Polyamines Modulate Nitric Oxide Production and Cox‐2 Gene Expression in Response to Mechanical Loading in Human Adipose Tissue‐Derived Mesenchymal Stem Cells

For bone tissue engineering, it is important that mesenchymal stem cells (MSCs) display a bone cell‐like response to mechanical loading. We have shown earlier that this response includes increased nitric oxide (NO) production and cyclooxygenase‐2 ( COX‐2 ) gene expression, both of which are intimately involved in mechanical adaptation of bone. COX‐2 gene expression is likely regulated by polyamines, which are organic cations implicated in cell proliferation and differentiation. This has led to the hypothesis that polyamines may play a role in the response of adipose tissue‐derived MSCs (AT‐MSCs) to mechanical loading. The aim of this study was to investigate whether genes involved in polyamine metabolism are regulated by mechanical loading and to study whether polyamines modulate mechanical loading‐induced NO production and COX‐2 gene expression in human AT‐MSCs. Human AT‐MSCs displayed a bone cell‐like response to mechanical loading applied by pulsating fluid flow (PFF), as demonstrated by increased NO production and increased gene expression of COX‐2 . Furthermore, PFF increased gene expression of spermidine/spermine N (1)‐acetyltransferase, which is involved in polyamine catabolism, suggesting that mechanical loading modulates polyamine levels. Finally, the polyamine spermine was shown to inhibit both PFF‐induced NO production and COX‐2 gene expression, suggesting that polyamines modulate the response of human AT‐MSCs to mechanical loading. In conclusion, this is the first study implicating polyamines in the response of human AT‐MSCs to mechanical loading, creating opportunities for the use of polyamines in tissue engineering approaches targeting skeletal defects.