Vascular Permeability and Remodelling Coincide with Inflammatory and Reparative Processes after Joint Bleeding in Factor VIII-Deficient Mice

Aberrant methylation and expression of TNXB promote chondrocyte apoptosis and extracullar matrix degradation in hemophilic arthropathy via AKT signaling

Recurrent joint bleeding in hemophilia patients frequently causes hemophilic arthropathy (HA). Drastic degradation of cartilage is a major characteristic of HA, but its pathological mechanisms has not yet been clarified. In HA cartilages, we found server matrix degradation and increased expression of DNA methyltransferase proteins. We thus performed genome-wide DNA methylation analysis on human HA (N=5) and osteoarthritis (OA) (N=5) articular cartilages, and identified 1228 differentially methylated regions (DMRs) associated with HA. Functional enrichment analyses revealed the association between DMR genes (DMGs) and extracellular matrix (ECM) organization. Among these DMGs, Tenascin XB (TNXB) expression was down-regulated in human and mouse HA cartilages. The loss of Tnxb in F8-/- mouse cartilage provided a disease-promoting role in HA by augmenting cartilage degeneration and subchondral bone loss. Tnxb knockdown also promoted chondrocyte apoptosis and inhibited phosphorylation of AKT. Importantly, AKT agonist showed chondroprotective effects following Tnxb knockdown. Together, our findings indicate that exposure of cartilage to blood leads to alterations in DNA methylation, which is functionally related to ECM homeostasis, and further demonstrate a critical role of TNXB in HA cartilage degeneration by activating AKT signaling. These mechanistic insights allow development of potentially new strategies for HA cartilage protection.

Evaluation of collagen turnover biomarkers as an objective measure for efficacy of treatment with rurioctocog alfa pegol in patients with hemophilia A: a secondary analysis of a randomized controlled trial

BACKGROUND

Patients with hemophilia who have recurrent hemarthroses develop hemophilic arthropathy (HA). Regular prophylaxis with factor (F) VIII (FVIII) can reduce HA, but there is a need for objective outcome measures to evaluate treatment efficacy.

OBJECTIVES

Evaluate and assess collagen turnover biomarkers in patients with hemophilia A to determine the efficacy of rurioctocog alfa pegol treatment and understand their potential as tools for guiding treatment decisions and monitoring outcomes.

METHODS

Joint remodeling was assessed by analyzing serum levels of collagen remodeling products at baseline and months 3, 6, 9, and 12 in a 98 patient subset receiving pharmacokinetics-guided prophylaxis with rurioctocog alfa pegol, targeting FVIII trough levels of 1 to 3 International Units (IU)/dL or 8 to 12 IU/dL (PROPEL study, NCT0285960).

RESULTS

Basement membrane metabolism-related type 4 collagen remodeling products (C4M and PRO-C4) decreased after 3 months at all time points by up to 25% at 1 to 3 IU/dL (P = .049, P < .0001) and 8 to 12 IU/dL FVIII trough levels (P = .0002, P < .0001). Interstitial tissue metabolism-related type 3 (C3M) and 5 (PRO-C5) collagen remodeling products decreased after 3 months, by up to 19% at 1 to 3 IU/dL FVIII trough level (P = .0001, P = .009) and 23% at 8 to 12 IU/dL FVIII trough level (P = .0002, P = .001). An increase of up to 12% was seen for cartilage metabolism-related type 2 collagen product (PRO-C2, not C2M) after 6 months at both trough levels (P = .01, P = .005). When stratified by prior treatment, changes in C3M (P = .03) and C4M (P = .02) levels were observed between trough levels for prior on-demand treatment but not for prophylaxis prior to study entry.

CONCLUSION

Joint improvement measured by collagen remodeling biomarkers specific to the basement membrane, interstitial matrix, and cartilage was seen with pharmacokinetics-guided prophylaxis. These collagen remodeling biomarkers warrant further exploration as biomarkers to guide treatment toward improvement in HA.

Maladaptive lymphangiogenesis is associated with synovial iron accumulation and delayed clearance in factor VIII-deficient mice after induced hemarthrosis

BACKGROUND

Mechanisms of iron clearance from hemophilic joints are unknown.

OBJECTIVES

To better understand mechanisms of iron clearance following joint bleeding in a mouse model of hemophilia.

METHODS

Hemarthrosis was induced by subpatellar puncture in factor VIII (FVIII)-deficient (FVII-/-) mice, +/- periprocedural recombinant human FVIII, and hypocoagulable (HypoBALB/c) mice. HypoBALB/c mice experienced transient FVIII deficiency (anti-FVIII antibody) at the time of injury combined with warfarin-induced hypocoagulability. Synovial tissue was harvested weekly up to 6 weeks after injury for histological analysis, ferric iron and macrophage accumulation (CD68), blood and lymphatic vessel remodeling (αSMA; LYVE1). Synovial RNA sequencing was performed for FVIII-/- mice at days 0, 3, and 14 after injury to quantify expression changes of iron regulators and lymphatic markers.

RESULTS

Bleed volumes were similar in FVIII-/- and HypoBALB/c mice. However, pronounced and prolonged synovial iron accumulation colocalizing with macrophages and impaired lymphangiogenesis were detected only in FVIII-/- mice and were prevented by periprocedural FVIII. Gene expression changes involved in iron handling (some genes with dual roles in inflammation) and lymphatic markers supported proinflammatory milieu with iron retention and disturbed lymphangiogenesis.

