High glucose-induced reactive oxygen species generation promotes stemness in human adipose-derived stem cells

Vaspin facilitates the proliferation and osteogenic differentiation of periodontal ligament stem cells

OBJECTIVE

To investigate whether visceral adipose tissue-derived serine protease inhibitor (vaspin) can alleviate the inhibitory effect of high-glucose (HG) culture on the proliferation and osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) and to preliminarily explore the underlying mechanisms.

BACKGROUND

High glucose produces damage to the regeneration of periodontal tissue of PDLSCs. The expression level of vaspin in periodontal tissue is high in periodontitis patients and effectively reduced after initial therapy of periodontal diseases. However, the effect of vaspin on PDLSCs remains unknown.

MATERIALS AND METHODS

PDLSCs were cultured in media augmented with 5.5 or 25.0 mM concentrations of glucose to elucidate the impact and mechanism of vaspin on PDLSCs under high glucose in vitro. Proliferation was measured by Cell Counting Kit-8 (CCK8) assay. Osteogenesis of PDLSCs was assessed by alkaline phosphatase (ALP) staining, ALP activity, and Alizarin Red staining. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot (WB) were used to investigate the osteo-specific markers. Then, the molecular impact of vaspin in the presence/absence of HG on PDLSCs physiology was determined with TGF-β1/Smad signaling pathway as the main focus.

RESULTS

It was revealed that the proliferation and osteogenic differentiation (OD) of PDLSCs under HG was reduced, and by adding vaspin the anti-osteogenic impact of HG was relieved. Moreover, vaspin enhanced TGF-β1/Smad signaling pathway activity. Pretreatment with TGF-β1 inhibitor blocked vaspin-triggered TGF-β1/Smad signal activation and minimized the vaspin-induced protective effect against HG-inhibited growth and OD.

CONCLUSIONS

In summary, vaspin observably reduces HG-mediated inhibition of PDLSCs OD by modulating the TGF-β1/Smad signaling pathway. Vaspin may be a potential therapeutic for periodontal tissue regeneration in diabetic patients.

Human platelet lysate-cultured adipose-derived stem cell sheets promote angiogenesis and accelerate wound healing via CCL5 modulation

BACKGROUND

A rising population faces challenges with healing-impaired cutaneous wounds, often leading to physical disabilities. Adipose-derived stem cells (ASCs), specifically in the cell sheet format, have emerged as a promising remedy for impaired wound healing. Human platelet lysate (HPL) provides an attractive alternative to fetal bovine serum (FBS) for culturing clinical-grade ASCs. However, the potential of HPL sheets in promoting wound healing has not been fully investigated. This study aimed to explore the anti-fibrotic and pro-angiogenic capabilities of HPL-cultured ASC sheets and delve into the molecular mechanism.

METHODS

A rat burn model was utilized to evaluate the efficacy of HPL-cultured ASC sheets in promoting wound healing. ASC sheets were fabricated with HPL, and those with FBS were included for comparison. Various analyses were conducted to assess the impact of HPL sheets on wound healing. Histological examination of wound tissues provided insights into aspects such as wound closure, collagen deposition, and overall tissue regeneration. Immunofluorescence was employed to assess the presence and distribution of transplanted ASCs after treatment. Further in vitro studies were conducted to decipher the specific factors in HPL sheets contributing to angiogenesis.

RESULTS

HPL-cultured ASC sheets significantly accelerated wound closure, fostering ample and organized collagen deposition in the neo-dermis. Significantly more retained ASCs were observed in wound tissues treated with HPL sheets compared to the FBS counterparts. Moreover, HPL sheets mitigated macrophage recruitment and decreased subsequent wound tissue fibrosis in vivo. Immunohistochemistry also indicated enhanced angiogenesis in the HPL sheet group. The in vitro analyses showed upregulation of C-C motif chemokine ligand 5 (CCL5) and angiogenin in HPL sheets, including both gene expression and protein secretion. Culturing endothelial cells in the conditioned media compared to media supplemented with CCL5 or angiogenin suggested a correlation between CCL5 and the pro-angiogenic effect of HPL sheets. Additionally, through neutralizing antibody experiments, we further validated the crucial role of CCL5 in HPL sheet-mediated angiogenesis in vitro.

CONCLUSIONS

The present study underscores CCL5 as an essential factor in the pro-angiogenic effect of HPL-cultured ASC sheets during the wound healing process. These findings highlight the potential of HPL-cultured ASC sheets as a promising therapeutic option for healing-impaired cutaneous wounds in clinical settings. Furthermore, the mechanism exploration yields valuable information for optimizing regenerative strategies with ASC products.

BRIEF ACKNOWLEDGMENT

This research was supported by the National Science and Technology Council, Taiwan (NSTC112-2321-B-002-018), National Taiwan University Hospital (111C-007), and E-Da Hospital-National Taiwan University Hospital Joint Research Program (111-EDN0001, 112-EDN0002).

GKT137831 in combination with adipose-derived stem cells alleviates high glucose-induced inflammaging and improves diabetic wound healing

Adipose-derived stem cells (ADSCs) have been proven to promote healing in diabetic wounds, which are one of the most serious chronic refractory wounds. However, reactive oxygen species (ROS) induced by high glucose (HG) lead to oxidative stress and aging in ADSCs, which limits the therapeutic effect of ADSCs. In this study, we investigated the role of GKT137831, a NOX1/4 inhibitor that can reduce ROS production, in protecting ADSCs from hyperglycemia and in diabetic wound healing. In vitro, ROS levels and NOX4 expression were increased after HG treatment of ADSCs, while the oxidative stress marker malondialdehyde was increased; mitochondrial membrane potential was decreased; inflammatory aging-related indicators such as p16, p21, matrix metalloproteinase-1 (MMP1), MMP3, interleukin-6, and β-galactosidase were increased; and migration was weakened. In vivo, we constructed a diabetic mouse wound model and found that the combination of ADSCs and GKT137831 synergistically promoted the 21-day wound healing rate, increased the expression of collagen and hydroxyproline, increased the number of blood vessels and the expression of CD31, and reduced the expression of interleukin-6, MMP1, MMP3, and p21. These results suggest that GKT137831 could protect ADSCs from oxidative stress and aging induced by HG and enhance the therapeutic effect of ADSCs on diabetic wounds.

Enhancement of skin rejuvenation and hair growth through novel near-infrared light emitting diode (nNIR) lighting: in vitro and in vivo study

The study aimed to explore the impact of a novel near-infrared LED (nNIR) with an extended spectrum on skin enhancement and hair growth. Various LED sources, including White and nNIRs, were compared across multiple parameters: cytotoxicity, adenosine triphosphate (ATP) synthesis, reactive oxygen species (ROS) reduction, skin thickness, collagen synthesis, collagenase expression, and hair follicle growth. Experiments were conducted on human skin cells and animal models. Cytotoxicity, ATP synthesis, and ROS reduction were evaluated in human skin cells exposed to nNIRs and Whites. LED irradiation effects were also studied on a UV-induced photoaging mouse model, analyzing skin thickness, collagen synthesis, and collagenase expression. Hair growth promotion was examined as well. Results revealed both White and nNIR were non-cytotoxic to human skin cells. nNIR enhanced ATP and collagen synthesis while reducing ROS levels, outperforming the commonly used 2chip LEDs. In the UV-induced photoaging mouse model, nNIR irradiation led to reduced skin thickness, increased collagen synthesis, and lowered collagenase expression. Additionally, nNIR irradiation stimulated hair growth, augmented skin thickness, and increased hair follicle count. In conclusion, the study highlighted positive effects of White and nNIR irradiation on skin and hair growth. However, nNIR exhibited superior outcomes compared to White. Its advancements in ATP content, collagen synthesis, collagenase inhibition, and hair growth promotion imply increased ATP synthesis activity. These findings underscore nNIR therapy's potential as an innovative and effective approach for enhancing skin and promoting hair growth.

