The mitogenic potential of human NP and AF cells can be stimulated by platelet-derived growth factor, basic fibroblast growth factor, and insulin-like growth factor-1 (IGF-1).132–135 Delivering BMP-7 with IGF-1 synergistically stimulated proteoglycan synthesis and cell proliferation from bovine NP cells.136 Injecting BMP-7 alone into degenerated rabbit discs provides an initial benefit by restoring disc height.137 However, no beneficial effects were detected by histology, suggesting that a single injection may result in transient effects that should be further optimized. This evidence concerns the gene IGF1 and atrial fibrillation.