Combined analysis of allograft inflammatory factor-1, interleukin-18, and Toll-like receptor expression and association with allograft rejection and coronary vasculopathy

In cardiac transplantation settings, the initial myocardial ischemia and reperfusion may cause myocyte tissue injury and the release of allograft inflammatory factor-1 (AIF-1). This in part may trigger the innate immune response through the modulation of Toll-like receptor-2 (TLR-2) and AIF-1 expression and function, causing the release of proinflammatory cytokines. The goal was to demonstrate these markers in the peripheral blood and biopsy specimen from recipients with cardiac allograft rejection and coronary vasculopathy (CV). Peripheral blood and endomyocardial specimens were tested by reverse transcriptase-polymerase chain reaction and immunohistochemistry stains for identification of TLR-2, -4, interleukin-18, and AIF-1 markers and analyzed against clinical rejection grades for rejection. The differences for mRNA transcript levels were determined by one-way analysis of variance. The mRNA expression levels were significantly varied for TLR-2 in monocytes with different rejection grades (P < 0.0001). The mean +/- SEM level of mRNA expression for 3A grade rejection was 64.21 +/- 3.8; grade 1A, 38.4 +/- 3.5; and for Grade 0 was 38.46 +/- 2.8. The TLR-4 mRNA expression was increased but the specificity was not statistically significant. The TLR-2 immunoreactivity was strongly detected in infiltrating mononuclear cells and cardiac myocytes in Grade 3A rejection. AIF-1 expression was increased significantly in the group with 3A rejection and Grade III CV as compared with Grade 0 or 1A. Interleukin-18 receptors were strongly detected in Grade 3A rejection and CV. The expression profiles of AIF-1, TLR-2, and interleukin-18 were correlated with biopsy-proven allograft rejection in both peripheral blood and local tissue, suggesting a potential for diagnostic biomarkers for early detection of allograft rejection.

Down regulation of immuno-detectable cardiac connexin-43 in BALB/c mice following acute fasting

Acute starvation effects for connexin-43 protein expression, in the heart, had not been previously explored. Hence we examined acute fasting on the myocardial immuno-histochemical expression of connexin-43 in 3 groups of 8-week old female BALB/c mice. Groups consisted of control mice (n=5), fasting for 24 h (N=5) and 48 h (N=3). Under light microscopy all control fed cases revealed the presence of some immuno-detectable staining for connexin-43 that is either present or weakly observed in some or all of the regions of interest, that include the cross-sectional left ventricular sub-endocardium, mid-myocardium and papillary muscle. Whereas mice that underwent 24 or 48 h of acute starvation, connexin-43 expression was either difficult to detect visually (N=3) or was completely absent (N=5) at 40x magnification using a light microscope. In starved mice with no membrane staining for connexin-43 we observed an increase in the intracellular accumulation of cytoplasmic connexin-43 expression.

Sympathetic nerve sprouting after orthotopic heart transplantation

BACKGROUND

Although many studies have documented sympathetic re-innervation in transplanted hearts (allografts) using chemical, imaging, and electrophysiologic methods, little histopathologic proof of this process exists.

METHODS AND RESULTS

We used immunohistochemical techniques with antibodies to S-100 protein, to growth-associated protein 43 (GAP43), and to tyrosine hydroxylase (TH) to detect nerves in the left ventricles in allografts from 29 consecutive recipients. Reasons for transplantation included ischemic heart disease (IHD, n=16), non-ischemic dilated cardiomyopathy (DCM, n=12), and both (n=1). We assessed nerve densities (nerves/mm2) with respect to time after transplantation in the endocardium; in the mid-myocardium; and around intramyocardial blood vessels, scars, foci of rejection, and Quilty lesions. Six normal hearts were used for comparison. As in normal hearts, all 29 allografts had epicardial nerve trunks that extended into the mid-myocardium around blood vessels. Although the total number of nerves (S100-positive) progressively decreased over time, GAP43-positive nerves around the blood vessels increased with time (p <0.005). We also observed abundant TH-positive nerves. The density of S100-positive nerves around blood vessels was greater in those undergoing transplantation for IHD (113 +/- 88) than in those with prior DCM (54 +/- 49, p <0.05). Nerve density in each area varied greatly.

CONCLUSIONS

Heterogeneous sympathetic nerve sprouting and re-innervation occurred around blood vessels in the allografts. The magnitude of nerve sprouting increased with time and varied greatly from patient to patient. Patients with IHD had greater nerve sprouting and re-innervation than did those with DCM.

Instantaneous quantitative video intensity heterogeneity: evaluation with low mechanical index contrast echocardiography

BACKGROUND

Instantaneous video intensity of myocardium has been poorly characterized. Myocardial video intensity is usually displayed in the fitted curve from the exponential equation, y = a(1 - e (-bt)). However, information from the fitted curve will be as accurate as the original video intensity data from the perfusion image. Therefore, we sought to characterize the intramyocardial instantaneous video intensity from low mechanical index (MI) contrast echo imaging for variation.

METHOD

Low-MI imaging using a nonlinear cancellation technique was performed on 10 subjects with normal myocardium. Quantitative video intensity was analyzed in five segments in the epicardium and subendocardium, as well as in systole and diastole.

RESULTS

Video intensity varied between the epicardium and endocardium in each of the region that was analyzed, with the greatest variation in the inferior region (P < 0.0001). Diastolic and systolic differences were also present.

CONCLUSION

Instantaneous video intensity is heterogeneous within the myocardium. Differences can result from attenuation, myocardial fiber structure, and even isotropic effects of the contrast agent, and should be taken into account when data are fitted into an exponential function.

Immunocytochemical localization of the endogenous vasoactive peptide apelin to human vascular and endocardial endothelial cells

Apelin, the proposed endogenous peptide ligand of the novel G-protein-coupled receptor APJ, has been shown to possess potent vasodilator and positive inotropic effects in rats and humans in vivo. However, in humans, no endogenous source of apelin has been reported. Therefore, based on the presence of APJ and mRNA encoding apelin in human tissues, we investigated the expression of apelin in fresh-frozen human tissue from right atrium, left ventricle, lung, kidney, adrenal and large conduit vessels using immunocytochemistry. Apelin-like immunoreactivity (apelin-LI) was detected in vascular endothelial cells lining blood vessels in the human heart, kidney, adrenal gland and lung and in endothelial cells of large conduit vessels. Apelin-LI was also present in endocardial endothelial cells lining recesses of the right atrium. Apelin-LI was not present or below the level of detection in cardiomyocytes, Purkinje's cells, pulmonary or renal epithelial cells, secretory cells of the adrenal gland, vascular smooth muscle cells, adipocytes, nerves and connective tissue. The restricted presence of apelin-LI in endothelial cells suggests that endothelial apelin may play a role as a locally secreted cardiovascular mediator acting on APJ receptors present on the vascular smooth muscle and on cardiac myocytes to regulate vascular tone and cardiac contractility.

Simultaneous multisite endocardial mapping of sustained and non-sustained atrial fibrillation in humans

The aim of this study was to investigate the differences between sustained and non-sustained forms of human atrial fibrillation (AF) using multielectrode endocardial recordings. Methods. Sixty-four pole basket catheters were deployed in the right atrium (RA) of 3 groups of patients: 1) patients with persistent AF (> 48 hours); 2) induced sustained AF (> 15 minutes); and 3) induced non-sustained AF (< 15 minutes). Beat to beat AF intervals (FF) were evaluated for each bipole. On the basis of signal characteristics and direction of wavefront propagation, the degree of spatial and temporal organization of AF was assessed. Results. Persistent AF showed the shortest FF intervals (161 ms) and lowest overall degree of AF organization, induced non-sustained AF the longest FF intervals (192 ms) and highest degree of organization. FF intervals of induced sustained AF were only slightly longer (169 ms) compared to persistent AF. Within each AF group, the lateral wall showed the highest degree of organization, the septal region the lowest. Conclusion. In humans, FF interval and overall degree of AF organization were found to increase significantly from sustained to non-sustained AF. Persistent and induced sustained AF, however, only slightly differed in these parameters.

Prichard's structures of the fossa ovalis are not histogenetically related to cardiac myxoma

AIMS

Cardiac myxomas are neoplasms of unknown histogenesis. They are thought to arise from hypothetical subendothelial vasoformative reserve cells or from primitive cells which reside in the fossa ovalis and surrounding endocardium. In 1951 Prichard described a kind of microscopic endocardial structure with a predilection for the interatrial septum, which were suggested to be related to cardiac myxomas. To confirm the existence of Prichard's structures and to clarify their role in the genesis of cardiac myxomas, we examined histologically the fossa ovalis and we performed an immunohistochemical study of the endocardial abnormalities that were found.