Excess dietary sugar impairs Drosophila adult stem cells via elevated reactive oxygen species-induced JNK signaling

High-sugar diets (HSDs) often lead to obesity and type 2 diabetes, both metabolic syndromes associated with stem cell dysfunction. However, it is unclear whether excess dietary sugar affects stem cells. Here, we report that HSD impairs stem cell function in the intestine and ovaries of female Drosophila prior to the onset of insulin resistance, a hallmark of type 2 diabetes. Although 1 week of HSD leads to obesity, impaired oogenesis and altered lipid metabolism, insulin resistance does not occur. HSD increases glucose uptake by germline stem cells (GSCs) and triggers reactive oxygen species-induced JNK signaling, which reduces GSC proliferation. Removal of excess sugar from the diet reverses these HSD-induced phenomena. A similar phenomenon is found in intestinal stem cells (ISCs), except that HSD disrupts ISC maintenance and differentiation. Interestingly, tumor-like GSCs and ISCs are less responsive to HSD, which may be because of their dependence on glycolytic metabolism and high energy demand, respectively. This study suggests that excess dietary sugar induces oxidative stress and damages stem cells before insulin resistance develops, a mechanism that may also occur in higher organisms.

Enhancing the therapeutic efficacy of mesenchymal stem cell transplantation in diabetes: Amelioration of mitochondrial dysfunction-induced senescence

Mesenchymal stem cell (MSC) transplantation offers significant potential for the treatment of diabetes mellitus (DM) and its complications. However, hyperglycemic conditions can induce senescence and dysfunction in both transplanted and resident MSCs, thereby limiting their therapeutic potential. Mitochondrial dysfunction and oxidative stress are key contributors to this process in MSCs exposed to hyperglycemia. As such, strategies aimed at mitigating mitochondrial dysfunction could enhance the therapeutic efficacy of MSC transplantation in DM. In this review, we provide an updated overview of how mitochondrial dysfunction mediates MSC senescence. We present experimental evidence for the molecular mechanisms behind high glucose-induced mitochondrial dysfunction in MSCs, which include impairment of mitochondrial biogenesis, mitochondrial calcium regulation, the mitochondrial antioxidant system, mitochondrial fusion-fission dynamics, mitophagy, and intercellular mitochondrial transfer. Furthermore, we propose potential pharmacological candidates that could improve the efficacy of MSC transplantation by enhancing mitochondrial function in patients with DM and related complications.

Low-glucose culture environment can enhance the wound healing capability of diabetic adipose-derived stem cells

BACKGROUND

Application of autologous adipose-derived stem cells (ASC) for diabetic chronic wounds has become an emerging treatment option. However, ASCs from diabetic individuals showed impaired cell function and suboptimal wound healing effects. We proposed that adopting a low-glucose level in the culture medium for diabetic ASCs may restore their pro-healing capabilities.

METHODS

ASCs from diabetic humans and mice were retrieved and cultured in high-glucose (HG, 4.5 g/L) or low-glucose (LG, 1.0 g/L) conditions. Cell characteristics and functions were investigated in vitro. Moreover, we applied diabetic murine ASCs cultured in HG or LG condition to a wound healing model in diabetic mice to compare their healing capabilities in vivo.

RESULTS

Human ASCs exhibited decreased cell proliferation and migration with enhanced senescence when cultured in HG condition in vitro. Similar findings were noted in ASCs derived from diabetic mice. The inferior cellular functions could be partially recovered when they were cultured in LG condition. In the animal study, wounds healed faster when treated with HG- or LG-cultured diabetic ASCs relative to the control group. Moreover, higher collagen density, more angiogenesis and cellular retention of applied ASCs were found in wound tissues treated with diabetic ASCs cultured in LG condition.

CONCLUSIONS

In line with the literature, our study showed that a diabetic milieu exerts an adverse effect on ASCs. Adopting LG culture condition is a simple and effective approach to enhance the wound healing capabilities of diabetic ASCs, which is valuable for the clinical application of autologous ASCs from diabetic patients.

Stress-induced senescence in mesenchymal stem cells: Triggers, hallmarks, and current rejuvenation approaches

Mesenchymal stem cells (MSCs) have emerged as promising cell-based therapies in the treatment of degenerative and inflammatory conditions. However, despite accumulating evidence of the breadth of MSC functional potency, their broad clinical translation is hampered by inconsistencies in therapeutic efficacy, which is at least partly due to the phenotypic and functional heterogeneity of MSC populations as they progress towards senescence in vitro. MSC senescence, a natural response to aging and stress, gives rise to altered cellular responses and functional decline. This review describes the key regenerative properties of MSCs; summarises the main triggers, mechanisms, and consequences of MSC senescence; and discusses current cellular and extracellular strategies to delay the onset or progression of senescence, or to rejuvenate biological functions lost to senescence.

Metformin combats high glucose-induced damage to the osteogenic differentiation of human periodontal ligament stem cells via inhibition of the NPR3-mediated MAPK pathway

Background

High glucose-induced damage to the osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) has long been a challenge to periodontal regeneration for diabetic individuals. Metformin is an anti-hyperglycemic drug that exhibits abundant biological activities associated with cell metabolism and downstream tissue regeneration. However, how metformin combats damage to PDLSC osteogenic differentiation under high glucose and the underlying mechanisms remain unknown.

Methods

Osteogenic differentiation of PDLSCs was assessed by alkaline phosphatase (ALP) staining, ALP activity, Alizarin Red staining and quantitative assay, quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. RNA-seq analysis was performed to screen target genes of metformin, and the effects of target genes were confirmed using lentivirus transfection. Western blot analysis was also used to detect the protein level of underlying signaling pathways.

Results

We found that osteogenic differentiation of PDLSCs under high glucose was decreased, and metformin addition enhanced this capacity of differentiation. Furthermore, the results of RNA-seq analysis showed that natriuretic peptide receptor 3 (NPR3) was upregulated in PDLSCs under high glucose and downregulated after metformin addition. When the underlying pathways involved were investigated, we found that upregulation of NPR3 can compromise the metformin-enhanced PDLSC osteogenic differentiation and activate the MAPK pathway (especially the p38 MAPK and Erk1/2 pathway), and that inhibition of the NPR3-mediated p38 MAPK or Erk1/2 pathway enhanced the osteogenic differentiation of PDLSCs under high glucose.

Conclusions

The present study suggests that metformin may enhance the osteogenic differentiation of PDLSCs under high glucose via downregulation of NPR3 and inhibition of its downstream MAPK pathway. This is the first report identifying the involvement of NPR3-mediated MAPK pathway in the metformin-enhanced osteogenic differentiation, indicating that NPR3 antagonists, such as metformin, may be feasible therapeutics for periodontal tissue regeneration in diabetic individuals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02992-z.

Fatty acids of type 2 diabetic serum decrease the stemness properties of human adipose-derived mesenchymal stem cells

In type 2 diabetes, dyslipidemia and increased serum free fatty acids (FFAs) exacerbate the development of the disease through a negative effect on insulin secretion. Adipose-derived mesenchymal stem cells (AdMSCs) play a key role in regenerative medicine, and these cells can potentially be applied as novel therapeutic resources in the treatment of diabetes. In this study, AdMSCs were treated with diabetic or nondiabetic serum FFAs isolated from women of menopausal age. Serum FFAs were analyzed using gas-liquid chromatography. The expression level of the stemness markers CD49e and CD90 and the Wnt signaling target genes Axin-2 and c-Myc were evaluated using real-time PCR. The proliferation rate and colony formation were also assessed using a BrdU assay and crystal violet staining, respectively. The level of glutathione was assessed using cell fluorescence staining. Compared to nondiabetic serum, diabetic serum contained a higher percentage of oleate (1.5-fold, p < 0.01). In comparison with nondiabetic FFAs, diabetic FFAs demonstrated decreasing effects on the expression of CD90 (-51%, p < 0.001) and c-Myc (-48%, p < 0.05), and proliferation rate (-35%, p < 0.001), colony formation capacity (-50%, p < 0.01), and GSH levels (-62%, p < 0.05). The negative effect of the FFAs of diabetic serum on the stemness characteristics may impair the regenerative capabilities of AdMSCs.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

Type 2 Diabetes Mellitus Facilitates Shift of Adipose-Derived Stem Cells Ex Vivo Differentiation toward Osteogenesis among Patients with Obesity

