Human blood is composed of plasma, red blood cells, white blood cells, and platelets. The primary function of platelets is to prevent blood loss by clotting together at the site of vascular rupture. Platelets also create the foundation for tissue regeneration throughout the body by releasing growth factors during degranulation. Growth factors are tiny bioactive proteins which bind to the receptors of target cells including mesenchymal stem cells (MSCs), osteoblasts, fibroblasts, endothelial cells, and epidermal cells. Once bound to the target cells, the growth factors increase cell signaling and the expression of genes which direct cellular proliferation, matrix formation, osteoid production, collagen synthesis, and angiogenesis.
In spinal fusion surgery, increased concentration of platelets initiates and biologically amplifies the healing cascade. Growth factors at the bone graft site increase local cell signalling, mitogenesis, and chemotaxis. Increased bone fusion rates could be attributed to matrix formation, osteoid production and increased MSC migration.