Conditioned media cause increases in select osteogenic and adipogenic differentiation markers in mesenchymal stem cell cultures.

The optimal mesenchymal stem cell (MSC) culture conditions that would allow clinically viable tissue-engineered devices are still yet to be determined. Most MSCs are found in the bone marrow, an area that also contains numerous osteoblasts and adipocytes. Paracrine signalling may be leveraged to modulate MSC differentiation in the preparation of a tissue-engineered device. Thus, the objectives of this study were to determine the effects of adipocyte-conditioned medium (CM) on MSC differentiation to osteoblasts and to determine the effects of osteoblast CM on MSC differentiation to adipocytes. Two groups of murine MSCs were given either an osteogenic differentiation medium or an adipogenic differentiation medium. CM was taken from one group and administered to the opposite group in concentrations of 25% or 50%. Metabolic activity, total protein and alkaline phosphatase (ALP) assays were conducted on the osteogenic group at predefined time points throughout the 21 day study, while metabolic activity, triglyceride and oil red O assays were conducted on the adipogenic group at predefined time points. Adipocyte CM administered at a concentration of 50% increased the ALP production of MSCs undergoing osteogenic differentiation. Additionally, osteoblast CM increased the triglyceride production of MSCs undergoing adipogenic differentiation and enlarged the lipid vesicles that were produced by the cells. The effects of the osteoblast CM were seen at both concentrations, but were greatest at the 50% CM level.