Notch signalling inhibits the adipogenic differentiation of single-cell-derived mesenchymal stem cell clones isolated from human adipose tissue

O-GlcNAcylation: roles and potential therapeutic target for bone pathophysiology

O-linked N-acetylglucosamine (O-GlcNAc) protein modification (O-GlcNAcylation) is a critical post-translational modification (PTM) of cytoplasmic and nuclear proteins. O-GlcNAcylation levels are regulated by the activity of two enzymes, O-GlcNAc transferase (OGT) and O‑GlcNAcase (OGA). While OGT attaches O-GlcNAc to proteins, OGA removes O-GlcNAc from proteins. Since its discovery, researchers have demonstrated O-GlcNAcylation on thousands of proteins implicated in numerous different biological processes. Moreover, dysregulation of O-GlcNAcylation has been associated with several pathologies, including cancers, ischemia-reperfusion injury, and neurodegenerative diseases. In this review, we focus on progress in our understanding of the role of O-GlcNAcylation in bone pathophysiology, and we discuss the potential molecular mechanisms of O-GlcNAcylation modulation of bone-related diseases. In addition, we explore significant advances in the identification of O-GlcNAcylation-related regulators as potential therapeutic targets, providing novel therapeutic strategies for the treatment of bone-related disorders.

The optimized priming effect of FGF-1 and FGF-2 enhances preadipocyte lineage commitment in human adipose-derived mesenchymal stem cells

The cell-assisted lipotransfer technique, integrating adipose-derived mesenchymal stem cells (ADMSCs), has transformed lipofilling, enhancing fat graft viability. However, the multipotent nature of ADMSCs poses challenges. To improve safety and graft vitality and to reduce unwanted lineage differentiation, this study refines the methodology by priming ADMSCs into preadipocytes-unipotent, self-renewing cells. We explored the impact of fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2), and epidermal growth factor (EGF), either alone or in combination, on primary human ADMSCs during the proliferative phase. FGF-2 emerged as a robust stimulator of cell proliferation, preserving stemness markers, especially when combined with EGF. Conversely, FGF-1, while not significantly affecting cell growth, influenced cell morphology, transitioning cells to a rounded shape with reduced CD34 expression. Furthermore, co-priming with FGF-1 and FGF-2 enhanced adipogenic potential, limiting osteogenic and chondrogenic tendencies, and possibly promoting preadipocyte commitment. These preadipocytes exhibited unique features: rounded morphology, reduced CD34, decreased preadipocyte factor 1 (Pref-1), and elevated C/EBPα and PPARγ, alongside sustained stemness markers (CD73, CD90, CD105). Mechanistically, FGF-1 and FGF-2 activated key adipogenic transcription factors-C/EBPα and PPARγ-while inhibiting GATA3 and Notch3, which are adipogenesis inhibitors. These findings hold the potential to advance innovative strategies for ADMSC-mediated lipofilling procedures.

Targeted Overexpression of Claudin 11 in Osteoblasts Increases Trabecular Bone Mass by Stimulating Osteogenesis at the Expense of Adipogenesis in Mice

Mice lacking Claudin11 (Cldn11) manifest reduced trabecular bone mass. However, the impact of Cldn11 expression in osteoblasts in vivo remains understudied. Herein, we generated osteoblast-specific transgenic (Tg) mice expressing Cldn11 and characterized their skeletal phenotype. Micro-CT analyses of the distal metaphysis of the femur showed a 50% and a 38% increase in trabecular bone mass in Tg male and female mice, respectively, due to a significant increase in trabecular number and a reduction in trabecular separation. Histomorphometry and serum biomarker studies uncovered that increased trabecular bone mass in Cldn11 Tg mice was the consequence of enhanced bone formation. Accordingly, an abundance of bone formation (Alp, Bsp), but not bone resorption (Ctsk), markers were augmented in the femurs of Cldn11 Tg mice. Since the trabecular bone density is known to inversely correlate with the amount of marrow adipose tissue (MAT), we measured the MAT in osmium-tetroxide-labeled bones by micro-CT scanning. We found 86% less MAT in the proximal tibia of the Tg males. Consistently, the expression levels of the adipogenic markers, adiponectin and leptin, were 50% lower in the femurs of the Tg males. Our data are consistent with the possibility that claudin11 exerts anabolic effects in osteoblastic lineage cells that act via promoting the differentiation of marrow stem cells towards osteoblasts at the expense of adipocytes.

Advanced Progress in the Role of Adipose-Derived Mesenchymal Stromal/Stem Cells in the Application of Central Nervous System Disorders

Currently, adipose-derived mesenchymal stromal/stem cells (ADMSCs) are recognized as a highly promising material for stem cell therapy due to their accessibility and safety. Given the frequently irreversible damage to neural cells associated with CNS disorders, ADMSC-related therapy, which primarily encompasses ADMSC transplantation and injection with exosomes derived from ADMSCs or secretome, has the capability to inhibit inflammatory response and neuronal apoptosis, promote neural regeneration, as well as modulate immune responses, holding potential as a comprehensive approach to treat CNS disorders and improve prognosis. Empirical evidence from both experiments and clinical trials convincingly demonstrates the satisfactory safety and efficacy of ADMSC-related therapies. This review provides a systematic summary of the role of ADMSCs in the treatment of central nervous system (CNS) disorders and explores their therapeutic potential for clinical application. ADMSC-related therapy offers a promising avenue to mitigate damage and enhance neurological function in central nervous system (CNS) disorders. However, further research is necessary to establish the safety and efficacy of clinical ADMSC-based therapy, optimize targeting accuracy, and refine delivery approaches for practical applications.

Notch signaling regulates a metabolic switch through inhibiting PGC-1α and mitochondrial biogenesis in dedifferentiated liposarcoma

Human dedifferentiated liposarcoma (DDLPS) is a rare but lethal cancer with no driver mutations being identified, hampering the development of targeted therapies. We and others recently reported that constitutive activation of Notch signaling through overexpression of the Notch1 intracellular domain (NICDOE) in murine adipocytes leads to tumors resembling human DDLPS. However, the mechanisms underlying the oncogenic functions of Notch activation in DDLPS remains unclear. Here, we show that Notch signaling is activated in a subset of human DDLPS and correlates with poor prognosis and expression of MDM2, a defining marker of DDLPS. Metabolic analyses reveal that murine NICDOE DDLPS cells exhibit markedly reduced mitochondrial respiration and increased glycolysis, mimicking the Warburg effect. This metabolic switch is associated with diminished expression of peroxisome proliferator-activated receptor gamma coactivator 1α (Ppargc1a, encoding PGC-1α protein), a master regulator of mitochondrial biogenesis. Genetic ablation of the NICDOE cassette rescues the expression of PGC-1α and mitochondrial respiration. Similarly, overexpression of PGC-1α is sufficient to rescue mitochondria biogenesis, inhibit the growth and promote adipogenic differentiation of DDLPS cells. Together, these data demonstrate that Notch activation inhibits PGC-1α to suppress mitochondrial biogenesis and drive a metabolic switch in DDLPS.