METHODS AND RESULTS

A prospective histological study of 100 interatrial septa and an immunohistochemical study of three out of the 12 endocardial abnormalities that were detected, as well as of four conventional cardiac myxomas were accomplished. Antibodies were used to vimentin, CD31, CD34, alpha-smooth muscle actin, S100 protein, thrombomodulin, calretinin and c-kit (CD117), a tyrosine kinase growth factor receptor for stem cell factor usually expressed by embryonic/fetal endothelium. Structures similar to the ones described by Prichard were found in 12% of septa, most of them in the left side of the fossa ovalis. The hearts with these structures were from patients 10 years older than the ones without them (72 +/- 10 versus 62 +/- 16 years, P=0.006). Immunohistochemically the cells comprising Prichard's structures were positive for vimentin, CD31, CD34 and thrombomodulin, and negative for alpha-smooth muscle actin, S100 protein, calretinin and c-kit. Therefore these cells seem to be mature endothelial cells, but not primitive multipotential mesenchymal cells. Furthermore, these cells were not found in the atrial tissue from the bases of any of the conventional cardiac myxomas.

CONCLUSIONS

Our study suggests that there is no apparent relation between Prichard's structures and cardiac myxomas, and that Prichard's minute endocardial deformities are age-related phenomena.

Evidence for increased pyridinoline concentration in fibrotic tissues in diffuse systemic sclerosis

Systemic sclerosis is a generalized disease characterized mainly by the accumulation of collagen in the skin and internal organs. The aim of our study was to determine the amount of collagen cross-link pyridinoline (Pyd) in a variety of fibrotic tissues (skin, fascia, endocardium, bladder) from an autopsy patient with diffuse systemic sclerosis, and to compare these with normal tissues from the same patient. Mean concentrations of Pyd in the fibrotic skin samples (66 mmol/mol collagen) were more than two-times greater than those in the uninvolved normal samples (27 mmol/mol collagen). The increase of Pyd in the endocardium, fascia, and bladder was also markedly higher (1.41 x, 1.26 x and 2.64 x higher than normal samples). The increased deposition of collagen in systemic sclerosis is accompanied by a significantly increased amount of Pyd in the collagen of fibrotic tissues.

Comparative histopathology of endomyocardial biopsies in chagasic and non-chagasic heart transplant recipients

BACKGROUND

Heart transplantation has been an option for the treatment of chagasic (C) cardiomyopathy despite difficulties concerning the control of rejection and reactivation. The parasite-host interaction under the influence of immunosuppressive therapy may affect the immunological response to the graft in a pattern different from that in non-chagasic (NC) patients. The aim of this study was to compare the major histopathological features in heart transplantation in C and NC patients.

METHODS

We studied 293 endomyocardial biopsies from two groups of heart transplanted patients, including 18 C and 15 NC. Both groups had identical surgical and clinical procedure except immunosuppressive therapy was lower in C patients. The histopathological parameters evaluated were the Quilty effect, rejection, C myocarditis reactivation, fibrosis, hypertrophy, and ischemia. In addition, lymphocytic cellular infiltration of myocarditis due to rejection or reactivation was immunophenotyped in the biopsies of both groups with rejection grades 3 to 4, in biopsies with signs of reactivation, and in fragments of the receptor heart with chronic C myocarditis. A search for Trypanosoma cruzi was performed in all biopsies in the C group in which lymphocyte immunophenotyping was done. We used immunofluorescence and confocal microscopy.

RESULTS

The Quilty effect was present in 23% of the biopsies, involving 69.7% of the patients without a significant difference between groups (p = 0.509). Rejection was frequently observed in biopsies with the Quilty effect and the effect often recurred in the same patient. Rejection grades 3 to 4 was more frequent in the C group (p = 0.023). There were 5 episodes of Chagas' disease reactivation with myocarditis in 2 cases. The mean numbers of CD8+ and CD4+ T cells, and the CD4+-to-CD8+ ratio were similar for rejection in both groups (p > 0.05), while the CD4+-to-CD8+ ratio was significantly lower in chronic C myocarditis compared to rejection in the C group (p = 0.043). There was no significant difference in ischemic damage or interstitial fibrosis in the groups but there was a higher frequency of hypertrophy in the NC group (p = 0.007).

CONCLUSIONS

The histopathological features of heart transplantation in C patients did not differ from that in NC patients in regard to the Quilty effect, development of myocardial fibrosis and ischemia. However, the higher involvement of the C group for rejection grades 3 to 4 suggested higher susceptibility to this event. The similarity of the lymphocytic cellular composition for rejection in both groups indicates that C patients respond to immunological stimulus in a similar pattern as NC patients.

Differential expression of RANTES chemokine, TGF-beta, and leukocyte phenotype in acute cellular rejection and quilty B lesions

BACKGROUND

Because of the complexity of the trabeculated endocardial surface and tangential histologic sectioning, the differentiation of acute cellular rejection (ACR) from Quilty B lesions (QB) in endomyocardial biopsies (EMBs) is problematic. We hypothesized that the phenotype chemokine RANTES (regulated upon activation, normal T cell expressed and secreted) expression of infiltrating cells and the pattern of expression of transforming growth factor-beta (TGF-beta) may distinguish ACR from QB. In previous studies, the number of RANTES-positive cells and the expression of TGF-beta correlated with the severity of rejection.

METHODS

We used immunohistochemical techniques to stain sections of human EMBs with only QB (n = 14) or with only ACR (International Society for Heart and Lung Transplantation Grades 1A and 1B, n = 7; Grades 3A and 3B, n = 7) for B (CD20) and T-lymphocytes (CD3), macrophages (CD68), RANTES, and TGF-beta expression. We graded the percentage of positive cells from 0 to 4 (1 = 1% to 25%; 2 = 26% to 50%; 3 = 51% to 75%, and 4 = 76% to 100%).

RESULTS

When ACR was compared with QB, we found no difference in the proportion of myocardial B cells (0.9 +/- 0.3 vs 1.1 +/- 0.3, p = 0.17); however, we found a lesser proportion of T cells (1.8 +/- 0.5 vs. 2.8 +/- 0.9, p <0.01) but more macrophages (2.9 +/- 0.5 vs. 1.1 +/- 0.6, p < 0.0001) in ACR than in QB. We also found more RANTES-positive leukocytes in ACR vs. QB (2.8 +/- 1.3 vs. 1.9 +/- 0.9, p = 0.03). In QB, many endocardial vessels stained for TGF-beta (2.9 +/- 1.6). Myocardial vessels and injured myocytes in both ACR and QB expressed TGF-beta.

CONCLUSIONS

In ACR, although T-lymphocytes are numerous, more than 50% of infiltrating cells are macrophages and more than 50% express RANTES. In QB lesions, more than 50% of infiltrating cells are T-lymphocytes and less that 50% of leukocytes will express RANTES. B cells are present in both ACR and QB, but on average comprise only 25% of the cells present. Thus, a relatively simple immunohistochemical analysis of endomyocardial biopsies may be useful in distinguishing ACR from QB.

Heat shock proteins, HSP25 and HSP70, and apoptosis in developing endocardial cushion of the mouse heart

Formation of the atrioventricular channels and valves from the endocardial cushion occurs through growth and remodeling of the initial endocardial cushion. This process requires balanced coordination of proliferation and apoptosis by still unknown factors. To detect a possible role for the heat shock proteins 25 and 70 (HSP25 and HSP70) as apoptosis-associated proteins and differentiation factors in the development of the endocardial cushion, we analyzed their temporal and regional occurrence during cell proliferation and apoptosis in E11-E17 embryos. The distribution and timing of these events and factors were consistent with the hypothesis that HSP25 is related to myocardial development whereas HSP70 is related to differentiation of the endocardial cushion by cell proliferation and apoptosis.

Identification and localization of TBX5 transcription factor during human cardiac morphogenesis

Mutations in the TBX5 transcription factor gene cause human cardiac malformation in Holt-Oram syndrome. To identify and localize TBX5 during cardiac morphogenesis, we performed immunohistochemical studies of TBX5 protein cardiac expression during human embryogenesis. Specific antibody to human TBX5 was generated in rabbits with a TBX5 synthetic peptide and affinity purification of antiserum. Anti-TBX5 was used in immunohistochemical analyses of human cardiac tissue. In embryonic and adult heart, TBX5 is expressed throughout the epicardium and in cardiomyocyte nuclei in myocardium of all four cardiac chambers. Endocardial expression of TBX5 is only present in left ventricle. Asymmetric left-sided transmyocardial gradients of TBX5 protein expression were observed in embryonic but not adult hearts. Human cardiac expression of TBX5 protein correlates with the cardiac manifestations of Holt-Oram syndrome. TBX5 transmyocardial protein gradients may contribute to normal patterning of the human heart during embryogenesis.

