Cell Culture Under Flow: Applications and Experimental Examples

This page summarizes common wall shear stress assay applications and cell culture under flow applications for adherent cells exposed to defined mechanical stimulation under controlled in vitro conditions. It is intended for researchers planning endothelial, epithelial, vascular co-culture, immune cell interaction, and mechanotransduction studies under flow.

Depending on the biological question, cells can be cultured as 2D monolayers under flow, in matrix-based 3D models, or as co-cultures on an optical porous membrane. This page connects these assay formats with experimental examples and suitable ibidi solutions.

Staining of spheroids (blue, red) and HUVECs (green) after 3 days in co-culture under perfusion. Cell nuclei: DAPI (blue); actin filaments: Phalloidin-iFluor 647 (red); CD31: Alexa Fluor 488 labeled anti-CD31 antibody (green).

Wall Shear Stress Assay Formats and Selection Guide

Wall shear stress assay formats model the mechanical forces generated by fluid flow in biofluidic systems, including blood vessels, lymphatic vessels, kidney tubules, and epithelial channels. The optimal format depends on the biological question, cell type, culture substrate, extracellular matrix, optional co-culture or gel-embedded cells, flow profile, and planned readout.

In vivo, vascular endothelial cells and selected epithelial barriers, such as kidney tubules, airway, gut, or ductal epithelia, are exposed to fluid flow and flow-related mechanical cues. In static cell culture, this mechanical stimulus is missing. 2D cell monolayers under flow can be cultured on optically suitable surfaces, membranes, or custom device substrates and exposed to defined shear stress. This format is commonly used to study flow-dependent cell morphology, alignment, cytoskeletal organization, adhesion properties, gene expression, barrier function, and inflammatory responses.

Many cells interact with extracellular matrix proteins in vivo, and these matrix cues strongly influence adhesion, migration, morphology, signaling, and tissue-like organization. Matrix-based 3D models under flow combine defined perfusion or wall shear stress with an extracellular matrix or gel environment. Depending on the experimental design, cells can be cultured on top of the matrix, embedded within the gel, perfused through the flow channel, or combined with spheroids or organoid-like structures. This format is especially useful for studying angiogenesis under flow, capillary-like structure formation, tumor–stroma interaction, immune cell recruitment, trans-endothelial migration, intra- or extravasation, matrix penetration, and drug delivery in 3D microenvironments.

Suspension cells: Depending on the model, suspended cells (e.g., leukocytes, erythrocytes, platelets) can be perfused over an adherent cell layer or through a flow channel to study rolling, adhesion, cell–cell interaction, or trans-endothelial migration.

Which Application Fits My Research Question?

Use the application field, cell cultivation model, and planned readout to identify a suitable ibidi solution for your flow assay.

Endothelial Mechanobiology and Vascular Flow Conditioning

Endothelial cells are highly sensitive to wall shear stress. Defined laminar flow can be used to condition endothelial monolayers and to analyze morphology, alignment, cytoskeletal organization, junction formation, inflammatory signaling, gene expression, and mechanotransduction.

Culturing Human Umbilical Vein Endothelial Cells (HUVECs) Under Flow

Immunofluorescence staining allows the comparison of static and flow-cultured endothelial cells and can reveal differences in cytoskeletal organization. In this example, flow-conditioned HUVECs were stained against VE-cadherin and compared with static cultures.

VE-cadherin staining highlights adherens junctions in both static and flow-conditioned HUVECs. Under static conditions, the cells are generally larger and show a less organized actin cytoskeleton. In contrast, flow-conditioned cells are elongated and display distinct F-actin stress fibers, indicating flow-dependent reorganization of the endothelial cell layer.

HUVECs were cultured for 5 days under static conditions in a µ-Dish ^{35 mm, high} ibiTreat (top, 0 dyn/cm²) or under flow at 10 dyn/cm² (bottom) in a µ-Slide I ^0.4 Luer ibiTreat, using the ibidi Pump System. The cells were stained for VE-cadherin (green), F-actin (red), and nuclei (blue). Imaging was performed using a Nikon Eclipse microscope at 60× magnification.

Culturing Pulmonary Endothelial Cells (HPMECs) Under Shear Stress

When cultured under flow, human pulmonary microvascular endothelial cells (HPMECs) show changes in morphology, cytoskeletal organization, and endothelial cell–cell contacts compared with static culture. This example demonstrates how phase contrast and fluorescence microscopy can be used to assess endothelial responses to defined shear stress conditions.

Phase contrast microscopy (top, scale bars: 200 µm) and fluorescence microscopy (bottom, scale bars: 100 µm) of HPMECs comparing static culture (left) and flow culture (right) after 72 h in the µ-Slide I ^0.6 Luer, coated with Collagen IV. A flow of 2.3 dyn/cm² was applied using the ibidi Pump System. Fluorescence labels: β-actin (green), VE-cadherin (red), and DAPI (blue). Data by Daniel Bourquain, Robert Koch Institute, Berlin.

Atherosclerosis and Vascular Inflammation

Atherosclerosis-related mechanisms are strongly linked to local flow patterns. Non-uniform, oscillatory, or disturbed-flow-like conditions can be used to analyze endothelial activation, inflammatory signaling, monocyte adhesion, mechanosensitive membrane domains, and vascular dysfunction.

Disturbed-Flow and y-Shaped Channel Setups

The µ-Slide y-shaped can be used to create spatially different shear stress conditions in a single sample. This enables the comparison of endothelial behavior under different flow environments and supports assays related to vascular inflammation and atherosclerosis.

