Modification of cellular gaseous microenvironments on gas-permeable microfluidic chips

The decreased oxygen availability activates the cells' hypoxia- inducible factor (HIF) pathway. HIF is a critical mediator of physiological responses in acute and chronic hypoxia. Conventional hypoxia chambers, which are widely employed to study hypoxia, are cumbersome and require large gas supply volumes. The high diffusivity of gases makes it impossible to control the local gaseous microenvironments in hypoxia chambers. In this study, microfluidic chips were utilized to create oxygen gradients in nano and micro scales to act as gaseous microenvironments for cell cultures. It was observed that by pumping an oxygen scavenger solution in the microfluidic channels, the hypoxia response increased in the adherent cells on the microchip system. A simultaneous cellular gaseous microenvironment for hypoxia and nitric oxide was created by utilizing a microfluidic channel architecture with two sets of microchannels. One of the channels was filled with the oxygen scavenger solution and the other with a nitric oxide donor (sodium nitroprusside, SNP). The channels then guided these treatments to selected areas of the cell culture. We showed that microfluidics could target the specific region in the chip and modify microenvironmental gases in the cells. At the same time, the other cultural area remained unchanged. A simultaneous cellular response to hypoxia and nitric oxide was obtained after 100 min pumping with a flowrate of 1.6 μl/min. Preeclampsia (PE) is a pregnancy disorder where hypoxia plays a crucial role in the pathophysiology. To mimic a preeclampsia (PE) microenvironment, an oxygen scavenger solution was pumped through the microfluidic channels of a Myogel-coated microchip on which JEG-3 choriocarcinoma cells were cultured as a human trophoblast model for 24h. RNAseq data of the cells from the microchip showed gene expression differences and pathways that were affected by hypoxia; among those were MYC targets, E2F targets, G2-M checkpoint, and the unfolded protein response. Based on our data, the hypoxia created by the microchip caused significant transcriptional changes in JEG-3 cells.