Monocyte chemoattractant protein-1 and nitric oxide promote adipogenesis in a model that mimics obesity

Analysis of Transcriptome Differences Between Subcutaneous and Intramuscular Adipose Tissue of Tibetan Pigs

Background/Objectives: Fat deposition traits in pigs directly influence pork flavor, tenderness, and juiciness and are closely linked to overall pork quality. The Tibetan pig, an indigenous breed in China, not only possesses a high intramuscular fat content but also exhibits a unique fat metabolism pattern due to long-term adaptation to harsh environments. This makes it an excellent genetic and physiological model for investigating fat deposition characteristics. Adipose tissue from different body regions displays varying morphologies, cytokines, and adipokines. This study aimed to examine adipose tissue deposition characteristics in different parts of Tibetan pigs and provide additional data to explore the underlying mechanisms of differential fat deposition. Methods: Our research identified significant differences in the morphology and gene expression patterns between subcutaneous fat (abdominal fat [AF] and back fat [BF]) and intramuscular fat (IMF) in Tibetan pigs. Results: Histological observations revealed that subcutaneous fat cells were significantly larger in area and diameter compared to IMF cells. The transcriptomic analysis further identified differentially expressed genes (DEGs) between subcutaneous fat and IMF, with a total of 65 DEGs in BF vs. IMF and 347 DEGs in AF vs. IMF, including 25 DEGs common to both comparisons. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that these genes were significantly associated with lipid metabolism-related signaling pathways, such as the Wnt, mTOR, and PI3K-Akt signaling pathways. Several DEGs, including DDAH1, ADRA1B, SLCO3A1, and THBS3, may be linked to the differences in fat deposition in different parts of Tibetan pigs, thereby affecting meat quality and nutritional value. Conclusions: These findings provide new insights into the unique fat distribution and deposition characteristics of Tibetan pigs and establish a foundation for breeding strategies aimed at improving pork quality.

Uncoupling Lipid Synthesis from Adipocyte Development

Obesity results from the expansion of adipose tissue, a versatile tissue regulating energy homeostasis, adipokine secretion, thermogenesis, and inflammation. The primary function of adipocytes is thought to be lipid storage through lipid synthesis, which is presumably intertwined with adipogenesis. However, during prolonged fasting, adipocytes are depleted of lipid droplets yet retain endocrine function and an instant response to nutrients. This observation led us to question whether lipid synthesis and storage can be uncoupled from adipogenesis and adipocyte function. By inhibiting key enzymes in the lipid synthesis pathway during adipocyte development, we demonstrated that a basal level of lipid synthesis is essential for adipogenesis initiation but not for maturation and maintenance of adipocyte identity. Furthermore, inducing dedifferentiation of mature adipocytes abrogated adipocyte identity but not lipid storage. These findings suggest that lipid synthesis and storage are not the defining features of adipocytes and raise the possibility of uncoupling lipid synthesis from adipocyte development to achieve smaller and healthier adipocytes for the treatment of obesity and related disorders.

Autophagy in adipogenesis: Molecular mechanisms and regulation by bioactive compounds

White adipose tissue expands rapidly due to increased adipocyte number (hyperplasia) and size (hypertrophy), which results in obesity. Adipogenesis is a process of the formation of mature adipocytes from precursor cells. Additionally, obesity-related metabolic complications, such as fatty liver and insulin resistance, are linked to adipogenesis. On the contrary, autophagy is a catabolic process; essential to maintain cellular homeostasis via the degradation or recycling of unnecessary or damaged components. Importantly, autophagy dictates obesity and adipogenesis. Hence, a clear understanding of how autophagy regulates adipogenesis is crucial for drug development and the prevention and treatment of obesity and its associated disorders, such as type 2 diabetes, cardiovascular disease, and cancer. In this review, we highlighted recent findings regarding the crosstalk between adipogenesis and autophagy, as well as the molecules involved. Furthermore, the review discussed how bioactive compounds regulate adipogenesis by manipulating autophagy and underlying molecular mechanisms. Based on in vitro and animal studies, we summarized the effects of bioactive compounds on adipogenesis and autophagy. Hence, human studies are necessary to validate the effectiveness and optimal dosage of these bioactive compounds.

Chemokine (C-C motif) ligand 2-enhanced adipogenesis and angiogenesis of human adipose-derived stem cell and human umbilical vein endothelial cell co-culture system in adipose tissue engineering

Human adipose-derived stem cells (hADSCs) and human umbilical vein endothelial cells (HUVECs) co-cultured in vitro are widely used in adipose tissue engineering but exhibit various limitations. Chemokine (C-C motif) ligand 2 (CCL2) has been proved essential during adipogenesis and angiogenesis in vivo. We examined whether adipogenesis and angiogenesis could also be directly promoted by CCL2 in vitro. Cells were cultured with 0, 10, 50, and 100 ng/ml CCL2. The effects of CCL2 on adipogenesis of hADSCs, and lipid accumulation in the positive control group (hADSCs), blank control group (hADSCs + HUVECs), and experimental group (hADSCs + HUVECs + CCL2) in the hADSC and HUVEC direct co-culture system were evaluated by Oil Red O staining. Angiogenesis in the presence of CCL2 was evaluated by Matrigel tube formation assay. Angiogenic- and adipogenic-associated gene and protein expression in the co-culture system were measured by Quantitative Real-time Polymerase Chain Reaction and western blotting, respectively. All concentrations of CCL2 promoted hADSC adipogenic differentiation and HUVEC tube formation (P < 0.05). Following direct co-culture, the experimental group accumulated more lipid droplets than the positive control (P < 0.0001), whereas the latter showed better adipogenesis than the blank control group. 50 ng/ml CCL2 exhibited stronger adipogenic and angiogenic potential than other concentrations. After 72 h of direct co-culture, the mRNA expression of adipogenic differentiation (peroxisome proliferators-activated receptorsγ, CCAAT/enhancer binding protein-α, Leptin, and lipoprotein lipase) and angiogenic genes (vascular endothelial growth factor-A, vascular endothelial growth factor receptor 2, matrix metalloprotein (MMP) 9, and 14) in the experimental group was much higher than in the control (P < 0.05). The addition of 50 ng/ml CCL2 in the system resulted in elevated phosphorylated Protein kinase B/AKT expression. In summary, CCL2 directly promoted adipogenesis of hADSCs and angiogenesis of HUVECs under both mono-culture and co-culture condition in vitro possibly by enhancing AKT phosphorylation. An optimal concentration of 50 ng/ml CCL2 could improve the adipogenesis and angiogenesis of hADSC and HUVEC co-culture system.

