Extramedullary hematopoiesis: Elucidating the function of the hematopoietic stem cell niche (Review)

Congenital asplenia impairs heme-iron recycling during erythropoiesis in zebrafish

The spleen is postulated to be a hematopoietic tissue in adult fish; however, clear evidence is still lacking to define its role in hematopoietic activity. In our previous study, a congenitally asplenic zebrafish was generated though gene editing, which provided a new perspective for studying the role of fish spleen in hematopoiesis. In this study, HSC-regulated and erythrocyte marker genes, such as gata1a, gata2, klf1, hbaa1, hbaa2, hbba1 and hbba2 were significantly reduced in congenitally asplenic zebrafish when compared with wild-type (WT). Subsequently, we conducted the transcriptome profiles of whole kidneys from WT and congenitally asplenic zebrafish to explore the possible molecular mechanisms underlying the impaired erythropoiesis caused by congenital asplenia. Our results demonstrated that congenital asplenia might impair heme-iron recycling during erythropoiesis, as evidenced by significant down-regulation of genes associated with iron acquisition (tfr1a, tfa, steap3 and slc25a37) and heme biosynthesis and transport (alas2, fech, uros, urod, copx, ppox and abcb10) in congenitally asplenic zebrafish. In addition, the down-regulation of hemopoiesis-related GO terms, including heme binding, tetrapyrrole binding, iron ion binding, heme metabolic process, heme biosynthetic process, erythrocyte differentiation, iron ion homeostasis and hemoglobin metabolic process confirmed the impaired erythropoiesis induced by congenital asplenia. Our study provides an in-depth understanding of spleen function in regulating heme-iron homeostasis during hematopoiesis, thereby providing valuable insights into pathological responses in splenectomized or congenitally asplenic patients.

Extramedullary Hematopoiesis Adjacent to Vertebral Fracture in a Patient with Pernicious Anemia: Support for a Mechanical Extrusion Mechanism

CASE

A 68-year-old woman presented with a paraspinal mass of indeterminate imaging characteristics. Workup and computed tomography-guided Fine Needle Aspiration (FNA) aspiration revealed extramedullary hematopoiesis (EMH) adjacent to a prior compression fracture in the setting of pernicious anemia.

CONCLUSION

The combination of findings suggests a possible relationship of the compression fracture and the EMH because of traumatic extravasation of marrow contents, with the patient's underlying anemia possibly providing an underlying predisposition to EMH.

MCL-1 Inhibitor S63845 Distinctively Affects Intramedullary and Extramedullary Hematopoiesis

Conventional chemotherapy for killing cancer cells using cytotoxic drugs suffers from low selectivity, significant toxicity, and a narrow therapeutic index. Hyper-specific targeted drugs achieve precise destruction of tumors by inhibiting molecular pathways that are critical to tumor growth. Myeloid cell leukemia 1 (MCL-1), an important pro-survival protein in the BCL-2 family, is a promising antitumor target. In this study, we chose to investigate the effects of S63845, a small-molecule inhibitor that targets MCL-1, on the normal hematopoietic system. A mouse model of hematopoietic injury was constructed, and the effects of the inhibitor on the hematopoietic system of mice were evaluated via routine blood tests and flow cytometry. The results showed that S63845 affected the hematopoiesis of various lineages in the early stage of action, causing extramedullary compensatory hematopoiesis in the myeloid and megakaryocytic lineages. The maturation of the erythroid lineage in the intramedullary and extramedullary segments was blocked to varying degrees, and both the intramedullary and extramedullary lymphoid lineages were inhibited. This study provides a complete description of the effects of MCL-1 inhibitor on the intramedullary and extramedullary hematopoietic lineages, which is important for the selection of combinations of antitumor drugs and the prevention of adverse hematopoiesis-related effects.

The hepatic extramedullary hematopoiesis during experimental murine Schistosomiasis mansoni

Many years ago, our research group has demonstrated extramedullary hematopoiesis in the peripheral zone of murine hepatic schistosomal granulomas. In the present study, we revisit this phenomenon using new technical and conceptual approaches. Therefore, newborn mice were percutaneously infected by Schistosoma mansoni cercariae and euthanized between 35- and 60-days post infection. Liver samples were submitted to histopathology and immunohistochemical analyses. Cells under mitosis and/or expressing Ki67 demonstrated the proliferation of hematopoietic cells both around the parasite’s eggs trapped in the liver and around hepatic vessels. After 50 days post infection, proliferating cells at different levels on differentiation were located preferentially in the peripheral zone of the granulomas, around the vessels and inside the sinusoids. The presence of acidic and sulfated glycoconjugates, reticular fibers and the absence of fibronectin characterized the microenvironment for attraction and maintenance of hematopoiesis. Some neutrophils secreted MMP9 from the earliest points of infection, indicating degradation of the extracellular matrix in regions of histolysis and a possible chemoattraction of hematopoietic stem cells to the liver. Fall-3+ cells and Sca-1+ cells indicated that early hematopoietic progenitors could be mobilized to the liver. Groups of vWF+ megakaryocytes suggest chemoattraction of these cells and/or migration, proliferation, and differentiation of very immature progenitors to this organ. The increase of blood vessels and extramedullary hematopoiesis in this environment, where markers of immature hematopoietic and endothelial cells have been identified, points to the possibility of the presence of progenitors for endothelial and hematopoietic cells in the liver during the infection. There is also the possibility of concomitant migration of more differentiated hematopoietic progenitors, that proliferate and differentiate in the liver, and the occurrence of angiogenesis caused by inflammation or release of ovular antigens that stimulate the activation and proliferation of endothelial cells. Altogether, these data increase knowledge about a murine model that is of interest for investigating the pathology of the schistosomiasis and also the dynamics of hematopoiesis.

