Development of biomimetic co-culture and tri-culture models to mimic the complex structure of the alveolar-capillary barrier

First contact: an interdisciplinary guide into decoding H5N1 influenza virus interactions with glycosaminoglycans in 3D respiratory cell models

The human respiratory system is vulnerable to viral infections. The influenza virus family alone accounts for one billion reported cases annually, some of which are severe and can be fatal. Among these, Influenza A viruses (IAVs) cause the most severe symptoms and course of disease. IAV has been a major health concern, especially since the emergence of the potentially pandemic avian H5N1 strain. However, despite the knowledge that IAVs recognize terminally attached sialic acids on the host cell surface for cell entry, the involvement of other glycans during early infection remains to be elucidated. In particular, the involvement of the alveolar epithelial glycocalyx as a last line of defense is often overlooked. Studying early infection of any virus in real time remains a challenge due to the currently available model systems and imaging techniques. Therefore, we extensively compare the use of different 3D cell systems and provide an overview of currently available scaffold-based and scaffold-free air-liquid interface (ALI) models. In addition, we discuss in detail the preferred use of a recently developed 3D organ tissue equivalent (OTE) model incorporating solubilized extracellular matrix components (sECM) to study viral interaction with glycosaminoglycans (GAGs) during the early stages of IAV infection. We further discuss and recommend the use of various synthetic virus models over IAV virions to reduce complexity by focusing only on surface protein interactions while simultaneously lowering the required biosafety levels, including, but not limited to virus-like particles (VLPs) or DNA origami. Finally, we delve into potential labeling strategies for IAV or IAV-like particles by reviewing internal and external labeling strategies with quantum dots (QDs) and potential GAG labeling, combined with a recommendation to combine high spatial resolution imaging techniques with high temporal resolution tracking, such as single virus tracking.

Influence of macrophages and neutrophilic granulocyte-like cells on crystalline silica-induced toxicity in human lung epithelial cells

In many industrial activities, workers may be exposed by inhalation to particles that are aerosolized, To predict the human health hazard of these materials, we propose to develop a co-culture model (macrophages, granulocytes, and alveolar epithelial cells) designed to be more representative of the inflammatory pulmonary response occurring in vivo. Phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 cells were used as macrophages, All-trans retinoic acid (ATRA)-differentiated HL60 were used as granulocytes and A549 were used as epithelial alveolar type II cells. A crystalline silica sample DQ12 was used as a prototypical particle for its capabilities to induce DNA damage, inflammatory response, and oxidative stress in epithelial cells; its polyvinylpyridine-N-oxide (PVNO)-surface modified counterpart was also used as a negative particulate control. Cells in mono-, bi- or tri-culture were exposed to DQ12 or DQ12-PVNO for 24 h. DQ12 but not DQ12-PVNO induced a significant increase in DNA damage in A549 cells. The presence of differentiated THP-1 reduced the genotoxic effects of this crystalline silica sample. The exposure of A549 to DQ12 but not DQ12-PVNO induced a significant change in interleukin-8 (IL-8) protein levels which was exacerbated when differentiated THP-1, and HL-60, were added. In addition, while no production of TNFα was detected in the A549 monoculture, elevated levels of this cytokine were observed in the co-culture systems. This work shows that a cell culture model that takes into consideration the complexity of the pulmonary inflammatory response might be more dependable to study the toxicological properties of particles than "simple" monoculture models.

A miniaturized multicellular platform to mimic the 3D structure of the alveolar-capillary barrier

Several diseases affect the alveoli, and the efficacy of medical treatments and pharmaceutical therapies is hampered by the lack of pre-clinical models able to recreate in vitro the diseases. Microfluidic devices, mimicking the key structural and compositional features of the alveoli, offer several advantages to medium and high-throughput analysis of new candidate therapies. Here, we developed an alveolus-on-a-chip recapitulating the microanatomy of the physiological tissue by including the epithelium, the fibrous interstitial layer and the capillary endothelium. A PDMS device was obtained assembling a top layer and a bottom layer obtained by replica molding. A polycaprolactone/gelatin (PCL-Gel) electrospun membrane was included within the two layers supporting the seeding of 3 cell phenotypes. Epithelial cells were grown on a fibroblast-laden collagen hydrogel located on the top side of the PCL-Gel mats while endothelial cells were seeded on the basolateral side of the membrane. The innovative design of the microfluidic device allows to replicate both cell-cell and cell-extracellular matrix interactions according to the in vivo cell arrangement along with the establishment of physiologically relevant air-liquid interface conditions. Indeed, high cell viability was confirmed for up to 10 days and the formation of a tight endothelial and epithelial barrier was assessed by immunofluorescence assays.