The Comparison of Commercial Serum-Free Media for Hanwoo Satellite Cell Proliferation and the Role of Fibroblast Growth Factor 2

Fetal bovine serum (FBS), which contains various nutrients, comprises 20% of the growth medium for cell-cultivated meat. However, ethical, cost, and scientific issues, necesitates identification of alternatives. In this study, we investigated commercially manufactured serum-free media capable of culturing Hanwoo satellite cells (HWSCs) to identify constituent proliferation enhancing factors. Six different serum-free media were selected, and the HWSC proliferation rates in these serum-free media were compared with that of control medium supplemented with 20% FBS. Among the six media, cell proliferation rates were higher only in StemFlexTM Medium (SF) and Mesenchymal Stem Cell Growth Medium DXF (MS) than in the control medium. SF and MS contain high fibroblast growth factor 2 (FGF2) concentrations, and we found upregulated FGF2 protein expression in cells cultured in SF or MS. Activation of the fibroblast growth factor receptor 1 (FGFR1)-mediated signaling pathway and stimulation of muscle satellite cell proliferation-related factors were confirmed by the presence of related biomarkers (FGFR1, FRS2, Raf1, ERK, p38, Pax7, and MyoD) as indicated by quantitative polymerase chain reaction, western blotting, and immunocytochemistry. Moreover, PD173074, an FGFR1 inhibitor suppressed cell proliferation in SF and MS and downregulated related biomarkers (FGFR1, FRS2, Raf1, and ERK). The promotion of cell proliferation in SF and MS was therefore attributed to FGF2, which indicates that FGFR1 activation in muscle satellite cells may be a target for improving the efficiency of cell-cultivated meat production.

Dual-Warhead Conjugate Based on Fibroblast Growth Factor 2 Dimer Loaded with α-Amanitin and Monomethyl Auristatin E Exhibits Superior Cytotoxicity towards Cancer Cells Overproducing Fibroblast Growth Factor Receptor 1

Targeting fibroblast growth factor receptor 1 (FGFR1) is a promising therapeutic strategy for various cancers associated with alterations in the FGFR1 gene. In this study, we developed a highly cytotoxic bioconjugate based on fibroblast growth factor 2 (FGF2), which is a natural ligand of this receptor, and two potent cytotoxic drugs-α-amanitin and monomethyl auristatin E-with completely independent mechanistic modes of action. Utilizing recombinant DNA technology, we produced an FGF2 N- to C-end dimer that exhibited superior internalization capacity in FGFR1-positive cells. The drugs were site-specifically attached to the targeting protein using SnoopLigase- and evolved sortase A-mediated ligations. The resulting dimeric dual-warhead conjugate selectively binds to the FGFR1 and utilizes receptor-mediated endocytosis to enter the cells. Moreover, our results demonstrate that the developed conjugate exhibits about 10-fold higher cytotoxic potency against FGFR1-positive cell lines than an equimolar mixture of single-warhead conjugates. The diversified mode of action of the dual-warhead conjugate may help to overcome the potential acquired resistance of FGFR1-overproducing cancer cells to single cytotoxic drugs.

Increased serum concentrations of estrogen-induced growth factors Midkine and FGF2 in NF1 patients with plexiform neurofibroma

Neurofibromatosis type 1 (NF1) predisposes to the development of dermal and plexiform neurofibromas and serum of NF1 patients stimulates neurofibroma proliferation in vitro. This study aimed to determine whether, in NF1 patients, serum levels of midkine (MK) and fibroblast growth factor 2 (FGF2) were associated with the number and/or type of neurofibromas. In addition, their concentrations were correlated with serum levels of dehydroepiandrosterone sulfate (DHEAS), a neurosteroid secreted by the peripheral nervous system. We performed a case control-study and measured, by ELISA assay, serum concentrations of MK, FGF2, and DHEAS in 20 NF1 patients and 30 controls. We found increased serum levels of MK and FGF2 in NF1 patients between 30 and 50 years old. Their concentrations were significantly higher in NF1 patients with plexiform neurofibromas than in controls (P=0.003 for MK and P=0.008 for FGF2). As an underlying hormonal regulation was suspected, DHEAS serum levels were measured but no difference was observed between patients and controls. We also observed a strong association between MK and FGF2 levels (P=0.0001) in NF1 patients and controls. In conclusion, we point out MK and FGF2 as biomarkers for plexiform neurofibroma in NF1 patients. As both growth factors are estrogen-responsive genes and neurofibromin is a co-repressor of estrogen receptor alpha activity, we suggest that the increased serum levels of MK and FGF2 observed in NF1 patients might be due to estradiol hypersensitivity.

Unconventional secretion mediated by direct protein self-translocation across the plasma membranes of mammalian cells

In recent years, a surprisingly complex picture emerged about endoplasmic reticulum (ER)/Golgi-independent secretory pathways, and several routes have been discovered that differ with regard to their molecular mechanisms and machineries. Fibroblast growth factor 2 (FGF2) is secreted by a pathway of unconventional protein secretion (UPS) that is based on direct self-translocation across the plasma membrane. Building on previous research, a component of this process has been identified to be glypican-1 (GPC1), a GPI-anchored heparan sulfate proteoglycan located on cell surfaces. These findings not only shed light on the molecular mechanism underlying this process but also reveal an intimate relationship between FGF2 and GPC1 that might be of critical relevance for the prominent roles they both have in tumor progression and metastasis.

