Bone marrow fibrosis: pathophysiology and clinical significance of increased bone marrow stromal fibres

Secondary Bone Marrow Fibrosis in Children And Young Adults: An Institutional Experience

Secondary bone marrow fibrosis (BMF) is associated with many disease conditions in children, but its prevalence and characteristics have not been well elucidated. We present our experience with pediatric secondary BMF, in an attempt to characterize it in terms of underlying diagnoses, severity, and outcome. A retrospective chart review of patients diagnosed with secondary BMF by bone marrow aspirate and biopsy between January 1984 and April 2011 showed a total of 214 patients, the majority (67.1%) of whom had an underlying oncologic disease. At diagnosis, 87 patients (39.7%) had mild, 51 (23.3%) had moderate, and 33 (15.1%) had marked BMF; it was not quantified in 48 (21.9%) patients. An underlying oncologic disease was more frequently associated with marked fibrosis compared with hematologic and miscellaneous diagnoses. Follow-up posttreatment bone marrow aspirate assessments were available for 117 patients. The outcome ranges from worsening of fibrosis to complete resolution. A majority of these children (N=70/117, 60%) showed complete resolution of fibrosis. Of note, 27 patients had marked fibrosis at initial diagnosis and 16 (60%) of them showed complete resolution. These findings underscore the importance of appropriate treatment of the underlying disorder in reversing secondary BMF. Ours is the largest series of pediatric secondary BMF reported.

Thrombopoietin/TGF-β1 Loop Regulates Megakaryocyte Extracellular Matrix Component Synthesis

Extracellular matrix (ECM) components initiate crucial biochemical and biomechanical cues that are required for bone marrow homeostasis. In our research, we prove that a peri-cellular matrix composed primarily of type III and type IV collagens, and fibronectin surrounds human megakaryocytes in the bone marrow. The data we collected support the hypothesis that bone marrow megakaryocytes possess a complete mechanism to synthesize the ECM components, and that thrombopoietin is a pivotal regulator of this new function inducing transforming growth factor-β1 (TGF-β1) release and consequent activation of the downstream pathways, both in vitro and in vivo. This activation results in a dose dependent increase of ECM component synthesis by megakaryocytes, which is reverted upon incubation with JAK and TGF-β1 receptor specific inhibitors. These data are pivotal for understanding the central role of megakaryocytes in creating their own regulatory niche within the bone marrow environment.

High expression of connective tissue growth factor accelerates dissemination of leukaemia

To improve treatment of acute lymphoblastic leukaemia (ALL), a better understanding of disease development is needed to tailor new therapies. Connective tissue growth factor (CTGF/CCN2) is highly expressed in leukaemia cells from the majority of paediatric patients with B-lineage ALL (pre-B ALL). CTGF is a matricellular protein and plays a role in aggressive cancers. Here we have genetically engineered leukaemia cells to modulate CTGF expression levels. Elevated CTGF levels accelerated disease dissemination and reduced survival in NOD/SCID mice. In vitro studies showed that CTGF protein induces stromal cell proliferation, promotes adhesion of leukaemia cells to stromal cells and leads to overexpression of genes associated with cell cycle and synthesis of extracellular matrix (ECM). Corresponding data from our leukaemia xenograft models demonstrated that CTGF leads to increased proliferation of non-leukaemia cells and deposition of ECM in the bone marrow. We document for the first time a functional role of CTGF in altering disease progression in a lymphoid malignancy. The findings provide support for targeting the bone marrow microenvironment in aggressive forms of leukaemia.

Clinical impact of bone marrow morphology for the diagnosis of essential thrombocythemia: comparison between the BCSH and the WHO criteria

Essential thrombocythemia (ET) is currently diagnosed either by the British Committee of Standards in Haematology (BCSH) criteria that are predominantly based on exclusion and not necessarily on bone marrow (BM) morphology, or the World Health Organization (WHO) criteria that require BM examination as essential criterion. We studied the morphological and clinical features in patients diagnosed according either to the BCSH (n=238) or the WHO guidelines (n=232). The BCSH-defined ET cohort was re-evaluated by applying the WHO classification. At presentation, patients of the BCSH group showed significantly higher values of serum lactate dehydrogenase and had palpable splenomegaly more frequently. Following the WHO criteria, the re-evaluation of the BCSH-diagnosed ET cohort displayed a heterogeneous population with 141 (59.2%) ET, 77 (32.4%) prefibrotic primary myelofibrosis (prePMF), 16 (6.7%) polycythemia vera and 4 (1.7%) primary myelofibrosis. Contrasting WHO-confirmed ET, the BCSH cohort revealed a significant worsening of fibrosis-free survival and prognosis. As demonstrated by the clinical data and different outcomes between WHO-diagnosed ET and prePMF, these adverse features were generated by the inadvertent inclusion of prePMF to the BCSH group. Taken together, the diagnosis of ET without a scrutinized examination of BM biopsy specimens will generate a heterogeneous cohort of patients impairing an appropriate clinical management.

Acute Myeloid Leukemia with Isolated Trisomy 19 Associated with Diffuse Myelofibrosis and Osteosclerosis

Primary myelofibrosis (PMF), per WHO criteria, is a clonal myeloproliferative neoplasm that usually presents with a proliferation of granulocytic and megakaryocytic lineages with an associated fibrous deposition and extramedullary hematopoiesis. The bone marrow histologic findings of this disorder are typically characterized by the presence of myeloid metaplasia with an associated reactive fibrosis, angiogenesis, and osteosclerosis. However, marked myelofibrosis is not solely confined to PMF and may also be associated with other conditions including but not limited to acute megakaryoblastic leukemias (FAB AML-M7). Here, we describe a rare case of a non-megakaryoblastic acute myeloid leukemia with marked myelofibrosis with osteosclerosis and an isolated trisomy 19. A 19-year-old male presented with severe bone pain of one week duration with a complete blood cell count and peripheral smear showing a mild anemia and occasional circulating blasts. A follow up computed tomography (CT) scan showed diffuse osteosclerosis with no evidence of hepatosplenomegaly or lymphadenopathy. Subsequently, the bone marrow biopsy showed markedly sclerotic bony trabeculae and a hypercellular marrow with marked fibrosis and intervening sheets of immature myeloid cells consistent with myeloblasts with monocytic differentiation. Importantly, these myeloblasts were negative for megakaryocytic markers (CD61 and vWF), erythroid markers (hemoglobin and E-cadherin), and lymphoid markers (CD3, CD19, and TdT). Metaphase cytogenetics showed an isolated triosomy 19 with no JAK2 V617F mutation. The patient was treated with induction chemotherapy followed by allogenic hematopoietic stem cell transplantation which subsequently resulted in a rapid resolution of bone marrow fibrosis, suggesting graft-anti-fibrosis effect. This is a rare case of a non-megakaryoblastic acute myeloid leukemia with myelofibrosis and osteosclerosis with trisomy 19 that may provide insights into the prognosis and therapeutic options of future cases.

