Heart transplantation: a thirty-year perspective

A second chance for a new heart? The role of metabolic and bariatric surgery in patients with end-stage heart failure

BACKGROUND

Obesity is an independent risk factor for heart failure (HF). Substantial weight loss has been shown to reverse obesity-related cardiomyopathy. This study aimed to report our institution's experience with laparoscopic sleeve gastrectomy (LSG) in patients with morbid obesity and end-stage HF.

METHODS

Between 2018 and 2022, 26 patients with end-stage HF were referred for LSG. Of 26 patients, 16 underwent an operation, and 10 did not. After institutional review board approval, a retrospective electronic medical record review was performed to evaluate (i) age, (ii) preoperative weight, (iii) decrease in body mass index (BMI) score, (iv) whether the patient underwent heart transplantation, and (v) mortality. Data analysis was performed using Stata/SE (version 17.0; StataCorp). The Wilcoxon rank-sum test was used to compare continuous variables between the cohorts, and the Pearson chi-square test was used for binary variables with Bonferroni correction applied.

RESULTS

The LSG and non-LSG cohorts had comparable ages (P = .088) and starting BMI score (P = .918), and a proportion of patients had a ventricular assist device (P = .191). Patients who underwent LSG lost significantly more weight than the patients who did not, with an average decrease in BMI score of 8.9 kg/m2 (SD, ±6.13) and 1.1 kg/m2 (SD, ±4.10), respectively (P = .040). Of note, 6 patients (37.5%) who underwent LSG eventually underwent transplantation, compared with 2 patients (20.0%) from the matched cohort (P = .884). Of the 26 patients, there were 6 deaths: 2 (12.5%) in the LSG cohort and 4 (40.0%) in the non-LSG cohort (P = .525).

CONCLUSION

LSG may be safe and effective for weight loss in patients with HF. This operation may provide patients affected by obesity with end-stage HF the lifesaving opportunity to achieve transplant candidacy.

Application potential of three-dimensional silk fibroin scaffold using mesenchymal stem cells for cardiac regeneration

Cardiac tissue engineering focusing on biomaterial scaffolds incorporating cells from different sources has been explored to regenerate or repair damaged area as a lifesaving approach.The aim of this study was to evaluate the cardiomyocyte differentiation potential of human adipose mesenchymal stem cells (hAD-MSCs) as an alternative cell source on silk fibroin (SF) scaffolds for cardiac tissue engineering. The change in surface morphology of SF scaffolds depending on SF concentration (1-6%, w/v) and increase in their porosity upon application of unidirectional freezing were visualized by scanning electron microscopy (SEM). Swelling ratio was found to increase 2.4 fold when SF amount was decreased from 4% to 2%. To avoid excessive swelling, 4% SF scaffold with swelling ratio of 10% (w/w) was chosen for further studies.Biodegradation rate of SF scaffolds depended on enzymatic activity was found to be 75% weight loss of SF scaffolds at the day 14. The phenotype of hAD-MSCs and their multi-linage potential into chondrocytes, osteocytes, and adipocytes were shown by flow cytometry and immunohistochemical staining, respectively.The viability of hAD-MSCs on 3D SF scaffolds was determined as 90%, 118%, and 138% after 1, 7, and 14 days, respectively. The use of 3D SF scaffolds was associated with increased production of cardiomyogenic biomarkers: α-actinin, troponin I, connexin 43, and myosin heavy chain. The fabricated 3D SF scaffolds were proved to sustain hAD-MSCs proliferation and cardiomyogenic differentiation therefore, hAD-MSCs on 3D SF scaffolds may useful tool to regenerate or repair damaged area using cardiac tissue engineering techniques.

Nanoscale Technologies for Prevention and Treatment of Heart Failure: Challenges and Opportunities

The adult myocardium has a limited regenerative capacity following heart injury, and the lost cells are primarily replaced by fibrotic scar tissue. Suboptimal efficiency of current clinical therapies to resurrect the infarcted heart results in injured heart enlargement and remodeling to maintain its physiological functions. These remodeling processes ultimately leads to ischemic cardiomyopathy and heart failure (HF). Recent therapeutic approaches (e.g., regenerative and nanomedicine) have shown promise to prevent HF postmyocardial infarction in animal models. However, these preclinical, clinical, and technological advancements have yet to yield substantial enhancements in the survival rate and quality of life of patients with severe ischemic injuries. This could be attributed largely to the considerable gap in knowledge between clinicians and nanobioengineers. Development of highly effective cardiac regenerative therapies requires connecting and coordinating multiple fields, including cardiology, cellular and molecular biology, biochemistry and chemistry, and mechanical and materials sciences, among others. This review is particularly intended to bridge the knowledge gap between cardiologists and regenerative nanomedicine experts. Establishing this multidisciplinary knowledge base may help pave the way for developing novel, safer, and more effective approaches that will enable the medical community to reduce morbidity and mortality in HF patients.

Combined treatment with simvastatin and rapamycin attenuates cardiac allograft rejection through the regulation of T helper 17 and regulatory T cells

Allograft rejection is an important issue post cardiac transplantation. In order to investigate the effect of combined treatment with simvastatin and rapamycin on allograft rejection, a cardiac transplantation rat model was employed in the present study. The survival time of rats following cardiac transplantation was recorded, while histopathological alterations were assessed by hematoxylin and eosin staining. The levels of transcription factors were measured by reverse transcription-quantitative polymerase chain reaction. In addition, the levels of CD4⁺ interleukin (IL)-17⁺ cells and CD4⁺ forkhead box P3 (FOXP3)⁺ cells in the allografts and CD4⁺ T cells and CD8⁺ T cells in the spleens were detected by flow cytometry. The results of the current study demonstrated that, following treatment with simvastatin and rapamycin, the survival time of model rats was prolonged, and the histopathological damage was attenuated. Treatment with simvastatin and rapamycin also led to decreased retinoic acid receptor-related orphan receptor γt (RORγt) level, increased FOXP3 level, reduced levels of CD4⁺IL-17⁺, CD4⁺ T and CD8⁺ T cells, and increased level of CD4⁺FOXP3⁺ cells. In conclusion, the current study observed that simvastatin and rapamycin performed a synergistic effect to reduce cardiac transplantation rejection. Thus, combined therapy of simvastatin and rapamycin may be a promising adjuvant therapy to reduce rejection post cardiac transplantation.

