Expression analysis of human adipose-derived stem cells during in vitro differentiation to an adipocyte lineage

Identification and verification of AK4 as a protective immune-related biomarker in adipose-derived stem cells and breast cancer

Background

Breast cancer (BC) remains the most common cancer among women, and novel post-surgical reconstruction techniques, including autologous fat transplantation, have emerged. While Adipose-derived stem cells (ADSCs) are known to impact the viability of fat grafts, their influence on breast cancer progression remains unclear. This study aims to elucidate the genetic interplay between ADSCs and breast cancer, focusing on potential therapeutic targets.

Methods

Using the GEO and TCGA databases, we pinpointed differentially expressed (DE) mRNAs, miRNAs, lncRNAs, and pseudogenes of ADSCs and BC. We performed functional enrichment analysis and constructed protein-protein interaction (PPI), RNA binding protein (RBP)-pseudogene-mRNA, and lncRNA-miRNA-transcription factor (TF)-gene networks. Our study delved into the correlation of AK4 expression with 33 different malignancies and examined its impact on prognostic outcomes across a pan-cancer cohort. Additionally, we scrutinized immune infiltration, microsatellite instability, and tumor mutational burden, and conducted single-cell analysis to further understand the implications of AK4 expression. We identified novel sample subtypes based on hub genes using the ConsensusClusterPlus package and examined their association with immune infiltration. The random forest algorithm was used to screen DE mRNAs between subtypes to validate the powerful prognostic prediction ability of the artificial neural network.

Results

Our analysis identified 395 DE mRNAs, 3 DE miRNAs, 84 DE lncRNAs, and 26 DE pseudogenes associated with ADSCs and BC. Of these, 173 mRNAs were commonly regulated in both ADSCs and breast cancer, and 222 exhibited differential regulation. The PPI, RBP-pseudogene-mRNA, and lncRNA-miRNA-TF-gene networks suggested AK4 as a key regulator. Our findings support AK4 as a promising immune-related therapeutic target for a wide range of malignancies. We identified 14 characteristic genes based on the AK4-related cluster using the random forest algorithm. Our artificial neural network yielded excellent diagnostic performance in the testing cohort with AUC values of 0.994, 0.973, and 0.995, indicating its ability to distinguish between breast cancer and non-breast cancer cases.

Conclusions

Our research sheds light on the dual role of ADSCs in BC at the genetic level and identifies AK4 as a key protective mRNA in breast cancer. We found that AK4 significantly predicts cancer prognosis and immunotherapy, indicating its potential as a therapeutic target.

CCNB1 may as a biomarker for the adipogenic differentiation of adipose-derived stem cells in the postoperative fat transplantation of breast cancer

Background

Adipose-derived stem cells (ADSCs) are closely associated with the survival rate of transplanted fat in breast reconstruction after breast cancer surgery. Nevertheless, the intrinsic mechanisms regulating ADSCs adipogenic differentiation remain ambiguous. The aim of our study was to explore the relevant genes and pathways to elucidate the potential mechanisms of adipogenic differentiation in ADSCs.

Methods

The Gene Expression Omnibus (GEO) dataset GSE61302 was downloaded and analyzed to identify differentially expressed genes (DEGs). Key genes and signaling pathways were obtained through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional and enrichment analysis. Protein-protein interaction (PPI) network and hub gene analyses were performed with the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database and Cytoscape software. Finally, the transcription levels of hub genes in the adipogenic differentiated group and undifferentiated group of ADSCs were compared via real-time quantitative polymerase chain reaction (RT-qPCR).

Results

In total, 1,091 DEGs were identified through bioinformatics analysis of the adipogenic differentiated group and undifferentiated group. If was then found that the 10 downregulated key genes, CCNB1, NUSAP1, DLGAP5, TTK, CCNB2, KIF23, BUB1B, CDC20, CDCA8, and KIF11 may play important roles in the adipogenic differentiation of ADSCs. Subsequent in vitro experimental verification also revealed that the messenger RNA (mRNA) expression levels of cyclin B1 in adipogenic differentiated cells and undifferentiated cells were significantly different at the early stage (P<0.05), but there was no significant difference at the late stage (P>0.05).

Conclusions

As a key gene, CCNB1 might be a potential biomarker in the adipogenic differentiation of ADSCs at the early stage.

Transcriptomic Analysis Reveals Fibroblast Growth Factor 11 (FGF11) Role in Brown Adipocytes in Thermogenic Regulation of Goats

Brown adipose tissue (BAT) is the main site of adaptive thermogenesis, generates heat to maintain body temperature upon cold exposure, and protects against obesity by promoting energy expenditure. RNA-seq analysis revealed that FGF11 is enriched in BAT. However, the functions and regulatory mechanisms of FGF11 in BAT thermogenesis are still limited. In this study, we found that FGF11 was significantly enriched in goat BAT compared with white adipose tissue (WAT). Gain- and loss-of-function experiments revealed that FGF11 promoted differentiation and thermogenesis in brown adipocytes. However, FGF11 had no effect on white adipocyte differentiation. Furthermore, FGF11 promoted the expression of the UCP1 protein and an EBF2 element was responsible for UCP1 promoter activity. Additionally, FGF11 induced UCP1 gene expression through promoting EBF2 binding to the UCP1 promoter. These results revealed that FGF11 promotes differentiation and thermogenesis in brown adipocytes but not in white adipocytes of goats. These findings provide evidence for FGF11 and transcription factor regulatory functions in controlling brown adipose thermogenesis of goats.