Problems and pitfalls in grading of bone marrow fibrosis, collagen deposition and osteosclerosis - a consensus-based study

AIMS

In the era of potentially disease-modifying agents such as Janus kinase inhibitors, accurate grading and differentiation of bone marrow (BM) fibrosis has become more relevant to assess staging of disease and therapeutic effects. However, different fibrosis grading models have been used in the past without uniformity, including the proposal by the World Health Organization. Current scoring systems are based only on reticulin fibrosis. Therefore, additional assessment of collagen and the grade of osteosclerosis appear to be essential to discriminate all components of the complex BM fibrous matrix.

METHODS AND RESULTS

We evaluated problems and pitfalls regarding staining techniques and the interpretation of reticulin fibrosis on a total of 352 samples. Furthermore, we propose a minor modification of the current grading and separate scoring for collagen deposition and osteosclerosis. Reproducibility of gradings was tested among 11 haematopathologists in a blinded assessment. Overall, the inter-rater reliability of all three grading systems ranged between 0.898 and 0.926.

CONCLUSIONS

A standardized assessment of BM fibrosis with differentiation between reticulin, collagen and osteosclerosis is recommended to evaluate the various components of the fibrous matrix which may be delinked after therapy. In this regard, quality of staining and application of laboratory standards enable a highly reproducible scoring.

Effect of treatment with a JAK2-selective inhibitor, fedratinib, on bone marrow fibrosis in patients with myelofibrosis

Background

Progressive bone marrow fibrosis (BMF) is a cardinal feature of many myeloproliferative neoplasms (MPNs) and there is a documented association between the severity of BMF and overall prognosis. We conducted an exploratory analysis of sequential BMF data from two phase I studies of long-term treatment with the Janus kinase 2 (JAK2) inhibitor fedratinib in patients with myelofibrosis.

Methods

Bone marrow samples were obtained at baseline and after every six cycles (24 weeks) of daily fedratinib treatment. Fibrosis was centrally assessed by three independent haematopathologists, who were blinded to the patients’ data, and graded according to European Consensus Myelofibrosis Grading Criteria. The analysis population comprised patients with a baseline BMF grade ≥1, and at least one post-baseline BMF grade assessment. Changes in BMF grade compared with baseline were classified as improvement (≥1 grade reduction), stabilisation (no change in any baseline BMF grade <3) or worsening (≥1 grade increase).

Results

Twenty-one patients were included in the analysis. A total of 153 bone marrow samples were analysed. Improvement or stabilisation of BMF from baseline was recorded in 15 of 18 (83 %) evaluable patients at cycle 6 and in four of nine (44 %) evaluable patients at cycle 30. Two patients achieved resolution of their BMF (grade = 0) by cycle 12.

Conclusions

This exploratory analysis indicates that improvement or even resolution of BMF may be achievable with JAK2 inhibitor therapy in some patients with MPNs and myelofibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0644-4) contains supplementary material, which is available to authorized users.

Fibrogenesis in Primary Myelofibrosis: Diagnostic, Clinical, and Therapeutic Implications

Primary myelofibrosis is a stem cell-derived clonal malignancy characterized by unchecked proliferation of myeloid cells, resulting in bone marrow fibrosis, osteosclerosis, and pathologic angiogenesis. Bone marrow fibrosis (BMF) plays a central role in the pathophysiology of the disease. This review describes current issues regarding BMF in primary myelofibrosis, including the pathophysiology and impact of abnormal deposition of excess collagen and reticulin fibers in bone marrow spaces, the modified Bauermeister and the European Consensus grading systems of BMF, and the prognostic impact of BMF on the overall outcome of patients with primary myelofibrosis. The impact of novel therapeutic strategies, including JAK-STAT inhibitors and allogeneic stem cell transplant, on BMF is discussed.

Bone geometry, bone mineral density, and micro-architecture in patients with myelofibrosis: a cross-sectional study using DXA, HR-pQCT, and bone turnover markers

Primary myelofibrosis (MF) is a severe chronic myeloproliferative neoplasm, progressing towards a terminal stage with insufficient haematopoiesis and osteosclerotic manifestations. Whilst densitometry studies have showed MF patients to have elevated bone mineral density, data on bone geometry and micro-structure assessed with non-invasive methods are lacking. We measured areal bone mineral density (aBMD) using dual-energy X-ray absorptiometry (DXA). Bone geometry, volumetric BMD, and micro-architecture were measured using high-resolution peripheral quantitative computed tomography (HR-pQCT). We compared the structural parameters of bones by comparing 18 patients with MF and healthy controls matched for age, sex, and height. Blood was analysed for biochemical markers of bone turnover in patients with MF. There were no significant differences in measurements of bone geometry, volumetric bone mineral density, and micro-structure between MF patients and matched controls. Estimated bone stiffness and bone strength were similar between MF patients and controls. The level of pro-collagen type 1 N-terminal pro-peptide (P1NP) was significantly increased in MF, which may indicate extensive collagen synthesis, one of the major diagnostic criteria in MF. We conclude that bone mineral density, geometry, and micro-architecture in this cohort of MF patients are comparable with those in healthy individuals.

