Histological changes in murine haemophilic synovitis: a quantitative grading system to assess blood-induced synovitis

Activated factor X delivered by adeno-associated virus significantly inhibited bleeding and alleviated hemophilic synovitis in hemophilic mice

In hemophilia, deficiency of factor VIII or IX prevents the activation of the common coagulation pathway, and inhibits the conversion of FX to activated FXa, which is required for thrombin generation. We hypothesized that the direct expressed FXa has the potential to activate the common pathway and restore coagulation in hemophilia patients. In this study, the cassettes that expressed FXa, FXaop and FXa-FVII were packaged into an engineered AAV capsid, AAV843, and were delivered into hemophilia A and B mice by intravenous injection. AAV-FXaop could be stably expressed in vivo and showed the best immediate and prolonged hemostatic effects, similar to those of commercial drugs (Xyntha and Benefix). AAV-FXaop also significantly inhibited bleeding in hemophilia A mice with inhibitors. In addition, FXa expression in joints significantly alleviated the occurrence of hemophilic synovitis. AAV-delivered FXa may be a novel target for treating hemophilic and hemophilic synovitis.

Anti-inflammatory effect of a novel piperazino-enaminone delivered by liposomes in a mouse model of hemophilic arthropathy

Hemophilic arthropathy (HA) is a condition caused by recurrent intra-articular bleeding in patients with hemophilia. Pro-inflammatory cytokines play a crucial role in the pathogenesis of HA. Our previous research demonstrated that a novel compound, piperazino-enaminone (JODI), effectively inhibited pro-inflammatory cytokines, including IL-6, MCP-1, MIP-1α, and MIP-1β, in a mouse model of hemarthrosis. This study aims to enhance the anti-inflammatory effect of JODI by employing nanoparticle delivery systems, which could potentially improve its poor water solubility. Here, we developed liposomes modified with polyethylene glycol (PEG) for the delivery of JODI (JODI-LIP), and found that JODI-LIP exhibited uniform size, morphology, good stability and in vitro release degree. JODI-LIP mitigated cytotoxicity of JODI, and significantly suppressed the production of pro-inflammatory cytokines (TNF-α and IL-1β) and nitric oxide (NO) release in RAW 264.7 cells stimulated by lipopolysaccharide (LPS), as well as the proliferation of human fibroblast-like synovial (HFLS) cells. In a murine model of HA, JODI-LIP demonstrated superior efficacy in ameliorating joint swelling and synovitis, compared to JODI. Importantly, JODI-LIP markedly reduced pro-inflammatory cytokines (TNF-α, IFN-γ, IL-33, and MCP-1) in injured joints. No hepatic or hematological toxicity was observed in mice treated with JODI-LIP. In summary, our results suggest that JODI-LIP holds promise as a therapeutic intervention for HA by attenuating pro-inflammatory cytokine levels.

AAV mediated repression of Neat1 lncRNA combined with F8 gene augmentation mitigates pathological mediators of joint disease in haemophilia

Haemophilic arthropathy (HA), a common comorbidity in haemophilic patients leads to joint pain, deformity and reduced quality of life. We have recently demonstrated that a long non-coding RNA, Neat1 as a primary regulator of matrix metalloproteinase (MMP) 3 and MMP13 activity, and its induction in the target joint has a deteriorating effect on articular cartilage. In the present study, we administered an Adeno-associated virus (AAV) 5 vector carrying an short hairpin (sh)RNA to Neat1 via intra-articular injection alone or in conjunction with systemic administration of a capsid-modified AAV8 (K31Q) vector carrying F8 gene (F8-BDD-V3) to study its impact on HA. AAV8K31Q-F8 vector administration at low dose, led to an increase in FVIII activity (16%-28%) in treated mice. We further observed a significant knockdown of Neat1 (~40 fold vs. untreated injured joint, p = 0.005) in joint tissue of treated mice and a downregulation of chondrodegenerative enzymes, MMP3, MMP13 and the inflammatory mediator- cPLA2, in mice receiving combination therapy. These data demonstrate that AAV mediated Neat1 knockdown in combination with F8 gene augmentation can potentially impact mediators of haemophilic joint disease.

DMT1-mediated iron overload accelerates cartilage degeneration in Hemophilic Arthropathy through the mtDNA-cGAS-STING axis

INTRODUCTION

Excess iron contributes to Hemophilic Arthropathy (HA) development. Divalent metal transporter 1 (DMT1) delivers iron into the cytoplasm, thus regulating iron homeostasis.

OBJECTIVES

We aimed to investigate whether DMT1-mediated iron homeostasis is involved in bleeding-induced cartilage degeneration and the molecular mechanisms underlying iron overload-induced chondrocyte damage.

METHODS

This study established an in vivo HA model by puncturing knee joints of coagulation factor VIII gene knockout mice with a needle, and mimicked iron overload conditions in vitro by treatment of Ferric ammonium citrate (FAC).

RESULTS

We demonstrated that blood exposure caused iron overload and cartilage degeneration, as well as elevated expression of DMT1. Furthermore, DMT1 silencing alleviated blood-induced iron overload and cartilage degeneration. In hemophilic mice, articular cartilage degeneration was also suppressed by intro-articularly injection of DMT1 adeno-associated virus 9 (AAV9). Mechanistically, RNA-sequencing analysis indicated the association between iron overload and cGAS-STING pathway. Further, iron overload triggered mtDNA-cGAS-STING pathway activation, which could be effectively mitigated by DMT1 silencing. Additionally, we discovered that RU.521, a potent Cyclic GMP-AMP Synthase (cGAS) inhibitor, successfully suppressed the downward cascades of cGAS-STING, thereby protecting against chondrocyte damage.

CONCLUSION

Taken together, DMT1-mediated iron overload promotes chondrocyte damage and murine HA development, and targeted DMT1 may provide therapeutic and preventive approaches in HA.

Targeted delivery of miR125a-5p and human Factor VIII attenuates molecular mediators of hemophilic arthropathy

Hemophilic arthropathy (HA) due to repeated bleeding into the joint cavity is a major cause of morbidity in patients with hemophilia. The molecular mechanisms contributing to this condition are not well characterized. MicroRNAs (miRs) are known to modulate the phenotype of multiple joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). Since miR125a is known to modulate disease progression in OA and RA, we performed a targeted screen of miR125a-5p and its target genes in a murine model of chronic HA. A digital PCR analysis demonstrated significant downregulation of miR125a-5p (2-fold vs control joint). Further molecular evaluation revealed elevated expression of the immunological markers STAT1 (7.6-fold vs control joint) and TRAF6 (10.6 fold vs control joint), which are direct targets of miR125a-5p. We then studied the impact of targeted overexpression of miR125a-5p using an Adeno-associated virus (AAV) vector in modulating the molecular mediators of HA. AAV5-miR125a vectors were administered intra-articularly either alone or in combination with a low dose of AAV8-based human factor 8 (F8) gene in a murine model of HA. We observed significantly increased expression of miR125a-5p in AAV5-miR125a administered mice (~12 fold vs injured joint) or in combination with AAV8-F8 vectors (~44 fold vs injured joint). The activity assay revealed ~17 %-20 % FVIII levels in mice that received low dose liver-directed F8 gene therapy. Further immunohistochemical analysis, demonstrated a decrease in inflammatory markers (STAT1 and TRAF6) and cartilage-degrading matrix metalloproteinases (MMPs) 3, 9, 13 in the joints of treated animals. These data highlight the crucial role of miR125a-5p in the development of HA.

