Rheumatic Aschoff nodules revisited: an immunohistological reappraisal of the cellular component

Impact of Rheumatic Process in Left and Right Ventricular Function in Patients with Mitral Regurgitation

Background

Mitral regurgitation (MR) burdens the left and right ventricles with a volume or pressure overload that leads to a series of compensatory adaptations that eventually lead to ventricular dysfunction, and it is well known that in rheumatic heart disease (RHD) that the inflammatory process not only occurs in the valve but also involves the myocardial and pericardial layers. However, whether the inflammatory process in rheumatic MR is associated with ventricular function besides hemodynamic changes is not yet established.

Purpose

Evaluate whether rheumatic etiology is associated with ventricular dysfunction in patients with chronic MR.

Methods

The study population comprised patients aged 18 years or older included in the registry who had echocardiography performed at the National Cardiovascular Center Harapan Kita in Indonesia during the study period with isolated primary MR due to rheumatic etiology and degenerative process with at least moderate regurgitation.

Results

The current study included 1,130 patients with significant isolated degenerative MR and 276 patients with rheumatic MR. Patients with rheumatic MR were younger and had a higher prevalence of atrial fibrillation and pulmonary hypertension, worse left ventricle (LV) ejection fraction and tricuspid annular plane systolic excursion (TAPSE) value, and larger left atrium (LA) dimension compared to patients with degenerative mitral regurgitation (MR). Gender, age, LV end-systolic diameter, rheumatic etiology, and TAPSE were independently associated with more impaired LV ejection fraction. Whereas low LV ejection fraction, LV end-systolic diameter, and tricuspid peak velocity (TR) peak velocity >3.4 m/s were independently associated with more reduced right ventricle (RV) systolic function (Table 3).

Conclusions

Rheumatic etiology was independently associated with more impaired left ventricular function; however, rheumatic etiology was not associated with reduced right ventricular systolic function in a patient with significant chronic MR.

Characteristics of patients with rheumatic heart disease in a national referral hospital in Indonesia

BACKGROUND Rheumatic heart disease (RHD) is one of the most common cardiovascular problems in Indonesia. Comprehensive data regarding patient characteristics are critical in planning optimal treatment strategies to relieve the burden of RHD. This study aimed to describe the clinical and echocardiographic characteristics of patients across several types of valvular lesions in RHD in the Indonesian population. METHODS This retrospective study was performed between January 2016 and June 2019 at the National Cardiovascular Center Harapan Kita, Jakarta, Indonesia. The study population comprised all patients with significant valve disease aged ≥18 years. Patient characteristics and echocardiographic parameters were collected retrospectively from medical records and hospital information systems. Patients were classified into several groups based on etiologies of valve disease. RESULTS Of 5,482 patients with significant valve lesions, 2,333 (42.6%) were RHD patients. They were predominantly female (64.1%) and younger (mean [standard deviation] age 42.61 [12.01] years). Atrial fibrillation (AF) was the most frequent rhythm disorder observed in RHD (65.4%). Isolated mitral stenosis was the most common valve lesion in RHD patients (46.5%). Most patients with RHD had preserved left ventricular (LV) ejection fraction. Half of the patients with mitral stenosis had reduced right ventricular (RV) contractility (tricuspid annular plane systolic excursion <17 mm). CONCLUSIONS Isolated mitral stenosis was the most observed condition of valve lesions in RHD. Characteristics of RHD patients in this study were predominantly female, younger age, had preserved LV function, reduced RV function, and high prevalence of AF.

Group G Streptococcus Induces an Autoimmune Carditis Mediated by Interleukin 17A and Interferon γ in the Lewis Rat Model of Rheumatic Heart Disease

Acute rheumatic fever and rheumatic heart disease (ARF/RHD) have long been described as autoimmune sequelae of Streptococcus pyogenes or group A streptococcal (GAS) infection. Both antibody and T-cell responses against immunodominant GAS virulence factors, including M protein, cross-react with host tissue proteins, triggering an inflammatory response leading to permanent heart damage. However, in some ARF/RHD-endemic regions, throat carriage of GAS is low. Because Streptococcus dysgalactiae subspecies equisimilis organisms, also known as β-hemolytic group C streptococci and group G streptococci (GGS), also express M protein, we postulated that streptococci other than GAS may have the potential to initiate or exacerbate ARF/RHD. Using a model initially developed to investigate the uniquely human disease of ARF/RHD, we have discovered that GGS causes interleukin 17A/interferon γ-induced myocarditis and valvulitis, hallmarks of ARF/RHD. Remarkably the histological, immunological, and functional changes in the hearts of rats exposed to GGS are identical to those exposed to GAS. Furthermore, antibody cross-reactivity to cardiac myosin was comparable in both GGS- and GAS-exposed animals, providing additional evidence that GGS can induce and/or exacerbate ARF/RHD.