A Wrong Fate Decision in Adipose Stem Cells upon Obesity

Progress has been made in identifying stem cell aging as a pathological manifestation of a variety of diseases, including obesity. Adipose stem cells (ASCs) play a core role in adipocyte turnover, which maintains tissue homeostasis. Given aberrant lineage determination as a feature of stem cell aging, failure in adipogenesis is a culprit of adipose hypertrophy, resulting in adiposopathy and related complications. In this review, we elucidate how ASC fails in entering adipogenic lineage, with a specific focus on extracellular signaling pathways, epigenetic drift, metabolic reprogramming, and mechanical stretch. Nonetheless, such detrimental alternations can be reversed by guiding ASCs towards adipogenesis. Considering the pathological role of ASC aging in obesity, targeting adipogenesis as an anti-obesity treatment will be a key area of future research, and a strategy to rejuvenate tissue stem cell will be capable of alleviating metabolic syndrome.

The Notch signalling pathway and miRNA regulation play important roles in the differentiation of Schwann cells from adipose-derived stem cells

An exploration of the underlying mechanisms is necessary to improve nerve myelin-forming cell Schwann cell (SC) differentiation from adipose-derived stem cells (ADSCs). Primary rat ADSCs were isolated and characterised for cell surface markers using flow cytometry analysis. After treatment with a mixture of glial growth factors, ADSCs were induced to differentiate and subsequently identified by immunofluorescence staining and western blotting. A miRNA microarray analysis was performed to explore the genes and signalling pathways regulating ADSC differentiation into SCs. ELISAs were conducted to measure the expression of neurotrophic factors and changes in the level of nerve cell adhesion factor. Dual luciferase reporter assays and RIP assays were performed to explore the potential mechanism of miR-21-5p in ADSC differentiation. The isolated ADSCs were positive for CD29 and CD44 but negative for CD49. After induction with specific cytokines, the differentiated ADSCs presented a spindle-like morphology similar to SCs and expressed S100. RNA-sequencing analyses revealed that 9821 mRNAs of protein-coding genes and 175 miRNAs were differentially expressed in differentiated SC-like cells compared to primary cultures of ADSCs. KEGG and Gene Ontology analyses revealed that the involvement of the Notch signalling pathway and miRNA negative regulation may be associated with the differentiation of ADSCs into SCs. Treatment with a Notch inhibitor promoted the differentiation of ADSCs. Furthermore, mechanistic studies showed that Jag1 bound to miR-21-5p and upregulated its target gene Jag1, thus affecting ADSC differentiation. These results revealed the mechanism underlying the important roles of miRNAs and the Notch signalling pathway in the differentiation of SCs from ADSCs, enabling potential therapeutic applications of ADSCs in peripheral nerve regeneration in the future.

Let-7a-5p regulated by lncRNA-MEG3 promotes functional differentiation to Schwann cells from adipose derived stem cells via directly inhibiting RBPJ-mediating Notch pathway

Schwann cells (SCs) have important roles in supporting and repairing peripheral neurons, and thus have great potential for nerve injury treatment. Adipose tissue-derived stem cells (ADSCs) can be reliably induced to differentiate into SCs. However, the underlying molecular mechanisms are unclear. We explored the roles of MEG3/let-7a-5p/RBPJ axis in the differentiation into SCs from ADSCs. Primary ADSCs were induced to differentiate into SCs by appropriate reagents. ELISA, immunostaining, Western blotting, and qRT-PCR were employed to examine levels of SC-markers such as S100, GFAP, SOX10, p75NTR, GAP43, MPZ, β-NGF, BDNF, and NCAM and let-7 family, MEG3, RBPJ, and Notch signaling related proteins. Dual luciferase assay and RNA immunoprecipitation were performed to validate interactions of let-7a-5p/RBPJ mRNA and MEG3/let-7a-5p. Cultured ADSCs could be induced to differentiate into functional SCs. Let-7a-5p and let-7d-5p were elevated during the differentiation while MEG3 and RBPJ/Notch-signaling were suppressed. Let-7a-5p mimics promoted ADSC differentiation into SCs and up-regulated the levels of SC-related markers including S100, GFAP, SOX10, p75NTR, GAP43, MPZ, β-NGF, and NCAM, while RBPJ or MEG3 overexpression retarded the differentiation and reduced those levels. Let-7a-5p directly targeted RBPJ and MEG3 disinhibited Notch-RBPJ signaling via sponging let-7a-5p. RBPJ overexpression reversed the acceleration of let-7a-5p mimics on SC differentiation while let-7a-5p mimics blocked MEG3-mediated suppression on SC differentiation. Let-7a-5p sponged by MEG3 promotes differentiation of ADSCs into SCs via suppressing Notch signaling by targeting RBPJ. These findings shed light on mechanisms underlying the differentiation of ADSCs to SCs and provide avenues to accelerate the process.

Human dental pulp stem cell responses to different dental pulp capping materials

Background

Direct pulp capping is a vital pulp therapy for a pin-point dental pulp exposure. Applying a pulp capping material leads to the formation of a dentin bridge and protects pulp vitality. The aim of this study was to compare the effects of four dental materials, DyCal^®, ProRoot^® MTA, Biodentine™, and TheraCal™ LC in vitro.

Methods

Human dental pulp stem cells (hDPs) were isolated and characterized. Extraction medium was prepared from the different pulp capping materials. The hDP cytotoxicity, proliferation, and migration were examined. The odonto/osteogenic differentiation was determined by alkaline phosphatase, Von Kossa, and alizarin red s staining. Osteogenic marker gene expression was evaluated using real-time polymerase chain reaction.

Results

ProRoot^® MTA and Biodentine™ generated less cytotoxicity than DyCal^® and TheraCal™ LC, which were highly toxic. The hDPs proliferated when cultured with the ProRoot^® MTA and Biodentine™ extraction media. The ProRoot^® MTA and Biodentine™ extraction medium induced greater cell attachment and spreading. Moreover, the hDPs cultured in the ProRoot^® MTA or Biodentine™ extraction medium migrated in a similar manner to those in serum-free medium, while a marked reduction in cell migration was observed in the cells cultured in DyCal^® and TheraCal™ LC extraction media. Improved mineralization was detected in hDPs maintained in ProRoot^® MTA or Biodentine™ extraction medium compared with those in serum-free medium.

