Anti-adipogenic effect of PDGF is reversed by PKC inhibition

Predominant control of PDGF/PDGF receptor signaling in the migration and proliferation of human adipose‑derived stem cells under culture conditions with a combination of growth factors

Human adipose-derived stem cells (hASCs) play important roles in regenerative medicine and tissue engineering. However, their clinical applications are limited because of their instability during cell culture. Platelet lysates (PLTs) contain large amounts of growth factors that are useful for manufacturing cellular products. Platelet-derived growth factor (PDGF) is a major growth factor in PLTs and a potent mitogen in hASCs. To optimize growth conditions, the effects of a combination of growth factors on the promotion of hASC proliferation were investigated. Moreover, PDGF-BB combined with vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) markedly enhanced the viability of hASCs compared with the effects of PDGF-BB alone. Neither VEGF nor HGF had any effect alone. All growth factor receptor inhibitors inhibited cell proliferation. Wound healing assays revealed that VEGF and HGF stimulated PDGF-dependent cell migration. The effects of these growth factors on the activation of their cognate receptors and signaling enzymes were assessed using immunoblotting. Phosphorylation of PDGF receptor (PDGFR)β, VEGF receptor (VEGFR)2 and MET proto-oncogene and receptor tyrosine kinase was induced by PDGF-BB treatment, and was further increased by treatment with PDGF-BB/VEGF and PDGF-BB/HGF. The levels of phospho-ERK1/2 and phospho-p38MAPK were increased by these treatments in parallel. Furthermore, the expression levels of SRY-box transcription factor 2 and peroxisome proliferator-activated receptor g were increased in PDGF-BB-treated cells, and PDGF-BB played a dominant role in spheroid formation. The findings of the present study highlighted that PDGF/PDGFR signaling played a predominant role in the proliferation and migration of hASCs, and suggested that PDGF was responsible for the efficacy of other growth factors when hASCs were cultured with PLTs.

Role of hydrogen sulfide in the regulation of lipid metabolism: Implications on cardiovascular health

The World Health Organization (WHO) defines obesity as an urgency for health and a social emergency. Today around 39 % of people is overweight, of these over 13 % is obese. It is well-consolidated that the adipose cells are deputy to lipid storage under caloric excess; however, despite the classical idea that adipose tissue has exclusively a passive function, now it is known to be deeply involved in the regulation of systemic metabolism in physiological as well as under obesogenic conditions, with consequences on cardiovascular health. Beside two traditional types of adipose cells (white and brown), recently the beige one has been highlighted as the consequence of the healthy remodeling of white adipocytes, confirming their metabolic adaptability. In this direction, pharmacological, nutraceutical and nutrient-based approaches are addressed to positively influence inflammation and metabolism, thus contributing to reduce the obese-associated cardiovascular risk. In this scenario, hydrogen sulfide emerges as a new mediator that may regulate crucial targets involved in the regulation of metabolism. The current evidence demonstrates that hydrogen sulfide may induce peroxisome proliferator activated receptor γ (PPARγ), a crucial mediator of adipogenesis, inhibit the phosphorylation of perlipin-1 (plin-1), a protein implicated in the lipolysis, and finally promote browning process, through the release of irisin from skeletal muscle. The results summarized in this review suggest an important role of hydrogen sulfide in the regulation of metabolism and in the prevention/treatment of obese-associated cardiovascular diseases and propose new insight on the putative mechanisms underlying the release of hydrogen sulfide or its biosynthesis, delineating a further exciting field of application.

A chromatin accessibility landscape during early adipogenesis of human adipose-derived stem cells

Obesity has become a serious global public health problem; a deeper understanding of systemic change of chromatin accessibility during human adipogenesis contributes to conquering obesity and its related diseases. Here, we applied the ATAC-seq method to depict a high-quality genome‐wide time-resolved accessible chromatin atlas during adipogenesis of human adipose-derived stem cells (hASCs). Our data indicated that the chromatin accessibility drastic dynamically reformed during the adipogenesis of hASCs and 8 h may be the critical transition node of adipogenesis chromatin states from commitment phase to determination phase. Moreover, upon adipogenesis, we also found that the chromatin accessibility of regions related to anti-apoptotic, angiogenic and immunoregulatory gradually increased, which is beneficial to maintaining the health of adipose tissue (AT). Finally, the chromatin accessibility changed significantly in intronic regions of peroxisome proliferator‐activated receptor γ during adipogenesis, and these regions were rich in transcription factors binding motifs that were exposed for further regulation. Overall, we systematically analysed the complex change of chromatin accessibility occurring in the early stage of adipogenesis and deepened our understanding of human adipogenesis. Furthermore, we also provided a good reference data resource of genome‐wide chromatin accessibility for future studies on human adipogenesis.

Improved Recovery from Liver Fibrosis by Crenolanib

Chronic liver diseases are associated with excessive deposition of extracellular matrix proteins. This so-called fibrosis can progress to cirrhosis and impair vital functions of the liver. We examined whether the receptor tyrosine kinase (RTK) class III inhibitor Crenolanib affects the behavior of hepatic stellate cells (HSC) involved in fibrogenesis. Rats were treated with thioacetamide (TAA) for 18 weeks to trigger fibrosis. After TAA treatment, the animals received Crenolanib for two weeks, which significantly improved recovery from liver fibrosis. Because Crenolanib predominantly inhibits the RTK platelet-derived growth factor receptor-β, impaired HSC proliferation might be responsible for this beneficial effect. Interestingly, blocking of RTK signaling by Crenolanib not only hindered HSC proliferation but also triggered their specification into hepatic endoderm. Endodermal specification was mediated by p38 mitogen-activated kinase (p38 MAPK) and c-Jun-activated kinase (JNK) signaling; however, this process remained incomplete, and the HSC accumulated lipids. JNK activation was induced by stress response-associated inositol-requiring enzyme-1α (IRE1α) in response to Crenolanib treatment, whereas β-catenin-dependent WNT signaling was able to counteract this process. In conclusion, the Crenolanib-mediated inhibition of RTK impeded HSC proliferation and triggered stress responses, initiating developmental processes in HSC that might have contributed to improved recovery from liver fibrosis in TAA-treated rats.

The low molecular weight protein tyrosine phosphatase promotes adipogenesis and subcutaneous adipocyte hypertrophy

Obesity is a major contributing factor to the pathogenesis of Type 2 diabetes. Multiple human genetics studies suggest that high activity of the low molecular weight protein tyrosine phosphatase (LMPTP) promotes metabolic syndrome in obesity. We reported that LMPTP is a critical promoter of insulin resistance in obesity by regulating liver insulin receptor signaling and that inhibition of LMPTP reverses obesity-associated diabetes in mice. Since LMPTP is expressed in adipose tissue but little is known about its function, here we examined the role of LMPTP in adipocyte biology. Using conditional knockout mice, we found that selective deletion of LMPTP in adipocytes impaired obesity-induced subcutaneous adipocyte hypertrophy. We assessed the role of LMPTP in adipogenesis in vitro, and found that LMPTP deletion or knockdown substantially impaired differentiation of primary preadipocytes and 3T3-L1 cells into adipocytes, respectively. Inhibition of LMPTP in 3T3-L1 preadipocytes also reduced adipogenesis and expression of proadipogenic transcription factors peroxisome proliferator activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha. Inhibition of LMPTP increased basal phosphorylation of platelet-derived growth factor receptor alpha (PDGFRα) on activation motif residue Y849 in 3T3-L1, resulting in increased activation of the mitogen-associated protein kinases p38 and c-Jun N-terminal kinase and increased PPARγ phosphorylation on inhibitory residue S82. Analysis of the metabolome of differentiating 3T3-L1 cells suggested that LMPTP inhibition decreased cell glucose utilization while enhancing mitochondrial respiration and nucleotide synthesis. In summary, we report a novel role for LMPTP as a key driver of adipocyte differentiation via control of PDGFRα signaling.

Identification and characterization of adipose surface epitopes

Adipose tissue is a central regulator of metabolism and an important pharmacological target to treat the metabolic consequences of obesity, such as insulin resistance and dyslipidemia. Among the various cellular compartments, the adipocyte cell surface is especially appealing as a drug target as it contains various proteins that when activated or inhibited promote adipocyte health, change its endocrine function and eventually maintain or restore whole-body insulin sensitivity. In addition, cell surface proteins are readily accessible by various drug classes. However, targeting individual cell surface proteins in adipocytes has been difficult due to important functions of these proteins outside adipose tissue, raising various safety concerns. Thus, one of the biggest challenges is the lack of adipose selective surface proteins and/or targeting reagents. Here, we discuss several receptor families with an important function in adipogenesis and mature adipocytes to highlight the complexity at the cell surface and illustrate the problems with identifying adipose selective proteins. We then discuss that, while no unique adipocyte surface protein might exist, how splicing, posttranslational modifications as well as protein/protein interactions can create enormous diversity at the cell surface that vastly expands the space of potentially unique epitopes and how these selective epitopes can be identified and targeted.

