A rat model of hypereosinophilic syndrome

In-Depth Review of Loeffler Endocarditis: What Have We Learned?

Loeffler endocarditis, eosinophilic endocarditis or eosinophilic endomyocardial disease are conditions associated with hypereosinophilia and they affect the heart function. Loeffler endocarditis is a rare endomyocardial disorder thought to be caused by eosinophilic damage. The disorder is characterized by inflammatory infiltration, formation of thrombus within cardiovascular system, and ultimately fibrosis of the afflicted area. It can lead to multiple severe complications, including thromboembolic disease, thickening of fibrous tissue in the endocardium of ventricles, valve involvement, apical obliteration, and various heart disorders. Although early clinical intervention can lead to remission, the underlying mechanisms of the disorder remain unresolved. In the present article, we summarise the existing literature concerning Loeffler endocarditis based on PubMed, Web of Science, and other medical databases to conduct an in-depth review of the epidemiology, etiology, pathophysiological mechanisms, staging, diagnosis, treatment and prognosis of Loeffler endocarditis. Meanwhile, we provide novel patients data and clinical figures of Loeffler endocarditis to supplement the understanding of this cardiac disorder. The findings presented in this article provide a basis for further studies and can be used to improve management of the disorder.

Eosinophilic aortitis with thoracic aortic aneurysm and rupture in a captive-born owl monkey

Eosinophilic aortitis is a rare condition in animals and humans, and it has been occasionally reported associated with parasitic migration and with a poorly understood complex group of autoimmune vasculitides. Here, we describe a case of eosinophilic aortitis with thoracic aortic aneurysm and rupture in a captive-born owl monkey and discuss the differential diagnoses.

The spectrum of eosinophilic infiltration of the cecum and its relationship to other disorders of multiple granulomas and arteritis in Sprague-Dawley rat

Spontaneous multiple granulomas were present in the animal under the SPF condition and without chemical treatment, in a 19-week-old male Sprague-Dawley control-group rat. Here we describe multiple granulomas and prominent diffuse infiltration by eosinophils in the cecal submucosa, and arteritis in the mesenteric arteries. The multiple granulomas were characterized by central eosinophilic degeneration or necrosis, prominent eosinophils, many multi-nucleated giant cells and abundant fibroblasts. They were restricted to the cecal submucosa. The mesenteric arteritis consisted of fibrinoid necrosis of the intima and media, intense inflammatory cell infiltration and fibrosis in the arterial wall. An affected artery in the cecum was continuous with the mesenteric artery. The foregoing tissue changes in this rat correlate with the high absolute blood eosinophil count found in this animal.

An interleukin-33 gene polymorphism is a modifier for eosinophilia in rats

In previous studies, we identified a loss-of-function mutation in the Cyba gene as the primary cause of hereditary eosinophilia in the Matsumoto Eosinophilia Shinshu (MES) rat strain. We also identified a modifier locus for eosinophilia named eos3 in rats. In this study, we examined the interleukin-33 (Il33) gene as a candidate for the eos3 and found a missense nucleotide substitution in the gene, which resulted in a G171S amino-acid substitution in the IL-33 protein. Recombinant IL-33 isoform with the G171S substitution had approximately 50% of activity of normal isoform in NF-κB-dependent reporter assay, and reduced bioactivity (∼65% of normal) to provoke eosinophilia when injected into mice. In a genetic association study using (ACI × MES) × MES backcross rats, we found that the effects of polymorphic Il33 alleles on blood eosinophil level were manifested only in rats with loss of Cyba function. In these rats, the blood eosinophil level was significantly lower (∼50%) in heterozygotes for the ACI allele of Il33 compared with homozygotes for the MES allele. Oddly, however, eosinophilic MES rats had blood IL-33 content below the detectable limits. These results suggest that the Il33 gene polymorphism could be a modifier of eosinophilia in rats.