Conclusion

This study demonstrates the favorable in vitro biocompatibility and bioactive properties of ProRoot^® MTA and Biodentine™ on hDPs, suggesting their superior regenerative potential compared with DyCal^® and TheraCal™.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01544-w.

hPER3 promotes adipogenesis via hHSP90AA1-mediated inhibition of Notch1 pathway

The period circadian regulator 3 (PER3) has been reported to play a negative role in human immortalized bone marrow-derived Scp-1 cells (iBMSCs) and patient adipose-derived stromal cells (PASCs) or a negative/positive role in mice adipogenesis. However, human PER3 (hPER3) was identified as a positive regulator of human adipose tissue-derived stromal cells (hADSCs) adipogenesis in this study. Silencing or overexpression of hPER3 in hADSCs inhibited and promoted adipogenesis in vitro. In vivo, the overexpression of hPER3 increased high-fat diet-induced inguinal white adipose tissue (iWAT) and epididymal white adipose tissue (eWAT) forms, increasing systemic glucose intolerance and insulin resistance. Molecularly, hPER3 does not interact with hPPARγ, but represses Notch1 signaling pathway to enhance adipogenesis by interacting with hHSP90AA1, which is able to combine with the promoter of hNotch1 and inactivate its expression. Thus, our study revealed hPER3 as a critical positive regulator of hADSCs adipogenesis, which was different from the other types of cells, providing a critical role of it in treating obesity.

Cellular Heterogeneity in Adipose Tissues

Adipose tissue depots in distinct anatomical locations mediate key aspects of metabolism, including energy storage, nutrient release, and thermogenesis. Although adipocytes make up more than 90% of adipose tissue volume, they represent less than 50% of its cellular content. Here, I review recent advances in genetic lineage tracing and transcriptomics that reveal the identities of the heterogeneous cell populations constituting mouse and human adipose tissues. In addition to mature adipocytes and their progenitors, these include endothelial and various immune cell types that together orchestrate adipose tissue development and functions. One salient finding is the identification of progenitor subtypes that can modulate adipogenic capacity through paracrine mechanisms. Another is the description of fate trajectories of monocyte/macrophages, which can respond maladaptively to nutritional and thermogenic stimuli, leading to metabolic disease. These studies have generated an extraordinary source of publicly available data that can be leveraged to explore commonalities and differences among experimental models, providing new insights into adipose tissues and their role in metabolic disease.

Gelatin Methacryloyl (GelMA) Nanocomposite Hydrogels Embedding Bioactive Naringin Liposomes

The development of nanocomposite hydrogels that take advantage of hierarchic building blocks is gaining increased attention due to their added functionality and numerous biomedical applications. Gathering on the unique properties of these platforms, herein we report the synthesis of bioactive nanocomposite hydrogels comprising naringin-loaded salmon-derived lecithin nanosized liposomal building blocks and gelatin methacryloyl (GelMA) macro-sized hydrogels for their embedding. This platform takes advantage of liposomes’ significant drug loading capacity and their role in hydrogel network reinforcement, as well as of the injectability and light-mediated crosslinking of bioderived gelatin-based biomaterials. First, the physicochemical properties, as well as the encapsulation efficiency, release profile, and cytotoxicity of naringin-loaded nanoliposomes (LipoN) were characterized. Then, the effect of embedding LipoN in the GelMA matrix were characterized by studying the release behavior, swelling ratio, and hydrophilic character, as well as the rheological and mechanical properties of GelMA and GelMA-LipoN functionalized hydrogels. Finally, the dispersion of nanoliposomes encapsulating a model fluorescent probe in the GelMA matrix was visualized. The formulation of naringin-loaded liposomes via an optimized procedure yielded nanosized (114 nm) negatively charged particles with a high encapsulation efficiency (~99%). Naringin-loaded nanoliposomes administration to human adipose-derived stem cells confirmed their suitable cytocompatibility. Moreover, in addition to significantly extending the release of naringin from the hydrogel, the nanoliposomes inclusion in the GelMA matrix significantly increased its elastic and compressive moduli and decreased its swelling ratio, while showing an excellent dispersion in the hydrogel network. Overall, salmon-derived nanoliposomes enabled the inclusion and controlled release of pro-osteogenic bioactive molecules, as well as improved the hydrogel matrix properties, which suggests that these soft nanoparticles can play an important role in bioengineering bioactive nanocomposites for bone tissue engineering in the foreseeable future.

Distinct roles for Notch1 and Notch3 in human adipose-derived stem/stromal cell adipogenesis

The role of the Notch signaling pathway in adipogenesis has long been controversial as the action of individual Notch receptors appears to vary with experimental conditions. In this study, we offer some explanation for the observed contradictions by comparing the role of both Notch1 and Notch3 in regulating the expression of key adipogenic regulator, PPARγ, in human adipose-derived stem/stromal cells (hADSCs) during in vitro adipogenesis. Utilizing qRT-PCR, western blot, and immunofluorescence staining, we demonstrated that Notch3 was expressed prior to the formation of lipid vesicles, while Notch1 only appeared after vesicle formation. In addition, following the induction of adipogenesis, the levels of Notch1 intracellular domain in the nucleus were significantly reduced, while the siRNA-mediated loss of Notch1 reduced transcript but not protein levels of PPARγ. The knockdown of Notch3 led to increased expression of PPARγ during early adipogenesis that was not paralleled by a decreased expression of Hes1 and Hey1, but was accompanied by a marked decrease in the protein level of β-catenin, the key functional component of the canonical Wnt/β-catenin signaling pathway. This study deepens the understanding of the Notch pathway by clarifying the distinct roles of Notch1 and Notch3 during adipogenesis. We showed that Notch3 is involved in early adipogenic differentiation, while Notch1 functions later in the process. In addition, we begin to uncover the interaction between the Notch and Wnt signaling pathways that may offer novel therapeutic targets aimed at obesity and diabetes.

In Vitro Evaluation of Clinical Candidates of γ-Secretase Inhibitors: Effects on Notch Inhibition and Promoting Beige Adipogenesis and Mitochondrial Biogenesis

PURPOSE

Inhibition of Notch signaling has been recently demonstrated to promote beige adipocyte biogenesis. However, most γ-secretase inhibitors (GSIs) used to achieve pharmacological inhibition of Notch signaling are at the basic research or preclinical stage, limiting the translation of fundamental findings into clinical practice. This present study aimed to evaluate the potential of several clinical candidates of GSIs as browning agents for the treatment of obesity.

METHODS

Seven GSIs that are clinical candidates for the treatment of Alzheimer's disease or cancer were selected and their impacts on Notch inhibition as well as promoting beige biogenesis were compared using in vitro culture of 3T3-L1 preadipocytes.

RESULTS

Four compounds (i.e.RO4929097, PF-03084014, LY3039478, and BMS-906024) that efficiently inhibited the expression of Notch target genes in 3T3-L1 preadipocytes were identified. Moreover, these compounds were optimized for dose-dependent effects at three gradient concentrations (0.5, 1, and 10 μM) to promote beige adipogenesis and mitochondrial biogenesis in 3T3-L1 preadipocytes without causing severe cytotoxicity.

