Nacre is able to induce bone-forming cells mineralization, and gains widespread interest in bone regeneration. While, the osteoinductive compounds are not identified yet. The nacre extract, ethanol soluble matrix (ESM), was proven having the capacity to induce the mineralization of mouse MC3T3-E1 cells and to restore mineralization defect in human osteoarthritic osteoblasts. Being tested on the two cells, ESM could induce the formation of mineralization nodules, identified as crystalline hydroxyapatite by RAMAN spectroscopy, and stimulate the expression of bone markers, collagen type I, Runx2, osteopontin and osteocalcin. Besides, the formation of collagen fibres in extracellular matrix were also observed with SHG imaging. Thus, ESM is suitable to serve as a source of osteoinductive compounds.
Recently, a new step was done in the purification of the active nacre compounds to the way of the identification. By using ion-exchange resin and cation exchange HPLC, cationic ESM (ESMc), anionic ESM (ESMa) and ten cationic HPLC fractions of ESM were achieved and tested to validate their osteoanabolic activity. ESMc and 2 HPLC fractions stimulated the mineralization in both cell types. No interaction on bone mineralization between ESMc and ESMa was observed. Energy dispersive X-ray spectrometry demonstrated the abundant presence of calcium and chloride in the osteogenic fractions. To validate, pure CaCl2 was tested and proven having an osteogenic effect in both cells, but less stable than ESM, suggesting that free Ca plays a role, though limited, in inducing the cell mineralization.
In conclusion, ESM has an osteoanabolic effect, which may bring some innovative therapeutics for hypomineralization diseases, such as osteoporosis. The cationic ESM, a purified matrix of ESM, makes the identification prospective a bit closer.
14 May 2016 - 17 May 2016