Evidence of chondrocyte turnover in lung cartilage, with the probable participation of nestin-positive cells.

Healthy adult cartilage is thought to have little or no capacity to renewal, and cell turnover has not been reported in lung cartilage. We report that chondrocyte turnover occurs in lung cartilage, found in an unrelated study. Lung specimens from CD1 mice of 2, 6, 12, 18 or 24 months were fixed in 10% neutral-buffered formalin and paraffin-embedded. Apoptosis was analysed by in situ end-labelling of fragmented DNA. Proliferating cell nuclear antigen (PCNA) and nestin were examined by immunohistochemistry. Apoptosis and PCNA were detected in lung chondrocytes. Serial section analysis showed that cells in apoptosis were different from PCNA-positive cells, indicating that turnover was occurring. Chondrocytes were negative for nestin. Nestin-positive cells were present in connective tissue associated with cartilage, in some specimens in close proximity of it and in perivascular cells. Thus cell turnover in lung cartilage is possible, which may be mediated by nestin-positive cells.