Integrative Analysis of the Predictive Value of Perilipin Family on Clinical Significance, Prognosis and Immunotherapy of Glioma

Gliomas are common tumors of the central nervous system. The PLINs family is widely involved in the regulation of lipid metabolism and has been associated with the development and invasive metastasis of various malignancies. However, the biological role of the PLINs family in gliomas is still unclear. TIMER and UALCAN were used to assess PLINs mRNA expression in gliomas. “Survminer” and “Survival” were used to evaluate the connection between PLINs expression and glioma patients’ survival. cBioPortal was applied to assess PLINs’ genetic alterations in glioblastoma multiforme (GBM) and low-grade glioma (LGG). The correlation of PLINs expression with tumor immune cells was analyzed by TIMER. The expressions of PLIN1, PLIN4, and PLIN5 were decreased in GBM compared to normal tissues. However, PLIN2 and PLIN3 were significantly increased in GBM. Prognostic analysis showed that LGG patients with high PLIN1 expression had better overall survival (OS), and high expression of PLIN2/3/4/5 was associated with unfavorable OS. We further determined that the expression of PLINs members in gliomas was strongly related to tumor immune cells and immune checkpoint-associated genes. PLINS may be potential biomarkers for regulating the tumor microenvironment and predicting the efficacy of immunotherapy. In addition, we determined that PLIN1 may affect glioma patients’ therapeutic sensitivity to temozolomide. Our results demonstrated the biological significance and clinical values of PLINs in gliomas and provide a basis for future in-depth exploration of the specific mechanisms of each member of PLINs in gliomas.

Preparation and Quality Evaluation of Cultured Fat

Cultured meat is rapidly developing as an emerging meat production technology. Adipose tissue plays an essential role in the flavor of meat products. In this study, cultured fat was produced by cultured adipose-derived stem cells (ADSCs) based on collagen in vitro, with a 3D model. The research showed that ADSCs could attach to collagen hydrogels and differentiate into mature adipocytes. Texture analysis demonstrated that the springiness, cohesiveness, and resilience of cultured fat were consistent with porcine subcutaneous fat. Moreover, 28 volatile organic compounds (VOCs) were detected by headspace gas chromatography-ion mobility spectrometry. The relative contents of 17 VOCs in cultured fat were significantly higher than porcine subcutaneous fat and empty collagen hydrogels, and the relative contents of 5 VOCs in cultured fat were not significantly different from porcine subcutaneous fat. These findings assert the promising application of cultured fat in cultured meat production.

The immune checkpoint B7-H3 (CD276) regulates adipocyte progenitor metabolism and obesity development

The immune checkpoint B7-H3 (CD276) is a member of the B7 family that has been studied in the tumor microenvironment and immunotherapy, but its potential role in metabolism remains largely unknown. Here, we show that B7-H3 is highly expressed in mouse and human adipose tissue at steady state, with the highest levels in adipocyte progenitor cells. B7-H3 is rapidly down-regulated upon the initiation of adipocyte differentiation. Combined RNA sequencing and metabolic studies reveal that B7-H3 stimulates glycolytic and mitochondrial activity of adipocyte progenitors. Loss of B7-H3 in progenitors results in impaired oxidative metabolism program and increased lipid accumulation in derived adipocytes. Consistent with these observations, mice knocked out for B7-H3 develop spontaneous obesity, metabolic dysfunction, and adipose tissue inflammation. Our results reveal an unexpected metabolic role for B7-H3 in adipose tissue and open potential new avenues for the treatment of metabolic diseases by targeting the B7-H3 pathway.

In Vitro Cultures of Adipose-Derived Stem Cells: An Overview of Methods, Molecular Analyses, and Clinical Applications

Adipose-derived stem cells (ASCs) exhibiting mesenchymal stem cell (MSC) characteristics, have been extensively studied in recent years. Because they have been shown to differentiate into lineages such as osteogenic, chondrogenic, neurogenic or myogenic, the focus of most of the current research concerns either their potential to replace bone marrow as a readily available and abundant source of MSCs, or to employ them in regenerative and reconstructive medicine. There is close to consensus regarding the methodology used for ASC isolation and culture, whereas a number of molecular analyses implicates them in potential therapies of a number of pathologies. When it comes to clinical application, there is a range of examples of animal trials and clinical studies employing ASCs, further emphasizing the advancement of studies leading to their more widespread use. Nevertheless, in vitro studies will most likely continue to play a significant role in ASC studies, both providing the molecular knowledge of their ex vivo properties and possibly serving as an important step in purification and application of those cells in a clinical setting. Therefore, it is important to consider current methods of ASC isolation, culture, and processing. Furthermore, molecular analyses and cell surface properties of ASCs are essential for animal studies, clinical studies, and therapeutic applications of the MSC properties.

