Adipose Stromal Cell Expansion and Exhaustion: Mechanisms and Consequences

Endothelial-specific telomerase inactivation causes telomere-independent cell senescence and multi-organ dysfunction characteristic of aging

It has remained unclear how aging of endothelial cells (EC) contributes to pathophysiology of individual organs. Cell senescence results in part from inactivation of telomerase (TERT). Here, we analyzed mice with Tert knockout specifically in EC. Tert loss in EC induced transcriptional changes indicative of senescence and tissue hypoxia in EC and in other cells. We demonstrate that EC-Tert-KO mice have leaky blood vessels. The blood-brain barrier of EC-Tert-KO mice is compromised, and their cognitive function is impaired. EC-Tert-KO mice display reduced muscle endurance and decreased expression of enzymes responsible for oxidative metabolism. Our data indicate that Tert-KO EC have reduced mitochondrial content and function, which results in increased dependence on glycolysis. Consistent with this, EC-Tert-KO mice have metabolism changes indicative of increased glucose utilization. In EC-Tert-KO mice, expedited telomere attrition is observed for EC of adipose tissue (AT), while brain and skeletal muscle EC have normal telomere length but still display features of senescence. Our data indicate that the loss of Tert causes EC senescence in part through a telomere length-independent mechanism undermining mitochondrial function. We conclude that EC-Tert-KO mice is a model of expedited vascular senescence recapitulating the hallmarks aging, which can be useful for developing revitalization therapies.

Intraoperative radiotherapy in breast cancer: Alterations to the tumor microenvironment and subsequent biological outcomes (Review)

Intraoperative radiotherapy (IORT) is a precise, single high‑dose irradiation directly targeting the tumor bed during surgery. In comparison with traditional external beam RT, it minimizes damage to other normal tissues, ensures an adequate dose to the tumor bed and results in improved cosmetic outcomes and quality of life. Furthermore, IORT offers a shorter treatment duration, lower economic costs and therapeutic efficacy comparable with traditional RT. However, its relatively higher local recurrence rate limits its further clinical applications. Identifying effective radiosensitizing drugs and rational RT protocols will improve its advantages. Furthermore, IORT may not only damage DNA to directly kill breast tumor cells but also alter the tumor microenvironment (TME) to exert a sustained antitumor effect. Specific doses of IORT may exert anti‑angiogenic effects, and consequently antitumor effects, by impacting post‑radiation peripheral blood levels of vascular endothelial growth factor and delta‑like 4. IORT may also modify the postoperative wound fluid composition to continuously inhibit tumor growth, e.g. by reducing components such as microRNA (miR)‑21, miR‑221, miR‑115, oncostatin M, TNF‑β, IL‑6 and IL‑8, and by elevating levels of components such as miR‑223, to inhibit the ability of postoperative wound fluid to induce proliferation, invasion and migration of residual cancer cells. IORT can also modify cancer cell glucose metabolism to inhibit the proliferation of residual tumor cells. In addition, IORT can induce a bystander effect, eliminating the postoperative wound fluid‑induced epithelial‑mesenchymal transition and tumor stem cell phenotype. Insights gained at the molecular level may provide new directions for identifying novel therapeutic targets and approaches. A more comprehensive understanding of the effects of IORT on the breast cancer (BC) TME may further its clinical application. Hence, the present article reviews the primary effects of IORT on BC and its impact on the TME, aiming to offer fresh research perspectives for relevant professionals.