CONCLUSIONS

Our findings not only highlight the potential of cross-therapeutic application of these GSIs for obesity treatment via inhibition of γ-secretase-mediated processing of Notch signaling, but also provide important experimental evidence to support further design and development of clinically translatable Notch-inhibiting drug delivery systems.

Pathological Conversion of Mouse Perivascular Adipose Tissue by Notch Activation

OBJECTIVE

Perivascular adipose tissue (PVAT) surrounding arteries supports healthy vascular function. During obesity, PVAT loses its vasoprotective effect. We study pathological conversion of PVAT, which involves molecular changes in protein profiles and functional changes in adipocytes. Approach and Results: C57BL6/J mice were fed a 60% high-fat diet for 12 weeks or a cardioprotective 30% calorie-restricted diet for 5 weeks. Proteomic analysis identified PVAT as a molecularly distinct adipose depot, and novel markers for thermogenic adipocytes, such as GRP75 (stress-70 protein, mitochondrial), were identified. High-fat diet increased the similarity of protein signatures in PVAT and brown adipose, suggesting activation of a conserved whitening pathway. The whitening phenotype was characterized by suppression of UCP1 (uncoupling protein 1) and increased lipid deposition, leptin, and inflammation, and specifically in PVAT, elevated Notch signaling. Conversely, PVAT from calorie-restricted mice had decreased Notch signaling and less lipid. Using the Adipoq-Cre strain, we constitutively activated Notch1 signaling in adipocytes, which phenocopied the changes in PVAT caused by a high-fat diet, even on a standard diet. Preadipocytes from mouse PVAT expressed Sca1, CD140a, Notch1, and Notch2, but not CD105, showing differences compared with preadipocytes from other depots. Inhibition of Notch signaling during differentiation of PVAT-derived preadipocytes reduced lipid deposition and adipocyte marker expression.

CONCLUSIONS

PVAT shares features with other adipose depots, but has a unique protein signature that is regulated by dietary stress. Increased Notch signaling in PVAT is sufficient to initiate the pathological conversion of PVAT by promoting adipogenesis and lipid accumulation and may thus prime the microenvironment for vascular disease.

Transcriptome analysis of basic fibroblast growth factor treated stem cells isolated from human exfoliated deciduous teeth

Background

Basic fibroblast growth factor (bFGF) regulates cell proliferation, migration, and differentiation in various cell types. The aim of the present study was to determine the bFGF target genes in stem cells isolated from human exfoliated deciduous teeth (SHEDs).

Methods

Cells were isolated from pulp tissue obtained from exfoliated deciduous teeth. Mesenchymal stem cell surface markers and the differentiation potential toward adipogenic and neurogenic lineages were characterized. The bFGF-treated SHED transcriptome was examined using a high throughput RNA sequencing technique. The mRNA and protein expression of selected genes were evaluated using real-time polymerase chain reaction and immunofluorescence staining, respectively. Cell cycle analysis was performed by flow cytometry. The colony forming unit number was also examined.

Results

The isolated cells expressed CD44, CD90, CD105, but not CD45. The upregulation of adipogenic and neurogenic marker genes was observed after culturing cells in the appropriate induction medium. Transcriptome analysis of the bFGF treated cells revealed that the upregulated genes were in the cell cycle related pathways, while the downregulated genes were in the extracellular matrix related pathways. Correspondingly, bFGF induced MKI67 mRNA expression and Ki67 protein expression. Furthermore, bFGF treatment significantly decreased the G0/G1, but increased the G2/M, population in SHEDs. Colony formation was markedly increased in the bFGF treated group and was attenuated by pretreating the cells with FGFR or PI3K inhibitors.

Conclusion

bFGF controls cell cycle progression in SHEDs. Thus, it can be used to amplify cell number to obtain the amount of cells required for regenerative treatments.

The Role of Pref-1 during Adipogenic Differentiation: An Overview of Suggested Mechanisms

Obesity contributes significantly to the global health burden. A better understanding of adipogenesis, the process of fat formation, may lead to the discovery of novel treatment strategies. However, it is of concern that the regulation of adipocyte differentiation has predominantly been studied using the murine 3T3-L1 preadipocyte cell line and murine experimental animal models. Translation of these findings to the human setting requires confirmation using experimental models of human origin. The ability of mesenchymal stromal/stem cells (MSCs) to differentiate into adipocytes is an attractive model to study adipogenesis in vitro. Differences in the ability of MSCs isolated from different sources to undergo adipogenic differentiation, may be useful in investigating elements responsible for regulating adipogenic differentiation potential. Genes involved may be divided into three broad categories: early, intermediate and late-stage regulators. Preadipocyte factor-1 (Pref-1) is an early negative regulator of adipogenic differentiation. In this review, we briefly discuss the adipogenic differentiation potential of MSCs derived from two different sources, namely adipose-derived stromal/stem cells (ASCs) and Wharton’s Jelly derived stromal/stem cells (WJSCs). We then discuss the function and suggested mechanisms of action of Pref-1 in regulating adipogenesis, as well as current findings regarding Pref-1’s role in human adipogenesis.

Adipocyte dedifferentiation in health and diseases

Adipose tissues collectively as an endocrine organ and energy storage are crucial for systemic metabolic homeostasis. The major cell type in the adipose tissue, the adipocytes or fat cells, are remarkably plastic and can increase or decrease their size and number to adapt to changes in systemic or local metabolism. Changes in adipocyte size occur through hypertrophy or atrophy, and changes in cell numbers mainly involve de novo generation of new cells or death of existing cells. Recently, dedifferentiation, whereby a mature adipocyte is reverted to an undifferentiated progenitor-like status, has been reported as a mechanism underlying adipocyte plasticity. Dedifferentiation of mature adipocytes has been observed under both physiological and pathological conditions. This review covers several aspects of adipocyte dedifferentiation, its relevance to adipose tissue function, molecular pathways that drive dedifferentiation, and the potential of therapeutic targeting adipocyte dedifferentiation in human health and metabolic diseases.

