Obesity is associated with senescence of mesenchymal stromal cells derived from bone marrow, subcutaneous and visceral fat of young mice

Obesity-associated Inflammation and Alloimmunity

Obesity is a worldwide health problem with a rapidly rising incidence. In organ transplantation, increasing numbers of patients with obesity accumulate on waiting lists and undergo surgery. Obesity is in general conceptualized as a chronic inflammatory disease, potentially impacting alloimmune response and graft function. Here, we summarize our current understanding of cellular and molecular mechanisms that control obesity-associated adipose tissue inflammation and provide insights into mechanisms affecting transplant outcomes, emphasizing on the beneficial effects of weight loss on alloimmune responses.

Tissue-source effect on mesenchymal stem cells as living biodrugs for heart failure: Systematic review and meta-analysis

BACKGROUND

Mesenchymal stem cells (MSCs), as living biodrugs, have entered advanced phases of clinical assessment for cardiac function restoration in patients with myocardial infarction and heart failure. While MSCs are available from diverse tissue sources, bone-marrow-derived MSCs (BM-MSCs) remain the most well-studied cell type, besides umbilical-cord-derived MSCs (UC-MSCs). The latter offers advantages, including noninvasive availability without ethical considerations.

AIM

To compare the safety and efficacy of BM-MSCs and UC-MSCs in terms of left ventricular ejection fraction (LVEF), 6-min walking distance (6MWD), and major adverse cardiac events (MACEs).

METHODS

Five databases were systematically searched to identify randomized controlled trials (RCTs). Thirteen RCTs (693 patients) were included using predefined eligibility criteria. Weighted mean differences and odds ratio (OR) for the changes in the estimated treatment effects.

RESULTS

UC-MSCs significantly improved LVEF vs controls by 5.08% [95% confidence interval (CI): 2.20%-7.95%] at 6 mo and 2.78% (95%CI: 0.86%-4.70%) at 12 mo. However, no significant effect was observed for BM-MSCs vs controls. No significant changes were observed in the 6MWD with either of the two cell types. Also, no differences were observed for MACEs, except rehospitalization rates, which were lower only with BM-MSCs (odds ratio 0.48, 95%CI: 0.24-0.97) vs controls.

CONCLUSION

UC-MSCs significantly improved LVEF compared with BM-MSCs. Their advantageous characteristics position them as a promising alternative to MSC-based therapy.

Mesenchymal stem cells from adipose tissue prone to lose their stemness associated markers in obesity related stress conditions

Obesity is a health problem characterized by large expansion of adipose tissue. During this expansion, genotoxic stressors can be accumulated and negatively affect the mesenchymal stem cells (MSCs) of adipose tissue. Due to the oxidative stress generated by these genotoxic stressors, senescence phenotype might be observed in adipose tissue MSCs. Senescent MSCs lose their proliferations and differentiation properties and secrete senescence-associated molecules to their niche thus triggering senescence for the rest of the tissue. Accumulation of senescent cells in adipose tissue results in decreased tissue regeneration and functional impairment not only in the close vicinity but also in the other tissues. Here we hypothesized that declined tissue regeneration might be associated with loss of stemness markers in MSCs population. We analyzed the expression of several stemness-associated genes of in vitro cultured MSCs originated from adipose tissue of high-fat diet and normal diet mice models. Since the heterogenous MSCs population covers a small percentage of the pluripotent stem cells, which have roles in proliferation and tissue regeneration, we measured the percentage of these cells via TRA-1-60 pluripotent state antigen. Additionally, by conducting a shotgun proteomic approach using LC-MS/MS, whole cell proteome of the adipose tissue MSCs of high-fat diet and normal diet mice were analyzed and identified proteins were evaluated via gene ontology and PPI network analysis. MSCs of obese mice showed senescent phenotype and altered cell cycle distribution due to a hostile environment with oxidative stress in adipose tissue where they reside. Additionally, the number of pluripotent markers expressing cells declined in the MSC population of the high-fat diet mice. Gene expression analysis evidenced the loss of stemness with a decrease in the expression of stemness-associated genes. Of the proteomic comparison of the normal and the high-fat diet group, MSCs revealed that stemness-associated molecules were decreased while inflammation and senescence-associated phenotypes emerged in obese mice MSCs. Our results showed us that the MSCs of adipose tissue may lose their stemness properties due to obesity-associated stress conditions.

A nutrigeroscience approach: Dietary macronutrients and cellular senescence

Cellular senescence, a process in which a cell exits the cell cycle in response to stressors, is one of the hallmarks of aging. Senescence and the senescence-associated secretory phenotype (SASP)-a heterogeneous set of secreted factors that disrupt tissue homeostasis and promote the accumulation of senescent cells-reprogram metabolism and can lead to metabolic dysfunction. Dietary interventions have long been studied as methods to combat age-associated metabolic dysfunction, promote health, and increase lifespan. A growing body of literature suggests that senescence is responsive to diet, both to calories and specific dietary macronutrients, and that the metabolic benefits of dietary interventions may arise in part through reducing senescence. Here, we review what is currently known about dietary macronutrients' effect on senescence and the SASP, the nutrient-responsive molecular mechanisms that may mediate these effects, and the potential for these findings to inform the development of a nutrigeroscience approach to healthy aging.

