Focal adhesion kinase FAK also known as protein tyrosine

Focal adhesion kinase (FAK), also known as protein tyrosine kinase2 (PTK2), is a tyrosine kinase and vital member in integrin-mediated signaling pathways [3]. In response to integrin involvement, FAK would be phosphorylated. It was reported that FAK is involved in cellular adhesion and spreading [4]. Besides FAK is also an signal adaptor, which could cross talk with multiple other signal transduction pathways, and participate in regulation of various cellular processes including apoptosis, cell mobility and migration [5,6]. It was also reported that FAK could promote osteogenesis of ADSCs via Wnt-β-catenin signal [3,7]. BMP-9, also named as growth differentiation factor2 (GDF-2), was first identified in mice liver tissues [8]. BMP-9 could promote MSCs differentiation towards adipose, blood veins and cartolare [8,9]. Among all these effects mentioned above, osteogenesis and adipogenesis effects of BMP-9 were mostly valued [9,10]. BMP-9 could also enhance Wnt-β-catenin signal, and promote osteogenesis [11]. Although other BMP family members such as BMP2/4/6/7 were described to possess similar functions, yet BMP-9 is much stronger [8,12].
Materials and methods
Results
Discussion Osteoblast proliferation and differentiation are regulated by complex signaling networks and relationship between osteoblastogenesis and adipogenesis is important to our understanding of development and diseases affecting bone metabolism [13,21,22].Besides bone marrow stromal cells(BMSCs), adipose derived stromal A-54556A is another critical source for bone regeneration [1,23]. Both cells contribute to bone regeneration through osteogenesis [8]. Although BMSCs may bear greater potential in osteogenesis, ADSCs is more abundant and easier accessed. Thus, investigating on ADSCs osteogenesis bears great importance and may provide support for further studies in bone regeneration. Osteogenesis of ADSCs is regulated by FAK and BMP-9 [3,9]. Both factors contribute to ADSCs differentiation, and they may cross talk through Wnt-β-catenin pathway. From our results, ADSCs treated with BMP-9 contains stronger FAK phosphorylation and osteogenic genes expression (in Fig.1). Intensities of these proteins all increased when cells received higher dose of BMP-9. BMP-9 induced ALP and p-FAK signal indicated strong correlation between BMP-9 and ADSCs osteogenesis. Notably, activation of FAK is also enhanced by BMP-9 administration, indicating that FAK may act as a downstream factor of BMP-9 pathway. While BMP-9 could enhance ADSCs proliferation, knocking down FAK significantly inhibited such effect (in Fig. 2A). Migration of ADSCs was also inhibited by FAK knock down, which was remarkably promoted by BMP-9(in Fig. 2B). These results further validated that FAK might participate in BMP-9 signal transduction, or at least cross talked with BMP-9. Considering that both early osteogenesis (in Fig. 3A,B) and late osteogenesis (in Fig. 3C,D) were inhibited in FAK-knockdown cells, the hypothesis became much favorable that FAK played a pivotal role in BMP-9 induced ADSC osteogenesis. This is also supported by the fact that expression of osteogenic factor in BMP-9 treated ADSCs was all inhibited by shFAK. When analyzing cross talk between FAK and BMP-9, we revealed that only Wnt-β-catenin pathway was affected by FAK. Considering the intact Smads signal in shFAK cells, Smads pathway seems unrelated with FAK (in Fig. 5). We therefore concluded that in ADSCs, BMP-9 could activate FAK and Smads in parallel. FAK could affect GSK3β, modulating β-catenin signal and finally lead to expression of osteogenic proteins. Smads signaling pathway requires no β-catenin and stayed intact from shFAK. Thus we deduced that FAK and Smads could induce osteogenic differentiation and bone regeneration through different routes, and the only cross talk between FAK and BMP-9 is through Wnt-β-catenin.
Competing financial interests
Acknowledgements
Introduction Mounting epidemiological evidence has demonstrated that various natural components are beneficial to lower the risk of cancer development (Fiala, Reddy, & Weisburger, 1985). Among the natural compounds, polyphenols are a group of phytochemicals that have been widely reported possessing anti-tumoral activity in both in vitro and in vivo models (Yang, Landau, Huang, & Newmark, 2001). The dried flower of Hibiscus sabdariffa L. (Malvaceae) is commonly used as a major ingredient in a popular beverage Roselle tea, which contains a high content of polyphenols. Hibiscus polyphenol-rich extracts (HPE) is also used in traditional Chinese medicine for relief of hypertension (Haji Faraji & Haji Tarkhani, 1999), pyrexia, inflammation (Dafallah & al-Mustafa, 1996), liver disorders (Wang et al., 2000), and immunomodulating function (Muller & Franz, 1992). The component analysis shows that HPE consists of various polyphenols including anthocyanins, flavonoids, and polyphenolic acids, and some of the polyphenols have been indicated as anti-carcinogenic agents such as protocatechuic acid (Truong et al., 2017).