A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation, healing, and cellular differentiation.
Growth factors are regulators
Growth factors determine the fate of cells as they differentiate from being progenitors into their mature differentiated state.
Engineering growth factors for regenerative medicine applications. Mitchell AC, Briquez PS, Hubbell JA and Cochran JR. Acta Biomater. 2016 Jan; 30: 1–12.