Neutrophils as regulators of macrophage-induced inflammation in a setting of allogeneic bone marrow transplantation

Clinical data reveal that patients with allogeneic hematopoietic stem cell transplantation (HSCT) are vulnerable to infection and prone to developing severe sepsis, which greatly compromises the success of transplantation, indicating a dysregulation of inflammatory immune response in this clinical setting. Here, by using a mouse model of haploidentical bone marrow transplantation (haplo-BMT), we found that uncontrolled macrophage inflammation underlies the pathogenesis of both LPS- and E.coli-induced sepsis in recipient animals with graft-versus-host disease (GVHD). Deficient neutrophil maturation in GVHD mice post-haplo-BMT diminished modulation of macrophage-induced inflammation, which was mechanistically dependent on MMP9-mediated activation of TGF-β1. Accordingly, adoptive transfer of mature neutrophils purified from wild-type donor mice inhibited both sterile and infectious sepsis in GVHD mice post-haplo-BMT. Together, our findings identify a novel mature neutrophil-dependent regulation of macrophage inflammatory response in a haplo-BMT setting and provide useful clues for developing clinical strategies for patients suffering from post-HSCT sepsis.

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Macrophage inflammation leads to the development of post-haplo-BMT sepsis

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Impaired neutrophil maturation diminishes regulation of macrophage inflammation

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Extramedullary granulopoiesis fails to support neutrophil maturation after haplo-BMT

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Neutrophils regulate macrophage inflammation via MMP9-mediated TGF-β1 activation

Coexisting Extra-Medullary Manifestation of Chronic Myelomonocytic Leukemia and Follicular Lymphoma What's Between Neoplastic Follicles Matters

We illustrate a rare case of coexisting extramedullary manifestation of CMML and new onset follicular lymphoma within the same core-needle biopsy of a lymph node. We discuss the differences between extramedullary hematopoiesis and extramedullary manifestation of myeloid neoplasms. We also highlight the importance of generous tissue sampling and thorough examination of nodal tissue in the setting of an established myeloid neoplasm to avoid missing rare but possible nodal involvement.

The Quantification and Significance of Extramedullary Hematopoiesis Seen on Liver Biopsy Specimens

OBJECTIVES

Extramedullary hematopoiesis (EMH) may occur in the liver and is often considered pathologic in adults. Many hematologic and nonhematologic disorders are associated with the development of EMH. However, it is unclear whether the presence of EMH is always pathologic. At present, no formal grading system for EMH in the liver exists.

METHODS

We reviewed 42 liver biopsy specimens with EMH and developed a novel grading system to quantify the degree of EMH from 1 to 3 based on the number of EMH foci in 10 high-power fields.

RESULTS

Most patients had nonhematologic conditions (n = 25). Seventeen patients had a hematologic condition, most frequently a myeloproliferative neoplasm (n = 9). Patients with an underlying hematologic condition had a significantly higher EMH grade compared with those without a hematologic condition (P < .0001). All patients with grade 3 EMH had an underlying hematologic diagnosis, and most (86%) patients with grade 1 EMH had a nonhematologic disorder.

CONCLUSIONS

Our data suggest that EMH grading in the liver is feasible and can identify patients who may have an underlying hematologic condition, which can guide further diagnostic workup.

Adrenal extramedullary hematopoiesis in the setting of anti-Diego antibody and congenital dyserythropoietic anemia

Extramedullary hematopoiesis occurs in the setting of hematologic disorders or malignancies when the activity of the bone marrow is insufficient to generate blood cells. We report a unique case of adrenal extramedullary hematopoiesis diagnosed in a 16 year old female with a history of anti-Diego antibody and congenital dyserythropoietic anemia. She presented with an enlarging adrenal mass and underwent surgical resection. Pathology revealed extramedullary hematopoiesis. On literature review, we identified only two prior existing cases of adrenal extramedullary hematopoiesis in pediatric patients, with no prior case reports of adrenal extramedullary hematopoiesis occurring in patients with anti-Diego antibody or in those with congenital dyserythropoietic anemia.

Genomic Designs of rAAVs Contribute to Pathological Changes in the Livers and Spleens of Mice

Recombinant AAV (rAAV) gene therapy is being investigated as an effective therapy for several diseases including hemophilia B. Reports of liver tumor development in certain mouse models due to AAV treatment and genomic integration of the rAAV vector has raised concerns about the long-term safety and efficacy of this gene therapy. To investigate whether rAAV treatment causes cancer, we utilized two mouse models, inbred C57BL/6 and hemophilia B Balb/C mice (HemB), to test if injecting a high dose of various rAAV8 vectors containing or lacking hFIX transgene, a Poly-A sequence, or the CB or TTR promoter triggered liver fibrosis and/or cancer development over the course of the 6.5-month study. We observed no liver tumors in either mouse cohort regardless of rAAV treatment through ultrasound imaging, gross anatomical assessment at sacrifice, and histology. We did, however, detect differences in collagen deposition in C57BL/6 livers and HemB spleens of rAAV-injected mice. Pathology reports of the HemB mice revealed many pathological phenomena, including fibrosis and inflammation in the livers and spleens across different AAV-injected HemB mice. Mice from both cohorts injected with the TTR-hFIX vector demonstrated minimal adverse events. While not tumorigenic, high dose of rAAVs, especially those with incomplete genomes, can influence liver and spleen health negatively that could be problematic for cementing AAVs as a broad therapeutic option in the clinic.

Maternal High-Fat Feeding Affects the Liver and Thymus Metabolic Axis in the Offspring and Some Effects Are Attenuated by Maternal Diet Normalization in a Minipig Model

Maternal high-fat diet (HFD) affects metabolic and immune development. We aimed to characterize the effects of maternal HFD, and the subsequent diet-normalization of the mothers during a second pregnancy, on the liver and thymus metabolism in their offspring, in minipigs. Offspring born to high-fat (HFD) and normal diet (ND) fed mothers were studied at week 1 and months 1, 6, 12 of life. Liver and thymus glucose uptake (GU) was measured with positron emission tomography during hyperinsulinemic-isoglycemia. Histological analyses were performed to quantify liver steatosis, inflammation, and hepatic hematopoietic niches (HHN), and thymocyte size and density in a subset. The protocol was repeated after maternal-diet-normalization in the HFD group. At one week, HFD_off were characterized by hyperglycemia, hyperinsulinemia, severe insulin resistance (IR), and high liver and thymus GU, associating with thymocyte size and density, with elevated weight-gain, liver IR, and steatosis in the first 6 months of life. Maternal diet normalization reversed thymus and liver hypermetabolism, and increased HHN at one week. It also normalized systemic insulin-sensitivity and liver fat content at all ages. Instead, weight-gain excess, hyperglycemia, and hepatic IR were still observed at 1 month, i.e., end-lactation. We conclude that intra-uterine HFD exposure leads to time-changing metabolic and immune-correlated abnormalities. Maternal diet-normalization reversed most of the effects in the offspring.

