Jason M. Duran

Bone-Derived Stem Cells Repair the Heart after Myocardial Infarction Through Transdifferentiation and Paracrine Signaling Mechanisms

Rationale: Autologous bone marrow–derived or cardiac-derived stem cell therapy for heart disease has demonstrated safety and efficacy in clinical trials, but functional improvements have been limited. Finding the optimal stem cell type best suited for cardiac regeneration is the key toward improving clinical outcomes. Objective: To determine the mechanism by which novel bone-derived stem cells support the injured heart. Methods and Results: Cortical bone–derived stem cells (CBSCs) and cardiac-derived stem cells were isolated from enhanced green fluorescent protein (EGFP+) transgenic mice and were shown to express c-kit and Sca-1 as well as 8 paracrine factors involved in cardioprotection, angiogenesis, and stem cell function. Wild-type C57BL/6 mice underwent sham operation (n=21) or myocardial infarction with injection of CBSCs (n=67), cardiac-derived stem cells (n=36), or saline (n=60). Cardiac function was monitored using echocardiography. Only 2/8 paracrine factors were detected in EGFP+ CBSCs in vivo (basic fibroblast growth factor and vascular endothelial growth factor), and this expression was associated with increased neovascularization of the infarct border zone. CBSC therapy improved survival, cardiac function, regional strain, attenuated remodeling, and decreased infarct size relative to cardiac-derived stem cells– or saline-treated myocardial infarction controls. By 6 weeks, EGFP+ cardiomyocytes, vascular smooth muscle, and endothelial cells could be identified in CBSC-treated, but not in cardiac-derived stem cells–treated, animals. EGFP+ CBSC-derived isolated myocytes were smaller and more frequently mononucleated, but were functionally indistinguishable from EGFP− myocytes. Conclusions: CBSCs improve survival, cardiac function, and attenuate remodeling through the following 2 mechanisms: (1) secretion of proangiogenic factors that stimulate endogenous neovascularization, and (2) differentiation into functional adult myocytes and vascular cells.

Hyperphosphorylation of the Cardiac Ryanodine Receptor at Serine 2808 Is Not Involved in Cardiac Dysfunction After Myocardial Infarction

Rationale: Abnormal behavior of the cardiac ryanodine receptor (RyR2) has been linked to cardiac arrhythmias and heart failure (HF) after myocardial infarction (MI). It has been proposed that protein kinase A (PKA) hyperphosphorylation of the RyR2 at a single residue, Ser-2808, is a critical mediator of RyR dysfunction, depressed cardiac performance, and HF after MI. Objective: We used a mouse model (RyRS2808A) in which PKA hyperphosphorylation of the RyR2 at Ser-2808 is prevented to determine whether loss of PKA phosphorylation at this site averts post MI cardiac pump dysfunction. Methods and Results: MI was induced in wild-type (WT) and S2808A mice. Myocyte and cardiac function were compared in WT and S2808A animals before and after MI. The effects of the PKA activator Isoproterenol (Iso) on L-type Ca2+ current (ICaL), contractions, and [Ca2+]I transients were also measured. Both WT and S2808A mice had depressed pump function after MI, and there were no differences between groups. MI size was also identical in both groups. L type Ca2+ current, contractions, Ca2+ transients, and SR Ca2+ load were also not significantly different in WT versus S2808A myocytes either before or after MI. Iso effects on Ca2+ current, contraction, Ca2+ transients, and SR Ca2+ load were identical in WT and S2808A myocytes before and after MI at both low and high concentrations. Conclusions: These results strongly support the idea that PKA phosphorylation of RyR-S2808 is irrelevant to the development of cardiac dysfunction after MI, at least in the mice used in this study.