The role of SPARC (secreted protein acidic and rich in cysteine) in the pathogenesis of obesity, type 2 diabetes, and non-alcoholic fatty liver disease

Secreted protein acidic and rich in cysteine (SPARC) is an extracellular matrix glycoprotein with pleiotropic functions, which is expressed in adipose, hepatic, muscular, and pancreatic tissue. Particularly, several studies demonstrated that SPARC is an important player in the context of obesity, diabetes, and fatty liver disease including advanced hepatic fibrosis and hepatocellular carcinoma. Evidence in murine and human samples indicates that SPARC is involved in adipogenesis, cellular metabolism, extracellular matrix modulation, glucose and lipid metabolism, among others. Furthermore, studies in SPARC knockout mouse model showed that SPARC contributes to adipose tissue formation, non-alcoholic fatty liver disease (NAFLD), and diabetes. Hence, SPARC may represent a novel and interesting target protein for future therapeutic interventions or a biomarker of disease progression. This review summarizes the role of SPARC in the pathophysiology of obesity, and extensively revised SPARC functions in physiological and pathological adipose tissue deposition, muscle metabolism, liver, and diabetes-related pathways.

Obesity and prostate cancer - microenvironmental roles of adipose tissue

Obesity is known to have important roles in driving prostate cancer aggressiveness and increased mortality. Multiple mechanisms have been postulated for these clinical observations, including effects of diet and lifestyle, systemic changes in energy balance and hormonal regulation and activation of signalling by growth factors and cytokines and other components of the immune system. Over the past decade, research on obesity has shifted towards investigating the role of peri-prostatic white adipose tissue as an important source of locally produced factors that stimulate prostate cancer progression. Cells that comprise white adipose tissue, the adipocytes and their progenitor adipose stromal cells (ASCs), which proliferate to accommodate white adipose tissue expansion in obesity, have been identified as important drivers of obesity-associated cancer progression. Accumulating evidence suggests that adipocytes are a source of lipids that are used by adjacent prostate cancer cells. However, results of preclinical studies indicate that ASCs promote tumour growth by remodelling extracellular matrix and supporting neovascularization, contributing to the recruitment of immunosuppressive cells, and inducing epithelial-mesenchymal transition through paracrine signalling. Because epithelial-mesenchymal transition is associated with cancer chemotherapy resistance and metastasis, ASCs are considered to be potential targets of therapies that could be developed to suppress cancer aggressiveness in patients with obesity.

Adipose Tissue Hyperplasia and Hypertrophy in Common and Syndromic Obesity-The Case of BBS Obesity

Obesity is a metabolic state generated by the expansion of adipose tissue. Adipose tissue expansion depends on the interplay between hyperplasia and hypertrophy, and is mainly regulated by a complex interaction between genetics and excess energy intake. However, the genetic regulation of adipose tissue expansion is yet to be fully understood. Obesity can be divided into common multifactorial/polygenic obesity and monogenic obesity, non-syndromic and syndromic. Several genes related to obesity were found through studies of monogenic non-syndromic obesity models. However, syndromic obesity, characterized by additional features other than obesity, suggesting a more global role of the mutant genes related to the syndrome and, thus, an additional peripheral influence on the development of obesity, were hardly studied to date in this regard. This review summarizes present knowledge regarding the hyperplasia and hypertrophy of adipocytes in common obesity. Additionally, we highlight the scarce research on syndromic obesity as a model for studying adipocyte hyperplasia and hypertrophy, focusing on Bardet-Biedl syndrome (BBS). BBS obesity involves central and peripheral mechanisms, with molecular and mechanistic alternation in adipocyte hyperplasia and hypertrophy. Thus, we argue that using syndromic obesity models, such as BBS, can further advance our knowledge regarding peripheral adipocyte regulation in obesity.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

miRNAs as cornerstones in adipogenesis and obesity

In recent decades, obesity has extensively emerged to the level of pandemics. It's significantly associated with serious co-morbidities that could decrease life quality and even life expectancy. Obesity has several determinants, such as age, sex, endocrine, and genetic factors. The miRNAs have emerged as genetic factors affecting obesity. The miRNAs are small noncoding nucleic acids that can modify gene expression and hence, control biological processes. The miRNAs can greatly affect many biological processes in obesity, such as adipogenesis, lipid metabolism, and homeostasis. As a result, the entry of miRNAs in obesity therapeutic approaches has been strongly advised as miRNAs mimics, inhibitors, and stimulators. Hence, this review aims to point out a summarized and updated overview of miRNAs and their roles in obesity and its included processes, such as adipogenesis and lipid metabolism. Besides, we also review recent applications of miRNAs as a treatment approach for obesity.