At the Crossroads of the Adipocyte and Osteoclast Differentiation Programs: Future Therapeutic Perspectives

The coordinated development and function of bone-forming (osteoblasts) and bone-resorbing (osteoclasts) cells is critical for the maintenance of skeletal integrity and calcium homeostasis. An enhanced adipogenic versus osteogenic potential of bone marrow mesenchymal stem cells (MSCs) has been linked to bone loss associated with diseases such as diabetes mellitus, as well as aging and postmenopause. In addition to an inherent decrease in bone formation due to reduced osteoblast numbers, recent experimental evidence indicates that an increase in bone marrow adipocytes contributes to a disproportionate increase in osteoclast formation. Therefore, a potential strategy for therapeutic intervention in chronic bone loss disorders such as osteoporosis is to interfere with the pro-osteoclastogenic influence of marrow adipocytes. However, application of this approach is limited by the extremely complex regulatory processes in the osteoclastogenic program. For example, key regulators of osteoclastogenesis such as the receptor activator of nuclear factor-kappaB ligand (RANKL) and the soluble decoy receptor osteoprotegerin (OPG) are not only secreted by both osteoblasts and adipocytes, but are also regulated through several cytokines produced by these cell types. In this context, biologically active signaling molecules secreted from bone marrow adipocytes, such as chemerin, adiponectin, leptin, visfatin and resistin, can have a profound influence on the osteoclast differentiation program of hematopoietic stem cells (HSCs), and thus, hold therapeutic potential under disease conditions. In addition to these paracrine signals, adipogenic transcription factors including CCAAT/enhancer binding protein alpha (C/EBPα), C/EBP beta (C/EBPβ) and peroxisome proliferator-associated receptor gamma (PPARγ) are also expressed by osteoclastogenic cells. However, in contrast to MSCs, activation of these adipogenic transcription factors in HSCs promotes the differentiation of osteoclast precursors into mature osteoclasts. Herein, we discuss the molecular mechanisms that link adipogenic signaling molecules and transcription factors to the osteoclast differentiation program and highlight therapeutic strategies targeting these mechanisms for promoting bone homeostasis.

MicroRNA-150 Modulates Adipogenic Differentiation of Adipose-Derived Stem Cells by Targeting Notch3

MicroRNAs (miRNAs) influence stem cell functions, including mobilization, proliferation, and differentiation. miR-150 is abundantly expressed in monocytes. Knockdown of miR-150 promotes bone marrow stem cell migration. The role of miR-150 in adipose-derived stem cells (ADSCs) is unclear. In this study, the effects of miR-150 on adipogenic differentiation and proliferation of ADSCs were investigated. ADSCs were isolated from the inguinal adipose tissue of wild-type (WT) and miR-150 knockout (KO) mice and were induced for adipogenic differentiation. The miR-150 level was detected by real-time PCR. ADSCs were transfected by miR-150 or small-interfering RNA (siRNA) of Notch3. MTT assay and colony formation assay were performed in miR-150 knockdown and control ADSCs. Real-time PCR showed that miR-150 was expressed in ADSCs. miR-150 knockdown significantly decreased the capacity of adipogenic differentiation of ADSCs, as compared with their counterparts from WT mice. It is intriguing that the overexpression of miR-150 significantly increased C/EBPα and PPAR-γ expression and lipid formation in ADSCs with adipogenic induction. Overexpression of miR-150 significantly decreased Notch3 expression in ADSCs compared with the control groups. Furthermore, Notch3 inhibition promoted the adipogenic differentiation in ADSCs. miR-150 also suppressed proliferation potential and the expression of Nanog in ADSCs. In summary, this study demonstrates, for the first time, that miR-150 promotes adipogenic differentiation and inhibits proliferation of ADSCs. miR-150 regulates adipogenic differentiation of ADSCs, likely mediated by the downregulation of Notch3.

Determinants of stem cell lineage differentiation toward chondrogenesis versus adipogenesis

Adult stem cells, also termed as somatic stem cells, are undifferentiated cells, detected among differentiated cells in a tissue or an organ. Adult stem cells can differentiate toward lineage specific cell types of the tissue or organ in which they reside. They also have the ability to differentiate into mature cells of mesenchymal tissues, such as cartilage, fat and bone. Despite the fact that the balance has been comprehensively scrutinized between adipogenesis and osteogenesis and between chondrogenesis and osteogenesis, few reviews discuss the relationship between chondrogenesis and adipogenesis. In this review, the developmental and transcriptional crosstalk of chondrogenic and adipogenic lineages are briefly explored, followed by elucidation of signaling pathways and external factors guiding lineage determination between chondrogenic and adipogenic differentiation. An in-depth understanding of overlap and discrepancy between these two mesenchymal tissues in lineage differentiation would benefit regeneration of high-quality cartilage tissues and adipose tissues for clinical applications.

Bioinstructive Naringin-Loaded Micelles for Guiding Stem Cell Osteodifferentiation

Naringin is a naturally occurring flavanone with recognized neuroprotective, cardioprotective, anti-inflammatory, and antiosteoporotic properties. Herein, the delivery of Naringin-loaded methoxy-poly(ethylene glycol)-maleimide-thiol-poly(l-lactide) (mPEGMSPLA) diblock polymeric micelles to human adipose-derived stem cells (hASCs) with the aim to augment its pro-osteogenic effect in these cells is reported for the first time. The synthesis of the diblock copolymer is performed via Michael-type addition reaction between hydrophilic methoxy-poly(ethylene glycol)-maleimide (mPEGMAL) and hydrophobic thiol-poly(l-lactide) (PLASH) and confirmed by ¹ H NMR and attenuated total reflectance Fourier transformed infrared (ATR-FTIR) spectroscopy. The resulting mPEGMSPLA copolymer self-assembles into monodispersed polymeric micelles (≈84.4 ± 2 nm) and presents a high Naringin encapsulation efficiency (87.8 ± 4%), with a sustained release profile at physiological pH. Alongside, in vitro data reveal that upon internalization into hASC 2D cultures, Naringin nanomicellar formulations attain a higher pro-osteogenic effect than that of free drug. Notably, these bioactive carriers also induce superior osteopontin expression and increase matrix mineralization in these cells over free drug administration. Overall, such findings support for the first time the use of polymeric nanomicelles for Naringin delivery into hASCs as a valid approach for modulating stem cell osteogenic differentiation.

Molecular Mechanisms of Transdifferentiation of Adipose-Derived Stem Cells into Neural Cells: Current Status and Perspectives

Neurological diseases can severely compromise both physical and psychological health. Recently, adult mesenchymal stem cell- (MSC-) based cell transplantation has become a potential therapeutic strategy. However, most studies related to the transdifferentiation of MSCs into neural cells have had disappointing outcomes. Better understanding of the mechanisms underlying MSC transdifferentiation is necessary to make adult stem cells more applicable to treating neurological diseases. Several studies have focused on adipose-derived stromal/stem cell (ADSC) transdifferentiation. The purpose of this review is to outline the molecular characterization of ADSCs, to describe the methods for inducing ADSC transdifferentiation, and to examine factors influencing transdifferentiation, including transcription factors, epigenetics, and signaling pathways. Exploring and understanding the mechanisms are a precondition for developing and applying novel cell therapies.

Roles of Notch Signaling in Adipocyte Progenitor Cells and Mature Adipocytes

Adipose tissues, composed with mature adipocytes and preadipocytic stromal/stem cells, play crucial roles in whole body energy metabolism and regenerative medicine. Mature adipocytes are derived and differentiated from mesenchymal stem cells (MSCs) or preadipocytes. This differentiation process, also called adipogenesis, is regulated by several signaling pathways and transcription factors. Notch1 signaling is a highly conserved pathway that is indispensable for stem cell hemostasis and tissue development. In adipocyte progenitor cells, Notch1 signaling regulates the adipogenesis process including proliferation and differentiation of the adipocyte progenitor cells in vitro. Notably, the roles of Notch1 signaling in beige adipocytes formation, adipose development, and function, and the whole body energy metabolism have been recently reported. Here, we mainly review and discuss the roles of Notch1 signaling in adipogenesis in vitro as well as in beige adipocytes formation, adipocytes dedifferentiation, and function in vivo. J. Cell. Physiol. 232: 1258-1261, 2017. © 2016 Wiley Periodicals, Inc.