Immunolocalization of the transcription factor Slug in the developing avian heart

Slug is a transcription factor involved in processes such as the formation of mesoderm and neural crest, two developmental events that imply a transition from an epithelial to a mesenchymal phenotype. During late cardiac morphogenesis, mesenchymal cells originate from two epithelia--epicardial mesothelium and cushion endocardium. We aimed to check if Slug is expressed in these systems of epithelial-mesenchymal transition. We have immuno-located the Slug protein in the heart of quail embryos between Hamburger and Hamilton stages HH16 and HH30. In the proepicardium (the epicardial primordium), Slug was detected in most cells, mesothelial as well as mesenchymal. Slug immunoreactivity was strong in the mesenchyme of the endocardial cushions and subepicardium from its inception until HH24, but the immunoreactivity disappeared in later embryos. Only a small portion of the endocardial cells located in the areas of epithelial-mesenchymal transition (atrioventricular groove and outflow tract) were immuno-labelled, mainly between HH16 and HH20. Endocardial cells from other cardiac segments were always negative, except for a transient, weak immunoreactivity that coincided with the development of the intertrabecular sinusoids of the ventricle. In contrast, virtually all cells of the epicardial mesothelium were immunoreactive until stage HH24. The mesenchymal cells that migrate to the heart through the spina vestibuli were also conspicuously immunoreactive. The myocardium was not labelled in the stages studied. Our results stress the involvement of Slug in the epithelial to mesenchymal transition. We suggest that Slug can constitute a reliable marker of the cardiac epithelial cells that are competent to transform into mesenchyme as well as a transient marker of the epithelial-derived mesenchymal cells in the developing heart.

Immunohistochemical localization of modified C-reactive protein antigen in normal vascular tissue

BACKGROUND

The prototypic acute phase reactant, C-reactive protein (CRP), is a serum soluble, cyclic pentameric protein, the concentration of which increases markedly within hours of any tissue-damaging, inflammatory event. However, upon dissociation of its pentameric quaternary structure, CRP subunits undergo a spontaneous and irreversible conformational change. The resulting molecule, termed modified CRP or mCRP, has reduced aqueous solubility and a propensity to aggregate into a matrix-like lattice structure.

METHODS

Using monoclonal antibodies, normal human tissues were immunohistochemically screened for the presence of CRP as well as mCRP antigens.

RESULTS

Significant levels of mCRP were detected in the walls of blood vessels associated with normal human tissues. These data indicate that mCRP is a naturally occurring form of CRP and that it is a tissue-based rather than serum-based molecule.

SIGNIFICANCE

This report describes the localization of a stable form of CRP, mCRP, in blood vessels associated with normal human tissues.

Endothelial growth factor receptors in human fetal heart

BACKGROUND

Endothelial receptor tyrosine kinases include 3 members of the vascular endothelial growth factor receptor (VEGFR) family and 2 members of the angiopoietin receptor (Tie) family. In addition, the VEGF(165) isoform binds to neuropilin-1 (NP-1), a receptor for collapsins/semaphorins. The importance of these receptors for vasculogenesis and angiogenesis has been shown in gene-targeted mice, but so far, little is known about their exact expression patterns in the human vasculature.

METHODS AND RESULTS

Frozen sections of human fetal heart were stained immunohistochemically with receptor-specific monoclonal (VEGFR, Tie) or polyclonal (NP-1) antibodies. The following patterns were observed: The endocardium was positive for VEGFR-1, VEGFR-2, NP-1, Tie-1, and Tie-2 but negative for VEGFR-3. The coronary vessels were positive for Tie-1, Tie-2, VEGFR-1, and NP-1 and negative for VEGFR-2 and VEGFR-3. Myocardial capillaries and epicardial blood vessels stained for VEGFR-1, VEGFR-2, NP-1, and Tie-1; myocardial capillaries and epicardial veins weakly for Tie-2; and epicardial lymphatic vessels for VEGFR-2 and VEGFR-3, weakly for Tie-1 and Tie-2, but not for VEGFR-1 or NP-1.

CONCLUSIONS

The results demonstrate differential expression of the endothelial growth factor receptors in distinct types of vessels in the human heart. This information is useful for the understanding of their roles in physiological and pathological processes and for their diagnostic and therapeutic application in cardiovascular medicine.

Eosinophilic myocarditis associated with dense deposits of eosinophil cationic protein (ECP) in endomyocardium with high serum ECP

A case of eosinophilic myocarditis following high serum levels of eosinophil cationic protein (ECP) is described. A 27 year old woman was admitted with New York Heart Association (NYHA) class III congestive heart failure. A haematological study showed hypereosinophilia with degranulation and vacuoles; the total eosinophil count was 7980/ml and the ECP serum concentration was noticeably high at 150 ng/ml. Endomyocardial biopsy from the right ventricle showed infiltration of eosinophils and dense deposits of ECP in the endocardium as well as the myocardium. Steroid treatment returned the total eosinophil count and serum ECP to normal, with satisfactory improvement in clinical features. Eosinophilia may cause cardiac damage, and this report confirms that eosinophil degranulation is toxic. Thus, serum ECP seems to be a reliable indicator for diagnosis and for determining treatment parameters of eosinophilic myocarditis.

Fas expression and apoptosis correlate with cardiac dysfunction in patients with dilated cardiomyopathy

Fas is a transmembranous glycoprotein that mediates apoptosis. To elucidate the roles of Fas and of myocyte apoptosis in patients with dilated cardiomyopathy (DCM), the expression of Fas and the fragmentation of DNA were compared in endomyocardial biopsy specimens obtained from patients with DCM. Endomyocardial biopsy was performed on 19 subjects (16 with DCM and 3 control subjects) who also underwent cardiac catheterization and echocardiography. Fas and bcl-2 expression were assayed immunohistochemically, and in situ TdT staining was performed to estimate the number of apoptotic cells. Samples from the DCM patients stained more intensely with anti-Fas antibody than those from control patients (p<0.05). The percentage of in situ TdT-positive cells was significantly higher in the DCM group than in the control group (p<0.05). A correlation between Fas expression and in situ TdT staining was observed in 67% of myocytes in the DCM group. Moreover, the percentage of in situ TdT staining was significantly higher in subjects with severely impaired left ventricular systolic function than in those whose systolic function was mild to moderately impaired, or who had normal systolic function (p<0.05). The samples showed little expression of bcl-2. These results suggest that Fas expression and apoptosis may be involved in the progression of cardiac dysfunction in DCM.

Production of the transforming growth factor-beta binding protein endoglin is regulated during chick heart development

The early embryonic heart consists of two cell types. The cells form an inner epithelial tube of endocardium within an outer tube of myocardium separated by a cell-free extracellular matrix. A crucial process in heart development is the production of cushion mesenchyme in the atrioventricular (AV) canal and outflow tract (OT). Cushion mesenchyme differentiates from the endocardium in response to signaling molecules produced by the adjacent myocardium. In chicken hearts, both transforming growth factor-beta3 (TGF-beta3) and TGF-beta2 are present and have been identified as being important in the production of cushion mesenchyme. We were interested in how the signals from these two similar molecules may be differentiated during early heart development. To this end, we examined the expression of endoglin, a TGF-beta receptor molecule, in the developing chick heart. Endoglin is typically located on endothelial cell layers and binds tightly to TGF-beta1 and TGF-beta3 but not well to TGF-beta2. We show that during the formation of the primitive heart tube, endoglin is found at relatively high levels in both presumptive myocardium and endocardium. However, as myocardium differentiates and development proceeds, endoglin expression is progressively reduced. At stage 20 in the heart, endoglin expression is most readily seen in the AV canal and the OT. This pattern of expression is similar to the reported TGF-beta3 expression patterns in the heart.

