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Viscoelastic and motile properties of hamster lung and peritoneal macrophages
C L Bizal1, J P Butler, P A Valberg
1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts.
Abstract:
The motile and rheologic properties of hamster lung and peritoneal macrophages (LMs and PMs) were examined by following the motions of magnetizable iron oxide (gamma-Fe2O3) particles contained within phagolysosomes of these cells. As a measure of intracellular motility, gamma-Fe2O3 particles in cells were magnetically aligned and the decay rate of the remanent magnetic field (RMF) in the direction of initial magnetization was monitored over time. Cytoplasmic rheology was measured by twisting the intracellular particles with a magnetic field (Btw) applied perpendicularly to the direction of initial magnetization. We measured changes in the RMF associated with application and removal of Btw. Intracellular motility in LMs and PMs was not significantly different (P greater than 0.20); similarly, cytoplasmic viscosity was not significantly different in LMs and PMs (P greater than 0.12); deformation on application of torque was significantly greater (P less than 0.0001) and elastic recoil on removal of torque was significantly smaller (P less than 0.0001) in PMs than in LMs; and by qualitative observation, the yield stress of cytoplasm (associated with a plastic, nonrecoverable deformation) was lower in PMs than in LMs. These results show that although cytoplasmic motion and viscosity are similar in the two cell types, PM cytoplasm is less stiff than LM cytoplasm as determined by yield stress.
Insights
Peritoneal macrophages (PMs) exhibit less stiff cytoplasm than lung macrophages (LMs), with greater deformation and reduced elastic recoil. These findings highlight differences in macrophage mechanical properties.
Area of Science:
- Cell Biology
- Biophysics
- Immunology
Background:
- Macrophages play critical roles in immune responses.
- Understanding the mechanical properties of macrophages is essential for elucidating their function.
- Lung macrophages (LMs) and peritoneal macrophages (PMs) reside in different microenvironments, potentially leading to distinct cellular properties.
Purpose of the Study:
- To compare the intracellular motility and cytoplasmic rheology of hamster lung macrophages (LMs) and peritoneal macrophages (PMs).
- To investigate the mechanical differences between LMs and PMs using magnetizable particles.
Main Methods:
- Utilized magnetizable iron oxide (gamma-Fe2O3) particles within phagolysosomes to track cellular properties.
- Measured intracellular motility by monitoring the decay rate of the remanent magnetic field (RMF) after magnetic alignment.
- Assessed cytoplasmic rheology by applying torque with a perpendicular magnetic field (Btw) and measuring RMF changes.
Main Results:
- Intracellular motility and cytoplasmic viscosity were not significantly different between LMs and PMs.
- PMs showed significantly greater deformation upon torque application and smaller elastic recoil compared to LMs.
- Qualitative observations indicated a lower yield stress in PM cytoplasm, suggesting less stiffness.
Conclusions:
- Cytoplasmic motion and viscosity are similar in lung and peritoneal macrophages.
- Peritoneal macrophages possess less stiff cytoplasm than lung macrophages, characterized by greater deformability and reduced elastic recoil.
- These rheological differences may influence the distinct functional roles of LMs and PMs in vivo.