Microfluidic platform for chemotaxis in gradients formed by CXCL12 source-sink cells

Abstract

Chemokine CXCL12 promotes CXCR4-dependent chemotaxis of cancer cells to characteristic organs and tissues, leading to metastatic disease. This study was designed to investigate how cells expressing CXCR7 regulate chemotaxis of a separate population of CXCR4 cells under physiologic conditions in which cells are exposed to gradients of CXCL12. We recapitulated a cancer-stroma microenvironment by patterning CXCR4-expressing cancer cells in microchannels at spatially defined positions relative to CXCL12-producing cells and CXCR7-expressing cells. CXCR7 scavenges and degrades CXCL12, which has been proposed to facilitate CXCR4-dependent chemotaxis through a source-sink model. Using the microchannel device, we demonstrated that chemotaxis of CXCR4 cells depended critically on the presence and location of CXCR7 cells (sink) relative to chemokine secreting cells (source). Furthermore, inhibiting CXCR4 on migrating cells or CXCR7 on sink cells blocked CXCR4-dependent chemotaxis toward CXCL12, showing that the device can identify new therapeutic agents that block migration by targeting chemoattractant scavenging receptors. Our system enables efficient chemotaxis under much shallower yet more physiological chemoattractant gradients by generating an in vitro microenvironment where combinations of cellular products may be secreted along with formation of a chemoattractant gradient. In addition to elucidating mechanisms of CXCL-12 mediated chemotaxis, this simple and robust method can be broadly useful for engineering multiple microenvironments to investigate intercellular communication.

A paper-based invasion assay: Assessing chemotaxis of cancer cells in gradients of oxygen

“…This paper-based assay has several attractive characteristics (9)(10)(11)(19)(20)(21)(22)(23) Current in vitro studies of cellular response to changes in concentrations of oxygen rely on hypoxia chambers, which regulate the bulk concentration of oxygen to which a culture of cells is exposed. Furthermore, hypoxia chambers do not generating gradients of oxygen to study chemotaxis.…”

“…This lack of experimental data is due largely to the difficulty in controlling and measuring gradients of oxygen in living tissue, and to the difficulty associated with analyzing the migratory response of cells in conventional model systems (both in vivo and in vitro) (7)(8)(9)(10)(11). These mathematical models predict that asymmetric gradients of oxygen and other small molecules such as glucose can cause differential rates of proliferation of cells in a tumor, and these gradients ultimately contribute to the formation of primary tumors with irregular shapes (5).…”

“…There are a number of methods to assess cellular migration and invasiveness in vitro (9)(10)(11)(19)(20)(21)(22)(23); these methods rely on quantifying movement across two-dimensional (2D) substrates or through three-dimensional (3D) gels. The concentration gradient of small molecules can be controlled temporally and spatially (at length scales of tens of microns, which is the scale of a single cell) in a microfluidic device (7,8,(24)(25)(26)(27)(28).…”

Microvalve and liquid membrane double-controlled integrated microfluidics for observing the interaction of breast cancer cells

“…Moreover, the method also prevents mechanical damage to cells from scraping. However, this method is unsuitable for non-attached cell migration and it is limited by the potential enzymatic damage to cells (Collett et al 2007;Murrell et al 2011). (3) Cell patterning, i.e., the distribution of cells in designated areas with special shapes via physical or chemical methods Torisawa et al 2010). Using this method, cell populations can be spatially positioned with parallel edges.…”

A Perspective on Studying G-Protein–Coupled Receptor Signaling with Resonance Energy Transfer Biosensors in Living Organisms

“…The flow they provide not only mimics blood flow, thereby distributing oxygen and nutrients and removing waste products, but also simulates the shear stress experienced by many cell types, which has been shown to induce GPCR signaling (Storch et al, 2012). Moreover, microfluidics can be used to change agonist levels, create chemical gradients, or apply mixtures of soluble cues to investigate their effect on GPCR-mediated signaling (Torisawa et al, 2010).…”