Quantitative real-time PCR16,17 was used to analyze expression of genes previously implicated in keloid scarring: type 1 collagen pro-alpha 1 and 2 chain genes (COL1A1 and COL1A2); matrix metalloproteinases 1 and 3 (MMP1 and MMP3); and periostin (POSTN)15,18-22 (Fig 2). Here, MMP1 is linked to keloid.