MMP-14 promotes VSMC migration via up-regulating CD44 expression in cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV) was the leading cause of late death in heart transplantation recipients. Matrix metalloproteinase-14 (MMP-14), as a member of the MMPs family, has been reported to play a vital role in coronary vascular lesions of allotransplanted hearts. However, concrete mechanism is still unclear. Herein, we showed that the expression of MMP-14 was different between isografts and allografts. Interestingly, we found MMP-14 could interact with CD44 in allografts. Cluster of differentiation 44 (CD44), as a cell adhesion receptor and is involved in cell migration, caused our interest in MMP-14/CD44 complex in allografts. Then we analyzed the effect of MMP-14/CD44 complex on pro-MMP-9 activation and vascular smooth muscle cell (VSMC) migration in rat VSMC TNF-α treated model. Then, we further found intervention of MMP-14/CD44 complex could inhibit VSMC migration. Our results elucidate the molecular mechanism of VSMC migration after cardiac transplantation and provide theoretical basis for seeking new specific drug targets for CAV prevention and treatment.

Erythroblast transformation-specific 2 correlates with vascular smooth muscle cell apoptosis in rat heterotopic heart transplantation model

BACKGROUND

Cardiac allograft vasculopathy (CAV) decreases the long-term survival of heart transplantation recipients. Vascular smooth muscle cell (VSMC) apoptosis is an important pathological feature of CAV. Erythroblast transformation-specific 2 (Ets-2), as a transcription factor, participates in cell apoptosis and plays an important role in organ transplantation.

METHODS

Hearts from Wistar-Furth (WF:RT1u) rats were heterotopically transplanted into Lewis (Lew:RT1(l)) rats without immunosuppression. Additional syngeneic heterotopic cardiac transplantations were performed in Lewis rats. HE staining was used to identify CAV. Ets-2 expression was examined by western blot. Ets-2 tissue location was examined by immunohistochemical assay and double immunostaining. Cleaved caspase 3 expression was detected by western blot. Co-localization of Ets-2 and cleaved caspase 3 was detected by double immunostaining. Ets-2, p53, cleaved caspase 3 and Bcl-xl expression in rat VSMC line A7R5 was examined after Ets-2 siRNA transfection. TUNEL assay was applied to detect A7R5 apoptosis with or without ETS-2 siRNA transfection. Immunoprecipitation was performed to explore the interaction between Ets-2 and p53.

RESULTS

Ets-2 expression decreased in the allograft group but had no obvious change in the isograft group. Meanwhile, the phenomenon of CAV was observed in the allograft group and there is neointima formation in the isograft group which is not obvious compared with allograft group. Additionally, Ets-2 expression was opposite to VSMC apoptosis in the allograft group. In vitro, Ets-2 siRNA transfection in A7R5cells resulted in enhanced cell apoptosis. Finally, Ets-2 interacted with p53.

CONCLUSIONS

Ets-2 might inhibit VSMC apoptosis via p53 pathway. The results further elucidate the molecular mechanism of VSMC apoptosis after heart transplantation during CAV and provide theoretical basis for seeking new specific drug targets for CAV prevention and treatment.

Micro- and nano-force evaluation of bioengineered muscle cells: a non-contact two-dimensional biosensing using surface acoustic wave devices

A high degree of cell-generated force measurement is required to evaluate the biomechanical performance of bioengineered muscle tissues. However, the conventional cantilever types of direct force measurement methods have limitations in developing a non-contact two-dimensional force sensing device for a single muscle cell. In this paper, a method is proposed and discussed by using focused surface acoustic wave and magneto-optic Kerr measurements. To depict the capability of the proposed method, a conceptual design of such a sensory device is demonstrated for non-contact two-dimensional force measurement of a single muscle cell.

Management of the Potential Organ Donor in the ICU: Society of Critical Care Medicine/American College of Chest Physicians/Association of Organ Procurement Organizations Consensus Statement

This document was developed through the collaborative efforts of the Society of Critical Care Medicine, the American College of Chest Physicians, and the Association of Organ Procurement Organizations. Under the auspices of these societies, a multidisciplinary, multi-institutional task force was convened, incorporating expertise in critical care medicine, organ donor management, and transplantation. Members of the task force were divided into 13 subcommittees, each focused on one of the following general or organ-specific areas: death determination using neurologic criteria, donation after circulatory death determination, authorization process, general contraindications to donation, hemodynamic management, endocrine dysfunction and hormone replacement therapy, pediatric donor management, cardiac donation, lung donation, liver donation, kidney donation, small bowel donation, and pancreas donation. Subcommittees were charged with generating a series of management-related questions related to their topic. For each question, subcommittees provided a summary of relevant literature and specific recommendations. The specific recommendations were approved by all members of the task force and then assembled into a complete document. Because the available literature was overwhelmingly comprised of observational studies and case series, representing low-quality evidence, a decision was made that the document would assume the form of a consensus statement rather than a formally graded guideline. The goal of this document is to provide critical care practitioners with essential information and practical recommendations related to management of the potential organ donor, based on the available literature and expert consensus.

Increasing Frequency of Left Ventricular Assist Device Exchanges in the United States

BACKGROUND

Recent reports indicate an increased prevalence and earlier onset of pump thrombosis and associated pump exchanges after left ventricular assist device (LVAD) implantation. Questions remain regarding the current rate and clinical effect of pump exchanges.