Objective: Sedentary behavior with overnutrition provokes the development of obesity, insulin resistance, and type 2 diabetes mellitus (T2DM). The main progenitor cells of adipose tissue are adipose-derived stem cells (ADSCs) which can change differentiation, metabolic, and secretory phenotypes under obesity conditions. The purpose of this study was to evaluate ADSC osteogenesis activity among patients with obesity in normal glucose tolerance (NGT) and T2DM conditions. Methods: In the study, ADSCs from donors with obesity were used. After clinical characterization, all patients underwent bariatric surgery and ADSCs were isolated from subcutaneous fat biopsies. ADSCs were subjected to osteogenic differentiation, stained with Alizarin Red S, and harvested for real-time PCR and Western blotting. Cell senescence was evaluated with a β-galactosidase-activity-based assay. Results: Our results demonstrated the significantly increased calcification of ADSC on day 28 of osteogenesis in the T2DM group. These data were confirmed by the statistically significant enhancement of RUNX2 gene expression, which is a master regulator of osteogenesis. Protein expression analysis showed the increased expression of syndecan 1 and collagen I before and during osteogenesis, respectively. Moreover, T2DM ADSCs demonstrated an increased level of cellular senescence. Conclusion: We suggest that T2DM-associated cellular senescence can cause ADSC differentiation to shift toward osteogenesis, the impaired formation of new fat depots in adipose tissue, and the development of insulin resistance. The balance between ADSC adipo- and osteogenesis commitment is crucial for the determination of the metabolic fate of patients and their adipose tissue.

Comparison of the Infant and Adult Adipose-Derived Mesenchymal Stem Cells in Proliferation, Senescence, Anti-oxidative Ability and Differentiation Potential

BACKGROUND

Infant adipose-derived mesenchymal stem cells (ADSCs) collected from excised polydactyly fat tissue, which was surgical waste, could be cultured and expanded in vitro in this study. In addition, the collecting process would not cause pain in the host. In this study, the proliferation, reduction of senescence, anti-oxidative ability, and differentiation potential in the infant ADSCs were compared with those in the adult ADSCs harvested from thigh liposuction to determine the availability of infant ADSCs.

METHODS

Proliferation was determined by detecting the fold changes in cell numbers and doubling time periods. Senescence was analyzed by investigating the age-related gene expression levels and the replicative stress. The superoxide dismutase (SOD) gene expression, adipogenic, neurogenic, osteogenic, and tenogenic differentiation were compared by RT-qPCR. The chondrogenic differentiation efficiency was also determined using RT-qPCR and immunohistochemical staining.

RESULTS

The proliferation, SOD (SOD1, SOD2 and SOD3) gene expression, the stemness-related gene (c-MYC) and telomerase reverse transcriptase of the infant ADSCs at early passages were enhanced compared with those of the adults'. Cellular senescence related genes, including p16, p21 and p53, and replicative stress were reduced in the infant ADSCs. The adipogenic genes (PPARγ and LPL) and neurogenic genes (MAP2 and NEFH) of the infant ADSC differentiated cells were significantly higher than those of the adults' while the expression of the osteogenic genes (OCN and RUNX) and tenogenic genes (TNC and COL3A1) of both demonstrated opposite results. The chondrogenic markers (SOX9, COL2 and COL10) were enhanced in the infant ADSC differentiated chondrogenic pellets, and the expression levels of SODs were decreased during the differentiation process.

CONCLUSION

Cultured infant ADSCs demonstrate less cellular senescence and replicative stress, higher proliferation rates, better antioxidant defense activity, and higher potential of chondrogenic, adipogenic and neurogenic differentiation.

Influence of Glucose Concentration on Colony-Forming Efficiency and Biological Performance of Primary Human Tissue-Derived Progenitor Cells

OBJECTIVE

Glucose concentrations used in current cell culture methods are a significant departure from physiological glucose levels. The study focuses on comparing the effects of glucose concentrations on primary human progenitors (connective tissue progenitors [CTPs]) used for cartilage repair.

DESIGN

Cartilage- (Outerbridge grade 1, 2, 3; superficial and deep zone cartilage), infrapatellar fatpad-, synovium-, and periosteum-derived cells were obtained from 63 patients undergoing total knee arthroplasty and cultured simultaneously in fresh chondrogenic media containing 25 mM glucose (HGL) or 5 mM glucose (NGL) for pairwise comparison. Automated ASTM-based quantitative image analysis was used to determine colony-forming efficiency (CFE), effective proliferation rates (EPR), and sulfated-proteoglycan (GAG-ECM) staining of the CTPs across tissue sources.

RESULTS

HGL resulted in increased cell cultures with CFE = 0 compared with NGL in all tissue sources (P = 0.049). The CFE in NGL was higher than HGL for superficial cartilage (P < 0.001), and contrary for synovium-derived CTPs (P = 0.046) when CFE > 0. EPR of the CTPs did not differ between the media in the 6-day assay time period (P = 0.082). The GAG-ECM area of the CTPs and their progeny was increased in presence of HGL (P = 0.027).

CONCLUSION

Glucose concentration is critical to progenitor's physiology and should be taken into account in the setting of protocols for clinical or in vitro cell expansion strategies.

Impact of type 2 diabetes mellitus on the immunoregulatory characteristics of adipose tissue-derived mesenchymal stem cells

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder associated with several complications. Adipose tissue-derived mesenchymal stem cells (AT-MSCs) represent an emerging type of MSCs with high plasticity and immunoregulatory capabilities and are useful for treating inflammation-related disorders such as T2DM. However, the pathogenic microenvironment of T2DM may affect their therapeutic potential. We aimed to examine the impact of the diabetic milieu on the immunomodulatory/anti-inflammatory potential of AT-MSCs.

METHODS

We assessed the proliferation potential, cell surface expression of MSC-characteristic markers and immunomodulatory markers, along with the gene expression and protein secretion of pro-inflammatory and anti-inflammatory cytokines and adipokines in AT-MSCs derived from T2DM patients (dAT-MSCs) vs. those derived from non-diabetic volunteers (ndAT-MSCs). Furthermore, we evaluated the IFN-γ priming effect on both groups.

RESULTS

Our data revealed comparable proliferative activities in both groups. Flow cytometric analysis results showed a lower expression of CD200 and CD276 on dAT-MSCs vs. ndAT-MSCs. qPCR demonstrated upregulation of IL-1β associated with a downregulation of IL-1RN in dAT-MSCs vs. ndAT-MSCs. IFN-γ priming induced an elevation in CD274 expression associated with IDO1 and ILRN overexpression and IL-1β downregulation in both groups. ELISA analysis uncovered elevated levels of secreted IL-1β, TNF, and visfatin/NAMPT in dAT-MSCs, whereas IL-1RA and IDO levels were reduced. ELISA results were also evident in the secretome of dAT-MSCs upon IFN-γ priming.

CONCLUSIONS

This study suggests that the T2DM milieu alters the immunomodulatory characteristics of AT-MSCs with a shift towards a proinflammatory phenotype which may restrain their autologous therapeutic use. Furthermore, our findings indicate that IFN-γ priming could be a useful strategy for enhancing dAT-MSC anti-inflammatory potential.

E3 ligase activity of Carboxyl terminus of Hsc70 interacting protein (CHIP) in Wharton's jelly derived mesenchymal stem cells improves their persistence under hyperglycemic stress and promotes the prophylactic effects against diabetic cardiac damages

Recent studies indicate that umbilical cord stem cells are cytoprotective against several disorders. One critical limitation in using stem cells is reduction in their viability under stressful conditions, such as diabetes. However, the molecular intricacies responsible for diabetic conditions are not fully elucidated. In this study, we found that high glucose (HG) conditions induced loss of chaperone homeostasis, stabilized PTEN, triggered the downstream signaling cascade, and induced apoptosis and oxidative stress in Wharton's jelly derived mesenchymal stem cells (WJMSCs). Increased Carboxyl terminus of Hsc70 interacting protein (CHIP) expression promoted phosphatase and tensin homolog (PTEN) degradation via the ubiquitin-proteasome system and shortened its half-life during HG stress. Docking studies confirmed the interaction of CHIP with PTEN and FOXO3a with the Bim promoter region. Further, it was found that the chaperone system is involved in CHIP-mediated PTEN proteasomal degradation. CHIP depletion stabilizes PTEN whereas PTEN inhibition showed an inverse effect. CHIP overactivation suppressed the binding of FOXO3a with bim. Coculturing CHIP overexpressed WJMSCs suppressed HG-induced apoptosis and oxidative stress in embryo derived cardiac cell lines. CHIP overexpressing and PTEN silenced WJMSCs ameliorated diabetic effects in streptozotocin (STZ) induced diabetic rats and further improved their body weight and heart weight, and rescued from hyperglycemia-induced cardiac injury. Considering these, the current study suggests that CHIP confers resistance to apoptosis and acts as a potentiation factor in WJMSCs to provide protection from degenerative effects of diabetes.