Adipose Tissue-Derived Stem Cells Retain Their Adipocyte Differentiation Potential in Three-Dimensional Hydrogels and Bioreactors †

Osteoarthritis (OA) is a common joint disorder with a significant economic and healthcare impact. The knee joint is composed of cartilage and the adjoining bone, a synovial capsule, the infrapatellar fat pad (IPFP), and other connective tissues such as tendons and ligaments. Adipose tissue has recently been highlighted as a major contributor to OA through strong inflammation mediating effects. In this study, methacrylated gelatin (GelMA) constructs seeded with adipose tissue-derived mesenchymal stem cells (ASCs) and cultured in a 3D printed bioreactor were investigated for use in microphysiological systems to model adipose tissue in the knee joint. Four patient-derived ASC populations were seeded at a density of 20 million cells/mL in GelMA. Live/Dead and boron-dipyrromethene/4′,6-diamidino-2-phenylindole (BODIPY/DAPI) staining of cells within the constructs demonstrated robust cell viability after 28 days in a growth (control) medium, and robust cell viability and lipid accumulation in adipogenic differentiation medium. qPCR gene expression analysis and protein analysis demonstrated an upregulated expression of key adipogenesis-associated genes. Overall, these data indicate that ASCs retain their adipogenic potential when seeded within GelMA hydrogels and cultured within perfusion bioreactors, and thus can be used in a 3D organ-on-a-chip system to study the role of the IPFP in the pathobiology of the knee OA.

Comparative proteomic analysis of different stages of breast cancer tissues using ultra high performance liquid chromatography tandem mass spectrometer

BACKGROUND

Breast cancer is the fifth most prevalent cause of death among women worldwide. It is also one of the most common types of cancer among Malaysian women. This study aimed to characterize and differentiate the proteomics profiles of different stages of breast cancer and its matched adjacent normal tissues in Malaysian breast cancer patients. Also, this study aimed to construct a pertinent protein pathway involved in each stage of cancer.

METHODS

In total, 80 samples of tumor and matched adjacent normal tissues were collected from breast cancer patients at Seberang Jaya Hospital (SJH) and Kepala Batas Hospital (KBH), both in Penang, Malaysia. The protein expression profiles of breast cancer and normal tissues were mapped by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The Gel-Eluted Liquid Fractionation Entrapment Electrophoresis (GELFREE) Technology System was used for the separation and fractionation of extracted proteins, which also were analyzed to maximize protein detection. The protein fractions were then analyzed by tandem mass spectrometry (LC-MS/MS) analysis using LC/MS LTQ-Orbitrap Fusion and Elite. This study identified the proteins contained within the tissue samples using de novo sequencing and database matching via PEAKS software. We performed two different pathway analyses, DAVID and STRING, in the sets of proteins from stage 2 and stage 3 breast cancer samples. The lists of molecules were generated by the REACTOME-FI plugin, part of the CYTOSCAPE tool, and linker nodes were added in order to generate a connected network. Then, pathway enrichment was obtained, and a graphical model was created to depict the participation of the input proteins as well as the linker nodes.

RESULTS

This study identified 12 proteins that were detected in stage 2 tumor tissues, and 17 proteins that were detected in stage 3 tumor tissues, related to their normal counterparts. It also identified some proteins that were present in stage 2 but not stage 3 and vice versa. Based on these results, this study clarified unique proteins pathways involved in carcinogenesis within stage 2 and stage 3 breast cancers.

CONCLUSIONS

This study provided some useful insights about the proteins associated with breast cancer carcinogenesis and could establish an important foundation for future cancer-related discoveries using differential proteomics profiling. Beyond protein identification, this study considered the interaction, function, network, signaling pathway, and protein pathway involved in each profile. These results suggest that knowledge of protein expression, especially in stage 2 and stage 3 breast cancer, can provide important clues that may enable the discovery of novel biomarkers in carcinogenesis.