Identification of CD146 as a marker enriched for tumor-propagating capacity reveals targetable pathways in primary human sarcoma

Tumor-propagating cells (TPCs) are believed to drive cancer initiation, progression and recurrence. These cells are characterized by enhanced tumorigenicity and self-renewal. The ability to identify such cells in primary human sarcomas relies on the dye exclusion ability of tumor side population (SP) cells. Here, we performed a high-throughput cell surface antigen screen and found that CD146 is enriched in the SP population. In vivo serial transplantation assays showed that CD146+ cells are highly tumorigenic, capable of self-renewal and thus enriches for the TPC population. In addition, depletion of SP cells from the CD146+ population show that CD146+ cells and SP cells are a distinct and overlapping TPC populations. Gene expression profiling of CD146+ and SP cells revealed multiple pathways commonly upregulated in both of these populations. Inhibition of one of these upregulated pathways, Notch signaling, significantly reduced tumor growth and self-renewal. Our data demonstrate that CD146 is an effective cell surface marker for enriching TPCs in primary human sarcomas. Targeting differentially activated pathways in TPCs may provide new therapeutic strategies for treating sarcoma.

Use of Hes1-GFP reporter mice to assess activity of the Hes1 promoter in bone cells under chronic inflammation

Notch signaling plays a critical role in maintaining bone homeostasis partially by controlling the formation of osteoblasts from mesenchymal stem cells (MSCs). We reported that TNF activates Notch signaling in MSCs which inhibits osteoblast differentiation in TNF transgenic (TNF-Tg) mice, a mouse model of chronic inflammatory arthritis. In the current study, we used Hes1-GFP and Hes1-GFP/TNF-Tg mice to study the distribution and dynamic change of Notch active cells in normal and inflammatory bone loss and mechanisms mediating their enhanced proliferation. We found that Hes1-GFP+ cells are composed of cells expressing mesenchymal, hematopoietic and endothelial surface markers. CD45-/Hes1-GFP+ cells express high levels of mesenchymal markers and form CFU-F and CFU-ALP colonies. Expansion of CFU-F colonies is associated with a rapid increase in Hes1-GFP+ cell numbers and their GFP intensity. The GFP signal is lost when a CFU-F colony differentiates into an ALP+ osteoblast colony. TNF increases the numbers of CD45-/Hes1-GFP+ cells, which are stained negatively for osteoblast marker osteocalcin and localized adjacent to endosteal and trabecular bone surfaces. CD45-/Hes1-GFP+ cells in Hes1-GFP/TNF-Tg mice have increased BrdU incorporation and PDGFRβ levels. TNF increases the number of proliferating Hes1-GFP+ cells, which is prevented by a specific PDGFRβ inhibitor. Notch inhibition blocks TNF-mediated PDGFRβ expression and cell proliferation. Thus, TNF-induced MSC proliferation is mediated by PDGFRβ signal, which works at downstream of Notch. Hes1-GFP mice can be used to assess the activation status of Notch in bone cells.

Inhibition of Notch rescues the angiogenic potential impaired by cardiovascular risk factors in epicardial adipose stem cells

The epicardial adipose tissue (EAT) is a reservoir of adipose-derived stem cells (ASCs), with as yet unknown effects on myocardial and coronary arteries homeostasis. The purpose of this study was to investigate the angiogenic function of epicardial ASCs and their regulation by the common cardiovascular risk factors (CVRFs) affecting heart disease. Epicardial fat was obtained from a rodent model with clustering of CVRFs [Zucker diabetic fatty (ZDF)-Lepr(fa)] rats and from their lean control (ZDF-Crl) littermates without CVRFs, ASCs were isolated, and their function was assessed by proliferation and differentiation assays, flow cytometry, gene expression, and in vivo Matrigel angiogenesis analysis. Epicardial ASCs from both groups showed adipogenic and osteogenic differentiation capacity; however, epicardial ASCs from CVRF animals had a lesser ability to form tubular structures in vitro after endothelial differentiation, as well as a reduced angiogenic potential in vivo compared to control animals. Epicardial ASCs from CVRF rats showed up-regulation of the downstream Notch signaling genes Hes7, Hey1, and Heyl compared with control animals. The inhibition of Notch signaling by conditioning epicardial ASCs from CVRF animals with a γ-secretase inhibitor induced a reduction in Hes/Hey gene expression and rescued their angiogenic function in vivo We report for the first time the impact of CVRF burden on the ASCs of EAT and that the defective function is in part caused by increased Notch signaling. Conditioning ASCs by blocking Notch signaling rescues their angiogenic potential.-Bejar, M. T., Ferrer-Lorente, R., Peña, E., Badimon, L. Inhibition of Notch rescues the angiogenic potential impaired by cardiovascular risk factors in epicardial adipose stem cells.

MicroRNA-139-5p Suppresses 3T3-L1 Preadipocyte Differentiation Through Notch and IRS1/PI3K/Akt Insulin Signaling Pathways

MicroRNAs (miRNAs) participate in the regulation of adipogenesis. Identification of the full repertoire of miRNAs expressed in adipose tissue is likely to significantly improve our understanding of adipose tissue growth and development. Here, miR-139-5p was identified as an inhibitor of 3T3-L1 adipocyte differentiation with significantly down-regulating the expression levels of adipogenic marker genes PPAR γ (P < 0.01), aP2 (P < 0.01) and FAS (P < 0.01). Importantly, flow cytometry and EdU incorporation assay indicated that this inhibition was partly due to the dysfunction of clonal expansion. Furthermore, we firstly demonstrated that miR-139-5p blocked adipogenesis via directly targeted the 3' untranslated regions (UTRs) of Notch1 and IRS1 mRNAs, a key member of Notch signaling and IRS1/PI3K/Akt insulin signaling, respectively. In addition, the overexpression of Notch1 or IRS1 partially restored the suppressive effects miR-139-5p on differentiation of 3T3-L1 cells. To our knowledge, this was the first report that miR-139-5p functioned negatively by targeting Notch1 and IRS1 during 3T3-L1 adipogenesis, regulating the transition from clonal expansion to terminal differentiation.