CONCLUSION

Accumulation and delayed clearance of iron-laden macrophages were associated with defective lymphangiogenesis after hemarthrosis in FVIII-/- mice. The absence of such findings in HypoBALB/c mice suggests that intact lymphatics are required for removal of iron-laden macrophages and that these processes depend on FVIII availability. Studies to elucidate the biological mechanisms of disturbed lymphangiogenesis in hemophilia appear critical to develop new therapeutic targets.

Ferroptosis: a new target for iron overload-induced hemophilic arthropathy synovitis

Iron deposition is closely related to developing haemophilic arthropathy (HA). Studying the relationship between ferroptosis signal expression and iron overload in HA synovium facilitates understanding the pathogenesis of joint synovial hyperplasia in bloodborne arthritis and the development of new protective methods. The knee synovium was collected from HA and osteoarthritis (OA) patients, and pathological changes were analysed by HE and Prussian blue staining. Ferroptosis phenotypes were examined by immunohistochemistry and western blotting. Moreover, ferric ammonium citrate (FAC)-induced was used to construct an in vitro iron overload model to investigate the relationship between iron overload and ferroptosis in synovial fibroblasts (FLS). Furthermore, the factors influencing ferroptosis in FLS were explored. Iron deposition, cell proliferation, and vascular proliferation in the synovium of HA were more obvious. Ferroptosis in HA synovium appears to inhibit. FLS ferroptosis increased with iron accumulation, malondialdehyde (MDA) in cells, and glutathione (GSH) depletion. TNF-α plays a protective role in this process. Blocking the action of TNF-α and inducing ferroptosis significantly reduced synovial proliferation. TNF-α inhibitors combined with a ferroptosis inducer may be a new therapeutic method for HA synovitis.

Value of Contrast-enhanced Ultrasound in Evaluating Synovitis and Predicting Recurrent Joint Bleeding of Hemophilia

OBJECTIVE

Contrast-enhanced ultrasound (CEUS) is advantageous for evaluating microcirculation, and has been applied to assess arthritis in previous studies. However, CEUS examinations have not been studied for hemophilia arthritis. Hemophilia arthritis is different from other arthritis, because it is induced by spontaneous joint bleeding. Hence, CEUS may have special value in evaluating hemophilia arthritis. The present study assessed the value of CEUS in evaluating synovial hypertrophy and predicting recurrent joint bleeding in severe hemophilia A patients.

METHODS

From August 2016 to January 2017, 81 severe hemophilia A patients, who were referred to our hospital for ultrasound joint assessment with conventional ultrasound, were enrolled. Among these 81 patients, 46 patients consented for CEUS examinations on the same day.

RESULTS

Compared to color Doppler flow imaging (CDFI), four more joints presented with a blood flow signal under CEUS mode. In addition, the synovial hypertrophy measured by CEUS was thicker than that measured by conventional ultrasound. The ultrasound scores (including the total grey-scale ultrasound score, joint effusion/hemarthrosis, synovial hypertrophy, CDFI semi-quantitative score, and CEUS semi-quantitative score) were significantly higher in the joint bleeding group than in the no joint bleeding group (P<0.05). Furthermore, these ultrasound scores were positively correlated with the joint bleeding frequency, and had the highest correlation with the CEUS score (r=0.620, P<0.05).

CONCLUSION

CEUS can more accurately assess the degree of synovial hypertrophy and vascularization, and diagnose synovitis, when compared to conventional ultrasound. In addition, CEUS appears to be essential for evaluating the possibility of recurrent joint bleeding, and providing more reliable evidence for individualized treatment.

Interplay Between Iron Overload and Osteoarthritis: Clinical Significance and Cellular Mechanisms

There are multiple diseases or conditions such as hereditary hemochromatosis, hemophilia, thalassemia, sickle cell disease, aging, and estrogen deficiency that can cause iron overload in the human body. These diseases or conditions are frequently associated with osteoarthritic phenotypes, such as progressive cartilage degradation, alterations in the microarchitecture and biomechanics of the subchondral bone, persistent joint inflammation, proliferative synovitis, and synovial pannus. Growing evidences suggest that the conditions of pathological iron overload are associated with these osteoarthritic phenotypes. Osteoarthritis (OA) is an important complication in patients suffering from iron overload-related diseases and conditions. This review aims to summarize the findings and observations made in the field of iron overload-related OA while conducting clinical and basic research works. OA is a whole-joint disease that affects the articular cartilage lining surfaces of bones, subchondral bones, and synovial tissues in the joint cavity. Chondrocytes, osteoclasts, osteoblasts, and synovial-derived cells are involved in the disease. In this review, we will elucidate the cellular and molecular mechanisms associated with iron overload and the negative influence that iron overload has on joint homeostasis. The promising value of interrupting the pathologic effects of iron overload is also well discussed for the development of improved therapeutics that can be used in the field of OA.

A semiquantitative color Doppler ultrasound scoring system for evaluation of synovitis in joints of patients with blood-induced arthropathy

Background

Intra-articular bleeds in patients with inherited bleeding disorders lead to active synovitis which may progress to a chronic state over time. We explored the diagnostic value of color Doppler ultrasound in detecting synovitis in boys with bleeding disorders.