Role of bile acid receptor FXR in development and function of brown adipose tissue

Bile acids act as signalling molecules that contribute to maintenance of energy homeostasis in mice and humans. Activation of G-protein-coupled bile acid receptor TGR5 induces energy expenditure in brown adipose tissue (BAT). However, a role for the nuclear bile acid receptor Farnesoid X receptor (FXR) in BAT has remained ambiguous. We aimed to study the potential role of FXR in BAT development and functioning. Here we demonstrate low yet detectable expression of the α1/2 isoforms of FXR in murine BAT that markedly decreases upon cold exposure. Moderate adipose tissue-specific FXR overexpression in mice induces pronounced BAT whitening, presenting with large intracellular lipid droplets and extracellular collagen deposition. Expression of thermogenic marker genes including the target of Tgr5, Dio2, was significantly lower in BAT of chow-fed aP2-hFXR mice compared to wild-type controls. Transcriptomic analysis revealed marked up-regulation of extracellular matrix formation and down-regulation of mitochondrial functions in BAT from aP2-hFXR mice. In addition, markers of cell type lineages deriving from the dermomyotome, such as myocytes, as well as markers of cellular senescence were strongly induced. The response to cold and β3-adrenergic receptor agonism was blunted in these mice, yet resolved BAT whitening. Newborn cholestatic Cyp2c70^-/- mice with a human-like bile acid profile also showed distinct BAT whitening and upregulation of myocyte-specific genes, while thermogenic markers were down-regulated. Ucp1 expression inversely correlated with plasma bile acid levels. Therefore, bile acid signalling via FXR has a role in BAT function already early in tissue development. Functionally, FXR activation appears to oppose TGR5-mediated thermogenesis.

A Unified Model of Age-Related Cardiovascular Disease

Despite progress in biomedical technologies, cardiovascular disease remains the main cause of mortality. This is at least in part because current clinical interventions do not adequately take into account aging as a driver and are hence aimed at suboptimal targets. To achieve progress, consideration needs to be given to the role of cell aging in disease pathogenesis. We propose a model unifying the fundamental processes underlying most age-associated cardiovascular pathologies. According to this model, cell aging, leading to cell senescence, is responsible for tissue changes leading to age-related cardiovascular disease. This process, occurring due to telomerase inactivation and telomere attrition, affects all components of the cardiovascular system, including cardiomyocytes, vascular endothelial cells, smooth muscle cells, cardiac fibroblasts, and immune cells. The unified model offers insights into the relationship between upstream risk factors and downstream clinical outcomes and explains why interventions aimed at either of these components have limited success. Potential therapeutic approaches are considered based on this model. Because telomerase activity can prevent and reverse cell senescence, telomerase gene therapy is discussed as a promising intervention. Telomerase gene therapy and similar systems interventions based on the unified model are expected to be transformational in cardiovascular medicine.

Adipose-Derived Stem Cells, Obesity, and Inflammation: A Systematic Review and Implications for Osteoarthritis Treatment

