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Alveoli are the gas-exchange units of lung. The process of alveolar development, alveologenesis, is regulated by a complex network of signaling pathways that act on various cell types including alveolar type I and II epithelial cells, fibroblasts and the vascular endothelium. Dysregulated alveologenesis results in bronchopulmonary dysplasia in neonates and in adults, disrupted alveolar regeneration is associated with chronic lung diseases including COPD and pulmonary fibrosis. Therefore, visualizing alveologenesis is critical to understand lung homeostasis and for the development of effective therapies for incurable lung diseases. We have developed a technique to visualize alveologenesis in real-time using a combination of widefield microscopy and image deconvolution of precision-cut lung slices. Here, we describe this live imaging technique in step-by-step detail. This time-lapse imaging technique can be used to capture the dynamics of individual cells within tissue slices over a long time period (up to 16 h), with minimal loss of fluorescence or cell toxicity.

Epithelial abnormalities underpin the development of the middle ear disease, otitis media (OM). Until now, a well-characterized in vitro model of the middle ear (ME) epithelium that replicates the complex cellular composition of the middle ear has not been available. This chapter describes the development of a novel in vitro model of mouse middle ear epithelial cells (mMECs), cultured at the air-liquid interface (ALI). This system enables recapitulation of the characteristics of the native murine ME epithelium. We demonstrate that mMECs undergo differentiation into the varied cell populations seen within the native middle ear. Overall, our mMEC culture system can help better understand the cell biology of the middle ear and improve our understanding of the pathophysiology of OM. The model also has the potential to serve as a platform for validation of treatments designed to reverse aspects of epithelial remodeling underpinning OM development.

Aim: Human mesenchymal stem cells (hMSC) are multipotent progenitor cells. We propose the optimization of hMSC isolation and recovery using the application of a controlled hypoxic environment. Materials & Methods: We evaluated oxygen, glucose and serum in the recovery of hMSC from bone marrow (BMhMSC). Colony forming units-fibroblastic, cell numbers, tri-lineage differentiation, immunofluorescence and microarray were used to confirm and characterize BMhMSC. Results: In an optimized (2% O2, 4.5 g/l glucose and 5% serum) environment both colony forming units-fibroblastic (p = 0.01) and cell numbers (p = 0.0001) were enhanced over standard conditions. Transcriptional analysis identified differential expression of bone morphogenetic protein 2 (BMP2) and, putatively, chemokine (C-X-C motif) receptor 2 (CXCR2) signaling pathways. Conclusion: We have detailed a potential milestone in the process of refinement of the BMhMSC isolation process.

The airway epithelium secretes proteins that function in innate defense against infection. Bactericidal/permeability-increasing fold-containing family member A1 (BPIFA1) is secreted into airways and has a protective role during bacterial infections, but it is not known whether it also has an antiviral role. To determine a role in host defense against influenza A virus (IAV) infection and to find the underlying defense mechanism, we developed transgenic mouse models that are deficient in BPIFA1 and used these, in combination with in vitro three-dimensional mouse tracheal epithelial cell (mTEC) cultures, to investigate its antiviral properties. We show that BPIFA1 has a significant role in mucosal defense against IAV infection. BPIFA1 secretion was highly modulated after IAV infection. Mice deficient in BPIFA1 lost more weight after infection, supported a higher viral load and virus reached the peripheral lung earlier, indicative of a defect in the control of infection. Further analysis using mTEC cultures showed that BPIFA1-deficient cells bound more virus particles, displayed increased nuclear import of IAV ribonucleoprotein complexes, and supported higher levels of viral replication. Our results identify a critical role of BPIFA1 in the initial phase of infection by inhibiting the binding and entry of IAV into airway epithelial cells.Mucosal Immunology advance online publication 17 May 2017; doi:10.1038/mi.2017.45.

