The living shunt: a tissue engineering approach in the treatment of hydrocephalus

Tissue engineering is the use of cultured cells seeded into biodegradable polymers to create custom designed, living implantable devices. As a first approach to the use of this technique in the treatment of hydrocephalus, we have prepared chondrocyte-seeded polyglycolic acid (PGA) tubes coated with polylactic glycolic acid (PGLA), implanted initially with thin silastic stents removed four weeks after shunt insertion. The use of bovine xenograft cells in athymic (nude) rats resulted in more efficient seeding with chondrocytes, stiffer tube walls, and better patency. When implanted in 6-week-old rats made hydrocephalic by cisternal injection of kaolin at 4 weeks of age, six of eight 'living shunts' remained patent to radio-opaque contrast injection at two weeks after stent removal. At four weeks after stent removal, all four of the shunts had occluded at the ventricular end, three of the four apparently due to growth of the animal. We conclude that polymer type, cell type, and cell density will require considerable optimization, but a working tissue engineered shunt is feasible and may one day address some problems of interactions of living tissue and inert polymer.