MMP1 and atrial fibrillation: CTS stimulation upregulated collagen type I (COL1A1) expression, while IL-1β significantly stimulated IL-6, IL-8, MMP-1, and MMP-3 gene expression and prostaglandin E2 production by AF cells but downregulated COL1A1. The combination of CTS + IL-1β had a similar outcome as IL-1β alone, accompanied by a significant upregulation of elastin.