Key growth factors regulating this response are hepatocyte growth factor and keratinocyte growth factor.22,23 The receptors for these cytokines are expressed by the epithelium and are up-regulated in response to injury.24 Interleukin 1 and other cytokines also stimulate keratocyte/myofibroblast cells to produce metalloproteinases, collagenases, and other enzymes that are involved in the stromal wo