Cell-cell communication between adipocytes and pancreatic beta-cells in acoustically levitated droplets

Dysfunctional adipocytes and insulin-producing pancreatic beta-cells are hallmarks of human Type 2 diabetes and play important roles in the onset and progression of the disease. However, the precise mechanisms involved are complex and only partially understood. Here we present a new and unique method to perform single-cell and cell-cell communication studies in Type 2 diabetes-related research. The airborne analytical system offers "contactless" sample handling in the sub-microlitre volume range and is here equipped with fluorescence imaging detection. The system utilizes acoustically levitated droplets as "wall-less" test tubes and in-house constructed piezoelectric flow-through picolitre droplet dispensers for precise reagent supply. Hormone-mediated regulation of adipocyte lipolysis and communication between adipocytes and beta-cells can be studied at the few-cell level. Thus, lipolysis could be detected in single adipocytes, whether it was induced by isoprenaline or inhibited by insulin. Furthermore, the airborne system allowed the comparison of lipolysis in adipocytes of different sizes: a large adipocyte responded more slowly than a small cell. Furthermore, stimulation of insulin secretion by high glucose or acetylcholine administration to a levitated drop containing insulin-producing beta-cells resulted in inhibition of isoprenaline-induced lipolysis in adipocytes present in the same drop. The results show the applicability of the airborne analytical system for single cell analysis and for cell-cell communication studies as well as the potential for future analysis directly from human cells obtained from clinical biopsies.