Pathology of experimental haemarthrosis

Synovitis and synovectomy in haemophilia

Joint bleeds cause major morbidity in haemophilia patients. The synovial tissue is responsible for removal of blood remnants from the joint cavity. But blood components, especially iron, lead to a series of changes in the synovial tissue: inflammation, proliferation and neovascularization. These changes make the synovium vulnerable to subsequent bleeding and as such a vicious cycle of bleeding-synovitis-bleeding may develop leading to chronic synovitis. The initial step in the treatment is adequate clotting factor supplementation and immediate physiotherapeutic involvement. If these measures fail, synovectomy may be indicated. Non-surgical options are chemical and radioactive synovectomy. This is a relatively non-invasive procedure to do synovectomy, leading to a reduction in pain and joint bleeds. Radioactive synovectomy seems more effective than chemical synovectomy in larger joints. Surgical options are open and arthroscopic synovectomy. Open synovectomy has been found to decrease the incidence of breakthrough bleeds but at the cost of loss of joint motion. Use of arthroscopic synovectomy has been advocated to reduce bleeding episodes with less morbidity to extra-articular tissue and preservation of joint motion. Use of a continuous passive motion (CPM) machine and early mobilization can decrease the postoperative stiffness and promote early recovery. This review addresses the current understanding of synovitis and its treatment options with specific emphasis on chemical and radioactive synovectomy and surgical options.

Pathophysiology of Hemophilic Arthropathy

Spontaneous joint bleeding and repeated hemarthroses lead to hemophilic arthropathy—a debilitating disease with a significant negative impact on mobility and quality of life. Iron, cytokines, and angiogenic growth factors play a pivotal role in the onset of the inflammatory process that involves the synovial tissue, articular cartilage, and subchondral bone, with early damages and molecular changes determining the perpetuation of a chronic inflammatory condition. Synovitis is one of the earliest complications of hemarthrosis, and is characterized by synovial hypertrophy, migration of inflammatory cells, and a high degree of neo-angiogenesis with subsequent bleeding. The pathogenic mechanisms and molecular pathways by which blood in the joint cavity causes articular cartilage and subchondral bone destruction have yet to be fully elucidated. Both cytokines and matrix metalloproteinases and hydroxyl radicals may induce chondrocyte apoptosis. Members of the tumor necrosis factor receptor superfamily (such as the molecular triad: osteoprotegerin—OPG; receptor activator of nuclear factor κB—RANK; RANK ligand—RANKL) seem instead to play a major role in the inflammatory process. These pathogenic processes interact with each other and ultimately lead to a fibrotic joint and the disabling condition characteristic of hemophilic arthropathy.

Advances and challenges in hemophilic arthropathy

Hemophilic arthropathy is a form of joint disease that develops secondary to joint bleeding and presents with synovial hypertrophy, cartilage and bony destruction. The arthropathy can develop despite clotting factor replacement and is especially disabling in the aging population. Pathobiological tissue changes are triggered by release of hemoglobin and iron deposition in the joint, but the sequence of events and the molecular mechanisms resulting in joint deterioration are incompletely understood. Treatment options other than clotting factor replacement are limited. Improvements in the treatment of hemophilia necessitate a better understanding of the processes that lead to this disabling condition and better diagnostic tools. Towards that end, studies of the molecular mechanisms leading to the arthropathy, as well as the development of sensitive imaging techniques and biomarkers are needed. These will pave the way to identify the cause of acute pain such as joint bleeding or synovitis, detect early, potentially reversible structural changes, and predict progression of disease. This review describes current imaging techniques and the development of high resolution musculoskeletal ultrasound with power Doppler to afford point-of-care diagnosis and management, the potential utility of diagnostic biomarkers, and summarizes our current knowledge of the pathobiology of hemophilic arthropathy.

Quantitative versus semiquantitative MR imaging of cartilage in blood-induced arthritic ankles: preliminary findings

BACKGROUND

Recent advances in hemophilia prophylaxis have raised the need for accurate noninvasive methods for assessment of early cartilage damage in maturing joints to guide initiation of prophylaxis. Such methods can either be semiquantitative or quantitative. Whereas semiquantitative scores are less time-consuming to be performed than quantitative methods, they are prone to subjective interpretation.

OBJECTIVE

To test the feasibility of a manual segmentation and a quantitative methodology for cross-sectional evaluation of articular cartilage status in growing ankles of children with blood-induced arthritis, as compared with a semiquantitative scoring system and clinical-radiographic constructs.

MATERIALS AND METHODS

Twelve boys, 11 with hemophilia (A, n = 9; B, n = 2) and 1 with von Willebrand disease (median age: 13; range: 6-17), underwent physical examination and MRI at 1.5 T. Two radiologists semiquantitatively scored the MRIs for cartilage pathology (surface erosions, cartilage loss) with blinding to clinical information. An experienced operator applied a validated quantitative 3-D MRI method to determine the percentage area of denuded bone (dAB) and the cartilage thickness (ThCtAB) in the joints' MRIs. Quantitative and semiquantitative MRI methods and clinical-radiographic constructs (Hemophilia Joint Health Score [HJHS], Pettersson radiograph scores) were compared.