Platelet-derived growth factor-BB and epidermal growth factor promote dairy goat spermatogonial stem cells proliferation via Ras/ERK1/2 signaling pathway

Spermatogonial stem cells (SSCs) have been used for the production of transgenic animals and for the recovery of male fertility. However, the proliferation of SSCs in vitro is still immature, and the mechanisms and pathways involved in the proliferation of SSCs are not clear. Here, the effects of platelet-derived growth factor-BB (PDGF-BB) and epidermal growth factor (EGF) on the proliferation of dairy goat SSCs in vitro were detected. The results showed that 20 ng/ml PDGF-BB or 25 ng/ml EGF was the optimum concentration, and that the BCL2 in the experimental groups was significantly higher than that in the control (P < 0.05), while BAX and BAD were dramatically downregulated (P < 0.05). The pERK1/2 in the experimental groups was about 3-5 times higher than that in the control. After the specific MEK1/2 inhibitor was added, BCL2 was reduced significantly (P < 0.001), while BAX and BAD were upregulated (P < 0.001). The expression of pERK1/2 decreased by 10%-30%. We speculated that these two growth factors may be mediated through the Ras/ERK1/2 signaling pathway to regulate the expression of pERK1/2 protein, and thus enhance the resistance of SSCs to apoptosis. However, further studies are needed to verify this hypothesis.

Fat Graft Enrichment Strategies: A Systematic Review

BACKGROUND

Autologous fat grafting is a dynamic modality used in plastic surgery as an adjunct to improve functional and aesthetic form. However, current practices in fat grafting for soft-tissue augmentation are plagued by tremendous variability in long-term graft retention, resulting in suboptimal outcomes and repetitive procedures. This systematic review identifies and critically appraises the evidence for various enrichment strategies that can be used to augment and improve the viability of fat grafts.

METHODS

A comprehensive literature search of the Medline and PubMed databases was conducted for animal and human studies published through October of 2017 with multiple search terms related to adipose graft enrichment agents encompassing growth factors, platelet-rich plasma, adipose-derived and bone marrow stem cells, gene therapy, tissue engineering, and other strategies. Data on level of evidence, techniques, complications, and outcomes were collected.

RESULTS

A total of 1382 articles were identified, of which 147 met inclusion criteria. The majority of enrichment strategies demonstrated positive benefit for fat graft survival, particularly with growth factors and adipose-derived stem cell enrichment. Platelet-rich plasma and adipose-derived stem cells had the strongest evidence to support efficacy in human studies and may demonstrate a dose-dependent effect.

CONCLUSIONS

Improved understanding of enrichment strategies contributing to fat graft survival can help to optimize safety and outcomes. Controlled clinical studies are lacking, and future studies should examine factors influencing graft survival through controlled clinical trials in order to establish safety and to obtain consistent outcomes.

Verification and Analysis of Sheep Tail Type-Associated PDGF-D Gene Polymorphisms

Simple Summary

PDGF-D can be considered a candidate gene for selection for sheep tail type. This study investigated genetic variation of the PDGF-D gene in sheep with different tail types verified at a cellular level and revealed the molecular mechanism of PDGF-D in sheep tail fat deposition. We detected a total of two SNPs among 533 sheep. g.4122606 C > G site was significantly correlated with tail length, and g.3852134 C > T site was significantly correlated with tail width. In addition, overexpression of PDGF-D in sheep preadipocytes can promote adipogenic differentiation. The PDGF-D gene may participate in sheep tail fat deposition and could be used for molecular marker-assisted selection of sheep tail type.

Abstract

The aim of this study was to examine the correlation between the platelet-derived growth factor-D (PDGF-D) gene and sheep tail type character and explore the potential underlying mechanism. A total of 533 sheep were included in this study. Polymorphic sites were examined by Pool-seq, and individual genotype identification and correlation analysis between tail type data were conducted using the matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS) method. JASPART website was used to predict transcription factor binding sites in the promoter region with and without PDGF-D gene mutation. The effect of PDGF-D on adipogenic differentiation of sheep preadipocytes was investigated. Two single nucleotide polymorphism sites were identified: g.4122606 C > G site was significantly correlated with tail length, and g.3852134 C > T site was significantly correlated with tail width. g.3852134 C > T was located in the promoter region. Six transcription factor binding sites were eliminated after promoter mutation, and three new transcription factor binding sites appeared. Expression levels of peroxisome proliferator-activated receptor gamma (PPARγ) and lipoproteinlipase (LPL) were significantly up-regulated upon PDGF-D overexpression. Oil red O staining showed increased small and large oil drops in the PDGF-D overexpression group. Together these results indicate the PDGF-D gene is an important gene controlling sheep tail shape and regulating sheep tail fat deposition to a certain degree.

Differences in gene expression profiles for subcutaneous adipose, liver, and skeletal muscle tissues between Meishan and Landrace pigs with different backfat thicknesses

Backfat thickness is one of the most important traits of commercially raised pigs. Meishan pigs are renowned for having thicker backfat than Landrace pigs. To examine the genetic factors responsible for the differences, we first produced female crossbred pig lines by mating Landrace (L) × Large White (W) × Duroc (D) females (LWD) with Landrace (L) or Meishan (M) boars (i.e., LWD × L = LWDL for Landrace offspring and LWD × M = LWDM for the Meishan offspring). We confirmed that LWDM pigs indeed had a thicker backfat than LWDL pigs. Next, we performed gene expression microarray analysis in both genetic lines to examine differentially expressed genes (DEGs) in energy metabolism-related tissues, subcutaneous adipose (fat), liver, and longissimus dorsi muscle tissues. We analyzed the annotation of DEGs (2-fold cutoff) to functionally categorize them by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. The number of DEGs in muscle tissues of both lines was much less than that in fat and liver tissues, indicating that DEGs in muscle tissues may not contribute much to differences in backfat thickness. In contrast, several genes related to muscle (in fat tissue) and lipid metabolism (in liver tissue) were more upregulated in LWDM pigs than LWDL pigs, indicating that those DEGs might be responsible for differences in backfat thickness. The different genome-wide gene expression profiles in the fat, liver, and muscle tissues between genetic lines can provide useful information for pig breeders.

Regulation of PKCβ levels and autophagy by PML is essential for high-glucose-dependent mesenchymal stem cell adipogenesis

BACKGROUND/OBJECTIVES

Obesity is a complex disease characterized by the accumulation of excess body fat, which is caused by an increase in adipose cell size and number. The major source of adipocytes comes from mesenchymal stem cells (MSCs), although their roles in obesity remain unclear. An understanding of the mechanisms, regulation, and outcomes of adipogenesis is crucial for the development of new treatments for obesity-related diseases. Recently an unexpected role for the tumor suppressor promyelocytic leukemia protein (PML) in hematopoietic stem cell biology and metabolism regulation has come to light, but its role in MSC biology remains unknown. Here, we investigated the molecular pathway underlying the role of PML in the control of adipogenic MSC differentiation.

SUBJECTS/METHODS

Muscle-derived stem cells (MDSCs) and adipose-derived stem cells (ADSCs) obtained from mice and voluntary patients (as a source of MSCs) were cultured in the presence of high glucose (HG) concentration, a nutrient stress condition known to promote MSCs differentiation into mature adipocytes and the adipogenic potential of PML was assessed.

RESULTS

PML is essential for a correct HG-dependent adipogenic differentiation, and the enhancement of PML levels is fundamental during adipogenesis. Increased PML expression enables the upregulation of protein kinase Cβ (PKCβ), which, in turn, by controlling autophagy levels permits an increase in peroxisome proliferator-activated receptor γ (PPARγ) that leads the adipogenic differentiation. Therefore, genetic and pharmacological depletion of PML prevents PKCβ expression, and by increasing autophagy levels, impairs the MSCs adipogenic differentiation. Human ADSCs isolated from overweight patients displayed increased PML and PKCβ levels compared to those found in normal weight individuals, indicating that the PML-PKCβ pathway is directly involved in the enhancement of adipogenesis and human metabolism.

CONCLUSIONS

The new link found among PML, PKCβ, and autophagy opens new therapeutic avenues for diseases characterized by an imbalance in the MSCs differentiation process, such as metabolic syndromes and cancer.

Comparative transcriptome analysis reveals potentially novel roles of Homeobox genes in adipose deposition in fat-tailed sheep

Adipose tissues are phenotypically, metabolically and functionally heterogeneous based on the sites of their deposition. Undesirable fat deposits in the body are often detrimental to animal and human health. To unravel the potential underlying mechanisms governing accumulation of adipose tissues in various regions of the body, i.e., subcutaneous (SAT), visceral (VAT) and tail (TAT), we profiled transcriptomes from Tan sheep, a Chinese indigenous breed with notable fat tail using RNA-seq. Upon comparison, we identified a total of 1,058 differentially expressed genes (DEGs) between the three adipose types (218, 324, and 795 in SAT/VAT, SAT/TAT, and VAT/TAT, respectively), from which several known key players were identified that are involved in lipid metabolic process, Wnt signals, Vitamin A metabolism, and transcriptional regulation of adipocyte differentiation. We also found that many elevated genes in VAT were notably enriched for key biological processes such as cytokine secretion, signaling molecule interaction and immune systems. Several developmental genes including HOXC11, HOXC12 and HOXC13, and adipose-expressed genes in the tail region, such as HOTAIR_2, HOTAIR_3 and SP9 were specially highlighted, indicating their strong associations with tail fat development in fat-tailed sheep. Our results provide new insight into exploring the specific fat deposition in tail, also contribute to the understanding of differences between adipose depots.

