As shown in Fig. 2C, D, an obvious decrease of Col II and aggrecan expression was found in the IDD cell model (P < 0.001), while PPARγ significantly increased Col II and aggrecan expression (P < 0.05), and pioglitazone further enhanced the effect of PPARγ (P < 0.05). The gene discussed is ACAN; the disease is intervertebral disk degenerative disorder.