Results

Sixty boys with hemophilia and 3 boys with type 3 von Willebrand disease aged 5 to 18 years (median 12.3 years) were imaged by gray-scale and color Doppler ultrasound (US) in three centers (Beijing, China [n = 22], Guangzhou, China [n = 12] and Toronto, Canada [n = 29])) in this observational study. Images were independently reviewed by two radiologists blinded to clinical data using a subjective semi-quantitative scoring system and objective measurements of synovial thickness and vascularity. Inter-reader reliability for using subjective versus objective color Doppler US methods for assessing synovial vascularity was excellent for the subjective method and moderate/lower range of substantial for the objective method. Agreement between degree of vascularity on color Doppler and extent of synovial hypertrophy on gray-scale US was overall poor for Canada data and moderate for China data. Correlations between degree of vascularity on color Doppler and synovial hypertrophy on gray-scale US, and clinical constructs (total and itemized HJHS scores and total Pettersson X-ray scores) for assessment of blood-induced arthropathy were all poor.

Conclusion

Color Doppler US is a valuable scoring method for evaluating reactive synovitis in joints of subjects with inherited bleeding disorders and holds potential for assessing post-bleed reactive synovitis once further information on its association with timing of the joint bleed becomes available in the literature.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13244-021-01043-0.

Bleeding with iron deposition and vascular remodelling in subchondral cysts: A newly discovered feature unique to haemophilic arthropathy

INTRODUCTION

Joint iron accumulation is the incendiary factor triggering osteochondral destruction, synovial hypertrophy, inflammation, and vascular remodelling in haemophilic arthropathy (HA). Hemosiderin depositions have been described in synovium and, more recently, in cartilage. Clinical observations also suggest hemosiderin accumulation in subchondral cysts, implying cyst bleeding.

AIM

We explored associations between cystic iron accumulation, vascular remodelling and HA status to determine if cystic bleeding may contribute to HA progression.

METHODS

Thirty-six haemophilic joints (16 knees, 10 ankles, and 10 elbows; 31 adult patients with haemophilia A/B) were evaluated by magnetic resonance imaging (MRI) for subchondral cysts and hemosiderin. Cyst score (WORMS) and hemosiderin presence were compared between haemophilic and osteoarthritic knees, matched for the degree of arthritis (Kellgren-Lawrence score). Cystic iron accumulation, vascular remodelling and macrophage cell counts were also compared by immunohistochemistry in explanted joint tissues. In haemophilic knees, cyst number and extent of hemosiderin deposition were correlated with haemophilia joint health scores (HJHS).

RESULTS

Cystic hemosiderin was detected in 78% of haemophilic joints. Cyst score and presence of hemosiderin were significantly higher in haemophilic compared to osteoarthritic knees. Cyst score and presence of hemosiderin strongly correlated with HJHS. Moreover, iron deposition and vascular remodelling were significantly more pronounced within cysts in haemophilic compared to osteoarthritic knees, with similar total cell and macrophage count.

CONCLUSION

These findings suggest the presence of subchondral bleeding in haemophilia, contributing to poor joint health outcomes. Observations of bleeding into osseous structures are novel and should inform investigations of new therapies.

Hemophilic arthropathy: Current knowledge and future perspectives

Hemophilia A and B are rare X-linked inherited bleeding disorders caused by complete or partial deficiency in or the absence of coagulation factors VIII and IX. Recurrent joint bleeding (hemarthrosis) is the most frequent clinical manifestation of severe hemophilia. Unless appropriately managed, even subclinical hemarthrosis can lead to the development of hemophilic arthropathy, a disabling condition characterized by joint remodelling, chronic pain, and a reduced quality of life, and eventually requires joint replacement. Given the lack of specific treatments to reduce blood-induced synovitis, the prevention of bleeding is pivotal to the maintenance of joint health. Prophylactic coagulation factor replacement therapy using extended half-life recombinant drugs has significantly improved patients' quality of life by reducing the burden of intravenous injections, and the more recent introduction of nonreplacement therapies such as subcutaneous emicizumab injections has improved treatment adherence and led to the greater protection of patients with hemophilia A. However, despite these advances, chronic arthropathy is still a significant problem. The introduction of point-of-care ultrasound imaging has improved the diagnosis of acute hemarthrosis and early hemophilic arthropathy, and allowed the better monitoring of progressive joint damage, but further research into the underlying mechanisms of the disease is required to allow the development of more targeted treatment. In the meantime, patient management should be based on the risk factors for the onset and progression of arthropathy of each individual patient, and all patients should be collaboratively cared for by multidisciplinary teams of hematologists, rheumatologists, orthopedic surgeons, and physiotherapists at comprehensive hemophilia treatment centers.

FVIII at the crossroad of coagulation, bone and immune biology: Emerging evidence of biological activities beyond hemostasis

Hemophilia A is an X-linked hereditary disorder that results from deficient coagulation factor VIII (FVIII) activity, leading to spontaneous bleeding episodes, particularly in joints and muscles. FVIII deficiency has been associated with altered bone remodeling, dysregulated macrophage polarization, and inflammatory processes that are associated with the neoformation of abnormal blood vessels. Treatment based on FVIII replacement can lead to the development of inhibitors that render FVIII concentrate infusion ineffective. In this context, hemophilia has entered a new therapeutic era with the development of new drugs, such as emicizumab, that seek to restore the hemostatic balance by bypassing pathologically acquired antibodies. We discuss the potential extrahemostatic functions of FVIII that may be crucial for defining future therapies in hemophilia.

