Ultrasound Effect on Gene Expression of Sex Determining Region Y-box 9 (SOX9) and Transforming Growth Factor β Isoforms in Adipose Stem Cells

Cartilage tissue engineering is a promising method for repair of cartilage defects. Induction of chondrogenesis in mesenchymal stem cells (MSC) is currently used in cartilage tissue engineering. Among growth factors, transforming growth factor β (TGF-β) is common chondrogenic inducer but toward hypertrophic chondrocyte. However, mechanical factors such as ultrasound could stimulate chondrogenesis.
We aimed to investigate stimulation of endogenous TGF-β genes expression by low intensity pulsed ultrasound (LIPUS) in MSC.
In this experimental study, adipose tissue stem cells (ASC) cultures were treated with or without LIPUS (30 mW/cm2, 20 min/day) and with or without TGF-β3 (10 ng/mL) for 4 or 14 days. Chondrogenic gene expression of SOX9 and members of TGF-β family (β1, β2 and β3) was assessed in ASC cultures at day 4 and 14 by real time PCR.
The gene expression of SOX9 significantly increased by LIPUS and TGF-β treatment versus control cultures. Exogenous TGF-β3 treatment stimulated endogenous TGF-β1 and β2 gene expressions more than LIPUS treated cultures at day 4. LIPUS, TGF-β and LIPUS plus TGF-β treated cultures expressed same TGF-β3 gene expression at day 4. The expression of TGF-β1 and β2 decreased by LIPUS in comparison to TGF-β treated cultures at day 14.
Our results suggest that LIPUS might initiate differentiation of ASC without enhancing endogenous TGF-β genes in in-vitro.