Complement component C3: Serologic signature for osteogenesis imperfecta. Analysis of a comparative proteomic study

Osteogenesis imperfecta (OI) is a disease characterized by low bone mass and bony fragility. This study investigated the serum proteomic profiles and their correlation with bone density for OI cases. Methods: Twenty OI patients and 20 control participants were included. Comparative serum proteomic profiles were analyzed by two-dimensional electrophoresis and tandem mass spectrometry. Serum protein levels were measured by enzyme-linked immunosorbent assay. Cutoff values and areas under the curve were estimated by the receiver operating characteristic curve. Bone mineral density data was obtained from all OI patients. Results: Candidate proteins identified by electrophoresis were complement component C3 (C3), vitamin D-binding protein (DBP), and haptoglobin (HP). Enzyme-linked immunosorbent assay validation showed that OI patients had decreased C3 and DBP and increased HP. The results were not affected by age or bisphosphonate use. Serum C3 levels significantly correlated with bone mineral density of the lumbar spine and hip. C3 had the greatest areas under the curve to distinguish OI from healthy controls. Conclusion: Serum C3, DBP, and HP are emerging serologic signatures for OI. Concentrations of serum C3 correlated with the T score of OI patients. C3 had the greatest areas under the curve of the three proteins to distinguish OI from healthy controls.