Background: Understanding interspecies variation between animal models and humans is essential to develop tissue-engineered bone. The authors studied osteogenic and angiogenic marker expression in human and murine osteoblasts and mesenchymal stem cells. Methods: Three human cells (human mesenchymal stem cells, multilineage progenitor cells, and normal human osteoblasts) and three murine cells (MC3T3-E1, C3H10T1/2, and M2-10B4) were used. Cells were seeded onto poly-lactide-glycolic acid-coated tissue culture plates or three-dimensional poly-lactide-glycolic acid scaffolds, incubated in osteogenic medium, and harvested at 1, 4, and 7 days. mRNA expression was analyzed using quantitative real-time reverse-transcriptase polymerase chain reaction for osteogenic markers, including alkaline phosphatase, osteocalcin, bone sialoprotein, and core-binding factor alpha-1, and angiogenic markers, including vascular endothelial growth factor and interleukin-8. Data were analyzed using analysis of variance. Results: All human cells had significantly increased expression of osteogenic markers in three dimensions compared with two dimensions (alkaline phosphatase by 220 percent, osteocalcin by 323 percent, bone sialoprotein by 534 percent, and core-binding factor alpha-1 by 357 percent). However, all murine cells exhibited significant decreases in the expression of osteogenic markers in three-dimensional compared with two-dimensional cultures (alkaline phosphatase by 89 percent, osteocalcin by 64 percent, bone sialoprotein by 76 percent, and core-binding factor alpha-1 by 73 percent). In contrast, all human and murine cells showed markedly elevated expression of angiogenic factors interleukin-8 and vascular endothelial growth factor in three-dimensional compared with two-dimensional cultures. Measurement of alkaline phosphatase activity confirmed this pattern of osteogenic differentiation. Conclusions: In three-dimensional versus two-dimensional cultures, osteogenesis increased significantly in human cells but decreased in murine cells; angiogenesis increased regardless of species. Since three-dimensional cultures represent in vivo conditions more closely, this species variation has important translational implications to tissue-engineered bone research.
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