Activation of the Acute-Phase Response in Hemophilia

To identify recurrent inflammation in hemophilia, we assessed the acute-phase response in the blood of patients with hemophilia A and B. Compared to age- and weight-matched controls, blood levels of interleukin-6 (IL-6), C-reactive protein (CRP), and LPS-binding protein (LBP) were significantly elevated in the entire cohort of hemophilia patients but exhibited a particularly pronounced increase in obese hemophilia patients with a body mass index (BMI) ≥30. Subgroup analysis of the remaining nonobese hemophilia patients (BMI: 18-29.9) revealed a significant spike of IL-6, CRP, and LBP in connection with a de-novo increase of soluble IL-6 receptor α (sIL-6Rα) in patients with bleeding events within the last month. Hemophilia patients who did not experience recent bleeding had IL-6, CRP, and sIL-6Rα blood levels similar to healthy controls. We did not find increased IL-6 or acute-phase reactants in hemophilia patients with arthropathy or infectious disease. The role of IL-6 as a marker of bleeding in hemophilia was confirmed in hemophilia patients with acute bleeding events as well as in transgenic hemophilia mice after needle puncture of the knee, which exhibited an extensive hematoma and a 150-fold increase of IL-6 blood levels within 7 days of the injury compared to needle-punctured control mice. Notably, IL-6 blood levels shrunk to a fourfold elevation in hemophilia mice over controls after 28 days, when the hematoma was replaced by arthrofibrosis. These findings indicate that acute-phase reactants in combination with sIL-6Rα could be sensitive biomarkers for the detection of acute and recent bleeding events in hemophilia.

What is the Effect of Bevacizumab on Cartilage and Synovium in a Rabbit Model of Hemophilic Arthropathy?

BACKGROUND

Hemophilic arthropathy can cause recurrent hemarthroses and severe damage to the synovium and articular cartilage. Previous studies have shown that vascular endothelial growth factor (VEGF) plays an essential role in neoangiogenesis. Bevacizumab, a monoclonal VEGF inhibitor, is used clinically to prevent angiogenesis. However, its effects on hemophilic arthropathy are unknown.

QUESTIONS/PURPOSES

Using a hemophilic arthropathy rabbit model, we asked: Does an intra-articular injection of bevacizumab (1) inhibit VEGF, (2) decrease signal intensity in dynamic contrast-enhanced MRI (DCE-MRI) as an assessment of capillary permeability and neoangiogenesis, (3) reduce cartilage damage, (4) reduce synovial changes, and (5) affect macroscopic changes during the development of hemophilic arthropathy?

METHODS

Twenty-five male New Zealand rabbits were divided into four groups. Eight knees from four rabbits were used as the control group. We used an established animal model for hemophilic arthropathy in the remaining 21 rabbits. Animals were assigned randomly to three groups with seven rabbits in each group. One group was used to establish mild arthropathy, and the other two were used to establish severe arthropathy. Autologous blood from the rabbits' ears was injected into the right and left knees twice per week for 8 weeks to represent mild arthropathy and for 16 weeks to represent severe arthropathy. In the mild arthropathy group, bevacizumab was injected into the right knee once every 2 weeks. Bevacizumab was injected into the right knee of rabbits in one of the severe arthropathy groups once every 2 weeks for 16 weeks, and intra-articular bevacizumab injections were administered to the right knees of rabbits in the other severe arthropathy group once every 2 weeks after the eighth week. An equal volume of 0.9% saline was injected into the left knee of rabbits in all arthropathy groups. To explore the efficacy of bevacizumab, joint diameters were quantitatively measured, and cartilage and synovial changes were examined. Degeneration of articular cartilage was evaluated with the semiquantitative Osteoarthritis Research Society International grading system. Synovial damage was analyzed with a semiquantitative microscopic scoring system. In addition, we evaluated perfusion and angiogenesis using DCE-MRI (quantitative signal intensity changes). Immunohistochemical testing was used to measure VEGF levels (analyzed by Western blotting).

RESULTS

Intra-articular bevacizumab treatment inhibited VEGF in our rabbit model of hemophilic arthropathy. VEGF protein expression levels were lower in the mild arthropathy group that received intra-articular bevacizumab (0.89 ± 0.45) than the mild arthropathy control group (1.41 ± 0.61) (mean difference -0.52 [95% CI -0.898 to -0.143]; p = 0.02). VEGF levels were lower in the severe arthropathy group that received treatment for 16 weeks (0.94 ± 0.27) than in the control knees (1.49 ± 0.36) (mean difference -0.55 [95% CI -0.935 to -0.161]; p = 0.01). In the severe arthropathy group, the Osteoarthritis Research Society International score indicating cartilage damage was lower in the group that received intra-articular bevacizumab treatment from the beginning than in the control group (median 17 [range 13 to 18] versus 18 [range 17 to 20]; difference of medians 1; p = 0.02). Additionally, the scores indicated synovial damage was lower in the group that received intra-articular bevacizumab treatment from the beginning than the control group (median 5 [range 4 to 9] versus 9 [range 8 to 12]; difference of medians 4; p = 0.02). The mean of mean values for signal intensity changes was higher in the nontreated severe groups than in the group of healthy knees. The signal intensity changes were higher in the severe arthropathy control groups (Groups BC and CC) (median 311.6 [range 301.4 to 361.2] and 315.1 [range 269.7 to 460.4]) than in the mild arthropathy control group (Group AC) (median 234.1 [range 212.5 to 304.2]; difference of medians 77.5 and 81, respectively; p = 0.02 and p = 0.04, respectively). In the severe arthropathy group, discoloration caused by hemosiderin deposition in the cartilage and synovium was more pronounced than in the mild arthropathy group. In the severe arthropathy group treated with intra-articular bevacizumab, joint diameters were smaller than in the control group (Group BT median 12.7 mm [range 12.3 to 14.0] versus Group BC median 14.0 mm [range 13.1 to 14.5]; difference of medians 1.3 mm; p = 0.02).

CONCLUSION

Hemarthrosis damages the synovial tissues and cartilage in the knees of rabbits, regardless of whether they are treated with intra-articular bevacizumab. However, intra-articular injection of bevacizumab may reduce cartilage and synovial damage in rabbits when treatment is initiated early during the development of hemophilic arthropathy.

CLINICAL RELEVANCE

If the findings in this study are replicated in larger-animal models that consider the limitations of our work, then a trial in humans might be appropriate to ascertain whether intra-articular injection of bevacizumab could reduce cartilage damage and synovial changes in patients with hemophilia whose hemarthroses cannot otherwise be controlled.