Inflammatory Fibroid Polyp in the Duodenum of a Common Marmoset (Callithrix jacchus)

A 32-month-old male common marmoset had a firm and white-colored mass in the duodenal wall. The cut surface was smooth and grayish white in color. Histologically, the mass consisted of a proliferation of spindle cells with an oval to spindle-shaped nucleus and scant eosinophilic cytoplasm in a loose myxoid or fibrotic background. Most of the lesion displayed no specific growth pattern whereas some of the cells concentrated around the vessels and created an onion-bulb structure. Additionally, marked inflammatory cellular infiltration, mainly eosinophils, was observed throughout the lesion. Immunohistochemically, the spindle cells were positive for vimentin, α-smooth muscle actin, fascin, and cyclin D1, and negative for S-100, factor VIII–related antigen, and c-kit. These histological and immunohistochemical features did not meet any differential diagnoses such as gastrointestinal stromal tumor, inflammatory myofibroblastic tumor, solitary fibrous tumor/hemangiopericytoma, smooth muscle tumor, schwannoma, and hemangiosarcoma. Collectively, the authors diagnosed the mass as a lesion that corresponded to an inflammatory fibroid polyp (IFP) in humans. IFP is defined as a mesenchymal proliferation composed of spindle stromal cells, small blood vessels, and inflammatory cells, particularly eosinophils, and is currently classified as a nonneoplastic lesion. To the best of our knowledge, this is the first case of spontaneous IFP in nonhuman primates.

BN.MES-Cyba(mes) congenic rats manifest focal necrosis with eosinophilic infiltration in the liver without blood eosinophilia

The Matsumoto Eosinophilia Shinshu (MES) rat strain develops hereditary blood eosinophilia and eosinophil-related inflammatory lesions in organs due to the mutant Cyba(mes) gene. We hypothesized that a new eosinophilia model with a different phenotype could be established by changing the genetic background of rats. We bred and characterized a congenic strain, in which the mutant Cyba(mes) gene was introduced into the background of a BN strain (BN.MES-Cyba(mes)). The congenic rats showed robust proliferation of eosinophils in the bone marrow. Nonetheless, blood eosinophil levels of the rats remained within the normal range. In addition, the rats manifested focal necrosis with eosinophilic infiltration in the liver, a phenotype rarely observed in the original MES rat strain. These results imply the presence of genetic polymorphisms between MES and BN strains which modulate the mobilization of eosinophils to the peripheral circulation and organs. The newly established BN.MES-Cyba(mes) congenic rat strain, together with the original MES strain, will provide useful models for elucidating the molecular genetic mechanisms involved in the development and trafficking of eosinophils.

Pivotal Advance: Eosinophilia in the MES rat strain is caused by a loss-of-function mutation in the gene for cytochrome b(-245), alpha polypeptide (Cyba)

MES is a rat strain that spontaneously develops severe blood eosinophilia as a hereditary trait. Herein, we report that eosinophilia in MES rats is caused by a loss-of-function mutation in the gene for cytochrome b(-245), alpha polypeptide (Cyba; also known as p22(phox)), which is an essential component of the superoxide-generating NADPH oxidase complex. The MES rat has a deletion of four nucleotides, including the 5' splice donor GpT of intron 4 of the Cyba gene. As a consequence of the deletion, a 51-nucleotide sequence of intron 4 is incorporated into the Cyba transcripts. Leukocytes from the MES strain lack both CYBA protein and NADPH oxidase activity. Nevertheless, unlike patients with chronic granulomatous disease, who suffer from infections with pathogens due to similar genetic defects in NADPH oxidase, MES rats retain normal innate immune defense against Staphylococcus aureus infection. This is due to large quantities of peritoneal eosinophils in MES rats, which phagocytose and kill the bacteria. MES rat has a balance defect due to impaired formation of otoconia in the utricles and saccules. Eosinophilia of the MES rat was normalized by introduction of a normal Cyba transgene. The mechanisms by which impairment of NADPH oxidase leads to eosinophilia in the MES rat are elusive. However, our study highlights the essential role of NADPH oxidase in homeostatic regulation of innate immunity beyond conventional microbicidial functions.

