When AF cells derived from degenerative tissue were subjected to 1.0-Hz CTS, the observed response, reduced relative gene expression of the matrix proteins aggrecan and type I collagen, did not appear to involve either IL-1 or IL-4 as demonstrated by the inability of the cytokine inhibitors IL-1Ra and IL-4RAb to prevent the CTS-induced changes in gene expression. Here, IL1A is linked to atrial fibrillation.