Role of the TGF-β pathway in dedifferentiation of human mature adipocytes

Quantification of cell cycle re-entry during dedifferentiation of primary adipocytes in vitro

Dedifferentiated adipose tissue (DFAT) has been proposed as a promising source of patient-specific multipotent progenitor cells (MPPs). During induced dedifferentiation, adipocytes exhibit profound gene expression and cell morphology changes. However, dedifferentiation of post-mitotic cells is expected to enable proliferation, which is critical if enough MPPs are to be obtained. Here, lineage tracing was employed to quantify cell proliferation in mouse adipocytes subjected to a dedifferentiation-inducing protocol commonly used to obtain DFAT cells. No evidence of cell proliferation in adipocyte-derived cells was observed, in contrast to the robust proliferation of non-adipocyte cells present in adipose tissue. We conclude that proliferative MPPs derived using the ceiling culture method most likely arise from non-adipocyte cells in adipose tissue.

A Closer Look into White Adipose Tissue Biology and the Molecular Regulation of Stem Cell Commitment and Differentiation

White adipose tissue (WAT) makes up about 20-25% of total body mass in healthy individuals and is crucial for regulating various metabolic processes, including energy metabolism, endocrine function, immunity, and reproduction. In adipose tissue research, "adipogenesis" is commonly used to refer to the process of adipocyte formation, spanning from stem cell commitment to the development of mature, functional adipocytes. Although, this term should encompass a wide range of processes beyond commitment and differentiation, to also include other stages of adipose tissue development such as hypertrophy, hyperplasia, angiogenesis, macrophage infiltration, polarization, etc.… collectively, referred to herein as the adipogenic cycle. The term "differentiation", conversely, should only be used to refer to the process by which committed stem cells progress through distinct phases of subsequent differentiation. Recognizing this distinction is essential for accurately interpreting research findings on the mechanisms and stages of adipose tissue development and function. In this review, we focus on the molecular regulation of white adipose tissue development, from commitment to terminal differentiation, and examine key functional aspects of WAT that are crucial for normal physiology and systemic metabolic homeostasis.

Lipid-associated macrophages reshape BAT cell identity in obesity

Obesity and type 2 diabetes cause a loss in brown adipose tissue (BAT) activity, but the molecular mechanisms that drive BAT cell remodeling remain largely unexplored. Using a multilayered approach, we comprehensively mapped a reorganization in BAT cells. We uncovered a subset of macrophages as lipid-associated macrophages (LAMs), which were massively increased in genetic and dietary model of BAT expansion. LAMs participate in this scenario by capturing extracellular vesicles carrying damaged lipids and mitochondria released from metabolically stressed brown adipocytes. CD36 scavenger receptor drove LAM phenotype, and CD36-deficient LAMs were able to increase brown fat genes in adipocytes. LAMs released transforming growth factor β1 (TGF-β1), which promoted the loss of brown adipocyte identity through aldehyde dehydrogenase 1 family member A1 (Aldh1a1) induction. These findings unfold cell dynamic changes in BAT during obesity and identify LAMs as key responders to tissue metabolic stress and drivers of loss of brown adipocyte identity.

The transdifferentiation of human dedifferentiated fat cells into fibroblasts: An in vitro experimental pilot study

BACKGROUND

Skin grafting is a common method of treating damaged skin; however, surgical complications may arise in patients with poor health. Currently, no effective conservative treatment is available for extensive skin loss. Mature adipocytes, which constitute a substantial portion of adipose tissue, have recently emerged as a potential source of stemness. When de-lipidated, these cells exhibit fibroblast-like characteristics and the ability to redifferentiate, offering homogeneity and research utility as "dedifferentiated fat cells."