Extramedullary Hematopoiesis in the Dura Mater During Treatment of a CNS Embryonal Tumor

Extramedullary hematopoiesis (EMH) is hematopoiesis occurring outside of the bone marrow. It has been reported to develop in abdominal organs or lymph nodes after chemotherapy. Here, the authors describe a patient with a localized central nervous system embryonal tumor who, during intensive chemotherapy, developed dural nodules. Biopsy revealed these nodules to be EMH. Without a pathologic diagnosis, this may have been considered disease progression, altering the patient's treatment plan. This report intends to serve as a reminder that EMH should be included in the differential diagnosis of suspicious lesions and highlights the importance of their biopsy because of potential management implications.

The Involvement of Macrophage Colony Stimulating Factor on Protein Hydrolysate Injection Mediated Hematopoietic Function Improvement

Protein hydrolysate injection (PH) is a sterile solution of hydrolyzed protein and sorbitol that contains 17 amino acids and has a molecular mass of 185.0-622.0 g/mol. This study investigated the effect of PH on hematopoietic function in K562 cells and mice with cyclophosphamide (CTX)-induced hematopoietic dysfunction. In these myelosuppressed mice, PH increased the number of hematopoietic cells in the bone marrow (BM) and regulated the concentration of several factors related to hematopoietic function. PH restored peripheral blood cell concentrations and increased the numbers of hematopoietic stem cells and progenitor cells (HSPCs), B lymphocytes, macrophages, and granulocytes in the BM of CTX-treated mice. Moreover, PH regulated the concentrations of macrophage colony stimulating factor (M-CSF), interleukin (IL)-2, and other hematopoiesis-related cytokines in the serum, spleen, femoral condyle, and sternum. In K562 cells, the PH-induced upregulation of hematopoiesis-related proteins was inhibited by transfection with M-CSF siRNA. Therefore, PH might benefit the BM hematopoietic system via the regulation of M-CSF expression, suggesting a potential role for PH in the treatment of hematopoietic dysfunction caused by cancer therapy.

Fine-needle aspiration diagnosis of clonal extramedullary hematopoiesis in a case of myeloproliferative neoplasm

Extramedullary hematopoiesis (EMH)-the proliferation of hematopoietic progenitors outside of the bone marrow (BM) is a well-known phenomenon in myeloproliferative neoplasms (MPN). Abundant literature describes EMH at various body sites in cases of MPN, and some studies showed the presence of cytogenetic changes associated with MPN in the EMH tissues. We present a case of an 80-year-old female, with a history of MPN, presenting with mediastinal adenopathy. The transbronchial fine-needle aspiration (FNA) of the mediastinal lymph node showed EMH with atypical megakaryocytes and del(13q) demonstrated by fluorescence in situ hybridization. The subsequent BM biopsy demonstrated myelofibrosis with atypical megakaryocytes harboring the same cytogenetic abnormality. Our case highlights the capability of FNA cytology for providing accurate morphologic, immunohistochemical, and cytogenetic diagnosis of clonal EMH.

Characteristic Distribution of Hematopoietic Cells in Bone Marrow of Xenopus Laevis

Bone marrow is the principal site of hematopoiesis in mammals. Amphibians were the first phylogenetic group in vertebrates to acquire bone marrow, but the distribution of hematopoietic cells in the bone marrow of the primitive frog, Xenopus laevis (X. laevis) has not been well documented. The purpose of this study was to perform a histological investigation of the distribution of hematopoietic cells in femoral bone marrow at various stages of development in X. laevis. Hematopoietic cells showed preferential distribution on the endosteal surface of cortical bone throughout all stages of development, from tadpole to aged frog. In mature frogs, hematopoietic cells appeared at the boundary between the epiphysis and the bone marrow. The distribution of hematopoietic cells around the blood vessels was limited to a small number of vessels in the bone marrow. Abundant adipose tissue was observed in the bone marrow cavity from the tadpole stage to the mature frog stage. Hematopoietic cells showed preferential distribution in a belt-like fashion on the surface of newly-formed bones in a bone regeneration model in the diaphysis of X. laevis. These results indicate that the distribution of hematopoietic cells in bone marrow in X. laevis differs from that in mammals, and that the bone marrow of X. laevis constitutes a useful model for exploring the mechanism underlying the phylogenetic differentiation of bone marrow hematopoiesis.

Investigation and Analysis of Iron-Deficiency Anemia Complicated by Splenomegaly

Objective

This study aimed to determine the incidence of iron-deficiency anemia (IDA) complicated by splenomegaly in our hospital over the past 6 years and to analyze the possible causes of this result.

Methods

This is a retrospective study. In total, 668 patients with IDA who were hospitalized in the hematology department of our hospital from 2013 to 2019 were selected as the research subjects and included in the IDA group, and 3201 patients who underwent outpatient physical examinations in our hospital during the same period were included in the control group. The incidences of splenomegaly in the IDA and control groups were calculated, and the difference was analyzed by means of statistical methods.

Results

Among the 668 IDA patients, 46 (6.9%) had splenomegaly, and among the 3201 patients in the control group, 21 had splenomegaly (0.7%). The incidence of splenomegaly was significantly higher in the IDA group than in the control group, and the severity of anemia in the IDA group was associated with the occurrence of splenomegaly. Specifically, the incidence of splenomegaly was 12.4% among patients with severe anemia and as high as 50% among patients with extremely severe anemia.

Conclusion

IDA is correlated with the incidence of splenomegaly, and the incidence of splenomegaly significantly increases as the severity of IDA increases. This is considered to be caused by extramedullary hematopoiesis.

