Extension of osmolality-induced podia is observed from fluorescently labeled hematopoietic cell lines in hyperosmotic medium

Abstract

Background: Since the description of long podia extended by hematopoietic cells and cell lines, the reliable elicitation of podia extensions is needed to study these podia systemically. In this study, hyperosmotic stress was considered as an elicitor. Methods: Using two fluorescent membrane dyes PKH2 and PKH26, and an automated fluorescence microscopy system, morphological changes of seven human cell lines (six hematopoietic, one fibrosarcoma) at different osmolalities were monitored. Presence of surface molecules on the hyperosmolality-induced podia (osmopodia) was examined. Results: In hyperosmotic medium, cells shrank rapidly, followed by osmopodia extension. Cells exhibited variable number (up to five) and length (up to longer than 100 μm) of osmopodia in about 1 h. Dead cells did not extend podia. Frequency, length, and number of podia were variable among cell lines studied. CD44 and CD45 were not present on the osmopodia, although they were present on the cell surface, showing that osmopodia-characteristics differ from the podia observed previously in isotonic media. The osmopodia extension process was shown to be reversible upon repeated osmolality changes. Conclusions: Osmopodia extended by human hematopoietic cell lines display a newly observed cellular morphology and provide a tool for investigation of dynamic cellular response to environmental changes. (C) 2000 Wiley-Liss, Inc.