The Cspg2 gene, disrupted in the hdf mutant, is required for right cardiac chamber and endocardial cushion formation

The heart defect (hdf) mouse is a recessive lethal that arose from a transgene insertional mutation on chromosome 13. Embryos homozygous for the transgene die in utero by embryonic day 10.5 postcoitus and exhibit specific defects along the anterior-posterior cardiac axis. The future right ventricle and conus/truncus of the single heart tube fail to form and the endocardial cushions in the atrioventricular and conus/truncus regions are absent. Because the hdf mouse mutation provided the opportunity to identify a gene required for endocardial cushion formation and for specification or maintenance of the anterior most segments of the heart, we initiated studies to further characterize the phenotype, clone the insertion site, and identify the gene disrupted. Chromosome mapping studies first identified the gene, Cspg2 (versican), as a candidate hdf gene. In addition, an antibody recognizing a glycosaminoglycan epitope on versican was found to be positive by immunohistochemistry in the extracellular matrix of normal wild-type embryonic hearts, but absent in homozygous hearts. Expression analysis of the Cspg2 gene showed that the 6/8, 6/9, and 7/9 Cspg2 exon boundaries were present in mRNA of normal wild-type embryonic hearts but absent in the homozygous mutant embryos. DNA sequence flanking the transgene was used to isolate from a normal mouse library overlapping genomic DNA segments that span the transgene insertion site. The contiguous genomic DNA segment was found to contain exon 7 of the Cspg2 in a position 3' to the transgene insertion site. These four separate lines of evidence support the hypothesis that Cspg2 is the gene disrupted by the transgene insertion in the hdf mouse line. The findings of this study and our previous studies of the hdf insertional mutant mouse have shown that normal expression of the Cspg2 gene is required for the successful development of the endocardial cushion swellings and the embryonic heart segments that give rise to the right ventricle and conus/truncus in the outlet of the looped heart.

Changes in diastolic function and collagen content in normotensive and hypertensive rats with long-term streptozotocin-induced diabetes

We investigated the relationship between left ventricular diastolic function and interstitial collagen content in the endocardium, mesocardium and epicardium of transverse sections of the heart, using an image analysis system in normotensive and hypertensive long-term streptozotocin (STZ) diabetic rats. STZ-induced diabetes was characterised by elevated blood glucose, polyuria, polydypsia and loss of body weight. In vivo systolic blood pressure was 165 +/- 4, 136 +/- 3 and 129 +/- 7 mmHg in hypertensive and normotensive diabetic rats and age-matched controls, respectively. Heart rate was significantly lower (P < 0.01) in diabetic rats (283 +/- 8 and 280 +/- 10 beats min-1 in normotensive and hypertensive rats, respectively) than controls (393 +/- 18 beats min-1). Pressure-volume (P-V) curves were studied in isolated Langendorff perfused hearts at rest and after 20 min global ischaemia and 30 min reperfusion 6 months after induction of diabetes. Left ventricular volumes were significantly smaller in diabetic rats than age-matched controls, but volumes normalised for heart weight were higher in normotensive (by 28%) and hypertensive (by 10%) diabetic rats. Slopes of end-diastolic P-V curves were similar between groups in basal conditions, but left ventricular systolic P-V curves were steeper in normotensive and flatter in hypertensive diabetic hearts. Post-ischaemic left ventricular end-diastolic pressure was significantly higher than the pre-ischaemic value at comparable increments of volume in each group. Collagen content significantly increased in the heart of rats with STZ-diabetes both in the free left ventricular wall and septum, and suggested this may play a role in the cardiac defects in contractility and relaxation in our experimental conditions. These results indicate that diabetes, irrespective of associated hypertension, can cause major changes in cardiac performance and susceptibility to ischaemia and reperfusion.

Angiotensin receptor type 1 mRNA in human right ventricular endomyocardial biopsies: downregulation in heart failure

OBJECTIVE

Atrial angiotensin II receptors type 1 (AT1) are downregulated in end-stage human heart failure at mRNA and protein level. The present study investigated whether AT1 ventricular mRNA content was reduced in myocardial biopsies from heart failure patients.

METHODS

AT1 mRNA was quantitated in right ventricular endomyocardial biopsies from 16 patients with decreased left ventricular function (LVEF 36 +/- 3%) due to dilated cardiomyopathy (DCM) and in biopsies from 12 patients with suspected myocardial disease but normal cardiac function (LVEF 62 +/- 2%). Two biopsies per patient were pooled, RNA was extracted and reverse-transcribed after addition of an AT1 cRNA standard. AT1 standard and wild-type RNA were amplified with the same primers in the same PCR tube. The PCR products were hybridized to a microtiter plate and detected and quantitated by an ELISA system. Glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA was determined in the same samples as AT1 mRNA.

RESULTS

In the biopsies from 16 patients with heart failure, a 68% decrease in AT1 mRNA content was found in comparison with 12 controls (heart failure 94 +/- 15 AT1 mRNA copies/ng RNA; controls 297 +/- 45; P < 0.001). Relating AT1 mRNA content to GAPDH mRNA confirmed the specific decrease in AT1 mRNA (AT1/GAPDH: heart failure 1.3 +/- 0.15; controls 3.4 +/- 0.5; p < 0.002). The best correlation between AT1 mRNA content and clinical parameters was found for right ventricular ejection fraction (r = 0.59, P < 0.01).

CONCLUSIONS

The quantitative RT-PCR procedure indicated a loss of ventricular AT1 mRNA in human heart failure which corresponds to the loss of AT1 protein described previously. It may underlie the decrease in AT1 protein expression in human heart failure.

Echocardiographic patterns of myocardial fibrosis in hypertensive patients: endomyocardial biopsy versus ultrasonic tissue characterization

Echocardiographic image texture has been demonstrated to reflect the physical properties of the tissue under examination. To evaluate the role of collagen in determining the echo pattern of the left ventricular wall, we studied nine hypertensive patients with left ventricular hypertrophy (left ventricular mass index > 125 gm/m2) and biopsy-proven different degrees of myocardial fibrosis by analyzing the echocardiographic examinations performed before the biopsy. Myocardial tissue was sampled under fluoroscopy and two-dimensional echo guidance in the interventricular septum. Collagen volume fraction (CVF; normal range up to 2%) was taken as an index of fibrosis. The echo patterns were assessed by analyzing standard two-dimensional parasternal long-axis echocardiograms recorded on videotape. Images were color-coded at 256 levels (0 = yellow, 256 = black) and digitized off-line onto a personal computer. The region of analysis was set using a selection tool (20 x 10 mm) in the general area of septum where the specimen was taken. For each selection a color-level histogram, representing the frequency distribution, was derived with estimates of the average pixel intensity (mCS), skewness (SK), kurtosis (K), and the broad band (Bb) of the echoes about the distribution. Echo-derived parameters in each patient were compared with corresponding CVF values. CVF was out of range in all patients, ranging from 2.6% to 7.6% (mean 4.3% +/- 1.6%). No correlation was found between CVF and mCS, whereas a significant correlation was found at end diastole between CVF and the parameters describing histogram morphology, respectively, SK (r = 0.73), K (r = 0.69), Bb (r = 0.72). These findings for the first time demonstrate in vivo in hypertensive patients with left ventricular hypertrophy an agreement between echo amplitude and histologically assessed collagen volume. Thus in our studied patients collagen content appears to be the major determinant of regional echo intensity, its increase resulting in a significant and progressive wider asymmetrical left shift (yellow) of the color histogram.

Expression of smooth muscle alpha-actin in mesenchymal cells during formation of avian endocardial cushion tissue: a role for transforming growth factor beta3

During early cardiac morphogenesis, outflow tract (OT) and atrio-ventricular (AV) endothelial cells differentiate into mesenchymal cells, which have characteristics of smooth muscle-like myofibroblasts, and which form endocardial cushion tissue, the primordia of valves, and septa in the adult heart. During this embryonic event, transforming growth factor beta3 (TGF beta3) is an essential element in the progression of endothelial-transformation into mesenchyme. TGF beta(s) are known to be a potent inducer for mesodermal differentiation and a promoter for differentiation of endothelial cells into smooth muscle-like cells. Using a monoclonal antibody against smooth muscle-specific alpha-actin (SMA), we examined the immunohistochemical staining of this form of actin in avian endocardial cushion tissue formation. To determine whether TGF beta3 initiates the expression of SMA, the pre-migratory AV endothelial monolayer was cultured with or without chicken recombinant TGF beta3 and the expression of SMA was examined immunochemically. Migrating mesenchymal cells expressed SMA beneath the cell surface membrane. These cells showed a reduction of endothelial specific marker antigen, QH1. Stationary endothelial cells did not express SMA. The deposition of SMA in the mesenchymal tissue persisted until the end of the fetal period. Pre-migratory endothelial cells cultured in complete medium (CM199) that contained TGF beta3 expressed SMA, whereas cells cultured in CM199 alone did not. At the onset of the endothelial-mesenchymal transformation, migrating mesenchymal cells express SMA and the expression of this form of actin is upregulated by TGF beta3. The induction of the expression of SMA by TGF beta3 is one of the initial events in the cytoskeletal reorganization in endothelial cells which separate from one another during the initial phenotypic change associated with the endothelial-mesenchymal transformation.