Knockout of NOS2 Promotes Adipogenic Differentiation of Rat MSCs by Enhancing Activation of JAK/STAT3 Signaling

Mesenchymal stromal cells (MSCs) are a heterogeneous population of cells that possess multilineage differentiation potential and extensive immunomodulatory properties. In mice and rats, MSCs produce nitric oxide (NO), as immunomodulatory effector molecule that exerts an antiproliferative effect on T cells, while the role of NO in differentiation was less clear. Here, we investigated the role of NO synthase 2 (NOS2) on adipogenic and osteogenic differentiation of rat MSCs. MSCs isolated from NOS2-null (NOS2^–/–) and wild type (WT) Sprague–Dawley (SD) rats exhibited homogenous fibroblast-like morphology and characteristic phenotypes. However, after induction, adipogenic differentiation was found significantly promoted in NOS2^–/– MSCs compared to WT MSCs, but not in osteogenic differentiation. Accordingly, qRT-PCR revealed that the adipogenesis-related genes PPAR-γ, C/EBP-α, LPL and FABP4 were markedly upregulated in NOS2^–/– MSCs, but not for osteogenic transcription factors or marker genes. Further investigations revealed that the significant enhancement of adipogenic differentiation in NOS2^–/– MSCs was due to overactivation of the STAT3 signaling pathway. Both AG490 and S3I-201, small molecule inhibitors that selectively inhibit STAT3 activation, reversed this adipogenic effect. Furthermore, after high-fat diet (HFD) feeding, knockout of NOS2 in rat MSCs resulted in significant obesity. In summary, NOS2 is involved in the regulation of rat MSC adipogenic differentiation via the STAT3 signaling pathway.

Inflammation Precedes Fat Deposition in an Experimental Model of Lymphedema

Background: Chronic lymphedema is a common complication of lymphatic obstruction, particularly after cancer treatment, characterized by an increased volume of the affected extremity, partly caused by the accumulation of excessive adipose tissue. The relationship between lymph vessels' obstruction and fat deposit is, however, poorly understood. Objective: Our central hypothesis was that the inflammatory process caused by lymph stasis precedes the adipocyte differentiation and fat deposition. Methods and Results: We used a modified mouse tail model to produce secondary lymphedema. Animals were treated with dexamethasone, or the procedure was performed in nitric oxide synthase 2 (NOS2)-deficient mice to evaluate the role of inflammation in lymphedema formation. Adipose tissue (Lipin) and inflammatory markers (IL-6, MCP-1, and F4-80) were analyzed in histological samples and by quantitative polymerase chain reaction. We observed an increased deposition of fat into the affected area that starts 3 weeks after lymph vessel ligation; it further increased after 6 weeks. Genes involved in the inflammatory process were upregulated before adipocyte maturation. Treatment with dexamethasone or the use of inducible nitric oxide synthase knockout mice blocked the inflammatory reaction and inhibited the accumulation of fat distal to the lymphatic obstruction. Conclusion: In the modified mouse tail lymphedema, inflammation precedes adipogenesis. Our data suggest that MCP-1 and nitric oxide may be potential targets for lymphedema management.

In vivo tissue engineering of an adipose tissue flap using fat grafts and Adipogel

For decades, plastic surgeons have spent considerable effort exploring anatomical regions for free flap design. More recently, tissue-engineering approaches have been utilised in an attempt to grow transplantable tissue flaps in vivo. The aim of this study was to engineer a fat flap with a vascular pedicle by combining autologous fat grafts and a novel acellular hydrogel (Adipogel) in an established tissue-engineering model comprising a chamber and blood vessel loop. An arteriovenous loop was created in the rat groin from the femoral vessels and positioned inside a perforated polycarbonate chamber. In Group 1, the chamber contained minced, centrifuged autologous fat; in Group 2, Adipogel was added to the graft; and in Group 3, Adipogel alone was used. Constructs were histologically examined at 6 and 12 weeks. In all groups, new tissue was generated. Adipocytes, although appearing viable in the graft at the time of insertion, were predominantly nonviable at 6 weeks. However, by 12 weeks, new fat had formed in all groups and was significantly greater in the combined fat/Adipogel group. No significant difference was seen in final construct total volume or construct neovascularisation between the groups. This study demonstrated that a pedicled adipose flap can be generated in rats by combining a blood vessel loop, an adipogenic hydrogel, and a lipoaspirate equivalent. Success appears to be based on adipogenesis rather than on adipocyte survival, and consistent with our previous work, this adipogenesis occurred subsequent to graft death and remodelling. The regenerative process was significantly enhanced in the presence of Adipogel.

Macrophage ontogeny in the control of adipose tissue biology

Macrophages are found in large numbers in the adipose tissue where they closely associate with the adipocytes and the vasculature. Adipose tissue macrophages are a heterogenous population of cells with 'hard wired' diversity brought upon by distinct developmental lineages. The purpose of this review is to provide a brief history of macrophages in control of adipose tissue metabolism with the emphasis on the importance of macrophage ontogeny.

Cytokines and inflammation in adipogenesis: an updated review

The biological relevance of cytokines is known for more than 20 years. Evidence suggests that adipogenesis is one of the biological events involved in the regulation of cytokines, and pro-inflammatory cytokines (e.g., TNFα and IL-1β) inhibit adipogenesis through various pathways. This inhibitory effect can constrain the hyperplastic expandability of adipose tissues. Meanwhile, chronic low-grade inflammation is commonly observed in obese populations. In some individuals, the impaired ability of adipose tissues to recruit new adipocytes to adipose depots during overnutrition results in adipocyte hypertrophy, ectopic lipid accumulation, and insulin resistance. Intervention studies showed that pro-inflammatory cytokine antagonists improve metabolism in patients with metabolic syndrome. This review focuses on the cytokines currently known to regulate adipogenesis under physiological and pathophysiological circumstances. Recent studies on how inhibited adipogenesis leads to metabolic disorders were summarized. Although the interplay of cytokines and lipid metabolism is yet incompletely understood, cytokines represent a class of potential therapeutic targets in the treatment of metabolic disorders.