CHIP-overexpressing Wharton's jelly-derived mesenchymal stem cells attenuate hyperglycemia-induced oxidative stress-mediated kidney injuries in diabetic rats

Accumulating studies have demonstrated the protective roles of mesenchymal stem cells against several disorders. However, one of their crucial limitations is reduced viability under stress conditions, including the hyperglycemia induced by diabetes. The molecular mechanisms involved in diabetes-induced kidney injuries are not fully elucidated. In this study, we found that high glucose (HG) reduced human proximal tubular epithelial cell viability. Further, hyperglycemia induced oxidative stress-mediated apoptosis and fibrosis in HK-2 cells via activation of the mitogen-activated protein kinases (MAPKs) including c-Jun N-terminal kinase JNK and p38 kinase. Carboxyl terminus of HSP70 interacting protein (CHIP) overactivation considerably rescued cell viability under HG stress. Moreover, Western blot analysis, flow cytometry, and MitoSOX staining revealed that hyperglycemia-induced mitochondrial oxidative stress production and apoptosis were attenuated in CHIP-overexpressing Wharton's jelly-derived mesenchymal stem cells (WJMSCs). Co-culture with CHIP-expressing WJMSCs maintained HK-2 cell viability, and inhibited apoptosis and fibrosis by attenuating HG-induced ROS-mediated MAPK activation. CHIP-overexpressing WJMSCs also rescued the decreased kidney weight and hyperglycemia-induced kidney damage observed in streptozotocin-induced diabetic rats. Cumulatively, the current research findings demonstrate that CHIP suppresses hyperglycemia-induced oxidative stress and confers resistance to MAPK-induced apoptosis and fibrosis, and suggests that CHIP protects WJMSCs and the high quality WJMSCs have therapeutic effects against diabetes-induced kidney injuries.

Unraveling the origin of glucose mediated disparate proliferation dynamics of cancer stem cells

Cancer stem cells (CSCs) often switch on their self-renewal programming aggressively to cause a relapse of cancer. Intriguingly, glucose triggers the proliferation propensities in CSCs by controlling the expression of the key transcription factor-like Nanog. However, the factors that critically govern this glucose-stimulated proliferation dynamics of CSCs remain elusive. Herein, by proposing a mathematical model of glucose-mediated Nanog regulation, we showed that the differential proliferation behavior of CSCs and cell-type similar to CSCs can be explained by considering the experimentally observed varied expression levels of key positive (STAT3) and negative (p53) regulators of Nanog. Our model reconciles various experimental observations and predicts ways to fine-tune the proliferation dynamics of these cell types in a context-dependent manner. In future, these modeling insights will be useful in developing improved therapeutic strategies to get rid of harmful CSCs.

Role of Hyperglycemia in the Senescence of Mesenchymal Stem Cells

The regenerative and immunomodulatory properties of mesenchymal stem cells (MSCs) have laid a sound foundation for their clinical application in various diseases. However, the clinical efficiency of MSC treatments varies depending on certain cell characteristics. Among these, the roles of cell aging or senescence cannot be excluded. Despite their stemness, evidence of senescence in MSCs has recently gained attention. Many factors may contribute to the senescence of MSCs, including MSC origin (biological niche), donor conditions (age, obesity, diseases, or unknown factors), and culture conditions in vitro. With the rapidly increasing prevalence of diabetes mellitus (DM) and gestational diabetes mellitus (GDM), the effects of hyperglycemia on the senescence of MSCs should be evaluated to improve the application of autologous MSCs. This review aims to present the available data on the senescence of MSCs, its relationship with hyperglycemia, and the strategies to suppress the senescence of MSCs in a hyperglycemic environment.

Targeting Stem Cells in Chronic Inflammatory Diseases

Mesenchymal stem cell (MSC) dysfunction is a serious complication in ageing and age-related inflammatory diseases such as type 2 diabetes mellitus. Inflammation and oxidative stress-induced cellular senescence alter the immunomodulatory ability of MSCs and hamper their pro-regenerative function, which in turn leads to an increase in disease severity, maladaptive tissue damage and the development of comorbidities. Targeting stem/progenitor cells to restore their function and/or protect them against impairment could thus improve healing outcomes and significantly enhance the quality of life for diabetic patients. This review discusses the dysregulation of MSCs' immunomodulatory capacity in the context of diabetes mellitus and focuses on intervention strategies aimed at MSC rejuvenation. Research pertaining to the potential therapeutic use of either pharmacological agents (NFкB antagonists), natural products (phytomedicine) or biological agents (exosomes, probiotics) to improve MSC function is discussed and an overview of the most pertinent methodological considerations given. Based on in vitro studies, numerous anti-inflammatory agents, antioxidants and biological agents show tremendous potential to revitalise MSCs. An integrated systems approach and a thorough understanding of complete disease pathology are however required to identify feasible candidates for in vivo targeting of MSCs.

The proper concentrations of dextrose and lidocaine in regenerative injection therapy: in vitro study

Background

Prolotherapy is a proliferation therapy as an alternative medicine. A combination of dextrose solution and lidocaine is usually used in prolotherapy. The concentrations of dextrose and lidocaine used in the clinical field are very high (dextrose 10%-25%, lidocaine 0.075%-1%). Several studies show about 1% dextrose and more than 0.2% lidocaine induced cell death in various cell types. We investigated the effects of low concentrations of dextrose and lidocaine in fibroblasts and suggest the optimal range of concentrations of dextrose and lidocaine in prolotherapy.

Methods

Various concentrations of dextrose and lidocaine were treated in NIH-3T3. Viability was examined with trypan blue exclusion assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Migration assay was performed for measuring the motile activity. Extracellular signal-regulated kinase (Erk) activation and protein expression of collagen I and α-smooth muscle actin (α-SMA) were determined with western blot analysis.

Results

The cell viability was decreased in concentrations of more than 5% dextrose and 0.1% lidocaine. However, in the concentrations 1% dextrose (D1) and 0.01% lidocaine (L0.01), fibroblasts proliferated mildly. The ability of migration in fibroblast was increased in the D1, L0.01, and D1 + L0.01 groups sequentially. D1 and L0.01 increased Erk activation and the expression of collagen I and α-SMA and D1 + L0.01 further increased. The inhibition of Erk activation suppressed fibroblast proliferation and the synthesis of collagen I.

Conclusions

D1, L0.01, and the combination of D1 and L0.01 induced fibroblast proliferation and increased collagen I synthesis via Erk activation.

Therapeutic Potential of Reactive Oxygen Species: State of the Art and Recent Advances

In the last decade, several studies have proven that when at low concentration reactive oxygen species (ROS) show an adaptive beneficial effect and posited the idea that they can be utilized as inexpensive and convenient inducers of tissue regeneration. On the other hand, the recent discovery that cancer cells are more sensitive to oxidative damage paved the way for their use in the selective killing of tumor cells, and sensors to monitor ROS production during cancer treatment are under extensive investigation. Nevertheless, although ROS-activated signaling pathways are well established, less is known about the mechanisms underlying the switch from an anabolic to a cytotoxic response. Furthermore, a high variability in biological response is observed between different modalities of administration, cell types, donor ages, eventual concomitant diseases, and external microenvironment. On the other hand, available preclinical studies are scarce, whereas the quest for the most suitable systems for in vivo delivery is still elusive. Furthermore, new strategies to control the temporal pattern of ROS release need to be developed, if considering their tumorigenic potential. This review initially discusses ROS mechanisms of action and their potential application in stem cell biology, tissue engineering, and cancer therapy. It then outlines the state of art of ROS-based drugs and identifies challenges faced in translating ROS research into clinical practice.

