Figure 4.

Vit D supplementation slows down KC progression by inhibiting collagen degradation systemically. (A) Plasma collagen degradation markers measured by ELISA: ICTP, MMP-9, (MMP-1, TIMP-1, and IL-1β. Results are expressed as fold change between month 0 and month 6 (M6/M0). (B) To establish the degradation status, we calculated the ratio between MMP-9 and TIMP-1 at months 0 and 6. (C, D) The MMP-9/TIMP-1 ratio inversely correlated with Vit D levels (C) and VDR expression (D) measured by RT-PCR. M0, n = 20 patients; M6, n = 20 patients. Graphs represent the mean ± SD. Statistical analysis was performed using the one-sample t-test, Wilcoxon signed-rank test, or Spearman's correlation coefficient. *P < 0.05, **P < 0.01, ***P < 0.001.