MCP-1 Feedback Loop Between Adipocytes and Mesenchymal Stromal Cells Causes Fat Accumulation and Contributes to Hematopoietic Stem Cell Rarefaction in the Bone Marrow of Patients With Diabetes

Fat accumulates in bone marrow (BM) of patients with diabetes. In this study, we investigated the mechanisms and consequences of this phenomenon. BM mesenchymal stromal cells (BM-MSCs) from patients with type 2 diabetes (T2D) constitutively express adipogenic markers and robustly differentiate into adipocytes (ADs) upon in vitro induction as compared with BM-MSCs from subjects without diabetes. Moreover, BM-ADs from subjects with T2D (T2D BM-ADs) paracrinally stimulate a transcriptional adipogenic program in BM-MSCs. Antagonism of MCP-1, a chemokine pivotally expressed in T2D BM-ADs, prevented the T2D BM-AD secretome from converting BM-MSCs into ADs. Mechanistic validation of human data was next performed in an obese T2D mouse model. Systemic antagonism of MCP-1 improved metabolic control, reduced BM fat, and increased osteocyte density. It also indirectly re-established the abundance of long-term versus short-term hematopoietic stem cells. We reveal a diabetic feedback loop in which 1) BM-MSCs are constitutively inclined to make ADs, and 2) mature BM-ADs, via secreted MCP-1, relentlessly fuel BM-MSC determination into new fat. Pharmacological inhibition of MCP-1 signaling can contrast this vicious cycle, restoring, at least in part, the balance between adipogenesis and hematopoiesis in BM from subjects with T2D.

Nitric oxide balances osteoblast and adipocyte lineage differentiation via the JNK/MAPK signaling pathway in periodontal ligament stem cells

Background

Critical tissues that undergo regeneration in periodontal tissue are of mesenchymal origin; thus, investigating the regulatory mechanisms underlying the fate of periodontal ligament stem cells could be beneficial for application in periodontal tissue regeneration. Nitric oxide (NO) regulates many biological processes in developing embryos and adult stem cells. The present study was designed to investigate the effects of NO on the function of human periodontal ligament stem cells (PDLSCs) as well as to elucidate the underlying molecular mechanisms.

Methods

Immunofluorescent staining and flow cytometry were used for stem cell identification. Western blot, reverse transcription polymerase chain reaction (RT-PCR), immunofluorescent staining, and flow cytometry were used to examine the expression of NO-synthesizing enzymes. The proliferative capacity of PDLSCs was determined by EdU assays. The osteogenic potential of PDLSCs was tested using alkaline phosphatase (ALP) staining, Alizarin Red staining, and calcium concentration detection. Oil Red O staining was used to analyze the adipogenic ability. Western blot, RT-PCR, and staining were used to examine the signaling pathway.

Results

Human PDLSCs expressed both inducible NO synthase (iNOS) and endothelial NO synthase (eNOS) and produced NO. Blocking the generation of NO with the NOS inhibitor l-N^G-monomethyl arginine (l-NMMA) had no influence on PDLSC proliferation and apoptosis but significantly attenuated the osteogenic differentiation capacity and stimulated the adipogenic differentiation capacity of PDLSCs. Increasing the physiological level of NO with NO donor sodium nitroprusside (SNP) significantly promoted the osteogenic differentiation capacity but reduced the adipogenic differentiation capacity of PDLSCs. NO balances the osteoblast and adipocyte lineage differentiation in periodontal ligament stem cells via the c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling pathway.

Conclusions

NO is essential for maintaining the balance between osteoblasts and adipocytes in PDLSCs via the JNK/MAPK signaling pathway.

Graphical Abstract

NO balances osteoblast and adipocyte lineage differentiation via JNK/MAPK signaling pathway

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0869-2) contains supplementary material, which is available to authorized users.

Polycaprolactone nanofibrous mesh reduces foreign body reaction and induces adipose flap expansion in tissue engineering chamber

Tissue engineering chamber technique can be used to generate engineered adipose tissue, showing the potential for the reconstruction of soft tissue defects. However, the consequent foreign body reaction induced by the exogenous chamber implantation causes thick capsule formation on the surface of the adipose flap following capsule contracture, which may limit the internal tissue expansion. The nanotopographical property and architecture of nanofibrous scaffold may serve as a promising method for minimizing the foreign body reaction. Accordingly, electrospinning porous polycaprolactone (PCL) nanofibrous mesh, a biocompatible synthetic polymer, was attached to the internal surface of the chamber for the reducing local foreign body reaction. Adipose flap volume, level of inflammation, collagen quantification, capsule thickness, and adipose tissue-specific gene expression in chamber after implantation were evaluated at different time points. The in vivo study revealed that the engineered adipose flaps in the PCL group had a structure similar to that in the controls and normal adipose tissue structure but with a larger flap volume. Interleukin (IL)-1β, IL-6, and transforming growth factor-β expression decreased significantly in the PCL group compared with the control. Moreover, the control group had much more collagen deposition and thicker capsule than that observed in the PCL group. These results indicate that the unique nanotopographical effect of electrospinning PCL nanofiber can reduce foreign body reaction in a tissue engineering chamber, which maybe a promising new method for generating a larger volume of mature, vascularized, and stable adipose tissue.

Body composition and lung function in cystic fibrosis and their association with adiposity and normal-weight obesity

OBJECTIVES

This study aimed to evaluate the relationship between lung function and body composition in cystic fibrosis (CF) and examine the presence of normal-weight obesity (NWO), a high body fat percentage with a normal body mass index (BMI), in this population.

METHODS

In a pilot, cross-sectional study, 32 subjects with CF and a reference group of 20 adults without CF underwent body composition analysis with air displacement plethysmography. NWO was defined as a BMI <25 kg/m(2) and body fat >30% (for women) or >23% (for men). Lung function in subjects with CF was determined by the percentage of predicted forced expiratory volume in 1 s (FEV1% predicted).

