Injection molding of chondrocyte/alginate constructs in the shape of facial implants

Over one million patients per year undergo some type of procedure involving cartilage reconstruction. Polymer hydrogels, such as alginate, have been s hown to be effective carriers for chondrocytes in subcutaneous cartilage fo rmation. The goal of our current study was to develop a method to create co mplex structures (nose bridge, chin, etc.) with good dimensional tolerance to form cartilage in specific shapes. Molds of facial implants M ere prepar ed using Silastic ERTV. Suspensions of chondrocytes in 2% alginate were gel led by mixing with CaSO4, (0.2 g/mL) and injected into the molds. Construct s of various cell concentrations (10, 25, and 50 million/mL) were implanted in the dorsal aspect of nude mice and harvested at times up to 30 weeks. A nalysis of implanted constructs indicated progressive cartilage formation w ith time. Proteoglycan and collagen constructs increased with time to appro ximately 60% that of native tissue. Equilibrium modulus likewise increased with time to 15% that of normal tissue, whereas hydraulic permeability decr eased to 20 times that of native tissue. Implants seeded with greater conce ntrations of cells increased proteoglycan content and collagen content and equilibrium and decreased permeability. Production of shaped cartilage impl ants by this technique presents several advantages, including good dimensio nal tolerance, high sample-to-sample reproducibility, and high cell viabili ty. This system may be useful in the large-scale production of precisely sh aped cartilage implants. (C) 2001 John Wiley & Sons, Inc.