Group A streptococcal M-protein specific antibodies and T-cells drive the pathology observed in the rat autoimmune valvulitis model

Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are autoimmune mediated diseases triggered by group A streptococcal (GAS) infections. Molecular mimicry between GAS M-proteins and host tissue proteins has been proposed as the mechanism that initiates autoreactive immune responses in ARF/RHD. However, the individual role of antibodies and T-cells specific for GAS M-proteins in the pathogenesis of autoimmune carditis remains under-explored. The current study investigated the role of antibodies and T-cells in the development of carditis in the Lewis rat autoimmune valvultis (RAV) model by transferring serum and/or splenic T-cells from rats previously injected with GAS recombinant M5 protein. Here we report that serum antibodies alone and serum plus in vitro expanded rM5-specific T-cells from hyperimmune rats were capable of transferring carditis to naïve syngeneic animals. Moreover, the rats that received combined serum and T-cells developed more severe carditis. Recipient rats developed mitral valvulitis and myocarditis and showed prolongation of P-R intervals in electrocardiography. GAS M5 protein-specific IgG reactivity and T-cell recall response were also demonstrated in recipient rats indicating long-term persistence of antibodies and T-cells following transfer. The results suggest that both anti-GAS M5 antibodies and T-cells have differential propensity to induce autoimmune mediated carditis in syngeneic rats following transfer. The results highlight that antibodies and effector T-cells generated by GAS M protein injection can also independently home into cardiac tissue to cross-react with tissue proteins causing autoimmune mediated immunopathology.

Cardiac phenotype in mouse models of systemic autoimmunity

Patients suffering from systemic autoimmune diseases are at significant risk of cardiovascular complications. This can be due to systemically increased levels of inflammation leading to accelerated atherosclerosis, or due to direct damage to the tissues and cells of the heart. Cardiac complications include an increased risk of myocardial infarction, myocarditis and dilated cardiomyopathy, valve disease, endothelial dysfunction, excessive fibrosis, and bona fide autoimmune-mediated tissue damage by autoantibodies or auto-reactive cells. There is, however, still a considerable need to better understand how to diagnose and treat cardiac complications in autoimmune patients. A range of inducible and spontaneous mouse models of systemic autoimmune diseases is available for mechanistic and therapeutic studies. For this Review, we systematically collated information on the cardiac phenotype in the most common inducible, spontaneous and engineered mouse models of systemic lupus erythematosus, rheumatoid arthritis and systemic sclerosis. We also highlight selected lesser-known models of interest to provide researchers with a decision framework to choose the most suitable model for their study of heart involvement in systemic autoimmunity.

Spontaneously occurring intramural coronary arteriosclerosis in regularly slaughtered veal calves and beef cattle: a screening study about prevalence and histopathological features

OBJECTIVES

Intramural coronary arteriosclerosis has been reported in several species, but no systematic studies are currently available in bovine. The present study aimed to describe the arteriosclerotic changes in regularly slaughtered veal calves and beef cattle.

ANIMALS

Twenty-five veal calves (6-9 months old) and 17 beef cattle (10-24 months old) housed in intensive livestock farming and regularly slaughtered were included in the present study.

METHODS

Selected heart samples were submitted for histopathological and ultrastructural examination and the following parameters were evaluated: intimal hyperplasia, degenerative changes of the tunica media, medial hypertrophy/hyperplasia, myocardial fibrosis, and myocarditis. Pathological intramural coronary arteries with and without lumen narrowing were manually counted in every sample.

