PPARγ silencing enhances osteogenic differentiation of human adipose‐derived mesenchymal stem cells

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.

Sustained knock down of PPARγ and bFGF presentation in collagen hydrogels promote MSC osteogenesis

“…The optimal bFGF was determined as 10 ng in the present study, similar to the previous report [14]. PPARγ is known as a potential target for regulating the osteogenic differentiation of progenitor cells, and suppression of PPARγ by RNA interference was demonstrated to promote osteogenic differentiation of human MSCs [2]. However, siRNA transfection with conventional method was usually transitory (within one week).…”

“…It has been demonstrated that down-regulation of PPARγ could significantly promote bone regeneration [18]. In a report by Lee et al [2], suppression of PPARγ through RNA interference efficiently enhanced MSC osteogenic differentiation induced by osteogenic medium, suggesting that suppressing PPARγ by siRNA may be a potent enhancer for MSC osteogenic differentiation.…”

“…Therefore, some other strategies, which may play synergetic roles with growth factors in regulating MSC differentiation, would be required in bone tissue engineering. Peroxisome proliferatoractivated receptor gamma (PPARγ) was confirmed to be an important regulator in MSC osteogenic differentiation [2,18]. It has been demonstrated that down-regulation of PPARγ could significantly promote bone regeneration [18].…”

“…Meanwhile, severe bone disorders are also increasingly prevalent with the greying of society [1,2]. For serious bone defects, it is usually difficult to heal through endogenous regenerative mechanisms, especially for aged patients.…”

BMP2 Increases Adipogenic Differentiation in the Presence of Dexamethasone, which is Inhibited by the Treatment of TNF-a in Human Adipose Tissue-Derived Stromal Cells

“…PPAR-γ plays a critical role in commitment switch of progenitor cells between adipogenesis and osteogenesis [36,37]. It has been reported that PPAR-γ silencing increases osteogenic differentiation of hADSCs [38]. We observed that the treatment of TNF-α restored the BMP2-induced increase in osteogenic differentiation in hADSCs in which the addition of BMP2 alone inhibited osteogenic differentiation, which results from TNF-α-induced inhibition of PPAR-γ and C/EBP-α expression.…”