Vasopressin-induced Ca(2+) signals in human adipose-derived stem cells

Intracellular Ca(2+) signals are essential for stem cell differentiation due to their ability to control signaling pathways involved in this process. Arginine vasopression (AVP) is a neurohypophyseal hormone that increases intracellular Ca(2+) concentration during adipogenesis via V1a receptors, Gq-proteins and the PLC-IP3 pathway in human adipose-derived stromal/stem cells (hASCs). These Ca(2+) signals originate through calcium release from pools within the endoplasmic reticulum and the extracellular space. AVP supplementation to the adipogenic media inhibits adipogenesis and key adipocyte marker genes. This review focuses on the intersection between AVP, Ca(2+) signals and ASC differentiation.

Notch signaling pathway activation in normal and hyperglycemic rats differs in the stem cells of visceral and subcutaneous adipose tissue

The precise mechanisms underlying the differential function and cardiometabolic risk of white adipose tissue (WAT) remain unclear. Visceral adipose tissue (VWAT) and subcutaneous adipose tissue (SCWAT) have different metabolic functions that seem to be ascribed to their different intrinsic expansion capacities. Here we have hypothesized that the WAT characteristics are determined by the resident adipose-derived stem cells (ASCs) found in the different WAT depots. Therefore, our objective has been to investigate adipogenesis in anatomically distinct fat depots. ASCs from five different WAT depots were characterized in both healthy lean and diabetic obese rats, showing significant differences in expression of some of genes governing the stemness and the earlier adipogenic differentiation steps. Notch-target genes [Hes (hairy and enhancer of split) and Hey (hairy/enhancer of split related with YRPW motif) families] were upregulated in ASCs derived from visceral depots. Upon adipogenic differentiation, adipocyte cell markers were downregulated in ASCs from VWAT in comparison to ASCs from SCWAT, revealing a lower adipogenic capacity in ASCs of visceral origin than in those of SCWAT in accordance with the differential activation of Notch signaling. Notch upregulation by its activator phenethyl isothiocyanate attenuated the adipogenic differentiation of ASCs from SCWAT whereas Notch inhibition by N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) increased the adipogenic differentiation of ASCs from visceral origin. In conclusion, the differential activation of Notch in ASCs is the origin of the different intrinsic WAT expansion capacities that contribute to the regional variations in WAT homeostasis and to its associated cardiometabolic risk.

DAPT inhibits the chondrogenesis of human umbilical cord mesenchymal stem cells

Notch signaling plays a key role in cell proliferation and differentiation, and is important in several biological processes, but its role in the chondrogenesis of human umbilical cord mesenchymal stem cells (UC-MSCs) is still unknown. N-[N-(3,5- difluorophenacetyl-L-alanyl)]-(S)-phenylglycinet-butyl ester (DAPT) is the inhibitor of Notch pathway. The aim of this study is to investgate the influence of DAPT on the chondrogenesis of UC-MSCs. In our study, UC-MSCs were isolated from human umbilical cord and their characteristics were identified. The UC-MSCs were induced to differentiate into chondrocytes in vitro and treated with 5 μM DAPT. Glycosaminoglycan (GAG) and collagen type II (COL-2A1) were analyzed qualitatively and quantitatively. The gene expression of Notch-1, Hes-1, GAG and COL-2A1 were analyzed by quantitative polymerase chain reaction (qPCR). The UC-MSCs separated from human umbilical cord, followed the characteristics of Mesenchymal Stem Cells (MSCs). The gene expression of Notch-1 and Hes-1 decreased after chondrogenic induction but the percentage in G1 period and the content of GAG and COL-2A1 increased. The expression of all tested Notch signaling and proliferation genes declined when 5 μM DAPT was added, also the content of GAG and COL-2A1 also decreased. Our study revealed that Notch signaling exists in UC-MSCs and it may remain the proliferative activity of UC-MSCs. Once the chondrogenesis begins, Notch signaling strength decline evidently. DAPT inhibits the chondrogenesis of UC-MSCs.

Notch signaling as a novel regulator of metabolism

Evolutionarily unprepared for modern high-calorie diets and sedentary lifestyles, humans are now unprecedentedly susceptible to metabolic disorders such as obesity, type 2 diabetes (T2D), nonalcoholic fatty liver, and cardiovascular disease. These metabolic conditions are intertwined, together known as metabolic syndrome, and compromise human life quality as well as lives. Notch signaling, a fundamental signal transduction pathway critical for cell-cell communication and development, has recently been recognized as a key player in metabolism. This review summarizes the emerging roles of Notch signaling in regulating the metabolism of various cell and tissue types, with emphasis on the underlying molecular mechanisms and the potential of targeting this signal axis to treat metabolic diseases.

Comparison of the transcriptomes of mouse skin derived precursors (SKPs) and SKP-derived fibroblasts (SFBs) by RNA-Seq

Skin-derived precursors (SKPs) from dermis possess the capacities of self-renewal and multipotency. In vitro and in vivo studies demonstrated that they can differentiate into fibroblasts. However, little is known about the molecular mechanism of the differentiation of SKPs into fibroblasts. Here we compare the transcriptomes of mouse SKPs and SKP-derived fibroblasts (SFBs) by RNA-Seq analysis, trying to find differences in gene expression between the two kinds of cells and then elucidate the candidate genes that may play important roles in the differentiation of SKPs into fibroblasts. A total of 1971 differentially expressed genes (DEGs) were identified by RNA-Seq, which provided abundant data for further analysis. Gene Ontology enrichment analysis revealed that genes related to cell differentiation, cell proliferation, protein binding, transporter activity and membrane were significantly enriched. The most significantly up-regulated genes Wnt4, Wisp2 and Tsp-1 and down-regulated genes Slitrk1, Klk6, Agtr2, Ivl, Msx1, IL15, Atp6v0d2, Kcne1l and Thbs4 may play important roles in the differentiation of SKPs into fibroblasts. KEGG analysis showed that DEGs were significantly enriched in the TGF-β signaling pathway, Wnt signaling pathway and Notch signaling pathway, which have been previously proven to regulate the differentiation and self-renewal of various stem cells. These identified DEGs and pathways could facilitate further investigations of the detailed molecular mechanisms, making it possible to take advantage of the potential therapeutic applications of SKPs in skin regeneration in the future.

Adipose tissue biology in 2014: Advances in our understanding of adipose tissue homeostasis

In 2014, numerous noteworthy papers focusing on adipose tissue physiology were published. Many of these articles showed the promise of adipose-tissue-targeted approaches for therapeutic intervention in obesity and type 2 diabetes mellitus. Here, we highlight advances in the development and maintenance of brown and/or beige adipocytes and the metabolic implications of infammation in adipose tissues.

