Aims: To study the mechanisms of action of obesity associated with osteoporosis has offered insights that fat mass may favour mesenchymal stem cell differentiation towards adipocytes away from the osteoblastic lineage. Previous studies have shown beneficial effects of green tea polyphenols (GTP) on obesity and insulin resistance. The aim of this study was to evaluate whether GTP regulates adipose-derived stem cells (ADSCs) differentiation shifting adipogenesis towards osteogenic process.
Methods: Primary human ADSCs were isolated from obese patients and treated with concentrations of GTP (1 and 10 µg/mL). The differentiation of ADSCs into mature adipocytes and osteoblasts was determined by Oil Red-O staining with cellular triglyceride assay and Alizarin red staining with calcium assay, respectively. Cells were fixed on coverslips for immunofluorescent staining to label key antibodies involved in the adipogenic pathway, peroxisome proliferator-activated receptor gamma (PPARɤ) and osteogenic pathway in Runt-related transcription factor 2 (RUNX2). qRT-PCR was used to reveal cell mRNA expression with and without GTP treatment for detecting the adipogenic pathway in Cebpa (CCAAT/enhancer-binding proteins), Pparg (PPARɤ) and Creb (cAMP response element-binding protein), osteogenic pathway in Runx2 and Bmp2 (Bone morphogenetic protein 2).
Results: GTP at 1 and 10 µg/mL significantly reduced total lipids and triglyceride content during ADSCs differentiation (P<0.05 vs control cells). Downregulation of PPARɤ expression in GTP-treated cells was dose-dependent (P<0.01 and P<0.001 at dose of 1 and 10 µg/mL, respectively). Calcium content and ALP activity were significantly increased in GTP-treated cells with increased Runx2 protein expression. Furthermore, GTP treatment seemed to inhibit adipogenesis by downregulating mRNA expression of PPARγ, CREB and C/EBPα, whilst increasing the osteogenic processes by upregulating mRNA expression of Runx2 and BMP2 (P<0.05).
Conclusions: These results indicate that GTP can regulate ADSCs differentiation towards osteogenesis through upregulating the RUNX2-BMP2 pathway and inhibiting adipogenesis by down regulating the PPARɤ-CREB-C/EBP pathway.