RESULTS

Intramural coronary arteriosclerosis was observed in all the calves and cattle, with similar prevalence of fibromuscular/muscular intimal hyperplasia (92% vs 88%), degenerative changes of the tunica media (76% vs 71%), and medial hypertrophy/hyperplasia (44% vs 59%). The posterior papillary muscle of the left ventricle was the myocardial localization significantly more affected in both calves (p = 0.0007) and cattle (p = 0.0339). Anitschkow cells were detected in the coronary walls of both calves (60%) and cattle (76%).

CONCLUSIONS

This is the first study that systematically describes spontaneously occurring intramural coronary arteriosclerosis in bovine species. Anitschkow cells, whose ultrastructural characteristics and localization suggest their potential origin from the smooth muscle cells of the tunica media of the arteriosclerotic coronary vessels, were also identified.

Group A Streptococcus, Acute Rheumatic Fever and Rheumatic Heart Disease: Epidemiology and Clinical Considerations

OPINION STATEMENT

Early recognition of group A streptococcal pharyngitis and appropriate management with benzathine penicillin using local clinical prediction rules together with validated rapi-strep testing when available should be incorporated in primary health care. A directed approach to the differential diagnosis of acute rheumatic fever now includes the concept of low-risk versus medium-to-high risk populations. Initiation of secondary prophylaxis and the establishment of early medium to long-term care plans is a key aspect of the management of ARF. It is a requirement to identify high-risk individuals with RHD such as those with heart failure, pregnant women, and those with severe disease and multiple valve involvement. As penicillin is the mainstay of primary and secondary prevention, further research into penicillin supply chains, alternate preparations and modes of delivery is required.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.

The same systemic autoimmune disease provokes arthritis and endocarditis via distinct mechanisms

The immune mechanisms that provoke concomitant inflammation of synovial joints and cardiac valves in disorders such as rheumatic fever and systemic lupus erythematosus remain poorly defined. Here, we report the discovery of spontaneous endocarditis-in addition to their well-studied autoimmune arthritis-in K/BxN T cell receptor (TCR) transgenic mice. The same adaptive immune system elements were required for initiation of arthritis and endocarditis, and both diseases were dependent on autoantibodies. In contrast, the participation of key innate immune system molecules and perhaps T cells as effectors of inflammation differed between the 2 target tissues. Arthritis in K/BxN TCR transgenic mice depended primarily on complement C5 and not FcRgamma-using receptors; conversely, endocarditis depended essentially on FcRgamma receptors and not C5. Elucidating how a single systemic autoimmune disease engages distinct immune effector pathways to damage different target tissues is essential for optimizing the treatment of such disorders.

Role of NADPH oxidase in formation and function of multinucleated giant cells

Macrophages play essential roles in a wide variety of physiological and pathological processes. One of the unique features of these phagocytic leukocytes is their ability to fuse, forming multinucleated giant cells. Multinucleated giant cells are important mediators of tissue remodeling and repair and are also responsible for removal or sequestration of foreign material, intracellular bacteria and non-phagocytosable pathogens, such as parasites and fungi. Depending on the tissue where fusion occurs and the inflammatory insult, multinucleated giant cells assume distinctly different phenotypes. Nevertheless, the ultimate outcome is the formation of large cells that can resorb bone tissue (osteoclasts) or foreign material and pathogens (giant cells) extracellularly. While progress has been made in recent years, the mechanisms and factors involved in macrophage fusion are still not fully understood. In addition to cytokines and a number of adhesion proteins and receptors, it is becoming increasingly clear that NADPH oxidase-generated reactive oxygen species (ROS) also play an important role in macrophage fusion. In this review, we provide an overview of macrophage multinucleation, with a specific focus on the role of NADPH oxidases and ROS in macrophage fusion and in the function of multinucleated giant cells. In addition, we provide an updated overview of the role of these cells in inflammation and various autoimmune diseases.

