It is becoming ever more common these days to see news of proof of concept work for the engineering of specific tissue structures throughout the body. Here is a recent example:
In developing tissue-engineered gut replacements the researchers use smooth muscle and nerve stem cells from human intestine to engineer innervated muscle sheets. The sheets are then wrapped around tubular chitosan scaffolds. The tubular structures were implanted just under the skin of rats for 14 days, a first step in assessing their performance. Researchers found that the implants developed a blood vessel supply and that the tube opening was maintained. In addition, the innervated muscle remodeled as the cells began the process of releasing their own materials to replace the scaffold. "It is the combination of smooth muscle and neural cells in gut tissue that moves digested food material through the gastrointestinal tract and this has been a major challenge in efforts to build replacement tissue. Our preliminary results demonstrate that these cells maintained their function and the implant became vascularized, providing proof of concept that regenerating segments of the gastrointestinal tract is achievable."
The group's second project, to engineer anal sphincters, also reached a new milestone with the successful implantation of the structures in rabbits. Sphincters are ring-like muscles that maintain constriction of a body passage, such as controlling the release of urine and feces. There are actually two sphincters at the anus - one internal and one external. A large proportion of fecal incontinence in humans is the result of a weakened internal sphincter.
To engineer the internal anal sphincters, researchers used a small biopsy from the animals' sphincter tissue and isolated smooth muscle cells that were then multiplied in the lab. In a ring-shaped mold, these cells were layered with nerve cells isolated from small intestine to build the sphincter. The mold was placed in an incubator, allowing for tissue formation. The entire process took about four to six weeks. The bioengineered sphincters mimicked the architecture and function of native tissue and there are no signs of inflammation or infection after implantation. The constructs demonstrated the presence of contractile smooth muscle as well as mature nerve-cell populations. The bioengineered sphincters restored fecal continence in the animals throughout the six-month follow-up period after implantation.