title: Metabolic and functional characterization of human adipose-derived stem cells in tissue engineering.
abstract: BACKGROUND
  The use of adipose-derived stem cells for tissue engineering involves exposing them to metabolically adverse conditions. This study examines the metabolism, proliferation, and differentiation of adipose-derived stem cells under various conditions.
  
  
  METHODS
  Adipose-derived stem cells were cultured in 16 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 were 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
  Adipose-derived stem cells 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 with the hypoxic environment. Osteogenic differentiation of adipose-derived stem cells was observed only when glucose and/or oxygen concentrations were physiologically normal to high.
  
  
  CONCLUSIONS
  Adipose-derived stem cells are an excellent source of multipotent cells and are capable of advancing current tissue engineering methodologies. These data show that adipose-derived stem cells remain viable under adverse conditions of low glucose, glutamine, and oxygen concentrations. However, there are variable levels of differentiation in the various culture conditions, which could lead to challenges in de novo osteogenesis and other forms of tissue engineering. Therefore, these results should be used in developing specific strategies to ensure successful application of adipose-derived stem cells in bone engineering and similar applications.
authors.affiliation: Durham and Research Triangle Park, N.C. From the Division of Plastic, Reconstructive, Maxillofacial, and Oral Surgery, Department of Surgery, Duke University Medical Center, and Zen-Bio, Inc.
authors.forename: Blaine T
authors.initials: BT
authors.lastname: Mischen
authors.forename: Keith E
authors.initials: KE
authors.lastname: Follmar
authors.forename: Kurtis E
authors.initials: KE
authors.lastname: Moyer
authors.forename: Ben
authors.initials: B
authors.lastname: Buehrer
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Olbrich
authors.forename: L Scott
authors.initials: LS
authors.lastname: Levin
authors.forename: Bruce
authors.initials: B
authors.lastname: Klitzman
authors.forename: Detlev
authors.initials: D
authors.lastname: Erdmann