RESULTS

Moderate correlations were noted between erosions and dAB (r = 0.62, P = 0.03) in the talus but not in the distal tibia (P > 0.05). Whereas substantial to high correlations (r range: 0.70-0.94, P < 0.05) were observed between erosions, cartilage loss, HJHS and Pettersson scores both at the distal tibia and talus levels, moderate/borderline substantial (r range: 0.55-0.61, P < 0.05) correlations were noted between dAB/ThCtAB and clinical-radiographic constructs.

CONCLUSION

Whereas the semiquantitative method of assessing cartilage status is closely associated with clinical-radiographic scores in cross-sectional studies of blood-induced arthropathy, quantitative measures provide independent information and are therefore less applicable for that research design.

The effect of secondary prophylaxis versus episodic treatment on the range of motion of target joints in patients with haemophilia

This study prospectively compared the effect of secondary prophylaxis to episodic treatment on target joint (TJ) range of motion (ROM), number of joint haemorrhages and new TJ development in patients with moderate or severe haemophilia. Two-hundred and eighty-six males, 17% in prophylaxis, 83% in episodic treatment group, participating in the Centers for Disease Control and Prevention's Universal Data Collection project, fulfilled inclusion criteria: age >2 years at enrollment, free of TJs at enrollment, developed at least one TJ after enrollment, and received either prophylaxis or episodic treatment continuously for two follow-up visits after TJ development. The outcomes of interest - percentage change in TJ ROM, number of joint haemorrhages and new TJ development, were modelled using multivariate linear, Poisson and logistic regression techniques respectively. Individuals who received secondary prophylaxis in comparison to episodic treatment were younger at TJ development (P < 0.01); there was no difference in the decrease in TJ ROM between the two groups (P = 0.9). Factors significantly associated with a higher rate of haemarthroses included episodic treatment, severe haemophilia, age >5 years at TJ development, obesity and inhibitor negative status. Secondary prophylaxis significantly decreased haemarthroses but was not associated with a significant improvement in TJ ROM or with new TJ development.

Wound healing in haemophilia--breaking the vicious cycle

Our group has been studying how haemostasis interacts with repair processes and also how to optimize treatment of bleeding disorders in a mouse model of haemophilia B. We have found that cutaneous wounds heal more slowly in haemophilic mice than in wild-type mice, and also exhibit histological abnormalities, even after closure of the skin defect. The haemophilic wounds showed reduced influx of inflammatory cells and increased angiogenesis. Even after surface closure, the haemophilic animals experienced repeated episodes of re-bleeding and progressive accumulation of iron in the wound bed and deeper tissues. A dose of replacement or bypassing therapy sufficient to establish initial haemostasis did not normalize wound healing. In fact, daily dosing for 7 days was required to normalize wound closure. Thus, normal healing requires adequate haemostatic function for an extended period of time. We have hypothesized that this is because angiogenesis during healing predisposes to bleeding, especially in the setting where haemostasis is impaired. Thus, normalizing haemostasis, until the process of angiogenesis has resolved, may be required to prevent re-bleeding and additional tissue damage.

IL-1 beta, IL-6, KC and MCP-1 are elevated in synovial fluid from haemophilic mice with experimentally induced haemarthrosis

The hallmark of haemophilia is the joint morbidity resulting from haemarthrosis that accounts for the majority of the bleeds. The exact mechanisms underlying changes are not fully elucidated. Cytokines are speculated to be involved in the progression and in vitro studies have confirmed the presence of elevated levels of cytokines in synovial tissue and cartilage from patients with haemophilic synovitis. In this study, the presence of selected cytokines in synovial fluid from haemophilia A mice with experimentally induced haemarthroses treated with rFVIII, rFVIIa and an rFVIIa analogue were investigated. Ten cytokines previously shown to be involved in arthritic syndromes were evaluated. Interleukin (IL)-1 beta, IL-2, IL-4, IL-6, IL-10, IL-17, Tumor Necrosis Factor-alpha (TNF- alpha), keratinocyte-derived chemokine (KC), Regulated upon Activation, Normal T cell Expressed and Secreted (RANTES) and monocyte chemotactic protein-1 (MCP-1) were included. In this article, we demonstrate, for the first time, that bleeding in knee joints of haemophilia A mice resulted in correlated increased levels of the pro-inflammatory cytokines: IL-1 beta, IL-6, KC and the MCP-1 in synovial fluid. These results suggest an important role of MCP-1 in the recruitment of monocytes and furthermore that the inflamed synovium releases IL-1 beta, IL-6 and KC, which in turn might contribute to further progression of the inflammatory process.

