Diabetes mellitus impairs CD133+ progenitor cell function after myocardial infarction

Glyoxalase 1 Prevents Chronic Hyperglycemia Induced Heart-Explant Derived Cell Dysfunction

Decades of work have shown that diabetes increases the risk of heart disease and worsens clinical outcomes after myocardial infarction. Because diabetes is an absolute contraindication to heart transplant, cell therapy is increasingly being explored as a means of improving heart function for these patients with very few other options. Given that hyperglycemia promotes the generation of toxic metabolites, the influence of the key detoxification enzyme glyoxalase 1 (Glo1) on chronic hyperglycemia induced heart explant-derived cell (EDC) dysfunction was investigated.

Methods: EDCs were cultured from wild type C57Bl/6 or Glo1 over-expressing transgenic mice 2 months after treatment with the pancreatic beta cell toxin streptozotocin or vehicle. The effects of Glo1 overexpression was evaluated using in vitro and in vivo models of myocardial ischemia.

Results: Chronic hyperglycemia reduced overall culture yields and increased the reactive dicarbonyl cell burden within EDCs. These intrinsic cell changes reduced the angiogenic potential and production of pro-healing exosomes while promoting senescence and slowing proliferation. Compared to intra-myocardial injection of normoglycemic cells, chronic hyperglycemia attenuated cell-mediated improvements in myocardial function and reduced the ability of transplanted cells to promote new blood vessel and cardiomyocyte growth. In contrast, Glo1 overexpression decreased oxidative damage while restoring both cell culture yields and EDC-mediated repair of ischemic myocardium. The latter was associated with enhanced production of pro-healing extracellular vesicles by Glo1 cells without altering the pro-healing microRNA cargo within.

Conclusions: Chronic hyperglycemia decreases the regenerative performance of EDCs. Overexpression of Glo1 reduces dicarbonyl stress and prevents chronic hyperglycemia-induced dysfunction by rejuvenating the production of pro-healing extracellular vesicles.

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

Impaired endothelial progenitor cell mobilization and dysfunctional bone marrow stroma in diabetes mellitus

Background

Circulating Endothelial Progenitor Cell (EPC) levels are reduced in diabetes mellitus. This may be a consequence of impaired mobilization of EPC from the bone marrow. We hypothesized that under diabetic conditions, mobilization of EPC from the bone marrow to the circulation is impaired –at least partly– due to dysfunction of the bone marrow stromal compartment.

Methods

Diabetes was induced in mice by streptozotocin injection. Circulating Sca-1⁺Flk-1⁺ EPC were characterized and quantified by flow cytometry at baseline and after mobilization with G-CSF/SCF injections. In vivo hemangiogenic recovery was tested by 5-FU challenge. Interaction within the bone marrow environment between CD34⁺ hematopoietic progenitor cells (HPC) and supporting stroma was assessed by co-cultures. To study progenitor cell–endothelial cell interaction under normoglycemic and hyperglycemic conditions, a co-culture model using E4Orf1-transfected human endothelial cells was employed.

Results

In diabetic mice, bone marrow EPC levels were unaffected. However, circulating EPC levels in blood were lower at baseline and mobilization was attenuated. Diabetic mice failed to recover and repopulate from 5-FU injection. In vitro, primary cultured bone marrow stroma from diabetic mice was impaired in its capacity to support human CFU-forming HPC. Finally, hyperglycemia hampered the HPC supportive function of endothelial cells in vitro.

Conclusion

EPC mobilization is impaired under experimental diabetic conditions and our data suggest that diabetes induces alterations in the progenitor cell supportive capacity of the bone marrow stroma, which could be partially responsible for the attenuated EPC mobilization and reduced EPC levels observed in diabetic patients.