Human Adipose-Derived Hydrogel Characterization Based on In Vitro ASC Biocompatibility and Differentiation

Hydrogels serve as three-dimensional scaffolds whose composition can be customized to allow attachment and proliferation of several different cell types. Extracellular matrix-derived hydrogels are considered close replicates of the tissue microenvironment. They can serve as scaffolds for in vitro tissue engineering and are a useful tool to study cell-scaffold interaction. The aim of the present study was to analyze the effect of adipose-derived stromal/stem cells (ASCs) and decellularized adipose tissue-derived (DAT) hydrogel interaction on ASC morphology, proliferation, differentiation, and DAT hydrogel microstructure. First, the ASCs were characterized using flow cytometry, adipogenic/osteogenic differentiation, colony-forming unit fibroblast assay and doubling time. The viability and proliferation assays showed that ASCs seeded in DAT hydrogel at different concentrations and cultured for 21 days remained viable and displayed proliferation. ASCs were seeded on DAT hydrogel and cultured in stromal, adipogenic, or osteogenic media for 14 or 28 days. The analysis of adipogenic differentiation demonstrated the upregulation of adipogenic marker genes and accumulation of oil droplets in the cells. Osteogenic differentiation demonstrated the upregulation of osteogenic marker genes and mineral deposition in the DAT hydrogel. The analysis of DAT hydrogel fiber metrics revealed that ASC seeding, and differentiation altered both the diameter and arrangement of fibers in the matrix. Matrix metalloproteinase-2 (MMP-2) activity was assessed to determine the possible mechanism for DAT hydrogel remodeling. MMP-2 activity was observed in all ASC seeded samples, with the osteogenic samples displaying the highest MMP-2 activity. These findings indicate that DAT hydrogel is a cytocompatible scaffold that supports the adipogenic and osteogenic differentiation of ASCs. Furthermore, the attachment of ASCs and differentiation along adipogenic and osteogenic lineages remodels the microstructure of DAT hydrogel.

Heterogeneity in Adipose Stem Cells

Adipose stem cells (ASCs) are the basis of procedures intended for tissue regeneration. These cells are heterogeneous, owing to various factors, including the donor age, sex, body mass index, and clinical condition; the isolation procedure (liposuction or fat excision); the place from where the cells were sampled (body site and depth of each adipose depot); culture surface; type of medium (whether supplemented with fetal bovine serum or xeno-free), that affect the principal phenotypic features of ASCs. The features related to ASCs heterogeneity are relevant for the success of therapeutic procedures; these features include proliferation capacity, differentiation potential, immunophenotype, and the secretome. These are important characteristics for the success of regenerative tissue engineering, not only because of their effects upon the reconstruction and healing exerted by ASCs themselves, but also because of the paracrine signaling of ASCs and its impact on recipient tissues. Knowledge of sources of heterogeneity will be helpful in the standardization of ASCs-based procedures. New avenues of research could include evaluation of the effects of the use of more homo1geneous ASCs for specific purposes, the study of ASCs-recipient interactions in heterologous cell transplantation, and the characterization of epigenetic changes in ASCs, as well as investigations of the effect of the metabolome upon ASCs behavior in culture.

Injectable Allograft Adipose Matrix Supports Adipogenic Tissue Remodeling in the Nude Mouse and Human. Plast Reconstr Surg. 2019;143:299e-309e. [PMID: 30688888 PMCID: PMC6358185 DOI: 10.1097/prs.0000000000005269]

Supplemental Digital Content is available in the text.

Background:

Adipose tissue reaches cellular stasis after puberty, leaving adipocytes unable to significantly expand or renew under normal physiologic conditions. This is problematic in progressive lipodystrophies, in instances of scarring, and in soft-tissue damage resulting from lumpectomy and traumatic deformities, because adipose tissue will not self-renew once damaged. This yields significant clinical necessity for an off-the-shelf de novo soft-tissue replacement mechanism.

Methods:

A process comprising separate steps of removing lipid and cellular materials from adipose tissue has been developed, creating an ambient temperature-stable allograft adipose matrix. Growth factors and matrix proteins relevant to angiogenesis and adipogenesis were identified by enzyme-linked immunosorbent assay and immunohistochemistry, and subcutaneous soft-tissue integration of the allograft adipose matrix was investigated in vivo in both the athymic mouse and the dorsum of the human wrist.

Results:

Allograft adipose matrix maintained structural components and endogenous growth factors. In vitro, adipose-derived stem cells cultured on allograft adipose matrix underwent adipogenesis in the absence of media-based cues. In vivo, animal modeling showed vasculature formation followed by perilipin A–positive tissue segments. Allograft adipose matrix maintained soft-tissue volume in the dorsal wrist in a 4-month investigation with no severe adverse events, becoming palpably consistent with subcutaneous adipose.

Conclusions:

Subcutaneous implantation of allograft adipose matrix laden with retained angiogenic and adipogenic factors served as an inductive scaffold for sustaining adipogenesis. Tissue incorporation assessed histologically from both the subcutaneous injection site of the athymic nude mouse over 6 months and human dorsal wrist presented adipocyte morphology residing within the injected scaffold.