METHODS AND RESULTS

We conducted an in vitro study to induce fibroblast-like traits in the adipose tissue by transdifferentiating mature adipocytes for skin regeneration. Human subcutaneous fat tissues were isolated and purified from mature adipocytes that underwent a transformation process over 14 days of cultivation. Microscopic analysis revealed lipid degradation over time, ultimately transforming cells into fibroblast-like forms. Flow cytometry was used to verify their characteristics, highlighting markers such as CD90 and CD105 (mesenchymal stem cell markers) and CD56 and CD106 (for detecting fibroblast characteristics). Administering dedifferentiated fat cells with transforming growth factor-β at the identified optimal differentiation concentration of 5 ng/mL for a span of 14 days led to heightened expression of alpha smooth muscle actin and fibronectin, as evidenced by RNA and protein analysis. Meanwhile, functional validation through cell sorting demonstrated limited fibroblast marker expression in both treated and untreated cells after transdifferentiation by transforming growth factor-β.

CONCLUSION

Although challenges remain in achieving more effective transformation and definitive fibroblast differentiation, our trial could pave the way for a novel skin regeneration treatment strategy.

Hypertonicity induces mitochondrial extracellular vesicles (MEVs) that activate TNF-α and β-catenin signaling to promote adipocyte dedifferentiation

BACKGROUND

Recent studies demonstrated that elevated osmolarity could induce adipocyte dedifferentiation, representing an appealing procedure to generate multipotent stem cells. Here we aim to elucidate the molecular mechanisms that underlie osmotic induction of adipocyte reprogramming.

METHODS

To induce dedifferentiation, the 3T3-L1 or SVF adipocytes were cultured under the hypertonic pressure in 2% PEG 300 medium. Adipocyte dedifferentiation was monitored by aspect ratio measurement, Oil Red staining and qPCR to examine the morphology, lipid droplets, and specific genes of adipocytes, respectively. The osteogenic and chondrogenic re-differentiation capacities of dedifferentiated adipocytes were also examined. To investigate the mechanisms of the osmotic stress-induced dedifferentiation, extracellular vesicles (EVs) were collected from the reprograming cells, followed by proteomic and functional analyses. In addition, qPCR, ELISA, and TNF-α neutralizing antibody (20 ng/ml) was applied to examine the activation and effects of the TNF-α signaling. Furthermore, we also analyzed the Wnt signaling by assessing the activation of β-catenin and applying BML-284, an agonist of β-catenin.

RESULTS

Hypertonic treatment induced dedifferentiation of both 3T3-L1 and the primary stromal vascular fraction (SVF) adipocytes, characterized by morphological and functional changes. Proteomic profiling revealed that hypertonicity induced extracellular vesicles (EVs) containing mitochondrial molecules including NDUFA9 and VDAC. Functionally, the mitochondrial EVs (MEVs) stimulated TNF-α signaling that activates Wnt-β-catenin signaling and adipocyte dedifferentiation. Neutralizing TNF-α inhibited hypertonic dedifferentiation of adipocytes. In addition, direct activation of Wnt-β-catenin signaling using BML-284 could efficiently induce adipocyte dedifferentiation while circumventing the apoptotic effect of the hypertonic treatment.

CONCLUSIONS

Hypertonicity prompts the adipocytes to release MEVs, which in turn enhances the secretion of TNF-α as a pro-inflammatory cytokine during the stress response. Importantly, TNF-α is essential for the activation of the Wnt/β-catenin signaling that drives adipocyte dedifferentiation. A caveat of the hypertonic treatment is apoptosis, which could be circumvented by direct activation of the Wnt/β-catenin signaling using BML-284.

ECM proteins and cationic polymers coating promote dedifferentiation of patient-derived mature adipocytes to stem cells

