Microfluidic one-directional interstitial flow generation from cancer to cancer associated fibroblast

Tumors, unlike normal tissue, have vascular anomalies and create interstitial flow (IF), which allows soluble substances from cancer cells to be transported directionally toward the tumor stroma. In the stroma, IF activates fibroblasts. Cancer-associated fibroblasts (CAFs) are formed from stimulated cells and aid cancer growth. A microfluidic device was designed to generate a one-directional flow of a small volume mimicking IF from donor cells to recipient at steady-state conditions only based on the medium evaporation from reservoirs with different diameter. The IF carried substances from donor cells, which stimulated the activation of fibroblasts on the receiving side, as well as their migration and stellate formation. Matrix metallopeptidases 9 and 14 as well as CAF markers such as fibroblast activation protein alpha, vimentin, and alpha-smooth muscle actin are abundantly expressed in the migrating fibroblasts. The created platform mimicked one-directional delivery in tumor stroma. This will allow researchers to investigate how cancer cells activate and differentiate stromal cells. STATEMENT OF SIGNIFICANCE: We show how to provide continuous one-directional interstitial flow (IF) in a microfluidic device without using any power source and instrumentation. This microfluidic technology was used to simulate the tumor microenvironment. Fibroblasts in the tumor stroma are activated and migrated toward cancer cells, as recapitulated by co-culture of cancer cells as donor and fibroblasts as recipient under the one-directional IF. We believe that soluble substances from cancerous cells delivered by the one-directional IF efficiently regulated the development of cancer-associated fibroblasts (CAFs),  as shown by increasing roundness and decreased circularity, taking on a stellate morphology, and by enhanced invasion into a type I collagen hydrogel. Migrating fibroblasts into the hydrogel had significant levels of MMP-9, MMP-14, FAP, vimentin, and αSMA, all of which are CAF markers, bearing a capacity to form hot stroma affecting tumor malignancy.