The secret life of a megakaryocyte: emerging roles in bone marrow homeostasis control

Megakaryocytes are rare cells found in the bone marrow, responsible for the everyday production and release of millions of platelets into the bloodstream. Since the discovery and cloning, in 1994, of their principal humoral factor, thrombopoietin, and its receptor c-Mpl, many efforts have been directed to define the mechanisms underlying an efficient platelet production. However, more recently different studies have pointed out new roles for megakaryocytes as regulators of bone marrow homeostasis and physiology. In this review we discuss the interaction and the reciprocal regulation of megakaryocytes with the different cellular and extracellular components of the bone marrow environment. Finally, we provide evidence that these processes may concur to the reconstitution of the bone marrow environment after injury and their deregulation may lead to the development of a series of inherited or acquired pathologies.

United Kingdom immune thrombocytopenia registry: retrospective evaluation of bone marrow fibrosis in adult patients with primary immune thrombocytopenia and correlation with clinical findings

Fibrosis has been reported in some patients with immune thrombocytopenia (ITP) treated with thrombopoietin receptor agonists (TPO-RA). However, fibrosis has also been reported in patients with various stages of ITP, who were TPO-RA treatment-naïve. In our study, we looked for fibrosis in bone marrow trephine biopsies taken at initial diagnosis from 32 adult patients with ITP. Ten of the 32 evaluated samples (31·25%) showed increased reticulin (Grade 1-2 on Bauermeister scale and Grade 0-1 on the European Consensus scale), which showed a positive correlation with ethnicity (0·3%) but did not correlate with disease severity, any clinical features or co-morbidities.

Autoimmune Myelofibrosis in Systemic Lupus Erythematosus Report of Two Cases and Review of the Literature

Autoimmune myelofibrosis (AIMF) is a rare entity of steroid-responsive bone marrow fibrosis that accompanies a variety of autoimmune diseases, particularly systemic lupus erythematosus (SLE). Rarely it may occur in patients with autoimmune markers but no definable autoimmune disease (Primary-AIMF). We report the cases of two young women with SLE-associated AIMF (SLE-AIMF). The first patient was a young woman who had pancytopenia, massive splenomegaly and reticulin fibrosis in the marrow biopsy. The pancytopenia and splenomegaly resolved completely within weeks of treatment with corticosteroids. Repeat marrow biopsy showed marked regression of marrow fibrosis. The second patient was a young woman with fever, anasarca, bicytopenia and reticulin fibrosis in the marrow biopsy. Steroid therapy resulted in rapid clinical improvement and resolution of pancytopenia. A review of the literature revealed a total of 30 patients with SLE-AIMF reported to-date. Patients with SLE-AIMF are young women with SLE and blood cytopenia who are found to have increased bone marrow reticulin on marrow biopsy. Steroid therapy results in rapid hematological recovery and regression of marrow fibrosis. Whether AIMF is one of several hematological complications of SLE, or represents a unique and distinct subset of patients with SLE in not clear. Prospective studies with longer follow-up are needed to better define the prevalence and clinical spectrum of SLE-AIMF.

Allo-SCT for myelofibrosis: reversing the chronic phase in the JAK inhibitor era?

At present, allo-SCT is the only curative treatment for patients with myelofibrosis (MF). Unfortunately, a significant proportion of candidate patients are considered transplant ineligible due to their poor general condition and advanced age at the time of diagnosis. The approval of the first JAK inhibitor, ruxolitinib, for patients with advanced MF in 2011 has had a qualified impact on the treatment algorithm. The drug affords substantial improvement in MF-associated symptoms and splenomegaly but no major effect on the natural history. There has, therefore, been considerable support for assessing the drug's candidacy in the peritransplant period. The drug's precise impact on clinical outcome following allo-SCT is currently not known; nor are the drug's long-term efficacy and safety known. Considering the rarity of MF and the small proportion of patients who undergo allo-SCT, well designed collaborative efforts are required. In order to address some of the principal challenges, an expert panel of laboratory and clinical experts in this field was established, and an independent workshop held during the 54th American Society of Hematology Annual Meeting in New Orleans, USA on 6 December 2013, and the European Hematology Association's Annual Meeting in Milan, Italy on 13 June 2014. This document summarizes the results of these efforts.

Quantitative analyses of myelofibrosis by determining hydroxyproline

BACKGROUND

Myeloproliferative neoplasms (MPNs) are blood malignancies manifested in increased production of red blood cells, white blood cells, and/or platelets. Myelofibrosis is a subtype of MPNs characterized by the formation of scar-like tissues in the bone marrow due to abnormal hematopoiesis. It is considered a disease of both hematopoietic stem cells and stem cell niches. Patients with myelofibrosis have very poor prognosis, and there is no effective treatment so far. Myelofibrosis has routinely been detected by using histochemical staining methods which produce qualitative rather than quantitative results. In this study, we developed a quantitative assay of bone marrow myelofibrosis in JAK2V617F transgenic mice by determining hydroxyproline.

METHODS

The JAK2V617F transgenic mice's tissue was collected to detect the bone marrow myelofibrosis. Statistical analyses were performed using the GraphPad Prism program. Differences of samples between two groups were accessed using t tests. P values less than 0.05 (2-tailed) were considered significantly different.

RESULTS

We developed a quantitative method for detecting myelofibrosis by analyzing the content of hydroxyproline, a modified amino acid largely restricted to collagen which forms the fibrotic structure in bone marrow tissues. Our study also demonstrated age-dependent development of bone marrow myelofibrosis in JAK2V617F transgenic mice.

CONCLUSIONS

In the present study, we have developed a new method for detecting bone marrow myelofibrosis by analyzing hydroxyproline contents. The method is highly sensitive and accurate. It provides more accurate, representative, and quantitative information than histochemical analyses. We believe that this method should find wide applications for analyzing the progression of myelofibrosis and efficacy of drug treatment.

Assessment of bone marrow inflammation in patients with myelofibrosis: an 18F-fluorodeoxyglucose PET/CT study

PURPOSE

Myelofibrosis is a haematopoietic stem cell neoplasm characterized by bone marrow inflammation, reactive marrow fibrosis and extramedullary haematopoiesis. The aim of this study was to determine if (18)F-FDG PET/CT can be used to noninvasively visualize and quantify the extent and activity of bone marrow involvement.

METHODS

In 30 patients, the biodistribution of (18)F-FDG was analysed by measuring the standardized uptake value in the bone marrow compartment and spleen. Imaging findings were compared with laboratory, cytogenetic and histopathological data.

