Human Platelet-Derived Growth Factor-BB (PDGF-BB) is a homodimeric growth factor composed of two PDGF-B chains that plays a critical role in cell proliferation, migration, angiogenesis, and tissue repair. PDGF-BB signals primarily through platelet-derived growth factor receptor-β (PDGFR-β) and PDGFR-α/β receptor complexes, activating intracellular signaling pathways including PI3K/AKT, MAPK, and STAT, which regulate fibroblast activation, smooth muscle cell proliferation, and extracellular matrix production. In humans, PDGF-BB is produced by platelets, macrophages, endothelial cells, fibroblasts, and other stromal cells, and is released during tissue injury, inflammation, and wound healing. It plays essential roles in vascular development, connective tissue repair, and regulation of mesenchymal cell growth, contributing to processes such as dermal wound healing and blood vessel formation. Dysregulated PDGF-BB signaling has been implicated in fibrotic diseases, atherosclerosis, and cancer, including glioblastoma, sarcomas, and other tumors, where PDGF-driven signaling can promote tumor cell proliferation and remodeling of the tumor microenvironment. Because of its central role in angiogenesis, tissue regeneration, and cellular growth signaling, human PDGF-BB is widely studied as both a biomarker and therapeutic target in regenerative medicine, fibrosis, vascular disease, and oncology.