SPP1 and atrial fibrillation: Accordingly, EP histological scores were significantly higher in the cKO mice than those in the Spp1fl/fl mice at 6 and 14 months of age, while the NP/AF histological scores were higher in the cKO mice than those in the Spp1fl/fl mice only at 14 months of age (Fig. 2i, j), indicating that CEP degeneration preceded the degeneration of NP/AF in OPN-deficient IVD.