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Probing mechanical properties of living cells by magnetopneumography
1GSF National Research Center for Environment and Health, Institute for Inhalation Biology, Neuherberg, Germany.
Abstract:
Magnetopneumography (MPG) has been used to study long-term particle clearance from human lungs as well as cellular motility of pulmonary macrophages (PMs). This study describes an extension of the method enabling the measurement of mechanical properties of PM cells in vivo. Ferromagnetic microparticles are inhaled and then retained in the alveolar region of the lungs, where they are phagocytized within hours by PMs. The magnetic particles can be rotated in weak magnetic fields, and the response to this twisting shear (force) is detected as a macroscopic magnetic field producing a measure of cytoskeletal mechanics. Cytoplasmic viscosity is very high compared with that of water and is strongly non-Newtonian. Under rotational stresses from 0.4 to 6.4 Pa, it acts like a pseudoplastic fluid showing a characteristic shear rate dependence. The viscosity as well as the stiffness of the cytoskeleton increases with increasing shear stress as seems typical for living tissue and evidence for an intact cytoskeletal matrix. The particle recoil as measured by the amount of recoverable strain following a short twisting force describes a cytoplasmic elasticity that depends on both level and duration of stress. These investigations on the mechanical properties of living human cells are promising and should lead to better understanding of cellular dysfunction in disease as well as pathways for drug administration.
Insights
Magnetopneumography (MPG) measures lung particle clearance and pulmonary macrophage (PM) mechanics in vivo. This method reveals non-Newtonian cytoplasmic viscosity and cytoskeletal stiffness, offering insights into cellular health and disease.
Area of Science:
- Pulmonary medicine
- Cellular mechanics
- Biophysics
Background:
- Magnetopneumography (MPG) traditionally assesses particle clearance and pulmonary macrophage (PM) motility.
- Understanding the mechanical properties of PMs in vivo is crucial for diagnosing lung diseases.
Purpose of the Study:
- To extend MPG for in vivo measurement of pulmonary macrophage mechanical properties.
- To investigate the non-Newtonian behavior and cytoskeletal mechanics of PMs.
Main Methods:
- Inhaled ferromagnetic microparticles are phagocytized by lung PMs.
- Particles are rotated in magnetic fields to measure cytoskeletal response.
- Macroscopic magnetic fields detect mechanical properties like viscosity and elasticity.
Main Results:
- Pulmonary macrophage cytoplasm exhibits high, non-Newtonian viscosity, behaving as a pseudoplastic fluid.
- Cytoskeletal viscosity and stiffness increase with shear stress, indicating an intact matrix.
- Cytoplasmic elasticity is dependent on stress level and duration.
Conclusions:
- MPG can effectively measure in vivo mechanical properties of pulmonary macrophages.
- Findings provide insights into cellular mechanics relevant to lung health and disease.
- This method holds promise for understanding cellular dysfunction and guiding drug delivery.