Reprogramming of mature adipocytes is an attractive research area due to the plasticity of these cells. Mature adipocytes can be reprogrammed in vitro, transforming them into dedifferentiated fat cells (DFATs), which are considered a new type of stem cell, and thereby have a high potential for use in tissue engineering and regenerative medicine. However, there are still no reports or findings on in vitro controlling the dedifferentiation. Although ceiling culture performed in related studies is a relatively simple method, its yield is low and does not allow manipulation of mature adipocytes to increase or decrease the dedifferentiation. In this study, to understand the role of physicochemical surface effects on the dedifferentiation of patient-derived mature adipocytes, the surfaces of cell culture flasks were coated with extracellular matrix, basement membrane proteins, and cationic/anionic polymers. Extracellular matrix such as fibronectin and collagen type I, and basement membrane proteins such as collagen type IV and laminin strongly promoted dedifferentiation of mature adipocytes, with laminin showing the highest effect with a DFAT ratio of 2.98 (±0.84). Interestingly, cationic polymers also showed a high dedifferentiation effect, but anionic polymers did not, and poly(diallyl dimethylammonium chloride) showed the highest DFAT ratio of 2.27 (±2.8) among the cationic polymers. Protein assay results revealed that serum proteins were strongly adsorbed on the surfaces of the cationic polymer coating, including inducing high mature adipocyte adhesion. This study demonstrates for the first time the possibility of regulating the transformation of mature adipocytes to DFAT stem cells by controlling the physicochemical properties of the surface of conventional cell culture flasks.

DFATs derived from infrapatellar fat pad hold advantage on chondrogenesis and adipogenesis to evade age mediated influence

Background

Dedifferentiated fat cells (DFATs) are highly homogeneous and multipotent compared with adipose-derived stromal cells (SCs). Infrapatellar fat pad (IFP)-SCs have advanced chondrogenic potency; however, whether IFP-DFATs could serve as better cell material remains unclear. Here, we aimed to examine the influence of age and body mass index (BMI) on the features of IFPs and IFP-derived cells (IFP-SCs and IFP-DFATs) with exploration of the clinical utilization of IFP-DFATs.

Methods

We collected IFPs with isolation of paired IFP-SCs and IFP-DFATs from individuals aged 65 years and older with distinct body weights who underwent total knee replacement for osteoarthritis (OA). Flow cytometry was used to characterize the cellular immunophenotypes. Adipogenesis and chondrogenesis were performed in vitro. Real-time qPCR, western blotting, and Oil Red O or Alcian blue staining were performed to evaluate inflammation, adipogenesis, and chondrogenesis. RNA sequencing and Seahorse analyses were conducted to explore the underlying mechanisms.

Results

We found that IFPs from old or normal-weight individuals with knee OA were pro-inflammatory, and that interleukin-6 (IL-6) signaling was associated with multiple immune-related molecules, whereas IFP-derived cells could escape the inflammatory properties. Aging plays an important role in diminishing the chondrogenic and adipogenic abilities of IFP-SCs; however, this effect was avoided in IFP-DFATs. Generally, IFP-DFATs presented a steady state of chondrogenesis (less influenced by age) and consistently enhanced adipogenesis compared to paired IFP-SCs in different age or BMI groups. RNA sequencing and Seahorse analysis suggested that the downregulation of eukaryotic initiation factor 2 (EIF2) signaling and enhanced mitochondrial function may contribute to the improved cellular biology of IFP-DFATs.

Conclusions

Our data indicate that IFP-DFATs are superior cell material compared to IFP-SCs for cartilage differentiation and adipogenesis, particularly in advanced aging patients with knee OA.

The translational potential of this article

These results provide a novel concept and supportive evidence for the use of IFP-DFATs for cell therapy or tissue engineering in patients with knee OA. Using Ingenuity Pathway Analysis (IPA) of RNA-seq data and Seahorse analysis of mitochondrial metabolic parameters, we highlighted that some molecules, signaling pathways, and mitochondrial functions are likely to be jointly coordinated to determine the enhanced biological function in IFP-DFATs.

Identification of crucial modules and genes associated with backfat tissue development by WGCNA in Ningxiang pigs

