Paraffin-embedded skin slides were rehydrated and stained with Masson’s trichrome (Sigma-Aldrich) or picrosirius red kit (Abcam). The thickness of the dermis, defined as the distance between the epidermal-dermal junction to the dermal-adipose layer junction, was measured blindly at six randomly selected sites/microscopic fields in each skin sample (Wu et al., 2012 (link)). The picrosirius red–stained skin was quantified using ImageJ and macro language (available at https://imagej.nih.gov/ij/docs/examples/stained-sections/index.html). The percentage of positive picrosirius red–stained area was determined, and data were normalized to the GFP control.