Microvascular and cellular defects of the periosteum of osteogenesis imperfecta

Periosteum stripped from fragments of diaphyseal long bones from osteogenesis imperfecta (OI) patients was examined both in vivo and in vitro. The OI periosteum was thickened and characteristic finding was a defective microvascular system. The vascular walls of arterioles and capillaries were thick and the lumina of many of these vessels were narrowed or occluded by hypertrophic endothelial cells and multiplication of smooth muscle cell layers. Circulatory deficiency in the OI periosteum might be regarded as one of the causes of the slender, osteopenic diaphyseal bone characteristic of the disorder. A higher proliferative activity was observed in cultured OI periosteal cells, but the cytoplasmic structure showed increased myelinoid bodies and smooth endoplasmic reticulum and decreased lysosomes and rough endoplasmic reticulum. These findings may be related to the abnormal metabolic activity of OI periosteal cells.