Iron homeostasis in arthropathies: From pathogenesis to therapeutic potential

Iron is an essential element for proper functioning of cells within mammalian organ systems; in particular, iron homeostasis is critical for joint health. Excess iron can induce oxidative stress damage, associated with the pathogenesis of iron-storage and ageing-related diseases. Therefore, iron levels in body tissues and cells must be tightly regulated. In the past decades, excess iron content within joints has been found in some patients with joint diseases including hemophilic arthropathy, hemochromatosis arthropathy, and osteoarthritis (OA). Currently, increased evidence has shown that iron accumulation is closely associated with multiple pathological changes of these arthropathies. This review summarizes system-level and intracellular regulation of iron homeostasis, and emphasizes the role of iron in synovial alterations, cartilage degeneration, and subchondral bone of several arthropathies. Of note, we discuss the potential link between iron homeostasis and OA pathogenesis. Finally, we discuss the therapeutic potential of maintaining iron homeostasis in these arthropathies.

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.

CRISPR/Cas9-mediated knockin of human factor IX into swine factor IX locus effectively alleviates bleeding in hemophilia B pigs

Hemophilia B is an X-linked recessive bleeding disorder caused by abnormalities in the coagulation factor IX gene. Without prophylactic treatment, patients experience frequent spontaneous bleeding episodes. Well-characterized animal models are valuable for determining the pathobiology of the disease and for testing novel therapeutic innovations. Here, we generated a porcine model of hemophilia B (HB) using a combination of CRISPR/Cas9 and somatic cell nuclear transfer. We also tested the possibility of HB therapy by gene insertion. Frequent spontaneous joint bleeding episodes that occurred in HB pigs allowed a thorough investigation of the pathological process of hemophilic arthropathy. In contrast to the HB pigs, which showed a severe bleeding tendency and joint damage, the transgenic pigs carrying human coagulation factor IX exhibited a partial improvement in bleeding. In summary, this study not only offers a translational HB model for exploring the pathological process of hemophilic arthropathy, but also provides a possibility for the permanent correction of hemophilia in the future by genome editing in situ.

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.

Initial joint bleed volume in a delayed on-demand treatment setup correlates with subsequent synovial changes in hemophilic mice

BACKGROUND

Hemophilic arthropathy is a debilitating morbidity of hemophilia caused by recurrent joint bleeds. We investigated if the joint bleed volume, before initiation of treatment, was linked to the subsequent degree of histopathological changes and the development of bone pathology in a mouse model of hemophilic arthropathy.

METHODS

FVIII knock-out (F8-KO) mice were dosed with a micro-CT blood pool agent prior to induction of hemarthrosis. Eight hours after induction, the bleed volume was quantified with micro computed tomography (micro-CT) and recombinant FVIII treatment initiated. On Day 8, inflammation in the knees was characterized by fluorescence molecular tomography. On Day 14, knee pathology was characterized by micro-CT and histopathology. In a second study, contrast agent was injected into the knee of wild-type (WT) mice, followed by histopathological evaluation on Day 14.

RESULTS

The average joint bleed volume before treatment was 3.9 mm3. The inflammation-related fluorescent intensities in the injured knees were significantly increased on Day 8. The injured knees had significantly increased synovitis scores, vessel counts, and areas of hemosiderin compared to un-injured knees. However, no cartilage- or bone pathology was observed. The bleed volume before initiation of treatment correlated with the degree of synovitis and was associated with high fluorescent intensity on Day 8. In F8-KO and WT mice, persistence of contrast agent in the joint elicited morphological changes.

CONCLUSION

When applying a delayed on-demand treatment regimen to hemophilic mice subjected to an induced knee hemarthrosis, the degree of histopathological changes on Day 14 reflected the bleed volume prior to initiation of treatment.

Exploring the Potential Feasibility of Intra-Articular Adeno-Associated Virus-Mediated Gene Therapy for Hemophilia Arthropathy

Hemophilia arthropathy (HA) represents the majority of morbidity in severe hemophilia patients, especially in resource-limited countries. Adeno-associated virus (AAV)-mediated gene therapy is showing promise for managing hemophilia. However, patients with neutralizing antibodies (NAbs) against AAV, and inhibitors to clotting factors, are excluded from such therapy. This study explored the feasibility of AAV-mediated local gene therapy for HA. Factor VIII knockout (FVIII^-/-) mice, with or without a FVIII inhibitor, were subjected to hemarthrosis induction and treated with either intravenous (IV) or intraarticular (IA) recombinant human factor VIII (rhFVIII). To investigate whether rhFVIII carried the risk to develop a FVIII inhibitor, FVIII^-/- mice were treated with three doses of IV or IA rhFVIII and inhibitor development was measured. In patients with established HA requiring synovial fluid aspiration, plasma, and synovial fluid were collected and measured for anti-AAV capsid IgG (serotypes 1-9 and 843) and NAbs for AAV843. IA rhFVIII provided better protection from synovitis compared with IV rhFVIII, with or without the FVIII inhibitor. While IV rhFVIII led to all FVIII^-/- mice developing an FVIII inhibitor (n = 31, median 4.9 Bethesda units [BU]/mL), only 50% of the mice developed a FVIII inhibitor by IA administration, and at a lower titer (median 0.55 BU/mL). In hemophilia patients, total anti-AAV IgG was lowest for AAV4 and AAV5, both in plasma and synovial fluid. Anti-AAV IgGs in synovial fluid for most samples were lower or similar to the plasma levels. These results show that direct IA rhFVIII administration yields better protection against bleeding-induced joint damage, even in the presence of an inhibitor antibody. IA rhFVIII delivery carried a lower risk of FVIII inhibitor formation compared with IV FVIII. The anti-AAV antibody level in synovial fluid was similar or lower than the plasma level, supporting the feasibility of local gene therapy for managing HA.

A Translational Study of TNF-Alpha Antagonists as an Adjunctive Therapy for Preventing Hemophilic Arthropathy

Repeated intra-articular hemorrhages lead to hemophilic arthropathy in severe hemophilia. Inflammation and pro-inflammatory cytokines (e.g., tumor necrosis factor alpha (TNFα)) might be involved in this pathogenesis. We hypothesized that anti-TNFα may provide adjuvant protection for hemophilic arthropathy management. We measured TNFα in synovial lavage from hemophilia mice subjected to hemarthrosis induction and synovial fluid from patients with hemophilic arthropathy (n = 5). In hemophilia mice, recurrent hemarthroses were induced, anti-TNFα was initiated either from day (D)7 after one hemarthrosis episode or D21 after three hemarthroses episodes (n ≥ 7/treatment group). In patients with hemophilic arthropathy (16 patients with 17 affected joints), a single dose of anti-TNFα was administered intra-articularly. Efficacy, characterized by synovial membrane thickness and vascularity, was determined. Elevated TNFα in synovial lavage was found in the hemophilia mice and patients with hemophilic arthropathy. Hemophilia mice subjected to three hemarthroses developed severe synovitis (Synovitis score of 6.0 ± 1.6). Factor IX (FIX) replacement alone partially improved the pathological changes (Synovitis score of 4.2 ± 0.8). However, anti-TNFα treatment initiated at D7, not D21, significantly provided protection (Synovitis score of 1.8 ± 0.9 vs. 3.9 ± 0.3). In patients with hemophilic arthropathy, intra-articular anti-TNFα significantly decreased synovial thickness and vascularity during the observed period from D7 to D30. Collectively, this preliminary study seems to indicate that TNFα may be associated with the pathogenicity of hemophilic arthropathy and anti-TNFα could provide adjuvant protection against hemophilic arthropathy. Further studies are required to confirm the preliminary results shown in this study.