Identification of YAP1 as a novel downstream effector of the FGF2/STAT3 pathway in the pathogenesis of renal tubulointerstitial fibrosis

Chronic kidney disease is a global health problem and eventually develops into an end-stage renal disease (ESRD). It is now widely believed that renal tubulointerstitial fibrosis (TIF) plays an important role in the progression of ESRD. Renal tubular epithelial-mesenchymal transition (EMT) is an important cause of TIF. Studies have shown that FGF2 is highly expressed in fibrotic renal tissue, although the mechanism remains unclear. We found that FGF2 can activate STAT3 and induce EMT in renal tubular epithelial cells. STAT3, an important transcription factor, was predicted by the JASPAR biological database to bind to the promoter region of YAP1. In this study, STAT3 was shown to promote the expression of the downstream target gene YAP1 through transcription, promote EMT of renal tubular epithelial cells, and mediate the occurrence of renal TIF. This study provides a theoretical basis for the involvement of the FGF2/STAT3/YAP1 signaling pathway in the process of renal interstitial fibrosis and provides a potential target for the treatment of renal fibrosis.

ERK1/2 and JNK signaling synergistically modulate mitogenic effect of fibroblast growth factor 2 on liver cell

Proliferation of the adult hepatocyte population represents a central feature of tissue regeneration after liver injury and resection. This process could be driven by a diverse range of mitogens, such as hepatocyte growth factor (HGF) and fibroblast growth factor (FGF). Among FGF family, FGF2 is closely related to wound repair and cell proliferation. FGF2 does function in the process of angiogenesis in regenerating liver, while fewer reports are concerned with the impact and underlying mechanism of FGF2 on liver cell proliferation. To this end, an immortalized human normal hepatocyte L02 and mouse primary hepatocytes were exposed to FGF2 in this study. We demonstrate that FGF2 significantly enhances liver cell proliferation. Treatment with FGF2 obviously increases the phosphorylation level of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and c-Jun N-terminal kinase (JNK). Activity inhibition or expression down-regulation prove that both ERK1/2 and JNK signaling are required for FGF2-mediated effect on liver cell proliferation. Interestingly, interfering of ERK1/2 signaling results in marked decrease of JNK activation under FGF2 treatment, and JNK signaling is also involved in regulation of FGF2-induced ERK1/2 activation, suggesting that cross-talk between ERK1/2 and JNK signaling is important for FGF2 mitogenic activity. Both ERK1/2 and JNK signal via CREB to function in proliferation impact of FGF2 on liver cells. Taken together, this study reveals that ERK and JNK pathways synergistically regulate FGF2-induced liver cell proliferation via phosphorylating CREB, which will contribute to the understanding of FGF2 impact on liver cell proliferation and liver regeneration.

Key Anti-Fibrosis Associated Long Noncoding RNAs Identified in Human Hepatic Stellate Cell via Transcriptome Sequencing Analysis

Hepatic fibrosis is the main pathological basis for chronic cirrhosis, and activated hepatic stellate cells (HSCs) are the primary cells involved in liver fibrosis. Our study analyzed anti-fibrosis long noncoding RNAs (lncRNAs) in activated human HSCs (hHSCs). We performed RNA sequencing (RNA-seq) and bioinformatics analysis to determine whether lncRNA expression profile changes between hHSCs activation and quiescence. Eight differentially expressed (DE) lncRNAs and three pairs of co-expression lncRNAs-mRNAs were verified by quantitative Real-Time Polymerase Chain Reaction (qRT-PCR). A total of 34146 DE lncRNAs were identified in this study. Via gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, we found several DE lncRNAs regulated hHSC activation by participating in DNA bending/packaging complex, growth factor binding and the Hippo signaling pathway (p < 0.05). With lncRNA–mRNA co-expression analysis, three lncRNAs were identified to be associated with connective tissue growth factor (CTGF), fibroblast growth factor 2 (FGF2) and netrin-4 (NTN4). The quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) results of the eight DE lncRNAs and three pairs of co-expression lncRNAs–mRNAs were consistent with the RNA-seq data and previous reports. Several lncRNAs may serve as potential targets to reverse the progression of liver fibrosis. This study provides a first insight into lncRNA expression profile changes associated with activated human HSCs.

Binding of FGF2 to FGFR2 in an autocrine mode in trophectoderm cells is indispensable for mouse blastocyst formation through PKC-p38 pathway

Fibroblast growth factors (FGF1, FGF2 and FGF4) and fibroblast growth factor receptors (FGFR1, FGFR2, FGFR3 and FGFR4) have been reported to be expressed in preimplantation embryos and be required for their development. However, the functions of these molecules in trophectoderm cells (TEs) that lead to the formation of the blastocyst as well as the underlying mechanism have not been elucidated. The present study has demonstrated for the first time that endogenous FGF2 secreted by TEs can regulate protein expression and distribution in TEs via the FGFR2-mediated activation of PKC and p38, which are important for the development of expanded blastocysts. This finding provides the first explanation for the long-observed phenomenon that only high concentrations of exogenous FGFs have effects on embryonic development, but in vivo the amount of endogenous FGFs are trace. Besides, the present results suggest that FGF2/FGFR2 may act in an autocrine fashion and activate the downstream PKC/p38 pathway in TEs during expanded blastocyst formation.