ABSTRACT

Adipose is a known source of mesenchymal stem cells that can be used to treat musculoskeletal disorders, such as osteoarthritis. Because obesity often coexists with osteoarthritis, excess adiposity may be a useful source of mesenchymal stem cells. However, obesity is associated with systemic inflammation, which may influence the quality of adipose-derived stem cells. We performed a systematic review of the literature examining adipose-derived stem cell behavior, cytokine, and growth factor profiles from obese and nonobese patients. Two independent reviewers applied the inclusion/exclusion criteria and independently extracted data including mesenchymal stem cell count/viability/behavior, growth factor, and/or cytokine expression. Twenty-two articles met criteria for inclusion. Samples from obese patients had increased mesenchymal stem cell content (n = 6), but decreased proliferative ability (n = 3), and increased expression of interleukin 1 (n = 3), interleukin 6 (n = 3), and tumor necrosis factor α (n = 6). There was also greater macrophage content (n = 4). Weight loss normalized cellular function. In vitro behavior and quality of adipose-derived stem cell are significantly different between obese and nonobese patients. Samples from obese patients had greater adipose-derived stem cell content, lower proliferative ability, increased senescence, and increased proinflammatory cytokine expression. Differences in cellular function should be considered when using adipose to treat musculoskeletal pathology in obese and nonobese patients.

Transmissible Endoplasmic Reticulum Stress Mediated by Extracellular Vesicles from Adipocyte Promoting the Senescence of Adipose-Derived Mesenchymal Stem Cells in Hypertrophic Obesity

Hypertrophic obesity, characterized by an excessive expansion of subcutaneous adipocytes, causes chronic inflammation and insulin resistance. It is the primary feature of obesity in middle-aged and elderly individuals. In the adipose microenvironment, a high level of endoplasmic reticulum (ER) stress and changes in the extracellular vesicle (EV) composition of adipocytes may cause the senescence and restrained differentiation of progenitor cells of adipose, including adipose-derived mesenchymal stem cells (ASCs). In this study, a hypertrophic obesity mouse model was established, and the effects of adipocytes on the ER stress and senescence of ASCs were observed in a coculture of control ASCs and hypertrophic obesity mouse adipocytes or their derived EVs. The adipocytes of hypertrophic obesity mice were treated with GW4869 or an iron chelation agent to observe the effects of EVs secreted by adipocytes and their iron contents on the ER stress and senescence of ASCs. Results showed higher ER stress level and senescence phenotypes in the ASCs from the hypertrophic obesity mice than in those from the control mice. The ER stress, senescence phenotypes, and ferritin level of ASCs can be aggravated by the coculture of ASCs with adipocytes or EVs released by them from the hypertrophic obesity mice. GW4869 or iron chelator treatment improved the ER stress and senescence of the ASCs cocultured with EVs released by the adipocytes of the hypertrophic obesity mice. Our findings suggest that EV-mediated transmissible ER stress is responsible for the senescence of ASCs in hypertrophic obesity mice.

Dedifferentiation of Human Adipocytes After Fat Transplantation

BACKGROUND

Fat transplantation is a common method employed to treat soft-tissue defects. The dedifferentiation of mature adipocytes has been well documented, but whether it occurs after fat transplantation remains unclear.

OBJECTIVES

The major purpose of this project was to investigate the dedifferentiation of mature adipocytes after fat transplantation.

METHODS

Human lipoaspirate tissue was obtained from 6 female patients who underwent esthetic liposuction. Mature adipocytes were extracted and labeled with PKH26, mixed with lipoaspirate, and injected into nude mice. In addition, PKH26+ adipocytes were subjected to a ceiling culture. Grafted fat was harvested from nude mice, and stromal vascular fragment cells were isolated. The immunophenotype of PKH26+ cells was detected by flow cytometry analysis at 2 days and 1 week. The PKH26+ cells were sorted and counted at 2 and 4 weeks to verify their proliferation and multilineage differentiation abilities.

RESULTS

Two days after transplantation, almost no PKH26+ cells were found in the stromal vascular fragment cells. The PKH26+ cells found 1 week after transplantation showed a positive expression of cluster of differentiation (CD) 90 (CD90) and CD105 and a negative expression of CD45. This indicates that the labeled adipocytes were dedifferentiated. Its pluripotency was further demonstrated by fluorescent cell sorting and differentiation culture in vitro. In addition, the number of live PKH26+ cells at week 4 [(6.83 ± 1.67) × 104] was similar with that at week 2 [(7.11 ± 1.82) × 104].

