Considerations on the use of ear chondrocytes as donor chondrocytes for cartilage tissue engineering

Articular cartilage is often used for research on cartilage tissue engineering. However, ear cartilage is easier to harvest, with less donor-site morbidity. The aim of this study was to evaluate whether adult human ear chondrocytes were capable of producing cartilage after expansion in monolayer culture. Cell yield per gram of cartilage was twice as high for ear than for articular cartilage. Moreover, ear chondrocytes proliferated faster. Cell proliferation could be further stimulated by the use of serum-free medium with Fibroblast Growth Factor 2 (FGF2) in stead of medium with 10% serum. To evaluate chondrogenic capacity, multiplied chondrocytes were suspended in alginate and implanted subcutaneously in athymic mice. After 8 weeks the constructs demonstrated a proteoglycan-rich matrix that contained collagen type II. Constructs of ear chondrocytes showed a faint staining for elastin. Quantitative RT-PCR revealed that expression of collagen type II was 2-fold upregulated whereas expression of collagen type I was 2-fold down regulated in ear chondrocytes expanded in serum-free medium with FGF2 compared to serum-containing medium. Expression of alkaline phosphatase and collagen type X were low indicating the absence of terminal differentiation. We conclude that ear chondrocytes can be used as donor chondrocytes for cartilage tissue engineering. Furthermore, it may proof to be a promising alternative cell source to engineer cartilage for articular repair.