Fat deposition is an economically important trait in pigs. Ningxiang pig, one of the four famous indigenous breeds in China, is characterized by high fat content. The underlying gene expression pattern in different developmental periods of backfat tissue remains unclear, and the purpose of this investigation is to explore the potential molecular regulators of backfat tissue development in Ningxiang pigs. Backfat tissue (three samples for each stage) was initially collected from different developmental stages (60, 120, 180, 240, 300, and 360 days after birth), and histological analysis and RNA sequencing (RNA-seq) were then conducted. Fragments per kilobase of transcript per million (FPKM) method was used to qualify gene expressions, and differentially expressed genes (DEGs) were identified. Furthermore, strongly co-expressed genes in modules, which were named by color, were clustered by Weighted gene co-expression network analysis (WGCNA) based on dynamic tree cutting algorithm. Gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) enrichment were subsequently implemented, and hub genes were described in each module. Finally, QPCR analysis was employed to validate RNA-seq data. The results showed that adipocyte area increased and adipocyte number decreased with development of backfat tissue. A total of 1,024 DEGs were identified in five comparison groups (120 days vs. 60 days, 180 days vs. 120 days, 240 days vs. 180 days, 300 days vs. 240 days, and 360 days vs. 300 days). The turquoise, red, pink, paleturquoise, darkorange, and darkgreen module had the highest correlation coefficient with 60, 120, 180, 240, 300, and 360 days developmental stage, while the tan, black and turquoise module had strong relationship with backfat thickness, adipocyte area, and adipocyte number, respectively. Thirteen hub genes (ACSL1, ACOX1, FN1, DCN, CHST13, COL1A1, COL1A2, COL6A3, COL5A1, COL14A1, OAZ3, DNM1, and SELP) were recognized. ACSL1 and ACOX1 might perform function in the early developmental stage of backfat tissue (60 days), and FN1, DCN, COL1A1, COL1A2, COL5A1, COL6A3, and COL14A1 have unignorable position in backfat tissue around 120 days developmental stage. Besides, hub genes SELP and DNM1 in modules significantly associated with backfat thickness and adipocyte area might be involved in the process of backfat tissue development. These findings contribute to understand the integrated mechanism underlying backfat tissue development and promote the progress of genetic improvement in Ningxiang pigs.

Targeting adipocyte-immune cell crosstalk to control breast cancer progression

Adipocytes are crucial components of breast cancer and are involved in regulating the progression, therapeutic efficacy, and prognosis of breast cancer patients. Characterized by storing energy and producing a variety of secretory factors, adipocytes are responsible for inducing obesity and regulating the tumor immune activity. Adipocytes communicate with tumor infiltrating immune cells through the secreted adipokines, cytokines, and exosomes in the breast cancer TIME, which shapes the tumor supporting environment to facilitate the immune escape of tumor cells. In-depth studies of the crosstalk between adipocytes and TIME can not only provide a more comprehensive regulatory landscape of TIME, but also be conducive to screening novel targets for future precision targeted therapy. The aim of this review is to discuss recent studies for understanding the role of crosstalk between adipocytes and immune cells in shaping the breast cancer immune microenvironment.

Dynamic interplay between IL-1 and WNT pathways in regulating dermal adipocyte lineage cells during skin development and wound regeneration

Dermal adipocyte lineage cells are highly plastic and can undergo reversible differentiation and dedifferentiation in response to various stimuli. Using single-cell RNA sequencing of developing or wounded mouse skin, we classify dermal fibroblasts (dFBs) into distinct non-adipogenic and adipogenic cell states. Cell differentiation trajectory analyses identify IL-1-NF-κB and WNT-β-catenin as top signaling pathways that positively and negatively associate with adipogenesis, respectively. Upon wounding, activation of adipocyte progenitors and wound-induced adipogenesis are mediated in part by neutrophils through the IL-1R-NF-κB-CREB signaling axis. In contrast, WNT activation, by WNT ligand and/or ablation of Gsk3, inhibits the adipogenic potential of dFBs but promotes lipolysis and dedifferentiation of mature adipocytes, contributing to myofibroblast formation. Finally, sustained WNT activation and inhibition of adipogenesis is seen in human keloids. These data reveal molecular mechanisms underlying the plasticity of dermal adipocyte lineage cells, defining potential therapeutic targets for defective wound healing and scar formation.