Senescence of skeletal stem cells and their contribution to age-related bone loss

Human aging is linked to bone loss, resulting in bone fragility and an increased risk of fractures. This is primarily due to an age-related decline in the function of bone-forming osteoblastic cells and accelerated cellular senescence within the bone microenvironment. Here, we provide a detailed discussion of the hypothesis that age-related defective bone formation is caused by senescence of skeletal stem cells, as they are the main source of bone forming osteoblastic cells and influence the composition of bone microenvironment. Furthermore, this review discusses potential strategies to target cellular senescence as an emerging approach to treat age-related bone loss.

Obesity induces osteoimmunology imbalance: Molecular mechanisms and clinical implications

The notion that obesity can be a protective factor for bone health is a topic of ongoing debate. Increased body weight may have a positive impact on bone health due to its mechanical effects and the production of estrogen by adipose tissue. However, recent studies have found a higher risk of bone fracture and delayed bone healing in elderly obese patients, which may be attributed to the heightened risk of bone immune regulation disruption associated with obesity. The balanced functions of bone cells such as osteoclasts, osteoblasts, and osteocytes, would be subverted by aberrant and prolonged immune responses under obese conditions. This review aims to explore the intricate relationship between obesity and bone health from the perspective of osteoimmunology, elucidate the impact of disturbances in bone immune regulation on the functioning of bone cells, including osteoclasts, osteoblasts, and osteocytes, highlighting the deleterious effects of obesity on various diseases development such as rheumatoid arthritis (RA), osteoarthritis (AS), bone fracture, periodontitis. On the one hand, weight loss may achieve significant therapeutic effects on the aforementioned diseases. On the other hand, for patients who have difficulty in losing weight, the osteoimmunological therapies could potentially serve as a viable approach in halting the progression of these disease. Additional research in the field of osteoimmunology is necessary to ascertain the optimal equilibrium between body weight and bone health.

White adipocyte dysfunction and obesity-associated pathologies in humans

The prevalence of obesity and associated chronic diseases continues to increase worldwide, negatively impacting on societies and economies. Whereas the association between excess body weight and increased risk for developing a multitude of diseases is well established, the initiating mechanisms by which weight gain impairs our metabolic health remain surprisingly contested. In order to better address the myriad of disease states associated with obesity, it is essential to understand adipose tissue dysfunction and develop strategies for reinforcing adipocyte health. In this Review we outline the diverse physiological functions and pathological roles of human white adipocytes, examining our current knowledge of why white adipocytes are vital for systemic metabolic control, yet poorly adapted to our current obesogenic environment.

Effect of High BMI on Human Bone Marrow-Derived Mesenchymal Stromal Cells

Bone marrow-derived mesenchymal stromal cells (BMSCs) are attractive candidates in tissue engineering and regenerative medicine. Growing evidence has suggested that a high body mass index (BMI) can affect the properties of BMSCs, resulting in a reduced quality of the cells. However, the results are not consistent. Therefore, this study aimed to investigate the influences of high BMI on human BMSCs (hBMSCs). To avoid gender bias, BMSCs from females and males were studied independently. Finally, hBMSCs from 89 females and 152 males were separately divided into the normal BMI group (18.5 kg/m2 ≤ BMI < 25 kg/m2) and the high BMI group (BMI > 25 kg/m2). The cells were analyzed for the colony-forming potential; proliferation capacity; in vitro adipogenic, osteogenic, and chondrogenic differentiation potentials; and the expression of 32 common surface antigens. The results showed that high BMI did not change the number of colonies at passage 1 in females and males. In contrast, significantly reduced colony numbers at passage 4 (P4) were found in both female and male donors with high BMI. The doubling time of hBMSCs was comparable between the normal and the high BMI groups of females and males. Furthermore, the results of trilineage differentiation did not differ between the different BMI groups of males. In females, the high and the normal BMI groups also showed similar adipogenic and chondrogenic differentiation, while osteogenic differentiation was significantly enhanced in the high-BMI group. Regarding the expression of surface antigens, the expressions of CD200 and SSEA4 on hBMSCs were reduced in the high-BMI group of females and males, respectively. In conclusion, high BMI suppressed the clonogenicity of female and male hBMSCs at P4, improved the in vitro osteogenesis of female hBMSCs, and decreased the expressions of CD200 on hBMSCs in females and SSEA4 in males.

Adiponectin restores the obesity-induced impaired immunomodulatory function of mesenchymal stromal cells via glycolytic reprogramming

Obesity has been known to negatively modulate the life-span and immunosuppressive potential of mesenchymal stromal cells (MSC). However, it remains unclear what drives the compromised potency of obese MSC. In this study, we examined the involvement of adiponectin, an adipose tissue-derived hormone, in obesity-induced impaired therapeutic function of MSC. Diet-induced obesity leads to a decrease in serum adiponectin, accompanied by impairment of survival and immunomodulatory effects of adipose-derived MSC (ADSC). Interestingly, priming with globular adiponectin (gAcrp) improved the immunomodulatory potential of obese ADSC. Similar effects were also observed in lean ADSC. In addition, gAcrp potentiated the therapeutic effectiveness of ADSC in a mouse model of DSS-induced colitis. Mechanistically, while obesity inhibited the glycolytic capacity of MSC, gAcrp treatment induced a metabolic shift toward glycolysis through activation of adiponectin receptor type 1/p38 MAPK/hypoxia inducible factor-1α axis. These findings suggest that activation of adiponectin signaling is a promising strategy for enhancing the therapeutic efficacy of MSC against immune-mediated disorders.

