TNF and dentin dysplasia: Fibrocytes, in addition to acting as myofibroblasts precursors, also secrete a variety of cytokines, growth factors, and other extracellular matrix proteins (ECM) which are shown to be up-regulated in DD tissue such as transforming growth factor (TGF)-β, tumor necrosis factor (TNF)-α, interleukin (IL)-6, vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF), type I collagen, a-smooth muscle actin, and fibronectin [22].