METHODS

All United States Medicare fee-for-service patients undergoing LVAD implantations (n = 3,166) between January 2009 and December 2012 were identified by procedural codes present on carrier claims collected by the Centers for Medicare & Medicaid Services. Pump exchange, pump removal, heart transplantation, and death were collected from subsequent carrier claim and denominator files. Comorbidities present before implantation were generated using the Elixhauser comorbidity index.

RESULTS

Compared with patients who received LVADs before March 1, 2011, LVAD recipients after March 1, 2011, were older on average (63.9 vs 62.2 years, p < 0.01), more likely to be male (82.3% vs. 79.4%, p = 0.04), and had a higher incidence of common comorbidities. The later cohort had higher occurrence of pump exchange by Kaplan-Meier time-to-event estimates and Fisher exact tests at 3 months (1.8 vs 0.8, p = 0.02), 6 months (3.3 vs 1.0, p < 0.01), and 12 months (4.9 vs 2.2, p < 0.01). Cox regression analysis found time-dependent pump exchange was associated with worse survival (hazard ratio, 2.5; 95% confidence interval, 1.8 to 3.62; p < 0.01) after adjusting for age, gender, and comorbidities.

CONCLUSIONS

Although LVAD exchanges remain relatively uncommon, a significant increase in the incidence of the procedure has occurred since March 1, 2011. Pump exchanges are highly associated with death, and further research is required to understand the cause of this disturbing trend and surveillance to determine its trajectory.

Expression of HSPA12B in acute cardiac allograft rejection in rats

HSP70 may play a more important role in regulating antigen-specific immune response than other HSPs; however, HSPA12B production in transplanted heart remains obscure, which was identified as the newest member of the HSP70 family. In the current study, we performed a heart transplantation model in adult rats and investigated the dynamic changes of HSPA12B expression in the cardiac grafts. The cardiac grafts of allogeneic (Wistar-Lewis rat) and syngeneic (Lewis-Lewis rat) rat models were subjected to histopathological and immunohistochemical analyses for HSPA12B expression on days 0-7 after operation. We also examined the expression profiles of active caspase-3, whose changes were correlated with the expression profiles of HSPA12B. Our results demonstrated that HSPA12B protein exhibited biphasic patterns in transplanted heart. The first expression phase correlated with ischemical reperfusion injury over 2 days post-transplant. The second peak of HSPA12B expression was found only in allografts on day 5, concurrent with the expression of caspase-3. Immunohistochemical assay showed that compared with rare expression in isografts, there were significant protein expressions of HSPA12B and caspase-3 in heart allografts from day 5 to 7 post-transplant. Furthermore, double immunofluorescence staining for active caspase-3 and HSPA12B in isografts and allografts at day 5 post-transplant were analyzed and colocalization of HSPA12B/active caspase-3 was detected in allografts. In conclusion, this is the first description of HSPA12B expression in acute cardiac allograft rejection. Our results suggested that HSPA12B might play crucial roles in heart pathophysiology after transplantation.

Ischemic preconditioning for cell-based therapy and tissue engineering

Cell- and tissue-based therapies are innovative strategies to repair and regenerate injured hearts. Despite major advances achieved in optimizing these strategies in terms of cell source and delivery method, the clinical outcome of cell-based therapy remains unsatisfactory. The non-genetic approach of ischemic/hypoxic preconditioning to enhance cell- and tissue-based therapies has received much attention in recent years due to its non-invasive drug-free application. Here we discuss the current development of hypoxic/ischemic preconditioning to enhance stem cell-based cardiac repair and regeneration.

Nanoparticle PET-CT detects rejection and immunomodulation in cardiac allografts

BACKGROUND

Macrophages predominate among the inflammatory cells in rejecting allografts. These innate immune cells, in addition to allospecific T cells, can damage cardiomyocytes directly.

METHODS AND RESULTS

We explored whether sensitive positron emission tomography-computed tomography (PET-CT) imaging of macrophages-avid nanoparticles detects rejection of heart allografts in mice. In addition, we used the imaging method to follow the immunomodulatory impact of angiotensin-converting enzyme inhibitor therapy on myeloid cells in allografts. Dextran nanoparticles were derivatized with the PET isotope copper-64 and imaged 7 days after transplantation. C57BL/6 recipients of BALB/c allografts displayed robust positron emission tomography signal (standard uptake value allograft, 2.8±0.3; isograft control, 1.7±0.2; P<0.05). Autoradiography and scintillation counting confirmed the in vivo findings. We then imaged the effects of angiotensin-converting enzyme inhibitor (5 mg/kg enalapril). Angiotensin-converting enzyme inhibitor significantly decreased nanoparticle signal (P<0.05). Histology and flow cytometry showed a reduced number of myeloid cells in the graft, blood, and lymph nodes and diminished antigen presentation (P<0.05 versus untreated allografts). Angiotensin-converting enzyme inhibitor also significantly prolonged allograft survival (12 versus 7 days; P<0.0001).

CONCLUSIONS

Nanoparticle macrophage PET-CT detects heart transplant rejection and predicts organ survival by reporting on myeloid cells.