Cellular microenvironment: a key for tuning mesenchymal stem cell senescence

Mesenchymal stem cells (MSCs) possess the ability to self-renew and differentiate into multiple cell types, making them highly suitable for use as seed cells in tissue engineering. These can be derived from various sources and have been found to play crucial roles in several physiological processes, such as tissue repair, immune regulation, and intercellular communication. However, the limited capacity for cell proliferation and the secretion of senescence-associated secreted phenotypes (SASPs) pose challenges for the clinical application of MSCs. In this review, we provide a comprehensive summary of the senescence characteristics of MSCs and examine the different features of cellular microenvironments studied thus far. Additionally, we discuss the mechanisms by which cellular microenvironments regulate the senescence process of MSCs, offering insights into preserving their functionality and enhancing their effectiveness.

Visceral fat and cardiometabolic future in children and adolescents: a critical update

Cardiovascular disease (CVD) is a process whose pathogenetic mechanisms start very early in life. Recently, the importance of visceral adipose tissue (VAT) has been highlighted in the development of CVD. VAT does not always depend on body mass index (BMI) and has been implicated in unfavorable metabolic activity and cardiovascular adverse events. Abnormally high deposition of VAT is associated with metabolic syndrome, obesity-associated phenotype, and cardiometabolic risk factors. Although the importance of visceral fat has not been studied broadly or extensively in long-term studies in children and adolescents, it appears that it does not have the same behavior as in adults, it is related to the appearance of cardiac risk factors. In adolescents, it plays a role in the pathogenesis of CVD that occur later in adulthood. Excess body weight and adiposity may lead to the development of early myocardial and pathological coronary changes in childhood. The purpose of this review is to summarize the risk factors, the clinical significance, and the prognostic role of visceral obesity in children and adolescents. In addition, extensive reference is made to the most commonly used techniques for the evaluation of VAT in clinical settings. IMPACT: Visceral obesity, plays an important role in cardiovascular health from very early in an individual's life. Visceral adipose tissue (VAT) distribution is not entirely related to body mass index (BMI) and provides additional prognostic information. There is a need to pay more attention to the assessment of VAT in young people, to develop methods that would go beyond the measurement of only BMI in clinical practice and to identify individuals with excess visceral adiposity and perhaps to monitor its changes.

Obesity drives adipose-derived stem cells into a senescent and dysfunctional phenotype associated with P38MAPK/NF-KB axis

BACKGROUND

Adipose-derived stem cells (ADSC) are multipotent cells implicated in tissue homeostasis. Obesity represents a chronic inflammatory disease associated with metabolic dysfunction and age-related mechanisms, with progressive accumulation of senescent cells and compromised ADSC function. In this study, we aimed to explore mechanisms associated with the inflammatory environment present in obesity in modulating ADSC to a senescent phenotype. We evaluated phenotypic and functional alterations through 18 days of treatment. ADSC were cultivated with a conditioned medium supplemented with a pool of plasma from eutrophic individuals (PE, n = 15) or with obesity (PO, n = 14), and compared to the control.

RESULTS

Our results showed that PO-treated ADSC exhibited decreased proliferative capacity with G2/M cycle arrest and CDKN1A (p21WAF1/Cip1) up-regulation. We also observed increased senescence-associated β-galactosidase (SA-β-gal) activity, which was positively correlated with TRF1 protein expression. After 18 days, ADSC treated with PO showed augmented CDKN2A (p16INK4A) expression, which was accompanied by a cumulative nuclear enlargement. After 10 days, ADSC treated with PO showed an increase in NF-κB phosphorylation, while PE and PO showed an increase in p38MAPK activation. PE and PO treatment also induced an increase in senescence-associated secretory phenotype (SASP) cytokines IL-6 and IL-8. PO-treated cells exhibited decreased metabolic activity, reduced oxygen consumption related to basal respiration, increased mitochondrial depolarization and biomass, and mitochondrial network remodeling, with no superoxide overproduction. Finally, we observed an accumulation of lipid droplets in PO-treated ADSC, implying an adaptive cellular mechanism induced by the obesogenic stimuli.

CONCLUSIONS

Taken together, our data suggest that the inflammatory environment observed in obesity induces a senescent phenotype associated with p38MAPK/NF-κB axis, which stimulates and amplifies the SASP and is associated with impaired mitochondrial homeostasis.

Mesenchymal Stem/Stromal Cells Therapy for Metabolic Syndrome: Potential Clinical Application?

Mesenchymal stem/stromal cells (MSCs), a class of cells with proliferative, immunomodulatory, and reparative functions, have shown therapeutic potential in a variety of systemic diseases, including metabolic syndrome (MetS). The cluster of morbidities that constitute MetS might be particularly amenable for the application of MSCs, which employ an arsenal of reparative actions to target multiple pathogenic pathways simultaneously. Preclinical studies have shown that MSCs can reverse pathological changes in MetS mainly by inhibiting inflammation, improving insulin resistance, regulating glycolipid metabolism, and protecting organ function. However, several challenges remain to overcome before MSCs can be applied for treating MetS. For example, the merits of autologous versus allogeneic MSCs sources remain unclear, particularly with autologous MSCs obtained from the noxious MetS milieu. The distinct characteristics and relative efficacy of MSCs harvested from different tissue sources also require clarification. Moreover, to improve the therapeutic efficacy of MSCs, investigators have explored several approaches that improved therapeutic efficacy but may involve potential safety concerns. This review summarized the potentially useful MSCs strategy for treating MetS, as well as some hurdles that remain to be overcome. In particular, larger-scale studies are needed to determine the therapeutic efficacy and safety of MSCs for clinical application.