[Research progress on effects of high glucose microenvironment on biological activity of adipose-derived stem cells]

Objective

To summarize the research progress of the effects of high glucose microenvironment on the biological activity of adipose-derived stem cells (ADSCs).

Methods

The literature on the high glucose microenvironment and ADSCs at home and abroad in recent years was reviewed, and the effects of high glucose microenvironment on the general characteristics, differentiation potential, angiogenesis, and nerve regeneration of ADSCs were summarized.

Results

The accumulation of advanced glycosylation end products (AGEs) in the high glucose microenvironment led to changes in the biological activities of ADSCs through various pathways, including cell surface markers, proliferation, migration, multi-lineage differentiation, secretory function, and tissue repair ability. The ability of ADSCs to promote angiogenesis and nerve regeneration in high glucose microenvironment is still controversial.

Conclusion

High glucose microenvironment can affect the biological activity of ADSCs, and the effect and mechanism of ADSCs on angiogenesis and nerve regeneration in high glucose microenvironment need to be further studied.

Osteogenesis of adipose-derived stem cells from patients with glucose metabolism disorders

Background

Adipose derived stem cells (ADSCs) are clinically widely used somatic stem cells obtained from white adipose tissue. They are characterized by ability to differentiate e.g. into osteoblasts and might successfully regenerate bone tissue in fracture repair. However, the main problem of somatic stem cells is a documented influence of various diseases, drugs or age which can inhibit cells activity. Therefore, in the present study, we investigated the influence of insulin resistance (IR) and type 2 diabetes (T2D) on the proliferation and differentiation potential of ADSCs.

Methods

The fat from subcutaneous abdominal adipose tissue was acquired by lipoaspiration from 23 voluntary participants, divided into three groups: with diabetes type 2, with insulin resistance and control healthy donors. The proliferative potential was analyzed by cell cytotoxicity assays and by mRNA expression of genes connected with proliferation. Flow cytometry was done for identifying proteins characteristic for mesenchymal stem cells and an analysis of osteogenic differentiation potential based on the assessment of osteogenic markers by real time RT-qPCR, and the evaluation of calcium deposition were also performed.

Results

The results showed that diabetes type 2 lowered the activity of ADSCs in proliferation assays and changed their phenotypical characteristics. Interestingly, we observed differences in the proliferation potential of ADSCs in patients with insulin resistance, which is often the first phase of diabetes, compared to the control. It might suggest that insulin resistance, early-stage T2D, alters the activity of cells. Moreover, expression of osteogenesis markers was higher in cells from T2D patients than in cells from patients with IR and control.

Conclusion

We conclude that type 2 diabetes changes the activity of stem cells, and insulin resistance influences on the proliferation of ADSCs.

Identifying the Therapeutic Significance of Mesenchymal Stem Cells

The pleiotropic behavior of mesenchymal stem cells (MSCs) has gained global attention due to their immense potential for immunosuppression and their therapeutic role in immune disorders. MSCs migrate towards inflamed microenvironments, produce anti-inflammatory cytokines and conceal themselves from the innate immune system. These signatures are the reason for the uprising in the sciences of cellular therapy in the last decades. Irrespective of their therapeutic role in immune disorders, some factors limit beneficial effects such as inconsistency of cell characteristics, erratic protocols, deviating dosages, and diverse transfusion patterns. Conclusive protocols for cell culture, differentiation, expansion, and cryopreservation of MSCs are of the utmost importance for a better understanding of MSCs in therapeutic applications. In this review, we address the immunomodulatory properties and immunosuppressive actions of MSCs. Also, we sum up the results of the enhancement, utilization, and therapeutic responses of MSCs in treating inflammatory diseases, metabolic disorders and diabetes.

Diabetes-induced glucolipotoxicity impairs wound healing ability of adipose-derived stem cells-through the miR-1248/CITED2/HIF-1α pathway

Despite being an attractive cell type for mesenchymal stem cell (MSC) transplantation therapy for wound healing, human adipose-derived stem cells (hADSCs) from diabetes mellitus (DM) patients result in remarkable retention of stem cell activity due to diabetes-induced glucolipotoxicity. We explored the effect of diabetes and medium containing AGEs on the cell activity, phenotype, multipotency, angiogenic potential, and the therapeutic effect of hADSCs. Then, miRNA-1248 was selected by miRNA microarray analysis to further study the core molecular pathways that regulate the wound healing ability of hADSCs. hADSCs isolated from DM patients or cultured in medium containing AGEs in vitro exhibited decreased effectiveness in stem cell therapy. The expression of miRNA-1248 was decreased in the hADSCs of DM patients and hence failed to positively regulate stem cell activity, differentiation functions, and angiogenesis promotion effect. This concomitantly increased the expression of CITED2, an inhibitor of HIF-1α, thus influencing growth factors that promote angiogenesis, cellular proliferation, and wound healing. Overall, our data demonstrated that the glucolipotoxicity-impaired wound healing ability of hADSCs might occur through the miR-1248/CITED2/HIF-1α pathway. MiRNA-1248 may have potential to be used as a novel therapeutic target for wound healing in DM patients or restoring the wound healing ability of diabetic hADSCs.

Impact of Type 2 Diabetes Mellitus on Human Bone Marrow Stromal Cell Number and Phenotypic Characteristics

Human bone marrow-derived mesenchymal stromal cells (MSCs) have been investigated in numerous disease settings involving impaired regeneration because of the crucial role they play in tissue maintenance and repair. Considering the number of comorbidities associated with type 2 diabetes mellitus (T2DM), the hypothesis that MSCs mediate these comorbidities via a reduction in their native maintenance and repair activities is an intriguing line of inquiry. Here, it is demonstrated that the number of bone marrow-derived MSCs in people with T2DM was reduced compared to that of age-matched control (AMC) donors and that this was due to a specific decrease in the number of MSCs with osteogenic capacity. There were no differences in MSC cell surface phenotype or in MSC expansion, differentiation, or angiogenic or migratory capacity from donors living with T2DM as compared to AMCs. These findings elucidate the basic biology of MSCs and their potential as mediators of diabetic comorbidities, especially osteopathies, and provide insight into donor choice for MSC-based clinical trials. This study suggests that any role of bone marrow MSCs as a mediator of T2DM comorbidity is likely due to a reduction in the osteoprogenitor population size and not due to a permanent alteration to the MSCs' capacity to maintain tissue homeostasis through expansion and differentiation.

The effect of high glucose on the biological characteristics of nucleus pulposus-derived mesenchymal stem cells

Diabetes mellitus (DM) is a dependent risk factor in the progression of intervertebral disc degeneration (IVDD). High glucose supply has negative effects on nucleus pulpous (NP) cell and mesenchymal stem cell (MSC) biology. However, the effect of hyperglycaemia on the biological characterization of nucleus pulpous-derived mesenchymal stem cell (NPMSC) has not been investigated previously. Therefore, further exploration of the effects of DM-associated hyperglycaemia on NPMSC biology is important to better understand and develop endogenous repair strategies of DM patient-associated IVDD. Therefore, the cell biological characteristics were compared between NPMSC cultured in media with low glucose concentration (LG-NPMSC) and high glucose concentration (HG-NPMSC). The results demonstrated that HG-NPMSC showed significantly decreased cell proliferation, colony formation ability, migration and wound-healing capability compared with those of LG-NPMSC. HG-NPMSC also showed significantly decreased expressions of stemness genes and mRNA and protein expressions of silent information regulator protein 1 (SIRT1), SIRT6, hypoxia inducible factor-1α (HIF-1α) and glucose transporter 1 (GLUT-1), whereas increased cell apoptosis, cell senescence and caspase-3 expression. These results suggest that high glucose may decrease proliferation and stemness maintenance ability and increase apoptosis and senescence of NPMSC. SIGNIFICANCE OF THE STUDY: We found that high glucose concentration significantly decreased cell proliferation, colony formation ability, migration and wound-healing capability of nucleus pulposus-derived mesenchymal stem cells. Moreover, high glucose cultured nucleus pulposus-derived mesenchymal stem cells showed significantly decreased expression of stemness genes, related mRNA and protein, whereas increased cell apoptosis, cell senescence and expression of caspase-3. The present study indicated that better control of high concentration glucose in the early stage of diabetes mellitus should be recommended to prevent or limit intervertebral disc degeneration.