Immunotherapy against APP β-Secretase Cleavage Site Improves Cognitive Function and Reduces Neuroinflammation in Tg2576 Mice without a Significant Effect on Brain Aβ Levels

BACKGROUND/OBJECTIVES

Active and passive immunization methodologies against amyloid-beta (Abeta) are employed to clear and reduce cerebral Abetatowards treatment of Alzheimer's disease (AD) patients. The therapeutic potential of these antibodies in AD patients is limited because of adverse inflammatory reactions and cerebral hemorrhage, which are associated with the treatment. We propose a novel approach to inhibit Abeta production via antibodies against the beta-secretase cleavage site of the amyloid precursor protein (APP). Such an approach limits APP processing by beta-secretase, mainly through the endocytic pathway, and overcomes some of the limitations of BACE inhibition. Anti-APP beta-site antibodies, tested in a cellular model expressing wild-type APP, were found to bind full-length APP, internalize into the cells and interfere with BACE activity, inhibiting both intra- and extracellular Abeta peptide formation.

METHODS

We investigated the effect of anti-beta-site antibodies in an AD animal model regarding antibody efficacy, as well as possible adverse effects in the brain and periphery that may result from antibody treatment.

RESULTS/CONCLUSIONS

Here, we show that long-term systemic administration of anti-APP beta-site antibodies to Tg2576 transgenic mice improved mouse cognitive functions associated with a reduction in both brain inflammation and the incidence of microhemorrhage. Furthermore, antibody treatment did not induce any peripheral autoimmunity responses. In spite of the beneficial effects observed in antibody-treated mice, brain Abeta levels were not altered as a result of antibody treatment.

Pathogenesis of haemophilic arthropathy

The pathogenetic mechanism of haemophilic arthropathy is multifactorial and includes degenerative cartilage-mediated and inflammatory synovium-mediated components. Intra-articular blood first has a direct effect on cartilage, as a result of the iron-catalysed formation of destructive oxygen metabolites (resulting in chondrocyte apoptosis), and subsequently affects the synovium, in addition to haemosiderin-induced synovial triggering. Both processes occur in parallel, and while they influence each other they probably do not depend on each other. This concept resembles degenerative joint damage as found in osteoarthritis as well as inflammatory processes in rheumatoid arthritis. These processes finally result in a fibrotic and destroyed joint.

Assessment of blood-induced cartilage damage in rabbit knees using scanning electron microscopy

PURPOSE

To investigate the harmful effects of a single episode of intra-articular bleeding on articular cartilage of rabbit knees using scanning electron microscopy.

METHODS

Autologous blood was injected into the right knee joints of 18 New Zealand white rabbits. Surface and cellular damages were examined by the scanning electron microscope (n=9) and light microscope (n=34), respectively. The injected right knees were then compared with the corresponding control left knees at one, 3, and 6 weeks after the blood injection.

RESULTS

The articular surface of the injected knees turned uniformly rough with multiple pits after one week. Maximal changes with elevations and depressions were observed at 3 weeks. These changes reversed at 6 weeks with the irregularities smoothing out. A similar pattern of transient cartilage damage was noted histologically.

CONCLUSION

Both scanning electron microscopic and light microscopic findings suggest that a single episode of intra-articular bleeding leads to articular cartilage damage but this appears to be reversible. Our findings of transient damage to the articular cartilage suggest that there is no need for intra-articular evacuation and washout following an acute episode of haemarthrosis.

Initiation of degenerative joint damage by experimental bleeding combined with loading of the joint: a possible mechanism of hemophilic arthropathy

OBJECTIVE

To investigate the effect of a limited number of experimental joint bleedings, combined with loading of the affected joint, on the development of progressive degenerative joint damage.

METHODS

The right knee of 8 mature beagle dogs was injected with freshly collected autologous blood 3 times per week for 4 weeks, to mimic a limited number of joint hemorrhages occurring over a short period. To ensure loading of the experimental joint, the contralateral control knee of the animals was fixed to the trunk 4 hours per day, 3 days per week. Ten weeks after the last injection, cartilage tissue and synovium were collected from both knees to analyze features of joint degeneration. Cartilage was prepared for analysis of proteoglycan turnover (synthesis, retention, release, and content) and histologic features. Synovium was prepared for histologic analysis.

RESULTS

The rate of proteoglycan synthesis was significantly increased, characteristic of degenerative cartilage damage as seen in osteoarthritis. Release of newly formed proteoglycans (as a measure of retention) and total loss of proteoglycans from the cartilage matrix were increased. Cartilage matrix integrity was adversely altered, as shown by histologic damage. Histologic analysis also revealed signs of synovial inflammation. These effects were not observed 10 weeks after the experimental bleedings in joints that did not undergo forced loading.

CONCLUSION

Experimental joint bleedings when combined with loading of the affected joint resulted in features of progressive degenerative joint damage, whereas similar joint hemorrhages without joint loading did not. This might reflect a possible mechanism of joint damage in hemophilia.