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.

Curcumin: hopeful treatment of hemophilic arthropathy via inhibition of inflammation and angiogenesis

Introduction: Hemophilic arthropathy (HA) is a serious complication among hemophilic patients causing a wide range of morbidity due to the inflammatory reactions followed by repeated episodes of bleeding. This condition has recently been shown to be accompanied by angiogenesis. The cascade starts with iron accumulation leading to an increase in CD⁶⁸⁺ and CD^11b+ cells responsible for initiating the inflammation.Areas covered: During inflammation, different factors and cytokines such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor α (TNF-α) actively play parts in the pathogenesis of HA and also angiogenesis. It has been demonstrated that different pro-angiogenic and angiogenic factors such as hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), oxidative stress and matrix metalloproteinases (MMPs) are also important in the pathogenesis of HA. Curcumin is known for its strong anti-inflammatory and anti-angiogenic potentials. This agent is able to inhibit the mentioned inflammatory and angiogenic factors such as IL-1, IL-6, TNF-α, VEGF, MMPs, and HIF-1α. Also, as well as anti-angiogenic and anti-inflammatory activity, curcumin has a strong antioxidant potential and can decrease oxidative stress.Expert opinion: It seems that curcumin could be considered as a possible agent for the treatment of HA through inhibition of inflammation, oxidative stress, and angiogenesis.

Hemophilia A and B mice, but not VWF-/-mice, display bone defects in congenital development and remodeling after injury

While joint damage is the primary co-morbidity of hemophilia, osteoporosis and osteopenia are also observed. Coagulation factor VIII deficient (FVIII^−/−) mice develop an osteoporotic phenotype in the absence of induced hemarthrosis that is exacerbated two weeks after an induced joint injury. Here we have compared comprehensively the bone health of clotting factor VIII, factor IX, and Von Willebrand Factor knockout (FVIII^−/−, FIX^−/−, and VWF^−/− respectively) mice both in the absence of joint hemorrhage and following induced joint injury. We found FVIII^−/− and FIX^−/− mice, but not VWF^−/− mice, developmentally have an osteoporotic phenotype. Unilateral induced hemarthrosis causes further bone damage in both FVIII^−/− and FIX^−/− mice, but has little effect on VWF^−/− bone health, indicating that the FVIII.VWF complex is not required for normal bone remodeling in vivo. To further investigate the bone healing following hemarthrosis in hemophilia we examined a two week time course using microCT, serum chemistry, and histological analysis. Elevated ratio of osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL), increased osterix⁺ osteoblastic cells, and decreased smoothness of the cortical bone surface were evident within several days of injury, indicative of acute heterotopic mineralization along the cortical surface. This was closely followed by increased interleukin-6 (IL-6) levels, increased osteoclast numbers, and significant trabecular bone loss. Uncoupled and disorganized bone formation and resorption continued for the duration of the study resulting in significant deterioration of the joint. Further elucidation of the shared mechanisms underlying abnormal bone homeostasis in the absence of FVIII or FIX is needed to guide evidence-based approaches to the screening and treatment of the prevalent bone defects in hemophilia A and B.

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.

Prophylactic administration of glycoPEGylated factor IX provides protection and joint outcome superior to recombinant factor IX after induced joint bleeding

BACKGROUND

Following induced joint hemorrhage, hemophilia B results in the abnormal persistence of iron deposition, inflammation, and neovascularity of the synovial tissue, as well as deterioration of the bone articular surface and strength. Previously, we demonstrated that a factor IX (FIX) replacement protein with extended circulating FIX activity, glycoPEGylated FIX nonacog beta pegol (N9-GP), could improve synovial and osteochondral parameters in F9 knockout mice when administered after joint injury.

OBJECTIVE

We explored the use of N9-GP prior to unilateral joint hemorrhage and compared to unmodified recombinant FIX (rFIX).

METHODS

Pharmacodynamics, histology, and microcomputed tomography were used to assess the effects of prophylactic administration of glycoPEGylated FIX.

RESULTS

In comparison to rFIX, N9-GP significantly improved soft tissue histological parameters, as well as bone outcome at 2 weeks post injury, while performing equally in reduction of blood present in the joint space assessed 1 day after injury.

CONCLUSIONS

These results indicate that, in comparison to rFIX, the prophylactic use of extended half-life FIX provides superior protection from bleeding-induced joint damage, manifested by improved correction of histologic parameters.

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.

Defective TAFI activation in hemophilia A mice is a major contributor to joint bleeding

Joint bleeds are common in congenital hemophilia but rare in acquired hemophilia A (aHA) for reasons unknown. To identify key mechanisms responsible for joint-specific bleeding in congenital hemophilia, bleeding phenotypes after joint injury and tail transection were compared in aHA wild-type (WT) mice (receiving an anti-factor VIII [FVIII] antibody) and congenital HA (FVIII-/-) mice. Both aHA and FVIII-/- mice bled severely after tail transection, but consistent with clinical findings, joint bleeding was notably milder in aHA compared with FVIII-/- mice. Focus was directed to thrombin-activatable fibrinolysis inhibitor (TAFI) to determine its potentially protective effect on joint bleeding in aHA. Joint bleeding in TAFI-/- mice with anti-FVIII antibody was increased, compared with WT aHA mice, and became indistinguishable from joint bleeding in FVIII-/- mice. Measurements of circulating TAFI zymogen consumption after joint injury indicated severely defective TAFI activation in FVIII-/- mice in vivo, consistent with previous in vitro analyses in FVIII-deficient plasma. In contrast, notable TAFI activation was observed in aHA mice, suggesting that TAFI protected aHA joints against bleeding. Pharmacological inhibitors of fibrinolysis revealed that urokinase-type plasminogen activator (uPA)-induced fibrinolysis drove joint bleeding, whereas tissue-type plasminogen activator-mediated fibrinolysis contributed to tail bleeding. These data identify TAFI as an important modifier of hemophilic joint bleeding in aHA by inhibiting uPA-mediated fibrinolysis. Moreover, our data suggest that bleed protection by TAFI was absent in congenital FVIII-/- mice because of severely defective TAFI activation, underscoring the importance of clot protection in addition to clot formation when considering prohemostatic strategies for hemophilic joint bleeding.