CONCLUSIONS

Human mature adipocytes can dedifferentiate into stem cell-like cells in vivo after fat transplantation.

Nutrients and the Circadian Clock: A Partnership Controlling Adipose Tissue Function and Health

White adipose tissue (WAT) is a metabolic organ with flexibility to retract and expand based on energy storage and utilization needs, processes that are driven via the coordination of different cells within adipose tissue. WAT is comprised of mature adipocytes (MA) and cells of the stromal vascular cell fraction (SVF), which include adipose progenitor cells (APCs), adipose endothelial cells (AEC) and infiltrating immune cells. APCs have the ability to proliferate and undergo adipogenesis to form MA, the main constituents of WAT being predominantly composed of white, triglyceride-storing adipocytes with unilocular lipid droplets. While adiposity and adipose tissue health are controlled by diet and aging, the endogenous circadian (24-h) biological clock of the body is highly active in adipose tissue, from adipocyte progenitor cells to mature adipocytes, and may play a unique role in adipose tissue health and function. To some extent, 24-h rhythms in adipose tissue rely on rhythmic energy intake, but individual circadian clock proteins are also thought to be important for healthy fat. Here we discuss how and why the clock might be so important in this metabolic depot, and how temporal and qualitative aspects of energy intake play important roles in maintaining healthy fat throughout aging.

A Comparative Study on the Adipogenic Differentiation of Mesenchymal Stem/Stromal Cells in 2D and 3D Culture

Mesenchymal stem/stromal cells (MSC) are capable of renewing the progenitor cell fraction or differentiating in a tissue-specific manner. Adipogenic differentiation of adipose-tissue-derived MSC (adMSC) is important in various pathological processes. Adipocytes and their progenitors are metabolically active and secrete molecules (adipokines) that have both pro- and anti-inflammatory properties. Cell culturing in 2D is commonly used to study cellular responses, but the 2D environment does not reflect the structural situation for most cell types. Therefore, 3D culture systems have been developed to create an environment considered more physiological. Since knowledge about the effects of 3D cultivation on adipogenic differentiation is limited, we investigated its effects on adipogenic differentiation and adipokine release of adMSC (up to 28 days) and compared these with the effects in 2D. We demonstrated that cultivation conditions are crucial for cell behavior: in both 2D and 3D culture, adipogenic differentiation occurred only after specific stimulation. While the size and structure of adipogenically stimulated 3D spheroids remained stable during the experiment, the unstimulated spheroids showed signs of disintegration. Adipokine release was dependent on culture dimensionality; we found upregulated adiponectin and downregulated pro-inflammatory factors. Our findings are relevant for cell therapeutic applications of adMSC in complex, three-dimensionally arranged tissues.

The composition, function, and regulation of adipose stem and progenitor cells

White adipose tissue (WAT) is a highly plastic organ that plays a central role in regulating whole-body energy metabolism. Adipose stem and progenitor cells (ASPCs) are essential components of the stromal vascular fraction (SVF) of adipose tissue. They give rise to mature adipocytes and play a critical role in maintaining adipose tissue function. However, the molecular heterogeneity and functional diversity of ASPCs are still poorly understood. Recently, single-cell RNA sequencing (scRNA-seq) analysis has identified distinct subtypes of ASPCs in murine and human adipose tissues, providing new insights into the cellular complexity of ASPCs among multiple fat depots. This review summarizes the current knowledge on ASPC populations, including their markers, functions, and regulatory mechanisms. Targeting one or several of these cell populations may ameliorate metabolic disorders by promoting adaptive hyperplastic adipose growth.