MicroRNA-26 family is required for human adipogenesis and drives characteristics of brown adipocytes

Adipose tissue contains thermogenic adipocytes (i.e., brown and brite/beige) that oxidize nutrients at exceptionally high rates via nonshivering thermogenesis. Its recent discovery in adult humans has opened up new avenues to fight obesity and related disorders such as diabetes. Here, we identified miR-26a and -26b as key regulators of human white and brite adipocyte differentiation. Both microRNAs are upregulated in early adipogenesis, and their inhibition prevented lipid accumulation while their overexpression accelerated it. Intriguingly, miR-26a significantly induced pathways related to energy dissipation, shifted mitochondrial morphology toward that seen in brown adipocytes, and promoted uncoupled respiration by markedly increasing the hallmark protein of brown fat, uncoupling protein 1. By combining in silico target prediction, transcriptomics, and an RNA interference screen, we identified the sheddase ADAM metallopeptidase domain 17 (ADAM17) as a direct target of miR-26 that mediated the observed effects on white and brite adipogenesis. These results point to a novel, critical role for the miR-26 family and its downstream effector ADAM17 in human adipocyte differentiation by promoting characteristics of energy-dissipating thermogenic adipocytes.

Inhibition of Notch signaling promotes browning of white adipose tissue and ameliorates obesity

Beige adipocytes in white adipose tissue (WAT) are similar to classical brown adipocytes in that they can burn lipids to produce heat. Thus, an increase in beige adipocyte content in WAT browning would raise energy expenditure and reduce adiposity. Here we report that adipose-specific inactivation of Notch1 or its signaling mediator Rbpj in mice results in browning of WAT and elevated expression of uncoupling protein 1 (Ucp1), a key regulator of thermogenesis. Consequently, as compared to wild-type mice, Notch mutants exhibit elevated energy expenditure, better glucose tolerance and improved insulin sensitivity and are more resistant to high fat diet-induced obesity. By contrast, adipose-specific activation of Notch1 leads to the opposite phenotypes. At the molecular level, constitutive activation of Notch signaling inhibits, whereas Notch inhibition induces, Ppargc1a and Prdm16 transcription in white adipocytes. Notably, pharmacological inhibition of Notch signaling in obese mice ameliorates obesity, reduces blood glucose and increases Ucp1 expression in white fat. Therefore, Notch signaling may be therapeutically targeted to treat obesity and type 2 diabetes.

Alteration of Notch signaling and functionality of adipose tissue derived mesenchymal stem cells in heart failure

AIM

Circulating mesenchymal cells increase in heart failure (HF) patients and could be used therapeutically. Our aim was to investigate whether HF affects adipose tissue derived mesenchymal cell (adMSC) isolation, functional characteristics and Notch pathway.

METHODS AND RESULTS

We compared 25 patients with different degrees of HF (11 NYHA classes I and II and 14 NYHA III and IV) with 10 age and gender matched controls. 100% adMSC cultures were obtained from controls, while only 72.7% and 35.7% from patients with mild or severe HF (p<0.0001). adMSC from HF patients showed higher markers of senescence (p16 positive cells: 14±2.3% in controls and 35.6±5.6% (p<0.05) and 69±14.7% (p<0.01) in mild or severe HF; γ-H2AX positive cells: 3.7±1.2%, 19.4±4.1% (p<0.05) and 23.7±3.4% (p<0.05) respectively), lower proliferation index (Ki67 positive cells: 21.5±4.9%, 13.2±2.8% and 13.7±3.2%, respectively), reduced pluripotency-associated genes (Oct4 positive cells: 86.7±4.9%, 55±12% (p<0.05) and 43.3±8.7% (p<0.05), respectively; NANOG positive cells: 89.8±3.7%, 39.6±14.4% (p<0.01) and 47±8.1%, respectively), and decreased differentiation markers (α-sarcomeric actin positive cells: 79.8±4.6%, 49±18.1% and 47±12.1% (p<0.05) and CD31-positive endothelial cells: 24.5±2.9%, 0.5±0.5% (p<0.001) and 2.3±2.3% (p<0.001), respectively). AdMSC from HF patients also showed reduced Notch transcriptional activity (lowered expression of Hey 1 and Hey 2 mRNAs). Stimulation with TNF-α of adMSC isolated from controls affected the transcription of several components of the Notch pathway (reduction of Notch 4 and Hes 1 mRNAs and increase of Notch 2 and Hey 1 mRNAs).

CONCLUSIONS

In HF yield and functionality of adMSC are impaired and their Notch signaling is downregulated.

Crucial role of Notch signaling in osteogenic differentiation of periodontal ligament stem cells in osteoporotic rats

Estrogen deficiency-induced osteoporosis typically occurs in postmenopausal women and has been strongly associated with periodontal diseases. Periodontal ligament stem cells (PDLSCs) isolated from the periodontal ligament can differentiate into many types of specialized cells, including osteoblast-like cells that contribute to periodontal tissue repair. The Notch signaling pathway is highly conserved and associated with self-renewal potential and cell-fate determination. Recently, several studies have focused on the relationship between Notch signaling and osteogenic differentiation. However, the precise mechanisms underlying this relationship are largely unknown. We have successfully isolated PDLSCs from both ovariectomized (OVX) and sham-operated rats. Both the mRNA and protein levels of Notch1 and Jagged1 were upregulated when PDLSCs were cultured in osteogenic induction media. Mineralization assays showed decreased calcium deposits in OVX-PDLSCs treated with a γ-secretase inhibitor compared with control cells. Thus Notch signaling is important in maintaining the osteogenic differentiation of PDLSCs in osteoporotic rats, which help in the development of a potential therapeutic strategy for periodontal disease in postmenopausal women.

HES1 inhibits adipogenesis of porcine mesenchymal stem cells via transcriptional repression of FAD24

Adipogenesis, the development from preadipocytes or mesenchymal stem cells (MSCs) to mature adipocytes, is regulated by a network of signaling pathways and transcription factors. The involvement of Notch signaling and its effector HES1 in adipogenesis has been investigated in several studies with conflicting results. The underlying mechanisms remain unclear because of the lack of information about HES1 target genes during adipocyte differentiation. As a novel gene transiently up-regulated in early adipogenesis, FAD24 functions as a positive regulator of adipocyte differentiation in both preadipocytes and MSCs. In the present study, we report that the expression level of FAD24 is inversely associated with that of HES1 in porcine MSCs after adipogenic induction. Enforced overexpression of HES1 in MSCs during the early stage of adipogenesis significantly repressed the transcription of FAD24 (P < 0.01) and the other pro-adipogenic genes (P < 0.05), resulting in reduced intracellular lipid accumulation. Sequence analysis showed that porcine FAD24 harbors an evolutionarily conserved HES1 binding site in its proximal promoter region. Functional HES1, but not its dominant-negative mutant, markedly reduced the promoter activity of FAD24 (P < 0.01). Site-directed mutation and chromatin immunoprecipitation further confirmed that HES1 inhibits FAD24 transcription by direct binding to the promoter. Taken together, we identified FAD24 as a novel downstream target of HES1 during adipogenesis. Our data suggest that HES1-mediated repression of FAD24 transcription at the early stage of adipocyte differentiation may contribute to the impaired adipogenesis induced by the Notch-HES1 signaling pathway.