PTN and scoliosis: In vivo models of experimentally induced scoliosis noted an increased expression of angiogenesis-regulating factors, such as metalloproteinase-1 (MMP1) and -12 (MMP12), vascular endothelial growth factor A (VEGFA) and pleiotrophin, supporting the notion of a close connection between defective angiogenesis and scoliosis progression [70,71,72,73].