Progenitor cell dysfunctions underlie some diabetic complications

Photobiomodulation inhibits retinal degeneration in diabetic mice through modulation of stem cell mobilization and gene expression

The number of people suffering from type 2 diabetes (DM2) is increasing and over 30 percent of DM2 patients will develop diabetic retinopathy (DR). Available therapeutic approaches for DR have their limitations. It is of great significance to search for other effective alternate therapeutic approaches. The present study aimed to explore the beneficial effects of photobiomodulation (PBM) on the diabetic retinopathy and underlying mechanisms. Streptozotocin was administered to male mice to establish diabetic model. The mice in the diabetic group (DM) received no treatment, and the mice in DM + PBM group received LED illumination (wavelength 670 nm) once a day for 20 consecutive weeks. Retinal vessel degenerate changes, the expression levels of E-Cadherin, N-Cadherin and the mRNA levels of c-kit, CXCR4, MYPT1, SCF, SDF1-α in retina, the levels of SDF-1α and SCF in the peripheral blood and the number of LSK cells expressing c-kit and sca-1 were determined. PBM could significantly inhibit the degenerative change of diabetic retinal vessels, decrease the expression levels of E-Cadherin and N-Cadherin and the mRNA levels of c-kit, CXCR4, MYPT1, SCF, SDF1-α and increase VEGF mRNA levels in retina. PBM could also increase the levels of SDF-1α and SCF in the peripheral blood and the number of LSK cells expressing c-kit and sca-1 in diabetic mice. PBM at 4 min/day for 20 consecutive weeks significantly inhibit the degenerative change of diabetic retinal vessels, and PBM is likely to produce its beneficial effects on the retina through promoting the migration of bone marrow stem cells to circulation and diabetic retinal tissue. The present study provides a new therapeutic direction and experimental foundation for the treatment of diabetic retinopathy.

Autologous transplantation of green tea epigallocatechin-3-gallate pretreated adipose-derived stem cells increases cardiac regenerative capability through C-X-C motif chemokine receptor 4 expression in the treatment of rats with diabetic cardiomyopathy

Cardiomyopathy is one of complications related to diabetes. Stem cell transplantation shows potential in diabetic cardiomyopathy treatment. Epigallocatechin-3-gallate (EGCG) is one of the major components found in green tea. Although stem cell transplantation and green tea EGCG supplementation show therapeutic effects on cardiomyopathy, the detailed cellular mechanisms in stem cell transplantation coupled with EGCG treatment remain unclear. This study investigates whether adipose-derived stem cells (ADSC) pretreated with EGCG show better protective effect on diabetic cardiomyopathy than ADSC without EGCG pretreatment. A cell model indicated that ADSC pretreated with EGCG increased cell functions including colony formation, migration and survival markers. All of these functions are blocked by small interfering C-X-C motif chemokine receptor 4 (siCXCR4) administration. These findings suggest that ADSC pretreatment with EGCG increases cell functions through CXCR4 expression. A diabetic animal model was designed to verify the above findings, including Sham, DM (diabetes mellitus), DM+ADSC (DM rats receiving autologous transplantation of ADSC) and DM+E-ADSC (DM rats receiving EGCG pretreated ADSC). Compared to the Sham, we found that all of pathophysiological signalings were activated in the DM group, including functional changes (decrease in ejection fraction and fractional shortening), structural changes (disarray and fibrosis) and molecular changes (increases in apoptotic, fibrotic, hypertrophic markers and decreases in survival and longevity markers). E-ADSC (DM+E-ADSC) transplantation shows significant improvement in the above pathophysiological signalings greater than ADSC (DM+ADSC). Therefore, ADSC pretreated with EGCG may contribute to clinical applications for diabetic patients with cardiomyopathy.

Comparison of genetic and epigenetic profiles of periodontitis according to the presence of type 2 diabetes

Type 2 diabetes mellitus (T2DM) and periodontitis (PD) have intricated connections as chronic inflammatory diseases. While the immune response is a key factor that accounts for their association, the underlying mechanisms remain unclear. To gain a deeper understanding of the connection, we conducted research using a multiomics approach. We generated whole genome and methylation profiling array data from the periodontium of PD patients with DM (PDDM) and without DM to confirm genetic and epigenetic changes. Independent bulk and single-cell RNA sequencing data were employed to verify the expression levels of hypo-methylated genes. We observed a gradual rise in C>T base substitutions and hypomethylation in PD and PDDM patients compared with healthy participants. Furthermore, specific genetic and epigenetic alterations were prominently associated with the Fc-gamma receptor-mediated phagocytosis pathway. The upregulation of these genes was confirmed in both the periodontal tissues of PD patients and the pancreatic tissues of T2DM patients. Through single-cell RNA analysis of peripheral blood mononuclear cells, substantial upregulation of Fc-gamma receptors and related genes was particularly identified in monocytes. Our findings suggest that targeting the Fc-gamma signaling pathway in monocytes holds promise as a potential treatment strategy for managing systemic complications associated with diabetes.