RESULTS

Despite lower BMI and fat-free mass index (P < 0.01), fat mass index and percent body fat did not differ between subjects with CF and the reference group. Among subjects with CF, FEV1% predicted was positively associated with fat-free mass index (β = 6.31 ± 2.93, P = 0.04) and inversely associated with fat mass index (β = -6.44 ± 2.93, P = 0.04), after adjusting for age, sex, and BMI. Ten subjects with CF (31%) had NWO, which corresponded with lower fat-free mass index and FEV1% predicted compared with overweight subjects (P = 0.006 and 0.004, respectively).

CONCLUSIONS

Excess adiposity, particularly in the form of NWO, was inversely associated with lung function in CF. Larger prospective studies should be undertaken to confirm these findings and determine the long-term metabolic and clinical consequences of excess adiposity in CF. As the lifespan of individuals with CF increases, nutrition screening protocols, which primarily rely on BMI, may require reassessment.

Targeting IκB kinase β in Adipocyte Lineage Cells for Treatment of Obesity and Metabolic Dysfunctions

IκB kinase β (IKKβ), a central coordinator of inflammation through activation of nuclear factor-κB, has been identified as a potential therapeutic target for the treatment of obesity-associated metabolic dysfunctions. In this study, we evaluated an antisense oligonucleotide (ASO) inhibitor of IKKβ and found that IKKβ ASO ameliorated diet-induced metabolic dysfunctions in mice. Interestingly, IKKβ ASO also inhibited adipocyte differentiation and reduced adiposity in high-fat (HF)-fed mice, indicating an important role of IKKβ signaling in the regulation of adipocyte differentiation. Indeed, CRISPR/Cas9-mediated genomic deletion of IKKβ in 3T3-L1 preadipocytes blocked these cells differentiating into adipocytes. To further elucidate the role of adipose progenitor IKKβ signaling in diet-induced obesity, we generated mice that selectively lack IKKβ in the white adipose lineage and confirmed the essential role of IKKβ in mediating adipocyte differentiation in vivo. Deficiency of IKKβ decreased HF-elicited adipogenesis in addition to reducing inflammation and protected mice from diet-induced obesity and insulin resistance. Further, pharmacological inhibition of IKKβ also blocked human adipose stem cell differentiation. Our findings establish IKKβ as a pivotal regulator of adipogenesis and suggest that overnutrition-mediated IKKβ activation serves as an initial signal that triggers adipose progenitor cell differentiation in response to HF feeding. Inhibition of IKKβ with antisense therapy may represent as a novel therapeutic approach to combat obesity and metabolic dysfunctions. Stem Cells 2016;34:1883-1895.

Role of MCP-1 on inflammatory processes and metabolic dysfunction following high-fat feedings in the FVB/N strain

Background

MCP-1 is known to be an important chemokine for macrophage recruitment. Thus, targeting MCP-1 may prevent the perturbations associated with macrophage-induced inflammation in adipose tissue. However, inconsistencies in the available animal literature have questioned the role of this chemokine in this process. The purpose of this study was to examine the role of MCP-1 on obesity-related pathologies.

Methods

Wild-type (WT) and MCP-1 deficient mice on an FVB/N background were assigned to either low-fat-diet (LFD) or high-fat-diet (HFD) treatment for a period of 16 weeks. Body weight and body composition were measured weekly and monthly, respectively. Fasting blood glucose and insulin, and glucose tolerance were measured at 16 weeks. Macrophages, T cell markers, inflammatory mediators, and markers of fibrosis were examined in the adipose tissue at sacrifice.

Results

As expected, HFD increased adiposity (body weight, fat mass, fat percent, and adipocyte size), metabolic dysfunction (impaired glucose metabolism and insulin resistance) macrophage number (CD11b⁺F480⁺ cells, and gene expression of EMR1 and CD11c), T cell markers (gene expression of CD4 and CD8), inflammatory mediators (pNFκB and pJNK, and mRNA expression of MCP-1, CCL5, CXCL14, TNF-α, and IL-6), and fibrosis (expression of IL-10, IL-13, TGF-β, and MMP2) (P<0.05). However, contrary to our hypothesis, MCP-1 deficiency exacerbated many of these responses resulting in a further increase in adiposity (body weight, fat mass, fat percent and adipocyte size), metabolic dysregulation, macrophage markers (EMR1), inflammatory cell infiltration, and fibrosis (formation of type I and III collagens, mRNA expression of IL-10 and MMP2) (P<0.05).

Conclusions

These data suggest that MCP-1 may be a necessary component of the inflammatory response required for adipose tissue protection, remodeling, and healthy expansion in the FVB/N strain in response to HFD feedings.

The multifaceted role of nitric oxide synthases in mitochondrial biogenesis and cell differentiation

Nitric oxide (NO) is physiologically synthetized by a family of enzymes called NO synthases (NOSs). NO is a pleiotropic second messenger having a fundamental role in several cellular processes including cell differentiation. Being a high reactive molecule, NO must be synthetized in close proximity to the effector/target. For this reason, the subcellular localization of NOSs is tightly regulated by different post-translation mechanisms. Recently, in murine C2C12 myoblasts, we have demonstrated that mitochondrial biogenesis, an essential event for cell differentiation, can be effective only if the site of NO production is located at nuclear level, where NO favors the CREB-dependent expression of PGC-1α gene. The increase of NO flux in nuclei is elicited by the up-regulation and redistribution of neuronal NOS (nNOS) toward nuclei. Herein we show that an upregulation of endothelial NOS (eNOS) occurs during adipocyte differentiation in 3T3-L1 cells. However, differently to differentiating myocytes, a concomitant redistribution of eNOS toward nuclei was not detected. We also observed that, upon treatment with the NO synthesis inhibitor L-NAME, mitochondrial biogenesis as well as triglyceride accumulation that normally occurs during adipogenesis were not impeded. The absence of eNOS in nuclei together with the ineffectiveness of L-NAME suggest that, at least during 3T3-L1 differentiation, NO is not fundamental for the induction of mitochondrial biogenesis and adipogenesis.

