Everad L. Tilokee

Hyperglycemia Inhibits Cardiac Stem Cell–Mediated Cardiac Repair and Angiogenic Capacity

Background— The impact of diabetes mellitus on the cardiac regenerative potential of cardiac stem cells (CSCs) is unknown yet critical, given that individuals with diabetes mellitus may well require CSC therapy in the future. Using human and murine CSCs from diabetic cardiac tissue, we tested the hypothesis that hyperglycemic conditions impair CSC function. Methods and Results— CSCs cultured from the cardiac biopsies of patients with diabetes mellitus (hemoglobin A1c, 10±2%) demonstrated reduced overall cell numbers compared with nondiabetic sourced biopsies (P=0.04). When injected into the infarct border zone of immunodeficient mice 1 week after myocardial infarction, CSCs from patients with diabetes mellitus demonstrated reduced cardiac repair compared with nondiabetic patients. Conditioned medium from CSCs of patients with diabetes mellitus displayed a reduced ability to promote in vitro blood vessel formation (P=0.02). Similarly, conditioned medium from CSCs cultured from the cardiac biopsies of streptozotocin-induced diabetic mice displayed impaired angiogenic capacity (P=0.0008). Somatic gene transfer of the methylglyoxal detoxification enzyme, glyoxalase-1, restored the angiogenic capacity of diabetic CSCs (diabetic transgenic versus nondiabetic transgenic; P=0.8). Culture of nondiabetic murine cardiac biopsies under high (25 mmol/L) glucose conditions reduced CSC yield (P=0.003), impaired angiogenic (P=0.02) and chemotactic (P=0.003) response, and reduced CSC-mediated cardiac repair (P<0.05). Conclusions— Diabetes mellitus reduces the ability of CSCs to repair injured myocardium. Both diabetes mellitus and preconditioning CSCs in high glucose attenuated the proangiogenic capacity of CSCs. Increased expression of glyoxalase-1 restored the proangiogenic capacity of diabetic CSCs, suggesting a means of reversing diabetic CSC dysfunction by interfering with the accumulation of reactive dicarbonyls.

Paracrine Engineering of Human Cardiac Stem Cells With Insulin‐Like Growth Factor 1 Enhances Myocardial Repair

Background Insulin-like growth factor 1 (IGF-1) activates prosurvival pathways and improves postischemic cardiac function, but this key cytokine is not robustly expressed by cultured human cardiac stem cells. We explored the influence of an enhanced IGF-1 paracrine signature on explant-derived cardiac stem cell–mediated cardiac repair. Methods and Results Receptor profiling demonstrated that IGF-1 receptor expression was increased in the infarct border zones of experimentally infarcted mice by 1 week after myocardial infarction. Human explant-derived cells underwent somatic gene transfer to overexpress human IGF-1 or the green fluorescent protein reporter alone. After culture in hypoxic reduced-serum media, overexpression of IGF-1 enhanced proliferation and expression of prosurvival transcripts and prosurvival proteins and decreased expression of apoptotic markers in both explant-derived cells and cocultured neonatal rat ventricular cardiomyocytes. Transplant of explant-derived cells genetically engineered to overexpress IGF-1 into immunodeficient mice 1 week after infarction boosted IGF-1 content within infarcted tissue and long-term engraftment of transplanted cells while reducing apoptosis and long-term myocardial scarring. Conclusions Paracrine engineering of explant-derived cells to overexpress IGF-1 provided a targeted means of improving cardiac stem cell–mediated repair by enhancing the long-term survival of transplanted cells and surrounding myocardium.

Resident cardiac stem cells and their role in stem cell therapies for myocardial repair.

Despite advances in treatment, heart failure remains one of the top killers in Canada. This recognition motivated a new research focus to harness the fundamental repair properties of the human heart. Since then, cardiac stem cells (CSCs) have emerged as a promising cell candidate to regenerate damaged hearts. The rationale of this approach is simple with ex vivo amplification of CSCs from clinical-grade biopsies, followed by delivery to areas of injury, where they engraft and regenerate the heart. In this review we will summarize recent advances and discuss future developments in CSC-mediated cardiac repair to treat the growing number of Canadians living with and dying from heart failure.

