Detection of cardiac allograft rejection and myocyte necrosis by monoclonal antibody to cardiac myosin

Programmed necrosis in cardiomyocytes: mitochondria, death receptors and beyond

Excessive death of cardiac myocytes leads to many cardiac diseases, including myocardial infarction, arrhythmia, heart failure and sudden cardiac death. For the last several decades, most work on cell death has focused on apoptosis, which is generally considered as the only form of regulated cell death, whereas necrosis has been regarded to be an unregulated process. Recent findings reveal that necrosis also occurs in a regulated manner and that it is closely related to the physiology and pathophysiology of many organs, including the heart. The recognition of necrosis as a regulated process mandates a re-examination of cell death in the heart together with the mechanisms and therapy of cardiac diseases. In this study, we summarize the regulatory mechanisms of the programmed necrosis of cardiomyocytes, that is, the intrinsic (mitochondrial) and extrinsic (death receptor) pathways. Furthermore, the role of this programmed necrosis in various heart diseases is also delineated. Finally, we describe the currently known pharmacological inhibitors of several of the key regulatory molecules of regulated cell necrosis and the opportunities for their therapeutic use in cardiac disease. We intend to systemically summarize the recent progresses in the regulation and pathological significance of programmed cardiomyocyte necrosis along with its potential therapeutic applications to cardiac diseases. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Biomarkers of heart transplant rejection: the good, the bad, and the ugly!

Acute cellular rejection (ACR), antibody-mediated rejection (AMR), and cardiac allograft vasculopathy (CAV) are important limitations for the long-term survival of heart transplant recipients. Although much progress has been made in reducing ACR with modern immunosuppressive treatments and continuous biopsy surveillance, there is still a long way to go to better understand and treat AMR, to enable early detection of patients at risk of CAV, and to reduce the development and sustained progression of this irreversible disease that permanently compromises graft function. This review considers the advances made in ACR detection and treatment allowing a more prolonged survival and the risk factors leading to endothelial injury, dysfunction, inflammation, and subsequent CAV, as well as new treatment modalities for CAV. The review also evaluates the controversies around the definition, pathogenesis, and treatment of AMR. To date, much progress is still needed to significantly reduce post-transplant complications and increase graft and patient survival.

Anything but a biopsy: noninvasive monitoring for cardiac allograft rejection

Endomyocardial biopsy has stood the test of time as a surveillance technique; however, the expense, resources required, invasive nature, and low but definite risks have motivated investigators to pursue less invasive techniques. The search for noninvasive surveillance techniques for cardiac rejection have centered on measurements of cardiac function, intragraft electrical events, peripheral proteomic markers of graft micronecrosis, immune activation, and nonimmune accompaniments of rejection. Although several investigations allude to a reasonable negative predictive value of such monitoring, the specificity of these techniques remains poor. Until well-constructed studies not only define the predictive values of noninvasive techniques but also appropriately evaluate the clinical safety of any such approach, invasive endomyocardial biopsy will remain the gold standard.

Measurements of exocrine proteins in the pig pancreas using microdialysis

The authors adapted microdialysis for the study of intrapancreatic exocrine proteins. Immunoreactive cationic and anionic trypsinogen were continuously measured after the insertion of one probe inside the pig pancreas and another placed under the peritoneum on the anterior surface of the gland. The concentration initially declined in the dialysate from the intrapancreatic probe, followed by an increasing tendency until 120 minutes after the insertion, after which a decline to a relative steady state after four to six hours was observed. A dialysate with a lower concentration of enzymes was obtained from the probe on the pancreatic surface. In order to study the turnover of an exogenously administered substance, a microdialysis probe was inserted into the pancreas and human recombinant pancreatic secretory trypsin inhibitor was injected into the pancreatic duct. The inhibitor was cleared from the pancreas with an intrapancreatic half-life of approximately 45 minutes. Membrane function, measured in vitro before and after use in vivo, was not significantly affected after seven hours in the pig pancreas.

Imaging the rejecting heart. In vivo detection of major histocompatibility complex class II antigen induction

BACKGROUND

Mice with abdominal heterotopic heart transplants were studied to determine whether scintigraphic detection of an increase in major histocompatibility complex (MHC) class II antigen expression could be used as a noninvasive method for diagnosing early rejection.

METHODS AND RESULTS

Allografts from C3H/He (H2k) donors were transplanted into BALB/c (H2d) recipients (n = 18). Two of the 18 allografted mice were treated with cyclosporine (15 mg/kg/day), and two isografted mice served as controls. Each mouse was injected intravenously with 100 microCi of 111In-labeled anti-MHC class II monoclonal antibodies (10-2-16 and 14-4-4S) 24 hours before scintigraphy. After imaging, the mice were killed for tissue counting and histopathology. Radiotracer uptake in the grafts reflected the severity of rejection as determined by histopathological criteria. The percent injected dose per gram of tissue in excised grafts was 4.8 +/- 1.8 (mean +/- SD) for normal grafts (n = 8), 11.1 +/- 9.7 for grafts with grade IA rejection (n = 3, NS), 18.0 +/- 3.8 for grafts with grade IIIA rejection (n = 4, p less than 0.001 versus normal), 18.7 +/- 3.2 for grafts with grade IIIB rejection (n = 3, p less than 0.001 versus normal), and 22.6 +/- 5.4 for grafts with severe rejection (grade IV) (n = 3, p less than 0.001 versus normal). Rejecting allografts with lymphocyte infiltration but without significant myocyte necrosis could be identified by this scintigraphic method. In the BALB/c donor-C57BL/6 (H2b, IE-) recipient combination, rejecting allografts were visualized by 14-4-4S (anti-IEk,d,p,r) antibody but not by 10-2-16 (anti-IAk,r,s,f) antibody. This difference shows that class II antigens induced on donor hearts are solely responsible for the antibody uptake in positive scintigrams of rejecting allografts.