Myelopoiesis during Solid Cancers and Strategies for Immunotherapy

Our understanding of the relationship between the immune system and cancers has undergone significant discovery recently. Immunotherapy with T cell therapies and checkpoint blockade has meaningfully changed the oncology landscape. While remarkable clinical advances in adaptive immunity are occurring, modulation of innate immunity has proven more difficult. The myeloid compartment, including macrophages, neutrophils, and dendritic cells, has a significant impact on the persistence or elimination of tumors. Myeloid cells, specifically in the tumor microenvironment, have direct contact with tumor tissue and coordinate with tumor-reactive T cells to either stimulate or antagonize cancer immunity. However, the myeloid compartment comprises a broad array of cells in various stages of development. In addition, hematopoietic stem and progenitor cells at various stages of myelopoiesis in distant sites undergo significant modulation by tumors. Understanding how tumors exert their influence on myeloid progenitors is critical to making clinically meaningful improvements in these pathways. Therefore, this review will cover recent developments in our understanding of how solid tumors modulate myelopoiesis to promote the formation of pro-tumor immature myeloid cells. Then, it will cover some of the potential avenues for capitalizing on these mechanisms to generate antitumor immunity.

Niche-Mediated Integrin Signaling Supports Steady-State Hematopoiesis in the Spleen

Outside-in integrin signaling regulates cell fate decisions in a variety of cell types, including hematopoietic stem cells (HSCs). Our earlier published studies showed that interruption of periostin (POSTN) and integrin-αv (ITGAV) interaction induces faster proliferation in HSCs with developmental stage-dependent functional effects. In this study, we examined the role of POSTN-ITGAV axis in lymphohematopoietic activity in spleen that hosts a rare population of HSCs, the functional regulation of which is not clearly known. Vav-iCre-mediated deletion of Itgav in the hematopoietic system led to higher proliferation rates, resulting in increased frequency of primitive HSCs in the adult spleen. However, in vitro CFU-C assays demonstrated a poorer differentiation potential following Itgav deletion. This also led to a decrease in the white pulp area with a significant decline in the B cell numbers. Systemic deletion of its ligand, POSTN, phenocopied the effects noted in Vav-Itgav^-/- mice. Histological examination of Postn-deficient spleen also showed an increase in the spleen trabecular areas. Importantly, these are the myofibroblasts of the trabecular and capsular areas that expressed high levels of POSTN within the spleen tissue. In addition, vascular smooth muscle cells also expressed POSTN. Through CFU-S₁₂ assays, we showed that hematopoietic support potential of stroma in Postn-deficient splenic hematopoietic niche was defective. Overall, we demonstrate that POSTN-ITGAV interaction plays an important role in spleen lymphohematopoiesis.

15-PGDH inhibition activates the splenic niche to promote hematopoietic regeneration

The splenic microenvironment regulates hematopoietic stem and progenitor cell (HSPC) function, particularly during demand-adapted hematopoiesis; however, practical strategies to enhance splenic support of transplanted HSPCs have proved elusive. We have previously demonstrated that inhibiting 15-hydroxyprostaglandin dehydrogenase (15-PGDH), using the small molecule (+)SW033291 (PGDHi), increases BM prostaglandin E₂ (PGE₂) levels, expands HSPC numbers, and accelerates hematologic reconstitution after BM transplantation (BMT) in mice. Here we demonstrate that the splenic microenvironment, specifically 15-PGDH high-expressing macrophages, megakaryocytes (MKs), and mast cells (MCs), regulates steady-state hematopoiesis and potentiates recovery after BMT. Notably, PGDHi-induced neutrophil, platelet, and HSPC recovery were highly attenuated in splenectomized mice. PGDHi induced nonpathologic splenic extramedullary hematopoiesis at steady state, and pretransplant PGDHi enhanced the homing of transplanted cells to the spleen. 15-PGDH enzymatic activity localized specifically to macrophages, MK lineage cells, and MCs, identifying these cell types as likely coordinating the impact of PGDHi on splenic HSPCs. These findings suggest that 15-PGDH expression marks HSC niche cell types that regulate hematopoietic regeneration. Therefore, PGDHi provides a well-tolerated strategy to therapeutically target multiple HSC niches, promote hematopoietic regeneration, and improve clinical outcomes of BMT.

Perinatal and early-life cobalt exposure impairs essential metal metabolism in immature ICR mice

The objective of the present study was to assess the impact of cobalt (Co) exposure on tissue distribution of iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn), as well as serum hepcidin levels in immature mice (18, 25, 30 days). Pregnant mice were exposed to 75 mg/kg b.w. cobalt chloride (CoCl₂ × 6H2O) with drinking water starting from 3 days before delivery and during lactation. At weaning (day 25) the offspring were separated and housed in individual cages with subsequent exposure to 75 mg/kg b.w. CoCl₂ until 30 days postnatally. Evaluation of tissue metal levels was performed by an inductively coupled plasma-mass spectrometry (ICP-MS). Serum hepcidin level was assayed by enzyme linked immunosorbent assay (ELISA). Cobalt exposure resulted in a time- and tissue-dependent increase in Co levels in kidney, spleen, liver, muscle, erythrocytes, and serum on days 18, 25, and 30. In parallel with increasing Co levels, CoCl₂ exposure resulted in a significant accumulation of Cu, Fe, Mn, and Zn in the studied tissues, with the effect being most pronounced in 25-day-old mice. Cobalt exposure significantly increased serum hepcidin levels only in day18 mice. The obtained data demonstrate that Co exposure may alter essential metal metabolism in vivo.

