Noggin is a secreted homodimeric glycoprotein that is an antagonist of bone morphogenetic proteins (BMPs). Secreted Noggin probably remains close to the cell surface due to its binding of heparin-containing proteoglycans.

FGF-10 belongs to the subgroup of FGFs that also includes FGF-3, -7, and -22. FGF-10 is secreted by mesenchymal cells and associates with extracellular FGF-BP. It preferentially binds and activates epithelial cell FGF R2 (IIb) and interacts more weakly with FGF R1 (IIb).

The Wnt signal transduction is essential for cell proliferation and differentiation and the self-renewal of stem cells.

HGF, is a pleiotropic protein in the plasminogen subfamily of S1 peptidases. Human HGF is secreted as an inactive 728 amino acid (aa) single chain propeptide.

Basic fibroblast growth factor (bFGF), also known as FGF2, is a member of the FGF superfamily of mitogenic proteins which show 35-60% amino acid conservation.

FGF-7 (fibroblast growth factor-7) is one of 22 known members of the mouse FGF family of secreted proteins that plays a key role in development, morphogenesis, angiogenesis, wound healing, and tumorigenesis.

Human Gastrin I, is the endogenous peptide produced in the stomach, and increases gastric acid secretion via cholecystokinin 2 (CCK2) receptor.

Epidermal growth factor (EGF) is a small, potent growth factor capable of inducing cell proliferation, differentiation, and survival. EGF is the founding member of the EGF family which are characterized by a shared structural motif, the EGF- like domain[1]. EGF is a high affinity ligand of the EGF receptor (ErbB).