Type II pneumocytes synthesize, store and release pulmonary surfactant into the alveolar space. Since surfactant reduces alveolar surface tension, it prevents alveoli from collapsing and enables the inspiration. Although the importance of surfactant for respiratory function is commonly accepted, only little is known about the ontogeny of surfactant storing veiscles, called lamellar bodies in type II pneumocytes. In order to investigate the lamellar body ontogeny, we established culturing conditions for fetal rat pneumocytes which maintain their ability to progressively increase the number and size of their lamellar body like vesicles. Cells cultured under these conditions for four days usually contain small vesicles with a lamellar membrane content as well as larger vesicles with aggregates of small lamellar body like structures adjacent to the inner side of their boardering membrane. After eight days of culturing, vesicles were enlarged and typically showed a lamellar body like structure as well as presumed lamellar body precursors, so called multi vesicular bodies. Therefore, our cellular model is more suitable than established ex vivo models based on primary cultures for the investigation of typ II pneumocytes differentiation and the biogenesis of lamellar bodies.

Supported by FWF, Projects P15742 & P15743; DFG, Project D1402 and the 6th framework of the European Union, Pulmonet.