Uncoupling Lipid Synthesis from Adipocyte Development

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

The Role of IL-13 and IL-4 in Adipose Tissue Fibrosis

White adipose tissue (WAT) fibrosis, characterized by an excess of extracellular (ECM) matrix components, is strongly associated with WAT inflammation and dysfunction due to obesity. Interleukin (IL)-13 and IL-4 were recently identified as critical mediators in the pathogenesis of fibrotic diseases. However, their role in WAT fibrosis is still ill-defined. We therefore established an ex vivo WAT organotypic culture system and demonstrated an upregulation of fibrosis-related genes and an increase of α-smooth muscle actin (αSMA) and fibronectin abundance upon dose-dependent stimulation with IL-13/IL-4. These fibrotic effects were lost in WAT lacking il4ra, which encodes for the underlying receptor controlling this process. Adipose tissue macrophages were found to play a key role in mediating IL-13/IL-4 effects in WAT fibrosis as their depletion through clodronate dramatically decreased the fibrotic phenotype. IL-4-induced WAT fibrosis was partly confirmed in mice injected intraperitoneally with IL-4. Furthermore, gene correlation analyses of human WAT samples revealed a strong positive correlation of fibrosis markers with IL-13/IL-4 receptors, whereas IL13 and IL4 correlations failed to confirm this association. In conclusion, IL-13 and IL-4 can induce WAT fibrosis ex vivo and partly in vivo, but their role in human WAT remains to be further elucidated.

Screening for genes, miRNAs and transcription factors of adipogenic differentiation and dedifferentiation of mesenchymal stem cells

BACKGROUND

The purpose of present study was to reveal the molecular mechanisms responsible for both adipogenic differentiation and dedifferentiation of mesenchymal stem cells (MSCs).

METHODS

Microarray data GSE36923 were obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between adipogenically differentiated cells vs undifferentiated bone marrow-derived MSCs, adipogenically differentiated cells vs dedifferentiated cells samples at day 7 and adipogenically differentiated cells vs dedifferentiated cells samples at day 35 were screened, and overlapped DEGs across the three groups were analyzed. The underlying functions of the upregulated and downregulated DEGs were investigated by Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis. The protein-protein interaction network was constructed, and hub genes were obtained subsequently. Hub genes were verified with GSE113253 dataset, and then miRNA-gene network and TF-gene network were constructed.

RESULTS

A total of 284 upregulated DEGs and 376 downregulated DEGs overlapped across the three groups. PPAR signaling pathway, AMPK signaling pathway, insulin signaling pathway, carbon metabolism, pyruvate metabolism, fatty acid metabolism, regulation of lipolysis in adipocytes, biosynthesis of amino acids, citrate cycle (TCA cycle) and 2-Oxocarboxylic acid metabolism were the top 10 pathways involving in the upregulated DEGs, and graft-versus-host disease, allograft rejection, viral myocarditis, cell adhesion molecules, phagosome, type I diabetes mellitus, antigen processing and presentation, autoimmune thyroid disease, intestinal immune network for IgA production and rheumatoid arthritis were the top 10 pathways in downregulated DEGs. After validation, the 8 hub genes were IL6, PPARG, CCL2, FASN, CEBPA, ADIPOQ, FABP4 and LIPE. Ten key miRNAs were hsa-mir-27a-3p, hsa-mir-182-5p, hsa-mir-7-5p, hsa-mir-16-5p, hsa-mir-1-3p, hsa-mir-155-5p, hsa-mir-21-3p, hsa-mir-34a-5p, hsa-mir-27a-5p and hsa-mir-30c-5p, and 10 key TFs were TFDP1, GTF2A2, ZNF584, NRF1, ZNF512, NFRKB, CEBPG, KLF16, GLIS2 and MXD4.

CONCLUSION

Our study constructed miRNA-gene network and TF-gene network involved in both adipogenic differentiation and dedifferentiation of MSCs, contributing to enhancing the efficiency of MSCs transplantation in soft tissue defect repair and developing more potent remedies for adipogenesis-related skeletal disorders.