An lncRNA‑miRNA‑mRNA ceRNA network for adipocyte differentiation from human adipose‑derived stem cells

Human adipose tissue‑derived stromal stem cells (HASCs) represent a promising regenerative resource for breast reconstruction and augmentation. However, the mechanisms involved in inducing its adipogenic differentiation remain to be fully elucidated. The present study aimed to comprehensively investigate the expression changes in mRNAs, microRNAs (miRNAs) and long non‑coding (lnc)RNAs during the adipogenic differentiation of HASCs, and screen crucial lncRNA‑miRNA‑mRNA interaction axes using microarray datasets GSE57593, GSE25715 and GSE61302 collected from the Gene Expression Omnibus database. Following pretreatment, differentially expressed genes (DEGs), miRNAs (DE‑miRNAs) or lncRNAs (DE‑lncRNAs) between undifferentiated and differentiated HASCs were identified using the Linear Models for Microarray data method. A protein‑protein interaction (PPI) network was constructed for the DEGs based on protein databases, followed by module analysis. The 'lncRNA‑miRNA‑mRNA' competing endogenous RNA (ceRNA) network was constructed based on the interactions between miRNAs and mRNAs, lncRNAs and miRNAs predicted by the miRWalk and lnCeDB databases. The underlying functions of mRNAs were predicted using the clusterProfiler package. In the present study, 905 DEGs, 36 DE‑miRNAs and 577 DE‑lncRNAs were screened between undifferentiated HASCs and differentiated adipocyte cells. PPI network analysis demonstrated that LEP may be a hub gene, which was also enriched in significant module 5. LEP was predicted to be involved in the Janus kinase‑signal transducer and activator of transcription signaling pathway, and the regulation of inflammatory response. The upregulation of LEP was regulated by downregulated hsa‑miRNA (miR)‑130b‑5p and hsa‑miR‑23a‑5p (or hsa‑miR‑302d‑3p). These miRNAs also respectively interacted with RP11‑552F3.9 (or RP11‑15A1.7), ultimately forming the ceRNA axes. In conclusion, the present study revealed that the RP11‑552F3.9 (RP11‑15A1.7)‑hsa‑miR‑130b‑5p/hsa‑miR‑23a‑5p (hsa‑miR‑302d‑3p)‑LEP interaction axes may be crucial for inducing the adipogenic differentiation of HASCs via involvement in inflammation.

FGF11 influences 3T3-L1 preadipocyte differentiation by modulating the expression of PPARγ regulators

Fibroblast growth factor 11 (FGF11) is a member of the intracellular fibroblast growth factor superfamily. Here, we identified FGF11 as a novel mediator of adipogenesis. During 3T3‐L1 adipocyte differentiation, the expression of FGF11 decreased at the mitotic clonal expansion stage and increased at the terminal differentiation stage. FGF11 knockdown reduced the expression of peroxisome proliferator‐activated receptor gamma (PPARγ), a master regulator of adipogenesis, resulting in the inhibition of adipocyte differentiation. Treatment with the PPARγ agonist rosiglitazone restored the inhibition of adipogenesis caused by FGF11 knockdown. We also report that the expression of the PPARγ regulators CCAAT/enhancer‐binding protein α, sterol regulatory element‐binding protein 1, KLF9, KLF2, GATA binding factor 2, and GATA binding factor 3 was influenced by FGF11. These results suggest that FGF11 indirectly controls the expression of PPARγ through modifying the expression of multiple PPARγ regulators, thereby mediating adipogenesis.

The antiviral protein viperin regulates chondrogenic differentiation via CXCL10 protein secretion

Viperin (also known as radical SAM domain–containing 2 (RSAD2)) is an interferon-inducible and evolutionary conserved protein that participates in the cell's innate immune response against a number of viruses. Viperin mRNA is a substrate for endoribonucleolytic cleavage by RNase mitochondrial RNA processing (MRP) and mutations in the RNase MRP small nucleolar RNA (snoRNA) subunit of the RNase MRP complex cause cartilage-hair hypoplasia (CHH), a human developmental condition characterized by metaphyseal chondrodysplasia and severe dwarfism. It is unknown how CHH-pathogenic mutations in RNase MRP snoRNA interfere with skeletal development, and aberrant processing of RNase MRP substrate RNAs is thought to be involved. We hypothesized that viperin plays a role in chondrogenic differentiation. Using immunohistochemistry, real-time quantitative PCR, immunoblotting, ELISA, siRNA-mediated gene silencing, plasmid-mediated gene overexpression, label-free MS proteomics, and promoter reporter bioluminescence assays, we discovered here that viperin is expressed in differentiating chondrocytic cells and regulates their protein secretion and the outcome of chondrogenic differentiation by influencing transforming growth factor β (TGF-β)/SMAD family 2/3 (SMAD2/3) activity via C-X-C motif chemokine ligand 10 (CXCL10). Of note, we observed disturbances in this viperin–CXCL10–TGF-β/SMAD2/3 axis in CHH chondrocytic cells. Our results indicate that the antiviral protein viperin controls chondrogenic differentiation by influencing secretion of soluble proteins and identify a molecular route that may explain impaired chondrogenic differentiation of cells from individuals with CHH.