PDGFRα controls the balance of stromal and adipogenic cells during adipose tissue organogenesis

Adipose tissue is distributed in depots throughout the body with specialized roles in energy storage and thermogenesis. PDGFRα is a marker of adipocyte precursors, and increased PDGFRα activity causes adipose tissue fibrosis in adult mice. However, the function of PDGFRα during adipose tissue organogenesis is unknown. Here, by analyzing mice with juxtamembrane or kinase domain point mutations that increase PDGFRα activity (V561D or D842V), we found that PDGFRα activation inhibits embryonic white adipose tissue organogenesis in a tissue-autonomous manner. By lineage tracing analysis, we also found that collagen-expressing precursor fibroblasts differentiate into white adipocytes in the embryo. PDGFRα inhibited the formation of adipocytes from these precursors while favoring the formation of stromal fibroblasts. This imbalance between adipocytes and stromal cells was accompanied by overexpression of the cell fate regulator Zfp521. PDGFRα activation also inhibited the formation of juvenile beige adipocytes in the inguinal fat pad. Our data highlight the importance of balancing stromal versus adipogenic cell expansion during white adipose tissue development, with PDGFRα activity coordinating this crucial process in the embryo.

Inhibition of fat cell differentiation in 3T3-L1 pre-adipocytes by all-trans retinoic acid: Integrative analysis of transcriptomic and phenotypic data

The process of adipogenesis is controlled in a highly orchestrated manner, including transcriptional and post-transcriptional events. In developing 3T3-L1 pre-adipocytes, this program can be interrupted by all-trans retinoic acid (ATRA). To examine this inhibiting impact by ATRA, we generated large-scale transcriptomic data on the microRNA and mRNA level. Non-coding RNAs such as microRNAs represent a field in RNA turnover, which is very important for understanding the regulation of mRNA gene expression. High throughput mRNA and microRNA expression profiling was performed using mRNA hybridisation microarray technology and multiplexed expression assay for microRNA quantification. After quantitative measurements we merged expression data sets, integrated the results and analysed the molecular regulation of in vitro adipogenesis. For this purpose, we applied local enrichment analysis on the integrative microRNA-mRNA network determined by a linear regression approach. This approach includes the target predictions of TargetScan Mouse 5.2 and 23 pre-selected, significantly regulated microRNAs as well as Affymetrix microarray mRNA data. We found that the cellular lipid metabolism is negatively affected by ATRA. Furthermore, we were able to show that microRNA 27a and/or microRNA 96 are important regulators of gap junction signalling, the rearrangement of the actin cytoskeleton as well as the citric acid cycle, which represent the most affected pathways with regard to inhibitory effects of ATRA in 3T3-L1 preadipocytes. In conclusion, the experimental workflow and the integrative microRNA–mRNA data analysis shown in this study represent a possibility for illustrating interactions in highly orchestrated biological processes. Further the applied global microRNA–mRNA interaction network may also be used for the pre-selection of potential new biomarkers with regard to obesity or for the identification of new pharmaceutical targets.

Skin Adipocyte Stem Cell Self-Renewal Is Regulated by a PDGFA/AKT-Signaling Axis

Tissue growth and maintenance requires stem cell populations that self-renew, proliferate, and differentiate. Maintenance of white adipose tissue (WAT) requires the proliferation and differentiation of adipocyte stem cells (ASCs) to form postmitotic, lipid-filled mature adipocytes. Here we use the dynamic adipogenic program that occurs during hair growth to uncover an unrecognized regulator of ASC self-renewal and proliferation, PDGFA, which activates AKT signaling to drive and maintain the adipogenic program in the skin. Pdgfa expression is reduced in aged ASCs and is required for ASC proliferation and maintenance in the dermis, but not in other WATs. Our molecular and genetic studies uncover PI3K/AKT2 as a direct PDGFA target that is activated in ASCs during WAT hyperplasia and is functionally required for dermal ASC proliferation. Our data therefore reveal active mechanisms that regulate ASC self-renewal in the skin and show that distinct regulatory mechanisms operate in different WAT depots.

Shared genetic variants between serum levels of high-density lipoprotein cholesterol and wheezing in a cohort of children from Cyprus

Background

In a cohort of children in Cyprus, we recently reported low levels of high density lipoprotein cholesterol (HDL-C) to be associated with asthma. We examined whether genetic polymorphisms that were previously linked individually to asthma, obesity, or HDL-C are associated with both asthma and HDL-C levels in the Cyprus cohort.

Methods

We assessed genotypes frequencies in current-wheezers (n = 190) and non-asthmatic controls (n = 671) and HDL-C levels across several genotypes. Binary logistic regression models were used to assess the effect of genotypes on wheezing risk and examined whether this effect is carried out through changes of HDL–C.

Results

Of the 16 polymorphisms tested, two polymorphisms TNFa rs3093664 and PRKCA rs9892651 presented significant differences in genotype distribution among current-wheezers and controls. Higher HDL-C levels were noted in carriers of genotype GG of polymorphism TNFa rs3093664 that was protective for wheezing Vs AG and AA genotypes (65.3 Vs 51.8 and 53.3 mg/dl, p-value < 0.001 and p-value for trend = 0.028). In polymorphism PRKCA rs9892651, HDL-C levels were lower in carriers of CC and TC genotypes that were more frequent in current-wheezers Vs TT genotype (52.2 and 52.7 Vs 55.2 mg/dl, p-value = 0.042 and p-value for trend = 0.02). The association of TNFa rs3093664 with wheezing is partly mediated by its effect on HDL-C whereas association of PRKCA rs9892651 with wheezing appeared to be independent of HDL-C.

Conclusions

We found evidence that two SNPs located in different genetic loci, are associated with both wheezing and HDL-C levels, although more studies in other populations are needed to confirm our results.

Electronic supplementary material

The online version of this article (doi:10.1186/s13052-016-0276-1) contains supplementary material, which is available to authorized users.

Ahnak stimulates BMP2-mediated adipocyte differentiation through Smad1 activation

OBJECTIVE

Previous reports have indicated that Ahnak-deficient mice were protected from high-fat diet-induced obesity. However, the molecular mechanism in which Ahnak mediates adipocyte differentiation and high-fat diet-induced obesity is unclear.

METHODS

Adipocytes from Ahnak knockout (Ahnak(-/-) ) mice and knockdown of Ahnak in C3H10T1/2 were used to investigate the function of Ahnak in adipocyte differentiation. Ahnak-induced adipocyte differentiation was analyzed by Oil Red O staining.

RESULTS

Adipocytes from Ahnak(-/-) mice were smaller than those from wild-type mice. Silencing of Ahnak in C3H10T1/2 and adipose tissue-derived mesenchymal stem cells (ADSCs) from Ahnak(-/-) mice showed severely impaired adipocyte differentiation. Down-regulation of Ahnak in C3H10T1/2 cells and ADSCs from Ahnak(-/-) mice attenuated the phosphorylation and nuclear localization of Smad1 in response to BMP2, whereas Ahnak overexpression in 3T3-L1 cells significantly increased Smad1 activation. Because PPARγ is a well-known transcriptional factor in adipocyte differentiation, the PPARγ expression in Ahnak-mediated adipocyte differentiation was investigated. Transfection of C3H10T1/2 cells with Ahnak siRNA resulted in reduced PPARγ expression apparently through inhibited binding of Smad1 to the Smad1-binding site in the PPARγ promoter. These results suggest that Ahnak regulates adipogenesis by regulating Smad1-dependent PPARγ expression.

CONCLUSIONS

A molecular mechanism was proposed in which Ahnak regulates adipocyte differentiation through Smad1 activation.

Genome-Wide Specific Selection in Three Domestic Sheep Breeds

BACKGROUND

Commercial sheep raised for mutton grow faster than traditional Chinese sheep breeds. Here, we aimed to evaluate genetic selection among three different types of sheep breed: two well-known commercial mutton breeds and one indigenous Chinese breed.

RESULTS

We first combined locus-specific branch lengths and di statistical methods to detect candidate regions targeted by selection in the three different populations. The results showed that the genetic distances reached at least medium divergence for each pairwise combination. We found these two methods were highly correlated, and identified many growth-related candidate genes undergoing artificial selection. For production traits, APOBR and FTO are associated with body mass index. For meat traits, ALDOA, STK32B and FAM190A are related to marbling. For reproduction traits, CCNB2 and SLC8A3 affect oocyte development. We also found two well-known genes, GHR (which affects meat production and quality) and EDAR (associated with hair thickness) were associated with German mutton merino sheep. Furthermore, four genes (POL, RPL7, MSL1 and SHISA9) were associated with pre-weaning gain in our previous genome-wide association study.

CONCLUSIONS

Our results indicated that combine locus-specific branch lengths and di statistical approaches can reduce the searching ranges for specific selection. And we got many credible candidate genes which not only confirm the results of previous reports, but also provide a suite of novel candidate genes in defined breeds to guide hybridization breeding.