Regulatory mechanisms of the early phase of white adipocyte differentiation: an overview

The adipose organ comprises two main fat depots termed white and brown adipose tissues. Adipogenesis is a process leading to newly differentiated adipocytes starting from precursor cells, which requires the contribution of many cellular activities at the genome, transcriptome, proteome, and metabolome levels. The adipogenic program is accomplished through two sequential phases; the first includes events favoring the commitment of adipose tissue stem cells/precursors to preadipocytes, while the second involves mechanisms that allow the achievement of full adipocyte differentiation. While there is a very large literature about the mechanisms involved in terminal adipogenesis, little is known about the first stage of this process. Growing interest in this field is due to the recent identification of adipose tissue precursors, which include a heterogenous cell population within different types of adipose tissue as well as within the same fat depot. In addition, the alteration of the heterogeneity of adipose tissue stem cells and of the mechanisms involved in their commitment have been linked to adipose tissue development defects and hence to the onset/progression of metabolic diseases, such as obesity. For this reason, the characterization of early adipogenic events is crucial to understand the etiology and the evolution of adipogenesis-related pathologies, and to explore the adipose tissue precursors’ potential as future tools for precision medicine.

Mesenchymal Stromal Cells: a Possible Reservoir for HIV-1?

The introduction of antiretroviral therapy (ART) and highly active antiretroviral therapy (HAART) has transformed human immunodeficiency virus (HIV)-1 into a chronic, well-managed disease. However, these therapies do not eliminate all infected cells from the body despite suppressing viral load. Viral rebound is largely due to the presence of cellular reservoirs which support long-term persistence of HIV-1. A thorough understanding of the HIV-1 reservoir will facilitate the development of new strategies leading to its detection, reduction, and elimination, ultimately leading to curative therapies for HIV-1. Although immune cells derived from lymphoid and myeloid progenitors have been thoroughly studied as HIV-1 reservoirs, few studies have examined whether mesenchymal stromal/stem cells (MSCs) can assume this function. In this review, we evaluate published studies which have assessed whether MSCs contribute to the HIV-1 reservoir. MSCs have been found to express the receptors and co-receptors required for HIV-1 entry, albeit at levels of expression and receptor localisation that vary considerably between studies. Exposure to HIV-1 and HIV-1 proteins alters MSC properties in vitro, including their proliferation capacity and differentiation potential. However, in vitro and in vivo experiments investigating whether MSCs can become infected with and harbour latent integrated proviral DNA are lacking. In conclusion, MSCs appear to have the potential to contribute to the HIV-1 reservoir. However, further studies are needed using techniques such as those used to prove that cluster of differentiation (CD)4⁺ T cells constitute an HIV-1 reservoir before a reservoir function can definitively be ascribed to MSCs.

Adipose-Derived Stem/Stromal Cells in Kidney Transplantation: Status Quo and Future Perspectives

Kidney transplantation (KT) is the gold standard treatment of end-stage renal disease. Despite progressive advances in organ preservation, surgical technique, intensive care, and immunosuppression, long-term allograft survival has not significantly improved. Among the many peri-operative complications that can jeopardize transplant outcomes, ischemia–reperfusion injury (IRI) deserves special consideration as it is associated with delayed graft function, acute rejection, and premature transplant loss. Over the years, several strategies have been proposed to mitigate the impact of IRI and favor tolerance, with rather disappointing results. There is mounting evidence that adipose stem/stromal cells (ASCs) possess specific characteristics that could help prevent, reduce, or reverse IRI. Immunomodulating and tolerogenic properties have also been suggested, thus leading to the development of ASC-based prophylactic and therapeutic strategies in pre-clinical and clinical models of renal IRI and allograft rejection. ASCs are copious, easy to harvest, and readily expandable in culture. Furthermore, ASCs can secrete extracellular vesicles (EV) which may act as powerful mediators of tissue repair and tolerance. In the present review, we discuss the current knowledge on the mechanisms of action and therapeutic opportunities offered by ASCs and ASC-derived EVs in the KT setting. Most relevant pre-clinical and clinical studies as well as actual limitations and future perspective are highlighted.

