function and activation status of the seeded endothelial cells (ECs). In this study, the blood flow through two HFM oxygenators, including the commercially available iLA® MiniLung Petite Novalung (Xenios AG, Germany) and an experimental one for the rat animal model, was modeled using computational fluid dynamics (CFD), with a view to assessing the magnitude and distribution of the wall shear stress (WSS) on the hollow fibers and flow fields in the oxygenators. This work demonstrated significant inhomogeneity in the flow dynamics of both oxygenators, with regions of high hollow-fiber WSS and regions of stagnant flow, implying a variable flow-induced stimulation on seeded ECs and possible EC activation and damage in a biohybrid oxygenator setting.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

Biomimetic Design for Bio-Matrix Interfaces and Regenerative Organs

The urgent demand for transplanted organs has motivated the development of regenerative medicine to biomimetically reconstruct the structure and function of natural tissues or organs. The prerequisites for constructing multicellular organs include specific cell sources, suitable scaffolding material, and interconnective biofunctional interfaces. As some of the most complex systems in nature, human organs, tissues, and cellular units have unique "bio-matrix" physicochemical interfaces. Human tissues support a large number of cells with distinct biofunctional interfaces for compartmentalization related to metabolism, material exchange, and physical barriers. These naturally shaped biofunctional interfaces support critical metabolic functions that drive adaptive human behavior. In contrast, mutations and disorders during organogenesis can disrupt these interfaces as a consequence of disease and trauma. To replicate the appropriate structure and physiological function of tissues and organs, the biomaterials used in these approaches should have properties that mimic those of natural biofunctional interfaces. In this review, the focus is on the biomimetic design of functional interfaces and hierarchical structures for four regenerative organs, liver, kidney, lung, heart, and the immune system. Research on these organs provides understanding of cell-matrix interactions for hierarchically bioinspired material engineering, and guidance for the design of bioartificial organs. Finally, we provide perspectives on future challenges in biofunctional interface designs and discuss the obstacles that remain toward the generation of functional bioartificial organs.

Bioengineering lungs - current status and future prospects

INTRODUCTION

Once pulmonary disease progresses to end-stage pulmonary disease, treatment options are very limited. An important advance in the field is the development of a bioartificial lung derived from a generic matrix scaffold populated with patients' own cells. Significant progress has already been made in the engineering of bioartificial lungs.

AREAS COVERED

This review explains how previous and current research contributes to the goal of creating a successful bioartificial lung, and the barriers faced in doing so. We will also highlight some of the design considerations being explored to optimize bioartificial lungs and considerations for clinical translation.

EXPERT OPINION

While current bioartificial lungs are able to provide short-term gas exchange in large-animal studies, much work is still required to combine the disciplines of cell biology, materials science, and tissue engineering to create such clinically useful and functioning artificial lungs.

New Approaches to Respiratory Assist: Bioengineering an Ambulatory, Miniaturized Bioartificial Lung

Although state-of-the-art treatments of respiratory failure clearly have made some progress in terms of survival in patients suffering from severe respiratory system disorders, such as acute respiratory distress syndrome (ARDS), they failed to significantly improve the quality of life in patients with acute or chronic lung failure, including severe acute exacerbations of chronic obstructive pulmonary disease or ARDS as well. Limitations of standard treatment modalities, which largely rely on conventional mechanical ventilation, emphasize the urgent, unmet clinical need for developing novel (bio)artificial respiratory assist devices that provide extracorporeal gas exchange with a focus on direct extracorporeal CO2 removal from the blood. In this review, we discuss some of the novel concepts and critical prerequisites for such respiratory lung assist devices that can be used with an adequate safety profile, in the intensive care setting, as well as for long-term domiciliary therapy in patients with chronic ventilatory failure. Specifically, we describe some of the pivotal steps, such as device miniaturization, passivation of the blood-contacting surfaces by chemical surface modifications, or endothelial cell seeding, all of which are required for converting current lung assist devices into ambulatory lung assist device for long-term use in critically ill patients. Finally, we also discuss some of the risks and challenges for the long-term use of ambulatory miniaturized bioartificial lungs.

Artificial lung

Lung transplantation remains the definitive curative treatment for end-stage lung disease. However, future applications of tissue bioengineering could overcome the donor organ shortage and the need for immunosuppression. The final goal of lung tissue engineering is to recreate the whole spectrum of specialized lung tissues and thereby provide physiologic functions through bioengineered conducting airways, vasculature and gas exchange tissue. This review focuses on ongoing research in artificial lung development, open questions, achievements to date and how tissue engineering and stem cell technology may further contribute to the clinical application of bioartificial lungs. Although experimental transplantation of bioartificial lung developed by perfusing decellularized or synthetic scaffolds has been shown to provide gas exchange in vivo over a prolonged period, it should be clearly acknowledged that the development of a transplantable bioartificial lung is far from reality.