Genome-wide analysis reveals population structure and selection in Chinese indigenous sheep breeds

BACKGROUND

Traditionally, Chinese indigenous sheep were classified geographically and morphologically into three groups: Mongolian, Kazakh and Tibetan. Herein, we aimed to evaluate the population structure and genome selection among 140 individuals from ten representative Chinese indigenous sheep breeds: Ujimqin, Hu, Tong, Large-Tailed Han and Lop breed (Mongolian group); Duolang and Kazakh (Kazakh group); and Diqing, Plateau-type Tibetan, and Valley-type Tibetan breed (Tibetan group).

RESULTS

We analyzed the population using principal component analysis (PCA), STRUCTURE and a Neighbor-Joining (NJ)-tree. In PCA plot, the Tibetan and Mongolian groups were clustered as expected; however, Duolang and Kazakh (Kazakh group) were segregated. STRUCTURE analyses suggested two subpopulations: one from North China (Kazakh and Mongolian groups) and the other from the Southwest (Tibetan group). In the NJ-tree, the Tibetan group formed an independent branch and the Kazakh and Mongolian groups were mixed. We then used the d i statistic approach to reveal selection in Chinese indigenous sheep breeds. Among the 599 genome sequence windows analyzed, sixteen (2.7%) exhibited signatures of selection in four or more breeds. We detected three strong selection windows involving three functional genes: RXFP2, PPP1CC and PDGFD. PDGFD, one of the four subfamilies of PDGF, which promotes proliferation and inhibits differentiation of preadipocytes, was significantly selected in fat type breeds by the Rsb (across pairs of populations) approach. Two consecutive selection regions in Duolang sheep were obviously different to other breeds. One region was in OAR2 including three genes (NPR2, SPAG8 and HINT2) the influence growth traits. The other region was in OAR 6 including four genes (PKD2, SPP1, MEPE, and IBSP) associated with a milk production quantitative trait locus. We also identified known candidate genes such as BMPR1B, MSRB3, and three genes (KIT, MC1R, and FRY) that influence lambing percentage, ear size and coat phenotypes, respectively.

CONCLUSIONS

Based on the results presented here, we propose that Chinese native sheep can be divided into two genetic groups: the thin type (Tibetan group), and the fat type (Mongolian and Kazakh group). We also identified important genes that drive valuable phenotypes in Chinese indigenous sheep, especially PDGFD, which may influence fat deposition in fat type sheep.

Effect of phorbol 12-myristate 13-acetate on the differentiation of adipose-derived stromal cells from different subcutaneous adipose tissue depots

Human adipose-tissue-derived stromal cells (hADSCs) are abundant in adipose tissue and can differentiate into multi-lineage cell types, including adipocytes, osteoblasts, and chondrocytes. In order to define the optimal harvest site of adipose tissue harvest site, we solated hADSCs from different subcutaneous sites (upper abdomen, lower abdomen, and thigh) and compared their proliferation and potential to differentiate into adipocytes and osteoblasts. In addition, this study examined the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, on proliferation and differentiation of hADSCs to adipocytes or osteoblasts. hADSCs isolated from different subcutaneous depots have a similar growth rate. Fluorescence-activated cell sorting (FACS) analysis showed that the expression levels of CD73 and CD90 were similar between hADSCs from abdomen and thigh regions. However, the expression of CD105 was lower in hADSCs from the thigh than in those from the abdomen. Although the adipogenic differentiation potential of hADSCs from both tissue regions was similar, the osteogenic differentiation potential of hADSCs from the thigh was greater than that of hADSCs from the abdomen. Phorbol 12-myristate 13-acetate (PMA) treatment increased osteogenic differentiation and suppressed adipogenic differentiation of all hADSCs without affecting their growth rate and the treatment of Go6983, a general inhibitor of protein kinase C (PKC) blocked the PMA effect. These findings indicate that the thigh region might be a suitable source of hADSCs for bone regeneration and that the PKC signaling pathway may be involved in the adipogenic and osteogenic differentiation of hADSCs.

Pathway landscapes and epigenetic regulation in breast cancer and melanoma cell lines

BACKGROUND

Epigenetic variation is a main regulation mechanism of gene expression in various cancer histotypes, and due to its reversibility, the potential impact in therapy can be very relevant.

METHODS

Based on a selected pair, breast cancer (BC) and melanoma, we conducted inference analysis in parallel on a few cell lines (MCF-7 for BC and A375 for melanoma). Starting from differential expression after treatment with a demethylating agent, the 5-Aza-2'-deoxycytidine (DAC), we provided pathway enrichment analysis and gene regulatory maps with cross-linked microRNAs and transcription factors.

RESULTS

Several oncogenic signaling pathways altered upon DAC treatment were detected with significant enrichment. We represented the association between these cancers by depicting the landscape of common and specific variation affecting them.

Adipocyte lineages: tracing back the origins of fat

The obesity epidemic has intensified efforts to understand the mechanisms controlling adipose tissue development. Adipose tissue is generally classified as white adipose tissue (WAT), the major energy storing tissue, or brown adipose tissue (BAT), which mediates non-shivering thermogenesis. It is hypothesized that brite adipocytes (brown in white) may represent a third adipocyte class. The recent realization that brown fat exist in adult humans suggests increasing brown fat energy expenditure could be a therapeutic strategy to combat obesity. To understand adipose tissue development, several groups are tracing the origins of mature adipocytes back to their adult precursor and embryonic ancestors. From these studies emerged a model that brown adipocytes originate from a precursor shared with skeletal muscle that expresses Myf5-Cre, while all white adipocytes originate from a Myf5-negative precursors. While this provided a rational explanation to why BAT is more metabolically favorable than WAT, recent work indicates the situation is more complex because subsets of white adipocytes also arise from Myf5-Cre expressing precursors. Lineage tracing studies further suggest that the vasculature may provide a niche supporting both brown and white adipocyte progenitors; however, the identity of the adipocyte progenitor cell is under debate. Differences in origin between adipocytes could explain metabolic heterogeneity between depots and/or influence body fat patterning particularly in lipodystrophy disorders. Here, we discuss recent insights into adipose tissue origins highlighting lineage-tracing studies in mice, how variations in metabolism or signaling between lineages could affect body fat distribution, and the questions that remain unresolved. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

Prokineticin receptor 1 as a novel suppressor of preadipocyte proliferation and differentiation to control obesity

Background

Adipocyte renewal from preadipocytes occurs throughout the lifetime and contributes to obesity. To date, little is known about the mechanisms that control preadipocyte proliferation and differentiation. Prokineticin-2 is an angiogenic and anorexigenic hormone that activate two G protein-coupled receptors (GPCRs): PKR1 and PKR2. Prokineticin-2 regulates food intake and energy metabolism via central mechanisms (PKR2). The peripheral effect of prokineticin-2 on adipocytes/preadipocytes has not been studied yet.

Methodology/Principal Findings

Since adipocytes and preadipocytes express mainly prokineticin receptor-1 (PKR1), here, we explored the role of PKR1 in adipose tissue expansion, generating PKR1-null (PKR1^−/−) and adipocyte-specific (PKR1^ad−/−) mutant mice, and using murine and human preadipocyte cell lines. Both PKR1^−/− and PKR1^ad−/− had excessive abdominal adipose tissue, but only PKR1^−/− mice showed severe obesity and diabetes-like syndrome. PKR1^ad−/−) mice had increased proliferating preadipocytes and newly formed adipocyte levels, leading to expansion of adipose tissue. Using PKR1-knockdown in 3T3-L1 preadipocytes, we show that PKR1 directly inhibits preadipocyte proliferation and differentiation. These PKR1 cell autonomous actions appear targeted at preadipocyte cell cycle regulatory pathways, through reducing cyclin D, E, cdk2, c-Myc levels.

Conclusions/Significance

These results suggest PKR1 to be a crucial player in the preadipocyte proliferation and differentiation. Our data should facilitate studies of both the pathogenesis and therapy of obesity in humans.

The tail wagging the dog--regulation of lipid metabolism by protein kinase C

Upon their discovery almost 40 years ago, isoforms of the lipid-activated protein kinase C (PKC) family were initially regarded only as downstream effectors of the second messengers calcium and diacylglycerol, undergoing activation upon phospholipid hydrolysis in response to acute stimuli. Subsequently, several isoforms were found to be associated with the inhibitory effects of lipid over-supply on glucose homeostasis, especially the negative cross-talk with insulin signal transduction, observed upon accumulation of diacylglycerol in insulin target tissues. The PKC family has therefore attracted much attention in diabetes and obesity research, because intracellular lipid accumulation is strongly correlated with defective insulin action and the development of type 2 diabetes. Causal roles for various isoforms in the generation of insulin resistance have more recently been confirmed using PKC-deficient mice. However, during characterization of these animals, it became increasingly evident that the enzymes play key roles in the modulation of lipid metabolism itself, and may control the supply of lipids between tissues such as adipose and liver. Molecular studies have also demonstrated roles for PKC isoforms in several aspects of lipid metabolism, such as adipocyte differentiation and hepatic lipogenesis. While the precise mechanisms involved, especially the identities of protein substrates, are still unclear, the emerging picture suggests that the currently held view of the contribution of PKC isoforms to metabolism is an over-simplification. Although PKCs may inhibit insulin signal transduction, these enzymes are not merely downstream effectors of lipid accumulation, but in fact control the fate of fatty acids, thus the tail wags the dog.