RESULTS

Retention of (18)F-FDG was observed in bone marrow and spleen. Bone marrow involvement varied, ranging from mildly increased uptake in the central skeleton to extensive uptake in most parts of the skeleton. The extent of bone marrow involvement decreased over time from initial diagnosis (r s  = -0.43, p = 0.019). Metabolic activity of the bone marrow decreased as the histopathological grade of fibrosis increased (r s  = -0.37, p = 0.04). There was a significant positive correlation between the metabolic activity of the bone marrow and that of the spleen (p = 0.04).

CONCLUSION

(18)F-FDG PET/CT is as a promising technique for the quantitation of bone marrow inflammation in myelofibrosis. Our data indicate that the intensity of bone marrow (18)F-FDG uptake decreases as bone marrow fibrosis increases. Further evaluation in prospective studies is required to determine the potential clinical impact and prognostic significance of PET.

High concordance in grading reticulin fibrosis and cellularity in patients with myeloproliferative neoplasms

The myeloproliferative neoplasms primary myelofibrosis, polycythemia vera, and, rarely, essential thrombocythemia are characterized by variable degrees of bone marrow fibrosis, either at presentation or upon progression. The increasing use of emerging therapies that may alter disease biology and morphology demands accurate and reproducible assessment of fibrosis grade. To assess concordance of hematopoietic cellularity and fibrosis grading, three hematopathologists independently evaluated a total of 728 bone marrow biopsies from 261 patients with myeloproliferative neoplasms on three clinical trials using fedratinib (SAR302503), a JAK2 inhibitor, including 249 taken at baseline and 479 on therapy. Concordance between the pathologists was evaluated by Pearson correlation coefficient (cellularity) and unweighted kappa statistic (fibrosis grade). There was high correlation of cellularity assessment (r=0.92) and fibrosis grading (kappa=0.83) between the three pathologists. Concordance with World Health Organization (WHO) grade 3 samples was higher compared with grades 0, 1, and 2. Concordance of fibrosis grading in pretreatment samples was superior to that of post-treatment samples (kappa=0.83 and 0.79, respectively, P=0.023). Our analysis suggests that the updated 2008 WHO reticulin fibrosis grading system is highly reproducible, even in patients undergoing JAK2 inhibitor therapy. This system is practically applicable to establish baseline fibrosis grade as well as changes in fibrosis in subsequent samples on therapy.

To evaluate the role of bone marrow aspiration and bone marrow biopsy in pancytopenia

BACKGROUND

Pancytopenia is not a disease entity but a triad of findings that may result from various disease processes, primarily or secondarily involving the bone marrow. Bone marrow aspiration and biopsy evaluation along with good clinical correlation is of utmost importance to evaluate the causes of pancytopenia and planning further investigations.

AIMS

The present study was a prospective clinicohaematological study undertaken to analyse the various causes of pancytopenia by evaluating bone marrow aspiration and biopsy and correlating with clinical findings, complete blood counts and peripheral blood picture.

MATERIALS AND METHODS

Fifty patients of pancytopenia were included in the study in which relevant history and physical examination findings were recorded. Bone marrow aspiration and biopsy were performed simultaneously in all cases. Perl's stain was done in all cases and special stains like MPO, PAS and reticulin were also done wherever necessary.

RESULTS AND CONCLUSION

The maximum cases of pancytopenia were in the age group of 10 to 30 y with male preponderance. Aplastic anaemia was found to be the most common aetiology of pancytopenia followed by normoblastic erythroid hyperplasia, megaloblastic anaemia, acute leukemias, myelofibrosis, lymphoid neoplasia and iron deficiency anaemia. It was concluded from the study that although the advantages of bone marrow aspiration and biopsy differ, both are complimentary to each other and should be performed simultaneously for a complete bone marrow work up and evaluation. It is only through the correlation of clinical, hematological and bone marrow examination findings that proper evaluation and management of patients of pancytopenia can be made.

Tissue-nonspecific alkaline phosphatase deficiency causes abnormal craniofacial bone development in the Alpl(-/-) mouse model of infantile hypophosphatasia

Tissue-nonspecific alkaline phosphatase (TNAP) is an enzyme present on the surface of mineralizing cells and their derived matrix vesicles that promotes hydroxyapatite crystal growth. Hypophosphatasia (HPP) is an inborn-error-of-metabolism that, dependent upon age of onset, features rickets or osteomalacia due to loss-of function mutations in the gene (Alpl) encoding TNAP. Craniosynostosis is prevalent in infants with HPP and other forms of rachitic disease but how craniosynostosis develops in these disorders is unknown.

OBJECTIVES

Because craniosynostosis carries high morbidity, we are investigating craniofacial skeletal abnormalities in Alpl(-/-) mice to establish these mice as a model of HPP-associated craniosynostosis and determine mechanisms by which TNAP influences craniofacial skeletal development.

METHODS

Cranial bone, cranial suture and cranial base abnormalities were analyzed by micro-CT and histology. Craniofacial shape abnormalities were quantified using digital calipers. TNAP expression was suppressed in MC3T3E1(C4) calvarial cells by TNAP-specific shRNA. Cells were analyzed for changes in mineralization, gene expression, proliferation, apoptosis, matrix deposition and cell adhesion.

RESULTS

Alpl(-/-) mice feature craniofacial shape abnormalities suggestive of limited anterior-posterior growth. Craniosynostosis in the form of bony coronal suture fusion is present by three weeks after birth. Alpl(-/-) mice also exhibit marked histologic abnormalities of calvarial bones and the cranial base involving growth plates, cortical and trabecular bone within two weeks of birth. Analysis of calvarial cells in which TNAP expression was suppressed by shRNA indicates that TNAP deficiency promotes aberrant osteoblastic gene expression, diminished matrix deposition, diminished proliferation, increased apoptosis and increased cell adhesion.

CONCLUSIONS

These findings demonstrate that Alpl(-/-) mice exhibit a craniofacial skeletal phenotype similar to that seen in infants with HPP, including true bony craniosynostosis in the context of severely diminished bone mineralization. Future studies will be required to determine if TNAP deficiency and other forms of rickets promote craniosynostosis directly through abnormal calvarial cell behavior, or indirectly due to deficient growth of the cranial base.