B- and T-cell responses in group a streptococcus M-protein- or Peptide-induced experimental carditis

The etiology of rheumatic fever and rheumatic heart disease (RF/RHD) is believed to be autoimmune, involving immune responses initiated between streptococcal and host tissue proteins through a molecular mimicry mechanism(s). We sought to investigate the humoral and cellular responses elicited in a Lewis rat model of group A streptococcus M-protein- or peptide-induced experimental valvulitis/carditis, a recently developed animal model which may, in part, represent human rheumatic carditis. Recombinant streptococcal M5 protein elicited opsonic antibodies in Lewis rats, and anti-M5 antisera recognized epitopes within the B- and C-repeat regions of M5. One peptide from the streptococcal M5 protein B-repeat region (M5-B.6, amino acids 161 to 180) induced lymphocytes that responded to both recombinant M5 and cardiac myosin. Rats immunized with streptococcal M5 protein developed valvular lesions, distinguished by infiltration of CD3(+), CD4(+), and CD68(+) cells into valve tissue, consistent with human studies that suggest that RF/RHD are mediated by inflammatory CD4(+) T cells and CD68(+) macrophages. The current study provides additional information that supports the use of the rat autoimmune valvulitis model for investigating RF/RHD.

Transgenic overexpression of platelet-derived growth factor-C in the mouse heart induces cardiac fibrosis, hypertrophy, and dilated cardiomyopathy

The platelet-derived growth factors are implicated in development of fibrotic reactions and disease in several organs. We have overexpressed platelet-derived growth factor-C in the heart using the alpha-myosin heavy chain promoter and created a transgenic mouse that exhibits cardiac fibrosis followed by hypertrophy with sex-dependent phenotypes. The transgenic mice developed several pathological changes including cardiac fibroblast proliferation and deposition of collagen, hypertrophy, vascular defects, and the presence of Anitschkow cells in the adult myocardium. Male mice developed a hypertrophic phenotype, whereas female mice were more severely affected and developed dilated cardiomyopathy, leading to heart failure and sudden death. The vascular defects initially included dilation of microvessels and vascular leakage. Subsequently, a marked loss of microvessels, formation of large vascular sac-like structures, and an increased density of smooth muscle-coated vessels were observed in the myocardium. In part, the observed vascular changes may be because of an up-regulation of vascular endothelial growth factor in cardiac fibroblasts of the transgenic hearts. This unique animal model reveals that a potent mitogen for cardiac fibroblasts result in an expansion of the interstitium that induce a secondary sex-dependent hypertrophic response in the cardiomyocytes.

Anitschkow myocytes or cardiac histiocytes in human hearts

The caterpillar chromatin pattern of the nucleus in longitudinal section and owl-eye appearance in transverse section characterize the Anitschkow cell of Aschoff bodies in rheumatic heart disease. Determining whether it is of muscle origin or cardiac histiocyte has been a source of controversy for many years. In a study of fetal and neonatal hearts from humans, vesicular nuclei often displaying the Anitschkow chromatin pattern were the predominant cell type in the myocardium. Because a similar pattern was also observed in two cell types related to laryngeal cartilage and the neighbouring fibrous tissue in a six week old neonate, it was concluded that the Anitschkow chromatin pattern probably indicates cellular immaturity rather than any specific cell type.

Pathology of mitral valve in regularly slaughtered pigs: an abattoir survey on the occurrence of myxoid degeneration (endocardiosis), fibrosis and valvulitis

The aim of this study was to report the prevalence of degenerative and early inflammatory lesions and to discuss some histological aspects of normal and pathological mitral valve leaflets in healthy, normally slaughtered pigs. Mitral valves were collected from 112, 6 month-old, pigs reared under different conditions. Histological examination revealed the presence of myxoid degeneration in 29.5% of the valves with no significantly different prevalence according to rearing conditions; fibrosis was present in 12.5%; inflammation (non-vegetative valvulitis) occurred in 20 (17.9%) macroscopically normal valves. No vegetative endocarditis could be observed. A significantly higher degree of inflammation was observed in valves affected by myxoid degeneration (P < 0.05) and Anitschkow cells were prevalent in all the pathological valves (P < 0.01). Capillaries were observed in a wide majority of the valves (86.5%), but small arterioles were related to fibrotic thickening of the leaflets (P < 0.01). The following conclusions are discussed: (1) environmental factors seem not to influence the prevalence of endocardiosis; (2) inflammatory foci in myxoid valves are a reaction to both abnormal friction and products of degraded collagen and extracellular matrix; (3) the authors consider the presence of capillaries in pig valves a normal finding whereas proliferation of the vessels occurs under pathological conditions; (4) non vegetative valvulitis can be related to the presence of vessels in the valve and may have a role in both infectious endocarditis and fibrosis; (5) Anitschkow cells are normally observed in pig valves and are not specifically related to pathological lesions.