Fig. 6

PDA NPs suppress UV-induced collagen degradation and photoaging. (A) Representative Masson’s trichrome staining and Verhoeff’s Van Gieson (EVG) staining images of the dorsal skin in Balb/c mice from different groups (n = 4). (B) Quantitative analysis of collagen ratio. (C) Representative immune histochemistry images of MMP-1 and MMP-3 expression in the dorsal skin of Balb/c mice from different groups (n = 4). (D, E) The mRNA expression levels of MMP-1 and MMP-3 of HaCaT cells were detected by qRT-PCR after being pretreated with different concentrations of 60 mg/mL PDA NPs for 24 h, followed by exposure to UVR. The mRNA expression levels of these genes were normalized to β-actin. (F-H) The protein level of MMP-1 and MMP-3 of HaCaT cells was determined by western blotting after indicated treatments. GAPDH was detected as a loading control. All data represent the mean ± SD. *p < 0.05, **p < 0.01 and ***p < 0.001