Anthony D. Caffarelli

Embryonic Stem Cell Immunogenicity Increases Upon Differentiation After Transplantation Into Ischemic Myocardium

Background—We investigated whether differentiation of embryonic stem cells (ESCs) in ischemic myocardium enhances their immunogenicity, thereby increasing their chance for rejection. Methods and Results—In one series, 129/SvJ-derived mouse ESCs (ES-D3 line) were transplanted by direct myocardial injection (1×106 cells) into murine hearts of both allogeneic (BALB/c, n=20) and syngeneic (129/SvJ, n=12) recipients after left anterior artery ligation. Hearts were procured at 1, 2, 4, and 8 weeks after ESC transplantation and analyzed by immunohistochemistry to assess immune cell infiltration (CD3, CD4, CD8, B220, CD11c, Mac-1, and Gr-1) and ESC differentiation (hematoxylin and eosin). In a second series (allogeneic n=5, sham n=3), ESC transplantation was performed similarly; however after 2 weeks, left anterior descending artery-ligated and ESC-injected hearts were heterotopically transplanted into naive BALB/c recipients. After an additional 2 weeks, donor hearts were procured and analyzed by immunohistochemistry. In the first series, the size of all ESC grafts remained stable and there was no evidence of ESC differentiation 2 weeks after transplantation; however, after 4 weeks, both allogeneic and syngeneic ESC grafts showed the presence of teratoma. By 8 weeks, surviving ESCs could be detected in the syngeneic but not in the allogeneic group. Mild inflammatory cellular infiltrates were found in allogeneic recipients at 1 and 2 weeks after transplantation, progressing into vigorous infiltration at 4 and 8 weeks. The second series demonstrated similar vigorous infiltration of immune cells as early as 2 weeks after heterotopic transplantation. Conclusion—In vivo differentiated ESCs elicit an accelerated immune response as compared with undifferentiated ESCs. These data imply that clinical transplantation of allogeneic ESCs or ESC derivatives for treatment of cardiac failure might require immunosuppressive therapy.

Early outcomes of deliberate nonoperative management for blunt thoracic aortic injury in trauma

OBJECTIVE Traumatic blunt aortic injury has traditionally been viewed as a surgical emergency, whereas nonoperative therapy has been reserved for nonsurgical candidates. This study reviews our experience with deliberate, nonoperative management for blunt thoracic aortic injury. METHODS A retrospective chart review with selective longitudinal follow-up was conducted for patients with blunt aortic injury. Surveillance imaging with computed tomography angiography was performed. Nonoperative patients were then reviewed and analyzed for survival, evolution of aortic injury, and treatment failures. RESULTS During the study period, 53 patients with an average age of 45 years (range, 18-80 years) were identified, with 28% presenting to the Stanford University School of Medicine emergency department and 72% transferred from outside hospitals. Of the 53 patients, 29 underwent planned, nonoperative management. Of the 29 nonoperative patients, in-hospital survival was 93% with no aortic deaths in the remaining patients. Survival was 97% at a median of 1.8 years (range, 0.9-7.2 years). One patient failed nonoperative management and underwent open repair. Serial imaging was performed in all patients (average = 107 days; median, 31 days), with 21 patients having stable aortic injuries without progression and 5 patients having resolved aortic injuries. CONCLUSIONS This experience suggests that deliberate, nonoperative management of carefully selected patients with traumatic blunt aortic injury may be a reasonable alternative in the polytrauma patient; however, serial imaging and long-term follow-up are necessary.

In Vivo Visualization of Cardiac Allograft Rejection and Trafficking Passenger Leukocytes Using Bioluminescence Imaging

Background—We investigated the feasibility of bioluminescence imaging (BLI) for the in vivo assessment of cardiac allograft viability and visualization of passenger leukocytes during the course of acute rejection. Methods and Results—Hearts of FVB (H-2q) luciferase-green fluorescent protein transgenic mice (β-actin promoter) or FVB luciferase transgenic mice (CD5 promoter) were heterotopically transplanted into either BALB/c (H-2d) or FVB recipients. Light intensity emitting from the recipient animals was measured daily by in vivo BLI until 12 days after transplantation. Graft beating score (0 to 4) was assessed by daily abdominal palpation until 12 days after transplantation. Inflammatory cell infiltration (CD45 stain) and structural changes of green fluorescent protein-positive cardiomyocytes were followed by immunohistochemistry. All cardiac allografts were acutely rejected by 12 days after transplantation. The intensity of light emitting from cardiac allografts declined 4 days after transplantation and correlated with graft beating scores (R2=0.91, P=0.02). Immunohistochemistry confirmed these results by showing an increase of CD45+ inflammatory cell infiltration and destruction of green fluorescent protein-positive cardiomyocytes in the cardiac allografts during acute rejection. In vivo BLI visualized migration and proliferation of CD5+ passenger leukocytes in both syngeneic and allogeneic recipients. In the allograft recipients, light signal from CD5+ passenger leukocytes peaked at 6 hours and diminished by 12 hours, whereas in the syngeneic recipients, the signal remained high until 10 days after transplantation. Conclusions—BLI is a useful modality for the quantitative assessment of in vivo cardiac graft viability and tracking of passenger leukocytes in vivo during the course of acute rejection.

