the impact of confluence on bmmsc proliferation and osteogenic differentiation".

background: in the field of cellular therapy, the impact of confluence degree to harvest or differentiate bmmscs and the effect of cell-to-cell contact remains controversial. therefore, the effect of confluence on bmmscs properties was studied and confluence-associated osteogenic differentiation efficiency was identified. materials and methods: the impact of confluences at 20, 50, 70, 80 and 100% on bmmscs proliferation properties, expression of erk and p-erk proteins and glucose consumption rate was studied. confluence-associated osteogenic differentiation efficiency was identified by determining calcium deposition, alizarin red staining, alp activity and osteopontin and osteocalcin genes expression.       results: there was a correlation between confluence % and the bmmscs density. viability was declined at the lower and higher confluences. the highest cfu-f, brd-u uptake and population doubling were obtained at 80% confluence. erk band intensity in 100% confluent bmmscs was lower compared to other confluences. bands of p-erk were highly detectable in 70% and 80% confluences. glucose consumption rate at 70% and 80% confluences in the last days were higher than at 20% and 100% confluences. although higher osteogenic differentiation estimated by calcium deposition, alizarin red stain and alp activity at 80% confluences, it was also extended at 100% confluence. osteopontin gene expressed among all confluences including 100% while osteocalcin gene was expressed highly in 70% confluent cells. conclusion: we concluded that the optimum seeding density for maximal expansion and harvesting purposes is 80% confluence and up to 100% confluence for osteogenic differentiation to trigger the process to be more cost effective.