Sorafenib Cardiotoxicity Increases Mortality After Myocardial Infarction

Rationale: Sorafenib is an effective treatment for renal cell carcinoma, but recent clinical reports have documented its cardiotoxicity through an unknown mechanism. Objective: Determining the mechanism of sorafenib-mediated cardiotoxicity. Methods and Results: Mice treated with sorafenib or vehicle for 3 weeks underwent induced myocardial infarction (MI) after 1 week of treatment. Sorafenib markedly decreased 2-week survival relative to vehicle-treated controls, but echocardiography at 1 and 2 weeks post MI detected no differences in cardiac function. Sorafenib-treated hearts had significantly smaller diastolic and systolic volumes and reduced heart weights. High doses of sorafenib induced necrotic death of isolated myocytes in vitro, but lower doses did not induce myocyte death or affect inotropy. Histological analysis documented increased myocyte cross-sectional area despite smaller heart sizes after sorafenib treatment, further suggesting myocyte loss. Sorafenib caused apoptotic cell death of cardiac- and bone-derived c-kit+ stem cells in vitro and decreased the number of BrdU+ (5-bromo-2’-deoxyuridine+) myocytes detected at the infarct border zone in fixed tissues. Sorafenib had no effect on infarct size, fibrosis, or post-MI neovascularization. When sorafenib-treated animals received metoprolol treatment post MI, the sorafenib-induced increase in post-MI mortality was eliminated, cardiac function was improved, and myocyte loss was ameliorated. Conclusions: Sorafenib cardiotoxicity results from myocyte necrosis rather than from any direct effect on myocyte function. Surviving myocytes undergo pathological hypertrophy. Inhibition of c-kit+ stem cell proliferation by inducing apoptosis exacerbates damage by decreasing endogenous cardiac repair. In the setting of MI, which also causes large-scale cell loss, sorafenib cardiotoxicity dramatically increases mortality.

Unique Features of Cortical Bone Stem Cells Associated with Repair of the Injured Heart

RATIONALE Adoptive transfer of multiple stem cell types has only had modest effects on the structure and function of failing human hearts. Despite increasing the use of stem cell therapies, consensus on the optimal stem cell type is not adequately defined. The modest cardiac repair and functional improvement in patients with cardiac disease warrants identification of a novel stem cell population that possesses properties that induce a more substantial improvement in patients with heart failure. OBJECTIVE To characterize and compare surface marker expression, proliferation, survival, migration, and differentiation capacity of cortical bone stem cells (CBSCs) relative to mesenchymal stem cells (MSCs) and cardiac-derived stem cells (CDCs), which have already been tested in early stage clinical trials. METHODS AND RESULTS CBSCs, MSCs, and CDCs were isolated from Gottingen miniswine or transgenic C57/BL6 mice expressing enhanced green fluorescent protein and were expanded in vitro. CBSCs possess a unique surface marker profile, including high expression of CD61 and integrin β4 versus CDCs and MSCs. In addition, CBSCs were morphologically distinct and showed enhanced proliferation capacity versus CDCs and MSCs. CBSCs had significantly better survival after exposure to an apoptotic stimuli when compared with MSCs. ATP and histamine induced a transient increase of intracellular Ca(2+) concentration in CBSCs versus CDCs and MSCs, which either respond to ATP or histamine only further documenting the differences between the 3 cell types. CONCLUSIONS CBSCs are unique from CDCs and MSCs and possess enhanced proliferative, survival, and lineage commitment capacity that could account for the enhanced protective effects after cardiac injury.

Does payer status matter in predicting penetrating trauma outcomes

BACKGROUND Few data exist regarding payer status as a predictor of outcomes in penetrating trauma. This study determined whether insurance status impacts in-hospital complications and mortality in gunshot and stab wound patients at our inner-city, level I trauma center. METHODS Penetrating trauma admissions from 2005 to 2009 were reviewed for patient demographics, insurance, Injury Severity Score, complications, duration of stay, and mortality. RESULTS A total of 1,347 penetrating trauma patients were admitted with 652 (48.4%) uninsured. Although uninsured patients were more likely to be male (93.3% vs 89.8%, P = .030), there was no difference in age, ISS, or number of radiologic, operative, or interventional procedures. Uninsured patients had lesser intensive care unit (4.4 vs 3.3 days; P = .049) and total hospital length of stay (10.2 vs 8.3; P = .049). No uninsured patients were placed into a rehabilitation facility at the time of discharge (0.0% vs 1.6%, P < .001). There was no difference in frequency of pulmonary complications, thromboembolic complications, sepsis, urinary tract infection, or wound infections. On multivariate analysis, being uninsured was not an independent predictor of in-hospital complications (1.010, 95% confidence interval 0.703-1.450, P = .959) or mortality (odds ratio 0.905, 95% confidence interval 0.523-1.566, P = .722). CONCLUSION This is the first study to show that penetrating trauma patients who are uninsured have lesser duration of stay and decreased placement into a rehabilitation facility. Being uninsured added no additional risk of in-hospital complications or mortality.

Examining prehospital intubation for penetrating trauma in a swine hemorrhagic shock model.

