In vivo assessment of the pulmonary microcirculation in elastase-induced emphysema using probe-based confocal fluorescence microscopy

The role of confocal laser endomicroscopy in pulmonary medicine

Accurate diagnosis and subsequent therapeutic options in pulmonary diseases mainly rely on imaging methods and histological assessment. However, imaging examinations are hampered by the limited spatial resolution of images and most procedures that are related to histological assessment are invasive with associated complications. As a result, a high-resolution imaging technology - confocal laser endomicroscopy (CLE), which is at the forefront and enables real-time microscopic visualisation of the morphologies and architectures of tissues or cells - has been developed to resolve the clinical dilemma pertaining to current techniques. The current evidence has shown that CLE has the potential to facilitate advanced diagnostic capabilities, to monitor and to aid the tailored treatment regime for patients with pulmonary diseases, as well as to expand the horizon for unravelling the mechanism and therapeutic targets of pulmonary diseases. In the future, if CLE can be combined with artificial intelligence, early, rapid and accurate diagnosis will be achieved through identifying the images automatically. As promising as this technique may be, further investigations are required before it can enter routine clinical practice.

Quantitative intravital two-photon excitation microscopy reveals absence of pulmonary vaso-occlusion in unchallenged Sickle Cell Disease mice

Sickle cell disease (SCD) is a genetic disorder that leads to red blood cell (RBC) sickling, hemolysis and the upregulation of adhesion molecules on sickle RBCs. Chronic hemolysis in SCD results in a hyper-inflammatory state characterized by activation of circulating leukocytes, platelets and endothelial cells even in the absence of a crisis. A crisis in SCD is often triggered by an inflammatory stimulus and can lead to the acute chest syndrome (ACS), which is a type of lung injury and a leading cause of mortality among SCD patients. Although it is believed that pulmonary vaso-occlusion could be the phenomenon contributing to the development of ACS, the role of vaso-occlusion in ACS remains elusive. Intravital imaging of the cremaster microcirculation in SCD mice has been instrumental in establishing the role of neutrophil-RBC-endothelium interactions in systemic vaso-occlusion; however, such studies, although warranted, have never been done in the pulmonary microcirculation of SCD mice. Here, we show that two-photon excitation fluorescence microscopy can be used to perform quantitative analysis of neutrophil and RBC trafficking in the pulmonary microcirculation of SCD mice. We provide the experimental approach that enables microscopic observations under physiological conditions and use it to show that RBC and neutrophil trafficking is comparable in SCD and control mice in the absence of an inflammatory stimulus. The intravital imaging scheme proposed in this study can be useful in elucidating the cellular and molecular mechanism of pulmonary vaso-occlusion in SCD mice following an inflammatory stimulus.

Structure-function relationship in COPD revisited: an in vivo microscopy view

BACKGROUND

Fibred confocal fluorescence microscopy (FCFM) is a novel technology that allows the in vivo assessment and quantification during bronchoscopy of the bronchial wall elastic fibre pattern, alveolar and vessel diameters and thickness of the elastic fibre in the alveolar wall.

AIMS

To relate these structural characteristics with lung function parameters in healthy subjects, smokers with normal spirometry and patients with chronic obstructive pulmonary disease (COPD).

METHODS

We performed FCFM in 20 never smokers, 20 smokers with normal spirometry and 23 patients with COPD who required bronchoscopy for clinical reasons. The bronchial wall elastic fibre pattern was classified as lamellar, loose and mixed pattern, and later confirmed pathologically. Airspace dimensions and extra-alveolar vessel diameters were measured. Lung function measurements and pulmonary CT scans were obtained in all participants.

RESULTS

Patients with COPD were characterised by a significantly higher prevalence of loose fibre bronchial deposition pattern and larger alveolar diameter which correlated inversely with several lung function parameters (forced expiratory volume in 1 s (FEV1) , FEV1/forced vital capacity ratio, maximum expiratory flow, carbon monoxide transfer factor and carbon monoxide transfer coefficient; p<0.05). Increased alveolar macrophages were demonstrated in active smokers with or without COPD.

CONCLUSIONS

This is the first FCFM study to describe in vivo microscopic changes in the airways and alveoli of patients with COPD that are related to lung function impairment. These findings open the possibility of assessing the in vivo effects of therapeutic interventions for COPD in future studies.