PTEN regulates adipose progenitor cell growth, differentiation, and replicative aging

The tumor suppressor phosphatase and tensin homolog (PTEN) negatively regulates the insulin signaling pathway. Germline PTEN pathogenic variants cause PTEN hamartoma tumor syndrome (PHTS), associated with lipoma development in children. Adipose progenitor cells (APCs) lose their capacity to differentiate into adipocytes during continuous culture, whereas APCs from lipomas of patients with PHTS retain their adipogenic potential over a prolonged period. It remains unclear which mechanisms trigger this aberrant adipose tissue growth. To investigate the role of PTEN in adipose tissue development, we performed functional assays and RNA-Seq of control and PTEN knockdown APCs. Reduction of PTEN levels using siRNA or CRISPR led to enhanced proliferation and differentiation of APCs. Forkhead box protein O1 (FOXO1) transcriptional activity is known to be regulated by insulin signaling, and FOXO1 was downregulated at the mRNA level while its inactivation through phosphorylation increased. FOXO1 phosphorylation initiates the expression of the lipogenesis-activating transcription factor sterol regulatory element-binding protein 1 (SREBP1). SREBP1 levels were higher after PTEN knockdown and may account for the observed enhanced adipogenesis. To validate this, we overexpressed constitutively active FOXO1 in PTEN CRISPR cells and found reduced adipogenesis, accompanied by SREBP1 downregulation. We observed that PTEN CRISPR cells showed less senescence compared with controls and the senescence marker CDKN1A (p21) was downregulated in PTEN knockdown cells. Cellular senescence was the most significantly enriched pathway found in RNA-Seq of PTEN knockdown versus control cells. These results provide evidence that PTEN is involved in the regulation of APC proliferation, differentiation, and senescence, thereby contributing to aberrant adipose tissue growth in patients with PHTS.

Adipose tissue and age‑dependent insulin resistance: New insights into WAT browning (Review)

Insulin resistance (IR) is defined as impaired insulin function, reduced glucose uptake and increased glucose production, which can result in type II diabetes, metabolic syndrome and even bone metabolic disorders. A possible reason for the increasing incidence of IR is population aging. Adipose tissue (AT) is an important endocrine organ that serves a crucial role in whole-body energy homeostasis. AT can be divided into white AT (WAT), beige AT and brown AT (BAT). Several mechanisms have been previously associated with age-dependent IR in WAT. However, BAT, a metabolically active tissue, controls the levels of plasma glucose and triglyceride metabolism. Therefore, the present review aimed to summarize the mechanisms of age-dependent IR induced by AT and to determine the role of WAT browning in achieving positive therapeutic outcomes in age-dependent IR.

Deciphering the Emerging Roles of Adipocytes and Adipose-Derived Stem Cells in Fat Transplantation

Autologous fat transplantation is widely regarded as an increasingly popular method for augmentation or reshaping applications in soft tissue defects. Although the fat transplantation is of simple applicability, low donor site morbidity and excellent biocompatibility, the clinical unpredictability and high resorption rates of the fat grafts remain an inevitable problem. In the sites of fat transplantation, the most essential components are the adipocyte and adipose-derived stem cells (ADSCs). The survival of adipocytes is the direct factor determining fat retention. The efficacy of fat transplantation is reduced by fat absorption and fibrosis due to the inadequate blood flow, adipocyte apoptosis and fat necrosis. ADSCs, a heterogeneous mixture of cells in adipose tissue, are closely related to tissue survival. ADSCs exhibit the ability of multilineage differentiation and remarkable paracrine activity, which is crucial for graft survival. This article will review the recent existing research on the mechanisms of adipocytes and ADSCs in fat transplantation, especially including adipocyte apoptosis, mature adipocyte dedifferentiation, adipocyte browning, ADSCs adipogenic differentiation and ADSCs angiogenesis. The in-depth understanding of the survival mechanism will be extremely valuable for achieving the desired filling effects.

