Nacre, or mother of pearl, is a promising natural biocompatible biomaterial consisting of aragonite (97%) and of organics (3%) and capable to increase the cell osteogenic activity. It has been established that osteoarthritic osteoblasts present a mineralization defect and, to date, only a few molecules (vitamin D3 and bone morphogenetic protein2) could improve the mineralization potential of this cell type. In this context, we evaluated the impact of nacreous molecules on the mineralization capacity of a pre-osteoblast lineage, MC3T3-E1, and osteoblasts from osteoarthritis (OA) patients.
For this goal, molecules were extracted from nacre with ethanol (ESM, Ethanol Soluble Matrix) and tested for 21 days at two concentrations (100 and 200 μg/ml), on MC3T3-E1, and osteoblasts of the subchondral bone from OA patients undergoing total knee replacement. Alizarin Red staining was performed to visualize capacity of mineralization and quantified at 405 nm. The Raman spectroscopy and environmental scanning electron microscopy were used to demonstrate the presence of calcium phosphate (hydroxyapatite). Additionally, the expression of bone markers such as Collagen type I, osteocalcin, osteopontin and Runx2 was monitored by quantitative PCR.
Our results with the alizarin red assay demonstrated the presence of precipitated calcium in cells treated by ESM from 7 days of culture for MC3T3-E1 and 14 days for osteoblasts. At day 7, the expression of Runx2, osteopontin andosteocalcin was increased. RAMAN and electron microscopy showed the presence of nanograins of hydroxyapatite in MC3T3-E1 and an early crystalline form of calcium phosphate in osteoblast cultures, after treatment with ESM.
In conclusion, the increased mineralization activity observed on MC3T3-E1 was also observed on OA osteoblasts. ESM would be able to restore a physiological phenomenon and induce mineralization of pre-osteoblastic cells. Thus confirming the osteogenic potential of nacre extract and place the MC3T3-E1 lineage as a promising model for screening nacreous molecules.
17 May 2014 - 20 May 2014