Cooperative and Independent Functions of the miR-23a~27a~24-2 Cluster in Bovine Adipocyte Adipogenesis

The miR-23a~27a~24-2 cluster is an important regulator in cell metabolism. However, the cooperative and independent functions of this cluster in bovine adipocyte adipogenesis have not been elucidated. In this study, we found that expression of the miR-23a~27a~24-2 cluster was induced during adipogenesis and this cluster acted as a negative regulator of adipogenesis. miR-27a and miR-24-2 were shown to inhibit adipogenesis by directly targeting glycerol-3-phosphate acyltransferase, mitochondrial (GPAM) and diacylglycerol O-acyltransferase 2 (DGAT2), both of which promoted adipogenesis. Meanwhile, miR-23a and miR-24-2 were shown to target decorin (DCN), glucose-6-phosphate dehydrogenase (G6PD), and lipoprotein lipase (LPL), all of which repressed adipogenesis in this study. Thus, the miR-23a~27a~24-2 cluster exhibits a non-canonical regulatory role in bovine adipocyte adipogenesis. To determine how the miR-23a~27a~24-2 cluster inhibits adipogenesis while targeting anti-adipogenic genes, we identified another target gene, fibroblast growth factor 11 (FGF11), a positive regulator of adipogenesis, that was commonly targeted by the entire miR-23a~27a~24-2 cluster. Our findings suggest that the miR-23a~27a~24-2 cluster fine-tunes the regulation of adipogenesis by targeting two types of genes with pro- or anti-adipogenic effects. This balanced regulatory role of miR-23a~27a~24-2 cluster finally repressed adipogenesis.

Adipocyte biology: It is time to upgrade to a new model

Globally, the obesity pandemic is profoundly affecting quality of life and economic productivity, but efforts to address this, especially on a pharmacological level, have generally proven unsuccessful to date, serving as a stark demonstration that our understanding of adipocyte biology and pathophysiology is incomplete. To deliver better insight into adipocyte function and obesity, we need improved adipocyte models with a high degree of fidelity in representing the in vivo state and with a diverse range of experimental applications. Adipocyte cell lines, especially 3T3-L1 cells, have been used extensively over many years, but these are limited in terms of relevance and versatility. In this review, I propose that primary adipose-derived stromal/stem cells (ASCs) present a superior model with which to study adipocyte biology ex vivo. In particular, ASCs afford us the opportunity to study adipocytes from different, functionally distinct, adipose depots and to investigate, by means of in vivo/ex vivo studies, the effects of many different physiological and pathophysiological factors, such as age, body weight, hormonal status, diet and nutraceuticals, as well as disease and pharmacological treatments, on the biology of adipocytes and their precursors. This study will give an overview of the characteristics of ASCs and published studies utilizing ASCs, to highlight the areas where our knowledge is lacking. More comprehensive studies in primary ASCs will contribute to an improved understanding of adipose tissue, in healthy and dysfunctional states, which will enhance our efforts to more successfully manage and treat obesity.

Isolation, Expansion, and Adipogenic Induction of CD34+CD31+ Endothelial Cells from Human Omental and Subcutaneous Adipose Tissue

Obesity is accompanied by an extensive remodeling of adipose tissue primarily via adipocyte hypertrophy. Extreme adipocyte growth results in a poor response to insulin, local hypoxia, and inflammation. By stimulating the differentiation of functional white adipocytes from progenitors, radical hypertrophy of the adipocyte population can be prevented and, consequently, the metabolic health of adipose tissue can be improved along with a reduction of inflammation. Also, by stimulating a differentiation of beige/brown adipocytes, the total body energy expenditure can be increased, resulting in weight loss. This approach could prevent the development of obesity co-morbidities such as type 2 diabetes and cardiovascular disease. This paper describes the isolation, expansion, and differentiation of white and beige adipocytes from a subset of human adipose tissue endothelial cells that co-express the CD31 and CD34 markers. The method is relatively cheap and is not labor-intensive. It requires access to human adipose tissue and the subcutaneous depot is suitable for sampling. For this protocol, fresh adipose tissue samples from morbidly obese subjects [body mass index (BMI) >35] are collected during bariatric surgery procedures. Using a sequential immunoseparation from the stromal vascular fraction, enough cells are produced from as little as 2-3 g of fat. These cells can be expanded in culture over 10-14 days, can be cryopreserved, and retain their adipogenic properties with passaging up to passage 5-6. The cells are treated for 14 days with an adipogenic cocktail using a combination of human insulin and the PPARγ agonist-rosiglitazone. This methodology can be used for obtaining proof of concept experiments on molecular mechanisms that drive adipogenic responses in adipose endothelial cells, or for screening new drugs that can enhance the adipogenic response directed either towards white or beige/brown adipocyte differentiation. Using small subcutaneous biopsies, this methodology can be used to screen out non-responder subjects for clinical trials aimed to stimulate beige/brown and white adipocytes for the treatment of obesity and co-morbidities.