Senescence of bone marrow mesenchymal stem cells in Wistar male rats receiving normal chow/high-calorie diets with/without vitamin D

Bone marrow mesenchymal stem cells (BM-MSCs) have a momentous function in the composition of the bone marrow microenvironment because of their many valuable properties and abilities, such as immunomodulation and hematopoiesis. The features and actions of MSCs are influenced by senescence, which may be affected by various factors such as nutritional/micronutrients status, e.g., vitamin D. This study aimed to examine the effects of a high-calorie diet (HCD) with/without vitamin D on BM-MSCs senescence. In the first phase, 48 middle-aged rats were fed a normal chow diet (NCD, n = 24) and an HCD (n = 24) for 26 weeks. Afterward, the rats in each group were randomly divided into three equal subgroups. Immediately, eight-rat from each diet group were sacrificed to assess the HCD effects on the first phase measurements. In the second phase, the remaining 4 groups of rats were fed either NCD or HCD with (6 IU/g) or without vitamin D (standard intake: 1 IU/g); in other words, in this phase, the animals were fed (a) NCD, (b) NCD plus vitamin D, (c) HCD, and (d) HCD plus vitamin D for 4 months. BM-MSCs were isolated and evaluated for P16INK4a, P38 MAPK, and Bmi-1 gene expression, reactive oxygen species (ROS) levels, SA-β-gal activity, and cell cycle profile at the end of both phases. After 26 weeks (first phase), the ROS level, SA-β-gal-positive cells, and cells in the G1 phase were significantly higher in HCD-fed rats than in NCD-fed ones (P < 0.05). HCD prescription did not significantly affect cells in the S and G2 phases (p > 0.05). Compared with the NCD-fed animals, P16INK4a and P38 MAPK gene expression were up-regulated in the HCD-fed animals; also, Bmi-1 gene expression was down-regulated (P < 0.05). BM-MSCs from vitamin D-treated rats (second phase) exhibited reduced mRNA levels of P16INK4a and P38 MAPK genes and increased Bmi-1 mRNA levels (all P < 0.05). Vitamin D prescription also declined the percentage of SA-β-gal-positive cells, ROS levels, and the cells in the G1 phase and increased the cells in the S phase in both NCD and HCD-fed animals (P < 0.05). The reduction of the cells in the G2 phase in rats fed with an NCD plus vitamin D was statistically non-significant (P = 0.128) and significant in HCD plus vitamin D rats (P = 0.002). HCD accelerates BM-MSCs senescence, and vitamin D reduces BM-MSCs senescence biomarkers.

The impact of cellular senescence in human adipose tissue

In the last decades the prevalence of obesity has increased dramatically, and the worldwide epidemic of obesity and related metabolic diseases has contributed to an increased interest for the adipose tissue (AT), the primary site for storage of lipids, as a metabolically dynamic and endocrine organ. Subcutaneous AT is the depot with the largest capacity to store excess energy and when its limit for storage is reached hypertrophic obesity, local inflammation, insulin resistance and ultimately type 2 diabetes (T2D) will develop. Hypertrophic AT is also associated with a dysfunctional adipogenesis, depending on the inability to recruit and differentiate new mature adipose cells. Lately, cellular senescence (CS), an aging mechanism defined as an irreversible growth arrest that occurs in response to various cellular stressors, such as telomere shortening, DNA damage and oxidative stress, has gained a lot of attention as a regulator of metabolic tissues and aging-associated conditions. The abundance of senescent cells increases not only with aging but also in hypertrophic obesity independent of age. Senescent AT is characterized by dysfunctional cells, increased inflammation, decreased insulin sensitivity and lipid storage. AT resident cells, such as progenitor cells (APC), non-proliferating mature cells and microvascular endothelial cells are affected with an increased senescence burden. Dysfunctional APC have both an impaired adipogenic and proliferative capacity. Interestingly, human mature adipose cells from obese hyperinsulinemic individuals have been shown to re-enter the cell cycle and senesce, which indicates an increased endoreplication. CS was also found to be more pronounced in mature cells from T2D individuals, compared to matched non-diabetic individuals, with decreased insulin sensitivity and adipogenic capacity. Factors associated with cellular senescence in human adipose tissue.

Increased cell senescence in human metabolic disorders

Cell senescence (CS) is at the nexus between aging and associated chronic disorders, and aging increases the burden of CS in all major metabolic tissues. However, CS is also increased in adult obesity, type 2 diabetes (T2D), and nonalcoholic fatty liver disease independent of aging. Senescent tissues are characterized by dysfunctional cells and increased inflammation, and both progenitor cells and mature, fully differentiated and nonproliferating cells are afflicted. Recent studies have shown that hyperinsulinemia and associated insulin resistance (IR) promote CS in both human adipose and liver cells. Similarly, increased CS promotes cellular IR, showing their interdependence. Furthermore, the increased adipose CS in T2D is independent of age, BMI, and degree of hyperinsulinemia, suggesting premature aging. These results suggest that senomorphic/senolytic therapy may become important for treating these common metabolic disorders.