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

Vascular remodelling is a prominent feature of haemophilic arthropathy (HA) that may underlie re-bleeding, yet the nature of vascular changes and underlying mechanisms remain largely unknown. Here, we aimed to characterize synovial vascular remodelling and vessel integrity after haemarthrosis, as well as temporal changes in inflammatory and tissue-reparative pathways. Thirty acutely painful joints in patients with haemophilia (PWH) were imaged by musculoskeletal ultrasound with Power Doppler (MSKUS/PD) to detect vascular abnormalities and bloody effusions. Nineteen out of 30 painful joint episodes in PWH were associated with haemarthrosis, and abnormal vascular perfusion was unique to bleeding joints. A model of induced haemarthrosis in factor VIII (FVIII)-deficient mice was used for histological assessment of vascular remodelling (α-smooth muscle actin [αSMA] expression), and monitoring of in vivo vascular perfusion and permeability by MSKUS/PD and albumin extravasation, respectively. Inflammatory (M1) and reparative (M2) macrophage markers were quantified in murine synovium over a 10-week time course by real-time polymerase chain reaction. The abnormal vascular perfusion observed in PWH was recapitulated in FVIII-deficient mice after induced haemarthrosis. Neovascularization and increased vessel permeability were apparent 2 weeks post-bleed in FVIII-deficient mice, after a transient elevation of inflammatory macrophage M1 markers. These vascular changes subsided by week 4, while vascular remodelling, evidenced by architectural changes and pronounced αSMA expression, persisted alongside a reparative macrophage M2 response. In conclusion, haemarthrosis leads to transient inflammation coupled with neovascularization and associated vascular permeability, while subsequent tissue repair mechanisms coincide with vascular remodelling. Together, these vascular changes may promote re-bleeding and HA progression.

Deferasirox limits cartilage damage following haemarthrosis in haemophilic mice

Joint bleeds in haemophilia result in iron-mediated synovitis and cartilage damage. It was evaluated whether deferasirox, an iron chelator, was able to limit the development of haemophilic synovitis and cartilage damage. Haemophilic mice were randomly assigned to oral treatment with deferasirox (30 mg/kg) or its vehicle (control) (30 mg/kg). Eight weeks after start of treatment, haemarthrosis was induced. After another five weeks of treatment, blood-induced synovitis and cartilage damage were determined. Treatment with deferasirox resulted in a statistically significant (p< 0.01) decrease in plasma ferritin levels as compared to the control group (823 ng/ml ± 56 and 1220 ng/ml ±114, respectively). Signs of haemophilic synovitis, as assessed by the Valentino score [range 0 (normal) – 10 (most affected)], were not different (p=0.52) when comparing the control group with the deferasirox group. However, deferasirox treatment resulted in a statistically significant (p< 0.01) reduction in cartilage damage, as assessed by the loss in Safranin O staining [range 0 (normal) – 6 (most affected)], when comparing the deferasirox group with the control group: score 2 (65.4 % vs 4.2 %), score 3 (26.9 % vs 4.2 %), score 4 (7.7 % vs 20.8 %), score 5 (0 % vs 54.2 %), and score 6 (0 % vs 16.7 %). Treatment with deferasirox limits cartilage damage following the induction of a haemarthrosis in haemophilic mice. This study demonstrates the role of iron in blood-induced cartilage damage. Moreover, these data indicate that iron chelation may be a potential prevention option to limit the development of haemophilic arthropathy.

A fusion protein of interleukin-4 and interleukin-10 protects against blood-induced cartilage damage in vitro and in vivo

Essentials Targeted treatment for hemophilic arthropathy, still causing significant morbidity, is lacking. This study evaluates the efficacy of a fusion of protein of interleukin(IL)-4 and IL-10. In vitro the fusion protein prevents blood-induced cartilage damage in a dose-dependent manner. In hemophilic mice, the IL4-10 fusion protein ameliorates cartilage damage upon joint bleeding.

SUMMARY

Background Joint damage still causes significant morbidity in hemophilia. It results from synovial inflammation and direct cartilage-degenerating properties of blood components. Interleukin (IL)-4 and IL-10 have been shown to protect cartilage from blood-induced damage. Recently an IL4-10 fusion protein has been developed to combine the function of IL-4 and IL-10 and increase their bioavailability. Objectives In this study we evaluate whether this IL4-10 fusion protein protects against blood-induced joint damage. Methods In vitro, human cartilage explants were exposed to whole blood and simultaneously to a broad concentration range of the IL4-10 fusion protein. Effects on cartilage matrix turnover were compared with the individual cytokines. Moreover, the influence of the fusion protein and its individual components on IL-1β and IL-6 production was investigated. In hemophilia A mice, the effect of intra-articular treatment on synovitis and cartilage damage resulting from joint bleeding was evaluated by histochemistry. Results In vitro, the fusion protein prevented blood-induced cartilage damage in a dose-dependent manner, with equal effectiveness to the combination of the separate cytokines. In whole blood cultures 10 ng mL-1 fusion protein completely blocked the production of IL-1β and IL-6 by monocytes/macrophages. In hemophilic mice, intra-articular injection of IL-4 and IL-10 did not influence synovitis or cartilage degeneration. In contrast, equimolar amounts of the fusion protein attenuated cartilage damage upon repeated joint bleeding, although synovial inflammation was hardly affected. Conclusions Overall, this study shows that the IL4-10 fusion protein prevents blood-induced cartilage damage in vitro and ameliorates cartilage degeneration upon joint bleeding in hemophilic mice.

Using mouse models to investigate the pathophysiology, treatment, and prevention of post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) is defined by its development after joint injury. Factors contributing to the risk of PTOA occurring, the rate of progression, and degree of associated disability in any individual, remain incompletely understood. What constitutes an "OA-inducing injury" is not defined. In line with advances in the traumatic brain injury field, we propose the scope of PTOA-inducing injuries be expanded to include not only those causing immediate structural damage and instability (Type I), but also those without initial instability/damage from moderate (Type II) or minor (Type III) loading severity. A review of the literature revealed this full spectrum of potential PTOA subtypes can be modeled in mice, with 27 Type I, 6 Type II, and 4 Type III models identified. Despite limitations due to cartilage anatomy, joint size, and bio-fluid availability, mice offer advantages as preclinical models to study PTOA, particularly genetically modified strains. Histopathology was the most common disease outcome, cartilage more frequently studied than bone or synovium, and meniscus and ligaments rarely evaluated. Other methods used to examine PTOA included gene expression, protein analysis, and imaging. Despite the major issues reported by patients being pain and biomechanical dysfunction, these were the least commonly measured outcomes in mouse models. Informative correlations of simultaneously measured disease outcomes in individual animals, was rarely done in any mouse PTOA model. This review has identified knowledge gaps that need to be addressed to increase understanding and improve prevention and management of PTOA. Preclinical mouse models play a critical role in these endeavors. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:424-439, 2017.

