Abstract
A reciprocal relationships between osteogenesis and adipogenesis has been observed in vitro and in vivo, and mechanical stretch has been believed to be a regulating factor of osteo-adipogenic axis differentiation of mesenchymal stem cells. In this study, rat adipose stem cells (ASCs) were isolated and cultured in adipogenic or normal medium. Their exposure to cyclic mechanical stretch (2000 με, 1 Hz) in the presence of adipogenic medium decreased mRNA and protein level of PPAR-γ, and increased Runx2 mRNA and protein levels as well as Pref-1 mRNA level, compared to static samples. ASCs cultured in normal medium without adipogenic induction did not show any significant change in mRNA expression of PPAR-γ, Runx2, nor Pref-1 irrespective of mechanical loading. Stretching induced phosphorylation of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) during the induction period. It was concluded that mechanical stretch inhibited adipogenesis and stimulated osteogenesis of these ASCs in the presence of adipogenic medium and that ERK1/2 activation may be involved in the mechanical stress-induced trans-differentiation.