Obesity and dyslipidemia are associated with partially reversible modifications to DNA hydroxymethylation of apoptosis- and senescence-related genes in swine adipose-derived mesenchymal stem/stromal cells

BACKGROUND

Obesity dysregulates key biological processes underlying the functional homeostasis, fate decisions, and reparative potential of mesenchymal stem/stromal cells (MSCs). Mechanisms directing obesity-induced phenotypic alterations in MSCs remain unclear, but emerging drivers include dynamic modification of epigenetic marks, like 5-hydroxymethylcytosine (5hmC). We hypothesized that obesity and cardiovascular risk factors induce functionally relevant, locus-specific changes in 5hmC of swine adipose-derived MSCs and evaluated their reversibility using an epigenetic modulator, vitamin-C.

METHODS

Female domestic pigs were fed a 16-week Lean or Obese diet (n = 6 each). MSCs were harvested from subcutaneous adipose tissue, and 5hmC profiles were examined through hydroxymethylated DNA immunoprecipitation sequencing (hMeDIP-seq) followed by an integrative (hMeDIP and mRNA sequencing) gene set enrichment analysis. For clinical context, we compared 5hmC profiles of adipose tissue-derived human MSCs harvested from patients with obesity and healthy controls.

RESULTS

hMeDIP-seq revealed 467 hyper- (fold change ≥ 1.4; p-value ≤ 0.05) and 591 hypo- (fold change ≤ 0.7; p-value ≤ 0.05) hydroxymethylated loci in swine Obese- versus Lean-MSCs. Integrative hMeDIP-seq/mRNA-seq analysis identified overlapping dysregulated gene sets and discrete differentially hydroxymethylated loci with functions related to apoptosis, cell proliferation, and senescence. These 5hmC changes were associated with increased senescence in cultured MSCs (p16/CDKN2A immunoreactivity, senescence-associated β-galactosidase [SA-β-Gal] staining), were partly reversed in swine Obese-MSCs treated with vitamin-C, and shared common pathways with 5hmC changes in human Obese-MSCs.

CONCLUSIONS

Obesity and dyslipidemia are associated with dysregulated DNA hydroxymethylation of apoptosis- and senescence-related genes in swine and human MSCs, potentially affecting cell vitality and regenerative functions. Vitamin-C may mediate reprogramming of this altered epigenomic landscape, providing a potential strategy to improve the success of autologous MSC transplantation in obese patients.

CX3CR1hi macrophages sustain metabolic adaptation by relieving adipose-derived stem cell senescence in visceral adipose tissue

Adipose-derived stem cells (ASCs) drive healthy visceral adipose tissue (VAT) expansion via adipocyte hyperplasia. Obesity induces ASC senescence that causes VAT dysfunction and metabolic disorders. It is challenging to restrain this process by biological intervention, as mechanisms of controlling VAT ASC senescence remain unclear. We demonstrate that a population of CX3CR1^hi macrophages is maintained in mouse VAT during short-term energy surplus, which sustains ASCs by restraining their senescence, driving adaptive VAT expansion and metabolic health. Long-term overnutrition induces diminishment of CX3CR1^hi macrophages in mouse VAT accompanied by ASC senescence and exhaustion, while transferring CX3CR1^hi macrophages restores ASC reservoir and triggers VAT beiging to alleviate the metabolic maladaptation. Mechanistically, visceral ASCs attract macrophages via MCP-1 and shape their CX3CR1^hi phenotype via exosomes; these macrophages relieve ASC senescence by promoting the arginase1-eIF5A hypusination axis. These findings identify VAT CX3CR1^hi macrophages as ASC supporters and unravel their therapeutic potential for metabolic maladaptation to obesity.

Smoking Suppresses the Therapeutic Potential of Adipose Stem Cells in Crohn’s Disease Patients through Epigenetic Changes

Patients with Crohn’s disease (CD) who smoke are known to have a worse prognosis than never-smokers and a higher risk for post-surgical recurrence, whereas patients who quit smoking after surgery have significantly lower post-operative recurrence. The hypothesis was that smoking induces epigenetic changes that impair the capacity of adipose stem cells (ASCs) to suppress the immune system. It was also questioned whether this impairment remains in ex-smokers with CD. ASCs were isolated from non-smokers, smokers and ex-smokers with CD and their interactions with immune cells were studied. The ASCs from both smokers and ex-smokers promoted macrophage polarization to an M1 pro-inflammatory phenotype, were not able to inhibit T- and B-cell proliferation in vitro and enhanced the gene and protein expression of inflammatory markers including interleukin-1b. Genome-wide epigenetic analysis using two different bioinformatic approaches revealed significant changes in the methylation patterns of genes that are critical for wound healing, immune and metabolic response and p53-mediated DNA damage response in ASCs from smokers and ex-smokers with CD. In conclusion, cigarette smoking induces a pro-inflammatory epigenetic signature in ASCs that likely compromises their therapeutic potential.

Obesity and Wound Healing: Focus on Mesenchymal Stem Cells

Chronic wounds represent nowadays a major challenge for both clinicians and researchers in the regenerative setting. Obesity represents one of the major comorbidities in patients affected by chronic ulcers and therefore diverse studies aimed at assessing possible links between these two morbid conditions are currently ongoing. In particular, adipose tissue has recently been described as having metabolic and endocrine functions rather than serving as a mere fat storage deposit. In this setting, adipose-derived stem cells, a peculiar subset of mesenchymal stromal/stem cells (MSCs) located in adipose tissue, have been demonstrated to possess regenerative and immunological functions with a key role in regulating both adipocyte function and skin regeneration. The aim of the present review is to give an overview of the most recent findings on wound healing, with a special focus on adipose tissue biology and obesity.