Abnormal joint and bone wound healing in hemophilia mice is improved by extending factor IX activity after hemarthrosis

Wound healing requires interactions between coagulation, inflammation, angiogenesis, cellular migration, and proliferation. Healing in dermal wounds of hemophilia B mice is delayed when compared with hemostatically normal wild-type (WT) mice, with abnormal persistence of iron deposition, inflammation, and neovascularity. We observed healing following induced joint hemorrhage in WT and factor IX (FIX) knockout (FIX^-/-) mice, examining also parameters previously studied in an excisional skin wound model. Hemostatically normal mice tolerated this joint bleeding challenge, cleared blood from the joint, and healed with minimal pathology, even if additional autologous blood was injected intra-articularly at the time of wounding. Following hemarthrosis, joint wound healing in hemophilia B mice was impaired and demonstrated similar abnormal histologic features as previously described in hemophilic dermal wounds. Therefore, studies of pathophysiology and therapy of hemophilic joint bleeding performed in hemostatically normal animals are not likely to accurately reflect the healing defect of hemophilia. We additionally explored the hypothesis that the use of a FIX replacement protein with extended circulating FIX activity could improve synovial and osteochondral wound healing in hemophilic mice, when compared with treatment with unmodified recombinant FIX (rFIX) in the established joint bleeding model. Significantly improved synovial wound healing and preservation of normal osteochondral architecture are achieved by extending FIX activity after hemarthrosis using glycoPEGylated FIX when compared with an equivalent dose of rFIX. These results suggest that treating joint bleeding only until hemostasis is achieved may not result in optimal joint healing, which is improved by extending factor activity.

Orthopedic disorders of the knee in hemophilia: A current concept review

The knee is frequently affected by severe orthopedic changes known as hemophilic arthropathy (HA) in patients with deficiency of coagulation factor VIII or IX and thus this manuscript seeks to present a current perspective of the role of the orthopedic surgeon in the management of these problems. Lifelong factor replacement therapy (FRT) is optimal to prevent HA, however adherence to this regerous treatment is challenging leading to breakthrough bleeding. In patients with chronic hemophilic synovitis, the prelude to HA, radiosynovectomy (RS) is the optimal to ameliorate bleeding. Surgery in people with hemophilia (PWH) is associated with a high risk of bleeding and infection, and must be performed with FRT. A coordinated effort including orthopedic surgeons, hematologists, physical medicine and rehabilitation physicians, physiotherapists and other team members is key to optimal outcomes. Ideally, orthopedic procedures should be performed in specialized hospitals with experienced teams. Until we are able to prevent orthopedic problems of the knee in PWH will have to continue performing orthopedic procedures (arthrocentesis, RS, arthroscopic synovectomy, hamstring release, arthroscopic debridement, alignment osteotomy, and total knee arthroplasty). By using the aforementioned procedures, the quality of life of PWH will be improved.

The F8(-/-) rat as a model of hemophilic arthropathy

Essentials Validating the F8 rat as a new intermediate-size animal model of hemophilic arthropathy. Factor VIII (FVIII) treated F8(-/-) rats suffered induced hemarthrosis analyzed by histopathology. F8 (-/-) animals develop hemophilic arthropathy upon hemarthrosis, preventable by FVIII treatment. The F8 (-/-) rat presents as a new pharmacologic model of hemophilic arthropathy.

SUMMARY

Background Translational animal models of hemophilia are valuable for determining the pathobiology of the disease and its co-morbidities (e.g. hemophilic arthropathy, HA). The biologic mechanisms behind the development of HA, a painful and debilitating condition, are not completely understood. We recently characterized a F8(-/-) rat, which could be a new preclinical model of HA. Objectives To establish the F8(-/-) rat as a model of HA by determining if the F8(-/-) rat develops HA resembling human HA after an induced joint bleed and whether a second joint bleed causes further disease progression. Methods Wild-type and F8(-/-) rats were treated with vehicle or recombinant human factor VIII (rhFVIII) prior to a needle-induced joint bleed. Joint swelling was measured prior to injury, the following 7 days and upon euthanasia. Histologic sections of the joint were stained, and athropathic changes identified and scored with regard to synovitis, bone remodelling, cartilage degradation and hemosiderin deposition. Results Vehicle-treated F8(-/-) rats experienced marked joint swelling and developed chronic degenerative joint changes (i.e. fibrosis of the subsynovial membrane, chondrocyte loss and excessive bone remodeling). Treatment with rhFVIII reduced or prevented swelling and degenerative joint changes, returning the F8(-/-) animals to a wild-type phenotype. Conclusion The hemophilic phenotype of the F8(-/-) rat resulted in a persistent hemarthrosis following an induced joint bleed. This caused development of HA resembling human HA, which was prevented by rhFVIII treatment, confirming the potential of the F8(-/-) rat as a model of HA.

Vascular remodeling underlies rebleeding in hemophilic arthropathy

Hemophilic arthropathy is a debilitating condition that can develop as a consequence of frequent joint bleeding despite adequate clotting factor replacement. The mechanisms leading to repeated spontaneous bleeding are unknown. We investigated synovial, vascular, stromal, and cartilage changes in response to a single induced hemarthrosis in the FVIII-deficient mouse. We found soft-tissue hyperproliferation with marked induction of neoangiogenesis and evolving abnormal vascular architecture. While soft-tissue changes were rapidly reversible, abnormal vascularity persisted for months and, surprisingly, was also seen in uninjured joints. Vascular changes in FVIII-deficient mice involved pronounced remodeling with expression of α-Smooth Muscle Actin (SMA), Endoglin (CD105), and vascular endothelial growth factor, as well as alterations of joint perfusion as determined by in vivo imaging. Vascular architecture changes and pronounced expression of α-SMA appeared unique to hemophilia, as these were not found in joint tissue obtained from mouse models of rheumatoid arthritis and osteoarthritis and from patients with the same conditions. Evidence that vascular changes in hemophilia were significantly associated with bleeding and joint deterioration was obtained prospectively by dynamic in vivo imaging with musculoskeletal ultrasound and power Doppler of 156 joints (elbows, knees, and ankles) in a cohort of 26 patients with hemophilia at baseline and during painful episodes. These observations support the hypothesis that vascular remodeling contributes significantly to bleed propagation and development of hemophilic arthropathy. Based on these findings, the development of molecular targets for angiogenesis inhibition may be considered in this disease.

Employing a gain-of-function factor IX variant R338L to advance the efficacy and safety of hemophilia B human gene therapy: preclinical evaluation supporting an ongoing adeno-associated virus clinical trial

Vector capsid dose-dependent inflammation of transduced liver has limited the ability of adeno-associated virus (AAV) factor IX (FIX) gene therapy vectors to reliably convert severe to mild hemophilia B in human clinical trials. These trials also identified the need to understand AAV neutralizing antibodies and empty AAV capsids regarding their impact on clinical success. To address these safety concerns, we have used a scalable manufacturing process to produce GMP-grade AAV8 expressing the FIXR338L gain-of-function variant with minimal (<10%) empty capsid and have performed comprehensive dose-response, biodistribution, and safety evaluations in clinically relevant hemophilia models. The scAAV8.FIXR338L vector produced greater than 6-fold increased FIX specific activity compared with wild-type FIX and demonstrated linear dose responses from doses that produced 2-500% FIX activity, associated with dose-dependent hemostasis in a tail transection bleeding challenge. More importantly, using a bleeding model that closely mimics the clinical morbidity of hemophilic arthropathy, mice that received the scAAV8.FIXR338L vector developed minimal histopathological findings of synovitis after hemarthrosis, when compared with mice that received identical doses of wild-type FIX vector. Hemostatically normal mice (n=20) and hemophilic mice (n=88) developed no FIX antibodies after peripheral intravenous vector delivery. No CD8(+) T cell liver infiltrates were observed, despite the marked tropism of scAAV8.FIXR338L for the liver in a comprehensive biodistribution evaluation (n=60 animals). With respect to the role of empty capsids, we demonstrated that in vivo FIXR338L expression was not influenced by the presence of empty AAV particles, either in the presence or absence of various titers of AAV8-neutralizing antibodies. Necropsy of FIX(-/-) mice 8-10 months after vector delivery revealed no microvascular or macrovascular thrombosis in mice expressing FIXR338L (plasma FIX activity, 100-500%). These preclinical studies demonstrate a safety:efficacy profile supporting an ongoing phase 1/2 human clinical trial of the scAAV8.FIXR338L vector (designated BAX335).

