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Swift transformation and locomotion of polymorphonuclear leukocytes and microglia as observed by VEC-DIC microscopy
M Tomita1, Y Fukuuchi, N Tanahashi
1Department of Neurology, School of Medicine, Keio University, Tokyo, Japan.
Abstract:
The detailed assembly used by us for video-enhanced contrast-differential interference contrast (VEC-DIC) microscopy (video microscopy is first described. Employing such video microscopy, we then examined the morphological changes occurring during locomotion and activation processes of polymorphonuclear leukocytes (PMNL) and microglia at an almost electron microscopic magnification. Upon contacting the substratum, PMNL transformed into a polarized ameboid shape and crawled extending pseudopodia, as has been well documented previously. The PMNL sometimes displayed a peculiar locomotion as if they were stepping on "tiny legs", or sliding on a treadmill of cell membrane. Cultured microglia were observed to exist in 4 forms; ramified, reactive, villous, and ameboid. Microglia in the reactive form pivoted, circled and crawled on the astroglial cell layer using their transparent lamellipodia with no morphological changes in their cell body. Unlike PMNL, reactive microglia exhibited no agitated movements of their intracellular organelles, including granules and cytosol, during locomotion. Lamellipodia on the undersurface of the cell body touching the cell layer adhesively, appeared to serve as the locomotive apparatus. When activated, both floating PMNL and microglia of villous form assumed an ameboid shape within a few seconds. Microglia occasionally swam in the medium waving their lamellipodia towards a target object (e.g. zymosan A particles), remodelling to an amorphous ameboid form and covering up the target. We attempt to discuss such swift morphological changes from the standpoint of thermodynamic potential of Gibbs free energy which is stored within the cells.
Insights
Video-enhanced contrast-differential interference contrast (VEC-DIC) microscopy revealed dynamic cell behaviors. Polymorphonuclear leukocytes (PMNL) and microglia exhibit distinct locomotion and rapid shape changes during activation and movement.
Area of Science:
- Cell biology
- Microscopy techniques
- Immunology
Background:
- Polymorphonuclear leukocytes (PMNL) and microglia are crucial immune cells.
- Understanding their dynamic morphological changes is key to immune response research.
- Previous studies documented basic cell movements, but high-resolution dynamics remained unclear.
Purpose of the Study:
- To detail the morphological transformations of PMNL and microglia during locomotion and activation using advanced microscopy.
- To observe and characterize unique cellular movement patterns at near-electron microscopic resolution.
- To explore the thermodynamic principles underlying these rapid cellular shape changes.
Main Methods:
- Development and application of video-enhanced contrast-differential interference contrast (VEC-DIC) microscopy.
- Observation of cultured human PMNL and microglia on a substratum and in medium.
- Analysis of cellular morphology during locomotion, activation, and target interaction.
Main Results:
- PMNL exhibited polarized ameboid shapes and pseudopod extension during locomotion.
- Microglia displayed four distinct forms (ramified, reactive, villous, ameboid) with unique locomotion styles.
- Reactive microglia utilized lamellipodia for adhesion and movement without internal agitation.
- Both cell types rapidly assumed ameboid shapes upon activation, with microglia sometimes swimming towards targets.
Conclusions:
- VEC-DIC microscopy provides unprecedented detail of leukocyte and microglial dynamics.
- Cellular locomotion and activation involve rapid, significant morphological adaptations.
- The observed swift changes suggest underlying mechanisms related to cellular energy states, potentially explained by Gibbs free energy principles.