Are the Properties of Bone Marrow-Derived Mesenchymal Stem Cells Influenced by Overweight and Obesity?

Bone marrow-derived mesenchymal stem cells (BMSCs) are promising candidates for cell-based therapies. Growing evidence has indicated that overweight/obesity can change the bone marrow microenvironment, which affects some properties of BMSCs. As the overweight/obese population rapidly increases, they will inevitably become a potential source of BMSCs for clinical application, especially when receiving autologous BMSC transplantation. Given this situation, the quality control of these cells has become particularly important. Therefore, it is urgent to characterize BMSCs isolated from overweight/obese bone marrow environments. In this review, we summarize the evidence of the effects of overweight/obesity on the biological properties of BMSCs derived from humans and animals, including proliferation, clonogenicity, surface antigen expression, senescence, apoptosis, and trilineage differentiation, as well as the underlying mechanisms. Overall, the conclusions of existing studies are not consistent. Most studies demonstrate that overweight/obesity can influence one or more characteristics of BMSCs, while the involved mechanisms are still unclear. Moreover, insufficient evidence proves that weight loss or other interventions can rescue these qualities to baseline status. Thus, further research should address these issues and prioritize developing methods to improve functions of overweight- or obesity-derived BMSCs.

Adipokines at the crossroads of obesity and mesenchymal stem cell therapy

Mesenchymal stem cell (MSC) therapy is an emerging treatment strategy to counteract metabolic syndromes, including obesity and its comorbid disorders. However, its effectiveness is challenged by various factors in the obese environment that negatively impact MSC survival and function. The identification of these detrimental factors will provide opportunities to optimize MSC therapy for the treatment of obesity and its comorbidities. Dysregulated production of adipokines, a group of cytokines and hormones derived from adipose tissue, has been postulated to play a pivotal role in the development of obesity-associated complications. Intriguingly, adipokines have also been implicated in the modulation of viability, self-renewal, proliferation, and other properties of MSC. However, the involvement of adipokine imbalance in impaired MSC functionality has not been completely understood. On the other hand, treatment of obese individuals with MSC can restore the serum adipokine profile, suggesting the bidirectionality of the adipokine-MSC relationship. In this review, we aim to discuss the current knowledge on the central role of adipokines in the crosstalk between obesity and MSC dysfunction. We also summarize recent advances in the use of MSC for the treatment of obesity-associated diseases to support the hypothesis that adipokines modulate the benefits of MSC therapy in obese patients.

Advances in In Vitro and In Vivo Bioreactor-Based Bone Generation for Craniofacial Tissue Engineering

Craniofacial reconstruction requires robust bone of specified geometry for the repair to be both functional and aesthetic. While native bone from elsewhere in the body can be harvested, shaped, and implanted within a defect, using either an in vitro or in vivo bioreactors eliminates donor site morbidity while increasing the customizability of the generated tissue. In vitro bioreactors utilize cells harvested from the patient, a scaffold, and a device to increase mass transfer of nutrients, oxygen, and waste, allowing for generation of larger viable tissues. In vivo bioreactors utilize the patient's own body as a source of cells and of nutrient transfer and involve the implantation of a scaffold with or without growth factors adjacent to vasculature, followed by the eventual transfer of vascularized, mineralized tissue to the defect site. Several different models of in vitro bioreactors exist, and several different implantation sites have been successfully utilized for in vivo tissue generation and defect repair in humans. In this review, we discuss the specifics of each bioreactor strategy, as well as the advantages and disadvantages of each and the future directions for the engineering of bony tissues for craniofacial defect repair.

Cellular Senescence in Obesity and Associated Complications: a New Therapeutic Target

PURPOSE OF REVIEW

Obesity has increased worldwide recently and represents a major global health challenge. This review focuses on the obesity-associated cellular senescence in various organs and the role of these senescent cells (SnCs) in driving complications associated with obesity. Also, the ability to target SnCs pharmacologically with drugs termed senotherapeutics as a therapy for these complications is discussed.

RECENT FINDINGS

Several studies have shown a positive correlation between obesity and SnC burden in organs such as adipose tissue, liver, and pancreatic-β-cells. These SnCs produce several secretory factors which affect other cells and tissues in a paracrine manner resulting in organ dysfunction. The accumulation of SnCs in adipocytes affects their lipid storage and impairs adipogenesis. The inflammatory senescence-associated secretory phenotype (SASP) of SnCs downregulates the antioxidant capacity and mitochondrial function in tissues. Senescent hepatocytes cannot oxidize fatty acids, which leads to lipid deposition and senescence in β-cells decrease function. These and other adverse effects of SnCs contribute to insulin resistance and type-2 diabetes. The reduction in the SnC burden genetically or pharmacologically improves the complications associated with obesity. The accumulation of SnCs with age and disease accelerates aging. Obesity is a key driver of SnC accumulation, and the complications associated with obesity can be controlled by reducing the SnC burden. Thus, senotherapeutic drugs have the potential to be an effective therapeutic option.

