the impact of confluence on bone marrow mesenchymal stem (bmmsc) proliferation and osteogenic differentiation

background: in the field of cellular therapy, the impact of confluence degree on harvesting or differentiation of bmmscs and the effect of cell-to-cell contact remain controversial. therefore, the effect of confluence on properties of bmmscs was studied and efficiency of confluence-associated osteogenic differentiation was identified. materials and methods: the impact of 20, 50, 70, 80 and 100% confluences on proliferation properties of bmmscs, expression of erk and p-erk proteins and glucose consumption rate was studied. efficiency of confluence-associated osteogenic differentiation was identified by determining calcium deposition, alizarin red staining, alp activity and expression of osteopontin and osteocalcin genes. results: there was a correlation between confluence % and 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 of 70% and 80% confluences in the last days were higher than 20% and 100% confluences. although higher osteogenic differentiation was estimated at 80% confluence using calcium deposition, alizarin red staining and alp activity, it was also extended at 100% confluence osteopontin gene was expressed among all confluences including 100% confluence, 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 for osteogenic differentiation up to 100% confluence is also acceptable.