Low FasL levels promote proliferation of human bone marrow-derived mesenchymal stem cells, higher levels inhibit their differentiation into adipocytes

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that can differentiate into several cell types. Bone marrow (BM)-MSCs mainly differentiate into osteoblasts or adipocytes. MSC interactions with their microenvironment directly affect their self-renewal/differentiation program. Here, we show for the first time that Fas ligand (FasL), a well-explored proapoptotic cytokine, can promote proliferation of BM-derived MSCs in vitro and inhibits their differentiation into adipocytes. BM-MSCs treated with a low FasL dose (0.5 ng/ml) proliferated more rapidly than untreated cells without undergoing spontaneous differentiation or apoptosis, whereas higher doses (25 ng/ml) induced significant though not massive BM-MSC death, with surviving cells maintaining a stem cell phenotype. At the molecular level, 0.5 ng/ml FasL induced ERK1/2 phosphorylation and survivin upregulation, whereas 25 ng/ml FasL induced caspase activation. Importantly, 25 ng/ml FasL reversibly prevented BM-MSC differentiation into adipocytes by modulating peroxisome proliferator-activated receptor gamma (PPARγ) and FABP4/aP2 expression induced by adipogenic medium. All such effects were inhibited by anti-Fas neutralizing antibody. The in vitro data regarding adipogenesis were confirmed using Fas(lpr) mutant mice, where higher PPARγ and FABP4/aP2 mRNA and protein levels were documented in whole tibia. These data show for the first time that the FasL/Fas system can have a role in BM-MSC biology via regulation of both proliferation and adipogenesis, and may have clinical relevance because circulating Fas/FasL levels decline with age and several age-related conditions, including osteoporosis, are characterized by adipocyte accumulation in BM.

Expression of cell surface markers during self-renewal and differentiation of human adipose-derived stem cells

Human adipose-derived stem cell populations express cell surface markers such as CD105, CD73, CD146 and CD140a/PDFGRα. However, it was unclear whether these markers could discriminate subpopulations of undifferentiated cells and whether the expression of these markers is modulated during differentiation. To address this issue, we analysed the immunophenotype of cultured human multipotent adipose derived stem (hMADS) cell populations at different adipocyte differentiation steps. We found that 100% of undifferentiated cells expressed CD73 and CD105. In contrast, CD146 and CD140a/PDFGRα marked two different subpopulations of cells. CD140a/PDGFRα subpopulation was regulated by FGF2, a critical factor of human adipose-derived stem cell self-renewal. During differentiation, CD73 was maintained and marked lipid-laden cells, whereas CD105 expression was inhibited in fully differentiated cells. The percentage of CD146 and CD140a/PDFGRα-positive cells declined as soon as cells had undergone differentiation. Altogether, these data support the notion that expanded adipose-derived stem cells are heterogeneous mixtures of cells and cell surface markers studied can discriminate subpopulations.

Differential expression of surface markers in mouse bone marrow mesenchymal stromal cell subpopulations with distinct lineage commitment

Bone marrow mesenchymal stromal cells (BM MSCs) represent a heterogeneous population of progenitors with potential for generation of skeletal tissues. However the identity of BM MSC subpopulations is poorly defined mainly due to the absence of specific markers allowing in situ localization of those cells and isolation of pure cell types. Here, we aimed at characterization of surface markers in mouse BM MSCs and in their subsets with distinct differentiation potential. Using conditionally immortalized BM MSCs we performed a screening with 176 antibodies and high-throughput flow cytometry, and found 33 markers expressed in MSCs, and among them 3 were novel for MSCs and 13 have not been reported for MSCs from mice. Furthermore, we obtained clonally derived MSC subpopulations and identified bipotential progenitors capable for osteo- and adipogenic differentiation, as well as monopotential osteogenic and adipogenic clones, and thus confirmed heterogeneity of MSCs. We found that expression of CD200 was characteristic for the clones with osteogenic potential, whereas SSEA4 marked adipogenic progenitors lacking osteogenic capacity, and CD140a was expressed in adipogenic cells independently of their efficiency for osteogenesis. We confirmed our observations in cell sorting experiments and further investigated the expression of those markers during the course of differentiation. Thus, our findings provide to our knowledge the most comprehensive characterization of surface antigens expression in mouse BM MSCs to date, and suggest CD200, SSEA4 and CD140a as markers differentially expressed in distinct types of MSC progenitors.

Generation and characterization of Tmeff2 mutant mice

TMEFF2 is a single-transmembrane protein containing one EGF-like and two follistatin-like domains. Some studies implicated TMEFF2 as a tumor suppressor for prostate and other cancers, whereas others reported TMEFF2 functioning as a growth factor for neurons and other cells. To gain insights into the apparently conflicting roles of TMEFF2, we generated a null allele of Tmeff2 gene by replacing its first coding exon with human placental alkaline phosphatase cDNA (Tmeff2(PLAP)). Tmeff2(PLAP/PLAP) homozygous mutant mice are born normal, but show growth retardation and die around weaning age. Tmeff2 is widely expressed in the nervous system, and the Tmeff2(PLAP) knock-in allele enables the visualization of neuronal innervations of skin and internal organs with a simple alkaline phosphatase staining. Tmeff2 is also highly expressed in prostate gland and white adipose tissues (WAT). However, with the exception of reduced WAT mass, extensive anatomical and molecular analyses failed to detect any structural or molecular abnormalities in the brain, the spinal cord, the enteric nervous system, or the prostate in the Tmeff2 mutants. No tumors were found in Tmeff2-mutant mice. The Tmeff2(PLAP/PLAP) knock-in mouse is an useful tool for studying the in vivo biological functions of TMEFF2.

The activation state of macrophages alters their ability to suppress preadipocyte apoptosis

Adipose tissue contains macrophages whose state of activation is regulated as obesity develops. Macrophage-secreted factors influence critical processes involved in adipose tissue homeostasis, including preadipocyte proliferation and differentiation into adipocytes. Macrophage-conditioned medium (MacCM) from J774A.1 macrophages protects 3T3-L1 preadipocytes from apoptosis through platelet-derived growth factor (PDGF) signaling. Here, we investigated the effect of macrophage activation on MacCM-dependent preadipocyte survival. MacCM was prepared following activation of either J774A.1 macrophages with lipopolysaccharide (LPS) or human primary monocyte-derived macrophages (MD-macrophages) with LPS or interleukin 4 (IL4). 3T3-L1 and human primary preadipocytes were induced to undergo apoptosis in MacCM, and apoptosis was quantified by cell enumeration or Hoechst nuclear staining. Preadipocyte PDGF signaling was assessed by immunoblot analysis of phosphorylated PDGF receptor, Akt, and ERK1/2. Pro-inflammatory activation of J774A.1 macrophages with LPS inhibited the pro-survival activity of MacCM on 3T3-L1 preadipocytes, despite intact PDGF signaling. Upregulation of macrophage tumor necrosis factor a (TNFα) expression occurred in response to LPS, and TNFα was demonstrated to be responsible for the inability of LPS-J774A.1-MacCM to inhibit preadipocyte apoptosis. Furthermore, MacCM from human MD-macrophages (MD-MacCM) inhibited apoptosis of primary human preadipocytes. MD-MacCM from LPS-treated macrophages, but not IL4-treated anti-inflammatory macrophages, was unable to protect human preadipocytes from cell death. In both murine cell lines and human primary cells, pro-inflammatory activation of macrophages inhibits their pro-survival activity, favoring preadipocyte death. These findings may be relevant to preadipocyte fate and adipose tissue remodeling in obesity.

Suppression of PDGF-induced PI3 kinase activity by imatinib promotes adipogenesis and adiponectin secretion

Improved glucose and lipid metabolism is a unique side effect of imatinib therapy in some chronic myeloid leukaemia (CML) patients. We recently reported that plasma levels of adiponectin, an important regulator of insulin sensitivity, are elevated following imatinib therapy in CML patients, which could account for these improved metabolic outcomes. Adiponectin is secreted exclusively from adipocytes, suggesting that imatinib modulates adiponectin levels directly, by transcriptional upregulation of adiponectin in pre-existing adipocytes, and/or indirectly, by stimulating adipogenesis. In this report, we have demonstrated that imatinib promotes adipogenic differentiation of human mesenchymal stromal cells (MSCs), which in turn secrete high-molecular-weight adiponectin. Conversely, imatinib does not stimulate adiponectin secretion from mature adipocytes. We hypothesise that inhibition of PDGFRα (PDGFRA) and PDGFRβ (PDGFRB) is the mechanism by which imatinib promotes adipogenesis. Supporting this, functional blocking antibodies to PDGFR promote adipogenesis and adiponectin secretion in MSC cultures. We have shown that imatinib is a potent inhibitor of PDGF-induced PI3 kinase activation and, using a PI3 kinase p110α-specific inhibitor (PIK-75), we have demonstrated that suppression of this pathway recapitulates the effects of imatinib on MSC differentiation. Furthermore, using mitogens that activate the PI3 kinase pathway, or MSCs expressing constitutively activated Akt, we have shown that activation of the PI3 kinase pathway negates the pro-adipogenic effects of imatinib. Taken together, our results suggest that imatinib increases plasma adiponectin levels by promoting adipogenesis through the suppression of PI3 kinase signalling downstream of PDGFR.