The fate diversity of mesodermal cells within the heart field during chicken early embryogenesis

In gastrulation stage embryos of birds and mammals, the heart field is established as mesodermal crescents flanking the area rostrolateral to Hensen's node. Subsequent fusion of the bilateral heart primordia gives rise to a single tubular heart consisting of two epithelial layers: an outer myocardium and an inner endocardium. To date, it is uncertain whether these two distinct cell types of the heart arise from common or separate progenitor populations of mesodermal cells within the heart field. By retroviral single cell marking and tracking, we examined the diversity of cell populations present in the heart field of stage 4 chicken embryos. Here we demonstrate that individual mesodermal cells in the heart field gave rise to a clone consisting only of one cell type, either endocardial or myocardial cells; i.e., 95.1% of the mesoderm-derived clones were localized in the myocardium, while 4.9% of them were found in endocardium. No clones containing both of these two cell types were detected. The results suggest that the heart field mesoderm at stage 4 consists of at least two distinct subpopulations, containing more premyocardial cells than preendocardial cells. If there exists a common precursor of both myocardial and endocardial cells, the lineage diversification must occur at or prior to the arrival of mesodermal cells to the heart field.

Glucose metabolism distal to a critical coronary stenosis in a canine model of low-flow myocardial ischemia

Myocardial regions perfused through a coronary stenosis may cease contracting, but remain viable. Clinical observations suggest that increased glucose utilization may be an adaptive mechanism in such "hibernating" regions. In this study, we used a combination of 13C-NMR spectroscopy, GC-MS analysis, and tissue biochemical measurements to track glucose through intracellular metabolism in intact dogs infused with [1-13C]glucose during a 3-4-h period of acute ischemic hibernation. During low-flow ischemia [3-13C]alanine enrichment was higher, relative to plasma [1-13C]glucose enrichment, in ischemic than in nonischemic regions of the heart, suggesting a greater contribution of exogenous glucose to glycolytic flux in the ischemic region (approximately 72 vs. approximately 28%, P < 0.01). Both the fraction of glycogen synthase present in the physiologically active glucose-6-phosphate-independent form (46 +/- 10 vs. 9 +/- 6%, P < 0.01) and the rate of incorporation of circulating glucose into glycogen (94 +/- 25 vs. 20 +/- 15 nmol/gram/min, P < 0.01) were also greater in ischemic regions. Measurement of steady state [4-13C)glutamate/[3-13C]alanine enrichment ratios demonstrated that glucose-derived pyruvate supported 26-36% of total tricarboxylic acid cycle flux in all regions, however, indicating no preference for glucose over fat as an oxidative substrate in the ischemic myocardium. Thus during sustained regional low-flow ischemia in vivo, the ischemic myocardium increases its utilization of exogenous glucose as a substrate. Upregulation is restricted to cytosolic utilization pathways, however (glycolysis and glycogen synthesis), and fat continues to be the major source of mitochondrial oxidative substrate.

Cardiac myxoma is rich in factor XIIIa positive dendrophages: immunohistochemical study of four cases

Cardiac myxoma is an enigmatic tumour thought to arise from primitive cardiac mesenchymal cells. Factor XIIIa+ dendrophages are tissue histiocytes that are active in tissue repair and thrombosis. To explore whether factor XIIIa+ dendrophages play a role in cardiac myxoma morphogenesis, we stained four cases with an antiserum against coagulation factor XIIIa (FXIIIa). We also used antibodies recognizing CD34, CD31, and S-100 protein. Samples of valvular endocardium from 12 and 16 week fetuses and two adult autopsies were compared with the four myxomas. All cardiac myxomas had rounded and dendritic FXIIIa+ cells admixed with more numerous CD34+ spindle and stellate myxoma cells. The CD34+ cells formed multicellular syncytia and capillary sprouts. Many of these syncytial structures also expressed CD31 and, to a lesser extent, S-100 protein, strongly in two cases and more focally in two. Fetal subendocardium was composed of CD34+ stellate fibroblast-like cells invested with scattered FXIIIa+ histiocytes; no S-100+ cells were detected. Our findings confirm that cardiac myxomas are composed of CD34+ primitive subendocardial cells. These cells show a capacity for CD31+ endothelial differentiation. In cardiac myxoma, the CD34+ myxoma cells are accompanied by numerous FXIIIa+ dendrophages, the presence of which suggests abnormal organizing thrombus-like differentiation in cardiac myxoma morphogenesis.

Collagen content in normal, pressure, and pressure-volume overloaded developing human hearts

Increased myocardial collagen accompanies pressure overload of the adult left ventricle. This phenomenon is poorly understood in infants. This study compares the myocardial volume fraction of collagen in infants who did not have primary heart disease with infants with isolated pressure overload of the right ventricle (tetralogy of Fallot [ToF]), and with infants with combined volume and pressure overload (aortic valve atresia [AVA]). The distribution of collagen in the neonatal myocardium was also determined. We measured the volume fraction of collagen from right ventricular biopsy specimens of cadaver hearts in normal infants (1 to 9 months old; n = 7), infants with ToF (1 day to 9 months old; n = 9), newborns with AVA (AVA-NB) (1 to 4 days old; n = 5), and older patients with AVA (AVA-I) (5 to 8 months old; n = 5). Myocardium from 3 patients undergoing repair of ToF (6 to 8 months old) was also analyzed. Specimens were stained with Masson's trichrome and myocardial volume fraction of collagen determined by point counting. Myocardial volume fraction of collagen was significantly higher (p = 0.02) in AVA-I patients (8.0 +/- 3.5%) versus normal (3.3 +/- 2.7%), ToF (3.2 +/- 1.8%), and AVA-NB (3.5 +/- 2.3%) patients. There was a tendency for increased collagen in the subendocardium, especially in AVA-I patients (p > 0.05). We conclude that patients with AVA-I have increased collagen relative to normal subjects, patients with ToF, and patients with AVA-NB, and that this increase is greatest in the subendocardium.

Fibulin-1, vitronectin, and fibronectin expression during avian cardiac valve and septa development

BACKGROUND

Extracellular matrix (ECM) proteins have been implicated as mediators of events important to valvuloseptal development (reviewed by Little and Rongish, Experentia, 51:873-882, 1995). The aim of this study was to identify connective tissue ECM proteins present at sites of valvuloseptal morphogenesis, and to determine how their patterns of expression change during the developmental process.

METHODS

Immunofluorescence microscopy was used to examine the distribution of fibulin-1, vitronectin, and fibronectin in the embryonic chicken heart over a broad developmental time frame (Hamburger and Hamilton stages 14 to 44), emphasizing stages that illustrate endocardial cushion formation, growth, fusion, and development into valvuloseptal components.

RESULTS AND CONCLUSIONS

Fibulin-1 immunolabeling was concentrated in endocardial cushions, notably at boundaries with the myocardium, during stages when the cushions are differentiating into valvular and septal components. Fibulin-1 was detected in the endocardial cushions prior to their seeding with cushion cells, but became undetectable by early midgestation. Vitronectin expression was similar to fibulin-1, but less restricted in its distribution. Vitronectin was observed before endocardial cushion cell migration commenced and persisted until the formation of prevalvular structures (early midgestation) in the atrioventricular cushions. Vitronectin remained detectable in the semilunar valves until late midgestation. Fibronectin was present in the endocardial cushion region and in portions of the endocardium and myocardium throughout the stages presented. Our data suggests that the ECM of the endocardial cushions undergoes remodelling in a regionally and temporally specific manner which corresponds with morphogenetic changes during valvuloseptal development.

Expression of cytokine genes and presence of enteroviral genomic RNA in endomyocardial biopsy tissues of myocarditis and dilated cardiomyopathy

Viral infection, especially by enteroviruses, has been considered to be the most common cause of myocarditis, which may progress to dilated cardiomyopathy (DCM). Although the mechanism of progression remains uncertain, a cytokine-associated injury of myocytes has been proposed. Using reverse transcriptase polymerase chain reaction (RT-PCR), we examined the expression of interleukin 1 beta (IL-1 beta), IL-6, IL-8 and tumour necrosis factor alpha (TNF-alpha) and the presence of enteroviral genomic RNA in endomyocardial biopsy tissues obtained from patients with myocarditis and DCM. We examined endomyocardial biopsy tissues obtained from 6 patients with myocarditis, 21 with DCM and 15 with non-infectious cardiac diseases as controls. In patients with myocarditis, endomyocardial biopsy was performed twice at an interval of 1 month to 8 years after the onset of myocarditis. We used RT-PCR to detect IL-1 beta, IL-6, IL-8 and TNF-alpha genes expression and nested RT-PCR (nRT-PCR) to detect enteroviral genomic RNA. IL-1 beta, IL-6, IL-8 and TNF-alpha genes were expressed in 100% (6/6) and enteroviral genomic RNA in 67% (4/6) of myocarditis patients at the first biopsy. At the second biopsy, IL-1 beta, IL-6, IL-8 and TNF-alpha genes were expressed in none, 50% (3/6), 67% (4/6) and 67% (4/6), respectively, and enteroviral genomic RNA in 67% (4/6). Four patients with myocarditis, in whom IL-8 and TNF-alpha genes and enteroviral genomic RNA were detected, progressed to DCM at the second biopsy. IL-1 beta, IL-6, IL-8 and TNF-alpha genes were expressed in none, 24% (5/21), 38% (8/21), 57% (12/21) of DCM patients, respectively. Enteroviral genomic RNA was detected in 43% (9/21) of DCM. Neither cytokine expression nor enteroviral genomic RNA were detected in the controls. the high incidence of cytokines, especially IL-6, IL-8 and TNF-alpha, expression in myocarditis and DCM, which might be induced by enteroviral infection, suggests that cytokines play an important role in myocytic damage leading to DCM.