Contribution of Extramedullary Hematopoiesis to Atherosclerosis. The Spleen as a Neglected Hub of Inflammatory Cells

Cardiovascular diseases (CVDs) incidence is becoming higher. This fact is promoted by metabolic disorders such as obesity, and aging. Atherosclerosis is the underlying cause of most of these pathologies. It is a chronic inflammatory disease that begins with the progressive accumulation of lipids and fibrotic materials in the blood-vessel wall, which leads to massive leukocyte recruitment. Rupture of the fibrous cap of the atherogenic cusps is responsible for tissue ischemic events, among them myocardial infarction. Extramedullary hematopoiesis (EMH), or blood cell production outside the bone marrow (BM), occurs when the normal production of these cells is impaired (chronic hematological and genetic disorders, leukemia, etc.) or is altered by metabolic disorders, such as hypercholesterolemia, or after myocardial infarction. Recent studies indicate that the main EMH tissues (spleen, liver, adipose and lymph nodes) complement the hematopoietic function of the BM, producing circulating inflammatory cells that infiltrate into the atheroma. Indeed, the spleen, which is a secondary lymphopoietic organ with high metabolic activity, contains a reservoir of myeloid progenitors and monocytes, constituting an important source of inflammatory cells to the atherosclerotic lesion. Furthermore, the spleen also plays an important role in lipid homeostasis and immune-cell selection. Interestingly, clinical evidence from splenectomized subjects shows that they are more susceptible to developing pathologies, such as dyslipidemia and atherosclerosis due to the loss of immune selection. Although CVDs represent the leading cause of death worldwide, the mechanisms involving the spleen-atherosclerosis-heart axis cross-talk remain poorly characterized.

The Hepatic Microenvironment Uniquely Protects Leukemia Cells through Induction of Growth and Survival Pathways Mediated by LIPG

Due to the disseminated nature of leukemia, malignant cells are exposed to many different tissue microenvironments, including a variety of extramedullary sites. In the present study, we demonstrate that leukemic cells residing in the liver display unique biological properties and also contribute to systemic changes that influence physiologic responses to chemotherapy. Specifically, the liver microenvironment induces metabolic adaptations via upregulating expression of endothelial lipase in leukemia cells, which not only stimulates tumor cell proliferation through polyunsaturated fatty acid-mediated pathways, but also promotes survival by stabilizing antiapoptotic proteins. Additionally, hepatic infiltration and tissue damage caused by malignant cells induces release of liver-derived enzymes capable of degrading chemotherapy drugs, an event that further protects leukemia cells from conventional therapies. Together, these studies demonstrate a unique role for liver in modulating the pathogenesis of leukemic disease and suggest that the hepatic microenvironment may protect leukemia cells from chemotherapeutic challenge. SIGNIFICANCE: The studies presented herein demonstrate that the liver provides a microenvironment in which leukemia cells acquire unique metabolic properties. The adaptations that occur in the liver confer increased resistance to chemotherapy. Therefore, we propose that therapies designed to overcome liver-specific metabolic changes will yield improved outcomes for patients with leukemia.This article is highlighted in the In This Issue feature, p. 211.

Stress erythropoiesis: definitions and models for its study

Steady-state erythropoiesis generates new erythrocytes at a constant rate, and it has enormous productive capacity. This production is balanced by the removal of senescent erythrocytes by macrophages in the spleen and liver. Erythroid homeostasis is highly regulated to maintain sufficient erythrocytes for efficient oxygen delivery to the tissues, while avoiding viscosity problems associated with overproduction. However, there are times when this constant production of erythrocytes is inhibited or is inadequate; at these times, erythroid output is increased to compensate for the loss of production. In some cases, increased steady-state erythropoiesis can offset the loss of erythrocytes but, in response to inflammation caused by infection or tissue damage, steady-state erythropoiesis is inhibited. To maintain homeostasis under these conditions, an alternative stress erythropoiesis pathway is activated. Emerging data suggest that the bone morphogenetic protein 4 (BMP4)-dependent stress erythropoiesis pathway is integrated into the inflammatory response and generates a bolus of new erythrocytes that maintain homeostasis until steady-state erythropoiesis can resume. In this perspective, we define the mechanisms that generate new erythrocytes when steady-state erythropoiesis is impaired and discuss experimental models to study human stress erythropoiesis.

Conditions for combining gene therapy with bone marrow transplantation in murine Krabbe disease

Introduction: Krabbe disease (KD) is an autosomal recessive lysosomal disorder caused by mutations in the galactocerebrosidase (GALC) gene. This results in defective myelination in the peripheral and central nervous systems due to low GALC activity. Treatment at this time is limited to hematopoietic stem cell transplantation (HSCT) in pre-symptomatic individuals. While this treatment extends the lives of treated individuals, most have difficulty walking by the end of the first decade due to peripheral neuropathy. Studies in the murine model of KD, twitcher (twi) combining bone marrow transplantation (BMT) with AAVrh10-mGALC showed a great extension of life from 40 days to about 400 days, with some living a full life time. Methods: In order to find the optimum conditions for dosing and timing of this combined treatment, twi mice were injected with five doses of AAVrh10-mGALC at different times after BMT. Survival, as well as GALC expression were monitored along with studies of sciatic nerve myelination and possible liver pathology. Results: Dosing had a pronounced effect on survival and measured GALC activity. There was window of time after BMT to inject the viral vector and see similar results, however delaying both the BMT and the viral injection shortened the lifespans of the treated mice. Lowering the viral dose too much decreased the correction of the sciatic nerve myelination. There was no evidence for hepatic neoplasia. Conclusion: These studies provide the conditions optimum for successfully treating the murine model of KD. There is some flexibility in dosing and timing to obtain a satisfactory outcome. These studies are critical to the planning of a human trial combining the "standard of care", HSCT, with a single iv injection of AAVrh10-GALC.

Calf thymus polypeptide improved hematopoiesis via regulating colony-stimulating factors in BALB/c mice with hematopoietic dysfunction

Calf thymus polypeptide (CTP) is prepared from calf thymus. It has a molecular mass of <10 kilodalton (kDa) and contains 17 types of amino acids. This study investigated the hematopoietic function-improvement effect of CTP in CHRF, K562, and bone marrow mononuclear cells; mice with immunosuppression; and with hematopoietic dysfunction. In mice with immunosuppression, CTP enhanced the cytotoxic activity of natural killer cells and the proliferation of lymphocytes and regulated the levels of immunoglobulins. It also enhanced the proliferation and differentiation of CHRF and K562 cells by upregulating the expression of proliferation- and differentiation-related proteins. In mice with hematopoietic dysfunction, CTP restored white blood cell, neutrophil, and hemoglobin proportions in the peripheral blood and enhanced the levels of B lymphocytes and hematopoietic stem cells and progenitor cells in the bone marrow. CTP effectively regulated the levels of hematopoiesis-related cytokines, such as granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), interleukin 2, and interferons-γ, and enhanced the expression of hematopoiesis-related proteins in both primary bone marrow cells and mice with hematopoietic dysfunction. These results indicate that CTP has hematopoietic function-improvement effect and this effect may be related to the modulation of colony-stimulating factors (CSFs) and related signaling pathways.

