Anthony J. White

Validation of the Cardiosphere Method to Culture Cardiac Progenitor Cells from Myocardial Tissue

Background At least four laboratories have shown that endogenous cardiac progenitor cells (CPCs) can be grown directly from adult heart tissue in primary culture, as cardiospheres or their progeny (cardiosphere-derived cells, CDCs). Indeed, CDCs are already being tested in a clinical trial for cardiac regeneration. Nevertheless, the validity of the cardiosphere strategy to generate CPCs has been called into question by reports based on variant methods. In those reports, cardiospheres are argued to be cardiomyogenic only because of retained cardiomyocytes, and stem cell activity has been proposed to reflect hematological contamination. We use a variety of approaches (including genetic lineage tracing) to show that neither artifact is applicable to cardiospheres and CDCs grown using established methods, and we further document the stem cell characteristics (namely, clonogenicity and multilineage potential) of CDCs. Methodology/Principal Findings CPCs were expanded from human endomyocardial biopsies (n = 160), adult bi-transgenic MerCreMer-Z/EG mice (n = 6), adult C57BL/6 mice (n = 18), adult GFP+ C57BL/6 transgenic mice (n = 3), Yucatan mini pigs (n = 67), adult SCID beige mice (n = 8), and adult Wistar-Kyoto rats (n = 80). Cellular yield was enhanced by collagenase digestion and process standardization; yield was reduced in altered media and in specific animal strains. Heparinization/retrograde organ perfusion did not alter the ability to generate outgrowth from myocardial sample. The initial outgrowth from myocardial samples was enriched for sub-populations of CPCs (c-Kit+), endothelial cells (CD31+, CD34+), and mesenchymal cells (CD90+). Lineage tracing using MerCreMer-Z/EG transgenic mice revealed that the presence of cardiomyocytes in the cellular outgrowth is not required for the generation of CPCs. Rat CDCs are shown to be clonogenic, and cloned CDCs exhibit spontaneous multineage potential. Conclusions/Significance This study demonstrates that direct culture and expansion of CPCs from myocardial tissue is simple, straightforward, and reproducible when appropriate techniques are used.

Intramyocardial Injection of Autologous Cardiospheres or Cardiosphere-Derived Cells Preserves Function and Minimizes Adverse Ventricular Remodeling in Pigs With Heart Failure Post-Myocardial Infarction

OBJECTIVES The purpose of this study was to test the safety and efficacy of direct injection of cardiosphere-derived cells (CDCs) and their 3-dimensional precursors, cardiospheres, for cellular cardiomyoplasty in a mini-pig model of heart failure after myocardial infarction. BACKGROUND Intracoronary administration of CDCs has been demonstrated to reduce infarct size and improve hemodynamic indexes in the mini-pig model, but intramyocardial injection of CDCs or cardiospheres has not been assessed in large animals. METHODS Autologous cardiospheres or CDCs grown from endomyocardial biopsies were injected through thoracotomy 4 weeks after anteroseptal myocardial infarction. Engraftment optimization with luciferase-labeled CDCs guided the choice of cell dose (0.5 million cells/site) and target tissue (20 peri-infarct sites). Pigs were randomly allocated to placebo (n = 11), cardiospheres (n = 8), or CDCs (n = 10). Functional data were acquired before injection and again 8 weeks later, after which organs were harvested for histopathology. RESULTS Beyond the immediate perioperative period, all animals survived to protocol completion. Ejection fraction was equivalent at baseline, but at 8 weeks was higher than placebo in both of the cell-treated groups (placebo vs. CDC, p = 0.01; placebo vs. cardiospheres, p = 0.01). Echocardiographic and hemodynamic indexes of efficacy improved disproportionately with cardiospheres; likewise, adverse remodeling was more attenuated with cardiospheres than with CDCs. Provocative electrophysiologic testing showed no differences among groups, and no tumors were found. CONCLUSIONS Dosage-optimized direct injection of cardiospheres or CDCs is safe and effective in preserving ventricular function in porcine ischemic cardiomyopathy. Although CDCs and cardiospheres have equivalent effects on left ventricular ejection fraction, cardiospheres are superior in improving hemodynamics and regional function, and in attenuating ventricular remodeling.