Ischemic preconditioning promotes intrinsic vascularization and enhances survival of implanted cells in an in vivo tissue engineering model

Ischemic preconditioning (IPC) is a potent and effective means of protecting cells against ischemic injury. The protection has been demonstrated to involve release of paracrine factors that promote cell survival and angiogenesis, factors important for successful tissue engineering. The aim of the present study was to determine whether IPC of a vascular bed in vivo is an effective strategy to prepare it for tissue engineering with implanted cells. To test this hypothesis, an in vivo vascularized tissue engineering approach was employed, whereby polyacrylic chambers were placed around the femoral vessels of adult Sprague-Dawley rats. IPC was induced by 3 cycles of 5 min femoral artery occlusion interspersed with 5-min periods of reperfusion. Rats subjected to IPC generated bigger tissue constructs at 7 and 28 days postimplantation of empty chambers (∼50% increase in weight and volume, p<0.05). Morphometric counting of Masson trichrome stained tissue sections revealed significantly greater tissue construct volumes in ischemic preconditioned vascular beds at 7 and 28 days, increasing both fibrin matrix and vascularized tissue. Furthermore, morphometry of lectin-labeled blood vessels indicated an increase in vascular volume in IPC tissue constructs (∼100% increase vs. control, p<0.05). To investigate the cytoprotective effect of IPC, we implanted DiI-labeled neonatal rat cardiomyocytes in the chambers for 3 days, and IPC significantly reduced apoptosis of implanted cells as determined by the TUNEL assay and cleaved caspase-3 immunostaining. Furthermore, IPC significantly increased the cardiac muscle volume and vascular volume at 28 days after implantation of cardiomyocytes. In conclusion, in vivo IPC promotes survival of implanted cardiomyocytes and is associated with enhanced angiogenesis. IPC may represent a new approach to optimize tissue engineering with implanted cells.

The acute haemodynamic effect of nebulised frusemide in stable, advanced heart failure

PURPOSE

To assess the acute haemodynamic effects of nebulised frusemide in a stable advanced heart failure population.

PROCEDURE

In this randomised, double blind, placebo controlled trial, people with stable, advanced heart failure undergoing right heart catheterisation were randomised to receive either 40 mg (4 ml) of nebulised frusemide or 4 ml of normal saline. Following inhalation of the study medication, subjects' pulmonary pressures were recorded every 15 min for 1 h.

FINDINGS

There were no significant changes in the weighted average time course data of the subjects (n=32) in either group over the study period, in particular no differences were observed in haemodynamic parameters between the two groups. Weighted average pulmonary capillary wedge pressure after 60 min in the frusemide group was 22.5 (SD 6.5) mmHg (n=14) compared to the placebo group's 24.0 (SD 7.3) mmHg (n=18), p=0.55. The frusemide group had a significantly greater change in the median volume of urine in the bladder over the study period (186 ml IQR 137.8-260.8) compared to the placebo group (76 ml IQR 39.0-148.0) p=0.02.

CONCLUSION

This study showed that nebulised frusemide had no significant clinical effect on the haemodynamic characteristics of the subjects.

Adipose tissue-derived stem cells display a proangiogenic phenotype on 3D scaffolds

Ischemic heart disease is the leading cause of death worldwide. Recent studies suggest that adipose tissue-derived stem cells (ASCs) can be used as a potential source for cardiovascular tissue engineering due to their ability to differentiate along the cardiovascular lineage and to adopt a proangiogenic phenotype. To understand better ASCs' biology, we used a novel 3D culture device. ASCs' and b.END-3 endothelial cell proliferation, migration, and vessel morphogenesis were significantly enhanced compared to 2D culturing techniques. ASCs were isolated from inguinal fat pads of 6-week-old GFP+/BLI+ mice. Early passage ASCs cells (P3-P4), PKH26-labeled murine b.END-3 cells or a co-culture of ASCs and b.END-3 cells were seeded at a density of 1 × 10(5) on three different surface configurations: (a) a 2D surface of tissue culture plastic, (b) Matrigel, and (c) a highly porous 3D scaffold fabricated from inert polystyrene. VEGF expression, cell proliferation, and tubulization, were assessed using optical microscopy, fluorescence microscopy, 3D confocal microscopy, and SEM imaging (n = 6). Increased VEGF levels were seen in conditioned media harvested from co-cultures of ASCs and b.END-3 on either Matrigel or a 3D matrix. Fluorescence, confocal, SEM, bioluminescence revealed improved cell, proliferation, and tubule formation for cells seeded on the 3D polystyrene matrix. Collectively, these data demonstrate that co-culturing ASCs with endothelial cells in a 3D matrix environment enable us to generate prevascularized tissue-engineered constructs. This can potentially help us to surpass the tissue thickness limitations faced by the tissue engineering community today.

Treatment with interleukin-12/23p40 antibody attenuates acute cardiac allograft rejection

BACKGROUND

Interleukin (IL)-12 and -23 share the p40 subunit and are crucial for the development of T helper (Th) 1- and Th17-cell responses in acute graft rejection. However, little is known about the impact of treatment with antagonistic anti-p40 antibody in inhibiting rejection of cardiac allografts.

METHODS

C57BL/6 mice were transplanted with syngeneic or allogeneic (BALB/c) hearts and treated with 100 or 200 μg or 400 μg anti-P40 monoclonal antibody on postoperative days 1 and 3, respectively. The survival of grafts was monitored daily by abdominal palpation until the complete cessation of cardiac contractility (endpoint). The severity of acute rejection was evaluated by histology and immunohistochemistry. The expression of transcription factors within the grafts were measured by quantitative real-time polymerase chain reaction. Systemically, the lymphocytes were characterized by flow cytometry, and the serum levels of cytokines were determined by ELISA.

RESULTS

In comparison with mice treated with isotype IgG or saline, treatment with anti-p40 significantly alleviated acute phase allograft rejection and resulted in prolonged survival of cardiac allografts (P<0.05). These changes were associated with reduced infiltration of inflammatory cells and down-regulation of Th1- and Th17-specific transcription factors and cytokines. Furthermore, treatment with anti-p40 significantly reduced the percentages of splenic Th1 and Th17 cells, but not Th2 and regulatory T cells (P<0.05), with concomitant reduction of serum interferon-γ and IL-17 levels (P<0.05).

CONCLUSION

Our data indicated that treatment with anti-p40 inhibited Th1- and Th17-cell responses and prolonged the survival of cardiac allografts in mice.