Stem cells as a regenerative medicine approach in treatment of microvascular diabetic complications

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by high blood glucose and is associated with high morbidity and mortality among the diabetic population. Uncontrolled chronic hyperglycaemia causes increased formation and accumulation of different oxidative and nitrosative stress markers, resulting in microvascular and macrovascular complications, which might seriously affect the quality of a patient's life. Conventional treatment strategies are confined to controlling blood glucose by regulating the insulin level and are not involved in attenuating the life-threatening complications of diabetes mellitus. Thus, there is an unmet need to develop a viable treatment strategy that could target the multi-etiological factors involved in the pathogenesis of diabetic complications. Stem cell therapy, a regenerative medicine approach, has been investigated in diabetic complications owing to their unique characteristic features of self-renewal, multilineage differentiation and regeneration potential. The present review is focused on potential therapeutic applications of stem cells in the treatment of microvascular diabetic complications such as nephropathy, retinopathy, and polyneuropathy.

Functional carbohydrate-based hydrogels for diabetic wound therapy

Diabetes wound are grave and universal complications of diabetes. Owing to poor treatment course, high amputation rate and mortality, diabetes wound treatment and care have become a global challenge. Wound dressings have received much attention due to their ease of use, good therapeutic effect, and low costs. Among them, carbohydrate-based hydrogels with excellent biocompatibility are considered to be the best candidates for wound dressings. Based on this, we first systematically summarized the problems and healing mechanism of diabetes wounds. Next, common treatment methods and wound dressings were discussed, and the application of various carbohydrate-based hydrogels and their corresponding functionalization (antibacterial, antioxidant, autoxidation and bioactive substance delivery) in the treatment of diabetes wounds were emphatically introduced. Ultimately, the future development of carbohydrate-based hydrogel dressings was proposed. This review aims to provide a deeper understanding of wound treatment and theoretical support for the design of hydrogel dressings.

Tetrahydrocannabivarin (THCV) Protects Adipose-Derived Mesenchymal Stem Cells (ASC) against Endoplasmic Reticulum Stress Development and Reduces Inflammation during Adipogenesis

The endoplasmic reticulum (ER) fulfills essential duties in cell physiology, and impairment of this organelle's functions is associated with a wide number of metabolic diseases. When ER stress is generated in the adipose tissue, it is observed that the metabolism and energy homeostasis of the adipocytes are altered, leading to obesity-associated metabolic disorders such as type 2 diabetes (T2D). In the present work, we aimed to evaluate the protective effects of Δ9-tetrahydrocannabivarin (THCV, a cannabinoid compound isolated from Cannabis sativa L.) against ER stress in adipose-derived mesenchymal stem cells. Our results show that pre-treatment with THCV prevents the subcellular alteration of cell components such as nuclei, F-actin, or mitochondria distribution, and restores cell migration, cell proliferation and colony-forming capacity upon ER stress. In addition, THCV partially reverts the effects that ER stress induces regarding the activation of apoptosis and the altered anti- and pro-inflammatory cytokine profile. This indicates the protective characteristics of this cannabinoid compound in the adipose tissue. Most importantly, our data demonstrate that THCV decreases the expression of genes involved in the unfolded protein response (UPR) pathway, which were upregulated upon induction of ER stress. Altogether, our study shows that the cannabinoid THCV is a promising compound that counters the harmful effects triggered by ER stress in the adipose tissue. This work paves the way for the development of new therapeutic means based on THCV and its regenerative properties to create a favorable environment for the development of healthy mature adipocyte tissue and to reduce the incidence and clinical outcome of metabolic diseases such as diabetes.

Heparin binding proteins on monocyte cell surfaces regulates pre-inflammatory responses in diabetes

Many diabetic complications, such as renal and cardiovascular disease, share a common association with extensive and chronic inflammation due to infiltration by activated leukocytes that originate from the bone marrow (BM). Our previous study demonstrated that macrophage progenitor cells that divided in hyperglycemia induced intracellular synthesis of hyaluronan and became pro-inflammatory macrophages (Mpi), and that the presence of low concentrations of heparin (~50 nM) prevented the intracellular HA synthesis and promoted the formation of tissue repair macrophages (Mtr). However, the molecular mechanism underlying heparin's role is still unknown. This study showed that heparin can be internalized by dividing monocyte progenitor cells. Further, there are two most abundant heparin binding proteins, alpha-enolase (ENO-1) and cofilin-1, identified on monocyte cell surfaces. In addition to their conventional roles inside of cells, ENO-1 and cofilin-1 can be found on cell surfaces and are also involved in autoimmune diseases. Thus, this study provides new insight into heparin's role in regulating monocyte and macrophage function.