Pathobiology of hemophilic synovitis I: overexpression of mdm2 oncogene

Hemophilia is a genetic disease caused by a deficiency of blood coagulation factor VIII or IX. Bleeding into joints is the most frequent manifestation of hemophilia. Hemarthrosis results in an inflammatory and proliferative disorder termed hemophilic synovitis (HS). In time, a debilitating, crippling arthritis, hemophilic arthropathy, develops. Although the clinical sequence of events from joint bleeding to synovitis to arthropathy is well documented, the component or components in blood and the molecular changes responsible for hemophilic synovitis are not known. Iron has long been suspected to be the culprit but direct evidence has been lacking. Previously, we showed that iron increased human synovial cell proliferation and induced c-myc expression. Here we show that bleeding into a joint in vivo and iron in vitro result in increased expression of the p53-binding protein, mdm2. Iron induced the expression of mdm2 by normal human synovial cells approximately 8-fold. In a murine model of human hemophilia A, hemarthrosis resulted in pathologic changes observed in human hemophilic synovitis and a marked increase in synovial cell proliferation. Iron, in vitro, induced the expression of mdm2. The molecular changes induced by iron in the blood may be the basis of the increase in cell proliferation and the development of hemophilic synovitis.

Modified magnetic resonance imaging score compared with orthopaedic and radiological scores for the evaluation of haemophilic arthropathy

Twenty-four joints (10 knees and 14 ankles), with at least one manifestation of bleeding (proven by sonographic assessment), of 15 patients with haemophilia were investigated prospectively. For magnetic resonance imaging (MRI) evaluation, the MRI scale of Nuss et al. was modified to a MRI score (max. 13 points/joint) to allow a comparison with the physical examination score (max. 12 points) and the radiological score (Pettersson score; max. 13 points). The number of joint bleeds correlated well with the degree of arthropathy P < 0.01). In all 16 joints with a maximum of two bleeds, no alterations were found by physical examination, or radiological and MRI assessment. Joints with three bleeds had physical examination scores between 0 and 2, Pettersson scores from 0 to 3 and MRI scores of 2. Joints with four or more bleeds had physical examination scores ranging between 3 and 7, radiological scores between 7 and 12 and MRI scores between 3 and 8. The MRI score describes initial joint alterations more precisely and earlier than other assessments, allowing a discerning estimation of the degree of arthropathy, as well as a follow-up of haemophilic arthropathy and an improvement after change of treatment. In addition, the modified MRI score seems to differentiate better between early and advanced signs of arthropathy than the MRI scale of Nuss et al.

Blood-induced joint damage: a canine in vivo study

OBJECTIVE

To investigate the direct and indirect (via synovial inflammation) effects of intraarticular bleeding on cartilage in vivo.

METHODS

Right knees of 14 beagle dogs were injected with autologous blood on days 0 and 2. Cartilage matrix proteoglycan turnover, collagen damage, and synovial inflammation of these knees, including the cartilage-destructive properties of the synovial tissue, were determined and compared with those of the left control knees on day 4 (short-term effects; n = 7) and day 16 (long-term effects; n = 7).

RESULTS

Injected knees had a diminished content of proteoglycans in the cartilage matrix, and release of proteoglycans was enhanced (days 4 and 16). The synthesis of proteoglycans was significantly inhibited on day 4 but was enhanced on day 16. On day 4 more collagen was denatured in the injected joint than in the control joint; this effect was no longer detectable on day 16. Synovial tissue showed signs of inflammation on day 4 and day 16 but had cartilage-destructive properties only on day 16.

CONCLUSION

In vivo exposure of articular cartilage to blood for a relatively short time results in lasting changes in chondrocyte activity and in cartilage matrix integrity, changes that may predict lasting joint damage over time. Interestingly, the direct effect of blood on cartilage precedes the indirect effect via synovial inflammation.

When should prophylactic treatment in patients with haemophilia A and B start?--The German experience

