Hybrid devices that are part machine, part living cells offer new hope to patients with kidney problems for whom purely artificial treatments like dialysis aren’t good enough.

A “bioartificial kidney,” being developed by Nephros Therapeutics, is based on a plastic cartridge containing one billion human kidney cells thriving inside 4,000 translucent, hollow, plastic fibers. It is based on a decade of research by University of Michigan internist David Humes.

The real revolution will come with the development of permanent, implantable bioartificial organs that allow the cells to receive nourishment from the body but still protect them from attacks by the recipients’ immune systems.