Nanobiotechnology: Applications in Chronic Wound Healing

Wounds occur when skin integrity is broken and the skin is damaged. With progressive changes in the disease spectrum, the acute wounds caused by mechanical trauma have been become less common, while chronic wounds triggered with aging, diabetes and infection have become more frequent. Chronic wounds now affect more than 6 million people in the United States, amounting to 10 billion dollars in annual expenditure. However, the treatment of chronic wounds is associated with numerous challenges. Traditional remedies for chronic wounds include skin grafting, flap transplantation, negative-pressure wound therapy, and gauze dressing, all of which can cause tissue damage or activity limitations. Nanobiotechnology — which comprises a diverse array of technologies derived from engineering, chemistry, and biology — is now being applied in biomedical practice. Here, we review the design, application, and clinical trials for nanotechnology-based therapies for chronic wound healing, highlighting the clinical potential of nanobiotechnology in such treatments. By summarizing previous nanobiotechnology studies, we lay the foundation for future wound care via a nanotech-based multifunctional smart system.

Reprograming the immune niche for skin tissue regeneration - From cellular mechanisms to biomaterials applications

Despite the rapid development of therapeutic approaches for skin repair, chronic wounds such as diabetic foot ulcers remain an unaddressed problem that affects millions of people worldwide. Increasing evidence has revealed the crucial and diverse roles of the immune cells in the development and repair of the skin tissue, prompting new research to focus on further understanding and modulating the local immune niche for comprehensive, 'perfect' regeneration. In this review, we first introduce how different immunocytes and certain stromal cells involved in innate and adaptive immunity coordinate to maintain the immune niche and tissue homeostasis, with emphasis on their specific roles in normal and pathological wound healing. We then discuss novel engineering approaches - particularly biomaterials systems and cellular therapies - to target different players of the immune niche, with three major aims to i) overcome 'under-healing', ii) avoid 'over-healing', and iii) promote functional restoration, including appendage development. Finally, we highlight how these strategies strive to manage chronic wounds and achieve full structural and functional skin recovery by creating desirable 'soil' through modulating the immune microenvironment.

Transmembrane stem cell factor protein therapeutics enhance revascularization in ischemia without mast cell activation

Stem cell factor (SCF) is a cytokine that regulates hematopoiesis and other biological processes. While clinical treatments using SCF would be highly beneficial, these have been limited by toxicity related to mast cell activation. Transmembrane SCF (tmSCF) has differential activity from soluble SCF and has not been explored as a therapeutic agent. We created novel therapeutics using tmSCF embedded in proteoliposomes or lipid nanodiscs. Mouse models of anaphylaxis and ischemia revealed the tmSCF-based therapies did not activate mast cells and improved the revascularization in the ischemic hind limb. Proteoliposomal tmSCF preferentially acted on endothelial cells to induce angiogenesis while tmSCF nanodiscs had greater activity in inducing stem cell mobilization and recruitment to the site of injury. The type of lipid nanocarrier used altered the relative cellular uptake pathways and signaling in a cell type dependent manner. Overall, we found that tmSCF-based therapies can provide therapeutic benefits without off target effects.

Calystegines Improve the Metabolic Activity of Human Adipose Derived Stromal Stem Cells (ASCs) under Hyperglycaemic Condition through the Reduction of Oxidative/ER Stress, Inflammation, and the Promotion of the AKT/PI3K/mTOR Pathway

Hyperglycaemia and its resulting glucotoxicity are among the most prominent hallmarks of diabetes mellitus (DM) development. Persistent hyperglycaemia further leads to oxidative stress via mitochondrial dysfunction and subsequent ER stress onset, while associated hyperlipidaemia triggers the adipose tissue to secrete pro-inflammatory cytokines. In this study, the effect of calystegines has been investigated in an experimental model of hyperglycaemia induced on human ASCs cells. Different cellular pathways including apoptosis, oxidative and ER stress, inflammation as well as Pi3K/AKT/mTOR metabolic-associated axis have been evaluated by means on RT-qPCR, western blot, and flow cytometry techniques. Treatment of HuASCs cells with calystegines strongly promoted the hyperglycaemic cells survival and significantly diminished oxidative stress, mitochondrial dynamics failure and ER stress, while improving the endogenous cellular antioxidant defenses. Interestingly, nortropane alkaloids efficiently prevented the hyperglycaemia-mediated inflammatory response, as evidenced by the regulation of the pro- and anti-inflammatory response in HuASCs cells. Finally, we evidenced that calystegines may exert their protective effect on HuASCs cells metabolic functions through the restoration of the defective PI3K/AKT/mTOR pathway. Overall, the present investigation demonstrated that calystegines possess important abilities to protect HuASCs against hyperglycaemia-induced cellular dysfunction, and it evidenced that the observed effects are associated to the promotion of PI3K/AKT/mTOR pathway.

Identification of molecular pathways and protein-protein interactions in adipose tissue-derived mesenchymal stromal cells (ASCs) under physiological oxygen concentration in a diabetic rat model

Objectives

Adipose tissue-derived mesenchymal stromal cells (ASCs) are useful in cell-based therapy. However, it is well known that diabetes mellitus (DM) alters ASCs' functionality. The majority of in vitro studies related to ASCs are developed under non-physiological oxygen conditions. Therefore, they may not reflect the full effects of DM on ASCs, in vivo. The main aim of the current study is to identify molecular pathways and underlying biological mechanisms affected by diabetes on ASCs in physiological oxygen conditions.

