Ultrastructural localization of proteoglycans in bone in osteogenesis imperfecta as demonstrated by Cuprolinic Blue staining.

The role of proteoglycans in bone in osteogenesis imperfecta (OI) has been examined. Using Cuprolinic Blue staining of whole fetal bone tissue and examining the tissue in the transmission electron microscope, the presence of proteoglycans was observed. Quantitative comparative image-analysis of the proteoglycans from electron micrographs was performed, with measurement of sizes and number of proteoglycan particles. A significant increase in the total number of proteoglycan particles in OI bone osteoid was observed when compared with normal, matched controls. The area of the proteoglycan particles, as measured by pixel-area, using image analysis, was also increased in OI bone osteoid. These findings further suggest a role for proteoglycans in mineral formation by the possible inhibition of mineral growth and alteration of collagen nucleation sites. The increased number and size of proteoglycan particles may be a contributing factor to the previously reported poor mineral formation with subsequent loss of bone strength, making it more prone to fracture, in OI.