CONCLUSIONS

We conclude that 111In-labeled anti-MHC class II antigen antibody imaging is a sensitive and noninvasive method for detecting cardiac allograft rejection.

Indium-labeled presensitized T cells for diagnosis of graft rejection

The aim of this experiment was to test a safe, noninvasive method for necessary, accurate diagnosis of early allograft rejection. Heart-lung allograft was performed heterotopically using Brown Norway (BN) rats as the donor and Lewis (LEW) rats as the recipient. T cell suspensions were prepared from lymphnodes of specifically sensitized LEW rats that had acutely rejected full-thickness BN skin graft. Cell count was adjusted 50 x 10(6) cells/ml. The suspension was incubated in vitro with 111I oxide (1 m Ci-ml). An aliquot of labeled cell suspension containing 40 x 10(6) cells and a total radioactivity of 200 mCi was administered intravenously to each animal 3 and 6 days after heart-lung transplant. The traffic of T cells was followed in vivo and in isolated organs under large field view gamma camera. The gamma camera revealed radioactivity on the graft starting Postoperative Day 5 when the heart was actively beating; no radioactivity was revealed at the site of the isografted organs. The histology showed mild to moderate cellular infiltration parallel to the grade of radioimaging intensity. The injection of indium-labeled presensitized T cells was able to detect the rejection process in an early phase when there are no clinical symptoms of rejection and/or the rejection cascade can be reversed. These results suggest that a similar method can be used in human organ transplantation for early diagnosis of rejection.

Early detection of rejection and assessment of cyclosporine therapy by 111In antimyosin imaging in mouse heart allografts

BACKGROUND. Mice (n = 58) with abdominal heterotopic heart transplants were studied to examine the effectiveness of 111In-labeled antimyosin scintigraphy in the detection of rejection and to determine the consequence of cyclosporine therapy on the results. METHODS AND RESULTS. Allografts from B10D2 donors were transplanted into B6AF1 recipients. Of the 49 allografted mice, 19 were treated with cyclosporine (15 mg/kg.day). Nine isografted mice served as controls. Scintigraphy was performed by injecting 100 muCi 111In antimyosin monoclonal antibody 2-15 days after transplantation. An increase in the ratio of percent dose of antimyosin injected per gram (% dose/g) of the grafted heart (G) to that of the autologous heart (A) (G/A) as well as the increasing percent dose per gram of antimyosin in the grafts reflected the severity of histopathological rejection regardless of the presence or absence of cyclosporine. Scintigraphic images demonstrated unequivocally intense accumulation of 111In in rejected allografts as confirmed by histologically demonstrable myocyte necrosis. The G/A ratio in allografted mice with mildly deteriorated mechanical activity (4.2 +/- 1.0, mean +/- SD) was greater than that in mice with normal contractility (1.8 +/- 0.7) (p less than 0.001), and the necrosis correlated with this modest decline in mechanical function could be scintigraphically identified. Of mice with normally contracting allografts, the G/A ratio was greater in animals with demonstrated myocyte necrosis (2.6 +/- 0.5) than in those without necrosis (1.5 +/- 0.5) (p less than 0.001). In contrast, isografted mice or a subset of allografted mice treated with cyclosporine and not showing evidence of rejection did not manifest any significant change in G/A ratio, nor did they have scintigrams positive for rejection as late as 15 days after transplantation. CONCLUSIONS. These findings suggest that antimyosin scintigraphy is a sensitive and early indicator of cardiac transplant rejection and that it could be useful as a noninvasive method for assessing the efficacy of cyclosporine treatment.

Imaging of myocardial infarction in dogs and humans using monoclonal antibodies specific for human myosin heavy chains

The use of three different monoclonal antibodies specific for human ventricular myosin heavy chains in the visualization of the location and extent of necrosis in dogs with experimental acute myocardial infarction and in humans is described. Using a classic immunohistochemical method or ex vivo analysis of heart slices in dogs with acute myocardial infarction subjected to intravenous injection of unlabeled antimyosin antibodies or antimyosin antibodies labeled with indium-111, it was observed that all antibody fragments specifically reached the targeted necrotic zone less than 2 h after antibody injection and remained bound for up to 24 h. In a limited but significant number of cases (5 of the 12 humans and 11 of 43 dogs), it was possible to image the necrotic zone in vivo as early as 2 to 4 h after antibody injection. In other cases, individual blood clearance variations retarded or even prevented in vivo necrosis detection. Higher antimyosin fixation values were obtained in the necrotic zones in dogs with a rapid blood clearance relative to that of the other dogs. It is concluded that antimyosin antibodies always reached necrotic areas within 2 h. If blood clearance was rapid, in vivo imaging of the necrotic area was possible 2 to 6 h after necrosis, even in humans. In some cases, however, uncontrolled individual variations in the timing required for sufficient blood clearance hampered this rapid in vivo detection of myocardial necrosis.