Materials and Methods

ASCs derived from healthy (ASCs-C) and diabetic (ASCs-D) rats were expanded under standard culture conditions (21% O2) or cultured in physiological oxygen conditions (3% O2) and characterized. Differential gene expressions (DEGs) of ASCs-D with respect to ASCs-C were identified and analyzed with bioinformatic tools. Protein-protein interaction (PPI) networks, from up- and down-regulated DEGs, were also constructed.

Results

The bioinformatic analysis revealed 1354 up-regulated and 859 down-regulated DEGs in ASCs-D, with 21 and 78 terms over and under-represented, respectively. Terms linked with glycosylation and ribosomes were over-represented and terms related to the activity of RNA-polymerase II and transcription regulation were under-represented. PPI network disclosed RPL11-RPS5 and KDR-VEGFA as the main interactions from up- and down-regulated DEGs, respectively.

Conclusion

These results provide valuable information about gene pathways and underlying molecular mechanisms by which diabetes disturbs ASCs biology in physiological oxygen conditions. Furthermore, they reveal, molecular targets to improve the use of ASCs in autologous transplantation.

Diabetic pregnancy as a novel risk factor for cardiac dysfunction in the offspring-the heart as a target for fetal programming in rats

AIMS/HYPOTHESIS

The impact of diabetic pregnancy has been investigated extensively regarding offspring metabolism; however, little is known about the influence on the heart. We aimed to characterise the effects of a diabetic pregnancy on male adult offspring cardiac health after feeding a high-fat diet in an established transgenic rat model.

METHODS

We applied our rat model for maternal type 2 diabetes characterised by maternal insulin resistance with hyperglycaemia and hyperinsulinaemia. Diabetes was induced preconceptionally via doxycycline-induced knock down of the insulin receptor in transgenic rats. Male wild-type offspring of diabetic and normoglycaemic pregnancies were raised by foster mothers, followed up into adulthood and subgroups were challenged by a high-fat diet. Cardiac phenotype was assessed by innovative speckle tracking echocardiography, circulating factors, immunohistochemistry and gene expression in the heart.

RESULTS

When feeding normal chow, we did not observe differences in cardiac function, gene expression and plasma brain natriuretic peptide between adult diabetic or normoglycaemic offspring. Interestingly, when being fed a high-fat diet, adult offspring of diabetic pregnancy demonstrated decreased global longitudinal (-14.82 ± 0.59 vs -16.60 ± 0.48%) and circumferential strain (-23.40 ± 0.57 vs -26.74 ± 0.34%), increased relative wall thickness (0.53 ± 0.06 vs 0.37 ± 0.02), altered cardiac gene expression, enlarged cardiomyocytes (106.60 ± 4.14 vs 87.94 ± 1.67 μm), an accumulation of immune cells in the heart (10.27 ± 0.30 vs 6.48 ± 0.48 per fov) and higher plasma brain natriuretic peptide levels (0.50 ± 0.12 vs 0.12 ± 0.03 ng/ml) compared with normoglycaemic offspring on a high-fat diet. Blood pressure, urinary albumin, blood glucose and body weight were unaltered between groups on a high-fat diet.

CONCLUSIONS/INTERPRETATION

Diabetic pregnancy in rats induces cardiac dysfunction, left ventricular hypertrophy and altered proinflammatory status in adult offspring only after a high-fat diet. A diabetic pregnancy itself was not sufficient to impair myocardial function and gene expression in male offspring later in life. This suggests that a postnatal high-fat diet is important for the development of cardiac dysfunction in rat offspring after diabetic pregnancy. Our data provide evidence that a diabetic pregnancy is a novel cardiac risk factor that becomes relevant when other challenges, such as a high-fat diet, are present.

Nanotransfection-based vasculogenic cell reprogramming drives functional recovery in a mouse model of ischemic stroke

Ischemic stroke causes vascular and neuronal tissue deficiencies that could lead to substantial functional impairment and/or death. Although progenitor-based vasculogenic cell therapies have shown promise as a potential rescue strategy following ischemic stroke, current approaches face major hurdles. Here, we used fibroblasts nanotransfected with Etv2, Foxc2, and Fli1 (EFF) to drive reprogramming-based vasculogenesis, intracranially, as a potential therapy for ischemic stroke. Perfusion analyses suggest that intracranial delivery of EFF-nanotransfected fibroblasts led to a dose-dependent increase in perfusion 14 days after injection. MRI and behavioral tests revealed ~70% infarct resolution and up to ~90% motor recovery for mice treated with EFF-nanotransfected fibroblasts. Immunohistological analysis confirmed increases in vascularity and neuronal cellularity, as well as reduced glial scar formation in response to treatment with EFF-nanotransfected fibroblasts. Together, our results suggest that vasculogenic cell therapies based on nanotransfection-driven (i.e., nonviral) cellular reprogramming represent a promising strategy for the treatment of ischemic stroke.