Small Extracellular Vesicles from Inflamed Adipose Derived Stromal Cells Enhance the NF-κB-Dependent Inflammatory/Catabolic Environment of Osteoarthritis

The last decade has seen exponentially growing efforts to exploit the effects of adipose derived stromal cells (ADSC) in the treatment of a wide range of chronic degenerative diseases, including osteoarthritis (OA), the most prevalent joint disorder. In the perspective of developing a cell-free advanced therapy medicinal product, a focus has been recently addressed to the ADSC secretome that lends itself to an allogeneic use and can be further dissected for the selective purification of small extracellular vesicles (sEVs). sEVs can act as “biological drug carriers” to transfer information that mirror the pathophysiology of the providing cells. This is important in the clinical perspective where many OA patients are also affected by the metabolic syndrome (MetS). ADSC from MetS OA patients are dysfunctional and “inflammatory” primed within the adipose tissue. To mimic this condition, we exposed ADSC to IL-1β, and then we investigated the effects of the isolated sEVs on chondrocytes and synoviocytes, either cultured separately or in co-culture, to tease out the effects of these “IL-1β primed sEVs” on gene and protein expression of major inflammatory and catabolic OA markers. In comparison with sEVs isolated from unstimulated ADSC, the IL-1β primed sEVs were able to propagate NF-κB activation in bystander joint cells. The effects were more prominent on synoviocytes, possibly because of a higher expression of binding molecules such as CD44. These findings call upon a careful characterization of the “inflammatory fingerprint” of ADSC to avoid the transfer of an unwanted message as well as the development of in vitro “preconditioning” strategies able to rescue the antiinflammatory/anticatabolic potential of ADSC-derived sEVs.

HOXA5 inhibits adipocytes proliferation through transcriptional regulation of Ccne1 and blocking JAK2/STAT3 signaling pathway in mice

The highly regulated proliferation of adipocytes plays a momentous role in fat development and obesity. Hoxa5 is an important member of Hox family, its encoded protein is an important transcription factor related to development. And its differential expression in different adipose tissues seems to indicate that Hoxa5 may be involved in the regulation of adipocyte proliferation. In order to evaluate the regulation mechanism of Hoxa5 on adipocyte proliferation, we constructed a variety of Hoxa5 expression vectors in vivo and in vitro to explore its mechanism on adipocyte proliferation and its potential impact on obesity. We have observed that the overexpression of Hoxa5 strongly reduces cell counts, and Hoxa5 can inhibit cell proliferation and block cell cycle progression by regulating the expression of genes such as Cyclin E, Cycling D1 and p53. Most importantly, we demonstrated that Hoxa5 exerts its effect by regulating the signaling pathway of Janus kinase 2 (JAK2) signal transduction and transcription 3 (STAT3) activator, as well as binding to the promoter region of Ccne1 and inhibiting the transcription of Ccne1.This study provides an in-depth understanding of the potential molecular mechanism of Hoxa5 inhibiting adipocyte proliferation. Our results suggest the importance of Hoxa5 in the treatment of obesity.

Trappc9 Deficiency Impairs the Plasticity of Stem Cells

Genetic mutations of trappc9 cause intellectual disability with the atrophy of brain structures and variable obesity by poorly understood mechanisms. Trappc9-deficient mice develop phenotypes resembling pathological changes in humans and appear overweight shortly after weaning, and thus are useful for studying the pathogenesis of obesity. Here, we investigated the effects of trappc9 deficiency on the proliferation and differentiation capacity of adipose-derived stem cells (ASCs). We isolated ASCs from mice before overweight was developed and found that trappc9-null ASCs exhibited signs of premature senescence and cell death. While the lineage commitment was retained, trappc9-null ASCs preferred adipogenic differentiation. We observed a profound accumulation of lipid droplets in adipogenic cells derived from trappc9-deficient ASCs and marked differences in the distribution patterns and levels of calcium deposited in osteoblasts obtained from trappc9-null ASCs. Biochemical studies revealed that trappc9 deficiency resulted in an upregulated expression of rab1, rab11, and rab18, and agitated autophagy in ASCs. Moreover, we found that the content of neural stem cells in both the subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus vastly declined in trappc9-null mice. Collectively, our results suggest that obesity, as well as brain structure hypoplasia induced by the deficiency of trappc9, involves an impairment in the plasticity of stem cells.

Obesity Affects the Proliferative Potential of Equine Endometrial Progenitor Cells and Modulates Their Molecular Phenotype Associated with Mitochondrial Metabolism

The study aimed to investigate the influence of obesity on cellular features of equine endometrial progenitor cells (Eca EPCs), including viability, proliferation capacity, mitochondrial metabolism, and oxidative homeostasis. Eca EPCs derived from non-obese (non-OB) and obese (OB) mares were characterized by cellular phenotype and multipotency. Obesity-induced changes in the activity of Eca EPCs include the decline of their proliferative activity, clonogenic potential, mitochondrial metabolism, and enhanced oxidative stress. Eca EPCs isolated from obese mares were characterized by an increased occurrence of early apoptosis, loss of mitochondrial dynamics, and senescence-associated phenotype. Attenuated metabolism of Eca EPCs OB was related to increased expression of pro-apoptotic markers (CASP9, BAX, P53, P21), enhanced expression of OPN, PI3K, and AKT, simultaneously with decreased signaling stabilizing cellular homeostasis (including mitofusin, SIRT1, FOXP3). Obesity alters functional features and the self-renewal potential of endometrial progenitor cells. The impaired cytophysiology of progenitor cells from obese endometrium predicts lower regenerative capacity if used as autologous transplants.