Musculoskeletal ultrasound in hemophilia: Results and recommendations from a global survey and consensus meeting

Introduction

For persons with hemophilia, optimization of joint outcomes is an important unmet need. The aim of this initiative was to determine use of ultrasound in evaluating arthropathy in persons with hemophilia, and to move toward consensus among hemophilia care providers regarding the preferred ultrasound protocols for global adaptation.

Methods

A global survey of hemophilia treatment centers was conducted that focused on understanding how and why ultrasound was being used and endeavored to move toward consensus definitions of both point‐of‐care musculoskeletal ultrasound (POC‐MSKUS) and full diagnostic ultrasound, terminology to describe structures being assessed by ultrasound, and how these assessments should be interpreted. Next, an in‐person meeting of an international group of hemophilia health care professionals and patient representatives was held, with the objective of achieving consensus regarding the acquisition and interpretation of POC‐MSKUS and full diagnostic ultrasound for use in the assessment of musculoskeletal (MSK) pathologies in persons with hemophilia.

Results

The recommendations were that clear definitions of the types of ultrasound examinations should be adopted and that a standardized ultrasound scoring/measurement system should be developed, tested, and implemented. The scoring/measurement system should be tiered to allow for a range of complexity yet maintain the ability for comparison across levels.

Conclusion

Ultrasound is an evolving technology increasingly used for the assessment of MSK outcomes in persons with hemophilia. As adoption increases globally for clinical care and research, it will become increasingly important to establish clear guidelines for image acquisition, interpretation, and reporting to ensure accuracy, consistency, and comparability across groups.

On-demand treatment with the iron chelator deferasirox is ineffective in preventing blood-induced joint damage in haemophilic mice

INTRODUCTION

Early intervention in the devastating process of haemophilic arthropathy (HA) is highly desirable, but no disease-modifying therapy is currently available. Considering the pivotal role of iron in the development of HA, iron chelation is considered a promising therapeutic approach. A previous study in haemophilic mice demonstrated that treatment with the iron chelator deferasirox (DFX) 8 weeks before joint bleed induction, attenuated cartilage damage upon blood exposure. However, in haemophilia patients this approach is not opportune given the unpredictable occurrence of hemarthroses.

AIM

To evaluate the effectiveness of on-demand DFX treatment, initiated immediately after joint bleed induction.

METHODS

A joint bleed was induced in 66 factor VIII-deficient mice by infra-patellar needle puncture. Mice were randomly assigned to treatment with either placebo (drinking water) or DFX (dissolved in drinking water) throughout the study. Five weeks after joint bleed induction, inflammation and cartilage damage were assessed histologically. Joints of ten bleed naive haemophilic mice served as controls.

RESULTS

A joint bleed resulted in significant inflammation and cartilage damage in the blood-exposed joint compared with those of control animals, in both the placebo and DFX group (all p = <.05). No differences in tibiofemoral or patellar inflammation (p = .305 and p = .787, respectively) nor cartilage damage (p = .265 and p = .802, respectively) were found between the blood-exposed joints of both treatment groups.

CONCLUSION

On-demand treatment with DFX does not prevent joint damage following blood exposure in haemophilic mice. DFX seems unable to reach the joint in time to exert its effect before the irreversible harmful process is initiated.

Haemophilia

Haemophilia A and B are rare congenital, recessive X-linked disorders caused by lack or deficiency of clotting factor VIII (FVIII) or IX (FIX), respectively. The severity of the disease depends on the reduction of levels of FVIII or FIX, which are determined by the type of the causative mutation in the genes encoding the factors (F8 and F9, respectively). The hallmark clinical characteristic, especially in untreated severe forms, is bleeding (spontaneous or after trauma) into major joints such as ankles, knees and elbows, which can result in the development of arthropathy. Intracranial bleeds and bleeds into internal organs may be life-threatening. The median life expectancy was ~30 years until the 1960s, but improved understanding of the disorder and development of efficacious therapy based on prophylactic replacement of the missing factor has caused a paradigm shift, and today individuals with haemophilia can look forward to a virtually normal life expectancy and quality of life. Nevertheless, the potential development of inhibitory antibodies to infused factor is still a major hurdle to overcome in a substantial proportion of patients. Finally, gene therapy for both types of haemophilia has progressed remarkably and could soon become a reality.

Systemic vascular basement membrane markers linked to synovial vascular remodeling are biomarkers of hemarthrosis in patients with hemophilia

INTRODUCTION

Interstitial, cartilage, and bone collagens have been proposed as biomarkers of joint deterioration in hemophilic arthropathy. The role of basement membrane (type IV and VIII) collagens as biomarkers of endothelial turnover in relation to acute joint bleeding is not understood.

METHODS

Thirty-one adult patients with hemophilia were studied prospectively for 3 years with musculoskeletal ultrasound/power Doppler (MSKUS/PD) during pain-free intervals and painful events for joint bleed status, synovial vascular flow, and 10 plasma markers of collagen turnover. Joint health was determined using Hemophilia Joint Health Scores and Pettersson scores. In animal studies, bleeding was induced in factor VIII-/- mice by knee joint injury. Synovial vascular remodeling was assessed using MSKUS/PD and histology. Murine plasma samples were analyzed for type IV collagen turnover markers.

