Bioprinting is only one path toward the goal of tissue regeneration: using a patient’s own cells (or stem cells from other people) to repair or replace a major organ such as a kidney, liver or heart.

It’s likely that no single approach will work for everyone in need, said Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, so researchers are pursuing several methods:

- Making tissues in a mold: Cells from the patient’s tissue are placed on a detailed, organ-shaped scaffold surrounded by a mold. Once the replacement organ is transferred to the patient, the new tissue integrates with the body. Bladders and urethras have been engineered using this technique; a few people have had replacement bladders for more than a decade.

- Inserting tissue “wafers”: In theory, a surgeon could place a piece of lab-grown tissue into a failing kidney, almost instantly boosting the organ’s function enough to keep a patient off dialysis. Researchers are testing this theory by implanting such tissue in cattle.

- Reupholstering unused donor organs: Not all donated organs can be used, for various reasons. Scientists think they can salvage the leftovers by washing cells away, leaving the scaffolding that holds the organ together — including the all-important blood vessels. They would then populate the scaffold with newly grown cells from the patient, so the body would recognize the refurbished organ as its own.

- Injecting stem cells: Because environmental cues determine what stem cells become, injecting a patient’s own stem cells into a low-functioning liver or kidney might provide enough new liver or kidney cells to improve the organ’s function enough for the patient to avoid dialysis.

- Helping the organ regenerate itself: All our tissues replace themselves at different rates. We have a new stomach lining every six days and all new bones every 10 years. So the theory goes that if you can improve the “microenvironment” inside a sick organ by injecting proteins, growth factors and other helpful substances, diseased cells will naturally be replaced by healthy ones.

Bonnie Berkowitz