Plasma Lipidomic Analysis of Stable and Unstable Coronary Artery Disease

Objective—Traditional risk factors for coronary artery disease (CAD) fail to adequately distinguish patients who have atherosclerotic plaques susceptible to instability from those who have more benign forms. Using plasma lipid profiling, this study aimed to provide insight into disease pathogenesis and evaluate the potential of lipid profiles to assess risk of future plaque instability. Methods and Results—Plasma lipid profiles containing 305 lipids were measured on 220 individuals (matched healthy controls, n=80; stable angina, n=60; unstable coronary syndrome, n=80) using electrospray-ionisation tandem mass spectrometry. ReliefF feature selection coupled with an L2-regularized logistic regression based classifier was used to create multivariate classification models which were verified via 3-fold cross-validation (1000 repeats). Models incorporating both lipids and traditional risk factors provided improved classification of unstable CAD from stable CAD (C-statistic=0.875, 95% CI 0.874–0.877) compared with models containing only traditional risk factors (C-statistic=0.796, 95% CI 0.795–0.798). Many of the lipids identified as discriminatory for unstable CAD displayed an association with disease acuity (severity), suggesting that they are antecedents to the onset of acute coronary syndrome. Conclusion—Plasma lipid profiling may contribute to a new approach to risk stratification for unstable CAD.

A meta-analysis of 3,773 patients treated with percutaneous coronary intervention or surgery for unprotected left main coronary artery stenosis.

OBJECTIVES This study sought to understand the total weight of evidence regarding outcomes in coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI) in unprotected left main coronary artery (ULMCA) stenosis. BACKGROUND Following a diagnosis of significant ULMCA stenosis in an individual that is a candidate for surgery, CABG is recommended by the American College of Cardiology/American Heart Association guidelines, whereas PCI is not recommended (Class III). METHODS Databases were searched for clinical studies that reported outcomes after PCI and CABG for the treatment of ULMCA stenosis. Ten studies were identified that included a total of 3,773 patients. RESULTS Meta-analysis showed that death, myocardial infarction, and stroke (major adverse cardiovascular or cerebrovascular events) were similar in the PCI- and CABG-treated patients at 1 year (odds ratio [OR]: 0.84 [95% confidence interval: 0.57 to 1.22]), 2 years (OR: 1.25 [95% CI: 0.81 to 1.94]), and 3 years (OR: 1.16 [95% CI: 0.68 to 1.98]). Target vessel revascularization was significantly higher in the PCI group at 1 year (OR: 4.36 [95% CI: 2.60 to 7.32]), 2 years (OR: 4.20 [95% CI: 2.21 to 7.97]), and 3 years (OR: 3.30 [95% CI: 0.96 to 11.33]). There was no difference in mortality in PCI- versus CABG-treated patients at 1 year (OR: 1.00 [95% CI: 0.70 to 1.41]), 2 years (OR: 1.27 [95% CI: 0.83 to 1.94]), and 3 years (OR: 1.11 [95% CI: 0.66 to 1.86]). CONCLUSIONS Our analysis reveals no difference in mortality or major adverse cardiovascular or cerebrovascular events, for up to 3 years, between PCI and CABG for the treatment of ULMCA stenosis. However, PCI patients had a significantly higher risk of target vessel revascularization. In selected patients with ULMCA stenosis, PCI is emerging as an acceptable option.

Comparison of Coronary Artery Bypass Surgery and Percutaneous Drug-Eluting Stent Implantation for Treatment of Left Main Coronary Artery Stenosis

OBJECTIVES The purpose of this study was to compare outcomes for drug-eluting stents (DES) and coronary artery bypass graft (CABG) surgery in patients with unprotected left main coronary artery (ULMCA) stenosis. BACKGROUND Expert guidelines recommend coronary artery bypass graft (CABG) surgery for the treatment of significant stenosis of the unprotected left main coronary artery (ULMCA) if the patient is eligible for CABG; however, treatment by percutaneous coronary intervention (PCI) is common. METHODS Details of patients (n = 343, ages 69.9 +/- 11.9 years) undergoing coronary revascularization for ULMCA stenosis (April 2003 to January 2007) were recorded. A total of 223 patients were treated with CABG (mean [interquartile range]: follow-up 600 [226 to 977) days) and 120 by PCI (follow-up 362 [192 to 586) days). The hazard ratios (HRs) for death and major adverse cardiovascular and cerebrovascular events (MACCE) were calculated incorporating propensity score adjustment. Survival comparisons were conducted in propensity-matched subjects (n = 134), and in low- and high-risk subjects for CABG. RESULTS Patients treated by PCI were more likely to be >or=75 years of age (49% vs. 33%; p = 0.005), and of greater surgical risk (Parsonnet score 17.2 +/- 11.2 vs. 13.0 +/- 9.3; p < 0.001) than patients treated by CABG. Overall, the propensity-adjusted HR for death was not statistically different (HR 1.93, 95% confidence interval [CI] 0.89 to 4.19, p = 0.10), but MACCE was greater in the PCI group (HR 1.83, 95% CI 1.01 to 3.32, p = 0.05). In propensity-matched individuals, neither survival nor MACCE-free survival were different. Survival was equivalent among low-risk candidates, but PCI had a tendency to inferior survival in high-risk candidates (Ellis category IV, log-rank p = 0.05). Interaction testing, however, failed to demonstrate a difference in outcomes of the 2 revascularization techniques as a function of baseline risk assessment. CONCLUSIONS Overall, the propensity-adjusted risk of mortality for treatment of ULMCA disease does not differ between PCI- and CABG-treated groups. There appears to be sufficient equipoise that a randomized clinical trial to compare the techniques would not be ethically contraindicated.