Differentiated embryonic stem cells (ESC) can ameliorate lung inflammation and fibrosis in animal lung injury models; therefore, ESC, or their products, could be candidates for regenerative therapy for incurable lung diseases, such as idiopathic pulmonary fibrosis (IPF). In this study, we have investigated the paracrine effect of differentiated and undifferentiated human ESC on alveolar epithelial cell (AEC) wound repair. hESC line, SHEF-2 cells were differentiated with Activin treatment for 22 days in an embryoid body (EB) suspension culture. Conditioned media (CM) which contain cell secretory factors were collected at different time points of differentiation. CM were then tested onin vitro wound repair model with human type II AEC line, A549 cells (AEC). Our study demonstrated that CM originated from undifferentiated hESC significantly inhibited AEC wound repair when compared to the control. Whereas, CM originated from Activin-directed hESC differentiated cell population demonstrated a differential reparative effect on AEC wound repair model. CM obtained from Day-11 of differentiation significantly enhanced AEC wound repair in comparison to CM collected from pre- and post-Day-11 of differentiation. Day-11 CM enhanced AEC wound repair through significant stimulation of cell migration and cell proliferation. RT-PCR and immunocytochemistry confirmed that Day-11 CM was originated form a mixed population of endodermal/mesodermal differentiated hESC. This report suggests a putative paracrine-mediated epithelial injury healing mechanism by hESC secreted products, which is valuable in the development of novel stem cell-based therapeutic strategies.

Club cells (Clara cells) participate in bronchiolar wound repair and regeneration. Located in the bronchioles, they become activated during alveolar injury in idiopathic pulmonary fibrosis (IPF) and migrate into the affected alveoli, a process called alveolar bronchiolisation. The purpose of this migration and the role of club cells in alveolar wound repair is controversial. This study was undertaken to investigate the role of club cells in alveolar epithelial wound repair and pulmonary fibrosis. A direct-contact co-culture in vitro model was used to evaluate the role of club cells (H441 cell line) on alveolar epithelial cell (A549 cell line) and small airway epithelial cell (SAEC) wound repair. Immunohistochemistry was conducted on lung tissue samples from patients with IPF to replicate the in vitro findings ex vivo. Our study demonstrated that club cells induce apoptosis in alveolar epithelial cells and SAECs through a tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-dependent mechanism resulting in significant inhibition of wound repair. Furthermore, in IPF lungs, TRAIL-expressing club cells were detected within the affected alveolar epithelia in areas of established fibrosis, together with widespread alveolar epithelial cell apoptosis. From these findings, we hypothesise that the extensive pro-fibrotic remodelling associated with IPF could be driven by TRAIL-expressing club cells inducing apoptosis in alveolar epithelial cells through a TRAIL-dependent mechanism.

The tissue turnover of unperturbed adult lung is remarkably slow. However, after injury or\ud insult, a specialised group of facultative lung progenitors become activated to replenish damaged\ud tissue through a reparative process called regeneration. Disruption in this process results in healing by\ud fibrosis causing aberrant lung remodelling and organ dysfunction. Post-insult failure of regeneration\ud leads to various incurable lung diseases including chronic obstructive pulmonary disease (COPD) and\ud idiopathic pulmonary fibrosis. Therefore, identification of true endogenous lung progenitors/stem\ud cells, and their regenerative pathway are crucial for next-generation therapeutic development. Recent\ud studies provide exciting and novel insights into postnatal lung development and post-injury lung\ud regeneration by native lung progenitors. Furthermore, exogenous application of bone marrow stem\ud cells, embryonic stem cells and inducible pluripotent stem cells (iPSC) show evidences of their\ud regenerative capacity in the repair of injured and diseased lungs. With the advent of modern tissue\ud engineering techniques, whole lung regeneration in the lab using de-cellularised tissue scaffold\ud and stem cells is now becoming reality. In this review, we will highlight the advancement of our\ud understanding in lung regeneration and development of stem cell mediated therapeutic strategies in\ud combating incurable lung diseases.

