VDR and Hyperkeratosis: Given the hyperkeratosis observed in VDR-KO rats through HE staining, we conducted Western blotting using the antibody against the keratin marker Krt14 and anti-pan-keratin antibody (PCK26), which detects rat keratin 1 (66 kDa), keratin 5 (58 kDa), and keratin 8 (52 kDa).