Increased angiogenesis in primary myelofibrosis: latent transforming growth factor-β as a possible angiogenic factor

Objective

The aim of this work was to demonstrate a possible relationship between anti-latency-associated peptide human latent transforming growth factor beta 1 (latent TGF-β1) expression in megakaryocytes and microvascular density in bone marrow biopsies from patients with essential thrombocythemia and primary myelofibrosis.

Methods

Microvascular density was evaluated by immunohistochemical analysis and the expression of latent TGF-β1 in samples (100 megakaryocytes per bone marrow sample) from 18 essential thrombocythemia and 38 primary myelofibrosis (19 prefibrotic and 19 fibrotic) patients. Six bone marrow donor biopsies were used as controls. Fibrosis in the bone marrow biopsies was evaluated according to the European Consensus.

Results

The average fibrosis grade differed between essential thrombocythemia and primary myelofibrosis groups when compared to the control group. Latent TGF-β1 expression differed significantly between the fibrotic primary myelofibrosis (PMF) group and the control group (p-value < 0.01). A high degree of neo-angiogenesis (demonstrated by analysis of CD34 expression) was detected in patients with myelofibrosis. There were correlations between latent TGF-β1 expression and microvascular density (r = 0.45; p-value < 0.0009) and between degree of microvascular density and fibrosis grade (r = 0.80; p-value < 0.0001). Remarkable differences for neo-angiogenesis were not observed between patients with essential thrombocythemia and controls.

Conclusion

Angiogenesis participates in the pathogenesis of primary myelofibrosis, in both the prefibrotic and fibrotic stages, while latent TGF-β is differentially expressed only in the prefibrotic stage.

Bone marrow fibrosis as a feature of systemic lupus erythematosus: a case report and literature review

Introduction

Peripheral cytopenias are common in systemic lupus erythematosus (SLE), but bone marrow involvement is rarely reported. Myelofibrosis is a rare disorder characterized by reticulin fibrosis of the bone marrow, which usually occurs in response to clonal proliferation of hematopoietic stem cells in myeloproliferative disorders. However, bone marrow fibrosis has also been described in association with auto-immune diseases, especially SLE.

Method

We will report here a new case of bone marrow fibrosis associated with SLE. We also reviewed the 27 cases published in the English language literature, and will discuss the clinical presentation, outcome, treatment, and pathophysiology of bone marrow fibrosis occurring in association with SLE.

Results

Over one half of patients were diagnosed concomitantly with bone marrow fibrosis and SLE. Epidemiological, clinical and biological features of lupus were unremarkable. Except for the presence of reticulin fibrosis, the findings from the bone marrow biopsies proved highly variable. Overall mortality was about 14% but corticosteroid-based therapy lead to clinical improvement and reverted bone marrow fibrosis in most cases. Data on the usefulness of other immunomodulatory therapies are inconclusive.

Conclusions

SLE may be complicated by bone marrow involvement, of a likely autoimmune origin. Bone marrow fibrosis occurring with SLE is probably similar to “primary autoimmune myelofibrosis” and may respond to steroid and immunomodulatory therapies. Further studies with standardised proofreading of bone marrow aspirations and biopsies are needed to delineate the clinical and biological features of this rare complication of SLE.

Bone marrow-derived vascular modulatory cells in pulmonary arterial hypertension

Hematopoiesis and vascular homeostasis are closely linked to each other via subsets of circulating bone marrow-derived cells with potent activity to repair endothelial injury and promote angiogenesis. As a consequence, abnormalities in hematopoiesis will eventually affect vascular health. Pulmonary arterial hypertension (PAH) is a vascular disease characterized by severe remodeling of the pulmonary artery wall. Over the past decade, circulating hematopoietic cells have been assigned an increasing role in the remodeling, such that these cells have been used in new therapeutic strategies. More recently, research has been extended to the bone marrow where these cells originate to identify abnormalities in hematopoiesis that may underlie PAH. Here, we review the current literature and identify gaps in knowledge of the myeloid effects on PAH.

WHO classification of myeloproliferative neoplasms (MPN): A critical update

Although the revised World Health Organization (WHO) criteria for the diagnosis and classification of myeloproliferative neoplasms (MPN) were defined by a panel of expert hematopathologists and clinicians, controversy has been repeatedly expressed questioning the clinical usefulness and reproducibility of these diagnostic guidelines. In particular, the distinction between essential thrombocythemia (ET), early/prefibrotic primary myelofibrosis (PMF) and initial stages of polycythemia vera (PV) is still a matter of debate. In this context, it has been argued that clinical correlations with histological features were not firmly substantiated. On the other hand, recently published data from independently performed studies have repeatedly validated the reproducibility of the WHO criteria and provided persuasive evidence that discrimination of early/prefibrotic PMF has a significant impact on the risk of myelofibrotic and leukemic transformation. However, as has been explicitly required, the WHO concept is based on the recognition of characteristic bone marrow patterns and a consensus of clinical and molecular data.

Image analysis of platelet derived growth factor receptor-beta (PDGFRβ) expression to determine the grade and dynamics of myelofibrosis in bone marrow biopsy samples

BACKGROUND

Myelofibrosis (MF) is characterized by accumulation of stromal cells and extracellular matrix. Progression of fibrosis is an important clinical issue and monitoring is required for new therapeutic approaches. Currently, the quantification is based on semiquantitative evaluation of reticulin silver stained slides. We recently reported that platelet derived growth factor receptor beta (PDGFRβ) expression in fibroblasts is a useful marker of stromal activation. PDGFRβ expression based scores represent significant differences in different MF grade which provides optimal source of quantification. In this study, slide-based measurements were performed to support correlations of PDGFRβ expression with MF grade.

METHODS

Scanned image tiles from 79 bone marrow samples (BM) with different MF grades were evaluated for PDGFRβ-related IHC parameters. Following the determination of immunopositive (brown component) and total area (region of interest) of the BM, PDGFRβ related image parameters were defined and evaluated in comparison with the classical reticulin based grading.