Radiological and orthopaedic outcome in severe and moderate haemophilia A and B patients undergoing long-term prophylactic treatment were prospectively investigated focusing on the age of onset of prophylaxis and the number of joint bleedings prior to treatment. We report on 21 patients with severe and moderate haemophilia A and B receiving prophylactic treatment of between 3.1 and 16.1 years' duration. Three patient groups were evaluated according to the age at onset of prophylaxis. In group I prophylactic treatment was initiated in the first 2 years of life. Patients in group II received prophylaxis at the age of 3-6 years. Late-onset or secondary prophylactic treatment was started at the age of 6 years and above in seven patients (group III). All patients received virus-inactivated F VIII or F IX concentrates at dosages of 30-50 IU/kg body weight i.v. three times per week for those with haemophilia A and twice per week for those with haemophilia B. Elbow, knee and ankle joints were investigated at 3-4-yearly intervals according to the radiological and orthopaedic scores recommended by the World Federation of Haemophilia. The total number of joint bleedings before and after start of prophylaxis were recorded in all patients. In group I 7/8 patients had unaffected joints with constant radiological and orthopaedic scores of zero or 1, after a median of 11.25 years of prophylactic treatment. One patient in this group demonstrated mild radiological alterations (score 4). Patients in group II showed neither radiological nor orthopaedic alterations at study entry. Surprisingly, worsening joint scores could be detected despite ongoing prophylaxis after the 3-year interval (median orthopaedic score 4, median radiological score 8). Treatment group III already showed considerable joint damage at study entry with a median radiological score of 11 (0-33) and a median orthopaedic score of 4 (0-11). Despite prophylactic treatment, both radiological (median 19.5, range 2-47) and orthopaedic scores (median 8, range 2-12) deteriorated after 3 years. Prior to onset of prophylaxis, no or only one joint bleeding occurred in treatment group I. In group II, a median of six joint bleeds (range 1-8) was reported before prophylaxis was started. Patients in group III usually experienced a median of more than 10 joint haemorrhages (range 6-10 or more). Under prophylactic treatment the number of joint bleedings decreased significantly in groups II and III. However, radiological and orthopaedic scores increased as a sign of progressing osteoarthropathic alterations in patients reporting more than five joint haemorrhages onset of prophylaxis whereas no joint alterations could be assessed in patients with no or only one joint bleeding episode prior to prophylaxis. Even a small number of joint bleedings seems to cause irreversible osteoarthropathic alterations leading to haemophilic arthropathy. Once apparent, further progression of joint damage could not be arrested despite of prophylactic treatment (groups II and III). In order to prevent haemophilic arthropathy, effective prophylaxis should be started before or at least after the first joint bleeding in severe haemophilia A and B.

Proteoglycan degradation in hemarthrosis. Intraarticular, autologous blood injection in rat knees

We determined the degradation of articular cartilage proteoglycans in a single episode of experimental hemarthrosis in rat knees. The right knee joints of rats were injected once with autologous whole blood. Both knee joints were examined histologically. Biochemical studies of cartilage proteoglycans extracted from the knees were also conducted. Histological examination revealed an accumulation of mononuclear cells in intraarticular fibrin clots and subsynovial layers 8 hours after the injection of blood. Accordingly, initiation of proteoglycan degradation occurred 8 hours after injection of blood, lasting from 1 day of limited degradation to 3 days; recovery then occurred within 7 days. The proteoglycan degradation could be inhibited by 1 mM phenylmethylsulfonyl fluoride, a general serine proteinase inhibitor, 0.1 M 6-aminohexanoic acid, a specific inhibitor of plasminogen activators, 10 mM EDTA, and 10(-6) to 10(-8) M dexamethasone, indicating that the accumulation of mononuclear cells in intraarticular fibrin clots and subsynovial layers may play an important role in cartilage damage.

Synovial hemangioma: a report of 20 cases with differential diagnostic considerations

True synovial-based hemangiomas are uncommon lesions and, as such, may enter the differential diagnosis of other lesions encountered more frequently in clinical practice, including pigmented villonodular synovitis and traumatic hemarthrosis. The consultation files of the Armed Forces Institute of Pathology were searched for benign vascular lesions diagnosed as synovial or bursal hemangiomas vascular lesions diagnosed as synovial or bursal hemangiomas submitted between the years 1960 and 1985; 20 cases of synovial hemangioma were identified. The patients ranged in age from 9 to 49 years at the time of presentation (average age, 25 years). Sixty-five percent of the patients were male; 35% were female. Presenting symptoms included pain and swelling (31%), pain alone (31%), and a painless mass (31%). Affected regions included the knee (60%), the elbow (30%), and the finger (10%). In 65% of cases the lesion was confined to the intra-articular synovium; in 30% of cases the hemangioma was located in a bursa adjacent to a joint. One case was located largely within the joint cavity but had an area of extension into the suprapatellar recess. The dominant histologic patterns included cavernous hemangioma (50%), lobular capillary hemangioma (25%), arteriovenous hemangioma (20%), and venous hemangioma (5%). One lesion (which had been incompletely excised) was removed in its entirety 3 months after the initial subtotal resection; otherwise, none of the patients studied developed recurrent disease. The clinical diagnosis of hemangioma was made in 22% of cases, while an initial pathologic diagnosis of hemangioma was reached in 67% of cases. Pathologic differential diagnostic considerations include nonspecific synovitis/bursitis, pigmented villonodular synovitis, nodular synovitis, and organizing hemorrhage. A relationship between synovial hemangioma and pigmented villonodular synovitis was not suggested by this analysis of our material.

