MMP13 is elevated in the steatotic liver. (a) Relative gene expression of matrix metalloproteinases (MMPs) in liver tissue of mice with steatosis (black bars) compared to normal (white bars) mice. Transcript levels were normalized to GAPDH and expressed as fold change relative to normal controls. Values represent the mean (n = 3 per group). Statistical analysis was carried out using 2-way ANOVA followed by Bonferroni post test between normal and steatotic samples for each MMP tested. (b) Representative western blot showing 3 samples per group and densitometric quantification (n = 9 per group) of MMP13 protein levels relative to actin levels in livers of wildtype C57bl/6 mice with and without steatosis. Statistical analysis was carried out using a 2-tailed t-test, P = 0.04. (c) Representative western blot and densitometric quantification of MMP13 protein levels relative to actin levels in human liver samples through multiple stages of NAFLD (n = 9 per group). Statistical analysis was carried out using a 2-tailed t-test with respect to normal livers. No significant differences were observed between the different stages of progression of NAFLD. (d) Representative immunohistochemical (IHC) staining of MMP13 in murine normal and steatotic livers. Inset represents IgG control. (e) Representative IHC of human MMP13 at different stages of NAFLD. MMP13 staining is detected at low levels in the normal liver hepatocytes and is increased in the stromal cells of livers with steatosis and steatohepatitis. Additionally, MMP13 is present in select hepatocytes in cirrhotic livers. Images were taken at 20X, Scalebar represents 100 microns.