The emerging role of cellular senescence in renal diseases

Cellular senescence represents the state of irreversible cell cycle arrest during cell division. Cellular senescence not only plays a role in diverse biological events such as embryogenesis, tissue regeneration and repair, ageing and tumour occurrence prevention, but it is also involved in many cardiovascular, renal and liver diseases through the senescence-associated secretory phenotype (SASP). This review summarizes the molecular mechanisms underlying cellular senescence and its possible effects on a variety of renal diseases. We will also discuss the therapeutic approaches based on the regulation of senescent and SASP blockade, which is considered as a promising strategy for the management of renal diseases.

Applicability of adipose-derived mesenchymal stem cells in treatment of patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is mainly characterized by insulin resistance (IR) and impaired insulin secretion. The chronic inflammatory process contributed to IR and could also hamper pancreatic β cell function. However, currently applied treatment cannot reverse β cell damage or alleviate inflammation. Mesenchymal stem cells (MSCs), the cell-based therapy for their self-renewable, differentiation potential, and immunosuppressive properties, have been demonstrated in displaying therapeutic effects in T2DM. Adipose-derived MSCs (AD-MSCs) attracted more attention due to less harvested inconvenience and ethical issues commonly accompany with bone marrow-derived MSCs (BM-MSCs) and fetal annex-derived MSCs. Both AD-MSC therapy studies and mechanism explorations in T2DM animals presented that AD-MSCs could translate to clinical application. However, hyperglycemia, hyperinsulinemia, and metabolic disturbance in T2DM are crucial for impairment of AD-MSC function, which may limit the therapeutical effects of MSCs. This review focuses on the outcomes and the molecular mechanisms of MSC therapies in T2DM which light up the hope of AD-MSCs as an innovative strategy to cure T2DM.

Hyperglycemia Changes Expression of Key Adipogenesis Markers (C/EBPα and PPARᵞ)and Morphology of Differentiating Human Visceral Adipocytes

Disturbances in adipose tissue significantly contribute to the development of metabolic disorders, which are connected with hyperglycemia (HG) and underlain by epigenetics-based mechanisms. Therefore, we aimed to evaluate the effect of hyperglycemia on proliferating, differentiating and maturating human visceral pre/adipocytes (HPA-v). Three stages of cell culture were conducted under constant or variable glycemic conditions. Adipogenesis progress was assessed using BODIPY 505/515 staining. Lipid content typical for normal and hyperglycemic conditions of adipocytes was analyzed using Raman spectroscopy and imaging. Expression of adipogenic markers, PPARγ and C/EBPα, was determined at the mRNA and protein levels. We also examined expression of miRNAs proven to target PPARγ (miR-34a-5p) and C/EBPα (miR-137-3p), employing TaqMan Low-Density Arrays (TLDA) cards. Hyperglycemia altered morphology of differentiating HPA-v in relation to normoglycemia by accelerating the formation of lipid droplets and making their numbers and volume increase. Raman results confirmed that the qualitative and quantitative lipid composition under normal and hyperglycemic conditions were different, and that the number of lipid droplets increased in (HG)-treated cells. Expression profiles of both examined genes markedly changed either during adipogenesis under physiological and hyperglycemic conditions, orat particular stages of adipogenesis upon chronic and/or variable glycemia. Expression levels of PPARγ seemed to correspond to some expression changes of miR-34a-5p. miR-137-3p, whose expression was rather stable throughout the culture, did not seem to affect C/EBPα. Our observations revealed that chronic and intermittent hyperglycemia change the morphology of visceral pre/adipocytes during adipogenesis. Moreover, hyperglycemia may utilize miR-34a-5p to induce some expression changes in PPARγ.

Diabetic Human Adipose-Derived Stem Cells Accelerate Pressure Ulcer Healing by Inducing Angiogenesis and Neurogenesis

Adipose-derived stem cells (ASCs) possess a well-characterized capacity to enhance cutaneous wound healing. However, many controversies exist regarding ASCs from diabetic patients (dASCs). No report exists on the administration of dASCs for the treatment of pressure ulcers. The aim of this study was to compare properties of dASCs and nondiabetic ASCs (nASCs). In addition, we studied if dASCs enhanced pressure ulcer healing in a rodent pressure ulcer model and investigated underlying mechanisms. We found similar expression of cell surface markers and characteristics in dASCs and nASCs, although dASCs exhibited decreased proliferation and osteogenic differentiation capacity and enhanced adipogenic differentiation capacity. dASCs had beneficial effects on chronic wound healing, though some aspects of their capacity were impaired. The ability of dASCs to promote nerve regeneration was not compromised. dASCs promoted pressure ulcer healing and improved healing by modulating inflammation, promoting angiogenesis and neuroregeneration, enhancing collagen deposition, and increasing re-epithelization. These data may provide a theoretical foundation for further clinical administration of ASCs for chronic wound healing in patients with diabetes.

Cell sheet composed of adipose-derived stem cells demonstrates enhanced skin wound healing with reduced scar formation

Scar formation remains a major clinical concern following tissue injuries such as skin wounds. Adipose-derived stem cell (ASC) sheets can be fabricated quickly through stimulation with l-ascorbate 2-phosphate and have valuable applications in tissue regeneration and wound healing. However, the antifibrotic capability of ASCs in cell sheet format has not been sufficiently investigated. We employed a murine model of healing-impaired cutaneous wounds and observed faster wound healing with ASC sheet treatment. Significantly more engrafted ASCs were observed in the wound tissue treated with ASC sheets at 14 days after wounding compared with dissociated cells. Moreover, no ASCs were found at day 28, which indicated a minimal risk of long-term side effects. The neoskin formed in the presence of ASC sheets exhibited a thickness comparable to normal skin and possessed a highly organized collagen structure. ASC sheets also suppressed macrophage infiltration and modulated TNF-α and TGF-β1 expression in vivo. Examination of fibroblasts cultured in ASC-conditioned medium indicated an anti-scarring effect of the ASC sheets evidenced by the downregulation of TGF-β1 and α-SMA in fibroblasts, which was likely mediated through the increased secretion of hepatocyte growth factor. Moreover, ASC sheets secreted significantly more C1q/TNF-related protein-3, which inhibited the C-C motif ligand 2 release by macrophages in vitro and subsequently reduced the chemotaxis of unstimulated macrophages. This mechanism may account for the observed decrease in recruitment of macrophages into the wound tissue. We conclude that ASC sheets possess the necessary paracrine factors to improve skin wound healing with a superior neoskin quality.

STATEMENT OF SIGNIFICANCE

Adipose-derived stem cell (ASC) sheets exhibit great potential for tissue regeneration. In this study, we investigated whether ASC sheets can ameliorate skin wound healing with reduced scar formation, and faster wound healing was observed when applying ASC sheets in an impaired wound healing model of mice. The neoskin formed in the presence of ASC sheets exhibited a thickness comparable to normal skin with a more organized collagen structure. In vitro experiments suggested that the anti-scarring effect of the ASC sheets was partly mediated through increased secretion of hepatocyte growth factor. Moreover, ASC sheets secreted significantly more C1q/TNF-related protein-3, which may account for the decreased recruitment of macrophages into the wound tissue. Therefore, ASC sheets possess the necessary paracrine factors to improve skin wound healing with less scarring, thus representing a desirable method of topical wound treatment.

Regulation of the mitochondrial reactive oxygen species: Strategies to control mesenchymal stem cell fates ex vivo and in vivo

Mesenchymal stem cells (MSCs) are broadly used in cell‐based regenerative medicine because of their self‐renewal and multilineage potencies in vitro and in vivo. To ensure sufficient amounts of MSCs for therapeutic purposes, cells are generally cultured in vitro for long‐term expansion or specific terminal differentiation until cell transplantation. Although physiologically up‐regulated reactive oxygen species (ROS) production is essential for maintenance of stem cell activities, abnormally high levels of ROS can harm MSCs both in vitro and in vivo. Overall, additional elucidation of the mechanisms by which physiological and pathological ROS are generated is necessary to better direct MSC fates and improve their therapeutic effects by controlling external ROS levels. In this review, we focus on the currently revealed ROS generation mechanisms and the regulatory routes for controlling their rates of proliferation, survival, senescence, apoptosis, and differentiation. A promising strategy in future regenerative medicine involves regulating ROS generation via various means to augment the therapeutic efficacy of MSCs, thus improving the prognosis of patients with terminal diseases.