Adipose-Derived Mesenchymal Stem Cells in the Use of Cartilage Tissue Engineering: The Need for a Rapid Isolation Procedure

Mesenchymal stem cells (MSCs) have shown much promise with respect to their use in cartilage tissue engineering. MSCs can be obtained from many different tissue sources. Among these, adipose tissue can provide an abundant source of adipose-derived mesenchymal stem cells (ADMSCs). The infrapatellar fat pad (IFP) is a promising source of ADMSCs with respect to producing a cartilage lineage. Cell isolation protocols to date are time-consuming and follow conservative approaches that rely on a long incubation period of 24–48 hours. The different types of ADMSC isolation techniques used for cartilage repair will be reviewed and compared with the view of developing a rapid one-step isolation protocol that can be applied in the context of a surgical procedure.

Expression analysis of candidate genes for fatty acid composition in adipose tissue and identification of regulatory regions

The aim of this work was to study the genetic basis of the backfat expression of lipid-related genes associated with meat quality traits in pigs. We performed a genome-wide association study with the backfat gene expression measured in 44 genes by qPCR and the PorcineSNP60 BeadChip genotypes in 115 Iberian x Landrace backcross animals. A total of 193 expression-associated SNPs located in 19 chromosomal regions were associated with expression levels of ACSM5, ELOVL6, FABP4, FADS2, and SLC27A4 genes. Three expression quantitative trail loci (eQTLs) corresponding to ACSM5, FABP4, and FADS2 were classified as cis-acting eQTLs, whereas the remaining 16 eQTLs have trans-regulatory effects. Remarkably, a SNP in the ACSM5 promoter region and a SNP in the 3′UTR region of FABP4 were the most associated polymorphisms with the ACSM5 and FABP4 expression levels, respectively. Moreover, relevant lipid-related genes mapped in the trans-eQTLs regions associated with the ACSM5, FABP4, FADS2, and SLC27A4 genes. Interestingly, a trans-eQTL hotspot on SSC13 regulating the gene expression of ELOVL6, ELOLV5, and SCD, three important genes implicated in the elongation and desaturation of fatty acids, was identified. These findings provide new data to further understand the functional regulatory mechanisms implicated in the variation of fatty acid composition in pigs.

Human adipose-derived stem cells support the growth of limbal stem/progenitor cells

The most efficient method to expand limbal stem cells (LSCs) in vitro for clinical transplantation is to culture single LSCs directly on growth-arrested mouse fibroblast 3T3 cells. To reduce possible xenobiotic contamination from 3T3s, primary human adipose-derived stem cells (ASCs) were examined as feeder cells to support the expansion of LSCs in vitro. To optimize the ASC-supported culture, freshly isolated limbal epithelial cells in the form of single cells (SC-ASC) or cell clusters (CC-ASC) were cultured using three different methods: LSCs seeded directly on feeder cells, a 3-dimensional (3D) culture system and a 3D culture system with fibrin (fibrin 3D). The expanded LSCs were examined at the end of a 2-week culture. The standard 3T3 culture served as control. Expansion of SC-ASC showed limited proliferation and exhibited differentiated morphology. CC-ASC generated epithelial cells with undifferentiated morphology in all culture methods, among which CC-ASC in 3D culture supported the highest cell doubling (cells doubled 9.0 times compared to cells doubled 4.9 times in control) while maintained the percentage of putative limbal stem/progenitor cells compared to the control. There were few cell-cell contacts between cultured LSCs and ASCs in 3D CC-ASC. In conclusion, ASCs support the growth of LSCs in the form of cell clusters but not in single cells. 3D CC-ASC could serve as a substitute for the standard 3T3 culture to expand LSCs.

A data analysis framework for biomedical big data: Application on mesoderm differentiation of human pluripotent stem cells

The development of high-throughput biomolecular technologies has resulted in generation of vast omics data at an unprecedented rate. This is transforming biomedical research into a big data discipline, where the main challenges relate to the analysis and interpretation of data into new biological knowledge. The aim of this study was to develop a framework for biomedical big data analytics, and apply it for analyzing transcriptomics time series data from early differentiation of human pluripotent stem cells towards the mesoderm and cardiac lineages. To this end, transcriptome profiling by microarray was performed on differentiating human pluripotent stem cells sampled at eleven consecutive days. The gene expression data was analyzed using the five-stage analysis framework proposed in this study, including data preparation, exploratory data analysis, confirmatory analysis, biological knowledge discovery, and visualization of the results. Clustering analysis revealed several distinct expression profiles during differentiation. Genes with an early transient response were strongly related to embryonic- and mesendoderm development, for example CER1 and NODAL. Pluripotency genes, such as NANOG and SOX2, exhibited substantial downregulation shortly after onset of differentiation. Rapid induction of genes related to metal ion response, cardiac tissue development, and muscle contraction were observed around day five and six. Several transcription factors were identified as potential regulators of these processes, e.g. POU1F1, TCF4 and TBP for muscle contraction genes. Pathway analysis revealed temporal activity of several signaling pathways, for example the inhibition of WNT signaling on day 2 and its reactivation on day 4. This study provides a comprehensive characterization of biological events and key regulators of the early differentiation of human pluripotent stem cells towards the mesoderm and cardiac lineages. The proposed analysis framework can be used to structure data analysis in future research, both in stem cell differentiation, and more generally, in biomedical big data analytics.