RESULTS

Ninety-one patient visits were compiled. Twenty-five were due to acute painful episodes, with 16 confirmed hemarthroses. Type IV collagen turnover markers (PRO-C4 and C4M), and a type VIII collagen synthesis marker (PRO-C8), were transiently elevated during acute hemarthrosis. Hemarthrosis was accompanied by increased synovial microvascular flow (MSKUS/PD), and levels of type IV collagen markers correlated with PD signals in the joint. In factor VIII-deficient mice, plasma levels of type IV collagen turnover markers correlated negatively with synovial αSMA staining, indicating that reduced type IV collagen turnover was associated with thicker vessels.

CONCLUSIONS

Our findings suggest that basement membrane turnover markers, closely linked to synovial vascular remodeling, may be systemic biomarkers of acute hemarthrosis. Vascular instability during neovascularization may be involved in the dynamics of hemarthrosis.

EPCR deficiency or function-blocking antibody protects against joint bleeding-induced pathology in hemophilia mice

We recently showed that clotting factor VIIa (FVIIa) binding to endothelial cell protein C receptor (EPCR) induces anti-inflammatory signaling and protects vascular barrier integrity. Inflammation and vascular permeability are thought to be major contributors to the development of hemophilic arthropathy following hemarthrosis. The present study was designed to investigate the potential influence of FVIIa interaction with EPCR in the pathogenesis of hemophilic arthropathy and its treatment with recombinant FVIIa (rFVIIa). For this, we first generated hemophilia A (FVIII-/-) mice lacking EPCR (EPCR-/-FVIII-/-) or overexpressing EPCR (EPCR++ FVIII-/-). Joint bleeding was induced in FVIII-/-, EPCR-/-FVIII-/-, and EPCR++FVIII-/- mice by needle puncture injury. Hemophilic synovitis was evaluated by monitoring joint bleeding, change in joint diameter, and histopathological analysis of joint tissue sections. EPCR deficiency in FVIII-/- mice significantly reduced the severity of hemophilic synovitis. EPCR deficiency attenuated the elaboration of interleukin-6, infiltration of macrophages, and neoangiogenesis in the synovium following hemarthrosis. A single dose of rFVIIa was sufficient to fully prevent the development of milder hemophilic synovitis in EPCR-/-FVIII-/- mice. The development of hemophilic arthropathy in EPCR-overexpressing FVIII-/- mice did not significantly differ from that of FVIII-/- mice, and 3 doses of rFVIIa partly protected against hemophilic synovitis in these mice. Consistent with the data that EPCR deficiency protects against developing hemophilic arthropathy, administration of a single dose of EPCR-blocking monoclonal antibodies markedly reduced hemophilic synovitis in FVIII-/- mice subjected to joint bleeding. The present data indicate that EPCR could be an attractive new target to prevent joint damage in hemophilia patients.

In vivo fluorescence molecular tomography of induced haemarthrosis in haemophilic mice: link between bleeding characteristics and development of bone pathology

Background

Haemophilic arthropathy is a chronic and debilitating joint disease caused by recurrent spontaneous joint bleeds in patients with haemophilia. Understanding how characteristics of individual joint bleeds relate to the subsequent development of arthropathy could improve management and prevention of this joint disease. Here, we aimed to explore relations between joint bleed characteristics and development of bone pathology in a mouse model of haemophilic arthropathy by using novel in vivo imaging methodology.

Methods

We characterised induced knee bleeds in a murine model of haemophilic arthropathy by quantitative in vivo fluorescence molecular tomography (FMT) and by measurements of changes in the diameter of the injured knee. Wild-type mice and non-injured haemophilic mice acted as controls. Development of arthropathy was characterised by post mortem evaluation of bone pathology by micro-CT 14 days after bleed-induction. In an in vitro study, we assessed the effect of blood on the quantification of fluorescent signal with FMT.

Results

In most injured haemophilic mice, we observed significant loss of trabecular bone, and half of the mice developed pathological bone remodelling. Development of pathological bone remodelling was associated with significantly increased fluorescent signal and diameter of the injured knee just 1 day after induction of the bleed. Further, a correlation between the fluorescent signal 1 day after induction of the bleed and loss of trabecular bone reached borderline significance. In the in vitro study, we found that high concentrations of blood significantly decreased the fluorescent signal.

Conclusion

Our results add novel insights on the pathogenesis of haemophilic arthropathy and underline the importance of the acute phase of joint bleeds for the subsequent development of arthropathy.

Proteoglycan synthesis rate as a novel method to measure blood-induced cartilage degeneration in non-haemophilic and haemophilic rats

INTRODUCTION

Haemophilic animal models are used to study blood-induced cartilage damage, but quantitative and sensitive outcome measures are needed.

AIM

To develop a novel quantitative method for detecting early cartilage degeneration in a haemophilic rat model of blood-induced joint damage.

METHODS

The ³⁵ Sulphate incorporation (³⁵ SO₄ ^2- assay) was applied to tibial and patellar cartilage of wild-type rats to quantify baseline proteoglycan synthesis and to evaluate the effect of 4-day blood exposure in vitro. Next, haemarthrosis was induced in 39 FVIII-deficient rats and characterized by changes in knee joint diameter and development of bone pathology (using micro-CT). Four- and 16-day posthaemarthrosis proteoglycan synthesis rate (PSR) was assessed using the ³⁵ SO₄ ^2- assay, with the contralateral knee as control.

RESULTS

In vitro, a decrease in PSR in tibial and patellar cartilage was demonstrated following blood exposure. In vivo, joint diameter and development of bone pathology confirmed successful induction of haemarthrosis. In the blood-exposed knee, tibial and patellar PSR was inhibited 4 and 16 days after induced haemarthrosis. Interestingly, at day 16 the proteoglycan synthesis in the contralateral knee was also inhibited to an extent correlating with that of the blood-exposed knee.

