Extramedullary hematopoiesis in the choroid plexus of five dogs

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Dog

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/inhand.asp) is a joint initiative of the societies of toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in most tissues and organs from the dog used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions, lesions induced by exposure to test materials, and relevant infectious and parasitic lesions. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

The choroid plexus stroma constitutes a sanctuary for paediatric B-cell precursor acute lymphoblastic leukaemia in the central nervous system

Despite current central nervous system-directed therapies for childhood B-cell precursor acute lymphoblastic leukaemia, relapse at this anatomical site still remains a challenging issue. Few reports have addressed the study of the specific cellular microenvironments which can promote the survival, quiescence, and therefore chemoresistance of B-cell precursor acute lymphoblastic leukaemia cells in the central nervous system. Herein, we showed by immunofluorescence and electron microscopy that in xenotransplanted mice, leukaemic cells infiltrate the connective tissue stroma of the choroid plexus, the brain structure responsible for the production of cerebrospinal fluid. The ultrastructural study also showed that leukaemia cells are able to migrate through blood vessels located in the choroid plexus stroma. In short-term co-cultures, leukaemic cells established strong interactions with human choroid plexus fibroblasts, mediated by an increased expression of ITGA4 (VLA-4)/ITGAL (LFA-1) and their ligands VCAM1/ICAM1. Upon contact with leukaemia cells, human choroid plexus fibroblasts acquired a cancer-associated fibroblast phenotype, with an increased expression of α-SMA and vimentin as well as pro-inflammatory factors. Human choroid plexus fibroblasts also have the capacity to reduce the proliferative index of leukaemic blasts and promote their survival and chemoresistance to methotrexate and cytarabine. The inhibition of VLA-4/VCAM-1 interactions using anti-VLA-4 antibodies, and the blockade of Notch signalling pathway by using a γ-secretase inhibitor partially restored chemotherapy sensitivity of leukaemia cells. We propose that the choroid plexus stroma constitutes a sanctuary for B-cell precursor acute lymphoblastic leukaemia cells in the central nervous system. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Thoracic and paraspinal extramedullary hematopoiesis in a cat with chronic non-regenerative anemia

Case summary

A 6-year-old neutered male domestic shorthair cat presented with non-regenerative macrocytic anemia of 2 years' duration and minimally ambulatory paraparesis. Neurologic examination suggested an upper motor neuron paresis or T3-L3 myelopathy. The cat was positive for feline immunodeficiency virus (FIV), neutropenic, had polyclonal gammopathy and was euthanized following a hemolytic crisis. At autopsy, multifocal bilateral dark red masses were observed subpleurally around the costochondral junctions, extradurally and paraspinally in the spinal canal, and paravertebrally, on the lateral and ventral subpleural surfaces of the T4-11 vertebrae. Histologic examination of the masses revealed extramedullary hematopoietic tissue composed primarily of erythroid precursors and megakaryocytes, with occasional myeloid precursors and blood-filled sinuses. Bone marrow findings supported ineffective granulopoiesis, and decreased erythropoiesis and megakaryopoiesis, with probable myelodysplasia as the underlying cause of the hematologic abnormalities.

Relevance and novel information

Thoracic, paraspinal and paravertebral extramedullary hematopoietis presenting as masses has not been described previously in cats with chronic anemia. This is a unique case of a thoracic-spinal-epidural extramedullary hematopoietic masses resulting in possible spinal cord compression and paraparesis in a cat.

Extramedullary Hematopoiesis in the Mandibular Lymph Node of Simian-Human Immunodeficiency Virus-Infected Rhesus Monkeys (Macaca mulatta): A Report of Three Cases

Three cases of extramedullary hematopoiesis (EMH) in the mandibular lymph nodes of rhesus monkeys, experimentally infected intravenously with a chimeric simian human immunodeficiency virus, are described. On histopathologic evaluation, multiple sections of mandibular lymph node from all animals showed evidence of EMH, which included erythroid, myeloid, or megakaryocytic precursor cells (or all) within the medullary sinuses. Immunohistochemistry was used for positive identification of multiple cell types. Evidence of EMH was not observed in numerous sections of axillary, inguinal, cervical, hilar, or mesenteric lymph nodes or in any other tissues examined. To our knowledge, this is the first report on EMH within the lymph nodes of rhesus monkeys without an obvious underlying disease process or stringent blood-sampling schedule warranting the need for increased hematopoiesis outside the confines of the bone marrow.

