US scientists have shown kidney cells can survive and function in an artificial organ implanted in a pig. The cells tested served only to regulate water levels but the idea is eventually to populate the “bioreactor” with the myriad different sorts of cells that work together in a kidney and pair it with a second device to filter waste products from the blood. The result should be an implantable artificial kidney to end the need for regular dialysis for many of the 500,000 people in the US alone who need it several times a week. Of those 500,000, only 20,000 a year are offered a transplant. The pig-based study was by the Kidney Project at UC San Francisco. A key question was whether the implant could function without immunosuppressant drugs. It could.