Fibroblast growth factor 8B (FGF-8B) is a member of the fibroblast growth factor (FGF) family and is an isoform of FGF-8. Cytokines in the FGF family possess broad mitogenic and cell survival activities (Folkman and Klagsbrun; Kimelman and Kirschner) and are involved in a variety of biological processes, including cell proliferation, differentiation, survival, and apoptosis (Folkman and Klagsbrun; Klagsbrun; Rifkin and Moscatelli). FGF-8B signals through FGF receptors (FGFRs) to activate PI3K and MAPK pathways. FGF-8B regulates gastrulation, epithelial-mesenchymal transition, and mesenchymal to epithelial differentiation during embryonic development. FGF-8B has also been found in peripheral blood leukocytes and healthy bone marrow samples (Mattila and Härkönen). FGF-8B has mitogenic effects on somatic cells in the germinal epithelium and is expressed in adult mouse ovarian cells and tissues, which suggests that it regulates maturation of oocytes and seminiferous epithelium in testes (Valve et al.). This product is animal component-free.