Engineered heart tissue graft derived from somatic cell nuclear transferred embryonic stem cells improve myocardial performance in infarcted rat heart

The concept of regenerating diseased myocardium by implanting engineered heart tissue (EHT) is intriguing. Yet it was limited by immune rejection and difficulties to be generated at a size with contractile properties. Somatic cell nuclear transfer is proposed as a practical strategy for generating autologous histocompatible stem (nuclear transferred embryonic stem [NT-ES]) cells to treat diseases. Nevertheless, it is controversial as NT-ES cells may pose risks in their therapeutic application. EHT from NT-ES cell-derived cardiomyocytes was generated through a series of improved techniques in a self-made mould to keep the EHTs from contraction and provide static stretch simultaneously. After 7 days of static and mechanical stretching, respectively, the EHTs were implanted to the infarcted rat heart. Four weeks after transplantation, the suitability of EHT in heart muscle repair after myocardial infarction was evaluated by histological examination, echocardiography and multielectrode array measurement. The results showed that large (thickness/diameter, 2–4 mm/10 mm) spontaneously contracting EHTs was generated successfully. The EHTs, which were derived from NT-ES cells, inte grated and electrically coupled to host myocardium and exerted beneficial effects on the left ventricular function of infarcted rat heart. No teratoma formation was observed in the rat heart implanted with EHTs for 4 weeks. NT-ES cells can be used as a source of seeding cells for cardiac tissue engineering. Large contractile EHT grafts can be constructed in vitro with the ability to survive after implantation and improve myocardial performance of infarcted rat hearts.

Rejection of transplanted hearts in patients evaluated by the component analysis of multi-wavelength NAD(P)H fluorescence lifetime spectroscopy

Rejection of transplanted hearts remains one of the principal reasons for death of paediatric patients, but an appropriate diagnostic tool for the mild rejection in early stages is still missing. Tissue autofluorescence (AF) is one of the most versatile non-invasive tools for mapping the metabolic state in living tissues. Increasing interest in the imaging and diagnosis of living cells and tissues based on their intrinsic fluorescence rather than fluorescence labelling is closely connected to the latest developments in high-performance spectroscopy and microscopy techniques. In this contribution, we investigate individual components in spectrally- and time-resolved NAD(P)H fluorescence, revealed by linear unmixing, responsible for increased fluorescence in patients presenting mild rejection of transplanted hearts. Application of such approach has the potential to improve the diagnostics of the cardiac transplant rejection by helping currently used histological analysis.

Myeloperoxidase-rich Ly-6C+ myeloid cells infiltrate allografts and contribute to an imaging signature of organ rejection in mice

Rates of graft rejection are high among recipients of heart transplants. The onset and progression of clinically significant heart transplant rejection are currently monitored by serial biopsy, but this approach is highly invasive and lacks sensitivity. Here, we have developed what we believe to be a new technique to measure organ rejection noninvasively that involves the exploration of tissue-infiltrating leukocytes as biomarker sources for diagnostic imaging. Specifically, we profiled the myeloid response in a murine model of heart transplantation with the aim of defining and validating an imaging signature of graft rejection. Ly-6Chi monocytes, which promote inflammation, accumulated progressively in allografts but only transiently in isografts. Ly-6Clo monocytes, which help resolve inflammation, did not accumulate, although they composed the majority of the few remaining monocytes in isografts. The persistence of Ly-6Chi monocytes in allografts prompted us to screen for a Ly-6Chi monocyte-associated imaging marker. Low-density array data revealed that Ly-6Chi monocytes express 10-fold higher levels of myeloperoxidase (MPO) than Ly-6Clo monocytes. Noninvasive magnetic resonance imaging of MPO with an MPO-activatable Gd-chelate revealed a spatially defined T1-weighted signal in rejected allografts but not in isografts or MPO-deficient allograft recipients. Flow cytometry, enzymography, and histology validated the approach by mapping MPO activity to Ly-6Chi monocytes and neutrophils. Thus, MPO imaging represents a potential alternative to the current invasive clinical standard by which transplants are monitored.

Preparation and characterization of alginate/gelatin blend films for cardiac tissue engineering

The aim of this work was the preparation of blends based on alginate and gelatin, with different weight ratio, to combine the advantages of these two natural polymers for application in cardiac tissue engineering. The physicochemical characterization, performed by Fourier transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis, revealed a good miscibility and the presence of interactions among the functional groups of pure biopolymers. Concerning the swelling and degradation tests, performed in different solutions simulating body fluids, both swelling degree and weight losses were higher in phosphate buffer saline (PBS) and for the blends with a higher content of gelatin. These results indicated a better stability of the blends in cell culture medium than in PBS and suggested a mainly hydrolytic degradation process. Cell culture tests, carried out using C2C12 myoblasts, showed a good cell proliferation for all the blends containing more than 60% of gelatin, with the alginate/gelatin 20:80 showing the best response. The same blend was the only one on which cell differentiation was observed. The results obtained in the biological characterization allow to select the alginate/gelatin 20:80 blend as a suitable material to prepare scaffolds for myocardial tissue engineering.

Cell-induced alignment augments twitch force in fibrin gel-based engineered myocardium via gap junction modification

A high-potential therapy for repairing the heart post-myocardial infarction is the implantation of tissue-engineered myocardium. While several groups have developed constructs that mimic the aligned structure of the native myocardium, to date no one has investigated the particular functional benefits conferred by alignment. In this study we created myocardial constructs in both aligned and isotropic configurations by entrapping neonatal rat cardiac cells in fibrin gel. Constructs were cultured statically for 2 weeks, and then characterized. Histological staining showed spread cells that express typical cardiac cell markers in both configurations. Isotropic constructs had higher final cell and collagen densities, but lower passive mechanical properties than aligned constructs. Twitch force associated with electrical pacing, however, was 181% higher in aligned constructs, and this improvement was greater than what would be expected from merely aligning the cells in the isotropic constructs in the force measurement direction. Our hypothesis was that this was due to improved gap junction formation/function facilitated by cell alignment, and further analyses of the twitch force data, as well as Western blot results of connexin 43 expression and phosphorylation state, support this hypothesis. Regardless of the specific mechanism, the results presented in this study underscore the importance of recapitulating the anisotropy of the native tissue in engineered myocardium.