Current Trends in Biomaterial Utilization for Cardiopulmonary System Regeneration

The cardiopulmonary system is made up of the heart and the lungs, with the core function of one complementing the other. The unimpeded and optimal cycling of blood between these two systems is pivotal to the overall function of the entire human body. Although the function of the cardiopulmonary system appears uncomplicated, the tissues that make up this system are undoubtedly complex. Hence, damage to this system is undesirable as its capacity to self-regenerate is quite limited. The surge in the incidence and prevalence of cardiopulmonary diseases has reached a critical state for a top-notch response as it currently tops the mortality table. Several therapies currently being utilized can only sustain chronically ailing patients for a short period while they are awaiting a possible transplant, which is also not devoid of complications. Regenerative therapeutic techniques now appear to be a potential approach to solve this conundrum posed by these poorly self-regenerating tissues. Stem cell therapy alone appears not to be sufficient to provide the desired tissue regeneration and hence the drive for biomaterials that can support its transplantation and translation, providing not only physical support to seeded cells but also chemical and physiological cues to the cells to facilitate tissue regeneration. The cardiac and pulmonary systems, although literarily seen as just being functionally and spatially cooperative, as shown by their diverse and dissimilar adult cellular and tissue composition has been proven to share some common embryological codevelopment. However, necessitating their consideration for separate review is the immense adult architectural difference in these systems. This review also looks at details on new biological and synthetic biomaterials, tissue engineering, nanotechnology, and organ decellularization for cardiopulmonary regenerative therapies.

Pulmonary vascular development goes awry in congenital lung abnormalities

Pulmonary vascular diseases of the newborn comprise a wide range of pathological conditions with developmental abnormalities in the pulmonary vasculature. Clinically, pulmonary arterial hypertension (PH) is characterized by persistent increased resistance of the vasculature and abnormal vascular response. The classification of PH is primarily based on clinical parameters instead of morphology and distinguishes five groups of PH. Congenital lung anomalies, such as alveolar capillary dysplasia (ACD) and PH associated with congenital diaphragmatic hernia (CDH), but also bronchopulmonary dysplasia (BPD), are classified in group three. Clearly, tight and correct regulation of pulmonary vascular development is crucial for normal lung development. Human and animal model systems have increased our knowledge and make it possible to identify and characterize affected pathways and study pivotal genes. Understanding of the normal development of the pulmonary vasculature will give new insights in the origin of the spectrum of rare diseases, such as CDH, ACD, and BPD, which render a significant clinical problem in neonatal intensive care units around the world. In this review, we describe normal pulmonary vascular development, and focus on four diseases of the newborn in which abnormal pulmonary vascular development play a critical role in morbidity and mortality. In the future perspective, we indicate the lines of research that seem to be very promising for elucidating the molecular pathways involved in the origin of congenital pulmonary vascular disease.

Inhibition of β-catenin/p300 interaction proximalizes mouse embryonic lung epithelium

BACKGROUND

Wnt/β-catenin signaling has been suggested to regulate proximal-distal determination of embryonic lung epithelium based upon genetically modified mouse models. The previously identified and characterized small molecule inhibitor IQ1 can pharmacologically decrease the interaction between β-catenin and its transcriptional coactivator p300, thereby enhancing the β-catenin/CBP interaction. Inhibition of the β-catenin/p300 interaction by IQ1 blocks the differentiation of embryonic stem cells and epicardial progenitor cells; however, whether differential coactivator usage by β-catenin plays a role in proximal-distal determination of lung epithelium is unknown.

METHODS

We examined the effects of inhibiting the β-catenin/p300 interaction with IQ1 on lung branching morphogenesis in mouse embryos in utero and mouse embryonic lung organ culture ex vivo. The phenotype of IQ1 treated lungs was analyzed by epithelial staining, histology, quantitative PCR and in situ hybridization.

RESULTS

Inhibition of the β-catenin/p300 interaction by IQ1 disrupted the distal branching of mouse lung epithelium both in utero and ex vivo. IQ1 proximalized lung epithelium with decreased expression of the genes Bmp4 and Fgf10, hallmarks of distal lung determination, and increased expression of the proximal genes Sox2 and Scgb1a1 (CC10) as shown by quantitative PCR and in situ hybridization. The disruption of branching was reversible ex vivo as branching was reinitiated after removal of IQ1 from the media.

CONCLUSIONS

The results demonstrate that the β-catenin/p300 interaction plays a critical role in proximal-distal determination of the epithelium in mouse lung branching morphogenesis and β-catenin/p300 inhibition pharmacologically proximalizes lung epithelium.

Inhibition of β-catenin/p300 interaction proximalizes mouse embryonic lung epithelium

Background

Wnt/β-catenin signaling has been suggested to regulate proximal-distal determination of embryonic lung epithelium based upon genetically modified mouse models. The previously identified and characterized small molecule inhibitor IQ1 can pharmacologically decrease the interaction between β-catenin and its transcriptional coactivator p300, thereby enhancing the β-catenin/CBP interaction. Inhibition of the β-catenin/p300 interaction by IQ1 blocks the differentiation of embryonic stem cells and epicardial progenitor cells; however, whether differential coactivator usage by β-catenin plays a role in proximal-distal determination of lung epithelium is unknown.

Methods

We examined the effects of inhibiting the β-catenin/p300 interaction with IQ1 on lung branching morphogenesis in mouse embryos in utero and mouse embryonic lung organ culture ex vivo. The phenotype of IQ1 treated lungs was analyzed by epithelial staining, histology, quantitative PCR and in situ hybridization.

Results

Inhibition of the β-catenin/p300 interaction by IQ1 disrupted the distal branching of mouse lung epithelium both in utero and ex vivo. IQ1 proximalized lung epithelium with decreased expression of the genes Bmp4 and Fgf10, hallmarks of distal lung determination, and increased expression of the proximal genes Sox2 and Scgb1a1 (CC10) as shown by quantitative PCR and in situ hybridization. The disruption of branching was reversible ex vivo as branching was reinitiated after removal of IQ1 from the media.

Conclusions

The results demonstrate that the β-catenin/p300 interaction plays a critical role in proximal-distal determination of the epithelium in mouse lung branching morphogenesis and β-catenin/p300 inhibition pharmacologically proximalizes lung epithelium.