Apelin-13 increases myocardial progenitor cells and improves repair postmyocardial infarction

Apelin is an endogenous ligand for the angiotensin-like 1 receptor (APJ) and has beneficial effects against myocardial ischemia-reperfusion injury. Little is known about the role of apelin in the homing of vascular progenitor cells (PCs) and cardiac functional recovery postmyocardial infarction (post-MI). The present study investigated whether apelin affects PC homing to the infarcted myocardium, thereby mediating repair and functional recovery post-MI. Mice were infarcted by coronary artery ligation, and apelin-13 (1 mg·kg(-1)·day(-1)) was injected for 3 days before MI and for 14 days post-MI. Homing of vascular PCs [CD133(+)/c-Kit(+)/Sca1(+), CD133(+)/stromal cell-derived factor (SDF)-1α(+), and CD133(+)/CXC chemokine receptor (CXCR)-4(+)] into the ischemic area was examined. Myocardial Akt, endothelial nitric oxide synthase (eNOS), VEGF, jagged1, notch3, SDF-1α, and CXCR-4 expression were assessed at 24 h and 14 days post-MI. Functional analyses were performed on day 14 post-MI. Mice that received apelin-13 treatment demonstrated upregulation of SDF-1α/CXCR-4 expression and dramatically increased the number of CD133(+)/c-Kit(+)/Sca1(+), CD133(+)/SDF-1α(+), and c-Kit(+)/CXCR-4(+) cells in infarcted hearts. Apelin-13 also significantly increased Akt and eNOS phosphorylation and upregulated VEGF, jagged1, and notch3 expression in ischemic hearts. This was accompanied by a significant reduction of myocardial apoptosis. Furthermore, treatment with apelin-13 promoted myocardial angiogenesis and attenuated cardiac fibrosis and hypertrophy together with a significant improvement of cardiac function at 14 days post-MI. Apelin-13 increases angiogenesis and improves cardiac repair post-MI by a mechanism involving the upregulation of SDF-1α/CXCR-4 and homing of vascular PCs.

Overexpression of angiopoietin-1 increases CD133+/c-kit+ cells and reduces myocardial apoptosis in db/db mouse infarcted hearts

Hematopoietic progenitor CD133(+)/c-kit(+) cells have been shown to be involved in myocardial healing following myocardial infarction (MI). Previously we demonstrated that angiopoietin-1(Ang-1) is beneficial in the repair of diabetic infarcted hearts. We now investigate whether Ang-1 affects CD133(+)/c-kit(+) cell recruitment to the infarcted myocardium thereby mediating cardiac repair in type II (db/db) diabetic mice. db/db mice were administered either adenovirus Ang-1 (Ad-Ang-1) or Ad-β-gal systemically immediately after ligation of the left anterior descending coronary artery (LAD). Overexpression of Ang-1 resulted in a significant increase in CXCR-4/SDF-1α expression and promoted CD133(+)/c-kit(+), CD133(+)/CXCR-4(+) and CD133(+)/SDF-1α(+) cell recruitment into ischemic hearts. Overexpression of Ang-1 led to significant increases in number of CD31(+) and smooth muscle-like cells and VEGF expression in bone marrow (BM). This was accompanied by significant decreases in cardiac apoptosis and fibrosis and an increase in myocardial capillary density. Ang-1 also upregulated Jagged-1, Notch3 and apelin expression followed by increases in arteriole formation in the infarcted myocardium. Furthermore, overexpression of Ang-1 resulted in a significant improvement of cardiac functional recovery after 14 days of ischemia. Our data strongly suggest that Ang-1 attenuates cardiac apoptosis and promotes cardiac repair by a mechanism involving in promoting CD133(+)/c-kit(+) cells and angiogenesis in diabetic db/db mouse infarcted hearts.