RESULTS

Eight PDGFRβ expression related image parameters showed excellent correlation with the MF grade (correlation coefficient ranging between 0.79 and 0.83) and with PDGFRβ score (0.76-0.87). Despite the significant sample heterogeneity, the parameters showed significant differences between fibrotic and nonfibrotic cases and between mild and advanced fibrosis. Distribution of values within a particular specimen emphasizes the heterogeneity of bone marrow involvement which may cause difficulties in semiquantitative methods.

CONCLUSIONS

Our results clearly demonstrated the correlation between MF and PDGFRβ expression considering all relevant areas in BM samples. This method provides good basis for follow-up comparison of the fibrotic samples.

Toll-like receptor 7-stimulated tumor necrosis factor α causes bone marrow damage in systemic lupus erythematosus

OBJECTIVE

To define the pathogenesis of bone marrow (BM) involvement in systemic lupus erythematosus (SLE).

METHODS

Tumor necrosis factor α (TNFα) levels, cell death, and cellular damage in BM from SLE patients, controls, and mice with pristane-induced lupus were analyzed using a morphometric technique and immunohistochemistry. The pathogenesis of BM abnormalities was studied in wild-type (WT), TNFα(-/-) , Toll-like receptor-deficient (TLR-7(-/-) ), interferon (IFN)-α/β/ω receptor-knockout (IFNAR(-/-) ), and B cell-deficient (μmt) mice treated with pristane. Flow cytometry was used to examine TNFα production (by intracellular staining) and plasma cell/plasmablast development. CXCL12 expression was determined by quantitative polymerase chain reaction.

RESULTS

BM from SLE patients exhibited striking death of niche and hematopoietic cells associated with TNFα overproduction. BM from mice with a type I IFN-mediated lupus syndrome induced by pristane showed similar abnormalities. TNFα was produced mainly by BM neutrophils, many with phagocytosed nuclear material (lupus erythematosus cells). TNFα production was abolished in pristane-treated TLR-7(-/-) and μmt mice but was restored in μmt mice by infusing normal plasma. Pristane-treated WT and IFNAR(-/-) mice developed anemia, BM hypocellularity, and extramedullary hematopoiesis, which were absent in TLR-7(-/-) and TNFα(-/-) mice. Additionally, the expression of CXCL12, which is produced by stromal cells and mediates homing of hematopoietic cells and plasmablasts, was decreased in BM from pristane-treated WT mice but was normal in BM from pristane-treated TNFα(-/-) mice.

CONCLUSION

Although autoantibodies and glomerulonephritis are type I IFN dependent, lupus-associated BM abnormalities were TLR-7 and TNFα driven but type I IFN independent, suggesting that lupus is a disorder of innate immunity in which TLR-7 activation by phagocytosed nuclei causes relentless type I IFN and TNFα production mediating glomerulonephritis and hematologic involvement, respectively.

[Pathomechanism and clinical impact of myelofibrosis in neoplastic diseases of the bone marrow]

Polyclonal mesenchymal cells (fibroblasts, endothelial cells, pericytes, osteoblasts, reticular cells, adipocytes, etc.) of the bone marrow create a functional microenvironment, which actively contributes to the maintenance of hemopoesis. This takes place through cellular interactions via growth factors, cytokines, adhesion molecules and extracellular matrix components, as well as through the control of calcium and oxygen concentration. Inflammatory and neoplastic diseases of the bone marrow result in pathologic interaction between hemopoietic progenitors and stromal cells. This may lead to the activation and expansion of the stroma and to the accumulation of reticulin and collagen fibers produced by mesenchymal cells. Clinically relevant fiber accumulation, termed as myelofibrosis accompanies many diseases, although, the extent and the consequence of myelofibrosis are variable in different disorders. The aim of this review is to summarize basic features of the normal bone marrow mesenchymal environment and the pathological process leading to myelofibrosis. In addition, the special features of myelofibrosis in bone marrow diseases, including myeloproliferative neoplasia, myelodysplastic syndrome and other neoplastic conditions are discussed.

Thrombopoietin from beginning to end

In the two decades since its cloning, thrombopoietin (TPO) has emerged not only as a critical haematopoietic cytokine, but also serves as a great example of bench-to-bedside research. Thrombopoietin, produced by the liver, is the primary regulator of megakaryocyte progenitor expansion and differentiation. Additionally, as TPO is vital for the maintenance of haematopoietic stem cells, it can truly be described as a pan-haematopoietic cytokine. Since recombinant TPO became available, the molecular mechanisms of TPO function have been the subject of extensive research. Via its receptor, c-Mpl (also termed MPL), TPO activates a wide array of downstream signalling pathways, promoting cellular survival and proliferation. Due to its central, non-redundant role in haematopoiesis, alterations of both the hormone and its receptor contribute to human disease; congenital and acquired states of thrombocytosis and thrombocytopenia and aplastic anaemia as a result from dysregulated TPO expression or functional alterations of c-Mpl. With TPO mimetics now in clinical use, the story of this haematopoietic cytokine represents a great success for biomedical research.

Bone marrow fibrosis in 66 patients with immune thrombocytopenia treated with thrombopoietin-receptor agonists: a single-center, long-term follow-up

Thrombopoietin-receptor agonists increase platelet counts by stimulating the thrombopoietin receptor. Bone marrow fibrosis has been reported in patients receiving thrombopoietin-receptor agonists. This study determined the extent of myelofibrosis, its clinical relevance, and incidence of phenotypic or karyotypic abnormalities in patients with immune thrombocytopenia treated with thrombopoietin-receptor agonists. The grade of myelofibrosis was assessed before (n=15), during (n=117) and after (n=9) treatment in bone marrow biopsies from 66 patients. The proportion of bone marrow biopsies showing no fibrosis (myelofibrosis grade 0) decreased from 67% pre-treatment to 22% at last biopsy, of which 59% had grade 1 myelofibrosis and 18% had grade 2 myelofibrosis. The median duration of treatment with thrombopoietin-receptor agonists to last bone marrow biopsies was 29 months; patients who had two or more biopsies significantly more frequently had myelofibrosis grades 2/3 in the last bone marrow biopsies as compared to the first. Older age was associated with higher grades of fibrosis. No differences in blood counts or lactate dehydrogenase levels were found between patients with myelofibrosis grades 0/1 and those with grade 2. No clonal karyotypic or immunophenotypic abnormalities emerged. This study found that thrombopoietin-receptor agonists induce myelofibrosis grades 2/3 in approximately one-fifth of patients with immune thrombocytopenia, increasingly with >2 years of treatment with thrombopoietin-receptor agonists. Annual/biannual follow-up with bone marrow biopsies is, therefore, recommended in patients being treated with thrombopoietin-receptor agonists in order to enable prompt discontinuation of these drugs should grades 2/3 myelofibrosis develop. Discontinuation of thrombopoietin-receptor agonists may prevent development of clinical manifestations by stopping progression of fibrosis in grade 2/3.