BPIFA1 is a member the bactericidal/permeability-increasing (BPI) protein family and is structurally similar to other BPIF family members with demonstrated innate immune roles. It is produced mainly in the mammalian respiratory tract and has been implicated in airway host defense against respiratory pathogens. However, the function of this protein is yet unresolved in many species and by elucidating this will aid to clarify its physiological role within the lungs. The objective of this study was to assess BPIFA1 expression and function in the respiratory tract in response to Influenza A virus. Using BPIFA1 knockout mice, we have shown increased virus load and inflammation in the lungs of these mice infected with the X31 strain (H3N2) as compared with wild-type controls. Interestingly, there were large peri-vascular aggregations of B cells in the lungs of BPIFA1-/- mice suggesting a role of BPIFA1 in modulating antibody responses. Lung tissues from mice infected with different strains of varying pathogenicities of Influenza A virus were analysed by immunohistochemical methods at specific time points during the infection period. Imaging software was then used to quantify the level of protein expression within the respiratory epithelium. It was found that the level of BPIFA1 decreased in response to highly pathogenic H5N1 and H7N9 infections but not to low pathogenicity H5N1 or H1N1 viruses. This alteration in expression was associated with an inflammatory response within the respiratory tissue surrounding the epithelium. Our data indicate that BPIFA1 influences inflammation and possibly signals to immune cells during Influenza A virus infection.

Although BPIFA1 is one of the most abundant secretory proteins in the upper airways, its9 function remains unclear. We have recently shown a reduction of BPIFA1 in the airways following influenza-A virus infection. In the present study we evaluated the host defence role of BPIFA1 in viral respiratory infection using an in vitro tracheal model. Tracheal epithelial cells isolated from wild-type and bpifa -/- mice, were seeded onto transwells and differentiated in ALI culture. Differentiated epithelium was infected with influenza-A virus (H3N2). Samples were collected at 2, 24, 48 and 72 hpi (hours post infection). Our data shows that the differentiated epithelial layer mimics the original tracheal epithelium, and abundant BPIFA1 was detected in the apical secretions and cytoplasm of differentiated epithelium. Influenza-A infection initiated inflammatory gene expression, where, IL-6 (2 hpi), TNF-α, IFN-β and IFN-λ2 (24 hpi) were highly upregulated. Influenza-A primarily infected ciliated cells, these cells then lost physical cilia and they down-regulated ciliated gene expression. At low dose (MOI-0.1), BPIFA1 and MUC5B expressing cells were largely uninfected. However, at high dose (MOI-0.5), BPIFA1 +ve cells were also infected and BPIFA1 was down-regulated 6-fold within 48 hpi. At 24 and 48 hpi, viral load was 2.3-fold higher in bpifa -/- cells with these cells exhibiting increased cell death compared to wild-type cell cultures. Our data suggest that BPIFA1 abrogates influenza-A viral infection and therefore, can be a novel target for antiviral treatment for respiratory tract infections.

Idiopathic pulmonary fibrosis (IPF) is a progressive, debilitating, and fatal lung disease of unknown aetiology with no current cure. The pathogenesis of IPF remains unclear but repeated alveolar epithelial cell (AEC) injuries and subsequent apoptosis are believed to be among the initiating/ongoing triggers. However, the precise mechanism of apoptotic induction is hitherto elusive. In this study, we investigated expression of a panel of pro-apoptotic and cell cycle regulatory proteins in 21 IPF and 19 control lung tissue samples. We reveal significant upregulation of the apoptosis-inducing ligand TRAIL and its cognate receptors DR4 and DR5 in AEC within active lesions of IPF lungs. This upregulation was accompanied by pro-apoptotic protein p53 overexpression. In contrast, myofibroblasts within the fibroblastic foci of IPF lungs exhibited high TRAIL, DR4 and DR5 expression but negligible p53 expression. Similarly, p53 expression was absent or negligible in IPF and control alveolar macrophages and lymphocytes. No significant differences in TRAIL expression were noted in these cell types between IPF and control lungs. However, DR4 and DR5 upregulation was detected in IPF alveolar macrophages and lymphocytes. The marker of cellular senescence p21(WAF1) was upregulated within affected AEC in IPF lungs. Cell cycle regulatory proteins Cyclin D1 and SOCS3 were significantly enhanced in AEC within the remodelled fibrotic areas of IPF lungs but expression was negligible in myofibroblasts. Taken together these findings suggest that, within the remodelled fibrotic areas of IPF, AEC can display markers associated with proliferation, senescence, and apoptotosis, where TRAIL could drive the apoptotic response. Clear understanding of disease processes and identification of therapeutic targets will direct us to develop effective therapies for IPF.