Diabetes impairs periosteal progenitor regenerative potential

Diabetics are at increased risk for fracture, and experience severely impaired skeletal healing characterized by delayed union or nonunion of the bone. The periosteum harbors osteochondral progenitors that can differentiate into chondrocytes and osteoblasts, and this connective tissue layer is required for efficient fracture healing. While bone marrow-derived stromal cells have been studied extensively in the context of diabetic skeletal repair and osteogenesis, the effect of diabetes on the periosteum and its ability to contribute to bone regeneration has not yet been explicitly evaluated. Within this study, we utilized an established murine model of type I diabetes to evaluate periosteal cell differentiation capacity, proliferation, and availability under the effect of a diabetic environment. Periosteal cells from diabetic mice were deficient in osteogenic differentiation ability in vitro, and diabetic mice had reduced periosteal populations of mesenchymal progenitors with a corresponding reduction in proliferation capacity following injury. Additionally, fracture callus mineralization and mature osteoblast activity during periosteum-mediated healing was impaired in diabetic mice compared to controls. We propose that the effect of diabetes on periosteal progenitors and their ability to aid in skeletal repair directly impairs fracture healing.

Abnormal DNA Methylation Induced by Hyperglycemia Reduces CXCR 4 Gene Expression in CD 34+ Stem Cells

Background CD 34⁺ stem/progenitor cells are involved in vascular homeostasis and in neovascularization of ischemic tissues. The number of circulating CD 34⁺ stem cells is a predictive biomarker of adverse cardiovascular outcomes in diabetic patients. Here, we provide evidence that hyperglycemia can be "memorized" by the stem cells through epigenetic changes that contribute to onset and maintenance of their dysfunction in diabetes mellitus. Methods and Results Cord-blood-derived CD 34⁺ stem cells exposed to high glucose displayed increased reactive oxygen species production, overexpression of p66^shc gene, and downregulation of antioxidant genes catalase and manganese superoxide dismutase when compared with normoglycemic cells. This altered oxidative state was associated with impaired migration ability toward stromal-cell-derived factor 1 alpha and reduced protein and mRNA expression of the C-X-C chemokine receptor type 4 ( CXCR 4) receptor. The methylation analysis by bisulfite Sanger sequencing of the CXCR 4 promoter revealed a significant increase in DNA methylation density in high-glucose CD 34⁺ stem cells that negatively correlated with mRNA expression (Pearson r=-0.76; P=0.004). Consistently, we found, by chromatin immunoprecipitation assay, a more transcriptionally inactive chromatin conformation and reduced RNA polymerase II engagement on the CXCR 4 promoter. Notably, alteration of CXCR 4 DNA methylation, as well as transcriptional and functional defects, persisted in high-glucose CD 34⁺ stem cells despite recovery in normoglycemic conditions. Importantly, such an epigenetic modification was thoroughly confirmed in bone marrow CD 34⁺ stem cells isolated from sternal biopsies of diabetic patients undergoing coronary bypass surgery. Conclusions CD 34⁺ stem cells "memorize" the hyperglycemic environment in the form of epigenetic modifications that collude to alter CXCR 4 receptor expression and migration.

Early Intervention in Ischemic Tissue with Oxygen Nanocarriers Enables Successful Implementation of Restorative Cell Therapies

Background

Tissue ischemia contributes to necrosis and infection. While angiogenic cell therapies have emerged as a promising strategy against ischemia, current approaches to cell therapies face multiple hurdles. Recent advances in nuclear reprogramming could potentially overcome some of these limitations. However, under severely ischemic conditions necrosis could outpace reprogramming-based repair. As such, adjunctive measures are required to maintain a minimum level of tissue viability/activity for optimal response to restorative interventions.

Methods

Here we explored the combined use of polymerized hemoglobin (PolyHb)-based oxygen nanocarriers with Tissue Nano-Transfection (TNT)-driven restoration to develop tissue preservation/repair strategies that could potentially be used as a first line of care. Random-pattern cutaneous flaps were created in a mouse model of ischemic injury. PolyHbs with high and low oxygen affinity were synthesized and injected into the tissue flap at various timepoints of ischemic injury. The degree of tissue preservation was evaluated in terms of perfusion, oxygenation, and resulting necrosis. TNT was then used to deploy reprogramming-based vasculogenic cell therapies to the flaps via nanochannels. Reprogramming/repair outcomes were evaluated in terms of vascularity and necrosis.

Results

Flaps treated with PolyHbs exhibited a gradual decrease in necrosis as a function of time-to-intervention, with low oxygen affinity PolyHb showing the best outcomes. TNT-based intervention of the flap in combination with PolyHb successfully curtailed advanced necrosis compared to flaps treated with only PolyHb or TNT alone.

