Effects of age and OA on chondrocyte production of IL-7. Media was collected 48 hours after changing to serum-free conditions in chondrocyte cultures established from (a) nonarthritic cartilage from 10 donors of different ages or from (b) cartilage from age-matched nonarthritic (n = 7) and osteoarthritic cartilage (n = 5). IL-7 was measured in the media using ELISA. The relationship of age to IL-7 levels was analyzed by Spearman correlation. The numbers in parentheses above the data points in panel a are the Collin's scores for the donor samples. OA, osteoarthritis.