Trends in invasive disease due to Candida species following heart and lung transplantation

Although invasive candidiasis (IC) causes significant morbidity and mortality in patients who undergo heart, lung, or heart-lung transplantation, a systematic study in a large cohort of thoracic organ transplant recipients has not been reported to date. Clinical and microbiological data were reviewed for 1305 patients who underwent thoracic organ transplantation at Stanford University Medical Center between 1980 and 2004. We identified and analyzed 76 episodes of IC in 68 patients (overall incidence 5.2% per patient).The incidence of IC was higher in lung (LTx) and heart-lung transplant (HLTx) recipients as compared with heart transplant (HTx) recipients (risk ratio [RR] 1.7, 95% confidence interval [CI] 1.1-2.7).The incidence of IC decreased over time in all thoracic organ transplant recipients, decreasing from 6.1% in the 1980-1986 time period to 2.1% in the 2001-2004 era in the HTx recipients, and from 20% in the 1980-1986 period to 1.8% in the 2001-2004 period in the LTx and HLTx recipients.The most common site of infection differed between the HTx and LTx cohorts, with bloodstream or disseminated disease in the former and tracheobronchitis in the latter. IC in the first year after transplant was significantly associated with death in both HTx (RR 2.9, 95% CI 1.8-4.6, P=0.001) and LTx and HLTx patients (RR 3.0, 95% CI 1.9-4.6, P<0.001). The attributable mortality from IC decreased during the 25-year period of observation, from 36% to 20% in the HTx recipients and from 39% to 15% in the LTx and HLTx recipients. There were a significant number of cases caused by non-albicans Candida species in all patients, with a trend toward higher mortality in the HTx group. In conclusion, the incidence and attributable mortality of IC in thoracic organ transplant recipients has significantly declined over the past 25 years.The use of newer antifungal agents for prophylaxis and treatment, the decrease in the incidence of cytomegalovirus disease, and the use of more selective immunosuppression, among other factors, may have been responsible for this change.

Cell-based cardiac pumps and tissue-engineered ventricles

Mortalities resulting from cardiovascular disorders remain high, with an urgent need to develop novel treatment modalities. Tissue-engineering therapies aim to provide cell-based alternatives to conventional options. Significant technological advancements have occurred during the last decade towards the fabrication of functional 3D heart muscle in vitro. More recent research has focused on the development of cell-based cardiac pumps and tissue-engineered ventricles. The global objective of this collective work is to simulate the functional performance of the left ventricle, utilizing completely cell-based options. Current prototypes have shown several physiological performance metrics, including the ability of these devices to generate intraluminal pressure upon electrical stimulation. This review will highlight the transition from tissue engineering 3D heart muscle to cell-based cardiac pumps/ventricles.

Technology assessment for the anesthesiologist

The expense associated with modern heath care in the United States is very high, in excess of 15% of the GDP, continues to grow and has become a significant public policy issue. New technologies, defined as all drugs, devices, procedures, and organizational systems, are major contributors to rising health care costs. The use of health technology assessment tools can assist those in leadership positions in making rational decisions as to which new technologies to adopt. The classical approach is to use data from prospective, randomized, clinical trials that compare the outcomes of those treated with the new technology and the accepted therapy. Using this information and detailed economic data, the cost-effectiveness ratio can be determined. The accepted metrics are either dollars per life year saved or dollars per quality-adjusted life year saved. If the new medical intervention costs less than $50,000 to 80,000 dollars per life year saved, it is considered to be cost-effective and worthy of adoption. This kind of analysis is complex and expensive. In addition, the required information is not always available, limiting the applicability of this approach. Finally, the economic analysis often includes down-stream expense and benefit not relevant from a medical center perspective. Another approach is to focus the analysis to what impacts the medical center. This includes determining whether the technology has received the necessary approvals and has been shown to be effective, to improve health outcomes, to be at least as effective as standard therapy, and to be achievable outside the investigative setting. A fiscal analysis also must be done to determine what will it cost to acquire and operate the technology, what are the anticipated patient volumes and payer mix, and what will be the down-stream consequences to the medical center. If the process concludes that the technology works, makes a positive difference to patient care, and is fiscally and operationally acceptable, it should be purchased. After the technology has been installed and has been used, a postimplementation review should be done. This review should go over the same attributes that led to the decision to purchase. It should be determined whether the expected patient volumes, outcomes, income, and expenses were seen. If not, the technology assessment process should be refined to make better decisions in the future. Finally, if the results are at a substantial negative variance from what was anticipated, abandoning the technology should be considered. Anesthesiology either directly controls or indirectly influences a significant portion of medical technology in every medical center. Therefore, the processes that have been discussed in this article should be used by the department of anesthesiology to assure optimal patient care and the fiscal stability of the organization.

Engineering the heart piece by piece: state of the art in cardiac tissue engineering

According to the National Transplant Society, more than 7000 Americans in need of organs die every year owing to a lack of lifesaving organs. Bioengineering 3D organs in vitro for subsequent implantation may provide a solution to this problem. The field of tissue engineering in its most rudimentary form is focused on the developed of transplantable organ substitutes in the laboratory. The objective of this article is to introduce important technological hurdles in the field of cardiac tissue engineering. This review starts with an overview of tissue engineering, followed by an introduction to the field of cardiovascular tissue engineering and finally summarizes some of the key advances in cardiac tissue engineering; specific topics discussed in this article include cell sourcing and biomaterials, in vitro models of cardiac muscle and bioreactors. The article concludes with thoughts on the utility of tissue-engineering models in basic research as well as critical technological hurdles that need to be addressed in the future.