Conclusions

These results indicate that PolyHb and TNT technologies could potentially be synergistically deployed and used as early intervention measures to combat severe tissue ischemia.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Full title: High glucose protects mesenchymal stem cells from metformin-induced apoptosis through the AMPK-mediated mTOR pathway

Micro- and macro-vascular events are directly associated with hyperglycemia in patients with type 2 diabetes mellitus (T2DM), but whether intensive glucose control decreases the risk of diabetic cardiovascular complications remains uncertain. Many studies have confirmed that impaired quality and quantity of mesenchymal stem cells (MSCs) plays a pathogenic role in diabetes. Our previous study found that the abundance of circulating MSCs was significantly decreased in patients with T2DM, which was correlated with the progression of diabetic complications. In addition, metformin-induced MSC apoptosis is one of the reasons for the decreased quantity of endogenous or exogenous MSCs during intensive glucose control. However, the role of glucose in metformin-induced MSC apoptosis during intensive glucose control in T2DM remains unknown. In this study, we found that metformin induces MSC apoptosis during intensive glucose control, while high glucose (standard glucose control) could significantly reverse its adverse effect in an AMPK-mTOR pathway dependent manner. Thus, our results indicate that the poorer clinical benefit of the intensive glucose control strategy may be related to an adverse effect due to metformin-induced MSC apoptosis during intensive glucose control therapy in patients with T2DM.

Diabetes induces myeloid bias in bone marrow progenitors associated with enhanced wound macrophage accumulation and impaired healing

Diabetes induces dysregulation throughout the spectrum of myeloid lineage cells from progenitors to terminally differentiated cells. Another complication of diabetes is persistent inflammation, including prolonged accumulation of macrophages, which contributes to impaired wound healing. However, it remains unclear whether diabetes disrupts the response of bone marrow progenitors to peripheral injury and whether such dysregulation leads to sustained inflammation and impaired healing. Here, we demonstrated that diabetic mice (db/db, referred to here as DB) exhibit myeloid lineage bias during homeostasis and following injury. In addition, cells in the LSK (Lin^- Sca-1⁺ cKit⁺ ) population of DB mice are preprogrammed towards myeloid commitment at the transcriptional level, and cultured myeloid progenitors from DB mice produce more monocytes ex vivo than their non-diabetic counterparts. We also show via bone marrow transfer between interleukin-1 receptor 1 KO (Il1r1^-/- ) and DB mice that IL-1R1 signaling is likely not involved in myeloid skewing in DB mice. Furthermore, in vitro experiments indicated that macrophage colony-stimulating factor receptor signaling is not likely involved in enhanced myeloid transcription factor expression in LSK cells of DB mice. Our findings indicate that myeloid lineage commitment in bone marrow may contribute to increased macrophage numbers observed in diabetic skin wounds, and that strategies to regulate monopoiesis during homeostasis or post-wounding may improve diabetic wound healing. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Hexokinase-2 Glycolytic Overload in Diabetes and Ischemia-Reperfusion Injury

Hexokinase-2 (HK2) was recently found to produce increased metabolic flux through glycolysis in hyperglycemia without concurrent transcriptional or other functional regulation. Rather, stabilization to proteolysis by increased glucose substrate binding produced unscheduled increased glucose metabolism in response to high cytosolic glucose concentration. This produces abnormal increases in glycolytic intermediates or glycolytic overload, driving cell dysfunction and vulnerability to the damaging effects of hyperglycemia in diabetes, explaining tissue-specific pathogenesis. Glycolytic overload is also activated in ischemia-reperfusion injury and cell senescence. A further key feature is HK2 displacement from mitochondria by increased glucose-6-phosphate concentration, inducing mitochondrial dysfunction and oxidative stress. This pathogenic mechanism suggested new targets for therapeutics development that gave promising outcomes in initial clinical evaluation.

Peritoneal macrophages have an impaired immune response in obesity which can be reversed by subsequent weight loss

INTRODUCTION

Obesity is recognized as a risk factor for various microbial infections. The immune system, which is affected by obesity, plays an important role in the pathophysiology of these infections and other obesity-related comorbidities. Weight loss is considered the most obvious treatment for obesity. However, multiple studies suggest that the comorbidities of obesity may persist after weight loss. Deregulation of immune cells including adipose tissue macrophages of obese individuals has been extensively studied, but how obesity and subsequent weight loss affect immune cell function outside adipose tissue is not well defined.

RESEARCH DESIGN AND METHODS

Here we investigated the phenotype of non-adipose tissue macrophages by transcriptional characterization of thioglycollate-elicited peritoneal macrophages (PM) from mice with diet-induced obesity and type 2 diabetes (T2D). Subsequently, we defined the characteristics of PMs after weight loss and mimicked a bacterial infection by exposing PMs to lipopolysaccharide.

RESULTS AND CONCLUSIONS

In contrast to the proinflammatory phenotype of adipose tissue macrophages in obesity and T2D, we found a deactivated state of PMs in obesity and T2D. Weight loss could reverse this deactivated macrophage phenotype. Anti-inflammatory characteristics of these non-adipose macrophages may explain why patients with obesity and T2D have an impaired immune response against pathogens. Our data also suggest that losing weight restores macrophage function and thus contributes to the reduction of immune-related comorbidities in patients.