Antiplasmin, but not amiloride, prevents synovitis and cartilage damage following hemarthrosis in hemophilic mice

BACKGROUND

Blood-induced joint damage is characterized by synovitis and cartilage damage. Recently, we demonstrated that joint bleeding in hemophilic mice results in elevated synovial levels of urokinase plasminogen activator (u-PA) and plasmin, and in plasmin-mediated cartilage damage.

OBJECTIVE

To evaluate whether treatment with amiloride (an inhibitor of u-PA) or antiplasmin attenuates synovitis and cartilage damage following joint bleeding in hemophilic mice.

METHODS

Following the induction of joint bleeding, hemophilic mice were randomized between daily oral treatment with amiloride (1 mg kg⁻¹) or control, or weekly intra-articular treatment with amiloride (2.5 mg mL⁻¹), antiplasmin (2.5 mg mL⁻¹), or control. After 5 weeks of treatment, synovitis and cartilage damage were determined on hematoxylin and eosin-stained (Valentino score) and Safranin O-stained sections, respectively.

RESULTS

No effects of oral and intra-articular treatment with amiloride were found. In contrast, intra-articular treatment with antiplasmin resulted in significant (P < 0.01) reductions in both synovitis (score 1, 11.1% vs. 0%; score 2, 11.1% vs. 4.2%; score 3, 61.1% vs. 16.7%; score 4, 5.6% vs. 29.2%; score 5, 11.1% vs. 20.8%; score 6, 7.7% vs. 8.3%; score 7, 0% vs. 8.3%; and score 8, 0% vs. 12.5%) and cartilage damage (score 2, 10% vs. 8.3%; score 3, 50% vs. 12.5%; score 4, 30% vs. 33.3%; score 5, 10% vs. 33.3%; and score 6, 0% vs. 16.7%) as compared with controls.

CONCLUSIONS

Intra-articular treatment with antiplasmin (but not amiloride) following joint bleeding prevented synovitis and cartilage damage in hemophilic mice. These data offer promise for the use of antiplasmin as a new therapeutic intervention for patients who suffer from joint bleeds despite administration of clotting factor.

IL-6 receptor antagonist as adjunctive therapy with clotting factor replacement to protect against bleeding-induced arthropathy in hemophilia

BACKGROUND

The most common morbidity that results from hemophilia is bleeding-induced hemophilic arthropathy (HA), which once established may not be interrupted completely even by prophylactic clotting factor replacement. Specific therapies to oppose inflammatory cytokines, including Interleukin 6 (IL-6) receptor antagonists, have become important in the management of inflammatory arthritides.

OBJECTIVES

We investigated combining therapy using MR16-1, a rat IgG antibody directed against mouse IL-6 receptor (anti-IL-6R), with factor VIII (FVIII) replacement to protect against bleeding-induced arthropathy in hemophilia A mice.

METHODS

Three recurrent hemarthroses were induced in the knee joint capsule of FVIII knockout mice. Treatment at the time of each hemorrhage included either: no treatment; FVIII replacement given at the time of hemorrhage; FVIII replacement at hemorrhage plus anti-IL-6R as 4-weekly injections; FVIII replacement with non-specific control antibody (rat IgG); and anti-IL-6R alone without FVIII replacement. Six weeks following the first hemarthosis, joints were harvested and histopathology was scored for synovitis, for cartilage integrity and for macrophage infiltration.

RESULTS

Animals that received anti-IL-6R as an adjunct to FVIII replacement demonstrated the best survival and the least acute joint swelling and pathology on histologic examination of the synovium and cartilage (P < 0.05 for each parameter). All histopathologic parameters in the mice receiving FVIII+anti-IL-6R were limited and were comparable to findings in injured hemostatically normal mice. The major benefits of adjunctive anti-IL-6R were decreasing synovial hyperplasia, hemosiderin deposition and macrophage infiltration.

CONCLUSIONS

Short-course specific inhibition of inflammatory cytokines as an adjunct to replacement hemostasis may be an approach to minimize hemophilic joint degeneration.

Development and definition of a simplified scanning procedure and scoring method for Haemophilia Early Arthropathy Detection with Ultrasound (HEAD-US)

The aim of this study was to develop a simplified ultrasound scanning procedure and scoring method, named Haemophilia Early Arthropathy Detection with UltraSound [HEAD-US], to evaluate joints of patients with haemophilic arthropathy. After an initial consensus-based process involving a multidisciplinary panel of experts, three comprehensive and evidence-based US scanning procedures to image the elbow, knee and ankle were established with the aim to increase sensitivity in detection of early signs of joint involvement while keeping the technique easy and quick to perform. Each procedure included systematic evaluation of synovial recesses and selection of a single osteochondral surface for damage analysis. Based on expert consensus, a simplified scoring system based on an additive scale was created to define the joint status and, in perspective, to offer a tool to evaluate disease progression and monitor the result of treatment in follow-up studies.

A single intra-articular injection with IL-4 plus IL-10 ameliorates blood-induced cartilage degeneration in haemophilic mice

The combination of interleukin (IL)-4 and IL-10 protects against blood-induced cartilage damage in vitro. It has been hypothesized that the combination of these cytokines is effective if applied early in the process of cartilage damage. The present study investigated whether a single intra-articular injection of IL-4 plus IL-10 immediately after a joint bleed limits cartilage damage in an in vivo haemophilia mouse model of blood-induced joint damage. Factor VIII knockout mice with severe haemophilia A were punctured once with a needle below the patella to induce a joint haemorrhage. Subsequently IL-4 plus IL-10 (n = 24) or vehicle (n = 24) was injected intra-articularly. After 35 days, the time needed for development of detectable joint degeneration, knee joints were examined for cartilage damage by macroscopic and microscopic evaluation. A single intra-articular injection of IL-4 plus IL-10 ameliorated progression of cartilage degeneration caused by a single joint bleed to a certain extent. No effect on inflammation was observed at this time point. A single intra-articular injection of IL-4 plus Il-10 directly after a single joint bleed limits progression of cartilage degeneration over time. Improved bioavailability (half-life) of both cytokines might improve their protective ability in the development of cartilage degeneration, and probably also inflammation.