[Primary myelofibrosis--pathogenesis, diagnosis and treatment]

BACKGROUND

Primary myelofibrosis is a malignant myeloproliferative disease. It is characterised by proliferation of megakaryocytes in the bone marrow, dysregulated cytokine production and reactive fibrosis that causes bone marrow failure. The purpose of this article is to provide an up-to-date presentation of the pathophysiology, diagnostics and treatment of the disease.

METHOD

The article is based on the authors' own experience and on a selection of articles identified through many years of experience of treating patients with myelofibrosis.

RESULTS

The molecular mechanisms that trigger the disease remain unidentified, but mutations in two genes (JAK2 and MPL) occur in 70% of patients and result in increased production of haematopoietic cells. Diagnosis is based on clinical examination, bone marrow histology and molecular biological examinations. The clinical course of primary myelofibrosis varies. Life expectancy depends on a number of factors and is severely decreased by high-risk disease. Allogeneic stem cell transplantation is the only treatment with a curative potential, but only a minority of patients are eligible for it. If transplantation is not possible, therapy is symptomatic. JAK2-inhibitors are new drugs that counteract cytokine production and cell proliferation. Ruxolitinib is the first approved JAK2 inhibitor and has proved effective on symptoms and quality of life.

INTERPRETATION

Medical inhibition of the JAK2 gene and associated JAK-STAT signalling pathway is a step forward in treatment. However, stem cell transplantation remains the only potentially curative treatment for myelofibrosis.

Active thrombopoiesis is associated with worse severity and activity of chronic GVHD

Chronic GVHD (cGVHD) is a major complication of allogeneic hematopoietic SCT. Post transplant thrombocytopenia in patients with cGVHD has been associated with poor outcome and its etiology is unclear. We investigated whether thrombopoiesis, assessed via measurement of the absolute immature platelet number (AIPN) in the blood, is impaired in cGVHD, and whether the level of thrombopoiesis correlates with the severity and activity of cGVHD as assessed via the National Institutes of Health (NIH) organ scoring system. We used a cohort of 110 well-characterized cGVHD patients, including 83 (75%) with severe cGVHD per NIH global score. Higher AIPN was associated with active therapeutic intent (P=0.026), lower Karnofsky score (P=0.0013), worse joint/fascia cGVHD (P=0.0005) and worse skin cGVHD (P=0.0044). AIPN correlated with platelet counts and was not correlated with ANC, WBC, C-reactive protein (CRP), absolute lymphocyte count (ALC), albumin, total and average NIH scores, or number of prior systemic therapies. AIPN values for cGVHD patients substantially overlapped those of the normal population. Higher AIPN, as marker of active thrombopoiesisis, was associated with worse severity and activity of cGVHD, especially skin and joints/fascia manifestations. Among patients with stable moderate or severe cGVHD, there was no evidence of hypoproduction of platelets. Future studies should further investigate the role of thrombopoiesis in cGVHD.

Differential diagnosis of myelofibrosis based on WHO 2008 criteria: acute panmyelosis with myelofibrosis, acute megakaryoblastic leukemia with myelofibrosis, primary myelofibrosis and myelodysplastic syndrome with myelofibrosis

INTRODUCTION

The aim of this study was to characterize clinicopathological features of acute panmyelosis with myelofibrosis (APMF), acute megakaryoblastic leukemia with myelofibrosis (AMKL-MF), primary myelofibrosis (PMF) and myelodysplastic syndrome with myelofibrosis (MDS-MF) in order to provide the keys to the differential diagnosis of bone marrow (BM) fibrosis.

METHODS

We compared age, gender, splenomegaly, serum lactate dehydrogenase level, blood cell counts, blast counts in peripheral blood (PB) and BM, megakaryocyte counts, BM cellularity, dysplasia, and the karyotypes of patients with APMF (n = 6), AMKL-MF (n = 7), PMF (n = 44), and MDS-MF (n = 44).

RESULTS

APMF showed hyperplasia of all three lineages, increase in megakaryocyte count with dysplasia and frequent abnormal karyotypes. AMKL-MF was associated with elevated BM blast counts, decreased BM megakaryocyte count with rare megakaryocytic dysplasia and chromosome 21 abnormality. PMF patients displayed splenomegaly, rare blasts in PB/BM, and JAK2 V617F mutation. MDS-MF patients showed pancytopenia, dysplasia in all three lineages and recurrent chromosomal abnormalities involving chromosome 5,7,12, and 17.

CONCLUSIONS

Although differential diagnosis among APMF, AMKL-MF, PMF, and MDS-MF is very challenging due to the overlapping clinical and morphological features, meticulous investigation of the patient with respect to splenomegaly, blood cell count, PB and BM findings, and karyotype will serve as a guide to correct diagnosis.

The efficacy and safety of romiplostim in adult patients with chronic immune thrombocytopenia

Romiplostim is a thrombopoietin peptide mimetic agent recently approved for the treatment of adults with chronic immune thrombocytopenia (ITP). In randomized controlled studies, this agent has demonstrated an increase in the platelet count in the majority of patients with ITP, both in splenectomized and nonsplenectomized patients. In up to 5 years of follow up, its safety profile has been favorable, suggesting this could be a novel therapeutic agent in patients with ITP. This article summarizes the development of this new agent and explores its safety and efficacy in adults with chronic ITP.

Bone marrow fibrosis and metastatic prostate adenocarcinoma

A 52-year-old man presented to the outpatient department with breathlessness and generalised weakness since 2 months. He was found to have anaemia and thrombocytopenia. A complete haematological workup failed to point towards a definite aetiology. Bone marrow biopsy revealed fibrosis with predominantly collagen fibres. An elevated prostate-specific antigen level and CT scan of the abdomen and pelvis suggested prostate carcinoma, which prompted a transrectal ultrasound-guided biopsy, revealing a poorly differentiated adenocarcinoma of the prostate.

