A bone matrix calcification-initiator noncollagenous protein.

Area of Science:

• Biochemistry
• Biomaterials Science
• Skeletal Biology

Background:

• Bone matrix, when demineralized, typically fails to recalcify in physiological conditions.
• Inhibitors of calcification present in bone matrix can prevent recalcification even after extraction.

Purpose of the Study:

• To investigate the factors responsible for the recalcification of demineralized bone matrix.
• To identify and characterize proteins involved in initiating bone calcification.

Main Methods:

• Sequential demineralization, extraction, and autolytic digestion of bone matrix.
• Isolation and characterization of calcification initiator protein (CIP) using gel filtration and chromatography.
• In vivo implantation of bone matrix residues to assess recalcification.

Main Results:

• A specific calcification initiator protein (CIP) was unmasked after a multi-step extraction process, enabling bone matrix recalcification.
• CIP is a disulfide-bonded glycoprotein aggregate (55,000 Da subunits) with high acidic amino acid content and significant calcium-binding capacity.
• Bone morphogenetic property (BMP) appears to mask CIP, with both attached to bone collagen.

Conclusions:

• The unmasking of CIP is essential for the recalcification of demineralized bone matrix.
• CIP's properties suggest it plays a crucial role in initiating calcification.
• Further research is needed to determine CIP's role in normal skeletal calcification.