In a proof-of-concept study using a rabbit model, researchers have successfully regenerated a functioning limb joint grown naturally using the host’s own adult stem cells. Prof. Jeremy J. Mao and his team at Columbia University Medical Center, along with colleagues from the University of Missouri and Clemson University, published their report online in The Lancet. They fabricated an anatomically correct 3-dimensional bioscaffold infused with the protein growth factor TGF3, and implanted the scaffolds into rabbits that had their forelimb thigh joint removed. Other rabbits had scaffolds implanted without the added protein, or no bioscaffold at all. Four weeks later, rabbits that received the protein-laden scaffolds were able to resume normal movements, like rabbits with normal functional joints.

The treated rabbits had grown their own joint using their own adult stem cells. The authors said their findings showed regeneration “without cell transplantation.” The rabbits’ own adult stem cells were attracted to the scaffold joint site by the protein growth factor, “homed” to the location of the missing joint, and regenerated cartilage and bone in two separate layers.

The published results actually show two new findings: regenerating a limb joint for the first time, with the animals resuming normal function with the new joint, and also the regenerated limb joint being created from the animal’s own endogenous stem cells, not stem cells that are harvested and manipulated outside the host’s body. According to Prof. Mao:

This is the first time an entire joint surface was regenerated with return of functions including weight bearing and locomotion. Regeneration of cartilage and bone both from the host’s own stem cells, rather than taking stem cells out of the body, may ultimately lead to clinical applications.”

In an accompanying published commentary, Dr Patrick Warnke of Bond University, Gold Coast, Australia, described the work as “a renaissance of use of the host as a bioreactor and recruitment of the host’s endogenous cells, including stem or progenitor cells, for tissue regeneration”.

Professor Molly Stevens of Imperial College London said:

This is the latest study to have shown that there are stem cells in the body that can be harnessed to grow bone and tissue if they are given the right sort of signals.”