Cardiac tissue engineering in an in vivo vascularized chamber

BACKGROUND

Cardiac tissue engineering offers the prospect of a novel treatment for acquired or congenital heart defects. We have created vascularized pieces of beating cardiac muscle in the rat that are as thick as the adult rat right ventricle wall.

METHOD AND RESULTS

Neonatal rat cardiomyocytes in Matrigel were implanted with an arteriovenous blood vessel loop into a 0.5-mL patented tissue-engineering chamber, located subcutaneously in the groin. Chambers were harvested 1, 4, and 10 weeks after insertion. At 4 and 10 weeks, all constructs that grew in the chambers contracted spontaneously. Immunostaining for alpha-sarcomeric actin, troponin, and desmin showed that differentiated cardiomyocytes present in tissue at all time points formed a network of interconnected cells within a collagenous extracellular matrix. Constructs at 4 and 10 weeks were extensively vascularized. The maximum thickness of cardiac tissue generated was 1983 microm. Cardiomyocytes increased in size from 1 to 10 weeks and were positive for the proliferation markers Ki67 and PCNA. Connexin-43 stain indicated that gap junctions were present between cardiomyocytes at 4 and 10 weeks. Echocardiograms performed between 4 and 10 weeks showed that the tissue construct contracted spontaneously in vivo. In vitro organ bath experiments showed a typical cardiac muscle length-tension relationship, the ability to be paced from electrical field pulses up to 3 Hz, positive chronotropy to norepinephrine, and positive inotropy in response to calcium.

CONCLUSIONS

In summary, the use of a vascularized tissue-engineering chamber allowed generation of a spontaneously beating 3-dimensional mass of cardiac tissue from neonatal rat cardiomyocytes. Further development of this vascularized model will increase the potential of cardiac tissue engineering to provide suitable replacement tissues for acquired and congenital defects.

Myocardial engineering in vivo: formation and characterization of contractile, vascularized three-dimensional cardiac tissue

Engineering cardiac tissue in three dimensions is limited by the ability to supply nourishment to the cells in the center of the construct. This limits the radius of an in vitro engineered cardiac construct to approximately 40 microm. This study describes a method of engineering contractile three-dimensional cardiac tissue with the incorporation of an intrinsic vascular supply. Neonatal cardiac myocytes were cultured in vivo in silicone chambers, in close proximity to an intact vascular pedicle. Silicone tubes were filled with a suspension of cardiac myocytes in fibrin gel and surgically placed around the femoral artery and vein of adult rats. At 3 weeks, the tissues in the chambers were harvested for in vitro contractility evaluation and processed for histologic analysis. By 3 weeks, the chambers had become filled with living tissue. Hematoxylin and eosin staining showed large amounts of muscle tissue situated around the femoral vessels. Electron micrographs revealed well-organized intracellular contractile machinery and a high degree of intercellular connectivity. Immunostaining for von Willebrand factor demonstrated neovascularization throughout the constructs. With electrical stimulation, the constructs were able to generate an average active force of 263 microN with a maximum of 843 microN. Electrical pacing was successful at frequencies of 1 to 20 Hz. In addition, the constructs exhibited positive inotropy in response to ionic calcium and positive chronotropy in response to epinephrine. As engineering of cardiac replacement tissue proceeds, vascularization is an increasingly important component in the development of three-dimensional structures. This study demonstrates the in vivo survival, vascularization, organization, and functionality of transplanted myocardial cells.

Creation of Engineered Cardiac Tissue In Vitro From Mouse Embryonic Stem Cells

Background— Embryonic stem (ES) cells can terminally differentiate into all types of somatic cells and are considered a promising source of seed cells for tissue engineering. However, despite recent progress in in vitro differentiation and in vivo transplantation methodologies of ES cells, to date, no one has succeeded in using ES cells in tissue engineering for generation of somatic tissues in vitro for potential transplantation therapy.

Methods and Results— ES-D3 cells were cultured in a slow-turning lateral vessel for mass production of embryoid bodies. The embryoid bodies were then induced to differentiate into cardiomyocytes in a medium supplemented with 1% ascorbic acid. The ES cell–derived cardiomyocytes were then enriched by Percoll gradient centrifugation. The enriched cardiomyocytes were mixed with liquid type I collagen supplemented with Matrigel to construct engineered cardiac tissue (ECT). After in vitro stretching for 7 days, the ECT can beat synchronously and respond to physical and pharmaceutical stimulation. Histological, immunohistochemical, and transmission electron microscopic studies further indicate that the ECTs both structurally and functionally resemble neonatal native cardiac muscle. Markers related to undifferentiated ES cell contamination were not found in reverse transcriptase–polymerase chain reaction analysis of the Percoll-enriched cardiomyocytes. No teratoma formation was observed in the ECTs implanted subcutaneously in nude mice for 4 weeks.

Conclusions— ES cells can be used as a source of seed cells for cardiac tissue engineering. Additional work remains to demonstrate engraftment of the engineered heart tissue in the case of cardiac defects and its functional integrity within the host’s remaining healthy cardiac tissue.

Cardiac allograft vasculopathy: pathology, prevention and treatment

PURPOSE OF REVIEW

Cardiac transplantation is a recognized therapy for end-stage heart failure. Graft coronary artery disease is a chief determinant of long-term survival following cardiac transplantation. There are multiple purported etiologies for graft coronary artery disease including both immunologic and nonimmunologic factors. Immunologic factors include human leukocyte antigen mismatching, cytokine production, and activation of the cellular immune system. Nonimmunologic factors include diabetes, hypertension, hyperlipidemia, and cytomegalovirus infection, just to name a few. There are also donor and recipient factors including age, prior coronary artery disease in the donor heart, and mode of donor brain death.