CONCLUSION

For the first time, early changes in cartilage matrix synthesis upon blood exposure were quantified with the ³⁵ SO₄ ^2- assay in a haemophilic rat model, establishing this assay as a novel method to study blood-induced cartilage damage.

Joint Bleeding Tendencies in Adult Patients With Hemophilia: It's Not All Pharmacokinetics

Hemophilic arthropathy from joint bleeding remains a complication with major morbidity in the increasingly aging patients with hemophilia. Prophylactic clotting factor infusions, based on pharmacokinetic dosing to reduce bleeding rates, are being explored more and more. However, there is little evidence on the benefits of pharmacokinetic dosing in direct association with bleeding events. Here, we prospectively followed a cohort of adult patients with hemophilia A and B (n = 26) and arthropathic joints on various clotting factor products over a period of 2 years with clinical and radiographic joint health assessments, frequent joint ultrasound, and pharmacokinetic studies. Joint bleeds and synovitis with synovial vascularity changes were objectively diagnosed by musculoskeletal ultrasound and power Doppler and analyzed in relation to pharmacokinetic, joint- and patient-specific parameters. Results revealed that, contrary to common beliefs, bleeding episodes were not readily explained by pharmacokinetic features, as they were not associated with more time spent below certain clotting factor thresholds. Joint bleeding was found to be associated with prominent vascularity changes, suggesting that vascular remodeling and leakiness may contribute to joint bleeding that cannot be prevented by clotting factor replacement alone.

Mechanisms of vascular permeability and remodeling associated with hemarthrosis in factor VIII-deficient mice

BACKGROUND

Vascular remodeling associated with hemophilic arthropathy (HA) may contribute to bleed propagation, but the mechanisms remain poorly understood.

OBJECTIVES

To explore molecular mechanisms of HA and the effects of hemostasis correction on synovial vascular remodeling after joint injury in hypocoagulable mice.

METHODS

Factor VIII (FVIII)-deficient mice +/- FVIII treatment and hypocoagulable wild-type mice (Hypo BALB/c) were subjected to subpatellar puncture. Hypo BALB/c mice were treated with warfarin and anti-FVIII before injury, after which warfarin was continued for 2 weeks or reversed +/- continuous anti-FVIII until harvest. Synovial vascularity was analyzed at baseline and 2 to 4 weeks post injury by histology, musculoskeletal ultrasound with power Doppler (microvascular flow), and Evans blue extravasation (vascular permeability). Synovial gene expression and systemic markers of vascular collagen turnover were studied in FVIII-deficient mice by RNA sequencing and enzyme-linked immunosorbent assay.

RESULTS

Vascular changes occurred in FVIII-deficient and Hypo BALB/c mice after injury with minimal effect of hemostasis correction. Increased vascular permeability was only significant in FVIII-deficient mice, who exhibited more pronounced vascular remodeling than Hypo BALB/c mice despite similar bleed volumes. FVIII-deficient mice exhibited a strong transcriptional response in synovium that was only partially affected by FVIII treatment and involved genes relating to angiogenesis and extracellular matrix remodeling, with vascular collagen turnover markers detected systemically.

CONCLUSIONS

Intact hemostasis at the time of hemarthrosis and during healing are both critical to prevent vascular remodeling, which appears worse with severe and prolonged FVIII deficiency. Unbiased RNA sequencing revealed potential targets for intervention and biomarker development to improve management of HA.

TAFI deficiency causes maladaptive vascular remodeling after hemophilic joint bleeding

Excessive vascular remodeling is characteristic of hemophilic arthropathy (HA) and may contribute to joint bleeding and the progression of HA. Mechanisms for pathological vascular remodeling after hemophilic joint bleeding are unknown. In hemophilia, activation of thrombin-activatable fibrinolysis inhibitor (TAFI) is impaired, which contributes to joint bleeding and may also underlie the aberrant vascular remodeling. Here, hemophilia A (factor VIII-deficient; FVIII-deficient) mice or TAFI-deficient mice with transient (antibody-induced) hemophilia A were used to determine the role of FVIII and TAFI in vascular remodeling after joint bleeding. Excessive vascular remodeling and vessel enlargement persisted in FVIII-deficient and TAFI-deficient mice, but not in transient hemophilia WT mice, after similar joint bleeding. TAFI-overexpression in FVIII-deficient mice prevented abnormal vessel enlargement and vascular leakage. Age-related vascular changes were observed with FVIII or TAFI deficiency and correlated positively with bleeding severity after injury, supporting increased vascularity as a major contributor to joint bleeding. Antibody-mediated inhibition of uPA also prevented abnormal vascular remodeling, suggesting that TAFI's protective effects include inhibition of uPA-mediated plasminogen activation. In conclusion, the functional TAFI deficiency in hemophilia drives maladaptive vascular remodeling in the joints after bleeding. These mechanistic insights allow targeted development of potentially new strategies to normalize vascularity and control rebleeding in HA.