Predictive accuracy of SYNTAX score for predicting long-term outcomes of unprotected left main coronary artery revascularization.

The American College of Cardiology/American Heart Association recently updated recommendations for percutaneous coronary intervention (PCI) of unprotected left main coronary artery (ULMCA) disease from class III to II(b) according to the results of the SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery (SYNTAX) trial. The SYNTAX score is an angiographic tool using solely the coronary anatomy. We studied the effect of co-morbidities (Parsonnets score) on the ability of the SYNTAX score to predict long-term outcomes in patients with ULMCA disease treated by revascularization. A total of 328 patients underwent revascularization of ULMCA from April 2003 to February 2007. Of the 328 patients, 120 underwent PCI (median follow-up 973 days) and 208 underwent coronary artery bypass grafting (CABG) (median follow-up 1,298 days). The ability of the SYNTAX score to predict outcomes was assessed using the Cox proportional hazards model. The outcomes between the PCI and CABG groups were compared by propensity analysis. The median SYNTAX score was 26 in the PCI and 28 in the CABG group (p = 0.5). In the PCI group, greater quartiles were associated with worse survival (62.1% at SYNTAX score of ≥36 vs 82.4% at SYNTAX score of <36, p = 0.03) and all-cause mortality, myocardial infarction, cerebrovascular events, and target vessel revascularization-free (MACCE) survival (47.7%, SYNTAX score ≥20 vs 76.6%, SYNTAX score <20, p = 0.02). Using the Parsonnet score as a covariate, the SYNTAX score continued to be an independent predictor of MACCE and demonstrated a trend toward predicting mortality in the PCI group. In contrast, the SYNTAX score did not predict the outcomes for the CABG group. No difference was found in mortality between the PCI and CABG groups for ULMCA disease, regardless of coronary complexity; although greater SYNTAX scores were associated with increased MACCE rates with PCI compared to CABG. Both the coronary anatomy (SYNTAX score) and co-morbidities (Parsonnets score) predicted long-term outcomes for PCI of ULMCA disease. In contrast, the SYNTAX score did not predict the outcomes after CABG. In conclusion, the ideal scoring system to guide an appropriate revascularization decision for ULMCA disease should take into account both the coronary anatomy and the co-morbidities.

Meta-Analysis of Incidence, Clinical Characteristics and Implications of Stent Fracture

A meta-analysis of published studies was conducted to evaluate the incidence, predictors, and clinical outcomes of stent fractures. Eight studies with 108 stent fractures in 5,321 patients were analyzed using the Bayesian method. Study end points included in-stent restenosis (ISR) and target lesion revascularization (TLR). The mean incidence of stent fracture per patient was 4.0% (95% confidence interval 0.4% to 16.3%). All cases, except 1, were reported with sirolimus-eluting stents. The incidence of stent fracture was 30.4% in the left anterior descending coronary artery, 10.9% in the left circumflex coronary artery, 56.4% in the right coronary artery, < 0.01% in the left main coronary artery, and 1.7% in saphenous vein grafts. The probability of stent fracture was significantly higher in the right coronary artery than in the left anterior descending and left circumflex lesions (p < 0.01). Left main stents were less likely to fracture compared to those in all other vessels (p < 0.01). The probability of stent fracture was significantly increased in overlapping stents (7.5% vs 2.1%, p = 0.01) and long stents (46 vs 32.5 mm, p < 0.01). Lesions with stent fractures had higher rates of ISR (38% vs 8.2%, p < 0.01) and TLR (17% vs 5.6%, p < 0.01). Conversely, the probability of stent fractures was higher in patients with ISR (12.8% vs 2.1%, p < 0.01) and TLR (8.8% vs 2.7%, p < 0.01). In conclusion, although not always associated with clinical sequelae, the probability of ISR and TLR is increased with stent fracture. Conversely, the probability of stent fractures is increased in lesions with ISR or TLR, thus raising the need for surveillance and management guidelines for at-risk patients.

