Characteristics of cartilage engineered from human pediatric auricular cartilage

In the repair of cartilage defects, autologous tissue offers the advantage of lasting biocompatibility. The ability of bovine chondrocytes isolated fr om hyaline cartilage to generate tissue-engineered cartilage in a predeterm ined shape, such as a human ear, has been demonstrated; however, the potent ial of chondrocytes isolated from human elastic cartilage remains unknown. In this study, the authors examined the multiplication characteristics of h uman auricular chondrocytes and the ability of these cells to generate new elastic cartilage as a function of the length of time they are maintained i n vitro. Human auricular cartilage, harvested from patients 5 to 17 years of age, wa s digested in collagenase, and the chondrocytes were isolated and cultured in vitro for up to 12 weeks. Cells were trypsinized, counted, and passaged every 2 weeks. Chondrocyte-polymer (polyglycolic acid) constructs were crea ted at each passage and then implanted into athymic mice for 8 weeks. The a bility of the cells to multiply in vitro and their ability to generate new cartilage as a function of the time they had been maintained in vitro were studied. A total of 31 experimental constructs from 12 patients were implan ted and compared with a control group of constructs without chondrocytes. I n parallel, a representative sample of cells was evaluated to determine the presence of collagen. The doubling rate of human auricular chondrocytes in vitro remained constan t within the population studied. New tissue developed in 22 of 31 experimen tal implants. This tissue demonstrated the physical characteristics of auri cular cartilage on gross inspection. Histogically, specimens exhibited dens e cellularity and lacunae-containing cells embedded in a basophilic matrix. The specimens resembled immature cartilage and were partially devoid of th e synthetic material of which the construct had been composed. Analyses for collagen, proteoglycans, and elastin were consistent with elastic cartilag e. No cartilage was detected in the control implants. Human auricular chondrocytes multiply well in vitro and possess the ability to form new cartilage when seeded onto a three-dimensional scaffold. These growth characteristics might some day enable chondrocytes isolated from a small auricular biopsy to be expanded in vitro to generate a large, custom- shaped, autologous graft for clinical reconstruction of a cartilage defect, such as for congenital microtia.