Table 4: Select endogenous growth factors and their known functions in fracture healing.

Growth factorsa	Known role in fracture healing	Produced by	Acts upon	Common orthopaedic uses
PDGF	Recruits inflammatory cells to fracture site. Increases cellular proliferation and collagen deposition. Promotes angiogenesis29	Platelets, monocytes, endothelial cells	signal mechanism involves tyrosine kinase receptors
TGF-β	May regulate cartilage and bone formation in fracture callus through stimulation of collagen and proteoglycans production by mesenchymal cells.	Platelets, osteoblasts, chondrocytes	signal mechanism involves serine/threonine kinase receptors	Used to augment porous-coated implants; BMP-2 and -7 (member of TGF- β family commonly used in lumbar fusions, fracture nonunions, open tibia fractures)
VEGF	Promotes vasculogenesis and angiogenesis	Platelets, chondrocytes in callus	Vascular endothelial cells
FGF	Increase cellular division and collagen deposition. Promotes angiogenesis.
PTH	Promotes bone deposition when used in pulsatile fashion. May have osteoinductive properties.24	Parathyroid glands	Mesenchymal stem cells24	rhPTH (teriparatide) has been shown to increase bone mineral density lumbar spines and femoral necks. Reduces overall fracture risk.
ILGF	The primary mediator of human growth hormone; functions in growth of many cell types Induces linear skeletal growth by promoting cellular proliferation without maturation (physeal closure). Supports anabolic muscle and bone growth in mature skeleton.	Osteoblasts, chondrocytes, hepatocytes	Many cell types, various insulin/IGF-1 receptors	FDA approved for use in pediatric treatment of short stature from growth hormone insensitivity (GHI) 30

^a PDGF, platelet-derived growth factor; TGF-β, transforming growth factor beta; VEGF, vascular endothelial growth factor; FGF, fibroblast growth factor; rhPTH, recombinant human parathyroid hormone; ILGF, insulin-like growth factor