Wound Healing: A Cellular Perspective

Wound healing is one of the most complex processes in the human body. It involves the spatial and temporal synchronization of a variety of cell types with distinct roles in the phases of hemostasis, inflammation, growth, re-epithelialization, and remodeling. With the evolution of single cell technologies, it has been possible to uncover phenotypic and functional heterogeneity within several of these cell types. There have also been discoveries of rare, stem cell subsets within the skin, which are unipotent in the uninjured state, but become multipotent following skin injury. Unraveling the roles of each of these cell types and their interactions with each other is important in understanding the mechanisms of normal wound closure. Changes in the microenvironment including alterations in mechanical forces, oxygen levels, chemokines, extracellular matrix and growth factor synthesis directly impact cellular recruitment and activation, leading to impaired states of wound healing. Single cell technologies can be used to decipher these cellular alterations in diseased states such as in chronic wounds and hypertrophic scarring so that effective therapeutic solutions for healing wounds can be developed.

Metformin induces apoptosis in mesenchymal stromal cells and dampens their therapeutic efficacy in infarcted myocardium

BACKGROUND

Cardiovascular complications, especially myocardial infarctions (MIs), are the leading mortality cause in diabetic patients. The transplantation of stem cells into damaged hearts has had considerable success as a treatment for MI, although whether antidiabetic drugs affect the therapeutic efficacy of stem cell transplantation is still unknown. This study aims to understand whether and how metformin, one of the first-line drugs used to treat type 2 diabetes mellitus (T2DM), induces mesenchymal stromal cell (MSC) apoptosis and dampens their cardioprotective effect after transplantation into infarcted hearts.

METHODS

A mouse MI model was generated via permanent ligation of the left anterior descending (LAD) coronary artery. MSCs with or without metformin treatment were transplanted after MI in diabetic mice. Echocardiography was used to assess cardiac function and determine cardiac remodeling, and TTC staining was performed to evaluate infarction size. A mouse gavage model was performed to evaluate bone marrow MSCs for flow cytometry assay.

RESULTS

Metformin dampened MSC therapeutic efficacy, which increased infarct size and restricted functional cardiac recovery. Specifically, metformin induced the activation of AMP-activated protein kinase (AMPK)-mediated apoptosis through the inhibition of S6K1-Bad-Bcl-xL cell survival signaling, resulting in the upregulated expression of apoptosis-associated proteins and increased MSC apoptosis. Accordingly, counteracting AMPK attenuated metformin-induced apoptosis in MSCs and partially restored their cardioprotective effects in diabetic mice with MI. Furthermore, a decrease in peripheral blood MSCs was found in patients with T2DM who had a metformin medication history.

CONCLUSIONS

Our results highlight an unexpected adverse effect of metformin-induced MSC apoptosis through AMPK-mediated mTOR suppression, which is attenuated by an AMPK inhibitor. Moreover, AMPK inhibition may be a novel strategy for enhancing the effectiveness of stem cell therapy after MI in diabetes.

Regenerative medicine and war: a front-line focus for UK defence

The recent prolonged conflicts in Iraq and Afghanistan saw the advancement of deployed trauma care to a point never before seen in war. The rapid translation of lessons from combat casualty care research, facilitated by an appetite for risk, contributed to year-on-year improvements in care of the injured. These paradigms, however, can only ever halt the progression of damage. Regenerative medicine approaches, in contrast, hold a truly disruptive potential to go beyond the cessation of damage from blast or ballistic trauma, to stimulate its reversal, and to do so from a very early point following injury. The internationally distributed and, in parts austere environments in which operational medical care is delivered provide an almost unique challenge to the development and translation of regenerative medicine technologies. In parallel, however, an inherent appetite for risk means that Defence will always be an early adopter. In focusing our operational priorities for regenerative medicine, the authors conducted a review of the current research landscape in the UK and abroad and sought wide clinical opinion. Our priorities are all applicable very far forward in the patient care pathway, and are focused on three broad and currently under-researched areas, namely: (a) blood, as an engineered tissue; (b) the mechanobiology of deep tissue loss and mechanobiological approaches to regeneration, and; (c) modification of the endogenous response. In focusing on these areas, we hope to engender the development of regenerative solutions for improved functional recovery from injuries sustained in conflict.

High glucose condition limited the angiogenic/cardiogenic capacity of murine cardiac progenitor cells in in vitro and in vivo milieu