In this study, collagen-elastin constructs were prepared with the aim of producing a material capable of mimicking the mechanical properties of a single alveolar wall. Collagen has been used in a wide range of tissue engineering applications; however, due to its low mechanical properties its use is limited to non load-bearing applications without further manipulation using methods such as cross-linking or mechanical compression. Here, it was hypothesised that the addition of soluble elastin to a collagen hydrogel could improve its mechanical properties. Hydrogels made from collagen only and collagen plus varying amounts elastin were prepared. Young׳s modulus of each membrane was measured using the combination of a non-destructive indentation and a theoretical model previously described. An increase in Young׳s modulus was observed with increasing concentration of elastin. The use of non-destructive indentation allowed for online monitoring of the elastic moduli of cell-seeded constructs over 8 days. The addition of lung fibroblasts into the membrane increased the stiffness of the hydrogels further and cell-seeded collagen hydrogels were found to have a stiffness equal to the theoretical value for a single alveolar wall (≈5kPa). Through provision of some of the native extracellular matrix components of the lung parenchyma these scaffolds may be able to provide an initial building block toward the regeneration of new functional lung tissue.

Mesenchymal stem cells (MSCs), a distinct population of adult stem cells, have amassed significant interest from both medical and scientific communities. An inherent multipotent differentiation potential offers a cell therapy option for various diseases, including those of the musculoskeletal, neuronal, cardiovascular and pulmonary systems. MSCs also secrete an array of paracrine factors implicated in the mitigation of pathological conditions through anti-inflammatory, anti-apoptotic and immunomodulatory mechanisms. The safety and efficacy of MSCs in human application have been confirmed through small- and large-scale clinical trials. However, achieving the optimal clinical benefit from MSC-mediated regenerative therapy approaches is entirely dependent upon adequate understanding of their healing/regeneration mechanisms and selection of appropriate clinical conditions. MSC-mediated acute alveolar injury repair. A cartoon depiction of an injured alveolus with associated inflammation and AEC apoptosis. Proposed routes of MSC delivery into injured alveoli could be by either intratracheal or intravenous routes, for instance. Following delivery a proposed mechanism of MSC action is to inhibit/reduce alveolar inflammation by abrogation of IL-1_-depenedent Tlymphocyte proliferation and suppression of TNF-_ secretion via macrophage activation following on from stimulation by MSC-secreted IL-1 receptor antagonist (IL-1RN). The inflammatory environment also stimulates MSC to secrete prostaglandin-E2 (PGE2) which can stimulate activated macrophages to secrete the anti-inflammatory cytokine IL-10. Inhibition of AEC apoptosis following injury can also be promoted via MSC stimulated up-regulation of the anti-apoptotic Bcl-2 gene. MSC-secreted KGF can stimulate AECII proliferation and migration propagating alveolar epithelial restitution. Alveolar structural engraftment of MSC is a rare event.

