TGFB1 and keloid: Using multiple in vitro models including 2D monolayers, 3D spheroids, fibroblast–keratinocyte coculture, and collagen gel contraction, we evaluated the effects of 0.5% HK on keloid fibroblasts (KFs) and normal dermal fibroblasts (DFs), with and without TGF-β1 stimulation.