Engineered Systems for Controlled Hypoxia and Thermogenesis

Cells adapt to microenvironmental alterations in oxygen levels and temperature by shifting metabolic processes and initiating transcriptional programs. Engineered systems have been developed to probe the biological responses of cells to their microenvironment. Our microfluidic platforms for gas control have allowed us to generate oxygen landscapes and gradients found in the physiological setting as a result of metabolic consumption and oxygen transport limitations. For gas control, we studied the hypoxic activation of the hypoxia inducible factor (HIF) family of transcription factors HIF-1α and HIF-2α in human endothelial cells, and we demonstrated differential hypoxic activation of HIF-1α and HIF-2α in a spatial linear oxygen gradient. Our temperature control studies have focused on nonshivering thermogenesis in human subcutaneous adipocytes. We used a ratiometric cell-permeable thermoprobe to demonstrate intracellular heat generation in adipocytes. Demonstrable single-cell thermogenesis during cold exposure allowed study of the requirement of glucose in cold-induced thermogenesis. Additionally, one of the fundamental questions in studying temperature-regulated transcription in human adipose tissue is whether cold-exposed cells in proximity to the skin surface undergoing browning release paracrine factors that induce the transcriptional program for conversion of adipocytes in deeper layers of fat which are not being directly exposed to cold. For this purpose, we developed an engineered system which generates temperature gradients and allows us to study paracrine interactions between warm and cold fat cells. Our findings suggest adipocytes exposed to cold temperature may modulate cellular responses in neighboring warm cells.