Presence of contractile-type smooth muscle cells in the endocardium

A smooth muscle layer exists in the parietal endocardium. Notwithstanding previous pioneer work, little has been known on the phenotypes of these smooth muscles. In humans as in animals, smooth muscles show two distinct phenotypes, the 'synthetic' and 'contractile' states, which can be differentiated on the basis of the expression of two types of myosin heavy chain isoforms, SM1 and SM2. In this study, using SM1- and SM2-specific monoclonal antibodies, we performed immunohistochemical examinations to determine the phenotype of the endocardial smooth muscles. We report here that the endocardial smooth muscles have the contractile phenotype.

Applicability of small endomyocardial biopsies for evaluation of high energy phosphates and glycogen in the heart

To evaluate variability of biochemical determination of energy stores in endomyocardial biopsies, we compared myocardial contents of high energy phosphates and glycogen in endomyocardial and transmural myocardial biopsies from 12 75-kg pigs before, during, and after cardioplegia. Before cardioplegia, comparable amounts of adenine nucleotides and glycogen were found in left and right ventricular endomyocardial and left ventricular transmural biopsies. Phosphocreatine levels were lower in endomyocardial than in transmural biopsies. Significant correlations were observed between endomyocardial and transmural adenine nucleotide and glycogen contents but not phosphocreatine content. During cardioplegia, myocardial ATP and phosphocreatine contents increased and glycogen concentration tended to decrease. During reperfusion, ATP and glycogen levels decreased, whereas phosphocreatine levels increased remarkably. Transmural changes in left ventricular adenine nucleotide and glycogen levels were reflected in endomyocardial biopsies but those in phosphocreatine were not. By increasing the number of endomyocardial biopsies from one to three, within-subject variance was reduced from 33-47% to 14-23% of total variance whereas four or more biopsies only added minor further reduction in variability. In conclusion, endomyocardial biopsies yield representative estimates of the average myocardial content of adenine nucleotides and glycogen but not of phosphocreatine in the normal heart. Endomyocardial biopsies offer a sensitive estimate of the changes in myocardial adenine nucleotides and glycogen induced by cardioplegia and reperfusion. However, metabolite content in endomyocardial biopsies shows a high variability. Three or more endomyocardial biopsies are necessary to reduce variability to acceptable levels.

Novel technique to bioassay endocardium-derived nitric oxide from the beating heart

Nitric oxide is a potent vasodilator and antiplatelet substance released by the vascular endothelium. In the current study, isolated rabbit hearts were perfused retrograde in the aortic root with a balanced salt solution using a Langendorff technique. To perfuse the right cardiac chambers, an inflow cannula was placed in the superior vena cava and an outflow cannula in the right ventricular apex via the pulmonary artery. To detect endocardial vasodilator production, right heart perfusate was used to bathe a "bioassay" segment of canine coronary artery denuded of endothelium. Perfusate from unstimulated hearts did not alter smooth muscle tone in the bioassay tissue. Calcium inophore, a potent stimulus for endothelial nitric oxide production, produced relaxation of the bioassay smooth muscle when added to the cardiac perfusate but not when applied directly to the bioassay segment. Cardiac effluent vasodilator activity was abolished by removal of the endocardium or addition of nitric oxide synthesis inhibitors, but not by prostanoid inhibitors. These experiments describe a practical method to bioassay endocardial nitric oxide production in the beating heart.

Cardiac dystrophin abnormalities in Becker muscular dystrophy assessed by endomyocardial biopsy

Duchenne and Becker muscular dystrophy (DMD/BMD) are allelic variants caused by mutations in gene-encoding dystrophin. Abnormal expression of dystrophin in skeletal muscle has been shown to correlate with severity of disease. However, in BMD the severity of skeletal and cardiac involvement are not well correlated. We studied the immunostaining pattern of cardiac dystrophin in endomyocardial biopsy specimens from 83 patients with heart disease. Immunohistochemical assessment of dystrophin in four patients with BMD and cardiomyopathy showed a variable distributions of myocytes with continuous, discontinuous, or absent membrane immunostaining patterns. These patterns were obviously different from patterns of other heart diseases. We conclude that the discontinuous immunostaining pattern of cardiac dystrophin is characteristic of BMD and that an absent pattern may be associated with more severe cardiac dysfunction. Because genetic analysis cannot determine the correct diagnosis in 35% of DMD/BMD cases, we recommend routine examination of immunostaining patterns of dystrophin in endomyocardial biopsy specimens in patients with cardiomyopathy suspected to be the result of BMD.

Grade 2 cellular heart rejection: does it exist?

According to the International Society for Heart and Lung Transplantation, a single focus of lymphocytic infiltration associated with myocyte injury in a cardiac allograft endomyocardial biopsy is focal moderate cellular rejection (Grade 2). We reviewed 115 endomyocardial biopsy specimens that were completely negative (n = 17), had a Quilty A (n = 17) or Quilty B (n = 46) lesion, or had a lesion fulfilling the criteria of grade 2 rejection (n = 35). By studying step sections (mean = 18) or sections stained for elastic tissue and collagen, we showed continuity of the focus of grade 2 rejection with the endocardium in 32 of 35 cases; these results justify reclassification of these foci as Quilty B lesions, which are defined as endocardial infiltrates that encroach on the underlying myocardium and that may be associated with myocyte injury but are not generally considered to represent acute rejection. Immunohistochemical staining for T and B lymphocytes and histiocytes showed similar patterns in deeper zones of Quilty B lesions and lesions initially regarded as grade 2 rejection. Normal hemodynamics were observed with 16 of 17 completely negative biopsy specimens, 16 of 17 Quilty A biopsy specimens, 46 of 46 Quilty B biopsy specimens, and 35 of 35 grade 2 rejection biopsy specimens. No grade 2 rejection was treated; only 1 biopsy specimen progressed to grade 3A rejection in a subsequent biopsy 2 months later. Most, if not all, cases of grade 2 cellular rejection can be shown to be Quilty B lesions, are not associated with hemodynamic abnormalities, and do not require augmented immunosuppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Dilated cardiomyopathy: computer-assisted analysis of endomyocardial biopsy protein patterns by two-dimensional gel electrophoresis

In order to identify disease-associated alterations in the myocardial protein patterns in dilated cardiomyopathy, we used 2-dimensional gel electrophoresis to analyse the proteins of endomyocardial biopsies from patients and controls. Proteins (150 micrograms) from biopsies (1-3 mg wet weight) were first separated by isoelectric focusing, then applied to large 2-dimensional gels. A computer-assisted system (PDQUEST) was used for spot detection, quantification and comparison of 2-dimensional protein patterns. From a single endomyocardial biopsy about 1000 different protein species were resolved. The spot pattern was influenced by the concentration of protein during sample preparation, by the amount of protein loaded onto the gels and by the development time of silver staining. Variances of spot position in the first and second dimension and in the long diagonals were less than 5%. Coefficients of variance for the spot quantities in 8 gels were 16 +/- 8%. Contaminating blood proteins could be identified in the biopsy patterns. Computer-assisted comparison between cardiomyopathy (n = 5) and controls (n = 5) over the whole gel revealed that 55 protein spots were increased 100%, 27 protein spots decreased 100%. Four proteins showed significant quantitative differences between the cardiomyopathic hearts and controls. Fourteen proteins were identified by amino acid analysis or microsequencing. An isoelectric point and molecular mass grid was laid over the whole gel based on these identified protein species, resulting in approximate isoelectric point values and molecular masses for all other protein species. Thus, myocardial 2-dimensional protein patterns obtained from endomyocardial biopsies can be used for the characterization of cardiac diseases.

