Continuous, noninvasive monitoring of local microscopic inflammation using a genetically engineered cell-based biosensor

Using an inflammation-responsive regulatory element as a molecular sensor, we established a cell-based biosensor for continuous, noninvasive monitoring of local microscopic inflammation in vivo. Glomerular mesangial cells were stably transfected with a marker gene encoding secreted alkaline phosphatase (SEAP) under the control of the kappa B enhancer elements. The established cells secreted SEAP in vitro in response to proinflammatory cytokines as well as to soluble factors produced by inflamed glomeruli. To examine feasibility of using the established cells for in vivo monitoring of local microscopic inflammation, the sensor cells were transferred selectively into rat glomeruli via the renal circulation. After induction of acute glomerulonephritis, the serum level of SEAP was increased transiently in cell-transferred nephritic rats. The kinetics of serum SEAP was closely correlated with the natural course of the inflammation, and the increase in SEAP was attenuated by suppression of inflammation using an immunosuppressive drug, cyclophosphamide. Neither cell-transferred normal rats nor nephritic rats without cell transfer exhibited increase in the serum level of SEAP. When the sensor cells were transferred extrarenally, elevation of serum SEAP was not observed in nephritic rats, confirming that the locally settled sensor cells responded only to local inflammation. These results suggested that, without invasive procedures like tissue biopsies, continuous monitoring of microscopic inflammation is feasible in vivo via locally created, cell-based biosensors.