Cardiovascular comorbidities of type 2 diabetes mellitus: defining the potential of glucagonlike peptide-1-based therapies

The global epidemic of diabetes mellitus (~95% type 2 diabetes) has been fueled by a parallel increase in obesity and overweight. Together, these metabolic disease epidemics have contributed to the increasing incidence and prevalence of cardiovascular disease. The accumulation of metabolic and cardiovascular risk factors in patients with type 2 diabetes--risk factors that may exacerbate one another--complicates treatment. Inadequate treatment, treatment that fails to achieve goals, increases the risk for cardiovascular morbidity and mortality. From a clinical perspective, type 2 diabetes is a cardiovascular disease, an observation that is supported by a range of epidemiologic, postmortem, and cardiovascular imaging studies. Vascular wall dysfunction, and particularly endothelial dysfunction, has been posited as a "common soil" linking dysglycemic and cardiovascular diseases. Vascular wall dysfunction promoted by environmental triggers (e.g., sedentary lifestyle) and metabolic triggers (chronic hyperglycemia, obesity) has been associated with the upregulation of reactive oxygen species and chronic inflammatory and hypercoagulable states, and as such with the pathogenesis of type 2 diabetes, atherosclerosis, and cardiovascular disease. Glucagon-like peptide-1 (GLP)-1, an incretin hormone, and synthetic GLP-1 receptor agonists represent promising new areas of research and therapeutics in the struggle not only against type 2 diabetes but also against the cardiovascular morbidity and mortality associated with type 2 diabetes. In a number of small trials in humans, as well as in preclinical and in vitro studies, both native GLP-1 and GLP-1 receptor agonists have demonstrated positive effects on a range of cardiovascular disease pathologies and clinical targets, including such markers of vascular inflammation as high-sensitivity C-reactive protein, plasminogen activator inhibitor-1, and brain natriuretic peptide. Reductions in markers of dyslipidemia such as elevated levels of triglycerides and free fatty acids have also been observed, as have cardioprotective functions. Larger trials of longer duration will be required to confirm preliminary findings. In large human trials, GLP-1 receptor agonists have been associated with significant reductions in both blood pressure and weight.

Advanced glycation end products induce chemokine/cytokine production via activation of p38 pathway and inhibit proliferation and migration of bone marrow mesenchymal stem cells

Background

Advanced glycation products (AGEs), as endogenous inflammatory mediator, compromise the physiological function of mesenchymal stem cells (MSCs). MSCs have a potential role in cell replacement therapy in acute myocardial infarction and ischemic cardiomyopathy. However, mechanisms of AGEs on MSCs are still not unveiled.

Methods

Reactive oxygen species (ROS), genes regulation, cell proliferation and migration have been detected by AGE-BSA stimulated MSCs.

Results

We found that in vitro stimulation with AGE-BSA induced generation of reactive oxygen species (ROS), and inhibited dose-dependently proliferation and migration of MSCs. Microarray and molecular biological assessment displayed an increased expression and secretion of Ccl2, Ccl3, Ccl4 and Il1b in a dose- and time-dependent manner. These chemokines/cytokines of equivalent concentration to those in conditioned medium exerted an inhibitory effect on MSC proliferation and migration after stimulation for 24 h. Transient elevation of phospho-p38 in MSCs upon AGE-BSA stimulation was blocked with p38 inhibitor.

Conclusions

The study indicates that AGE-BSA induces production of chemokines/cytokines in a dose- and time-dependent manner via activation of ROS-p38 mediated pathway. These chemokines/cytokines exert an inhibitory effect on MSC growth and migration, suggesting an amplified dysfunction of MSCs by AGEs.