Rheumatic manifestations of haemochromatosis

Haemochromatosis (HC) is a group of phenotypically heterogeneous clinical syndromes, which may have a common molecular basis. Classical genetic haemochromatosis (GHC) is one of these syndromes and is a disorder of iron storage due to an increase in intestinal iron absorption, which results in progressive and massive iron deposition leading to fibrosis and organ malfunction. The liver, pancreas, heart and pituitary are commonly involved. There is a specific arthropathy and an association with osteoporosis. Clinically, the arthropathy may resemble rheumatoid arthritis, with acute attacks of inflammation associated with bilateral destruction of the metacarpophalangeal joints. However, bony joint swelling may occur, suggestive of osteoarthritis. Hip arthritis may be unduly severe and disabling. Haemochromatosis arthritis is composed of three radiographic categories: isolated chondrocalcinosis, hypertrophic osteoarthritis which is indistinguishable from pyrophosphate associated arthropathy, and disease specific changes such as subchondral radiolucency of the femoral head, hook-like osteophytes on the metacarpal heads and a degenerative predilection for the metacarpophalangeal joint rather than the scapholunate. The characteristic histological changes are: abnormal amounts of iron deposits, little or no signs of synovial inflammation and CPPD deposition. Subchondral radiolucency of the femoral head and atypical stripping of the cartilage from the subchondral bone are thought to be specific radiographic and histological changes of HC. The pathogenesis of HC arthritis has been associated with the presence of iron in joint tissue, a defect in cartilage metabolism and immunological dysfunction. Treatment has little effect on clinical, radiological or histological progression.

Experimental haemarthrosis in rhesus monkeys: morphometric, biochemical and metabolic analyses

The effects of a single episode of massive haemarthrosis in rhesus monkeys were studied. Autologous whole blood was injected into a femorotibial joint of 16 anaesthetized monkeys, equally divided into four groups and killed 7 days, 2, 3 and 6 months post-injection (PI). Synovial membrane and femoral articular cartilage were analysed morphometrically and articular cartilage was further analysed biochemically and metabolically. At 7 days PI, morphometric evaluation revealed a significant increase (P less than 0.05) in synovial membrane cellularity and synovial intimal thickness of injected joints versus control joints. This change was no longer evident 2 months PI. There was also an overall (n = 16) significant increase (P less than 0.05) in femoral articular cartilage cellularity in injected joints. The average chondrocyte lacuna area of injected joints was not statistically different from the control joints. Biochemical analyses of femoral articular cartilage revealed a significant decrease in hexosamine concentration (P less than 0.05) of injected joints. There was no significant difference between the injected and control joints in hydroxyproline or total protein concentration. Metabolic analyses revealed a significant increase (P less than 0.05) in cartilage collagenous protein production by injected joints compared with control joints. There were no significant differences in cartilage or secreted total protein production between injected and control joints. There were also no significant differences in cartilage or secreted proteoglycan production between joints. Morphometric evaluation of articular tissues following massive haemarthrosis has quantified a temporary hyperplastic reaction. A significant decrease in cartilage hexosamine concentration in haemarthrotic joints suggests this is a crucial biochemical event in the pathogenesis of blood-induced cartilage destruction.

Ultrastructural changes in synovium and cartilage in experimental hemarthrosis in dogs

This paper reports electron-microscopic findings in synovium and cartilage in experimental hemarthrosis in dogs. The results are correlated with the total amount of glycosaminoglycans in the cartilage matrix, measured by the fixed-charge density method. Very early, changes are seen in the synoviocytes, similar to synovitis, and especially phagocytosis of iron-containing particles forming secondary lysosomes or siderosomes. Siderosomes are also a constant feature seen in the chondrocytes, together with changes in the rough endoplasmic reticulum and in the glycogen content, correlating with the changes in the ground substance.

Macroscopic, microscopic and ultrastructural findings in experimental haemarthrosis of rhesus monkeys

The effects of a single episode of massive haemarthrosis in rhesus monkeys were studied morphologically. Autologous whole blood was injected into a femorotibial joint of 16 anaesthetized monkeys, equally divided into four groups and killed 7 days, 2, 3 and 6 months post injection (PI). Synovial membrane and articular cartilage were examined for macroscopic, microscopic and ultrastructural changes. Haemarthrosis was only evident in one monkey by 7 days PI. Slight yellow-brown discoloration of synovium and cartilage was evident in groups killed early after injection. Histologically, a hyperplastic and inflammatory reaction was present in the synovium at 7 days PI. Ultrastructural examination of synoviocytes in this group revealed numerous cytoplasmic vacuoles and prominent microplicae compatible with increased phagocytic activity. Erythrophagocytosis by synoviocytes was observed by light microscopy and confirmed by transmission EM. Results of scanning EM suggested that red cells might also pass through the synovial intima. Transmission EM also revealed mild degenerative changes in superficial chondrocytes. Rhesus monkeys reacted morphologically to haemarthrosis in the same way as dogs and rabbits, with mild morphological changes that resolved by 2 months PI.

