Background: The use of adipose-derived stem cells (ASCs) for tissue engineering involves exposing them to metabolically-adverse conditions. This study examines the metabolism, proliferation, and differentiation of ASCs under various metabolic conditions.

Methods: ASCs were cultured in sixteen media conditions containing 0.6, 2.4, 4.3, or 6.1 mM glucose, 0.1, 2.5, 4.1 or 6.1 mM glutamine, and then grown in either 0.1% or 20% oxygen. Conditioned media was collected and assayed for glucose, lactate, and pyruvate. Cell proliferation and cell death were measured at several time points. Osteogenic differentiation was analyzed by alizarin red staining/ quantification and alkaline phosphatase activity, measured weekly over 4 weeks.

Results: ASCs remained metabolically active in all nutrient and oxygen conditions tested. Glucose consumption and lactate production increased under hypoxic conditions, but pyruvate consumption was jointly dependent on oxygen and glucose concentration. The 20% oxygen environment produced greater proliferation and cell death compared to the hypoxic environment. Osteogenic differentiation of ASCs was observed in both 20% and 0.1% oxygen environments when glucose and/or oxygen concentrations were physiologically normal to high respectively.

Conclusions: ASCs are an excellent source of multipotent cells capable of advancing tissue engineering methodologies currently used to address osseous defects. These data show that ASCs remain viable under adverse conditions of low glucose, glutamine, and oxygen concentrations. However, in 0.1% oxygen environments osteoblastic differentiation is dependent upon the presence of supra-physiologic levels of glucose and glutamine. Current challenges facing de-novo osteogenesis can be addressed by developing specific constructs to ensure the successful delivery of viable osteoprogenitor cells.