Ocular Manifestations in Patients with Philadelphia-Negative Myeloproliferative Neoplasms

The major complications of Philadelphia-negative (Ph-Negative) myeloproliferative neoplasms (MPNs) are thrombosis, haemorrhage and leukemic transformation. As systemic and haematological diseases, MPNs have the potential to affect many tissues and organs. Some complications lead to the diagnosis of MPNs, but other signs and symptoms are often misdiagnosed or neglected as a sign of MPN disease. Therefore, we reviewed the current literature to investigate and delineate the clinical manifestations seen in the eyes of Ph-negative MPN patients. We found that ocular manifestations are common among patients with MPNs. The most frequently described manifestations are due to the consequences of haematological abnormalities causing microvascular disturbances and hyperviscosity. More serious and vision-threatening complications as thrombotic events in the eyes have been repeatedly reported as well. These ocular symptoms may precede more serious extraocular complications. Accordingly, combined ophthalmological and haematological management have the potential to discover these diseases earlier and prevent morbidity and mortality in these patients. Furthermore, routine ophthalmological screening of all newly diagnosed MPN patients may be a preventive approach for early diagnosis and timely treatment of the ocular manifestations.

A case report of a rare omental extramedullary hematopoiesis in an adult: 'an idiopathic finding'

This is a case of a 62-year-old female, known to have multiple medical problems, who presented to her primary care physician with an intermittent abdominal pain and discomfort for a few months. The initial work-up showed mild leucocytosis and a small mass in the omentum. Given that the most concerning differential diagnosis was malignancy, the patient was referred to oncology, where biopsy of the mass showed omentum extramedullary hematopoiesis. The differential diagnosis was wide; however, a repeat computed tomography (CT) scan of the abdomen and pelvis did show persistence of the omental mass. After ruling out any possible causes, including myelofibrosis, with a normal bone marrow, her extramedullary hematopoiesis was deemed of unknown origin and with no clear explanation. Therefore, the patient was diagnosed with a rare adult idiopathic omental extramedullary hematopoiesis that was stable over time.

Identification and characterization of three CXC chemokines in Asian swamp eel (Monopterus albus) uncovers a third CXCL11_like group in fish

Chemokines direct cell migration in development and immune defense, and bridge between innate and adaptive immune responses. The chemokine gene family has been rapidly evolving and has undergone species/lineage-specific expansion. Mammals possess inflammatory CXC chemokines CXCL1-8/15 and CXCL9-11 sub-groups, and homeostatic CXCL12-14, 16-17. Orthologues of mammalian CXCL12-14, three chemokines related to CXCL1-8/15 (CXCL8_L1-3), two chemokines related to CXC9-11 (CXCL11_L1-2), and five fish-specific chemokines (CXCL_F1-5) have been described in teleosts. In this study, we reported three novel CXC chemokines in Asian swamp eel Monopterus albus, a commercially important freshwater fish species in China. Two of them belong to the fish-specific CXCL_F2 group, named CXCL_F2a/b, that share 89.5% amino acid identity. The other (CXCL11_L3) belongs to a third CXCL11_L related to the mammalian CXCL9-11 subfamily found only in percomorph fish species, and is the only CXCL9-11 related molecules in this lineage. Mammalian CXCL9-11 attract Th1 cells, and block the migration of Th2 cells in an immune response. This study suggests that all major lineages of teleosts have a CXCL9-11 related chemokine that will aid future functional investigation of CXCL11_L in fish. Cxcl_f2a is highly expressed constitutively in the skin of swamp eels that may attract immune cells to protect the skin in the absence of scales. Cxcl11_l3 and cxcl_f2b are highly expressed in immune tissues/organs and are up-regulated by the viral mimic poly I:C, but not bacterial infection in vivo, suggesting their role in anti-viral defense. The two cxcl_f2 paralogues are differentially expressed and modulated, indicating sub- and/or neo-functionalization.

Compressive Dorsal Myelopathy Secondary to Extramedullary Hematopoiesis in a Thalassemic Patient

Background

Extramedullary hematopoiesis (EMH) is one of the rare causes of spinal cord compression (SCC). It results from noncancerous proliferation of hematopoietic tissue outside the bone marrow as a compensatory mechanism for ineffective erythropoiesis. It occurs in the paraspinal area in 11-15% of thalassemic patients in intermediate and severe cases causing a paraspinal compressive mass. We present a rare case of spinal EMH with thoracic cord compression in a 22-year-old female with beta thalassemia who presented with paraparesis and we provide a review of literature.

Case Report

A 22-year-old female patient with a known history of beta thalassemia presented with subacute onset of weakness and numbness of both lower limbs with a sensory level at T6. Magnetic resonance imaging (MRI) of the dorsal spine showed cord compression secondary to paraspinal EMH from T2 to T9 with most prominent compression over T5. She was managed with blood transfusion and low-dose radiotherapy.

Conclusion

Although rare, EMH should be suspected in thalassemic patients presenting with paraplegia. Treatment with blood transfusions is usually effective. Other options include radiotherapy, surgery, hydroxyurea or a combination of these modalities.

Splenomegaly induced by anemia impairs T cell movement in the spleen partially via EPO

The spleen is an important secondary lymph organ. Splenomegaly induced by anemia could affect the function of spleen in immune responses. We observe that anemia induced in mice with reduced peripheral T cell trafficking to the spleen T cell zones as well as CCL21 and CCL19 expression. In accordance with previous research, we found that the production of EPO in the mice kidney was sharply increased post anemia. In addition, mice were injected with different doses of EPO. Our results show that with the increased dosage of EPO, the chemokine expression in the spleen is lowered with a decrease in peripheral T cell homing to the spleen T cell zones. At last, our results show that the anemia mice model administrated with anti-EPO antibody had a higher expression of spleen CCL19 and CCL21 and an increased count of periphery T cells trafficking to spleen T cell zones at day 3 post induction. These data indicate that anemia could disturb T cell movement in the spleen, which might further affect T cell immune response, with partial involvement of EPO.