The mouse tie receptor tyrosine kinase gene: expression during embryonic angiogenesis

Angiogenesis, the process by which new blood vessels are formed, is essential in reproduction, development, wound repair and oncogenesis. Endothelial receptor tyrosine kinases are likely to play key roles in the intercellular signalling controlling angiogenesis. We have here analysed the expression of the endothelial receptor tyrosine kinase tie during the earliest stages of vascular development. The mouse tie cDNA was isolated and sequenced and the exon structure of the coding region was determined. The part of the tie gene encoding the extracellular domain was found to be organized in exons specifying the characteristic domains of the Tie polypeptide. Early postimplantation mouse tissues were analysed for tie expression by in situ hybridization. No tie mRNA was detected in 7.5 day mouse embryos. In 8.5 day embryos, tie expression was observed in differentiating angioblasts of the head mesenchyme, in the splanchnopleure and dorsal aorta as well as in migrating endothelial cells of the developing heart. A weak tie signal was also obtained from angioblasts in the blood islands of the yolk sac. Furthermore, tie mRNA was prominent in the endocardium of the embryo and in the endothelial cells forming the lung vasculature. Expression of tie persisted in the lung capillaries of adult mice, but was decreased in the endocardium. These results suggest that the tie receptor tyrosine kinase is involved in angiogenesis and/or maintenance of endothelial cell functions.

Transmural saturation transfer analysis of the creatine kinase system in the mammalian heart

31P NMR spatial localization and saturation transfer techniques were combined to enable the transmural measurement of the forward creatine kinase (CK) rate (ATP:creatine N-phosphotransferase, EC 2.7.3.2.) in the in vivo canine myocardium. Five epicardial towards endocardial regions of the left ventricle (LV) were simultaneously examined using spatially localized voxels. Although intraleft ventricular CP/ATP ratios were constant, the pseudo first order rate constant (k') and the forward creatine kinase rate (Rf) displayed a 61% variation across the LV wall. Because CK levels and calculated [ADP], [CP] and pH are transmurally invariant in the normal left ventricle, the observed changes in the Rf could not be explained by changes in the absolute levels of these substrates and of creatine kinase. In addition, because myocardial oxygen consumption rates are known to be higher in the endocardium, these results imply that forward creatine kinase rates are not directly related to oxidative phosphorylation rates.

Characterization and localization of endothelin receptor subtypes in the human atrioventricular conducting system and myocardium

The characterization and localization of endothelin A (ETA) and endothelin B (ETB) receptors have been determined in tissue sections of the human atrioventricular conducting system, surrounding regions of atrial and ventricular myocardium, and the left ventricular free wall by use of radioligand binding, polymerase chain reaction, and in situ hybridization. Selective ETA (BQ123) and ETB (BQ3020) compounds in conjunction with [125I]endothelin-1 revealed the presence of ETA and ETB receptors in the left ventricular free wall (BQ123: 57 +/- 5% ETA, 43 +/- 2% ETB, n = 3; BQ3020: 67 +/- 3% ETA, 33 +/- 3% ETB, n = 3). Autoradiography using [125I]endothelin-1 in the absence or presence of BQ3020, BQ123, or endothelin-1 showed ETA and ETB receptors localized to atrial and ventricular myocardium, the atrioventricular conducting system, and endocardial cells. There was a higher proportion of ETB receptors in the atrioventricular node and the penetrating and branching bundles of His than in the surrounding interventricular and interatrial septa (p < 0.0001). There was a lower density of ETB receptors in the interventricular septum compared with the interatrial septum and the atrioventricular conducting system (p = 0.009) and a lower density of ETA receptors in the atrioventricular conducting system compared with interatrial and interventricular septa (p = 0.008). Isolated right atrial myocytes showed a higher proportion of ETA receptors (91 +/- 12%, n = 3). Amplification of left ventricular free wall cDNA by polymerase chain reaction revealed the presence of ETA and ETB receptor mRNA. mRNA for both subtypes was detected in isolated atrial myocytes. In situ hybridization showed ETA and ETB receptor mRNA localization to atrial and ventricular myocardium, the atrioventricular conducting system, and endocardial cells. These studies demonstrate the presence of ETA and ETB receptors in human myocardium and the atrioventricular conducting system.

Early heart development: dynamics of endocardial cell sorting suggests a common origin with cardiomyocytes

The myocardial and endocardial cell sorting out processes take place primarily between 19 and 29 hr of development in the avian embryo. This occurs in an apparent rostral to caudal wave through the heart forming region. During heart development considerable uncertainty exists regarding the processes that regulate cell commitments, progressive aggregation, and sorting out of the different precardiac cell populations. The question addressed in this report is whether endocardial and myocardial cells have a common origin or do the endocardial cells arise from a distinct population of cells from within the precardiac mesoderm. These cells then migrate to become localized between the developing myocardium above and the endoderm below. The distribution of preendocardial cells and premyocardial cells has been followed immunohistochemically in quail heart-forming region mesoderm explants from embryos approximately 18 hr in development and incubated for a 24-hr period. Differentiating myocardiocytes were immunostained with anti-N-cadherin and endocardiocytes with QH-1, a monoclonal antibody that recognizes an antigenic determinant on quail endothelial cells. Sparsely localized QH-1 labeled endothelial cells are localized in the stage 5 heart-forming region. These cells are often arranged in a columnar fashion in the mesoderm explants 6 hr after explantation. By 15-22 hr large patches of QH-1 expressing cells are interspersed with the N-cadherin expressing myocardiocytes. A subpopulation of cells express both N-cadherin and QH-1 antigen suggesting that endocardial and myocardial cells may arise from a common precursor population and that N-cadherin regulation may be a mechanism underlying specific cell sorting of these two cell populations during heart development.

Ventricular expression of atrial and brain natriuretic peptides in dilated cardiomyopathy. An immunohistocytochemical study of the endomyocardial biopsy specimens using specific monoclonal antibodies

Although brain natriuretic peptide is expressed in ventricles of failing hearts including dilated cardiomyopathy, its morphological localization is still unclear. In this study, we analyzed the immunohistocytochemical localization of atrial and brain natriuretic peptides in ventricles of dilated cardiomyopathy at both light and electron microscopic levels. Ventricular specimens were obtained by endomyocardial biopsy in 31 patients (26 with dilated cardiomyopathy and 5 controls without any specific cardiac disease). By light microscopic immunohistochemistry using specific monoclonal antibodies, all (26 of 26) of the left ventricular endomyocardial biopsy specimens and 31% (8 of 26) of the right ventricular specimens showed immunoreactivity for both of these natriuretic peptides in dilated cardiomyopathy. In contrast, none of the normal controls showed immunoreactivity for either of these peptides. The percentage of atrial natriuretic peptide-containing or brain natriuretic peptide-containing myocytes in the left ventricular specimens showed an inverse correlation with the left ventricular ejection fraction (r = -0.72 and r = -0.69, respectively). By electron microscopy, we identified specific secretory granules in ventricular myocytes from patients with dilated cardiomyopathy, but not in those from normal controls. Double immunocytochemistry using a two-face immunogold staining method revealed brain natriuretic peptide colocalized with atrial natriuretic peptide in the same ventricular granules. These findings suggest that brain natriuretic peptide is expressed in ventricular myocytes in response to hemodynamic stress in dilated cardiomyopathy. Brain natriuretic peptide may be, at least in part, synthesized simultaneously and secreted together with atrial natriuretic peptide by granules from failing ventricles, although the secretory turnover is different between these two peptides.

Expression of collagenase and IL-1 alpha in developing rat hearts

During development, extracellular matrix (ECM) molecules are thought to play a major role in regulating the formation of the heart. The change in the heart from a simple tube to a complex, four-chambered organ requires the modification of both the cellular components as well as the surrounding ECM. Matrix metalloproteinases (MMP), which include collagenases, are enzymes present in the ECM that have the potential to modify the existing ECM during the development of the heart. Using both monoclonal and polyclonal antisera against collagenase, specific temporal and spatial patterns have been documented during critical periods of heart development. The cytokine interleukin 1 alpha (IL-1 alpha), a potent inducer of the MMP expression, was also shown to have a similar staining pattern in the developing heart. The monoclonal anti-rat collagenase (Mab) intensely stained the surfaces of the myocytes in the trabeculae and the ventricular and atrial walls of the 11.5 or 12.5 embryonic day (ED) rat hearts. In contrast, the polyclonal anti-human collagenase (Pab) stained not only the cardiomyocytes but also the hypertrophic endocardial cells. Pab appeared to stain the leading edge of the mesenchymal cells that migrate into the cardiac jelly of the 11.5 or 12.5 ED hearts. Immunohistochemical staining showed IL-1 alpha on the endocardial endothelium and the surface of cardiomyocytes near the cardiac jelly just before or coincident with the appearance of migrating cells. IL-1 alpha was detected on the endocardial endothelium, cardiomyocytes in the trabeculae, and the ventricular and atrial walls, as well as in the myocardial basement membrane of the truncal or atrioventricular region. However, no staining could be detected on the migrating cells in the cardiac cushions. These results indicate the presence of collagenase and IL-1 alpha on the surface of cardiomyocytes and mesenchymal cells at times when the heart is undergoing acute remodeling during septation and trabeculation. These data suggest a role for collagenase/cytokine interaction in tissue remodeling during critical stages of cardiac embryogenesis where modification of the ECM is essential to cardiac morphogenesis.