Exercise ameliorates high-fat diet-induced impairment of differentiation of adipose-derived stem cells into neuron-like cells in rats

Adipose-derived stem cells (ADSCs) can differentiate into neurons under particular conditions. It remains largely unknown whether this differentiation potential is affected by physical conditions such as obesity, which modulates the functions of adipose tissue. In this study, we determined the impact of either a 9-week high-fat diet (60% fat; HFD) or 9-week exercise training on the differentiation potential of ADSCs into neuron-like cells in male Wistar rats. Rats were randomly assigned to a normal diet-fed (ND-SED) group, HFD-fed (HFD-SED) group, or exercise-trained HFD-fed group (HFD-EX). After a 9-week intervention, ADSCs from all groups differentiated into neuron-like cells. Expression of neuronal marker proteins (nestin, βIII-tubulin, and microtubule-associated protein 2 [MAP2]) and the average length of cell neurites were lower in cells from HFD-SED rats than in other groups. Instead, protein expression of COX IV and Cyt-c, the Bax/Bcl-2 and LC3-II/I ratio, and the malondialdehyde level in culture medium were higher in cells from HFD-SED rats. No significant difference between ND-SED and HFD-EX rats was observed, except for the average length of cell neurites in MAP2. Thus, HFD impaired the differentiation potential of ADSCs into neuron-like cells, which was accompanied by increases in apoptotic activity and oxidative stress. Importantly, exercise training ameliorated the HFD-induced impairment of neurogenesis in ADSCs. The adipose tissue microenvironment could influence the differentiation potential of ADSCs, a source of autologous stem cell therapy.

Mesenchymal Stromal Cell Characteristics and Regenerative Potential in Cardiovascular Disease: Implications for Cellular Therapy

Administration of mesenchymal stromal cells (MSCs) is a promising strategy to treat cardiovascular disease (CVD). As progenitor cells may be negatively affected by both age and comorbidity, characterization of MSC function is important to guide decisions regarding use of allogeneic or autologous cells. Definitive answers on which factors affect MSC function can also aid in selecting which MSC donors would yield the most therapeutically efficacious MSCs. Here we provide a narrative review of MSC function in CVD based on a systematic search. A total of 41 studies examining CVD-related MSC (dys)function were identified. These data show that MSC characteristics and regenerative potential are often affected by CVD. However, studies presented conflicting results, and directed assessment of MSC parameters relevant to regenerative medicine applications was lacking in many studies. The predictive ability of in vitro assays for in vivo efficacy was rarely assessed. There was no correlation between quality of study reporting and study findings. Age mismatch was also not associated with study findings or effect size. Future research should focus on assays that assess regenerative potential in MSCs and parameters that relate to clinical success.

Unraveling the compromised biomechanical performance of type 2 diabetes- and Roux-en-Y gastric bypass bone by linking mechanical-structural and physico-chemical properties

Type 2 diabetes mellitus (T2DM) is a metabolic disorder associated with obesity and hyperglycemia. Roux-en-Y gastric bypass (RYGB) surgery is a common treatment for severely obese patients and T2DM. Both RYGB and T2DM are linked to increased skeletal fragility, though the exact mechanisms are poorly understood. Our aim was to characterize the structural, mechanical and compositional properties of bones from diet-induced obese and RYGB-treated obese (bypass) mice to elucidate which the exact factors are contributing to the increased skeletal fragility. To achieve this, a combinatory approach including microfocus X-ray computed tomography, 3-point bending, finite element modeling and Raman spectroscopy, was used. Compared to aged-matched lean controls, the obese mice displayed decreased cortical thickness, trabecular bone loss, decreased stiffness and increased Young’s modulus. For the bypass mice, these alterations were even more pronounced, and additionally they showed low mineral-to-matrix ratio in the cortical endosteal area. Accumulation of the advanced glycation end-product (AGE) pentosidine was found in the cortex of obese and bypass groups and this accumulation was correlated with an increased Young’s modulus. In conclusion, we found that the increased fracture risk in T2DM- and post-RYGB bones is mainly driven by accumulation of AGEs and macro-structural alterations, generating biomechanical dysfunctionality.

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

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

Optineurin-mediated mitophagy protects renal tubular epithelial cells against accelerated senescence in diabetic nephropathy

Premature senescence is a key process in the progression of diabetic nephropathy (DN). Premature senescence of renal tubular epithelial cells (RTEC) in DN may result from the accumulation of damaged mitochondria. Mitophagy is the principal process that eliminates damaged mitochondria through PTEN-induced putative kinase 1 (PINK1)-mediated recruitment of optineurin (OPTN) to mitochondria. We aimed to examine the involvement of OPTN in mitophagy regulation of cellular senescence in RTEC in the context of DN. In vitro, the expression of senescence markers P16, P21, DcR2, SA-β-gal, SAHF, and insufficient mitophagic degradation marker (mitochondrial P62) in mouse RTECs increased after culture in 30 mM high-glucose (HG) conditions for 48 h. Mitochondrial fission/mitophagy inhibitor Mdivi-1 significantly enhanced RTEC senescence under HG conditions, whereas autophagy/mitophagy agonist Torin1 inhibited cell senescence. MitoTempo inhibited HG-induced mitochondrial reactive oxygen species and cell senescence with or without Mdivi-1. The expression of PINK1 and OPTN, two regulatory factors for mitophagosome formation, decreased significantly after HG stimulation. Overexpression of PINK1 did not enhance mitophagosome formation under HG conditions. OPTN silencing significantly inhibited HG-induced mitophagosome formation, and overexpression of OPTN relieved cellular senescence through promoting mitophagy. In clinical specimens, renal OPTN expression was gradually decreased with increased tubulointerstitial injury scores. OPTN-positive renal tubular cells did not express senescence marker P16. OPTN expression also negatively correlated with serum creatinine levels, and positively correlated with eGFR. Thus, OPTN-mediated mitophagy plays a crucial regulatory role in HG-induced RTEC senescence in DN. OPTN may, therefore, be a potential antisenescence factor in DN.

Diabetes as risk factor for pancreatic cancer: Hyperglycemia promotes epithelial-mesenchymal-transition and stem cell properties in pancreatic ductal epithelial cells

Type 2 diabetes mellitus (T2DM) is associated with hyperglycemia and a risk to develop pancreatic ductal adenocarcinoma (PDAC), one of the most fatal malignancies. Cancer stem cells (CSC) are essential for initiation and maintenance of tumors, and acquisition of CSC-features is linked to epithelial-mesenchymal-transition (EMT). The present study investigated whether hyperglycemia promotes EMT and CSC-features in premalignant and malignant pancreatic ductal epithelial cells (PDEC). Under normoglycemia (5 mM d-glucose), Panc1 PDAC cells but not premalignant H6c7-kras cells exhibited a mesenchymal phenotype along with pronounced colony formation. While hyperglycemia (25 mM d-glucose) did not impact the mesenchymal phenotype of Panc1 cells, CSC-properties were aggravated exemplified by increased Nanog expression and Nanog-dependent formation of holo- and meroclones. In H6c7-kras cells, high glucose increased secretion of Transforming-Growth-Factor-beta1 (TGF-β1) as well as TGF-β1 signaling, and in a TGF-β1-dependent manner reduced E-cadherin expression, increased Nestin expression and number of meroclones. Finally, reduced E-cadherin expression was detected in pancreatic ducts of hyperglycemic but not normoglycemic mice. These data suggest that hyperglycemia promotes the acquisition of mesenchymal and CSC-properties in PDEC by activating TGF-β signaling and might explain how T2DM facilitates pancreatic tumorigenesis.

