Degenerative lumbar EP and AF tissues from patients with DDD according to the modified Pfirrmann classification system were used as the DDD group (Supplementary Fig 1A–D).21 Quantitative real-time (qPCR) analysis of human tissues showed higher expression levels of HIF1a in the DDD group than in the control group. The gene discussed is HIF1A; the disease is atrial fibrillation.