Expression of cell adhesion molecules in human cardiac allograft rejection

Adhesion of leukocytes to vascular endothelial cells is a critical step in a variety of inflammatory conditions. We studied the expression and distribution of intercellular adhesion molecule-1 (ICAM-1) and endothelial leukocyte adhesion molecule-1 (ELAM-1) in frozen sections of 83 endomyocardial biopsy specimens from human allograft hearts using monoclonal antibodies and an avidin-biotin complex-alkaline phosphatase staining technique. Cases with cellular or humoral rejection and Quilty lesions were studied. Staining was graded from 0 to 3+ in lymphocytes and in capillary, arterial, venular, and endocardial endothelial cells. Expression of ICAM-1 in capillaries increased with the severity of cellular rejection and was prominent in humoral rejection. ICAM-1 was also expressed in lymphocytes in proportion to the degree of rejection. Little or no ELAM-1 expression was noted. In Quilty lesions the intensity of ICAM-1 expression was similar to that of mild-to-moderate rejection. Thus adhesion molecule expression can be identified in endomyocardial biopsy specimens of patients with rejection, suggesting a role for adhesion molecules in the process of rejection. These findings may prove useful in monitoring rejection and its response to therapy and in developing specific antisera directed against these molecules.

Fibulin is localized at sites of epithelial-mesenchymal transitions in the early avian embryo

Fibulin is a 100-kDa calcium-binding, extracellular matrix (ECM), and plasma glycoprotein (Argraves et al., Cell 58, pp. 623-629, 1989; Argraves et al., J. Cell Biol. 111, 3155-3164). Immunoprecipitation analysis showed that antibodies against human fibulin react with an avian isoform (M(r) 100,000). The spatial and temporal distribution of fibulin was examined in the early avian embryo using immunofluorescence microscopy. In stage 15-22 quail embryos fibulin is a constituent of most basement membranes. Areas undergoing epithelial-mesenchymal transitions such as the endocardial cushions, developing myotomes, and neural crest display especially prominent immunostaining. In the early heart fibulin expression was most pronounced in the cardiac jelly at sites where endocardial cushion cells begin the migrations that lead to the formation of valvular and septal primordia. Laser scanning confocal microscopy showed extensive extracellular accumulations of fibulin on the surface of endocardial mesenchyme cells that were motile at the time of fixation (stage 19). These data suggest that enhanced deposition of fibulin at sites of epithelial-mesenchymal transitions may influence cell behavior.

The effect of orthotopic transplantation on total, beta 1- and beta 2-adrenoceptors in the human heart

1. [125I]-(-)pindolol binding was used to determine beta-adrenoceptor density in homogenate preparations of right ventricular endomyocardial biopsies from 43 non-rejecting patients over the first 13 months following cardiac transplantation. The selective beta 1 subtype antagonist ligand CGP 20712A was used to determine the subtype density in 32 of the patients. Biopsy specimens from 15 donor hearts were used as controls. 2. beta-adrenoceptor density (expressed in terms of fmol mg-1 protein) was increased in the group of transplanted hearts as a whole compared with the donor hearts with respect to total (35 +/- 2 vs 23 +/- 2) and the beta 1 subtype (25 +/- 2 vs 16 +/- 2) whereas the beta 2 subtype and radioligand dissociation constant did not differ. 3. Non-parametric analysis of variance of total receptor density over time revealed significant heterogeneity which appears to be due to a discrete increase in beta-adrenoceptor density during the 4th post operative month. 4. These results indicate that beta-adrenoceptor density is not constant following transplantation. Furthermore, the increase in receptor density following transplantation is due mainly to an increase in the beta 1 subtype without a significant change in the beta 2 subtype.

Endocardial localization and characterization of natriuretic peptide binding sites in human fetal and adult heart

Specific, high affinity binding sites for 125I-human-alpha-atrial natriuretic peptide-(1-28)) (125I-hANP-(1-28)) were identified in human fetal and adult heart and the binding characterized using quantitative in vitro autoradiography. Binding sites were localized to atrial and ventricular endocardium, aorta, pulmonary arteries and epicardial mesothelium. Kinetic studies indicated a Kd value of 32 pM for ventricular endocardial 125I-hANP-(1-28) binding. The binding was completely inhibited by an excess (1 microM) of unlabelled hANP-(1-28), human brain natriuretic peptide-(1-32) (hBNP-(1-32)) and by the 'clearance receptor' specific ring-deleted analogue, C-ANP-(4-23). Competitive inhibition studies indicated a relative inhibitory potency for hBNP-(1-32) and C-ANP-(4-23) of 6% and 3% respectively. The data suggest that a distinct natriuretic peptide receptor subtype is expressed in the endocardium and in addition to a possible clearance function, may represent a site for feedback regulation and peptide interaction.

Myocardial fibrosis in aging germ-free and conventional Lobund-Wistar rats: the protective effect of diet restriction

The influences of diet restriction and germ-free environment on aging were studied in 127 male Lobund-Wistar rats ranging in age from 7 to 48 months. There was an age-related increase in collagen deposition of the heart, particularly involving the left ventricle. The degree of fibrosis was significantly less extensive in middle and old age rats (18 mo, 30 mo, 32+ mo) maintained on a restricted diet. No clear-cut influence of germ-free environment was apparent. No amyloid was detected in 175 tissue sections examined from hearts, lungs, and livers.

Myocardial catecholamine concentrations in dilated cardiomyopathy and heart failure of different origins

Myocardial catecholamine concentrations were determined in endomyocardial biopsies from patients with heart failure to assess if tissue catecholamine levels relate to the severity of myocardial damage or the aetiology of the underlying disease. Methodological studies revealed a good reproducibility of catecholamine determinations in biopsies; the variance between paired biopsies was below 17% when myocardial catecholamines were related to non-collagen protein (NCP). Myocardial norepinephrine (in pg micrograms-1 NCP) levels were comparable in patients with dilated cardiomyopathy (DCM, 5.3 +/- 3.4, n = 22) and in patients with coronary or valvular heart disease (5.6 +/- 4.7, n = 14). In both groups, a significant reduction of myocardial norepinephrine was found (controls 12.0 +/- 3.4, P less than 0.0006). In a subgroup of patients with heart failure and a LVEF less than 30% (3.9 +/- 3.5, n = 17) myocardial norepinephrine content was lower than in patients with heart failure and LVEF of 31-55% (6.6 +/- 3.4, n = 19) (both P less than 0.05 against controls: 12.0 +/- 3.4, n = 16). A correlation between myocardial norepinephrine and LVEF was found in DCM (P less than 0.001, r = 0.70). The loss of myocardial norepinephrine is a characteristic feature of heart failure. It is independent of the origin of failure, but correlates with the impairment of LV function.

Expression of atrial natriuretic factor in the human ventricle is independent of chamber dilation

This study investigated the presence of atrial natriuretic factor in ventricular tissue obtained from humans with dilated or restrictive heart disease. In 17 patients with ventricular dilation and impaired systolic function and in 8 patients with restrictive heart disease and preserved systolic function, the presence of ventricular atrial natriuretic factor was investigated in tissue obtained by ventricular endomyocardial biopsy. The objective of the study was to determine if the ventricular presence of atrial natriuretic factor is dependent on ventricular dilation. Left ventricular end-diastolic volume index was greater in the group with dilated cardiomyopathy than in the group with restrictive cardiomyopathy (134 +/- 13 versus 78 +/- 5 ml/m2, p less than 0.05); end-diastolic pressure was elevated in the two groups (20 +/- 2 versus 25 +/- 4 mm Hg, p = NS). With the use of immunohistochemical techniques, ventricular atrial natriuretic factor was clearly detected in 15 of the 17 patients with dilated cardiomyopathy and in 6 of the 8 patients with restrictive cardiomyopathy. This study demonstrates the high prevalence of ventricular atrial natriuretic factor in living patients with either systolic or diastolic dysfunction. Whereas in the atria, stretch or dilation may be an important stimulus, atrial natriuretic factor in the ventricular chamber occurs independent of dilation.