Intrinsic cardiac origin of human cardiosphere-derived cells

AIMS Cardiosphere-derived cells (CDCs) are in clinical development as a regenerative cell product which can be expanded ex vivo from patient cardiac biopsies. Cardiosphere-derived cells are clonogenic, exhibit multilineage differentiation, and exert functional benefits in preclinical models of heart failure. The origin of CDCs remains unclear: are these cells endogenous to the heart, or do they arise from cells that populate the heart via blood-borne seeding? METHODS AND RESULTS Right ventricular endomyocardial biopsies were obtained from cardiac transplant recipients (n = 10, age 57 ± 15 years), and CDCs expanded from each biopsy. Donor-recipient mismatches were used to probe the origin of CDCs in three complementary ways. First, DNA analysis of short-tandem nucleotide repeats (STRs) was performed on genomic DNA from donor and recipient, then compared with the STR pattern of CDCs. Second, in two cases where the donor was male and the recipient female, CDCs were examined for the presence of X and Y chromosomes by fluorescence in situ hybridization. Finally, in two cases, quantitative PCR (qPCR) was performed for individual-specific polymorphisms of a major histocompatability locus to quantify the contribution of recipient cells to CDCs. In no case was recipient DNA detectable in the CDCs by STR analysis. In the two cases in which a female patient had received a male heart, all CDCs examined had an X and Y chromosome, similarly indicating exclusively donor origin. Likewise, qPCR on CDCs did not detect any recipient DNA. CONCLUSION Cardiosphere-derived cells are of endogenous cardiac origin, with no detectable contribution from extra-cardiac seeding.

SIRPA, VCAM1 and CD34 identify discrete lineages during early human cardiovascular development

The study of human cardiogenesis would benefit from a detailed cell lineage fate map akin to that established for the haematopoietic lineages. Here we sought to define cell lineage relationships based on the expression of NKX2-5 and the cell surface markers VCAM1, SIRPA and CD34 during human cardiovascular development. Expression of NKX2-5(GFP) was used to identify cardiac progenitors and cardiomyocytes generated during the differentiation of NKX2-5(GFP/w) human embryonic stem cells (hESCs). Cardiovascular cell lineages sub-fractionated on the basis of SIRPA, VCAM1 and CD34 expression were assayed for differentiation potential and gene expression. The NKX2-5(pos)CD34(pos) population gave rise to endothelial cells that rapidly lost NKX2-5 expression in culture. Conversely, NKX2-5 expression was maintained in myocardial committed cells, which progressed from being NKX2-5(pos)SIRPA(pos) to NKX2-5(pos)SIRPA(pos)VCAM1(pos). Up-regulation of VCAM1 was accompanied by the expression of myofilament markers and reduced clonal capacity, implying a restriction of cell fate potential. Combinatorial expression of NKX2-5, SIRPA, VCAM1 and CD34 can be used to define discrete stages of cardiovascular cell lineage differentiation. These markers identify specific stages of cardiomyocyte and endothelial lineage commitment and, thus provide a scaffold for establishing a fate map of early human cardiogenesis.

New Paradigms of Myocardial Regeneration Post-Infarction: Tissue Preservation, Cell Environment, and Pluripotent Cell Sources

Meta-analyses of intracoronary autologous bone marrow cell infusion in patients with acute myocardial infarction establish the procedure as safe. Nonetheless, the typical small increase in ejection fraction is of uncertain clinical significance, with little if any evidence of myocardial regeneration. In this paper, we describe 3 new paradigms of myocardial preservation and regeneration that provide reasonable hope that the goal of myocardial rejuvenation can be achieved. The first paradigm is that substantial preservation of myocardium is possible even during the period of coronary occlusion and immediate reperfusion, before interventions aimed at myocardial regeneration. The factors that induce myocardial preservation may also create an environment more receptive to subsequent myocardial regeneration. The second paradigm is that the local environment may regulate the behavior of cells in the ischemic/infarct region. For instance, adult cells may be induced to re-enter the cell cycle and proliferate with appropriate environmental modification. The final paradigm is that autologous cardiac stem cells or induced pluripotent stem cells can create new myocytes and myocardium. Taken together, these new ideas, each still to be proven, suggest that the goal of regenerating functioning new myocardium can still be achieved.