Ceiling culture chip reveals dynamic lipid droplet transport during adipocyte dedifferentiation via actin remodeling

Adipocyte dedifferentiation has recently gained attention as a process underpinning adipocyte plasticity; however, a lack of suitable experimental platforms has hampered studies into the underlying mechanisms. Here, we developed a microscope-mountable ceiling culture chip that provides a stable yet tunable culture environment for long-term live-imaging of dedifferentiating adipocytes. A detailed spatiotemporal analysis of mature adipocyte dedifferentiation utilizing the culture platform and Cre-recombinase tracers revealed the involvement of dynamic actin remodeling for lipid droplet (LD) secretion during adipocyte dedifferentiation. Additionally, Hippo, Hedgehog, and PPARγ signaling pathways were identified as potent regulators of adipocyte dedifferentiation. Contrary to the belief that adult adipocytes are relatively static, we show that adipocytes are very dynamic, relying on actin-driven mechanical forces to execute LD extrusion and intercellular LD transfer processes.

Potential key factors involved in regulating adipocyte dedifferentiation

Adipocytes are the key constituents of adipose tissue, and their de-differentiation process has been widely observed in physiological and pathological conditions. For obese people, the promotion of adipocyte de-differentiation or maintenance of an undifferentiated state of adipocytes may help to improve their metabolic condition. Thus, understanding the regulatory mechanisms of adipocyte de-differentiation is necessary for treating metabolic diseases. Attractively, in addition to intracellular signals regulating adipocyte de-differentiation, external factors such as temperature and pressure also affect adipocyte de-differentiation. In this review, we summarize the recent progress in the field and discuss the regulatory roles and mechanisms of involved endogenous and exogenous factors during the process of de-differentiation.

Role of the extracellular matrix and YAP/TAZ in cell reprogramming

Stem cells are crucial in the fields of regenerative medicine and cell therapy. Mechanical signals from the cellular microenvironment play an important role in inducing the reprogramming of somatic cells into stem cells in vitro, but the mechanisms of this process have yet to be fully explored. Mechanical signals may activate a physical pathway involving the focal adhesions-cytoskeleton-LINC complex axis, and a chemical pathway involving YAP/TAZ. ENH protein likely plays an important role in connecting and regulating these two pathways. Such mechanisms illustrate one way in which mechanical signals from the cellular microenvironment can induce reprogramming of somatic cells to stem cells, and lays the foundation for a new strategy for inducing and regulating such reprogramming in vitro by means of physical processes related to local mechanical forces.

Standardization and characterization of adipose-derived stromal vascular fraction from New Zealand white rabbits for bone tissue engineering

Background and Aim:

Adipose tissue-derived stromal vascular fraction (SVF) contains a heterogeneous cell population comprising multipotent adipose-derived stem cells. Regenerative therapy using adipose-derived SVF has broad applications in bone tissue engineering due to the superior osteogenic potential of SVF. This study was designed to standardize and characterize adipose-derived SVF obtained from New Zealand white rabbits for bone tissue engineering and other potential applications.

Materials and Methods:

Ten skeletally mature and clinically healthy adult New Zealand white rabbits were used in this study. The SVF was prepared using surgically resected interscapular adipose tissue following enzymatic digestion with 0.1% collagenase type I solution. The SVF pellet obtained after the final centrifugation step was suspended in a 0.5 mL control solution to obtain ready-to-use adipose-derived SVF. The freshly prepared SVF was characterized based on the total SVF cell count and cell yield per gram of adipose tissue. The SVF cells were enumerated using a hemocytometer.

Results:

Interscapular adipose tissue depots are ideal for preparing autologous adipose-derived SVF due to the ease of access. The interscapular adipose-derived SVF prepared by enzymatic digestion had an average cell yield of 3.15±0.09×10⁶ cells/g adipose tissue. Freshly prepared SVF had a total cell count of 3.15±0.09×10⁴ cells/μL.

Conclusion:

The enzymatic digestion of adipose tissue using 0.1% collagenase resulted in better cell yield per gram than methods previously reported in rabbits. The use of adipose-derived SVF can preclude the requirement for an additional culture period. In addition, it may also reduce the risk of extensive cell contamination, which makes it a safe and cost-effective strategy for bone tissue engineering applications.