The adipogenic potential of various extracellular matrices under the influence of an angiogenic growth factor combination in a mouse tissue engineering chamber

The extracellular matrix (ECM) Matrigel™ has frequently and successfully been used to generate new adipose tissue experimentally, but is unsuitable for human application. This study sought to compare the adipogenic potential of a number of alternative, biologically derived or synthetic ECMs with potential for human application, with and without growth factors and a small fat autograft. Eight groups, with six severe combined immunodeficient (SCID) mice per group, were created with bilateral chambers (silicone tubes) implanted around the epigastric vascular pedicle, with one chamber/animal containing a 5mg fat autograft. Two animal groups were created for each of four ECMs (Matrigel™, Myogel, Cymetra® and PuraMatrix™) which filled the bilateral chambers. One group/ECM had no growth factors added to chambers whilst the other group had growth factors (GFs) (vascular endothelial growth factor-A (VEGF-A) plus fibroblast growth factor-2 (FGF-2) plus platelet-derived growth factor-BB (PDGF-BB)) added to both chambers. At 6weeks, chamber tissue was morphometrically assessed for percent and absolute adipose tissue volume. Overall, the triple GF regime significantly increased percent(∗) and absolute(#) adipose tissue volume (p<0.0005(∗#)) compared to chambers without triple GF treatment. The fat autograft also significantly increased percent (p<0.0005) and absolute (p<0.011) adipose tissue volume. Cymetra® (human collagen) constructs yielded the largest total tissue and absolute adipose tissue volume. We found that the pro-angiogenic FGF-2, VEGF-A and PDGF-BB combination in ECMs of synthetic and biological origin produced an overall significantly increased adipose tissue volume at 6weeks and may have clinical application, particularly with Cymetra.

Tissue engineering chamber promotes adipose tissue regeneration in adipose tissue engineering models through induced aseptic inflammation

Tissue engineering chamber (TEC) makes it possible to generate significant amounts of mature, vascularized, stable, and transferable adipose tissue. However, little is known about the role of the chamber in tissue engineering. Therefore, to investigate the role of inflammatory response and the change in mechanotransduction started by TEC after implantation, we placed a unique TEC model on the surface of the groin fat pads in rats to study the expression of cytokines and tissue development in the TEC. The number of infiltrating cells was counted, and vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) expression levels in the chamber at multiple time points postimplantation were analyzed by enzyme-linked immunosorbent assay. Tissue samples were collected at various time points and labeled for specific cell populations. The result showed that new adipose tissue formed in the chamber at day 60. Also, the expression of MCP-1 and VEGF in the chamber decreased slightly from an early stage as well as the number of the infiltrating cells. A large number of CD34+/perilipin- perivascular cells could be detected at day 30. Also, the CD34+/perilipin+ adipose precursor cell numbers increased sharply by day 45 and then decreased by day 60. CD34-/perilipin+ mature adipocytes were hard to detect in the chamber content at day 30, but their number increased and then peaked at day 60. Ki67-positive cells could be found near blood vessels and their number decreased sharply over time. Masson's trichrome showed that collagen was the dominant component of the chamber content at early stage and was replaced by newly formed small adipocytes over time. Our findings suggested that the TEC implantation could promote the proliferation of adipose precursor cells derived from local adipose tissue, increase angiogenesis, and finally lead to spontaneous adipogenesis by inducing aseptic inflammation and changing local mechanotransduction.

CCL2 mediates anti-fibrotic effects in human fibroblasts independently of CCR2

CCL2 is known for its major role as a chemoattractant of monocytes for immunological surveillance and to site of inflammation. CCL2 acts mainly through the G-protein-coupled receptor CCR2 but has also been described to mediate its effects independently of this receptor in vitro and in vivo. Emerging pieces of evidence indicate that the CCL2/CCR2 axis is involved in fibrotic diseases, such as increased plasma levels of CCL2 and the presence of CCL2-hyperresponsive fibroblasts explanted from patients with systemic sclerosis and idiopathic pulmonary fibrosis. One of the profibrotic key mediators is the myofibroblast characterized by overexpression of α-smooth muscle actin and collagen I. However, the correlation between the CCL2/CCR2 axis and the activation of fibroblasts is not yet fully understood. We have screened human fibroblasts of various origins, human pulmonary fibroblasts (HPF), human fetal lung fibroblasts (HFL-1) and primary preadipocytes (SPF-1) in regard to CCL2 stimulated fibrotic responses. Surprisingly we found that CCL2 mediates anti-fibrotic effects independently of CCR2 in human fibroblasts of different origins.

Adipose-derived stem cells: methods for isolation and applications for clinical use

Adipose tissue sciences have rapidly expanded since the identification of regenerative cells contained within the stromal vascular fraction (SVF) of fat. Isolation of the SVF, containing adipose-derived stem cells (ADSC), can be accomplished efficiently in the operating room or in the laboratory through enzymatic digestion of the adipose tissue and concentration of SVF. Cells can be directly re-injected as a mesotherapeutic agent, recombined with a tissue scaffold (e.g., cell-enriched fat grafts) or expanded in culture for tissue-engineered cell therapeutics. The potential for cell therapy is under current investigation by researchers around the world. This chapter reviews laboratory methods for isolating ADSCs and the ongoing clinical trials evaluating cell therapeutic efficacy across many specialties, including cardiology, neurology, immunology, tissue engineering, sports medicine, and plastic and reconstructive surgery.

Macrophages play a key role in angiogenesis and adipogenesis in a mouse tissue engineering model

We have previously described a mouse adipose tissue engineering model using a silicon chamber enclosing the superficial epigastric pedicle in a Matrigel based environment. We have shown that when Zymosan, a sterile inflammatory agent, is added to the chamber, angiogenesis and adipogenesis are significantly improved. As Zymosan interacts with toll-like receptors on macrophages, the role of macrophages in new tissue development in the tissue engineering chamber was assessed. Morphological and histological results showed that macrophages were presenting in high numbers at 2 weeks but had decreased significantly by 4 and 6 weeks in the chamber. Numerous immature new blood vessels had formed by 2 weeks, becoming more mature at 4 and 6 weeks. Immature adipocytes were visualized at 4 weeks and mature cells, at 6 weeks. To investigate the functional role of macrophages in the tissue engineering process, we knocked out the local macrophage population by inserting Clodronate liposomes in this chamber. This study shows for the first time that when macrophages are depleted, there is minimal new vascular and adipose tissue development. We propose a new theory for tissue engineering in which macrophages play a central role in both neovascularisation and adipogenesis.

