Biological braids: A machine braids together 48 threads of human extracellular material.
Cytograft has long focused on building replacement blood vessels for people who need dialysis, which cleans the blood of patients with kidney failure. This treatment is severely damaging to the vein (usually in the forearm) through which the patient’s blood is transferred.
Cytograft is not yet testing its woven blood vessels in patients, but it has approximated the needs of dialysis patients in dogs with vessel grafts implanted in their legs. The preclinical dog work has shown that the grafts are resistant to puncture damage and that very little blood leaks from the weave, says L’Heureux.
Cytograft’s implants remain intact after months, suggesting that the body accepts the grafts and does not try to break them down. “Other materials get remodeled very aggressively,” says L’Heureux. “With our tissue, it is so innocuous the body does not see a danger.”
That’s partly because Cytograft’s implants contain no cells. Though the company’s earlier implants were made of extracellular matrix produced from a patient’s own cells, its researchers can now harvest the material from cells unrelated to the person receiving the graft and remove the “donor” cells completely. “We don’t need the cells,” says L’Heureux. “The cells can come from the patients after implantation.”
Without any foreign cells to alert a patient’s immune system, the company could produce blood vessels ahead of time for use in any patient. Such replacement vessels would be less expensive and more readily accessible than what’s available today. “One of Cytograft’s biggest advantages will be off-the-shelf availability,” says Breuer.
The company is also working on a technique in which the cell-produced sheets are processed into particles instead of threads. The biological bits can then be molded together, says L’Heureux, giving tissue engineers two advantages. Molding the particles together leaves a complex network of channels behind—exactly what tissues engineers will need in order to produce, eventually, something like a liver, pancreas, or kidney. With most other technology, there is “no guarantee that the channels will be maintained,” says L’Heureux. The particles could also be injected, he says, which could add volume to tissues for cosmetic or reconstructive purposes.