Merging into the mainstream: the evolution of the role of point-of-care musculoskeletal ultrasound in hemophilia

Bleeding with resultant hemophilic arthropathy constitutes the largest cause of morbidity in patients with hemophilia. It results from repeated bleeding episodes in the joint and is characterized by synovial hypertrophy and cartilage and bony destruction. Hemophilic arthropathy assessment is a continually evolving process and is particularly challenging in children and young adults in whom joint disease may be missed or underestimated as obtaining serial "baseline" magnetic resonance imaging scans of multiple clinically asymptomatic or nearly asymptomatic joints may be unjustifiable and cost-ineffective. Musculoskeletal ultrasound-particularly, point-of-care musculoskeletal ultrasound-has emerged as a promising imaging modality for the early detection and management of hemophilic arthropathy, and for the evaluation of hemarthrosis and painful musculoskeletal episodes in patients with hemophilia. This review summarizes currently available data on the emerging role of this new imaging modality, its limitations, and gaps in knowledge. The review also raises unanswered questions, highlights the need for consolidated research efforts, and delineates future directions expected to advance this technology and optimize its use in this patient population.

Role of the brain-gut axis in gastrointestinal cancer

Several studies have largely focused on the significant role of the nervous and immune systems in the process of tumorigenesis, including tumor growth, proliferation, apoptosis, and metastasis. The brain-gut-axis is a new paradigm in neuroscience, which describes the biochemical signaling between the gastrointestinal (GI) tract and the central nervous system. This axis may play a critical role in the tumorigenesis and development of GI cancers. Mechanistically, the bidirectional signal transmission of the brain-gut-axis is complex and remains to be elucidated. In this article, we review the current findings concerning the relationship between the brain-gut axis and GI cancer cells, focusing on the significant role of the brain-gut axis in the processes of tumor proliferation, invasion, apoptosis, autophagy, and metastasis. It appears that the brain might modulate GI cancer by two pathways: the anatomical nerve pathway and the neuroendocrine route. The simulation and inactivation of the central nervous, sympathetic, and parasympathetic nervous systems, or changes in the innervation of the GI tract might contribute to a higher incidence of GI cancers. In addition, neurotransmitters and neurotrophic factors can produce stimulatory or inhibitory effects in the progression of GI cancers. Insights into these mechanisms may lead to the discovery of potential prognostic and therapeutic targets.

Advanced magnetic resonance imaging of cartilage components in haemophilic joints reveals that cartilage hemosiderin correlates with joint deterioration

INTRODUCTION

Evidence suggests that toxic iron is involved in haemophilic joint destruction.

AIM

To determine whether joint iron deposition is linked to clinical and imaging outcomes in order to optimize management of haemophilic joint disease.

METHODS

Adults with haemophilia A or haemophilia B (n = 23, ≥ age 21) of all severities were recruited prospectively to undergo assessment with Hemophilia Joint Health Scores (HJHS), pain scores (visual analogue scale [VAS]) and magnetic resonance imaging (MRI) at 3T using conventional MRI protocols and 4-echo 3D-UTE-Cones sequences for one affected arthropathic joint. MRI was scored blinded by two musculoskeletal radiologists using the International Prophylaxis Study Group (IPSG) MRI scale. Additionally, UTE-T2* values of cartilage were quantified. Correlations between parameters were performed using Spearman rank correlation. Two patients subsequently underwent knee arthroplasty, which permitted linking of histological findings (including Perl's reaction) with MRI results.

RESULTS

MRI scores did not correlate with pain scores or HJHS. Sixteen joints had sufficient cartilage for UTE-T2* analysis. T2* values for cartilage correlated inversely with HJHS (r_s  = -0.81, P < 0.001) and MRI scores (r_s  = -0.52, P = 0.037). This was unexpected since UTE-T2* values decrease with better joint status in patients with osteoarthritis, suggesting that iron was present and responsible for the effects. Histological analysis of cartilage confirmed iron deposition within chondrocytes, associated with low UTE-T2* values.

CONCLUSIONS

Iron accumulation can occur in cartilage (not only in synovium) and shows a clear association with joint health. Cartilage iron is a novel biomarker which, if quantifiable with innovative joint-specific MRI T2* sequences, may guide treatment optimization.

Development and Reliability of the Joint Tissue Activity and Damage Examination for Quantitation of Structural Abnormalities by Musculoskeletal Ultrasound in Hemophilic Joints

OBJECTIVES

Musculoskeletal ultrasound (US) is used increasingly to examine hemophilic arthropathy. However, quantitative algorithms to document findings are lacking. We developed and sought to validate a protocol quantifying hemophilic joint abnormalities.

METHODS

Thirty-one patients with hemophilia were examined serially for 2 years with musculoskeletal US (≈600 joint examinations and ≈6000 images). Based on the spectrum of pathologies, a quantitative algorithm, named Joint Tissue Activity and Damage Examination (JADE), was developed for soft tissue and osteochondral measurements, including power Doppler, using nominal group techniques. To study intra- and inter-rater reliability, 8 musculoskeletal US-experienced hemophilia providers performed anatomic landmark recognition and tissue measurements on 86 images with arthropathic changes, with repetition 1 month later. Twenty-three musculoskeletal US-inexperienced providers performed similar assessments. Inter-operator reliability was established by 6 musculoskeletal US-experienced hemophilia providers, each acquiring images and JADE assessments of 3 hemophilic arthropathic joints. A radiologist and musculoskeletal sonographer functioned as adjudicators. The statistical analysis was performed with the intraclass correlation coefficient (ICC), Fleiss κ, and Cohen κ where appropriate.