FGF11 induced by hypoxia interacts with HIF-1α and enhances its stability

Fibroblast growth factor 11 (FGF11) is an intracellular FGF. Although induction of FGF11 by hypoxia has been observed in several cell types, the molecular function of FGF11 is not clearly understood yet. Here, we investigated the role of FGF11 under hypoxia. We identified hypoxia-inducible factor-1α (HIF-1α) as an interacting protein of FGF11 using immunoprecipitation and mass spectrometry. FGF11 knockdown decreased HIF-1α protein, while FGF11 overexpression increased it, without affecting HIF-1α mRNA. Protein stability test and ubiquitination assay showed that FGF11 increased HIF-1α stability by acting upstream of proteasomal degradation. Altogether, these results suggest a cross-regulation between HIF-1α and FGF11, through which hypoxia-induced FGF11 reinforces hypoxia responses by enhancing the stability of HIF-1α.

The Role of Reactive Oxygen Species in Adipogenic Differentiation

Interest in reactive oxygen species and adipocyte differentiation/adipose tissue function is steadily increasing. This is due in part to a search for alternative avenues for combating obesity, which results from the excess accumulation of adipose tissue. Obesity is a major risk factor for complex disorders such as cancer, type 2 diabetes, and cardiovascular diseases. The ability of mesenchymal stromal/stem cells (MSCs) to differentiate into adipocytes is often used as a model for studying adipogenesis in vitro. A key focus is the effect of both intra- and extracellular reactive oxygen species (ROS) on adipogenesis. The consensus from the majority of studies is that ROS, irrespective of the source, promote adipogenesis.The effect of ROS on adipogenesis is suppressed by antioxidants or ROS scavengers. Reactive oxygen species are generated during the process of adipocyte differentiation as well as by other cell metabolic processes. Despite many studies in this field, it is still not possible to state with certainty whether ROS measured during adipocyte differentiation are a cause or consequence of this process. In addition, it is still unclear what the exact sources are of the ROS that initiate and/or drive adipogenic differentiation in MSCs in vivo. This review provides an overview of our understanding of the role of ROS in adipocyte differentiation as well as how certain ROS scavengers and antioxidants might affect this process.

Comparative study of adipose-derived stem cells and bone marrow-derived stem cells in similar microenvironmental conditions

Mesenchymal stem cells (MSCs), which were first isolated from the bone marrow, are now being extracted from various other tissues in the body, including the adipose tissue. The current study presents systematic evidence of how the adipose tissue-derived stem cells (ASCs) and bone marrow-derived mesenchymal stem cells (Bm-MSCs) behave when cultured in specific pro-adipogenic microenvironments. The cells were first characterized and identified as MSCs in terms of their morphology, phenotypic expression, self-renewal capabilities and multi-lineage potential. Subsequently, the proliferation and gene expression profiles of the cell populations cultured on two-dimensional (2D) adipose tissue extracellular matrix (ECM)-coated tissue culture plastic (TCP) and in three-dimensional (3D) AlgiMatrix® microenvironments were analyzed. Overall, it was found that adipogenesis was triggered in both cell populations due to the presence of adipose tissue ECM. However, in 3D microenvironments, ASCs and Bm-MSCs were predisposed to the adipogenic and osteogenic lineages respectively. Overall, findings from this study will contribute to ongoing efforts in adipose tissue engineering as well as provide new insights into the role of the ECM and cues provided by the immediate microenvironment for stem cell differentiation.

Dynamics of protein secretion during adipocyte differentiation

The major functions of adipocytes include both lipid storage and the production of secretory factors. However, the type of proteins released from mouse 3T3-L1 cells during adipocyte differentiation remains poorly understood. We examined the dynamics of secreted proteins during adipocyte differentiation using mass spectrometry (MS) combined with an iTRAQ (®) labeling method that enables the simultaneous analysis of relative protein expression levels. A total of 215 proteins were identified and quantified from approximately 10 000 MS/MS spectra. Of these, approximately 38% were categorized as secreted proteins based on gene ontology classification. Adipokine secretion levels were increased with the progression of differentiation. By contrast, levels of fibril collagen components, such as subunits of type I and III collagens, were decreased during differentiation. Basement membrane components attained their peak levels at day 4 when small lipid droplets accumulated in differentiated 3T3-L1 cells. Simultaneously, peak levels of collagen microfibril components that comprise type V and VI collagen subunits were also observed. Our data demonstrated that extracellular matrix components were predominantly released during the early and middle stages of adipocyte differentiation, with a subsequent increase in the secretion of adipokines. This suggests that 3T3-L1 cells secrete adipokines after their ECM is constructed during adipocyte differentiation.