BACKGROUND: Prehospital intubation does not result in a survival advantage in patients experiencing penetrating trauma, yet resistance to immediate transportation to facilitate access to definitive care remains. An animal model was developed to determine whether intubation provides a survival advantage during severe hemorrhagic shock. We hypothesized that intubation would not provide a survival advantage in potentially lethal hemorrhage. METHODS: After starting a propofol drip, Yorkshire pigs were intubated (n = 6) or given bag‐valve mask ventilation (n = 7) using 100% oxygen. The carotid artery was cannulated with a 14‐gauge catheter, and a Swan‐Ganz catheter was placed under fluoroscopy using a central venous introducer. After obtaining baseline hemodynamic and laboratory data, the animals were exsanguinated through the carotid line until death. The primary end point was time until death, while secondary end points included volume of blood shed, temperature, cardiac index, mean arterial pressure, lactic acid, base excess, and creatinine levels measured in 10‐minute intervals. RESULTS: There was no difference in time until death between the two groups (51.1 [2.5] minutes vs. 48.5 [2.4] minutes, p = 0.52). Intubated animals had greater volume of blood shed at 30 minutes (33.6 [4.4] mL/kg vs. 28.5 [4.3] mL/kg, p = 0.03), 40 minutes (41.7 [4.7] mL/kg vs. 34.9 [3.8] mL/kg, p = 0.04), and 50 minutes (49.2 [8.6] mL/kg vs. 40.2 [1.0] mL/kg, p = 0.001). In addition, the intubated animals were more hypothermic at 40 minutes (35.5°C [0.4°C] vs. 36.7°C [0.2°C], p = 0.01) and had higher lactate levels (2.4 [0.1] mmol/L vs. 1.8 [0.4] mmol/L, p = 0.04) at 10 minutes. Cardiac index (p = 0.66), mean arterial pressure (p = 0.69), base excess (p = 0.14), and creatinine levels (p = 0.37) were not different throughout the shock phase. CONCLUSION: Intubation does not convey a survival advantage in this model of severe hemorrhagic shock. Furthermore, intubation in the setting of severe hemorrhagic shock may result in a more profuse hemorrhage, worse hypothermia, and higher lactate when compared with bag‐valve mask ventilation.

A Review of the Basis of Autologous Stem Cell Therapy for Coronary Artery Disease

Until recently, the myocardium has been viewed as a terminally differentiated organ without potential for regeneration. Although dramatic advances have been made in the treatment of coronary artery disease resulting in greatly improved morbidity and mortality in these patients, further progress in treatment is limited by the inability to repair concomitantly damaged cardiac tissue. This limitation has led to increasing use of stem cell (SC) therapies with the assumption that replacement or repair of damaged vascular and cardiac tissue could lead to improvement in myocardial function. Although multiple experimental animal models and clinical trials of cell-based cardiac therapy have delivered promising results, the mechanisms of their effect are unclear. SC, depending on their lineage, possess the ability to differentiate into cells of various tissues. Although the differentiation of SC into functional cardiomyocytes has been difficult to demonstrate and fraught with controversy, differentiation into functioning endothelium with improved blood flow has been better illustrated and accepted. Studies in animal models have demonstrated improvement in myocardial function after targeted repair of myocardium via implantation of progenitor cells by various delivery methods, whether derived from peripheral blood, bone marrow (BM), umbilical cord blood, or embryonic sources. Here in is a review of the use of autologous SC therapy for coronary artery disease.

A Characterization and Targeting of the Infarct Border Zone in a Swine Model of Myocardial Infarction

Introduction: Novel therapies for myocardial infarction (MI) involving stem cells, gene therapy, biomaterials, or revascularization strategies have shown promise in animal studies and clinical trials, but results have been limited partially due to the injection of therapeutics into ischemic myocardium that cannot support their mechanism of action. Accurate targeting of therapeutics precisely to the infarct border zone (BZ) may be essential for effective repair of the ischemic heart.

The need for standardized protocols for future clinical trials of cell therapy

Multiple clinical trials have been conducted to determine the outcome of stem cell transplantation on cardiac function. However, marked variability in design across these trials has generated ambiguity in interpretation of their results. This review systematically evaluates the currently available protocols to illustrate the need for a standardized protocol for future trials.

Natriuretic Peptides in Heart Failure: Atrial and B-type Natriuretic Peptides

The natriuretic peptides play a vital role in normal physiology and as counter-regulatory hormones in heart failure (HF). Clinical assessment of their levels (for B-type natriuretic peptide [BNP], N-terminal proBNP, and the midregion of N-terminal pro-atrial natriuretic peptide) have become valuable tools in diagnosing patients with HF as well as risk stratifying and guiding therapy. Their roles have further expanded beyond HF to other cardiovascular conditions and for risk stratification in asymptomatic individuals. Understanding the clinical use of these hormones is vital to achieving their full potential.