Animal models of hemophilia

The X-linked bleeding disorder hemophilia is caused by mutations in coagulation factor VIII (hemophilia A) or factor IX (hemophilia B). Unless prophylactic treatment is provided, patients with severe disease (less than 1% clotting activity) typically experience frequent spontaneous bleeds. Current treatment is largely based on intravenous infusion of recombinant or plasma-derived coagulation factor concentrate. More effective factor products are being developed. Moreover, gene therapies for sustained correction of hemophilia are showing much promise in preclinical studies and in clinical trials. These advances in molecular medicine heavily depend on availability of well-characterized small and large animal models of hemophilia, primarily hemophilia mice and dogs. Experiments in these animals represent important early and intermediate steps of translational research aimed at development of better and safer treatments for hemophilia, such a protein and gene therapies or immune tolerance protocols. While murine models are excellent for studies of large groups of animals using genetically defined strains, canine models are important for testing scale-up and for long-term follow-up as well as for studies that require larger blood volumes.

Unique strategies for therapeutic gene transfer in haemophilia A and haemophilia BWFH State-of-the-Art Session on Therapeutic Gene Transfer Buenos Aires, Argentina

SUMMARY

Gene therapy of haemophilia has been initiated through a number of approaches including expression in muscle, liver and omental implanted fibroblasts, or i.v. injection of an expression construct under the control of a ubiquitous promoter. In all these approaches, the goal was to have factor VIII (FVIII) or factor IX (FIX) synthesized so that it restored the levels of the missing protein in blood. The three talks in this session are totally, or at least in part, directed at strategies that may be clinically effective even in the absence of correction of the missing plasma clotting factor, although the haematopoietic stem cell or blood outgrowth endothelial cell therapy could achieve plasma correction as well. Two of the approaches achieve localized coagulation factor expression without necessarily correcting the systemic defect--one is with synthesis of FVIII or FIX within the joint space and the other is with the local release of FVIII (or FIX) by platelets at the site of vascular injury. All of the three approaches have demonstrated efficacy in small animal models and are now the subject of larger animal studies. None has yet to progress to human trials.

Hemophilic synovitis: factor VII and the potential role of extravascular factor VIIa

The initiation of coagulation via tissue factor/factor VIIa is relatively weak in normal synovium and joint tissues, so that hemophilic patients with additional deficiency of the intrinsic pathway of coagulation are especially at risk for joint bleeding and the development of hemophilic synovitis. The inflamed joint that results from recurrent bleeding-induced injury, however, may be an environment in which pharmacologic doses of factor VIIa have potentially greater procoagulant action than in the uninjured joint. There is accumulating evidence suggesting that coagulation factors in the extravascular space, and not only circulating plasma factors, have the potential to contribute to hemostatic protection of joints. The potential role of extravascular factor VIIa is considered.

Prevention of haemarthrosis in a murine model of acute joint bleeding

Preservation of normal joint function in patients with haemophilia is a goal of modern therapy. Regular injections of anti-haemophilic factor concentrate reduce the risk of joint bleeding, the optimal regimen for which remains under investigation. The goals of the experiment described here are: (i) to assess the capacity of a murine model of severe haemophilic arthropathy to predict the likelihood of success of a test product to prevent joint bleeding and the complications that follow and (ii) to compare the effectiveness of recombinant human activated factor VII (rFVIIa) to recombinant human factor VIII (rFVIII) to prevent acute joint bleeding in the mouse model of haemarthrosis. Mice lacking expression of FVIII received a single intravenous injection of human rFVIII (280 U kg(-1)), rFVIIa (10 mg kg(-1)) or vehicle prior to blunt trauma injury to the knee joint. Mice receiving rFVIII and rFVIIa developed less injury-induced joint bleeding, swelling and loss of range of motion compared to mice pretreated with vehicle. Despite the reduction in clinical symptoms, synovial hyperplasia was evident in all groups after 7 days although less pronounced in mice receiving rFVIII and rFVIIa. The data under these experimental conditions demonstrate: (i) that this model can be used to evaluate novel therapies designed to prevent joint bleeding (prophylaxis) and (ii) both rFVIII and rFVIIa reduced acute haemarthrosis but did not completely prevent synovitis, the sequelae of blood induced joint injury.

Physiopathology of haemophilic arthropathy

Haemophilic arthropathy, which shares some clinical and biological injury characteristics with rheumatoid arthritis, is characterized by two main features: chronic proliferative synovitis and cartilage destruction. It is the consequence of repeated extravasation of blood into joint cavities, but its exact pathogenesis, particularly with regard to early changes in the joint, is still incompletely understood. This review presents recent findings obtained in experiments performed in vitro and using animal models, which have improved our knowledge of the pathogenesis of haemophilic arthropathy. These experimental studies show that haemophilic arthropathy is a multifactorial event in which the deposit of iron in the joints appears to exert a central role. First, iron may promote the apoptosis of chondrocytes by catalysing the formation of oxygen metabolites; this may explain the fact that intra-articular blood exerts a directly harmful effect on cartilage before, and independent of synovial changes. Secondly, iron may also act on the synovial membrane by favouring its proliferation through the induction of proto-oncogenes involved in cellular proliferation and stimulation of inflammatory cytokines as well as abrogation of apoptosis. These two processes, one degenerative and cartilage-mediated, the other inflammatory and synovium-mediated could occur in parallel or sequentially. Overall, it may be expected that these experimental results will yield new therapeutic strategies capable of effectively preventing the occurrence of this still serious and common complication in patients with severe haemophilia.

Intraarticular factor IX protein or gene replacement protects against development of hemophilic synovitis in the absence of circulating factor IX

Hemophilic bleeding into joints causes synovial and microvascular proliferation and inflammation (hemophilic synovitis) that contribute to end-stage joint degeneration (hemophilic arthropathy), the major morbidity of hemophilia. New therapies are needed for joint deterioration that progresses despite standard intravenous (IV) clotting factor replacement. To test whether factor IX within the joint space can protect joints from hemophilic synovitis, we established a hemophilia B mouse model of synovitis. Factor IX knockout (FIX(-/-)) mice received a puncture of the knee joint capsule with a needle to induce hemarthrosis; human factor IX (hFIX) was either injected through the needle into the joint space (intraarticularly) or immediately delivered IV. FIX(-/-) mice receiving intraarticular FIX protein were protected from synovitis compared with mice receiving same or greater doses of hFIX IV. Next, adeno-associated virus (AAV) gene transfer vectors expressing hFIX were injected into knee joints of FIX(-/-) mice. Joints treated with 10(10) vector genomes (vg)/joint AAV2-, AAV5-, or AAV8-hFIX or 2.5 x 10(9) vg/joint AAV5-hFIX developed significantly fewer pathologic changes 2 weeks after injury compared with the pathology of control injured contralateral hind limbs. Extravascular factor activity and joint-directed gene transfer may ameliorate hemophilic joint destruction, even in the absence of circulating FIX.