Senotherapeutic-like effect of Silybum marianum flower extract revealed on human skin cells

Cellular senescence causes irreversible growth arrest of cells. Prolonged accumulation of senescent cells in tissues leads to increased detrimental effects due to senescence associated secretory phenotype (SASP). Recent findings suggest that elimination of senescent cells has a beneficial effect on organismal aging and lifespan. In this study, using a validated replicative senescent human dermal fibroblasts (HDFs) model, we showed that elimination of senescent cells is possible through the activation of an apoptotic mechanism. We have shown in this replicative senescence model, that cell senescence is associated with DNA damage and cell cycle arrest (p21, p53 markers). We have shown that Silybum marianum flower extract (SMFE) is a safe and selective senolytic agent targeting only senescent cells. The elimination of the cells is induced through the activation of apoptotic pathway confirmed by annexin V/propidium iodide and caspase-3/PARP staining. Moreover, SMFE suppresses the expression of SASP factors such as IL-6 and MMP-1 in senescent HDFs. In a co-culture model of senescent and young fibroblasts, we demonstrated that senescent cells impaired the proliferative capacities of young cells. Interestingly, when the co-culture is treated with SMFE, the cell proliferation rate of young cells is increased due to the decrease of the senescent burden. Moreover, we demonstrated in vitro that senescent fibroblasts trigger senescent process in normal keratinocytes through a paracrine effect. Indeed, the conditioned medium of senescent HDFs treated with SMFE reduced the level of senescence-associated beta-galactosidase (SA-β-Gal), p16INK4A and SASP factors in keratinocytes compared with CM of senescent HDFs. These results indicate that SMFE can prevent premature aging due to senescence and even reprograms aged skin. Indeed, thanks to its senolytic and senomorphic properties SMFE is a candidate for anti-senescence strategies.

Clinical Trials Based on Mesenchymal Stromal Cells are Exponentially Increasing: Where are We in Recent Years?

Mesenchymal stromal cells (MSCs), present in the stromal component of several tissues, include multipotent stem cells, progenitors, and differentiated cells. MSCs have quickly attracted considerable attention in the clinical field for their regenerative properties and their ability to promote tissue homeostasis following injury. In recent years, MSCs mainly isolated from bone marrow, adipose tissue, and umbilical cord—have been utilized in hundreds of clinical trials for the treatment of various diseases. However, in addition to some successes, MSC-based therapies have experienced several failures. The number of new trials with MSCs is exponentially growing; still, complete results are only available for a limited number of trials. This dearth does not help prevent potentially inefficacious and unnecessary clinical trials. Results from unsuccessful studies may be useful in planning new therapeutic approaches to improve clinical outcomes. In order to bolster critical analysis of trial results, we reviewed the state of art of MSC clinical trials that have been published in the last six years. Most of the 416 published trials evaluated MSCs’ effectiveness in treating cardiovascular diseases, GvHD, and brain and neurological disorders, although some trials sought to treat immune system diseases and wounds and to restore tissue. We also report some unorthodox clinical trials that include unusual studies.

Different Stages of Quiescence, Senescence, and Cell Stress Identified by Molecular Algorithm Based on the Expression of Ki67, RPS6, and Beta-Galactosidase Activity

During their life span, cells have two possible states: a non-cycling, quiescent state (G0) and a cycling, activated state. Cells may enter a reversible G0 state of quiescence or, alternatively, they may undergo an irreversible G0 state. The latter may be a physiological differentiation or, following a stress event, a senescent status. Discrimination among the several G0 states represents a significant investigation, since quiescence, differentiation, and senescence are progressive phenomena with intermediate transitional stages. We used the expression of Ki67, RPS6, and beta-galactosidase to identify healthy cells that progressively enter and leave quiescence through G0-entry, G0 and G0-alert states. We then evaluated how cells may enter senescence following a genotoxic stressful event. We identified an initial stress stage with the expression of beta-galactosidase and Ki67 proliferation marker. Cells may recover from stress events or become senescent passing through early and late senescence states. Discrimination between quiescence and senescence was based on the expression of RPS6, a marker of active protein synthesis that is present in senescent cells but absent in quiescent cells. Even taking into account that fixed G0 states do not exist, our molecular algorithm may represent a method for identifying turning points of G0 transitional states that continuously change.

Obesity induced by high-fat diet is associated with critical changes in biological and molecular functions of mesenchymal stromal cells present in visceral adipose tissue

The mesenchymal stromal cells (MSCs) residing within the stromal component of visceral adipose tissue appear to be greatly affected by obesity, with impairment of their functions and presence of senescence. To gain further insight into these phenomena, we analyzed the changes in total proteome content and secretome of mouse MSCs after a high-fat diet (HFD) treatment compared to a normal diet (ND). In healthy conditions, MSCs are endowed with functions mainly devoted to vesicle trafficking. These cells have an immunoregulatory role, affecting leukocyte activation and migration, acute inflammation phase response, chemokine signaling, and platelet activities. They also present a robust response to stress. We identified four signaling pathways (TGF-β, VEGFR2, HMGB1, and Leptin) that appear to govern the cells' functions. In the obese mice, MSCs showed a change in their functions. The immunoregulation shifted toward pro-inflammatory tasks with the activation of interleukin-1 pathway and of Granzyme A signaling. Moreover, the methionine degradation pathway and the processing of capped intronless pre-mRNAs may be related to the inflammation process. The signaling pathways we identified in ND MSCs were replaced by MET, WNT, and FGFR2 signal transduction, which may play a role in promoting inflammation, cancer, and aging.