Inhibition of BRAF Sensitizes Thyroid Carcinoma to Immunotherapy by Enhancing tsMHCII-mediated Immune Recognition

CONTEXT

Multiple mechanisms play roles in restricting the ability of T-cells to recognize and eliminate tumor cells.

OBJECTIVE

To identify immune escape mechanisms involved in papillary thyroid carcinoma (PTC) to optimize immunotherapy.

SETTING AND DESIGN

iTRAQ analysis was conducted to identify proteins differentially expressed in PTC samples with or without BRAFV600E mutation. Molecular mechanisms regulating tumor cell evasion were investigated by in vitro modulations of BRAF/MAPK and related pathways. The pathological significance of identified tumor-specific major histocompatibility complex class II (tsMHCII) molecules in mediating tumor cell immune escape and targeted immune therapy was further evaluated in a transgenic mouse model of spontaneous thyroid cancer.

RESULTS

Proteomic analysis showed that tsMHCII level was significantly lower in BRAFV600E-associated PTCs and negatively correlated with BRAF mutation status. Constitutive activation of BRAF decreased tsMHCII surface expression on tumor cells, which inhibited activation of CD4+ T-cells and led to immune escape. Pathway analysis indicated that the transforming growth factor (TGF)-β1/SMAD3-mediated repression of tsMHCII, which could be reversed by BRAF inhibition (BRAFi). Targeting this pathway with a combined therapy of BRAF inhibitor PLX4032 and anti-PD-1 antibody efficiently blocked tumor growth by increasing CD4+ T-cell infiltration in a transgenic PTC mouse model.

CONCLUSIONS

Our results suggest that BRAFV600E mutation in PTC impairs the expression of tsMHCII through the TGF-β1/SMAD3 pathway to enhance immune escape. Combined treatment with PLX4032 and anti-PD-1 antibody promotes recognition and elimination of PTC by the immune system in a pre-clinical mouse model, and therefore offers an effective therapeutic strategy for patients with advanced PTC.

COL6A3 expression in adipose tissue cells is associated with levels of the homeobox transcription factor PRRX1

Fibrillar collagen COL6α3 in adipose tissue has been associated with obesity, inflammation, insulin resistance and cancer. We here aimed to identify novel transcriptional regulators of COL6A3 expression. Based on a transcriptome dataset of adipose tissue, we identified strong correlations for 56 genes with COL6A3 mRNA, including targets of TGF-β/SMAD signaling. Among the identified candidates, the homeobox transcription factor PRRX1 showed a particularly striking co-expression with COL6A3, validated across several different cohorts, including patients with extreme obesity, insulin sensitive and resistant obesity (subcutaneous and omental), after profound fat loss (subcutaneous), and lean controls (subcutaneous). In human and mouse adipose cells, PRRX1 knockdown reduced COL6A3 mRNA and PRRX1 overexpression transactivated a reporter construct with the endogenous human COL6A3 promoter. Stable PRRX1 overexpression in 3T3-L1 cells induced Col6a3 mRNA threefold specifically after adipogenic induction, whereas TGF-β1 treatment upregulated Col6a3 mRNA also in the preadipocyte state. Interestingly, pro-inflammatory stimulus (i.e., TNF-α treatment) decreased PRRX1-mediated Col6a3 transactivation and mRNA expression, supporting a role for this mechanism in the regulation of adipose tissue inflammation. In conclusion, we identified the homeobox factor PRRX1 as a novel transcriptional regulator associated with COL6A3 expression, providing new insight into the regulatory mechanisms of altered adipose tissue function in obesity and insulin resistance.

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.