Gene expression and functional annotation of the human and mouse choroid plexus epithelium

BACKGROUND

The choroid plexus epithelium (CPE) is a lobed neuro-epithelial structure that forms the outer blood-brain barrier. The CPE protrudes into the brain ventricles and produces the cerebrospinal fluid (CSF), which is crucial for brain homeostasis. Malfunction of the CPE is possibly implicated in disorders like Alzheimer disease, hydrocephalus or glaucoma. To study human genetic diseases and potential new therapies, mouse models are widely used. This requires a detailed knowledge of similarities and differences in gene expression and functional annotation between the species. The aim of this study is to analyze and compare gene expression and functional annotation of healthy human and mouse CPE.

METHODS

We performed 44k Agilent microarray hybridizations with RNA derived from laser dissected healthy human and mouse CPE cells. We functionally annotated and compared the gene expression data of human and mouse CPE using the knowledge database Ingenuity. We searched for common and species specific gene expression patterns and function between human and mouse CPE. We also made a comparison with previously published CPE human and mouse gene expression data.

RESULTS

Overall, the human and mouse CPE transcriptomes are very similar. Their major functionalities included epithelial junctions, transport, energy production, neuro-endocrine signaling, as well as immunological, neurological and hematological functions and disorders. The mouse CPE presented two additional functions not found in the human CPE: carbohydrate metabolism and a more extensive list of (neural) developmental functions. We found three genes specifically expressed in the mouse CPE compared to human CPE, being ACE, PON1 and TRIM3 and no human specifically expressed CPE genes compared to mouse CPE.

CONCLUSION

Human and mouse CPE transcriptomes are very similar, and display many common functionalities. Nonetheless, we also identified a few genes and pathways which suggest that the CPE between mouse and man differ with respect to transport and metabolic functions.

Peritoneal EMH in a Dog with Immune-Mediated Hemolytic Anemia

Extramedullary hematopoiesis (EMH) is the process by which normal blood cells are produced outside the bone marrow. In humans, EMH effusions are rare and are characterized by the presence of megakaryocytes, immature erythrocytes, immature leukocytes, or combinations of those cells. To the authors’ knowledge, this is the first report to describe a case of peritoneal EMH effusion in a dog. A 5 yr old castrated male shorthaired dachshund presented with a 2 day history of pigmenturia and inappetence. A complete blood count revealed regenerative anemia with marked agglutination, spherocytosis, and an acute inflammatory leukogram characterized by a neutrophilia, regenerative left shift, and monocytosis. Ultrasound-guided aspiration of peritoneal effusion yielded a sample of high nucleated cellularity predominantly composed of mature and immature neutrophils and erythroid precursor cells. The patient was diagnosed with primary immune-mediated hemolytic anemia with concurrent EMH peritoneal effusion. The following case description and discussion explore the clinical findings associated with the unusual effusion and outline the possible pathogenesis by which the EMH effusion may have arisen in the dog.

Spinal cord compression secondary to extramedullary hematopoiesis in a dog

CASE DESCRIPTION

An 11-year-old spayed female Siberian Husky was evaluated because of a 2-week history of progressive paraparesis.

CLINICAL FINDINGS

Results of neurologic examination were consistent with a T3-L3 myelopathy. There were no abnormalities on CBC, and hypercalcemia was noted on serum biochemical analysis. Several hypoechoic splenic nodules were evident on abdominal ultrasonography, and results of fine-needle aspiration cytology were consistent with splenic extramedullary hematopoiesis (EMH). Two compressive, extradural masses in the dorsal epidural space of the thoracolumbar region of the spinal cord were seen on MRI images.

TREATMENT AND OUTCOME

A dorsal laminectomy was performed to remove the extradural spinal masses. Results of histologic examination of tissue samples were consistent with EMH. Following surgery, clinical signs of paraparesis resolved, and there was no recurrence of the masses 24 months after surgery.