Typical Readouts

• Monocyte adhesion and endothelial activation
• Cell alignment and morphology
• Inflammatory marker expression
• Mechanotransduction and calcium signaling
• Barrier-related changes under disturbed flow

Leukocyte Recruitment and Immune-Cell Interaction

Flow assays are widely used to study leukocyte rolling, adhesion, and transmigration. In these assays, immune cells are perfused over an activated endothelial monolayer, a protein-coated surface, a membrane, or a matrix-based model. Readouts can include rolling velocity, adhesion count, transmigration events, and live cell tracking.

Rolling and Adhesion Assay Under Defined Shear Stress

Rolling and adhesion assays are commonly used to analyze leukocyte–endothelial interactions under flow. In this example, cerebrovascular endothelial cells (CVECs) were cultured as a 2D endothelial monolayer in the µ-Slide VI ^0.4 and stimulated with LPS to induce an inflammatory endothelial phenotype. Granulocytes were then perfused over the activated endothelial layer using the ibidi Pump System at 1 dyn/cm², enabling live microscopic analysis of granulocyte rolling, adhesion, and cell–cell interactions under defined shear stress.

Rolling and adhesion assay with granulocytes perfused over an LPS-stimulated cerebrovascular endothelial cell monolayer in the µ-Slide VI ^0.4. The assay enables visualization of leukocyte–endothelial interactions under defined shear stress. Image courtesy of Gediminas Cepinskas, University of Western Ontario, Canada.

Barrier Models and Permeability

Barrier models under flow are used to study endothelial or epithelial barrier integrity, permeability, compound transport, and immune-cell transmigration. Depending on the model, cells can be cultured on a membrane, on a channel surface, or in combination with a 3D matrix.

A Dynamic Blood–Brain Barrier Model for Microscopy and Permeability Analysis

The blood–brain barrier is a highly selective vascular interface that restricts drug entry into the brain, making physiologically relevant in vitro models essential for permeability testing and CNS drug development. In this study by Choublier et al., the authors developed a custom two-compartment BBB device in which hCMEC/D3 brain endothelial cells were cultured on a semi-permeable membrane and exposed to uniform laminar shear stress using the ibidi Pump System. The setup enabled long-term endothelial culture under flow, direct microscopy-based analysis of barrier morphology and junction markers, and permeability measurements under static and dynamic conditions.

Schematic representation of a dynamic blood–brain barrier model for microscopy and permeability analysis. Brain endothelial cells were cultured on a semi-permeable membrane in a custom two-compartment device and perfused under uniform laminar shear stress using the ibidi Pump System. Adapted from: Choublier N, et al. (2021), doi:10.3390/app11125584, licensed under CC BY 4.0.

Tumor Microenvironment, Extravasation, and Drug Delivery

Perfused tumor microenvironment models can combine endothelial layers, immune cells, tumor spheroids, hydrogel matrices, and dynamic compound delivery. These models are suitable for studying extravasation, immune-tumor interaction, carrier penetration, drug accumulation, and viability under flow.

Monocyte-Mediated Drug Delivery in a 3D Tumor Model Under Flow

Immune cell trafficking offers a promising route to improve drug delivery into solid tumors, where vascular barriers and dense extracellular matrices often limit passive nanoparticle accumulation. In this study by Chang et al., the authors developed monocyte-adhesive peptidyl liposomes, referred to as monocyte-mediated drug carriers (MMDCs), designed to hitchhike on circulating monocytes. Using ibidi flow-based assays, they first analyzed the interaction between MMDCs and monocytes under defined shear stress. They then established a 3D tumor microenvironment model with collagen-embedded tumor spheroids and an endothelial barrier to investigate monocyte adhesion, trans-endothelial migration, and selective MMDC accumulation in cancer-containing matrices under dynamic flow conditions.

Schematic illustration of MMDC-assisted monocyte homing in a 3D tumor microenvironment model under flow. The setup enabled analysis of monocyte adhesion, trans-endothelial migration, and tumor-directed carrier accumulation. Graphical abstract created by ibidi, based on: Chang CY, et al. (2025), doi:10.1016/j.jconrel.2025.113672.

PD-L1-Targeted Immunoliposomes in a Cervical Cancer-on-a-Chip Model

Cancer-on-a-chip models provide a controlled approach to study how therapeutic nanocarriers behave in a 3D tumor-like environment under perfusion. In this study by Fobian et al., PD-L1-targeted immunoliposomes were investigated in a dynamic cervical cancer model combining tumor spheroids, an extracellular matrix, and defined flow. The setup allowed the authors to assess how flow influences immunoliposome transport, penetration into the 3D matrix, and delivery toward PD-L1-expressing tumor cells in a more physiologically relevant in vitro system.

Schematic representation of a dynamic cervical cancer-on-a-chip model for studying PD-L1-targeted immunoliposome delivery. Tumor spheroids were embedded in an extracellular matrix and exposed to controlled perfusion, enabling the analysis of nanocarrier transport, matrix penetration, and tumor-associated accumulation under flow. Reproduced from: Fobian SF, et al. (2025), doi:10.1016/j.jconrel.2025.01.014, licensed under CC BY 4.0.

Additional Application Fields

The following application fields can also benefit from controlled wall shear stress or flow-based culture. Depending on the model, these fields may require a 2D monolayer, a membrane-based setup, or a matrix-based 3D culture format.

Monolayer Co-Culture on a Porous Membrane Under Flow

Porous membrane co-culture assays under flow enable the cultivation of two cell layers in separate but interacting compartments. One cell monolayer can be exposed to flow while soluble factors, cell–cell communication, or barrier-related responses are analyzed across the membrane. This assay format is suitable for endothelial and epithelial barrier models, vascular co-culture systems, immune cell interaction studies, and microscopy of living or fixed cell layers under defined shear stress conditions.

Transmigration of cells across a cell monolayer on the membrane into a 3D gel matrix with embedded cells using the µ-Slide ibiPore SiN.