Butyrate attenuates inflammation and lipolysis generated by the interaction of adipocytes and macrophages

AIM

Paracrine interaction between macrophages and adipocytes in obese visceral fat tissues is thought to be a trigger of chronic inflammation. The immunomodulatory effect of the short chain fatty acid, butyric acid, has been demonstrated. We hypothesize that sodium butyrate (butyrate) attenuates inflammatory responses and lipolysis generated by the interaction of macrophages and adipocytes.

METHODS

Using contact or transwell co-culture methods with differentiated 3T3-L1 adipocytes and RAW264.7 macrophages, we investigated the effects of butyrate on the production of tumor necrosis factor alpha (TNF-α), monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), and the release of free glycerol, free fatty acids (FFAs) into the medium. We also examined the activity of nuclear factor-kappaB (NF-κB) and the phosphorylation of mitogen-activated protein kinases (MAPKs) in co-cultured macrophages, as well as lipase activity and expression in co-cultured adipocytes.

RESULTS

We found increased production of TNF-α, MCP-1, IL-6, and free glycerol, FFAs in the co-culture medium, and butyrate significantly reduced them. Butyrate inhibited the phosphorylation of MAPKs, the activity of NF-κB in co-cultured macrophages, and suppressed lipase activity in co-cultured adipocytes. Lipase inhibitors significantly attenuated the production of TNF-α, MCP-1 and IL-6 in the co-culture medium as effectively as butyrate. Butyrate suppressed the protein production of adipose triglyceride lipase, hormone sensitive lipase, and fatty acid-binding protein 4 in co-cultured adipocytes. Pertussis toxin, which is known to block GPR41 completely, inhibited the antilipolysis effect of butyrate.

CONCLUSION

Butyrate suppresses inflammatory responses generated by the interaction of adipocytes and macrophages through reduced lipolysis and inhibition of inflammatory signaling.

An adipoinductive role of inflammation in adipose tissue engineering: key factors in the early development of engineered soft tissues

Tissue engineering and cell implantation therapies are gaining popularity because of their potential to repair and regenerate tissues and organs. To investigate the role of inflammatory cytokines in new tissue development in engineered tissues, we have characterized the nature and timing of cell populations forming new adipose tissue in a mouse tissue engineering chamber (TEC) and characterized the gene and protein expression of cytokines in the newly developing tissues. EGFP-labeled bone marrow transplant mice and MacGreen mice were implanted with TEC for periods ranging from 0.5 days to 6 weeks. Tissues were collected at various time points and assessed for cytokine expression through ELISA and mRNA analysis or labeled for specific cell populations in the TEC. Macrophage-derived factors, such as monocyte chemotactic protein-1 (MCP-1), appear to induce adipogenesis by recruiting macrophages and bone marrow-derived precursor cells to the TEC at early time points, with a second wave of nonbone marrow-derived progenitors. Gene expression analysis suggests that TNFα, LCN-2, and Interleukin 1β are important in early stages of neo-adipogenesis. Increasing platelet-derived growth factor and vascular endothelial cell growth factor expression at early time points correlates with preadipocyte proliferation and induction of angiogenesis. This study provides new information about key elements that are involved in early development of new adipose tissue.

The nitric oxide system--cure for shortcomings in adipose tissue engineering?

Adipose tissue engineering aims to grow fat tissue for soft tissue reconstruction after tumour resection or trauma. However, insufficient progenitor cell differentiation and poor vascularization compromise the generation of clinically applicable adipose tissue. The desired process of neo-adipogenesis seems to be difficult to mimic, even though it takes place in all of us, inevitably and rapidly, as soon as we start consuming high-caloric diets. It has previously been proposed that inflammation and its key regulator, nitric oxide (NO), may play a relevant part in neo-adipogenesis. We here discuss how a controlled activation of the nitric oxide system on various levels may represent a cure for several current shortcomings in adipose tissue engineering.

A novel xenograft model with intrinsic vascularisation for growing undifferentiated pleomorphic sarcoma NOS in mice

PURPOSE

Preclinical development of antisarcoma therapy is primarily based on the subcutaneous transplantation of sarcoma xenografts. Tumour cell survival remains a hurdle of current models, which has been attributed to the hypoxic conditions following transplantation. We hypothesised that sarcoma models with an intrinsic tissue-engineered vascular supply are easily reproducible. The aim of this study was to establish a novel vascularised xenograft model.

MATERIALS AND METHODS

Primary human soft tissue sarcomas were transplanted into a silicon chamber and placed around the superficial epigastric vessels of nude mice. Sarcoma xenograft samples were assessed histomorphologically.

RESULTS

All sarcoma xenografts engrafted, leading to solid tumours. Histological, immunohistochemical staining and light/electron microscopy confirmed the xenografts as identical high-grade pleomorphic sarcomas (NOS) compared with the original patients' tumours.

CONCLUSION

This novel sarcoma xenograft model with an intrinsic vascular supply could be of high value for studying human soft tissue sarcomas and their therapy.

The Vascularised Groin Chamber: A Novel Model for Growing Primary Human Liposarcoma in Nude Mice

Background

The preclinical development of anti-sarcoma drugs has been primarily based on the subcutaneous transplantation of xenografts. Transplant survival remains an obstacle of current models which has been attributed to the period of hypoxia after transplantation. We hypothesized that primary soft tissue sarcoma models with an intrinsic tissue engineered vascular supply would be easily reproducible. The aim of this study was to establish a model of primary human soft tissue sarcoma with an intrinsic vascular supply.

Methods

Primary soft tissue sarcoma cells from resected human liposarcomas isolated and divided into tumour fragments were transplanted into a silicon chamber, placed around the superficial epigastric vessels in mice. Sarcoma xenograft samples were analysed histomorphologically (light/electron microscopy and immunohistochemistry).

Results

All primary soft tissue sarcoma transplants engrafted, leading to solid tumours within 3 weeks. Histological and immunohistochemical staining confirmed the mouse xenografts as identical high grade liposarcomas compared to original tumour tissue.

