Direct visualisation of microparticles in the living lung.

Microparticles (MP) and fibres can be inhaled and cause inflammatory lung diseases. So far MP and fibres have not observed directly in the lung of living animals. A direct visualisation of particles and fibres would be important to study interactions with local and immigration host cells. In this methodical report latex beads were used as model particles for, e.g. nanoparticles, dusts, pollen or bacteria and were investigated using intravital fluorescence microscopy. Intravital fluorescence microscopy of the lung periphery is challenging because of the constant movement of the lung tissue and the heart. Chest window techniques have been described for investigation of lung vessels. For investigation of MP in larger areas of the lung surface this study presents an open chest-technique. Fluorescent MP were instilled into the trachea and could be observed in the alveoli of the right lung. Abundant numbers of MP were found within alveolar macrophages indicating that they are actively engulfed. Using the same setup also fluorescence labelled bacteria and its phagocytosis could be observed as shown in preliminary experiments. In conclusion, we present a method to analyse MP/fibres and its interaction with local and immigrating host cells in the living lung.