Mesenchymal stem cells (MSCs), a distinct population of adult stem cells, have amassed significant interest from both medical and scientific communities. An inherent multipotent differentiation potential offers a cell therapy option for various diseases, including those of the musculoskeletal, neuronal, cardiovascular and pulmonary systems. MSCs also secrete an array of paracrine factors implicated in the mitigation of pathological conditions through anti-inflammatory, anti-apoptotic and immunomodulatory mechanisms. The safety and efficacy of MSCs in human application have been confirmed through small- and large-scale clinical trials. However, achieving the optimal clinical benefit from MSC-mediated regenerative therapy approaches is entirely dependent upon adequate understanding of their healing/regeneration mechanisms and selection of appropriate clinical conditions. MSC-mediated acute alveolar injury repair. A cartoon depiction of an injured alveolus with associated inflammation and AEC apoptosis. Proposed routes of MSC delivery into injured alveoli could be by either intratracheal or intravenous routes, for instance. Following delivery a proposed mechanism of MSC action is to inhibit/reduce alveolar inflammation by abrogation of IL-1_-depenedent Tlymphocyte proliferation and suppression of TNF-_ secretion via macrophage activation following on from stimulation by MSC-secreted IL-1 receptor antagonist (IL-1RN). The inflammatory environment also stimulates MSC to secrete prostaglandin-E2 (PGE2) which can stimulate activated macrophages to secrete the anti-inflammatory cytokine IL-10. Inhibition of AEC apoptosis following injury can also be promoted via MSC stimulated up-regulation of the anti-apoptotic Bcl-2 gene. MSC-secreted KGF can stimulate AECII proliferation and migration propagating alveolar epithelial restitution. Alveolar structural engraftment of MSC is a rare event.

Hypothesis Idiopathic pulmonary fibrosis (IPF) remains an incurable fibrotic lung disease. A mesenchymal stem cell (MSC)-mediated regenerative approach has been proposed; MSC-mediated anti-fibrotic effects have been demonstrated in animal lung-fibrosis models. However the mechanism of action and effect on myofibroblastic differentiation are unknown. The Wnt family member, Wnt-3a, has been implicated as an inducer of myofibroblastic differentiation in fibroblast cell models. This study explores the influence of MSC secreted factors on Wnt-3a and TGF-β1-induced lung myofibroblastic differentiation. Method Human normal lung (CCD-8Lu) and IPF (LL29) fibroblasts were differentiated with Wnt-3a for 72-hours and TGF-β1 for 24-hours. MSC-mediated differentiation inhibition was assessed by co-incubation of fibroblasts with MSC-CM and either Wnt-3a for 72-hours or TGF-β1 for 24-hours. TGF-β1-induced myofibroblastic differentiation reversal was explored with MSC-CM incubation for 24, 48 and 72-hours. Myofibroblast differentiation was assessed by immunocytochemical detection of α-smooth muscle actin expression. Results Myofibroblastic differentiation following TGF-β1 treatment was achieved in 86.27+2.57% CCD-8Lu cells and 86.69+2.51% LL29 cells respectively. Similar, though reduced, levels of myofibroblastic differentiation were achieved in 52.9±0.2% CCD-8Lu and 55.6±5.9% LL29 cells respectively following Wnt-3a treatment. In contrast, a percentage reduction in myofibroblastic differentiation was achieved in CCD-8Lu 31.40+1.44% and LL29 35.69+7.47% cells following exposure to TGF-β1 in the presence of MSC-CM versus TGF-β1 alone (p A reversal of TGF-β1-induced myofibroblastic differentiation was observed following 72-hours administration of MSC-CM compared to serum-free culture media (p Conclusion MSC-CM appears to inhibit fibroblast to myofibroblast differentiation, over-riding the pro-differentiation effects of Wnt-3a and TGF-β1. Whilst both TGF-β1 and Wnt-3a have emerged as key players in IPF pathogenesis, we are the first to demonstrate that MSC-CM may be crucial in modulating their pro-fibrogenic effects. These actions of MSC-CM demonstrate exploitative potential for future anti-IPF therapeutic strategies.