Conclusion

This study established a reproducible xenograft model of primary human liposarcoma. This animal model could be of high value for studying human soft tissue sarcomas and their therapy.

Drug delivery in soft tissue engineering

INTRODUCTION

Tissue defects, sustained through disease or trauma, present enormous challenges in regenerative medicine. Modern tissue engineering (TE) aims at replacing or repairing these defects through a combined approach of biodegradable scaffolds, suitable cell sources and appropriate environmental cues, such as biomolecules presented on scaffold surfaces or sustainably released from within.

AREAS COVERED

This review provides a brief overview of the various drugs and bioactive molecules of interest to TE, as well as a selection of materials that have been proposed for TE scaffolds and matrices in the past. It then proceeds to discuss encapsulation, immobilization and controlled release strategies for bioactive proteins, before discussing recent advances in this area with a special focus on soft TE.

EXPERT OPINION

Overall, minimal clinical success has been achieved so far in using growth factor, morphogen, or adhesion factor modified scaffolds and matrices; only one growth factor delivery system (Regranex Gel), has been approved by the FDA for clinical use, with only a handful of other growth factors being approved for human use so far. However, many more growth factors are currently in clinical Phase I - II or preclinical trials and many delivery systems utilize materials already approved by the FDA for other purposes. With respect to drug delivery in soft TE, a combination of increased research efforts in hydrogel and support material development as well as growth factor development is needed before clinical success is realized.

Adipose tissue engineering for soft tissue regeneration

Current treatment modalities for soft tissue defects caused by various pathologies and trauma include autologous grafting and commercially available fillers. However, these treatment methods present a number of challenges and limitations, such as donor-site morbidity and volume loss over time. As such, improved therapeutic modalities need to be developed. Tissue engineering techniques offer novel solutions to these problems through development of bioactive tissue constructs that can regenerate adipose tissue in both structure and function. Recently, a number of studies have been designed to explore various methods to engineer human adipose tissue. This review will focus on these developments in the area of adipose tissue engineering for soft tissue replacement. The physiology of adipose tissue and current surgical therapies used to replace lost tissue volume, specifically in breast tissue, are introduced, and current biomaterials, cell sources, and tissue culture strategies are discussed. We discuss future areas of study in adipose tissue engineering.

Nitric oxide and downstream second messenger cGMP and cAMP enhance adipogenesis in primary human preadipocytes

BACKGROUND AIMS

Obesity is correlated with chronic low-grade inflammation. Thus the induction of inflammation could be used to stimulate adipose tissue formation in tissue-engineering approaches. As nitric oxide (NO) is a key regulator of inflammation, we investigated the effect of NO and its downstream signaling molecule guanosine 3',5'-cyclic monophosphate (cGMP) as well as adenosine 3',5'-cyclic monophosphate (cAMP) on preadipocytes in vitro.

METHODS

Preadipocytes were isolated from human subcutaneous adipose tissue, cultured until confluence, and differentiated. The NO donor diethylenetriamine (DETA)/NO (30-150 microm) was added during proliferation and differentiation. Additionally, cGMP/cAMP analogs 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP), 8-(4-chlorophenylthio)-guanosine 3',5'-cyclic monophosphate (8-pCPT-cGMP) and 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP), and the adenylyl cyclase activator forskolin, specific guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and adenylyl cyclase inhibitor 2'-5'-dideoxyadenosine (ddA), were applied. Proliferation and differentiation were evaluated.

RESULTS

DETA/NO in combination with the standard differentiation procedure significantly enhanced maturation of precursor cells to adipocytes. Proliferation, in contrast, was inhibited in the presence of NO. The application of cGMP and cAMP, respectively, increased pre-adipocyte differentiation to an even higher extent than NO. Inhibitors of the underlying pathways caused a significant decrease in adipogenic conversion.

CONCLUSIONS

Our results support the application of NO donors during transplantation of preadipocytes in a 3-dimensional setting to accelerate and optimize differentiation. The results suggest that, instead of the rather instable and reactive molecule NO, the application of cGMP and cAMP would be even more effective because these substances have a stronger adipogenic effect on preadipocytes and a longer half-life than NO. Also, by applying inhibitors of the underlying pathways, the induced inflammatory condition could be regulated to the desired level.

Apoptosis and inflammation: role of adipokines in inflammatory bowel disease

OBJECTIVES

Leptin and adiponectin (APN) are adipokines produced by adipocytes that participate in the modulation of immune and inflammatory responses. In Crohn's disease (CD), fat wrapping surrounding the inflamed intestine produces high levels of leptin and APN. In inflammatory bowel disease (IBD), apoptosis resistance of lamina propria T lymphocytes (LPL-T) is one of the mechanisms that maintains chronic inflammation. We addressed the mechanism by which leptin and APN regulate inflammation and apoptosis in IBD.

METHODS

Immune cell infiltration, several factors expressed by adipose tissue (AT), and spontaneous release of cytokines by adipocytes were measured. The presence of APN and leptin in intestinal mucosa was detected and their effect on LPL-T apoptosis, signal transducer and activator of transcription 3 (STAT3), Suppressor of Cytokine Signaling 3 (SOCS3), Bcl-2 and Bcl-xL expression, and cytokine production was studied. In addition, the effects of globular and high-molecular-weight (HMW) APN on LPL-T cytokine production and apoptosis were studied.

RESULTS

Higher levels of several chemokines, cytokines, and growth factors were present in AT near active than near inactive disease. A significantly higher amount of inflammatory infiltrate was present in AT near active CD than near ulcerative colitis, controls, and near the inactive area of CD. There were no changes in the ratios of APN molecular weight in control and IBD adipocyte products. Leptin and APN inhibited anti-CD3-stimulated-LPL-T apoptosis and potentiated STAT3 phosphorylation, Bcl-2, and Bcl-xL expression in IBD and control mucosa. However, SOCS3 expression was suppressed only in IBD. Both globular and HMW APN have similar effects on LPL-T cytokine production and apoptosis. Leptin and APN enhanced interleukin (IL)-10 production by anti-CD3-stimulated LPL-T in IBD only. APN, but not leptin, increased anti-CD3-induced IL-6 levels in LPL-T only in IBD patients. IL-10 exerts its anti-inflammatory activity in the presence of SOCS3 suppression by leptin or APN.