Paracrine Engineering of Human Explant‐Derived Cardiac Stem Cells to Over‐Express Stromal‐Cell Derived Factor 1α Enhances Myocardial Repair

First generation cardiac stem cell products provide indirect cardiac repair but variably produce key cardioprotective cytokines, such as stromal‐cell derived factor 1α, which opens the prospect of maximizing up‐front paracrine‐mediated repair. The mesenchymal subpopulation within explant derived human cardiac stem cells underwent lentiviral mediated gene transfer of stromal‐cell derived factor 1α. Unlike previous unsuccessful attempts to increase efficacy by boosting the paracrine signature of cardiac stem cells, cytokine profiling revealed that stromal‐cell derived factor 1α over‐expression prevented lv‐mediated “loss of cytokines” through autocrine stimulation of CXCR4+ cardiac stem cells. Stromal‐cell derived factor 1α enhanced angiogenesis and stem cell recruitment while priming cardiac stem cells to readily adopt a cardiac identity. As compared to injection with unmodified cardiac stem cells, transplant of stromal‐cell derived factor 1α enhanced cells into immunodeficient mice improved myocardial function and angiogenesis while reducing scarring. Increases in myocardial stromal‐cell derived factor 1α content paralleled reductions in myocyte apoptosis but did not influence long‐term engraftment or the fate of transplanted cells. Transplantation of stromal‐cell derived factor 1α transduced cardiac stem cells increased the generation of new myocytes, recruitment of bone marrow cells, new myocyte/vessel formation and the salvage of reversibly damaged myocardium to enhance cardiac repair after experimental infarction. Stem Cells 2016;34:1826–1835

IGF-1 ENGINEERED HUMAN CARDIAC STEM CELLS PROMOTE REPAIR OF ISCHEMIC MYOCARDIUM BY IMPROVING TRANSPLANT CELL SURVIVAL AND REDUCING MYOCARDIAL APOPTOSIS

the need for comprehensive long-term follow up studies. METHODS: The Canadian Registry of Atrial Fibrillation (CARAF) enrolled patients from 7 centres in Canada at the time of first electrocardiographic diagnosis of AF. Comprehensive clinical and echocardiographic data were collected and patients were followed annually, documenting clinical outcomes, recurrence of PAF, and progression to CAF. Univariate and multivariable Cox proportionate hazards analyses were performed to model the association between baseline clinical, electrocardiographic, and echocardiographic variables and outcomes of stroke and death in patients with AF. RESULTS: A total of 897 patients with non-surgical paroxysmal AF (PAF) were included in the analysis. The medial follow-up time was 8.89 years (interquartile range of 5 to 9.12 years). A total of 268 deaths and 84 strokes occurred during the follow-up period. Univariate analyses identified 13 risk factors that were independently associated with risk of death and 9 risk factors that were independently associated with risk of stroke. Of these risk factors, history of cardiomyopathy, presence of congestive heart failure (CHF), severe mitral regurgitation (MR) and older age had the highest hazard ratios (HR) for occurrence of death (HR 1⁄42.74, 2.61, 2.11 and 2.10, respectively (p<0.001)). The factors were also statistically associated with death in multivariate analysis. Presence of moderate to severe mitral stenosis (MS), cardiomyopathy, increase in left ventricular (LV) posterior wall dimension, CHF and age were highly associated with occurrence of stroke (HR1⁄4 3.99, 3.23, 2.51, 1.94 and 1.73, respectively (p<0.03)). In multivariable analysis, MS, age, And LV posterior wall dimension were associated with stroke. CONCLUSION: In patients with diagnosis of PAF, there are various clinical and echocardiographic risk factors that are independently associated with higher risk of poor outcomes such as death and stroke.

Circulating progenitor cells as a heart failure biomarker: does a failing marrow predict a failing heart?

Innovations in cardiac care have dramatically changed the landscape of patients with heart disease. Many patients are now surviving acute cardiac events but a growing number still suffer irreversible damage and live with the consequences. This chronic heart failure (HF) population often requires close monitoring to adjust therapies and prevent further adverse remodelling in the remaining myocardium. Prediction models based upon the symptom burden (eg, New York Heart Association class, peak oxygen uptake [ _ Vo2]) or structural measures of cardiac function (eg, left ventricular ejection fraction) guide therapeutic decisions, but there is no validated biomarker that participates in and predicts disease progression. Considering emerging evidence which suggests that endothelial dysfunction plays a key role in the progression of chronic HF, 1-3 study of circulating proangiogenic progenitor cells (CPCs) that modulate the capacity of endothelium to regulate inflammation, smooth muscle cell proliferation, thromboresistance, and vascular tone might provide a novel