Early changes in the ground substance of articular cartilage in experimental hemarthrosis in dogs, measured by the fixed-charge density method

This work presents early findings in the articular cartilage of dog knees in experimental hemarthrosis produced by injections of whole blood, red blood cells, white blood cells, serum, and iron citrate. The effect of coagulation and synovectomy was also studied. The fixed-charge density determination has proved to be a reliable, easy, and rapid method for finding - very early in the process - quantitative changes in cartilage ground substance. Changes in the proteoglycan (PG) content of articular cartilage matrix take place after a certain duration and intensity of hemarthrosis, after which loss of ground substance is repeatedly and consistently observed. After some time (6 months, and culminating after 14 months in our study) a reparative reaction takes place. In experimental hemarthrosis of longer duration this healing reaction seems to be overwhelmed by the degrading forces, with probable further evolution to the full-blown pathology. The cellular components of the blood seem to play a major role. Prophylactic synovectomy seems to be effective only in preventing further bleeding. Coagulation of the intra-articular blood does not alter its deleterious effect. Finally, a small iron ligand alone, although proven in vitro to penetrate into cartilage, is not capable of producing matrix changes.

Mechanisms of joint damage in an experimental model of hemophilic arthritis

Autologous whole blood was injected into the knee joints of rabbits 3 times each week for 12 weeks. The resulting destructive arthritis showed macroscopic and microscopic changes similar to those described in hemophilic arthritis in humans. Immunofluorescence studies indicated that a specific immune response is probably not involved in the pathogenesis of hemophilic arthritis. Detailed histopathologic examinations of knee joints in both the early and the late phase of arthritis revealed an obvious synovial and cartilage iron load, in the absence of inflammatory changes. The implications of these findings in the pathogenesis of destructive cartilage changes are discussed.

Liposome-induced synovitis in rabbits. Light and electron microscopic studies

A solution containing synthetic liposomes was injected into rabbit knee joints. This induced light and electron microscopic findings very similar to those seen in acute or chronic arthritis, not attributable to any mechanism other than to spherulites, in humans. Synovial fluid studies revealed leukocytosis and abundant extracellular, and/or intracellular positively birefringent spherulites, which appeared as Maltese crosses. Histologic studies of synovial membranes showed infiltration with polymorphonuclear neutrophils or mononuclear cells. Examination of the synovial fluids and synovial membranes by electron microscopy revealed intracellular multilayered membranous arrays of varying shapes. These observations suggest that further consideration should be given to a phlogistic role for similar spherulites found in some patients.

The nature of iron deposits in haemophilic synovitis. An immunohistochemical, ultrastructural and X-ray microanalytical study

Using a computerized electron-probe X-ray microanalytical technique to measure phosphorus/iron ratios we have defined the iron saturation of ferritin in vitro from prepared ferritin standards of known iron loading. This technique has been applied to the study of 5 haemophilic synovial membranes. At light microscope level the distribution and relationship of iron/ferritin were defined using Perls' reaction and an immunoperoxidase technique respectively. The synovia from all cases contained intra and extra-cellular deposits of Perls' positive material which were granular in nature in the most superficial synovial cells. There were increasing numbers of pheomorphic (1-12 micron diameter ovate bodies in the deeper synovial layers. Immunoperoxidase ferritin staining produced a strongly positive reaction in the granular material but the ovate bodies were negative with the exception of some peripheral staining. X-ray microanalysis showed the granular material to be highly iron saturated ferritin and the ovate bodies to be almost pure iron. We suggest that iron saturated ferritin in the synovial membrane could increase/perpetuate inflammation by promoting lipid peroxidation.

[Hemarthrosis and cruciate ligaments - biomechanical studies. 1]

Experimental studies on animals were conducted in order to investigate the influence exerted by a posttraumatic hemarthrosis upon the cruciate ligaments. The cruciate ligaments used in this experimentation had partly been exposed only to a posttraumatic hemarthrosis, the other part showed an additional lesion of the synovial sheath. Further investigations were carried out in order to find out if the effect of the hemarthrosis is modified by a plaster immobilization of the concerned extremity. In a comparative study, cruciate ligaments which had been exposed to hemarthrosis for different periods of time and normal cruciate ligaments were submitted to mechanical tension which was exerted until rupture. By means of extensive pre-experiments it was possible to define the practical execution, the storage of the removed cruciate ligament preparations, and the general mechanical behavior of cruciate ligaments in rabbits. The study showed that all cruciate ligaments exposed to hemarthrosis presented at least a temporary significant reduction of their mechanical loading capacity. This reduction was even more significant in case of an additional lesion of the synovial sheath. In the first case, a restitution of the normal loading capacity was observed after 8 to 12 weeks, in the second case (additional lesion of the synovial sheath) after 12 to 16 weeks. These results were not improved by a plaster immobilization of the concerned extremity; on the contrary this caused rather a negative tendency.

[Consequences of hemarthrosis for the knee joint (author's transl)]

The presence of an hemarthrosis generally is a sign of a particularly severe joint lesion. Arthrous alterations appearing post-traumatically can therefore be due to the extent of the joint lesion as well as to the accompanying hemarthrosis. A group of 24 young adult rabbits was submitted to morphologic examinations in order to find out in which way an isolated hemarthrosis can be responsible of degenerative cartilage alterations. At intervals of eight days each, 3 cm3 of their own blood were injected into both knee joints of the rabbits. One knee joint was immobilized, the other was mobile. The results prove that the hemarthrosis represents a considerable risk with regard to the trophism of the concerned joint. A direct enzymatic damage to the joint cartilage alone or in combination with trophical alterations appearing later on can lead to a formation and aggravation of arthrosis. The degenerative alterations are increased in an immobilized joint. Bearing in mind these alterations, the conclusion is drawn for clinical practice that the hemarthrosis has to be considered when establishing both diagnosis and therapy plan (punction, joint lavage, drainage, immobilization as early as possible).