High glucose induces the aging of mesenchymal stem cells via Akt/mTOR signaling

It has previously been demonstrated that glucose is important in the process of stem cell aging. However, the mechanisms of cell senescence induced by high glucose (HG) remain to be elucidated. The preliminary study indicated that D-galactose induced mesenchymal stem cell (MSCs) aging. The present study demonstrated, following treatment with 11.0 or 22.0 mM HG for 14 days, that HG significantly promoted MSCs aging and the expression levels of phosphorylated (p-)phosphatidylinositol 3-kinase/protein kinase B (Akt) and p-mammalian target of rapamycin signaling (mTOR) in the HG groups were increased compared with the control group. However, following Akt inhibition with 1.0 or 10.0 nM MK-2206, which is an Akt-specific small molecule inhibitor, the senescence-cell value in the HG group was significantly decreased compared with the control group. These results indicated that HG induced MSCs senescence and this effect was primarily mediated via the Akt/mTOR signaling pathway.

Effect of High Glucose Levels on White Adipose Cells and Adipokines-Fuel for the Fire

White adipocytes release adipokines that influence metabolic and vascular health. Hypertrophic obesity is associated with adipose tissue malfunctioning, leading to inflammation and insulin resistance. When pancreatic islet β cells can no longer compensate, the blood glucose concentration rises (hyperglycemia), resulting in type 2 diabetes. Hyperglycaemia may further aggravate adipose cell dysfunction in ~90% of patients with type 2 diabetes who are obese or overweight. This review will focus on the effects of high glucose levels on human adipose cells and the regulation of adipokines.

Adipose-derived stem cells were impaired in restricting CD4+T cell proliferation and polarization in type 2 diabetic ApoE-/- mouse

BACKGROUND

Atherosclerosis (AS) is the most common and serious complication of type 2 diabetes mellitus (T2DM) and is accelerated via chronic systemic inflammation rather than hyperglycemia. Adipose tissue is the major source of systemic inflammation in abnormal metabolic state. Pro-inflammatory CD4⁺T cells play pivotal role in promoting adipose inflammation. Adipose-derived stem cells (ADSCs) for fat regeneration have potent ability of immunosuppression and restricting CD4⁺T cells as well. Whether T2DM ADSCs are impaired in antagonizing CD4⁺T cell proliferation and polarization remains unclear.

METHODS

We constructed type 2 diabetic ApoE^-/- mouse models and tested infiltration and subgroups of CD4⁺T cell in stromal-vascular fraction (SVF) in vivo. Normal/T2DM ADSCs and normal splenocytes with or without CD4 sorting were separated and co-cultured at different scales ex vivo. Immune phenotypes of pro- and anti-inflammation of ADSCs were also investigated. Flow cytometry (FCM) and ELISA were applied in the experiments above.

RESULTS

CD4⁺T cells performed a more pro-inflammatory phenotype in adipose tissue in T2DM ApoE^-/- mice in vivo. Restriction to CD4⁺T cell proliferation and polarization was manifested obviously weakened after co-cultured with T2DM ADSCs ex vivo. No obvious distinctions were found in morphology and growth type of both ADSCs. However, T2DM ADSCs acquired a pro-inflammatory immune phenotype, with secreting less PGE2 and expressing higher MHC-II and co-stimulatory molecules (CD40, CD80). Normal ADSCs could also obtain the phenotypic change after cultured with T2DM SVF supernatant.

CONCLUSION

CD4⁺T cell infiltration and pro-inflammatory polarization exist in adipose tissue in type 2 diabetic ApoE^-/- mice. T2DM ADSCs had impaired function in restricting CD4⁺T lymphocyte proliferation and pro-inflammatory polarization due to immune phenotypic changes.

High glucose suppresses embryonic stem cell differentiation into cardiomyocytes : High glucose inhibits ES cell cardiogenesis

Background

Babies born to mothers with pregestational diabetes have a high risk for congenital heart defects (CHD). Embryonic stem cells (ESCs) are excellent in vitro models for studying the effect of high glucose on cardiac lineage specification because ESCs can be differentiated into cardiomyocytes. ESC maintenance and differentiation are currently performed under high glucose conditions, whose adverse effects have never been clarified.

Method

We investigated the effect of high glucose on cardiomyocyte differentiation from a well-characterized ESC line, E14, derived from mouse blastocysts. E14 cells maintained under high glucose (25 mM) failed to generate any beating cardiomyocytes using the hanging-drop embryonic body method. We created a glucose-responsive E14 cell line (GR-E14) through a graduated low glucose adaptation. The expression of stem cell markers was similar in the parent E14 cells and the GR-E14 cells.

Results

Glucose transporter 2 gene was increased in GR-E14 cells. When GR-E14 cells were differentiated into cardiomyocytes under low (5 mM) or high (25 mM) glucose conditions, high glucose significantly delayed the appearance and reduced the number of TNNT2 (Troponin T Type 2)-positive contracting cardiomyocytes. High glucose suppressed the expression of precardiac mesoderm markers, cardiac transcription factors, mature cardiomyocyte markers, and potassium channel proteins. High glucose impaired the functionality of ESC-derived cardiomyocytes by suppressing the frequencies of Ca²⁺ wave and contraction.

Conclusions

Our findings suggest that high glucose inhibits ESC cardiogenesis by suppressing key developmental genes essential for the cardiac program.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0446-5) contains supplementary material, which is available to authorized users.

Cu, Zn-Superoxide Dismutase Increases the Therapeutic Potential of Adipose-derived Mesenchymal Stem Cells by Maintaining Antioxidant Enzyme Levels

In the present study, we investigated the ability of Cu, Zn-superoxide dismutase (SOD1) to improve the therapeutic potential of adipose tissue-derived mesenchymal stem cells (Ad-MSCs) against ischemic damage in the spinal cord. Animals were divided into four groups: the control group, vehicle (PEP-1 peptide and artificial cerebrospinal fluid)-treated group, Ad-MSC alone group, and Ad-MSC-treated group with PEP-1-SOD1. The abdominal aorta of the rabbit was occluded for 30 min in the subrenal region to induce ischemic damage, and immediately after reperfusion, artificial cerebrospinal fluid or Ad-MSCs (2 × 10⁵) were administered intrathecally. In addition, PEP-1 or 0.5 mg/kg PEP-1-SOD1 was administered intraperitoneally to the Ad-MSC-treated rabbits. Motor behaviors and NeuN-immunoreactive neurons were significantly decreased in the vehicle-treated group after ischemia/reperfusion. Administration of Ad-MSCs significantly ameliorated the changes in motor behavior and NeuN-immunoreactive neuronal survival. In addition, the combination of PEP-1-SOD1 and Ad-MSCs further increased the ameliorative effects of Ad-MSCs in the spinal cord after ischemia. Furthermore, the administration of Ad-MSCs with PEP-1-SOD1 decreased lipid peroxidation and maintained levels of antioxidants such as SOD1 and glutathione peroxidase compared to the Ad-MSC alone group. These results suggest that combination therapy using Ad-MSCs and PEP-1-SOD1 strongly protects neurons from ischemic damage by modulating the balance of lipid peroxidation and antioxidants.

Mitochondrial Fission Increases Apoptosis and Decreases Autophagy in Renal Proximal Tubular Epithelial Cells Treated with High Glucose

The aim of this study was to examine the effect of mitochondrial morphogenesis changes on apoptosis and autophagy of high-glucose-treated proximal tubular epithelial cells (HK2). Cell viability, apoptosis, and mitochondrial morphogenesis were examined using crystal violet, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), and mitotracker staining, respectively. High glucose inhibited cell viability and induced mitochondrial fission in HK2 cells. After depleting mitofusin 1 (MFN1), the MFN1(-) HK2 cells (fission type) became more susceptible to high-glucose-induced apoptosis and mitochondrial fragmentation observed by TUNEL and mitotracker assays. In siMFN2 HK2 cells (fission type), mitochondria were highly fragmented (>80% fission rate) with or without high-glucose treatment; however, siFIS1 (mitochondrial fission protein 1) HK2 cells (fusion type) exhibited little fragmentation (<13%). High-glucose treatment induced autophagy, characterized by the formation of autophagosome and microtubule-associated protein light chain 3 (LC3) B-II, as observed by transmission electron microscopy and western blotting, respectively. LC3B-II levels decreased in both MFN1(-) and siMFN2 HK2 cells, but increased in siFIS1 HK2 cells. Moreover, autophagy displays a protective role against high-glucose-induced cell death based on cotreatment with autophagy inhibitors (3-methyladenine and chloroquine). Mitochondrial fission may increase apoptosis and decrease autophagy of high-glucose-treated HK2 cells.