Down-regulation of GATA1-dependent erythrocyte-related genes in the spleens of mice exposed to a space travel

Secondary lymphoid organs are critical for regulating acquired immune responses. The aim of this study was to characterize the impact of spaceflight on secondary lymphoid organs at the molecular level. We analysed the spleens and lymph nodes from mice flown aboard the International Space Station (ISS) in orbit for 35 days, as part of a Japan Aerospace Exploration Agency mission. During flight, half of the mice were exposed to 1 g by centrifuging in the ISS, to provide information regarding the effect of microgravity and 1 g exposure during spaceflight. Whole-transcript cDNA sequencing (RNA-Seq) analysis of the spleen suggested that erythrocyte-related genes regulated by the transcription factor GATA1 were significantly down-regulated in ISS-flown vs. ground control mice. GATA1 and Tal1 (regulators of erythropoiesis) mRNA expression was consistently reduced by approximately half. These reductions were not completely alleviated by 1 g exposure in the ISS, suggesting that the combined effect of space environments aside from microgravity could down-regulate gene expression in the spleen. Additionally, plasma immunoglobulin concentrations were slightly altered in ISS-flown mice. Overall, our data suggest that spaceflight might disturb the homeostatic gene expression of the spleen through a combination of microgravity and other environmental changes.

Targeting the Spleen as an Alternative Site for Hematopoiesis

Bone marrow is the main site for hematopoiesis in adults. It acts as a niche for hematopoietic stem cells (HSCs) and contains non-hematopoietic cells that contribute to stem cell dormancy, quiescence, self-renewal, and differentiation. HSC also exist in resting spleen of several species, although their contribution to hematopoiesis under steady-state conditions is unknown. The spleen can however undergo extramedullary hematopoiesis (EMH) triggered by physiological stress or disease. With the loss of bone marrow niches in aging and disease, the spleen as an alternative tissue site for hematopoiesis is an important consideration for future therapy, particularly during HSC transplantation. In terms of harnessing the spleen as a site for hematopoiesis, here the remarkable regenerative capacity of the spleen is considered with a view to forming additional or ectopic spleen tissue through cell engraftment. Studies in mice indicate the potential for such grafts to support the influx of hematopoietic cells leading to the development of normal spleen architecture. An important goal will be the formation of functional ectopic spleen tissue as an aid to hematopoietic recovery following clinical treatments that impact bone marrow. For example, expansion or replacement of niches could be considered where myeloablation ahead of HSC transplantation compromises treatment outcomes.

Identification of Stromal Cells in Spleen Which Support Myelopoiesis

Stromal cells in spleen organize tissue into red pulp, white pulp and marginal zone, and also interact with hematopoietic cells to regulate immune responses. This study has used phenotypic information of a previously described spleen stromal cell line called 5G3, which supports restricted hematopoiesis in vitro, to identify an equivalent stromal cell subset in vivo and to test its capacity to support hematopoiesis. Using stromal cell fractionation, phenotypic analysis, as well as cell growth and hematopoietic support assays, the Sca-1⁺gp38⁺Thy1.2⁺CD29⁺CD51⁺ fraction of spleen stroma has been identified as an equivalent stromal subset resembling the 5G3 cell counterpart. While heterogeneity may still exist within that subset, it has been shown to have superior hematopoietic support capacity compared with the 5G3 cell line, and all other spleen stromal cell fractions tested.

Bordetella pertussis Whole Cell Immunization, Unlike Acellular Immunization, Mimics Naïve Infection by Driving Hematopoietic Stem and Progenitor Cell Expansion in Mice

Hematopoietic stem and progenitor cell (HSPC) compartments are altered to direct immune responses to infection. Their roles during immunization are not well-described. To elucidate mechanisms for waning immunity following immunization with acellular vaccines (ACVs) against Bordetella pertussis (Bp), we tested the hypothesis that immunization with Bp ACVs and whole cell vaccines (WCVs) differ in directing the HSPC characteristics and immune cell development patterns that ultimately contribute to the types and quantities of cells produced to fight infection. Our data demonstrate that compared to control and ACV-immunized CD-1 mice, immunization with an efficacious WCV drives expansion of hematopoietic multipotent progenitor cells (MPPs), increases circulating white blood cells (WBCs), and alters the size and composition of lymphoid organs. In addition to MPPs, common lymphoid progenitor (CLP) proportions increase in the bone marrow of WCV-immunized mice, while B220⁺ cell proportions decrease. Upon subsequent infection, increases in maturing B cell populations are striking in WCV-immunized mice. RNAseq analyses of HSPCs revealed that WCV and ACV-immunized mice vastly differ in developing VDJ gene segment diversity. Moreover, gene set enrichment analyses demonstrate WCV-immunized mice exhibit unique gene signatures that suggest roles for interferon (IFN) induced gene expression. Also observed in naïve infection, these IFN stimulated gene (ISG) signatures point toward roles in cell survival, cell cycle, autophagy, and antigen processing and presentation. Taken together, these findings underscore the impact of vaccine antigen and adjuvant content on skewing and/or priming HSPC populations for immune response.

Tumor microenvironment in functional adrenocortical adenomas: immune cell infiltration in cortisol-producing adrenocortical adenoma

The tumor microenvironment plays pivotal roles in various human neoplasms. However, that of benign tumor, particularly hormone-secreting endocrine tumors, has remained virtually unknown. Therefore, we firstly attempted to analyze the tumor microenvironment of autonomous hormone-secreting adrenocortical adenomas. We first histologically evaluated 21 cortisol-producing adrenocortical adenoma (CPA) and 13 aldosterone-producing adrenocortical adenoma (APA) cases. Quantitative histologic analysis revealed that intratumoral immune cell infiltration (ICI) was more pronounced in CPAs than in APAs. We then evaluated the cytokine and chemokine profiles using polymerase chain reaction arrays in APAs and CPAs. Angiogenic chemokines, C-X-C motif chemokine ligand (CXCL) 1 and CXCL2, were significantly more abundant in CPAs than in APAs using subsequent quantitative polymerase chain reaction and immunohistochemical analyses. We then examined the vascular density between these 2 adenomas, and the density was significantly higher in overt CPAs than in APAs. Of particular interest, CXCL12-positive vessels were detected predominantly in CPAs, and their infiltrating immune cells were C-X-C motif chemokine receptor 4 (CXCR4) positive. These results above indicated that CXCL12-CXCR4 signaling could partly account for ICI detected predominantly in CPAs. We then further explored the etiology of ICI in CPAs by evaluating the senescence of tumor cells possibly caused by excessive cortisol in CPAs. The status of senescence markers, p16 and p21, was significantly more abundant in CPAs than in APAs. In addition, all CPA cases examined were positive for senescence-associated β-galactosidase. These results all indicated that exposure to local excessive cortisol could result in senescence of tumors cells and play essential roles in constituting the characteristic tissue microenvironment of CPAs.