CONCLUSION

Leptin and APN maintain the inhibition of anti-CD3-stimulated LPL-T apoptosis by enhancing Bcl-2 and Bcl-xL overexpression and promoting STAT3 phosphorylation while suppressing SOCS3.

Anti-adipogenesis by 6-thioinosine is mediated by downregulation of PPAR gamma through JNK-dependent upregulation of iNOS

Adipocyte dysfunction is associated with the development of obesity. This study shows that 6-thioinosine inhibits adipocyte differentiation. The mRNA levels of PPAR gamma and C/EBPalpha, but not C/EBPbeta and delta, were reduced by 6-thioinosine. Moreover, the mRNA levels of PPAR gamma target genes (LPL, CD36, aP2, and LXRalpha) were down-regulated by 6-thioinosine. We also demonstrated that 6-thioinosine inhibits the transactivation activity and the mRNA level of PPAR gamma. Additionally, attempts to elucidate a possible mechanism underlying the 6-thioinosine-mediated effects revealed that 6-thioinosine induced iNOS gene expression without impacting eNOS expression, and that this was mediated through activation of AP-1, especially, JNK. In addition, 6-thioinosine was found to operate upstream of MEKK-1 in JNK activation signaling. Taken together, these findings suggest that the inhibition of adipocyte differentiation by 6-thioinosine occurs primarily through the reduced expression of PPAR gamma, which is mediated by upregulation of iNOS via the activation of JNK.

Association of monocyte chemoattractant protein-1 -2518 polymorphism with metabolic syndrome in a South Indian cohort

BACKGROUND

Previous reports have indicated an association of monocyte chemoattractant protein-1 (MCP-1) with risk factors for atherosclerosis and coronary artery disease (CAD). Because some of these risk factors form components of metabolic syndrome, in the present study, we investigated the association of an important promoter region polymorphism of MCP-1, A-2518G, and its serum levels with metabolic syndrome in a South Indian cohort.

METHODS

The study comprised of 126 healthy subjects aged 30-59 years from South India. Subjects were classified on the basis of presence or absence of metabolic syndrome and metabolic syndrome components as per the International Diabetes Federation definition. MCP-1 genotyping was done by polymerase chain reaction restriction fragment-length polymorphism, and serum levels were estimated by enzyme-linked immunosorbent assay.

RESULTS

The MCP-1 -2518G allele frequency in the study population was 32.9% and the mean MCP-1 serum levels were 523 +/- 272.3 pg/mL. Subjects with metabolic syndrome showed an increased presence of the MCP-1 -2518G allele in comparison to those without metabolic syndrome (odds ratio [OR] = 5.03, P = 0.02). The association was related to a higher proportion of this allele in subjects with increased waist circumference (OR = 3.78, P = 0.05).

CONCLUSIONS

The MCP-1 -2518G allele may be contributing to atherosclerosis and CAD by conferring an increased risk to metabolic syndrome and/or obesity.

MCP-1 (monocyte chemotactic protein-1)-induced protein, a recently identified zinc finger protein, induces adipogenesis in 3T3-L1 pre-adipocytes without peroxisome proliferator-activated receptor gamma

Adipogenesis is a key differentiation process relevant to obesity and associated diseases such as type 2 diabetes. This process involves temporally regulated genes controlled by a set of transcription factors, CCAAT/enhancer-binding proteins (C/EBP) beta, C/EBPdelta, and C/EBPalpha and peroxisome proliferator-activated receptor gamma (PPARgamma). Currently, PPARgamma is universally accepted as the master regulator that is necessary and sufficient to induce adipogenesis as no known factor can induce adipogenesis without PPARgamma. We present evidence that a novel zinc finger protein, MCP-1-induced protein (MCPIP), can induce adipogenesis without PPARgamma. Classical adipogenesis-inducing medium induces MCP-1 production and expression of MCPIP in 3T3-L1 cells before the induction of the C/EBP family of transcription factors and PPARgamma. Knockdown of MCPIP prevents their expression and adipogenesis as measured by expression of adipocyte markers and lipid droplet accumulation. Treatment of 3T3-L1 cells with MCP-1 or forced expression of MCPIP induces expression of C/EBPbeta, C/EBPdelta, C/EBPalpha, and PPARgamma and adipogenesis without any other inducer. Forced expression of MCPIP induces expression of the C/EBP family of transcription factors and adipogenesis in PPARgamma(-/-) mouse embryonic fibroblasts. Thus, MCPIP is a newly identified protein that can induce adipogenesis without PPARgamma.

Maternal obesity, inflammation, and fetal skeletal muscle development

Maternal obesity coupled with Western-style high-energy diets represents a special problem that can result in poor fetal development, leading to harmful, persistent effects on offspring, including predisposition to obesity and type 2 diabetes. Mechanisms linking maternal obesity to the increased incidence of obesity and other metabolic diseases in offspring remain poorly defined. Because skeletal muscle is the principal site for glucose and fatty acid utilization and composes 40%-50% of total body mass, changes in the properties of offspring skeletal muscle and its mass resulting from maternal obesity may be responsible for the increase in type 2 diabetes and obesity. Fetal stage is crucial for skeletal muscle development because there is no net increase in the muscle fiber number after birth. Fetal skeletal muscle development involves myogenesis, adipogenesis, and fibrogenesis, which are all derived from mesenchymal stem cells (MSCs). Shifting commitment of MSCs from myogenesis to adipogenesis and fibrogenesis will result in increased intramuscular fat and connective tissue, as well as reduced numbers of muscle fiber and/or diameter, all of which have lasting negative effects on offspring muscle function and properties. Maternal obesity leads to low-grade inflammation, which changes the commitment of MSCs in fetal muscle through several possible mechanisms: 1) inflammation downregulates wingless and int (WNT) signaling, which attenuates myogenesis; 2) inflammation inhibits AMP-activated protein kinase, which promotes adipogenesis; and 3) inflammation may induce epigenetic modification through polycomb group proteins. More studies are needed to further explore the underlying mechanisms associated with maternal obesity, inflammation, and the commitment of MSCs.