Safety and efficacy of eltrombopag for treatment of chronic immune thrombocytopenia: results of the long-term, open-label EXTEND study

Patients with chronic immune thrombocytopenia may have bleeding resulting from low platelet counts. Eltrombopag increases and maintains hemostatic platelet counts; however, to date, outcome has been reported only for treatment lasting ≤ 6 months. This interim analysis of the ongoing open-label EXTEND (Eltrombopag eXTENded Dosing) study evaluates the safety and efficacy of eltrombopag in 299 patients treated up to 3 years. Splenectomized and nonsplenectomized patients achieved platelets ≥ 50 000/μL at least once (80% and 88%, respectively). Platelets ≥ 50 000/μL and 2 × baseline were maintained for a median of 73 of 104 and 109 of 156 cumulative study weeks, respectively. Bleeding symptoms (World Health Organization Grades 1-4) decreased from 56% of patients at baseline to 20% at 2 years and 11% at 3 years. One hundred (33%) patients were receiving concomitant treatments at study entry, 69 of whom attempted to reduce them; 65% (45 of 69) had a sustained reduction or permanently stopped ≥ 1 concomitant treatment. Thirty-eight patients (13%) experienced ≥ 1 adverse events leading to study withdrawal, including patients meeting protocol-defined withdrawal criteria (11 [4%] thromboembolic events, 5 [2%] exceeding liver enzyme thresholds). No new or increased incidence of safety issues was identified. Long-term treatment with eltrombopag was generally safe, well tolerated, and effective in maintaining platelet counts in the desired range.

Oxidases and reactive oxygen species during hematopoiesis: a focus on megakaryocytes

Reactive oxygen species (ROS), generated as a result of various reactions, control an array of cellular processes. The role of ROS during megakaryocyte (MK) development has been a subject of interest and research. The bone marrow niche is a site of MK differentiation and maturation. In this environment, a gradient of oxygen tension, from normoxia to hypoxia results in different levels of ROS, impacting cellular physiology. This article provides an overview of major sources of ROS, their implication in different signaling pathways, and their effect on cellular physiology, with a focus on megakaryopoiesis. The importance of ROS-generating oxidases in MK biology and pathology, including myelofibrosis, is also described.

The European Consensus on grading of bone marrow fibrosis allows a better prognostication of patients with primary myelofibrosis

We investigated the relationship between the International Prognostic Scoring System of the International Working Group for Myelofibrosis Research and Treatment and the European Consensus on grading of bone marrow fibrosis (MF) in patients with primary myelofibrosis. We compared them in 196 consecutive primary myelofibrosis patients (median follow-up 45.7 months; range 7.4-159). International Prognostic Scoring System classified 42 cases as low risk, 73 as intermediate risk-1, 69 as intermediate risk-2, and 12 as high risk; European Consensus on grading of bone marrow fibrosis classified 83 cases as MF-0, 58 as MF-1, 41 as MF-2, and 14 as MF-3. By the time of the analysis, 30 patients (15.3%) had died. Overall median survival was 3.8 years (95% confidence interval: 3.3-4.3). Multivariate analysis confirmed that both scoring systems independently predicted survival, with hazard ratios similar to those provided by univariate analysis (respectively, 2.40 (95% confidence interval: 1.47-3.91) and 2.58 (95% confidence interval: 1.72-3.89) but the likelihood ratio increased from 19.6 of the International Prognostic Scoring System or 29.0 of the European Consensus on grading of bone MF to 42.3 when both measures were considered together. Analysis of the overall survival curves documented that patients classified as having the most favourable rate with both prognostic scores (ie low risk and MF-0) survive longer than those with only one favourable score (ie low risk but MF >0 or MF-0, but International Prognostic Scoring System >low risk). In contrast, those patients classified as having the most unfavourable rate for both scores (high risk and MF-3) have a shorter survival than those with only one unfavourable score (ie high risk but MF<3 or MF-3, but International Prognostic Scoring System <high risk). In conclusion, our analysis suggests that better prognostication can be achieved in primary myelofibrosis patients when both systems are used together.

Megakaryocyte pathology and bone marrow fibrosis: the lysyl oxidase connection

Megakaryocytes (MKs), the platelet precursors, are capable of accumulating DNA greater than a diploid content as part of their cell cycle. MKs have been recognized as mediating fibrosis in a subset of hematologic malignancies, including acute megakaryoblastic leukemia and a subset of myeloproliferative neoplasms. The mechanisms responsible for fibrosis remain only partially understood. Past studies highlighted the role of growth factors in such pathologies, and recently, the protein lysyl oxidase (LOX) has been implicated in proliferation of MKs, ploidy and deposition of fibers. LOX was initially characterized as a protein responsible for the intermolecular cross-linking of elastin and collagen, and in recent years it has been identified as regulator of various pathologies, such as cancer and inflammation. Here, we review recent advances in the understanding of the contribution of MKs to the progression of myelofibrosis, highlighting the newly identified role of LOX.

Assessment of bone marrow fibrosis and angiogenesis in monitoring patients with multiple myeloma

The aim of our study was to emphasize the importance of accurate and standardized techniques for detailed monitoring of the microenvironment in multiple myeloma (MM). Bone marrow fibrosis, angiogenesis, and plasma cell infiltrates in bone marrow biopsy (BMB) samples at the time of diagnosis and on completion of therapy were analyzed for 42 patients with newly diagnosed MM. Computerized image analysis was used for all slides stained with anti-CD138 and anti-CD34. The patients with fibrosis in pretreatment BMB samples had significantly higher microvessel density (MVD) and plasma cell infiltrates. In posttreatment BMB samples, nonresponders had a significantly higher frequency and grade of fibrosis and higher values of MVD, total vascular area, and plasma cell percentage. The overall survival of nonresponders and patients with increased marrow fibrosis in posttreatment BMB samples was significantly shorter. The obtained results confirm that complex morphologic examination of the bone marrow microenvironment during the monitoring of MM can provide better prognostic significance.