Murine c-kit⁺ cardiac cells were isolated and enriched by magnetic activated cell sorting technique. c-kit⁺ cells viability and colony-forming activity were evaluated by MTT and clonogenic assay. c-kit⁺ cells were exposed to endothelial, pericyte, and cardiomyocyte induction media containing 30mM glucose for 7 days. We monitored the level of endothelial (VE-cadherin, CD31, and vWF), pericyte (NG₂ , α-SMA, and PDGFR-β), and cardiomyocyte markers (cTnT) using flow cytometry, real-time Polymerase Chain Reaction (PCR), and Enzyme-Linked Immunosorbent Assay (ELISA) analyses. Ultrastructural changes were studied by transmission electron microscopy (TEM) in cells treated with 5-Azacytidine and 30mM glucose. Matrigel plug assay was performed to determine the angio/cardiogenic property of c-kit⁺ cells in a diabetic mouse model. Glucose of 30mM decreased c-kit⁺ cells viability and clonogenicity (P < 0.05). The transdifferentiation capacity of c-kit⁺ cells into the endothelial lineage, pericytes, and cardiomyocytes were reduced through the inhibition of related genes (P < 0.05). TEM analysis revealed cardiomyocyte differentiation rate in c-kit⁺ cells coincided with an increased intracellular lipid accumulation and reduced number of mitochondria. Similar to in vitro condition, the angiogenic capacity of c-kit⁺ cells was aborted in vivo indicated by reduced NG₂ , α-SMA, CD31, and vWF levels. High glucose condition reduces the angio/cardiogenic capacity of cardiac c-kit⁺ cells in vitro and in vivo. SIGNIFICANCE OF THE STUDY: High glucose condition seen in diabetes mellitus could affect the regenerative potential of cardiac tissue. The current experiment showed that the exposure of murine cardiac progenitor cells (CD117⁺ cells) to condition containing 30mM glucose could decrease the differentiation properties into endothelial cells, pericytes, and mature cardiomyocytes in vitro and in vivo. Our finding confirmed that the angiogenic/cardiogenic potential cardiac progenitor cells decrease under treatment with high glucose content as seen in the diabetic condition.

Preclinical Assessment of the Proliferation Capacity of Gingival and Periodontal Ligament Stem Cells from Diabetic Patients

BACKGROUND:

Stem cells have recently received great interest as potential therapeutics alternative for a variety of diseases. The oral and maxillofacial region, in particular, encompasses a variety of distinctive mesenchymal (MSC) populations and is characterized by a potent multilineage differentiation capacity.

AIM:

In this report, we aimed to investigate the effect of diabetes on the proliferation potential of stem cells isolated from controlled diabetic patients (type 2) and healthy individuals.

SUBJECTS & METHODS:

The proliferation rate of gingival and periodontal derived stem cells isolated from diabetic & healthy individuals were compared using MTT Assay. Expression levels of Survivin in isolated stem cells from all groups were measured by qRt - PCR.

RESULTS:

There was a significantly positive correlation between proliferation rate and expression of Survivin in all groups which sheds light on the importance of Survivin as a reliable indicator of proliferation. The expression of Survivin further confirmed the proliferation results from MTT Assay where the expression of stem cells from non - diabetic individuals was higher than diabetic patients.

CONCLUSION:

Taking together all the results, it could be concluded that PDLSC and GSC are promising candidates for autologous regenerative therapy due to their ease of accessibility in addition to their high proliferative rates.

Complement C5a induces mesenchymal stem cell apoptosis during the progression of chronic diabetic complications

AIMS/HYPOTHESIS

Regeneration and repair mediated by mesenchymal stem cells (MSCs) are key self-protection mechanisms against diabetic complications, a reflection of diabetes-related cell/tissue damage and dysfunction. MSC abnormalities have been reported during the progression of diabetic complications, but little is known about whether a deficiency in these cells plays a role in the pathogenesis of this disease. In addition to MSC resident sites, peripheral circulation is a major source of MSCs that participate in the regeneration and repair of damaged tissue. Therefore, we investigated whether there is a deficiency of circulating MSC-like cells in people with diabetes and explored the underlying mechanisms.

METHODS

The abundance of MSC-like cells in peripheral blood was evaluated by FACS. Selected diabetic and non-diabetic serum (DS and NDS, respectively) samples were used to mimic diabetic and non-diabetic microenvironments, respectively. The proliferation and survival of MSCs under different serum conditions were analysed using several detection methods. The survival of MSCs in diabetic microenvironments was also investigated in vivo using leptin receptor mutant (Lepr db/db ) mice.

RESULTS

Our data showed a significant decrease in the abundance of circulating MSC-like cells, which was correlated with complications in individuals with type 2 diabetes. DS strongly impaired the proliferation and survival of culture-expanded MSCs through the complement system but not through exposure to high glucose levels. DS-induced MSC apoptosis was mediated, at least in part, by the complement C5a-dependent upregulation of Fas-associated protein with death domain (FADD) and the Bcl-2-associated X protein (BAX)/B cell lymphoma 2 (Bcl-2) ratio, which was significantly inhibited by neutralising C5a or by the pharmacological or genetic inhibition of the C5a receptor (C5aR) on MSCs. Moreover, blockade of the C5a/C5aR pathway significantly inhibited the apoptosis of transplanted MSCs in Lepr db/db recipient mice.

CONCLUSIONS/INTERPRETATION

C5a-dependent apoptotic death is probably involved in MSC deficiency and in the progression of complications in individuals with type 2 diabetes. Therefore, anticomplement therapy may be a novel intervention for diabetic complications.

Expanding horizons of cellular plasticity in regenerative medicine

This Guest Editorial introduces the Regenerative Medicine Theme Issue, which provides critical insight into the unfolding frontier of regenerative medicine.