Current perspective of pathophysiological and interventional effects on endothelial progenitor cell biology: focus on PI3K/AKT/eNOS pathway

For more than a decade, endothelial progenitor cells (EPCs) have been implicated in cardiovascular homeostasis. EPCs are believed to reside within the bone marrow in close contact with surrounding stromal cells, and, under stimulation of pro-inflammatory cytokines, EPCs are mobilized out of the bone marrow. Hereafter circulating EPCs home to peripheral tissues, undergoing further proliferation and differentiation. Under certain pathophysiologic conditions this process seems to be blunted, resulting in a reduced capacity of EPCs to engage in vasculogenesis at sites of endothelial injury or tissue ischemia. In this review, we focus on the effects of traditional cardiovascular risk factors on EPC biology and we explore whether pharmacological, dietary and lifestyle interventions can favorably restore EPC mobilization, differentiation, homing and angiogenic properties. Because the PI3K/Akt/eNOS pathway plays a pivotal role in the process of EPC mobilization, migration and homing, we specifically emphasize the involvement of PI3K, Akt and eNOS in EPC biology under these different (patho)physiologic conditions. (Pre)clinically used drugs or lifestyle interventions that have been shown to ameliorate EPC biology are reviewed. These treatment strategies remain attractive targets to restore the regenerative capacity of EPCs in cardiovascular diseases.

Endothelial dysfunction in diabetes: potential application of circulating markers as advanced diagnostic and prognostic tools

Endothelial dysfunction is a predisposing factor for vascular disease in diabetes, which contributes significantly to the mortality of diabetic patients. The currently utilized assessment methods of endothelial function/dysfunction in humans are associated with various limitations. Circulating endothelial-derived/associated markers have been proposed as potential alternatives for evaluation of the endothelium in condition of vascular disorders. These indicators include von Willebrand factor, soluble thrombomodulin, soluble E-selectin, asymmetric dimethylarginine, tissue plasminogen activator, endothelial microparticles, circulating endothelial cells and circulating endothelial progenitor cells. While tentative evidence is available for most of these biomarkers to serve as reliable sources of information, their usefulness for routine clinical applications has not yet been established. Thus, circulating endothelial markers are currently the subject of intense research interest and it is anticipated that as more information becomes available their improved quantification will provide a suitable diagnostic and prognostic tool for vascular events in diabetes and related diseases.

Neovascularization in diabetes

Diabetes and its complications are a major public health burden in the developed world. The major cause of diabetic complications is abnormal growth of new blood vessels. This dysfunctional neovascularization results in significant morbidity and mortality in patients with diabetes and, as such, is a major focus of basic and clinical investigation. It has become clear that hyperglycemia disrupts tissue-level signaling in response to hypoxia and ischemia, impairs the vasculogenic potential of circulating stem cells and fundamentally alters the structure and function of key neovascularization proteins, including hypoxia-inducible factor-1. These mechanistic and pathophysiologic studies have revealed new therapeutic targets to restore normal neovascularization and to ameliorate and prevent diabetic vascular complications.

Novel role of NADPH oxidase in angiogenesis and stem/progenitor cell function

Neovascularization is involved in normal development and wound repair as well as ischemic heart disease and peripheral artery disease. Both angiogenesis and vasculogenesis [de novo new vessel formation through mobilization of stem/progenitor cells from bone marrow (BM) and their homing to the ischemic sites] contribute to the formation of new blood vessels after tissue ischemia. Angiogenesis is dependent on cell proliferation, migration, and capillary tube formation in endothelial cells (ECs). Stem/progenitor cells have been used for cell-based therapy to promote revascularization after peripheral or myocardial ischemia. Excess amounts of reactive oxygen species (ROS) are involved in senescence and apoptosis of ECs and stem/progenitor cells, causing defective neovascularization. ROS at low levels function as signaling molecules to mediate cell proliferation, migration, differentiation, and gene expression. NADPH oxidase is one of the major sources of ROS in ECs and stem/progenitor cells, and is activated by various growth factors, cytokines, hypoxia, and ischemia. ROS derived from NADPH oxidase play an important role in redox signaling linked to angiogenesis ECs, as well as stem/progenitor cell mobilization, homing, and differentiation, thereby promoting neovascularization. Understanding these mechanisms may provide insight into NADPH oxidase and its mediators as potential therapeutic targets for ischemic heart and limb disease.