The expression of runx2 (runt-related transcription factor 2, a key transcription factor of osteoblast differentiation), bmp-2 (bone morphogenetic protein 2, an important growth factor in bone and cartilage development), and osteopontin were markedly increased in AF cells treated with osteogenic medium compared to that treated with growth medium (Fig. 2B), which indicates the osteogenic potential of these cells. This evidence concerns the gene SPP1 and atrial fibrillation.