Evaluation of vascular events in patients with myeloproliferative syndromes and mutations of either the januskinase-2 or calreticulin gene at the university hospital Krems from 2008 to 2015

Myeloproliferative neoplasms (MPN), classified as polycythemia vera (PV), essential thrombocytosis (ET) and myelofibrosis (MF) are stem-cell derived disorders. Mutations in either the januskinase-2 (JAK-2) or the calreticulin (CALR) gene are characteristic for MPN and may result in enhanced proliferation of red blood cells, white blood cells and platelets, and thus increase the risk for vascular events. This study is a retrospective and descriptive analysis of records of patients, who underwent treatment for myeloproliferative syndromes at the Department of Hemato-Oncology of the University hospital Krems from 2008 to the end of 2015. Out of 250 patients, who were suspected for MPN, 51 patients displayed a JAK-2 V617F mutation. These were analyzed with regard to their blood values, gender, age at diagnosis, therapy and vascular events before and after diagnosis (during therapy). Of the 51 patients diagnosed with MPN and a JAK-2 V617F mutation, 33 suffered from PV, 15 from ET and 3 from MF. More men than women were diagnosed with MPN and the median age at diagnosis was 72 years. Acetylsalicylic acid, phlebotomy and Hydroxyurea were the most frequent therapies applied. In our study cohort, the most common vascular events were acute coronary syndrome and transitory ischemic attack. Thromboembolic events were effectively reduced by MPN therapy while no elevation in bleeding events could be observed.

Surgical and immune reconstitution murine models in bone marrow research: Potential for exploring mechanisms in sepsis, trauma and allergy

Bone marrow, the vital organ which maintains lifelong hemopoiesis, currently receives considerable attention, as a source of multiple cell types which may play important roles in repair at distant sites. This emerging function, distinct from, but closely related to, bone marrow roles in innate immunity and inflammation, has been characterized through a number of strategies. However, the use of surgical models in this endeavour has hitherto been limited. Surgical strategies allow the experimenter to predetermine the site, timing, severity and invasiveness of injury; to add or remove aggravating factors (such as infection and defects in immunity) in controlled ways; and to manipulate the context of repair, including reconstitution with selected immune cell subpopulations. This endows surgical models overall with great potential for exploring bone marrow responses to injury, inflammation and infection, and its roles in repair and regeneration. We review three different murine surgical models, which variously combine trauma with infection, antigenic stimulation, or immune reconstitution, thereby illuminating different aspects of the bone marrow response to systemic injury in sepsis, trauma and allergy. They are: (1) cecal ligation and puncture, a versatile model of polymicrobial sepsis; (2) egg white implant, an intriguing model of eosinophilia induced by a combination of trauma and sensitization to insoluble allergen; and (3) ectopic lung tissue transplantation, which allows us to dissect afferent and efferent mechanisms leading to accumulation of hemopoietic cells in the lungs. These models highlight the gain in analytical power provided by the association of surgical and immunological strategies.

Comprehensive selection of reference genes for quantitative RT-PCR analysis of murine extramedullary hematopoiesis during development

The purpose of this study was to perform a comprehensive evaluation and selection of reference genes for the study of extramedullary hematopoiesis during development and the early post-natal period. A total of six candidate reference genes (ACTB, GAPDH, HPRT1, PPID, TBP, TUBB3) in four organs (heart, liver, spleen, and thymus) over five perinatal time points (Embryonic days 14.5, 16.5, 18.5, Post-natal days 0, 21) were evaluated by quantitative real-time PCR. The expression stability of the candidate reference genes were analyzed using geNorm, NormFinder, Bestkeeper, Delta CT method, and RefFinder software packages. Detailed methodology for isolation of high quality/purity RNA and analysis is presented. Detailed analysis demonstrated that TBP is the best single reference gene for embryonic samples and HPRT1 is the best single reference gene for post-natal and pooled embryonic and post-natal samples. Organ-level analysis demonstrated that HPRT1 was the most suitable reference gene for heart, liver and thymus samples, while TBP was the best candidate for spleen samples. In general, TUBB3 was consistently the least stable gene for normalization. This is the first study to describe a systematic comprehensive selection of reference genes for murine extramedullary hematopoietic tissues over a developmental time course. We provide suggested reference genes for individual tissues and developmental stages and propose that a combination of reference genes affords flexibility in experimental design and analysis.

A common complication of myelofibrosis presenting as a rare finding in cerebrospinal fluid cytology

Herein, we present a rare case of intracranial extramedullary hematopoiesis (EMH) diagnosed by cerebrospinal fluid (CSF) cytology and describe the clinical presentation, radiologic, and pathologic findings. A 65 year-old man with a history of progressing primary myelofibrosis was admitted for headaches and right facial numbness. A brain MRI revealed focal abnormalities that were suspicious for leptomeningeal involvement of acute leukemia. Cytologic examination of CSF demonstrated a hypercellular specimen composed of hematopoietic cells including few blasts, as well as maturing red blood cells and granulocytic cells. The integration of morphologic findings, peripheral blood and bone marrow counts, as well as flow cytometric analysis of CSF and bone marrow, excluded leptomeningeal involvement by leukemic blasts and helped establish the diagnosis of intracranial EMH. Inclusion of EMH in the differential diagnosis of intracranial pathology in patients with known conditions predisposing them to EMH is important because recognizing this rare event has implications for treatment and prognosis.