CLINICAL RELEVANCE

Extramedullary hematopoesis should be considered as a differential diagnosis in dogs in which results of diagnostic imaging indicate a epidural mass. In human patients, spinal EMH usually occurs secondary to an underlying hematologic disease, but it can also occur spontaneously. Treatment options reported for humans include surgical decompression, radiation therapy, chemotherapy, and blood transfusion. The dog of this report responded favorably to surgical decompression and was clinically normal 2 years after surgery.

Selective localization of bone marrow-derived ramified cells in the brain adjacent to the attachments of choroid plexus

Although the immune system modulates higher functions of the brain under non-inflammatory conditions, how immune cells interact with brain parenchymal cells remains to be determined. Using bone marrow chimeric mice in which the recipients' immune system was reconstituted by marrow cells derived from GFP-transgenic mice by syngeneic intra-bone marrow-bone marrow transplantation (IBM-BMT) and by intravenous (IV)-BMT, we examined the distribution, density and differentiation of donor-derived marrow cells in the brain parenchyma 2 weeks and 1, 4 and 8 months after BMT. Marrow-derived cells started to populate discrete brain regions from 1 to 4 months after BMT, exhibited ramified morphology and expressed Iba-1. The ramified marrow-derived cells were distributed in more brain regions and for a longer time after IBM-BMT than IV-BMT. Most of these discrete regions were adjacent to the attachments of choroid plexus that comprised thinned brain parenchyma consisting of astroglial processes in the narrow channel between the ependyma and pia. These specific portions of astroglial processes expressed fractalkine. In the choroid plexus stroma, not only Iba-1+ myeloid cells but also non-myeloid CXCL12-expressing cells were of bone marrow-origin. Transcripts of fractalkine, CXCL12 and their related molecules such as CX3CR1, ADAM10 and CXCR4 were detected in the tissue consisting of the choroid plexus, the attachments and adjacent brain parenchyma. Thus, bone marrow cells selectively enter the discrete brain regions adjacent to the attachments of choroid plexus and differentiate into ramified myeloid cells. Fractalkine in the attachments of choroid plexus and CXCL12 in the choroid plexus stroma may be involved in these brain-immune interactions.

Extramedullary hematopoiesis: a new look at the underlying stem cell niche, theories of development, and occurrence in animals

Extramedullary hematopoiesis (EMH) is the formation and development of blood cells outside the medullary spaces of the bone marrow. Although widely considered an epiphenomenon, secondary to underlying primary disease and lacking serious clinical or diagnostic implications, the presence of EMH is far from incidental on a molecular basis; rather, it reflects a well-choreographed suite of changes involving stem cells and their microenvironment (the stem cell niche). The goals of this review are to reconsider the molecular basis of EMH based on current knowledge of stem cell niches and to examine its role in the pathophysiologic mechanisms of EMH in animals. The ability of blood cells to home, proliferate, and mature in extramedullary tissues of adult animals reflects embryonic patterns of hematopoiesis and establishment or reactivation of a stem cell niche. This involves pathophysiologic alterations in hematopoietic stem cells, extracellular matrix, stromal cells, and local and systemic chemokines. Four major theories involving changes in stem cells and/or their microenvironment can explain the development of most occurrences of EMH: (1) severe bone marrow failure; (2) myelostimulation; (3) tissue inflammation, injury, and repair; and (4) abnormal chemokine production. EMH has also been reported within many types of neoplasms. Understanding the concepts and factors involved in stem cell niches enhances our understanding of the occurrence of EMH in animals and its relationship to underlying disease. In turn, a better understanding of the prevalence and distribution of EMH in animals and its molecular basis could further inform our understanding of the hematopoietic stem cell niche.

Extramedullary hematopoiesis in a case of benign mixed mammary tumor in a female dog: cytological and histopathological assessment

BACKGROUND

Extramedullary hematopoiesis (EMH) is defined as the presence of hematopoietic stem cells such as erythroid and myeloid lineage plus megakaryocytes in extramedullary sites like liver, spleen and lymph nodes and is usually associated with either bone marrow or hematological disorders. Mammary EMH is a rare condition either in human and veterinary medicine and can be associated with benign mixed mammary tumors, similarly to that described in this case.