Adipose Tissue-Derived Stem Cells: The Biologic Basis and Future Directions for Tissue Engineering

Mesenchymal stem cells (MSCs) have been isolated from a variety of tissues using different methods. Active research have confirmed that the most accessible site to collect them is the adipose tissue; which has a significantly higher concentration of MSCs. Moreover; harvesting from adipose tissue is less invasive; there are no ethical limitations and a lower risk of severe complications. These adipose-derived stem cells (ASCs) are also able to increase at higher rates and showing telomerase activity, which acts by maintaining the DNA stability during cell divisions. Adipose-derived stem cells secret molecules that show important function in other cells vitality and mechanisms associated with the immune system, central nervous system, the heart and several muscles. They release cytokines involved in pro/anti-inflammatory, angiogenic and hematopoietic processes. Adipose-derived stem cells also have immunosuppressive properties and have been reported to be "immune privileged" since they show negative or low expression of human leukocyte antigens. Translational medicine and basic research projects can take advantage of bioprinting. This technology allows precise control for both scaffolds and cells. The properties of cell adhesion, migration, maturation, proliferation, mimicry of cell microenvironment, and differentiation should be promoted by the printed biomaterial used in tissue engineering. Self-renewal and potency are presented by MSCs, which implies in an open-source for 3D bioprinting and regenerative medicine. Considering these features and necessities, ASCs can be applied in the designing of tissue engineering products. Understanding the heterogeneity of ASCs and optimizing their properties can contribute to making the best therapeutic use of these cells and opening new paths to make tissue engineering even more useful.

Evaluation of Fat Accumulation and Adipokine Production during the Long-Term Adipogenic Differentiation of Porcine Intramuscular Preadipocytes and Study of the Influence of Immunobiotics

The degree of fat accumulation and adipokine production are two major indicators of obesity that are correlated with increased adipose tissue mass and chronic inflammatory responses. Adipocytes have been considered effector cells for the inflammatory responses due to their capacity to express Toll-like receptors (TLRs). In this study, we evaluated the degree of fat accumulation and adipokine production in porcine intramuscular preadipocyte (PIP) cells maintained for in vitro differentiation over a long period without or with stimulation of either TNF-α or TLR2-, TLR3-, or TLR4-ligands. The cytosolic fat accumulation was measured by liquid chromatography and the expression of adipokines (CCL2, IL-6, IL-8 and IL-10) were quantified by RT-qPCR and ELISA at several time points (0 to 20 days) of PIP cells differentiation. Long-term adipogenic differentiation (LTAD) induced a progressive fat accumulation in the adipocytes over time. Activation of TLR3 and TLR4 resulted in an increased rate of fat accumulation into the adipocytes over the LTAD. The production of CCL2, IL-8 and IL-6 were significantly increased in unstimulated adipocytes during the LTAD, while IL-10 expression remained stable over the studied period. An increasing trend of adiponectin and leptin production was also observed during the LTAD. On the other hand, the stimulation of adipocytes with TLRs agonists or TNF-α resulted in an increasing trend of CCL2, IL-6 and IL-8 production while IL-10 remained stable in all four treatments during the LTAD. We also examined the influences of several immunoregulatory probiotic strains (immunobiotics) on the modulation of the fat accumulation and adipokine production using supernatants of immunobiotic-treated intestinal immune cells and the LTAD of PIP cells. Immunobiotics have shown a strain-specific ability to modulate the fat accumulation and adipokine production, and differentiation of adipocytes. Here, we expanded the utility and potential application of our in vitro PIP cells model by evaluating an LTAD period (20 days) in order to elucidate further insights of chronic inflammatory pathobiology of adipocytes associated with obesity as well as to explore the prospects of immunomodulatory intervention for obesity such as immunobiotics.