Adipose tissue stem cells meet preadipocyte commitment: going back to the future

White adipose tissue (WAT) is perhaps the most plastic organ in the body, capable of regeneration following surgical removal and massive expansion or contraction in response to altered energy balance. Research conducted for over 70 years has investigated adipose tissue plasticity on a cellular level, spurred on by the increasing burden that obesity and associated diseases are placing on public health globally. This work has identified committed preadipocytes in the stromal vascular fraction of adipose tissue and led to our current understanding that adipogenesis is important not only for WAT expansion, but also for maintenance of adipocyte numbers under normal metabolic states. At the turn of the millenium, studies investigating preadipocyte differentiation collided with developments in stem cell research, leading to the discovery of multipotent stem cells within WAT. Such adipose tissue-derived stem cells (ASCs) are capable of differentiating into numerous cell types of both mesodermal and nonmesodermal origin, leading to their extensive investigation from a therapeutic and tissue engineering perspective. However, the insights gained through studying ASCs have also contributed to more-recent progress in attempts to better characterize committed preadipocytes in adipose tissue. Thus, ASC research has gone back to its roots, thereby expanding our knowledge of preadipocyte commitment and adipose tissue biology.

PDGFRβ signaling regulates mural cell plasticity and inhibits fat development

Mural cells (pericytes and vascular smooth muscle cells) provide trophic and structural support to blood vessels. Vascular smooth muscle cells alternate between a synthetic/proliferative state and a differentiated/contractile state, but the dynamic states of pericytes are poorly understood. To explore the cues that regulate mural cell differentiation and homeostasis, we have generated conditional knockin mice with activating mutations at the PDGFRβ locus. We show that increased PDGFRβ signaling drives cell proliferation and downregulates differentiation genes in aortic vascular smooth muscle. Increased PDGFRβ signaling also induces a battery of immune response genes in pericytes and mesenchymal cells and inhibits differentiation of white adipocytes. Mural cells are emerging as multipotent progenitors of pathophysiological importance, and we identify PDGFRβ signaling as an important in vivo regulator of their progenitor potential.

Safe and effective gene transfer by adeno-associated virus of neonatal thymus-derived mesenchymal stromal cells

Recently, human neonatal thymus-derived mesenchymal stromal cells (nTMSCs) have been recognized as a promising mesenchymal stem cell source for combined cell and gene therapy. While efficient gene transfer is crucial for optimizing therapeutic efficacy, almost no studies have yet reported on the characteristics of nTMSC in terms of genetic modification. The present study investigates and realizes the potential of self-complementary adeno-associated viruses (scAAVs) as an effective transduction tool for nTMSCs. Transduction efficiency (TE), cytotoxicity and functional characteristics were determined in nTMSCs isolated from thymic tissues and transduced with scAAV1-6 and -8 serotypes expressing GFP. Our study confirms MSC-typical characteristics in nTMSCs and additionally, suggests further therapeutic advantages of nTMSCs due to its particularities with lower levels of MHC class I protein and higher levels of CD31 and CD34 expression. Effective transduction by scAAV2 and scAAV5 was evident in the majority of nTMSCs that were GFP-positive at a multiplicity of infection (MOI) of 1000. TE was further improved by higher MOI treatments. Transduced cells also successfully maintained adipocyte and vessel-forming endothelial cell multi-potency and showed no evidence of gene delivery-related cytotoxicity. Collectively, the data strongly suggest that scAAVs are promising technical platforms for safe and effective transgene expression in nTMSCs.

The inhibitory effects of PKCθ on adiponectin expression is mediated by ERK in 3T3-L1 adipocytes

The research suggests that adiponectin plays an important role in sensitizing insulin action. It is interesting to find that the lower levels of adiponectin exist in the plasma of obese and Type 2 diabetes subjects and in the adipose tissue of obese, db/db mice, and insulin-resistant individuals. However, the underlying mechanism by which adiponectin expression is inhibited remains largely unknown. In this study, we reported that adipogenesis was inhibited by the stable over-expression of protein kinase C θ (PKCθ) in 3T3-L1 pre - adipocytes. The prolonged treatment of mature 3T3-L1 adipocytes with palmitate, a kind of saturated free fatty acid, reduced adiponectin expression at both mRNA level and protein level, accompanied with the enhanced phosphorylation of PKCθ and extracellular signal-regulated kinase (ERK), and the impaired expression of peroxisome proliferator-activated receptor γ2 (PPARγ2) mRNA. Either PD98059, an ERK inhibitor or PKCθ pseudosubstrate, a specific PKCθ inhibitor, restored palmiate-inhibited PPARγ2 mRNA expression and subsequent adiponectin expression. In addition, the over-expression or activation of PKCθ resulted in the enhanced phosphorylation of ERK in the mature 3T3-L1 adipocytes. PKCθ pseudosubstrate significantly reduced the phorbol 3-myristate 12-acetate (PMA)-induced phosphorylation of ERK. The data suggested that PKCθ-dependent activity of ERK resulted in the impaired expression of PPARγ2 mRNA leading to the reduction of adiponectin expression in the mature 3T3-L1 adipocytes.

Analysis of human synovial and bone marrow mesenchymal stem cells in relation to heat-inactivation of autologous and fetal bovine serums

Background

Though sera are essential for Mesenchymal stem cells (MSCs), the effect of heat-inactivation remains unknown. Autologous human serum is recommended for clinical use; however, it is unclear whether differentiation potentials are maintained. To examine whether heat-inactivation of serum affected the proliferation and whether autologous human serum influenced their multipotentiality.

Methods

After whole blood collection, human synovium and bone marrow were harvested. Nucleated cells were expanded with autologous human serum and FBS.

Results

Heat-inactivation of autologous human serum enhanced proliferation of synovial MSCs. Heat-inactivation of each types of serum didn't affect calcification of synovial MSCs. The induction of calcification increased ALP activity, with the exception of bone marrow MSCs with autologous human serum. For adipogenesis of synovial MSCs, the Oil Red-O positive colony forming efficiency with autologous human serum was similar to or less than that with FBS.

Conclusion

These clarified the processing of human autologous serum and the influence of different sera for differentiation of synovial and bone marrow MSCs.

PDGF-Ralpha gene expression predicts proliferation, but PDGF-A suppresses transdifferentiation of neonatal mouse lung myofibroblasts

BACKGROUND

Platelet-derived growth factor A (PDGF-A) signals solely through PDGF-Ralpha, and is required for fibroblast proliferation and transdifferentiation (fibroblast to myofibroblast conversion) during alveolar development, because pdgfa-null mice lack both myofibroblasts and alveoli. However, these PDGF-A-mediated mechanisms remain incompletely defined. At postnatal days 4 and 12 (P4 and P12), using mouse lung fibroblasts, we examined (a) how PDGF-Ralpha correlates with ki67 (proliferation marker) or alpha-smooth muscle actin (alphaSMA, myofibroblast marker) expression, and (b) whether PDGF-A directly affects alphaSMA or modifies stimulation by transforming growth factor beta (TGFbeta).

METHODS

Using flow cytometry we examined PDGF-Ralpha, alphaSMA and Ki67 in mice which express green fluorescent protein (GFP) as a marker for PDGF-Ralpha expression. Using real-time RT-PCR we quantified alphaSMA mRNA in cultured Mlg neonatal mouse lung fibroblasts after treatment with PDGF-A, and/or TGFbeta.

RESULTS

The intensity of GFP-fluorescence enabled us to distinguish three groups of fibroblasts which exhibited absent, lower, or higher levels of PDGF-Ralpha. At P4, more of the higher than lower PDGF-Ralpha + fibroblasts contained Ki67 (Ki67+), and Ki67+ fibroblasts predominated in the alphaSMA + but not the alphaSMA- population. By P12, Ki67+ fibroblasts comprised a minority in both the PDGF-Ralpha + and alphaSMA+ populations. At P4, most Ki67+ fibroblasts were PDGF-Ralpha + and alphaSMA- whereas at P12, most Ki67+ fibroblasts were PDGF-Ralpha- and alphaSMA-. More of the PDGF-Ralpha + than - fibroblasts contained alphaSMA at both P4 and P12. In the lung, proximate alphaSMA was more abundant around nuclei in cells expressing high than low levels of PDGF-Ralpha at both P4 and P12. Nuclear SMAD 2/3 declined from P4 to P12 in PDGF-Ralpha-, but not in PDGF-Ralpha + cells. In Mlg fibroblasts, alphaSMA mRNA increased after exposure to TGFbeta, but declined after treatment with PDGF-A.

CONCLUSION

During both septal eruption (P4) and elongation (P12), alveolar PDGF-Ralpha may enhance the propensity of fibroblasts to transdifferentiate rather than directly stimulate alphaSMA, which preferentially localizes to non-proliferating fibroblasts. In accordance, PDGF-Ralpha more dominantly influences fibroblast proliferation at P4 than at P12. In the lung, TGFbeta may overshadow the antagonistic effects of PDGF-A/PDGF-Ralpha signaling, enhancing alphaSMA-abundance in PDGF-Ralpha-expressing fibroblasts.