Functional complexity of hair follicle stem cell niche and therapeutic targeting of niche dysfunction for hair regeneration

Stem cell activity is subject to non-cell-autonomous regulation from the local microenvironment, or niche. In adaption to varying physiological conditions and the ever-changing external environment, the stem cell niche has evolved with multifunctionality that enables stem cells to detect these changes and to communicate with remote cells/tissues to tailor their activity for organismal needs. The cyclic growth of hair follicles is powered by hair follicle stem cells (HFSCs). Using HFSCs as a model, we categorize niche cells into 3 functional modules, including signaling, sensing and message-relaying. Signaling modules, such as dermal papilla cells, immune cells and adipocytes, regulate HFSC activity through short-range cell-cell contact or paracrine effects. Macrophages capacitate the HFSC niche to sense tissue injury and mechanical cues and adipocytes seem to modulate HFSC activity in response to systemic nutritional states. Sympathetic nerves implement the message-relaying function by transmitting external light signals through an ipRGC-SCN-sympathetic circuit to facilitate hair regeneration. Hair growth can be disrupted by niche pathology, e.g. dysfunction of dermal papilla cells in androgenetic alopecia and influx of auto-reacting T cells in alopecia areata and lichen planopilaris. Understanding the functions and pathological changes of the HFSC niche can provide new insight for the treatment of hair loss.

Recent Advances in Understanding FOXN3 in Breast Cancer, and Other Malignancies

FOXN3 (forkhead box N3; CHES1: check point suppressor 1) belongs to the forkhead box (FOX) protein family. FOXN3 displays transcriptional inhibitory activity, and is involved in cell cycle regulation and tumorigenesis. FOXN3 is a tumor suppresser and alterations in FOXN3 are found in of a variety of cancers including melanoma, osteosarcoma, and hepatocellular carcinoma. While the roles of FOXN3 role in some cancers have been explored, its role in breast cancer remains unclear. Here we describe current state of knowledge of FOXN3 functions, and focus on its roles (known and potential) in breast cancer.

The Role of Immature and Mature Adipocytes in Hair Cycling

Hair follicles (HFs) strongly interact with adipocytes within the dermal white adipose tissue (dWAT), suggesting a strong physiological dependence on the content of immature and mature adipocytes in this layer. This content is regulated by the proliferation and differentiation of adipocyte precursors, as well as by dedifferentiation of mature existing adipocytes. Spatially, long-range interactions between HFs and dWAT involve the exchange of extracellular vesicles which are differentially released by precursors, preadipocytes, and mature adipocytes. Different exogenous factors, including light irradiation, are likely to modify the release of adipocyte-derived exosomes in dWAT, which can lead to aberrations of the HF cycle. Consequently, dWAT should be considered as a potential target for the modulation of hair growth.

Characterization and visualization of the liposecretion process taking place during ceiling culture of human mature adipocytes

OBJECTIVE

To investigate and further characterize the process of mature adipocyte dedifferentiation. Our hypothesis was that dedifferentiation does not involve mitosis but rather a phenomenon of liposecretion.

METHODS

Mature adipocytes were isolated by collagenase digestion of human adipose tissue samples. Ceiling cultures were established using our six-well plate model. Cells were treated with cytosine β-d-arabinofuranoside (AraC) or vincristine (VCR), two agents blocking cell division, and were compared with vehicle. Liposecretion events were visualized by time-lapse microscopy, with and without AraC in adipocytes transducted with a baculovirus. Microscopic analyses were performed after labeling phosphorylated histone 3 and cyclin B1 in ceiling cultures.

RESULTS

Treatment with AraC almost entirely prevented the formation of fibroblasts up to 12 days of ceiling culture. Similar results were obtained with VCR. The antimitotic effectiveness of the treatment was confirmed in fibroblast cultures from the adipose tissue stromal-vascular fraction by proliferation assays and colony-forming unit experiments. Using time-lapse microscopy, we visualized liposecretion events in which a large lipid droplet was rapidly secreted from isolated mature adipocytes. The same phenomenon was observed with AraC. This was observed in conjunction with histone 3 phosphorylation and cyclin B1 segregation to the nucleus.

CONCLUSION

Our results support the notion that dedifferentiation involves rapid secretion of the lipid droplet by the adipocytes with concomitant generation of fibroblast-like cells that subsequently proliferate to generate the dedifferentiated adipocyte population during ceiling culture. The presence of mitotic markers suggests that this process involves cell cycle progression, although cell division does not occur.