Inflammatory fibroid polyps harbour mutations in the platelet-derived growth factor receptor alpha (PDGFRA) gene

Inflammatory fibroid polyps (IFPs) are mesenchymal tumours which arise in the submucosa and mucosa of the gastrointestinal tract. To date, the pathogenesis is unknown and IFPs are considered reactive and non-neoplastic lesions. Investigating a series of 23 IFPs, we made the observation that the tumours consistently express PDGFRA. To further elucidate the pathogenetic role of PDGFRA, we performed mutational analyses of exons 10, 12, 14, and 18. As IFPs are characterized by an inflammatory infiltrate rich in eosinophils, we used fluorescence in situ hybridization in a subset of tumours to investigate a possible FIP1L1-PDGFRA translocation which is known as the cause of hypereosinophilic syndrome (HES). Sixteen IFPs (70%) harboured activating mutations in exons 12 and 18, respectively: V561D (n = 1), R560SDelta561-567 (n = 1), Delta559-561D591H (n = 1), S566RDelta567-571 (n = 3), D842V (n = 7), D842I (n = 1), Delta842-845 (n = 1), and Delta845-848 (n = 1). These mutations equal pathogenic mutations detected in gastrointestinal stromal tumours previously. Activating mutations in exons 10 and 14 were not noted. None of the cases revealed the FIP1L1-PDGFRA translocation. Considering the remarkable number of activating mutations detected in our series, we conclude that the vast majority of IFPs harbour gain-of-function mutations in the PDGFRA gene. The presence of PDGFRA mutations questions the reactive nature of IFPs and raises the possibility of a neoplastic process.

A locus for eosinophilia in the MES rat is on Chromosome 19

Matsumoto Eosinophilia Shinshu (MES) is a rat strain that spontaneously develops eosinophilia and eosinophil-related inflammatory lesions in many organs. We performed chromosomal mapping of the gene for eosinophilia by breeding backcross progeny. The onset of eosinophilia appeared to be delayed in the progeny compared with that in MES, with the prevalence of eosinophilia in the backcross progeny at 12 weeks of age being 22.5%. Genetic linkage analysis with marker loci indicated the major locus for eosinophilia was located at the end of the q arm region of Chromosome 19 (between D19Rat8 and telomere). The locus was denoted eosinophilia 1 (eos1). These data will form the basis for identification of the eos1 gene using a reverse genetic approach, which will hopefully lead to elucidation of the mechanisms involved in eosinophilia and eosinophilopoiesis.

Multiple organ involvement in eosinophilic polymyositis: an autopsy report

This report describes autopsy findings of eosinophilic polymyositis in a 29-year-old woman. She complained of muscle pain and tenderness. A serum examination disclosed elevated creatine kinase, and echocardiography showed lowered cardiac function. Electromyography demonstrated myopathic potentials, and the skeletal muscle biopsy revealed degeneration of muscle fibers accompanying marked eosinophilic infiltration. Peripheral eosinophilia was not prominent. A systemic examination excluded possible etiologic factors, such as hypereosinophilic syndrome, collagen vascular diseases, or parasites. The patient died of heart failure after a 4-month clinical course. The autopsy disclosed a set of histological changes indicating tissue injuries, that is, loss of muscle fibers, interstitial fibrosis, and/or infiltrates of lymphocytes not only in the skeletal muscles and heart but also in various visceral organs. Eosinophils were sparsely scattered. These results indicate that the overrun of eosinophils underlying eosinophilic polymyositis, regardless of the presence of hypereosinophilic syndrome or other systemic disorders, could involve wide-ranging visceral organs.

A Third Locus for Eosinophilia on Chromosome 1 of the MES Rats

Matsumoto Eosinophilia Shinshu (MES) is a rat strain that spontaneously develops eosinophilia and eosinophil-related inflammatory lesions in many organs. In a previous study, we performed chromosomal mapping of the gene for eosinophilia in MES rats using backcross progeny and found that the major locus for eosinophilia was located on chromosome 19. In addition, another quantitative trait locus showing suggestive linkage for blood eosinophil count was found on chromosome 2. In this study, we examined additional marker loci in the backcross progeny and discovered that a third locus for eosinophilia was also located on chromosome 1. These data reinforce the notion that eosinophilia in MES rats is a rather complex genetic trait. However, these results will form the basis for identifying the candidate genes for eosinophilia.