Insulin sensitization of human preadipocytes through glucocorticoid hormone induction of forkhead transcription factors

Glucocorticoids are synthesized locally in adipose tissue and contribute to metabolic disease through the facilitation of adipose tissue expansion. Here we report that exposure of human primary preadipocytes to glucocorticoids increases their sensitivity to insulin and enhances their subsequent response to stimuli that promote differentiation. This effect was observed in primary human preadipocytes but not in immortalized 3T3-L1 murine preadipocytes or in fully differentiated primary human adipocytes. Stimulation of insulin signaling was mediated through induction of insulin receptor (IR), IR substrate protein 1 (IRS1), IRS2, and the p85 regulatory subunit of phosphoinositide-3-3-kinase, which led to enhanced insulin-mediated activation of Akt. Although induction of IRS2 was direct, induction of IR and IRS1 by glucocorticoids occurred subsequent to primary induction of the forkhead family transcription factors FoxO1A and FoxO3A. These results reveal a new role for glucocorticoids in preparing preadipocytes for differentiation.

PRKCA: a positional candidate gene for body mass index and asthma

Asthma incidence and prevalence are higher in obese individuals. A potential mechanistic basis for this relationship is pleiotropy. We hypothesized that significant linkage and candidate-gene association would be found for body mass index (BMI) in a population ascertained on asthma affection status. Linkage analysis for BMI was performed on 657 subjects in eight Costa Rican families enrolled in a study of asthma. Family-based association studies were conducted for BMI with SNPs within a positional candidate gene, PRKCA. SNPs within PRKCA were also tested for association with asthma. Association studies were conducted in 415 Costa Rican parent-child trios and 493 trios participating in the Childhood Asthma Management Program (CAMP). Although only modest evidence of linkage for BMI was obtained for the whole cohort, significant linkage was noted for BMI in females on chromosome 17q (peak LOD = 3.39). Four SNPs in a candidate gene in this region (PRKCA) had unadjusted association p values < 0.05 for BMI in both cohorts, with the joint p value for two SNPs remaining significant after adjustment for multiple comparisons (rs228883 and rs1005651, joint p values = 9.5 x 10(-)(5) and 5.6 x 10(-)(5)). Similarly, eight SNPs had unadjusted association p values < 0.05 for asthma in both populations, with one SNP remaining significant after adjustment for multiple comparisons (rs11079657, joint p value = 2.6 x 10(-)(5)). PRKCA is a pleiotropic locus that is associated with both BMI and asthma and that has been identified via linkage analysis of BMI in a population ascertained on asthma.

GO6976 prevents TNF-alpha-induced suppression of adiponectin expression in 3T3-L1 adipocytes: putative involvement of protein kinase C

Adiponectin, one of the adipokines secreted by adipocytes, possesses insulin sensitizing and anti-atherosclerotic properties. Tumor necrosis factor-alpha (TNF-alpha) is known to suppress the expression and secretion of adiponectin in adipocytes; however, the underlying mechanism remains poorly understood. Here, we demonstrate that GO6976 (a selective inhibitor of conventional protein kinase C (PKC)) prevents TNF-alpha-induced suppression of adiponectin secretion and expression in fully differentiated 3T3-L1 adipocytes, accompanied by attenuation of c-Jun N-terminal kinase (JNK) activation. Additionally, the transcriptional activity of peroxisome proliferator-activated receptor-gamma (PPARg) (a strong inducer of adiponectin) on the adiponectin promoter was inhibited in a PKC isoform-specific manner. These results raise the possibility that PKC is involved in TNF-alpha-induced suppression of adiponectin in 3T3-L1 adipocytes.

Activation of peroxisome proliferator-activated receptor-gamma by curcumin blocks the signaling pathways for PDGF and EGF in hepatic stellate cells

During hepatic fibrogenesis, reduction in the abundance of peroxisome proliferator-activated receptor-gamma (PPARgamma) is accompanied by activation of mitogenic signaling for platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) in hepatic stellate cells (HSCs), the major effector cells. We previously reported that curcumin, the yellow pigment in curry, interrupted PDGF and EGF signaling, stimulated PPARgamma gene expression, and enhanced its activity, leading to inhibition of cell proliferation of activated HSC in vitro and in vivo. The aim of this study was to elucidate the underlying mechanisms. We hypothesized that the enhancement of PPARgamma activity by curcumin might result in the interruption of PDGF and EGF signaling. Our experiments demonstrated that curcumin, with different treatment strategies, showed different efficiencies in the inhibition of PDGF- or EGF-stimulated HSC proliferation. Further experiments observed that curcumin dose dependently reduced gene expression of PDGF and EGF receptors (ie, PDGF-betaR and EGFR), which required PPARgamma activation. The activation of PPARgamma by its agonist suppressed pdgf-betar and egfr expression in HSC. In addition, curcumin reduced the phosphorylation levels of PDGF-betaR and EGFR, as well as their downstream signaling cascades, including ERK1/2 and JNK1/2. Moreover, activation of PPARgamma induced gene expression of glutamate-cysteine ligase, the rate-limiting enzyme in de novo synthesis of the major intracellular antioxidant, glutathione. De novo synthesis of glutathione was required for curcumin to suppress pdgf-betar and egfr expression in activated HSCs. Our results collectively demonstrated that enhancement of PPARgamma activity by curcumin interrupted PDGF and EGF signaling in activated HSCs by reducing the phosphorylation levels of PDGF-betaR and EGFR, and by suppressing the receptor gene expression. These results provide novel insights into the mechanisms of curcumin in the inhibition of HSC activation and the suppression of hepatic fibrogenesis.

Effect of local, long-term delivery of platelet-derived growth factor (PDGF) on injected fat graft survival in severe combined immunodeficient (SCID) mice

SUMMARY BACKGROUND

Autogenous fat injection is widely used for the correction of acquired and congenital soft tissue defects. However, the high absorption rate results in the need for over-correction of the defect and repeat procedures. We hypothesised that platelet-derived growth factor (PDGF), a potent mitogen and known stimulant for murine preadipocytes, would improve fat graft survival when concentrations were sustained with a gelatine microsphere delivery system.

METHODS

Abdominal fat was harvested from an otherwise healthy 43-year-old woman during a breast reconstruction. Prior to subdermal injection into severe combined immunodeficient (SCID) mice, the fat grafts were divided into 1-ml aliquots, mixed with microspheres bound to PDGF, free PDGF, or nothing depending on its experimental group, and weighed. The following experimental groups were thus created (minimum n=8 per group): (1) fat graft control, (2) fat graft with free PDGF, (3) fat graft with blank microspheres, and (4) fat graft with microspheres bound to PDGF. After 12 weeks, the fat xenografts were harvested for analysis of weight maintenance and histological and morphometric evaluation.

RESULTS

The addition of PDGF bound to gelatine microspheres was effective in improving xenograft weight maintenance (P=0.018) and preservation of adipose tissue architecture (P<0.0005) compared to controls at 3 months. The microspheres were completely absorbed at 12 weeks.

CONCLUSIONS

Sustained, local delivery of PDGF via a gelatine microsphere delivery system resulted in improved weight maintenance of the xenografts with greater preservation of adipose tissue architecture at 3 months compared to controls.

Long-term imatinib therapy promotes bone formation in CML patients

Imatinib inhibits tyrosine kinases important in osteoclast (c-Fms) and osteoblast (platelet-derived growth factor receptor [PDGF-R], c-Abl) function, suggesting that long-term therapy may alter bone homeostasis. To investigate this question, we measured the trabecular bone volume (TBV) in iliac crest bone biopsies taken from chronic myeloid leukemia (CML) patients at diagnosis and again after 2 to 4 years of imatinib therapy. Half the patients (8 of 17) showed a substantive increase in TBV (> 2-fold), after imatinib therapy, with the TBV in the posttreatment biopsy typically surpassing the normal upper limit for the patient's age group. Imatinib-treated patients exhibited reduced serum calcium and phosphate levels with hypophosphatemia evident in 53% (9 of 17) of patients. In vitro, imatinib suppressed osteoblast proliferation and stimulated osteogenic gene expression and mineralized-matrix production by inhibiting PDGF receptor function. In PDGF-stimulated cultures, imatinib dose-dependently inhibited activation of Akt and Crk-L. Using pharmacologic inhibitors, inhibition of PI3-kinase/Akt activation promoted mineral formation, suggesting a possible molecular mechanism for the imatinib-mediated increase in TBV in vivo. Further investigation is required to determine whether the increase in TBV associated with imatinib therapy may represent a novel therapeutic avenue for the treatment of diseases that are characterized by generalized bone loss.

