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Cell membrane alignment along adhesive surfaces: contribution of active and passive cell processes
Anne Pierres1, Philippe Eymeric, Emmanuelle Baloche
1INSERM U387, Laboratoire d'Immunologie, Hôpital de Ste-Marguerite, BP 29, 13274 Marseille Cedex 09, France.
This study examined how monocytic THP-1 cells align with adhesive surfaces before spreading. Researchers used interference reflection microscopy to track early contact formation and found that cells form irregular-shaped zones within minutes. These zones were confirmed as adhesion sites since they resisted hydrodynamic forces. The study showed that passive membrane deformations and adhesive forces are enough to initiate alignment. Cytoskeletal activity accelerated the process but was not essential. Hypotonic medium increased the speed of contact extension, while microfilament blockade and cell fixation reduced it. Despite these changes, cells remained adhesive. The findings suggest that both passive and active processes contribute to initial cell-surface alignment.
Area of Science:
- Cell adhesion mechanisms in biomedical engineering
- Membrane biophysics in cell biology
Background:
Understanding how cells align with surfaces is essential for studying adhesion processes. Prior research has shown that cell adhesion involves nanoscale interactions between receptors and substrates. However, the exact mechanisms of initial membrane alignment remain unclear. No prior work had resolved the role of active and passive cellular processes in this alignment. This gap motivated the need for a detailed, quantitative study. Existing methods often overlook the early stages before full cell spreading. Researchers have not fully characterized the contribution of cytoskeletal activity or membrane deformability. This study aims to address these uncertainties by combining multiple imaging and mechanical techniques.
Purpose Of The Study:
The goal was to investigate the initial stages of cell-surface alignment. Researchers focused on monocytic THP-1 cells interacting with adhesive surfaces. They aimed to distinguish between active and passive contributions to this process. The study examined membrane alignment before full cell spreading occurs. They used interference reflection microscopy to track early contact formation. Micropipette aspiration and laminar flow assays were also employed. The motivation was to determine if adhesion could proceed without active cytoskeletal involvement. This work sought to clarify the role of passive membrane deformations in adhesion.
Main Methods:
The team used interference reflection microscopy to observe cell-surface interactions. They tracked the formation of irregular-shaped contact zones in real time. Micropipette aspiration measured cell deformability during these interactions. A laminar flow assay assessed adhesiveness by applying hydrodynamic forces. Cells were treated with cytochalasin to block microfilaments. Paraformaldehyde fixation was used to test for passive alignment. Hypotonic medium was applied to increase membrane flexibility. The study compared control and treated cells to isolate active and passive contributions.
Main Results:
Initial contact zones formed within minutes of cell-substrate interaction. These zones reached approximately 100 micrometers squared in area. The margin extension velocity was between 0.01 and 0.02 micrometers per second. These zones were confirmed as adhesion sites since cells resisted hydrodynamic forces. Microfilament blockade reduced but did not eliminate alignment. Fixed cells still showed some alignment, though less than controls. Hypotonic medium increased the rate of contact extension. Contact shapes in treated cells were more regular and matched deformability data.
Conclusions:
The study suggests that passive membrane deformations can drive initial alignment. Adhesive forces alone appear sufficient for early contact formation. Spontaneous cytoskeletal motion accelerates this process. Alignment is not entirely dependent on active cell processes. The findings support a dual mechanism involving both passive and active contributions. Membrane flexibility plays a key role in contact extension. The shape of contact zones reflects cell deformability. These conclusions align with the observed effects of various treatments on alignment.
Frequently Asked Questions
The study shows that passive membrane deformations and adhesive forces are sufficient for initial alignment, with cytoskeletal activity accelerating the process.
They used micropipette aspiration to assess how easily cells could deform during contact formation.
Hypotonic conditions likely increased membrane flexibility, allowing faster alignment with the substrate.
It was used to visualize and track the formation of contact zones between cells and adhesive surfaces.
No, it reduced alignment but did not abolish it, suggesting passive processes still contributed.
Active processes are not essential for initial alignment, but they enhance the rate of membrane extension.