Which decalcifier is best at preserving immunoreactivity for osteocalcin and osteonectin?

• A. Hydrochloric acid
• B. Formic acid
• C. 15% EDTA
• D. Sodium citrate

Answer: (C)

Preserving immunoreactivity during bone decalcification depends on keeping protein epitopes intact. Harsh acid decalcifiers quickly remove mineral but often degrade proteins, destroying epitopes on bone matrix proteins like osteocalcin and osteonectin, which leads to poor immunostaining. EDTA works by chelating calcium slowly and gently, decalcifying without violently hydrolyzing proteins, so the epitopes remain recognizable by antibodies. Among common decalcifiers, 15% EDTA provides effective decalcification while maintaining better antigenicity for these markers, giving stronger and more reliable immunohistochemical staining. Sodium citrate is milder but slower and may not preserve these specific epitopes as reliably, and acids are more likely to erode them.