RECENT FINDINGS

The diagnosis of graft coronary artery disease is especially difficult, partially due to the de-innervated allograft, as well as to its inherent predilection to affect the medium-sized and smaller arteries in a concentric and diffuse nature. Conventional angiography can overlook this condition because of the lack of eccentric plaques in larger epicardial arteries. Intravascular ultrasonography, by contrast, is more sensitive in detecting graft coronary artery disease but is unable to visualize the entire arterial system. Treatment is challenging and often unrewarding, leading to re-transplantation. Prevention is therefore ideal and involves protection against endothelial injury before and during transplantation as well as after transplantation, with decreased ischemic time, aggressive attention to early rejection, risk factor modification, and close follow-up.

SUMMARY

This review will look at the pathophysiology of graft coronary artery disease, current diagnostic and therapeutic choices, as well as existing and future directions.

A history of pediatric critical care medicine

Critical care medicine developed out of other subspecialties' need to provide care for their most critically ill patients. Advanced technologies, the understanding of the pathophysiology of critical illness, and the development of the multidisciplinary team have made this care possible. Pediatric critical care medicine emerged in the 1960s and has expanded dramatically since then. The field has made major advances in the areas of lung injury, sepsis, traumatic brain injury, and postoperative care. We review here the evolution of modern pediatric critical care medicine from its roots in general pediatric and cardiac surgery, adult respiratory care medicine, neonatology, and pediatric anesthesiology to its current state as a unique discipline.

Role of the β-adrenergic receptor kinase in myocardial dysfunction after brain death

OBJECTIVE

Significant cardiac dysfunction after brain death leading to exclusion from procurement for cardiac transplantation is seen in up to 25% of potential organ donors in the absence of structural heart disease. The cause includes uncoupling of the myocardial beta-adrenergic receptor signaling system. The mechanism, however, has not yet been described. This study investigates our hypothesis that brain death causes acute activation of the betaAR kinase and leads to desensitization of myocardial beta-adrenergic receptors and impaired ventricular function.

METHODS

Adult pigs underwent a sham operation or induction of brain death by means of subdural balloon inflation (n = 8 in each group). Cardiac function was assessed by using sonomicrometry at baseline and for 6 hours after the operation. beta-Adrenergic receptor signaling was assessed at 6 hours after the operation by measuring myocardial sarcolemmal membrane adenylate cyclase activity, beta-adrenergic receptor density, beta-adrenergic receptor kinase expression, and activity.

RESULTS

Induction of brain death led to significantly decreased left ventricular systolic and diastolic function. Basal and isoproterenol-stimulated adenylate cyclase activity was blunted in the brain dead group compared with the sham-operated group (28.3 +/- 4.3 vs 48.3 +/- 7.6 pmol of cyclic adenosine monophosphate.mg(-1) x min(-1) [P = .01] and 54.8 +/- 9.6 vs 114.5 +/- 18 pmol of cyclic adenosine monophosphate x mg(-1) x min(-1) [P < .02]). There was no difference in beta-adrenergic receptor density between the brain dead and sham-operated groups. Myocardial beta-adrenergic receptor kinase expression was 3-fold greater in the brain dead versus sham-operated groups, and membrane beta-adrenergic receptor kinase activity was 2.5-fold greater in the brain dead group compared with that seen in the sham-operated group.

CONCLUSION

Induction of brain death leads to significant left ventricular dysfunction in this porcine model. Cardiac beta-adrenergic receptors are clearly uncoupled after brain death, and our data suggest that the mechanism is acute increase of myocardial beta-adrenergic receptor kinase activity, leading to beta-adrenergic receptor desensitization and ventricular dysfunction.

Use of the implantable cardioverter-defibrillator in long-term survivors of orthotopic heart transplantation

BACKGROUND

Orthotopic heart transplantation is considered an effective treatment for patients with refractory heart failure. The long-term survival of orthotopic heart transplantation recipients has increased over the last several decades, but many long-term survivors of orthotopic heart transplantation develop graft atherosclerosis and associated left ventricular dysfunction. The risk of sudden cardiac death in long-term survivors of orthotopic heart transplantation with these complications is believed to be high. There are no data on the usefulness of implantable cardioverter-defibrillators (ICDs) in this population; therefore, we report our early experience with ICD placement in such patients.

OBJECTIVES

The purpose of this study was to examine the use of ICDs in adults who are long-term survivors of heart transplantation.

METHODS

We retrospectively reviewed all adult patients who underwent orthotopic heart transplantation at Stanford University Hospital (Stanford, CA, USA) from 1980 to 2004. All patients who received an ICD after transplant were included in this study. We reviewed demographic data, medical history, ejection fraction, presence of graft atherosclerosis, indication for ICD placement, and any device therapy delivered.

RESULTS

Of the 925 patients who had orthotopic heart transplantation during this time period, 493 patients were alive at the beginning of the year 2000. Of these patients, 10 ( approximately 2%) had subsequent placement of an ICD. All 10 patients were male. The average age at orthotopic heart transplantation was 37.8 years. The average age at ICD placement was 50.5 years. The average time from orthotopic heart transplantation to ICD placement was 14.6 years. The average ejection fraction at the time of implant was 46.5%. Five of the 10 patients had a low ejection fraction (within this subgroup, the average ejection fraction was 31%, range 15%-45%) and graft atherosclerosis. ICDs were placed because of symptomatic episodes of ventricular tachycardia (3 patients), low ejection fraction and severe graft atherosclerosis without symptoms (3 patients), and after thorough evaluation for otherwise unexplained syncope (4 patients). The average follow-up after device implantation was 13 months. Complications related to ICD placement were an infected ICD system requiring explant in one patient and a lead fracture in another patient. Three patients had subsequent appropriate shocks for ventricular arrhythmias, and one patient underwent a second orthotopic heart transplantation. One patient died of malignancy.

CONCLUSION

Use of the ICD in long-term survivors of orthotopic heart transplantation should be considered in appropriately selected patients. Further data are needed regarding ICD use in this population.