CASE PRESENTATION

Hematopoietic stem cells were found in a benign mixed mammary tumor of a 7-year-old female mongrel dog that presents a nodule in the left inguinal mammary gland. The patient did not have any hematological abnormalities. Cytological evaluation demonstrated two distinct cell populations, composed of either epithelial or mesenchymal cells, sometimes associated with a fibrillar acidophilic matrix, apart from megakaryocytes, osteoclasts, metarubricytes, prorubricytes, rubricytes, rubriblasts, promyelocytes, myeloblasts. Histological examination confirmed the presence of an active hematopoietic bone marrow within the bone tissue of a benign mammary mixed tumor.

CONCLUSIONS

EMH is a rare condition described in veterinary medicine that can be associated with mammary mixed tumors. It's detection can be associated with several neoplastic and non-neoplastic mammary lesions, i.e. osteosarcomas, mixed tumors and bone metaplasia.

Cerebrospinal Fluid

This chapter discusses the anatomy, functions, and biochemistry of cerebrospinal fluid (CSF). CSF has four major functions: physical support of neural structures, excretion and “sink” action, intracerebral transport, and control of the chemical environment of the central nervous system. CSF provides a “water jacket” of physical support and buoyancy. The CSF is protective because its volume changes reciprocally with changes in the volume of intracranial contents, particularly blood. Thus, the CSF protects the brain from changes in arterial and central venous pressure associated with posture, respiration, and exertion. Acute or chronic pathological changes in intracranial contents can be accommodated, to a point, by changes in the CSF volume. The direct transfer of brain metabolites into the CSF provides excretory function. This capacity is important because the brain lacks a lymphatic system. The lymphatic function of the CSF is also manifested in the removal of large proteins and cells, such as bacteria or blood cells, by bulk CSF absorption. The “sink” action of the CSF arises from the restricted access of water-soluble substances to the CSF and the low concentration of these solutes in the CSF.

Intracranial extramedullary hematopoiesis associated with pilocytic astrocytoma: a case report

Intracranial EMH is only occasionally found in primary brain tumors (mostly hemangioblastomas) and, to our knowledge, this is the first case of EMH associated with an astrocytoma. Intracranial extramedullary hematopoiesis (EMH) is described in a 29-year-old man with a recurrent pilocytic astrocytoma in the tectal region. Special stains confirmed the identities of erythroid, myeloid and megakaryocytic cells. The patient had no evidence of a predisposing bone marrow disorder or systemic EMH. Although the presence of multinucleated and blastic cells associated with a low-grade brain neoplasm is unusual, recognition of hematopoietic lineages allows EMH to be readily identified. Another tumor resection after a year of follow-up confirmed the absence of malignant progression in this recurrent astrocytoma. The small number of cases describing intracranial EMH in the absence of systemic hematologic abnormalities are correlated with the findings in this case. The low incidence of intracranial EMH indicates that cells with hematopoietic potential are seldom exposed to a supportive microenvironment within the central nervous system. However, intracranial EMH should be included as a potential, ancillary diagnosis when considering brain lesions. This may be particularly true if medical therapies involving growth factors or stem cells are found to promote hematopoiesis.

Neoplastic masquerade syndromes

Masquerade syndromes are classically defined as entities which emulate inflammatory conditions but which are in fact due to a neoplastic process. Careful history and examination in concert with appropriate ancillary investigations and histopathologic evaluation of tissue specimens are required in order to make the correct diagnosis. Many conditions may result in an appearance mimicking an inflammatory condition. The authors review neoplastic conditions which may be considered masquerades. The most common of these is primary intraocular lymphoma or primary central nervous system lymphoma, occurring predominately in older individuals. Diagnostic strategies, therapy, and prognosis are reviewed in detail. Other conditions that can be considered masquerade syndromes are reviewed as well, including lymphomatous and nonlymphomatous conditions, such as melanoma, retinoblastoma, juvenile xanthogranuloma, metastatic lesions, and paraneoplastic syndromes, among others.