RESULTS

The musculoskeletal US-experienced providers showed excellent intra-and inter-rater reliability for tissue measurements (ICCs, 0.94-0.96). Agreement was good to excellent for landmark recognition (Fleiss κ, 0.87-0.94). Inter-operator reliability was excellent for measurements and landmark recognition (ICC, 0.90; Fleiss κ, 1.0). Agreement with adjudicators was mostly good to excellent. Musculoskeletal US-inexperienced providers showed excellent inter-rater reliability for measurements (ICC, 0.96) and moderate agreement for landmark recognition (Fleiss κ, 0.58).

CONCLUSIONS

The JADE protocol appears feasible for quantifying hemophilic intra-articular abnormalities. Musculoskeletal US-trained hemophilia providers showed high intra-rater, inter-rater, and inter-operator reliability, supporting JADE as a protocol for clinical management and research.

Increased Accumulation and Retention of rhFVIIa (eptacog beta) in Knee Joints of Hemophilia A Mice Compared to Wild-Type Mice

Our earlier studies showed that recombinant human factor VIIa (rhFVIIa) administered intravascularly in mice disappeared rapidly from the circulation. However, a small fraction of rhFVIIa that entered extravascular remained functionally active for an extended period. The present study aims to investigate the dose-dependency of rhFVIIa accumulation and retention in mouse knee joints and test whether the hemophilic condition affects rhFVIIa sequestration in joints. Wild-type and FVIII^-/- mice were injected with three doses of rhFVIIa (eptacog beta, 90, 250, and 500 μg/kg) via the tail vein. At varying times following rhFVIIa administration, blood and knee joints were collected to measure FVIIa activity and antigen levels in plasma and joint tissues. Joint tissue sections were analyzed by immunohistochemistry for the presence of rhFVIIa. Vascular permeability was assessed by either Evans Blue dye or fluorescein dextran extravasation. The study showed that rhFVIIa accumulated in knee joints of wild-type and FVIII^-/- mice in a dose-dependent manner. rhFVIIa antigen and FVIIa activity could be detectable in joints for at least 7 days. Significantly higher levels of rhFVIIa accumulation were observed in knee joints of FVIII^-/- mice compared with that of wild-type mice. Immunohistochemical analyses confirmed higher levels of rhFVIIa retention in FVIII^-/- mice compared with wild-type mice. Additional studies showed that FVIII^-/- mice were more permissible to vascular leakage. In conclusion, the present data demonstrate a dose-dependent accumulation of rhFVIIa in knee joints, and the hemophilic condition enhances the entry of rhFVIIa from circulation to the extravascular. The present data will be useful in improving rhFVIIa prophylaxis.

Timely and large dose of clotting factor IX provides better joint wound healing after hemarthrosis in hemophilia B mice

Bleeding into the joints represents the major morbidity of severe hemophilia and predisposes it to hemophilic arthropathy (HA). In a reproducible hemarthrosis mouse model, we found distinct changes in thrombin activity in joint tissue homogenate following exposure of the joint to blood in wide type (WT) and hemophilic B mice. Specifically, at early time points (4 h and 24 h) after hemarthrosis, thrombin activity in WT mice quickly peaked at 4 h, and returned to baseline after 1 week. In hemophilia B mice, there was no/minimal thrombin activity in joint tissues at 4 h and 24 h, whereas at 72 h and thereafter, thrombin activity kept rising, and persisted at a higher level. Nevertheless, prothrombin had not decreased in both WT and hemophilia. The pattern was also confirmed by Western blotting and immunostaining. To optimize the protection against development of HA, we tested different treatment regimens by administration of clotting factor IX into hemophilia B mouse after hemarthrosis induction, including a total of 600 IU/kg FIX within the first 24 h or the whole 2-week period. We concluded that timely (in the first 24 h) and sufficient hemostasis correction is critical for a better protection against the development of hemophilic arthropathy.

Bleed volume of experimental knee haemarthrosis correlates with the subsequent degree of haemophilic arthropathy

BACKGROUND

Haemophilic arthropathy is the main morbidity of haemophilia. The individual pathological response to the same number of clinically evident joint bleeds is highly variable; thus, it remains unknown if certain joint bleeding characteristics are critical for the development of arthropathy.

AIM

To study the relation between bleed volume and subsequent development of arthropathy, we aimed to develop quantitative in vivo imaging of active joint bleeds in a mouse model of haemophilia.

METHODS

Haemophilia A (F8-KO) and wild-type (WT) mice were IV-dosed with a micro-CT blood pool contrast agent prior to an induced knee haemarthrosis or sham procedure. The mice were micro-CT scanned five times the following 2 days to characterise and quantify the induced haemarthrosis in vivo. On Day 14, the mice were euthanized and pathological changes evaluated by histology and micro-CT. Additionally, bleeding characteristics in vehicle-treated F8-KO mice were compared with those of recombinant FVIII (rFVIII)-treated F8-KO mice.

RESULTS

F8-KO mice had a significantly larger bleed volume than WT mice at all scan time points. The bleed volume 12 hours after induction of haemarthrosis correlated with the subsequent degree of arthropathy. Presence of µCT-detectable bone pathology was associated with a significantly increased bleed volume among F8-KO mice. rFVIII treatment significantly reduced bleed volume in F8-KO mice.

CONCLUSION

Quantitative in vivo contrast-enhanced micro-CT imaging can be used to characterize and quantify joint bleeds in a mouse model of haemophilic arthropathy. The bleed volume correlates with the subsequent degree of arthropathy.