AMP kinase agonists attenuate TGF-β-induced profibrotic responses in three-dimensional full-thickness human skin equivalents. Fibroblasts embedded in three-dimensional full-thickness skin equivalents were incubated with metformin (1 mM) with or without TGF-β (5 ng/ml) for six days. At the end of the experiments, rafts were harvested. A. Real-time qPCR. The results represent the means ± SEM of triplicate determinations. B. 4-μm thick paraffin-embedded sections were stained with Picrosirius Red. Mature highly cross-linked collagen fibers in the dermal compartment appear red when visualized under polarized light, whereas less mature collagen fibers containing few cross-links appear yellow/green. Representative images (original magnification ×40). SEM, standard error of the mean; TGF-β, transforming growth factor-β.