Abstract
Peroxisome proliferator-activated receptor gamma (PPARγ) is the master regulator of adipogenesis, and has been indicated as a potential therapeutic target to promote osteoblast differentiation. However, recent studies suggest that suppression of PPARγ inhibits adipogenesis, but does not promote osteogenic differentiation in human bone marrow-derived mesenchymal stem cells (hBMSCs). It was reasoned that the osteogenic effect of PPARγ suppression may be masked by the strong osteogenesis-inducing condition commonly used, resulting in a high degree of matrix mineralization in both control and experimental groups. This study investigates the role of PPARγ in the lineage commitment of human adipose-derived mesenchymal stem cells (hADSCs) by interfering with the function of PPARγ mRNA through small interfering RNAs (siRNAs) specific for PPARγ2. By applying an osteogenic induction condition less potent than that used conventionally, we found that PPARγ silencing led to retardation of adipogenesis and stimulated a higher level of matrix mineralization. The mRNA level of PPARγ decreased to 47% of control 2 days after treatment with 50 nmol/l PPARγ2 siRNA, while its protein expression was 60% of mock control. In the meantime, osteogenic marker genes, including bone morphogenic protein 2 (BMP2), runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OC), were up-regulated under PPARγ silencing. Our results suggest that transient suppression of PPARγ promotes the onset of osteogenesis, and may be considered a new strategy to stimulate bone formation in bone tissue engineering using hADSCs.
Highlights
Peroxisome proliferator-activated receptor gamma (PPARc) is the master regulator of adipogenesis, and has been indicated as a critical switch in the commitment of progenitor cells to either the adipogenic or osteogenic pathway [1,2,3]
We provide a closely related but controversial observation in human adipose-derived mesenchymal stem cells, in which PPARc silencing resulted in higher level of osteogenic gene expression and matrix mineralization
As determined by real-time PCR, treatment of human adipose-derived mesenchymal stem cells (hADSCs) with 50 nmol/l PPARc2 small interfering RNAs (siRNAs) for 2 days resulted in 53–59% suppression of PPARc gene expression, compared with cells without siRNA treatment or those treated with mock control (Fig. 1C)
Summary
Peroxisome proliferator-activated receptor gamma (PPARc) is the master regulator of adipogenesis, and has been indicated as a critical switch in the commitment of progenitor cells to either the adipogenic or osteogenic pathway [1,2,3]. Peroxisome proliferator-activated receptor gamma siRNAs have been reported to enhance bone formation in human preadipocytes and foetal-femur-derived mesenchymal cells, and reverse osteogenic repression of alcohol on human bone marrow-derived mesenchymal stem cells (hBMSCs) [6, 7]. It was reported that suppression of PPARc through either PPARc antagonists or RNA interference inhibits adipogenesis, but does not promote osteogenic differentiation of hBMSCs, suggesting that PPARc may not be the master regulator of lineage determination in human bone marrow [10]. The discrepancy between our study and the previous one was discussed
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