Platelet-Derived Growth Factor Receptor Regulates Myeloid and Monocytic Differentiation of HL-60 Cells

Here, we show that the platelet-derived growth factor receptor (PDGFR) regulates myeloid and monocytic differentiation of HL-60 myeloblastic leukemia cells in response to retinoic acid (RA) and vitamin D3 (D3), respectively. Both RA and D3 decreased the expression of PDGFR-alpha and PDGFR-beta throughout differentiation. When cells were treated with the PDGFR inhibitor AG1296 in addition to RA or D3, signs of terminal differentiation such as inducible oxidative metabolism and cell substrate adhesion were enhanced. These changes were accompanied by an increased extracellular signal-regulated kinase 1/2 activation. AG1296 also resulted in elevated expression of differentiation markers CD11b and CD66c when administered with RA or D3. Interestingly, other markers did not follow the same pattern. Cells receiving AG1296 in addition to RA or D3 showed decreased G1-G0 arrest and CD14, CD38, and CD89 expression. We thus provide evidence that certain sets of differentiation markers can be enhanced, whereas others can be inhibited by the PDGFR pathway. In addition, we found calcium levels to be decreased by RA and D3 but increased when AG1296 was given in addition to RA or D3, suggesting that calcium levels decrease during myeloid or monocytic differentiation, and elevated calcium levels can disturb the expression of certain differentiation markers.

The interruption of the PDGF and EGF signaling pathways by curcumin stimulates gene expression of PPARgamma in rat activated hepatic stellate cell in vitro

Activation of hepatic stellate cells (HSC), the major effector in hepatic fibrogenesis, is coupled with sequential alterations in expression of genes, including the upregulation of platelet-derived growth factor-beta receptor (PDGF-betaR) and epidermal growth factor receptor (EGFR), as well as the down-regulation of the peroxisome proliferator-activated receptor-gamma (PPARgamma). However, the relationship among the alterations in expression of the genes and the activation of their signaling in activated HSC remains obscure. We recently showed that curcumin, the yellow pigment in curry, inhibited cell growth and induced gene expression of endogenous PPARgamma in activated HSC in vitro. The present study is to elucidate the underlying mechanisms, focusing on the impacts of PDGF and EGF signaling. It is hypothesized that the interruption of the PDGF and EGF signaling pathways by curcumin might stimulate gene expression of PPARgamma in activated HSC. Our results in this report indicate that the activation of PDGF or EGF signaling by exogenous PDGF or EGF inhibits PPARgamma gene expression in passaged HSC. Curcumin interrupts PDGF and EGF signaling demonstrated by inhibiting tyrosine phosphorylation of PDGF-betaR and EGFR and by reducing the levels of phosphorylated phosphatidylinositol-3 kinase (PI-3K/AKT), extracellular signal-regulated kinase (ERK) and the Jun N-terminal kinase (JNK). The blockade of PI-3K/AKT, ERK or JNK signaling negatively regulates PPARgamma gene expression in activated HSC, leading to the reduction in cell growth, including inducing cell arrest and apoptosis. Our results collectively demonstrate that the interruption of the PDGF and EGF signaling pathways by curcumin stimulates gene expression of PPARgamma in activated HSC. These results provide novel insights into the mechanisms of curcumin in the induction of PPARgamma gene expression in activated HSC.

Subcutaneous fat in normal and diseased states

The quest for effective strategies to treat obesity has propelled fat research into an exploration of the molecular processes that drive adipocyte formation, and hence body fat mass. The development of obesity is dependent on the coordinated interplay of adipocyte hypertrophy (increased fat cell size), adipocyte hyperplasia (increased fat cell number), and angiogenesis. Evidence suggests that adipocyte hyperplasia, or adipogenesis, occurs throughout life, both in response to normal cell turnover as well as in response to the need for additional fat mass stores that arises when caloric intake exceeds nutritional requirements. Adipogenesis involves two major events-the recruitment and proliferation of adipocyte precursor cells, called preadipocytes, followed by the subsequent conversion of preadipocytes, or differentiation, into mature fat cells. In vitro studies using experimental and primary preadipocyte cell lines have uncovered the mechanisms that drive the adipogenic process, a tightly controlled sequence of events guided by the strict temporal regulation of multiple inhibitory and stimulatory signaling events involving regulators of cell-cycle functions and differentiation factors. This article reviews the current understanding of adipogenesis with emphasis on the various stages of adipocyte development; on key hormonal, nutritional, paracrine, and neuronal control signals; as well as on the components involved in cell-cell or cell-matrix interactions that are pivotal in regulating fat cell formation. Special consideration is given to clinical applications derived from adipogenesis research with impact on medical, surgical and cosmetic fields.

Regulation of PDGF-stimulated SHIP2 tyrosine phosphorylation and association with Shc in 3T3-L1 preadipocytes

In 3T3-L1 and human preadipocytes, insulin results in the isolated rise in phosphatidylinositol (PI)-3,4,5-P3, whereas PDGF produces PI(3,4)P2 in addition to PI(3,4,5)P3. SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) converts PI(3,4,5)P3 into PI(3,4)P2. PDGF, but not insulin, stimulates SHIP2 tyrosine phosphorylation and its association with Shc in human and 3T3-L1 preadipocytes. We now demonstrate that SHIP2 tyrosine phosphorylation and association with Shc in PDGF-treated 3T3-L1 preadipocytes was reduced by bisindolylmaleimide I (BisI), an inhibitor of conventional/novel protein kinase C (PKC). However, the production of PI(3,4)P2 and PI(3,4,5)P3 by PDGF was unaffected by BisI. Activation of PKC by 12-O-tetradecanoylphorbol-13-acetate (TPA) was not sufficient to induce SHIP2 tyrosine phosphorylation. Furthermore, we identified threonine 958 (T958) as a novel PDGF-responsive SHIP2 phosphorylation site. Mutation of T958 to alanine reduced PDGF-stimulated SHIP2 tyrosine phosphorylation and association with Shc, but did not alter its anti-proliferative effect on preadipocytes. This study demonstrates that SHIP2 tyrosine phosphorylation and Shc association can be regulated by serine/threonine signaling pathways, either indirectly (via PKC), or directly (via T958). Interestingly, the anti-proliferative effect of SHIP2 T958A, as well as another SHIP2 mutant (Y986F, Y987F) that also displays defective tyrosine phosphorylation and Shc association, does not depend on these molecular events.

PDGF essentially links TGF-beta signaling to nuclear beta-catenin accumulation in hepatocellular carcinoma progression

The cooperation of Ras - extracellular signal-regulated kinase/mitogen-activated protein kinase and transforming growth factor (TGF)-beta signaling provokes an epithelial to mesenchymal transition (EMT) of differentiated p19(ARF) null hepatocytes, which is accompanied by a shift in malignancy and gain of metastatic properties. Upon EMT, TGF-beta induces the secretion and autocrine regulation of platelet-derived growth factor (PDGF) by upregulation of PDGF-A and both PDGF receptors. Here, we demonstrate by loss-of-function analyses that PDGF provides adhesive and migratory properties in vitro as well as proliferative stimuli during tumor formation. PDGF signaling resulted in the activation of phosphatidylinositol-3 kinase, and furthermore associated with nuclear beta-catenin accumulation upon EMT. Hepatocytes expressing constitutively active beta-catenin or its negative regulator Axin were employed to study the impact of nuclear beta-catenin. Unexpectedly, active beta-catenin failed to accelerate proliferation during tumor formation, but in contrast, correlated with growth arrest. Nuclear localization of beta-catenin was accompanied by strong expression of the Cdk inhibitor p16(INK4A) and the concomitant induction of the beta-catenin target genes cyclin D1 and c-myc. In addition, active beta-catenin revealed protection of malignant hepatocytes against anoikis, which provides a prerequisite for the dissemination of carcinoma. From these data, we conclude that TGF-beta acts tumor progressive by induction of PDGF signaling and subsequent activation of beta-catenin, which endows a subpopulation of neoplastic hepatocytes with features of cancer stem cells..

Different roles of protein kinase C-betaI and -delta in the regulation of adipocyte differentiation

Protein kinase C (PKC) is a member of serine/threonine protein kinase family that plays important roles in the control of vast variety of cellular functions. Nevertheless, the regulatory effect of PKC on adipogenesis remained not well understood. In this study, we investigated the effect of several PKC isoforms on the adipogenic conversion of 3T3-L1 preadipocytes induced by dexamethasone, isobutylmethylxanthine and insulin. Treatment of cells with broad-spectrum PKC inhibitor Rö318220 suppressed the adipogenesis. Gö6976, a selective inhibitor for PKC isoforms-alpha, -betaI and -mu, also inhibited the adipogenesis of cells. Pretreatment of cells with peroxisomal proliferator activated receptor-gamma (PPARgamma) agonist troglitazone abolished the inhibitory effect of Gö6976 on adipogenesis. The plasmic membrane translocation of PKC-betaI was observed at the first 2 days of differentiation. Whereas no translocation of PKC-alpha and -mu was observed. Overexpression of dominant negative PKC-betaI, but not wild-type PKC-betaI, blocked adipogenesis. This effect of dominant negative PKC-betaI can be reversed by troglitazone, suggesting that PKC-betaI is required for the initiation of adipogenesis. In addition, rottlerin, a specific inhibitor of PKC-delta, can reverse the suppression of adipogenesis mediated by 12-O-tetradecanoyl-phorbol-13-acetate, transforming growth factor-beta1, and epidermal growth factor. These data suggest that PKC-betaI is important in the induction of adipogenesis, while the PKC-delta has an inhibitory role for adipogenesis.