Multimodality evaluation of the viability of stem cells delivered into different zones of myocardial infarction.

Background—We tested the hypothesis that multimodality imaging of mouse embryonic stem cells (mESCs) provides accurate assessment of cellular location, viability, and restorative potential after transplantation into different zones of myocardial infarction. Methods and Results—Mice underwent left anterior descending artery ligation followed by transplantation of dual-labeled mESCs with superparamagnetic iron oxide and luciferase via direct injection into 3 different zones of myocardial infarction: intra-infarction, peri-infarction, and normal (remote). One day after transplantation, magnetic resonance imaging enabled assessment of the precise anatomic locations of mESCs. Bioluminescence imaging allowed longitudinal analysis of cell viability through detection of luciferase activity. Subsequent evaluation of myocardial regeneration and functional restoration was performed by echocardiography and pressure–volume loop analysis. Using 16-segment analysis, we demonstrated precise localization of dual-labeled mESCs. A strong correlation between histology and magnetic resonance imaging was established (r=0.962, P=0.002). Bioluminescent imaging data demonstrated that cell viability in the remote group was significantly higher than in other groups. Echocardiography and pressure–volume loop analysis revealed improved functional restoration in animals treated with mESCs, although myocardial regeneration was not observed. Conclusions—Multimodality evaluation of mESC engraftment in the heterogeneous tissue of myocardial infarction is possible. Magnetic resonance imaging demonstrated accurate anatomic localization of dual-labeled mESCs. Bioluminescent imaging enabled assessment of variable viability of mESCs transplanted into the infarcted myocardium. Echocardiography and pressure–volume loop analysis validated the restorative potential of mESCs. Although mESCs transplanted into the remote zone demonstrated the highest viability, precise delivery of mESCs into the peri-infarction region might be equally critical in restoring the injured myocardium.

A Thrombus in the Venous Reservoir While Using Bivalirudin in a Patient with Heparin-induced Thrombocytopenia Undergoing Heart Transplantation

Direct thrombin inhibitors are heparin alternatives for anticoagulation during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia. We report a case of a large thrombus forming in the venous reservoir while using bivalirudin. We suggest that blood stasis associated with the full venous reservoir maintained in this case led to formation of a large thrombus at the top of the venous canister. Furthermore, activated clotting times may not accurately reflect the magnitude of anticoagulation when using direct thrombin inhibitors.

Will minimally invasive valve replacement ever really be important

Purpose of review Most cardiac surgical centers worldwide have instituted some form of minimally invasive surgery into their operative armamentarium. However, skepticism still remains whether minimally invasive valve replacement will ever really be important. This review first addresses the definition of minimally invasive surgery and then analyzes the possible advantages and disadvantages of minimally invasive valvular surgery. Recent findings The nomenclature for minimally invasive surgery is ill defined. Minimally invasive valve replacement is a safe and effective procedure compared with total sternotomy. The advantages of minimally invasive valve replacement are the length of stay and disposition after discharge, postoperative bleeding, cosmesis, and postoperative pain, whereas the main disadvantage involves the operative times early in the learning curve. Summary Minimally invasive valve replacement is beneficial and will continue to evolve as an important treatment option for patients with valvular heart diseases.

The road to clinical xenotransplantation: A worthwhile journey

Xenotransplantation carries numerous ethical dilemmas. In the Position Paper of the Ethics Committee of the International Xenotransplantation Association, Sykes et al. diagram important ethics issues including respect for clinical subjects characterized by proper informed consent, and beneficence to the patient and the community at large, highlighting the possible risk of porcine endogenous retroviruses and xenotourism. We propose optimizing informed consent to take into account the psychological, scientific, and ethical nuances of xenotransplantation. Moreover, regulation of xenotourism should mirror established U.S. guidelines for visitors with communicable diseases, thereby not limiting the rights of xenotransplant recipients.

Acute Cellular Insulin Resistance and Hyperglycemia Associated with Hypophosphatemia After Cardiac Surgery

Successful glycemic control reduces morbidity and mortality in cardiac surgery patients. Protocols that include insulin infusions are commonly followed to achieve target blood glucose levels. Insulin resistance has been reported and linked to low serum phosphate levels in animal models and studies in diabetic outpatients, but not in postoperative patients. The following case series is a retrospective observational review of 8 cardiac surgery patients who developed insulin resistance early after surgery; this resistance was reversed by correcting serum hypophosphatemia. We discuss the multiple underlying mechanisms causing hypophosphatemia.