Final stages of erythrophagocytosis in the sheep placenta

In trophoblastic epithelial cells of the sheep placenta the final stages of erythrocyte breakdown within the lysosomal apparatus were studied at the ultrastructural level. As a result of hemoglobin digestion lysosomes containing hemoglobin-derived pigments (HDP) were formed. The HDP-lysosomes were acid phosphatase-positive, highly electron-dense bodies of round to irregular shape containing whorled membranous formations. The accumulation of these lysosomes in epithelial cells led to fusion resulting in the formation of conglomerates. At the end of the gestation period the amount of HDP-lysosomes and their conglomerates markedly increased. In addition to erythrocytes the trophoblastic epithelial cells in the erythrophagocytic regions phagocytosed maternal leukocytes and neighbouring epithelial cells and giant cells. By gradual accumulation of HDP-lysosomes and remnants of phagocytosed cells, highly electron-dense acid phosphatase-positive residual bodies of variable appearance were formed within the epithelial cells. At the end of pregnancy the spaces between juxtaposed villi of the trophoblastic epithelium in the erythrophagocytic zones were occluded by apposition of the epithelial cells. In these occluded regions an increase in highly electron-dense large-sized residual bodies (15-22 micrometer of dimension) occurred as a result of multiple cell phagocytosis in combination with fusion. In these residual bodies the numerous incorporated HDP-lysosomes and the remnants of phagocytosed cells could still be recognized.

Importance of platelets in increased vascular permeability evoked by experimental haemarthrosis in synovium of the rat

Increased vascular permeability of synovium induced by experimental haemarthrosis was studied in the stifle joint of the rat. Abnormal permeability was detected by injecting animals intravenously with colloidal carbon and examining the synovial vessels for intramural deposits of carbon. Both fresh and heparinized whole blood injected into the joint induced a marked permeability response of synovial venules which persisted for 18 hours. Platelets suspended in heparinized Tyrode solution induced a similar response, but one lasting only 12 hours. The permeability effects of suspensions of leucocytes and erythrocytes on the synovial vasculature were relatively mild and were maximal 5 and 12 h respectively after intra-articular injection. Heparinized platelet-free plasma had no significant permeability effects. These results indicate that platelets may play an important role in the pathogenesis of synovial inflammation in haemarthrosis.

Ultrastructure of intramuscular haematomas and electron-probe x-ray analysis of extracellular and intracellular iron deposits

Haematomas were produced in rabbits by intramuscular injections of autologous blood. Clotting and marked lysis of erythrocytes was noted in these haematomas but there was no evidence of fragmentation of erythrocytes, prior to, during, or after ingestion by macrophages as has been reported in other sites such as spleen, peritoneal cavity or joint cavity. The phagocytosis of intact erythrocytes, lysed erythrocytes and haemoglobin led to the formation of three main types of lysosomal bodies, (1) myelinosomes, (2) siderosomes and (3) myelinosidersomes. Electron-probe X-ray analysis of siderosomes has yielded further data supporting the idea that haemosiderin is essentially an inorganic iron compound; presumably a hydrated ferric oxide. An unusual and hitherto unreported finding was the occurrence of electron-dense granules in the connective tissue matrix in two animals. The granules were shown to contain iron, calcium, potassium and phosphorus. It is thought they might represent an attempt at pathological calcification in damaged tissue.

Satellite heterophagosomes

An incidental observation made during a recent ultrastructural study shows that after ingestion of an erythrocyte by a Kupffer cell surface budding occurred from the heterophagosome leading to the formation of smaller satellite or daughter heterophagosomes. It is suggested that an entire erythrocyte may be too large to digest in a single heterolysosome and that fragmentation into smaller units facilitates digestion by bringing about better contact between the enzymes and substrates.

Synovial haemangioma of the knee: light and electron microscopic findings

Venous haemangioma of the synovium of one knee also involved adjacent, skin and muscle of the leg in a 4-yr-old girl. Phleboliths were seen in the knee on X-ray. Histologically, the synovium contained large venous channels and was laden with haemosiderin. On electron microscopy, the synovial cells were morpholgically most like synthetic (B) cells. Erythrocytes were ingested and broken down, stepwise, to siderosomes. The synovial cell cytoplasm also contained electron-dense punctate iron deposits. The synovial response appeared to represent chronic haemarthrosis.

Ultrastructure of experimentally produced subcutaneous haematomas in the rabbit

Haematomas were produced in rabbits by subcutaneous injection of autologous blood. Clotting and marked lysis of erythrocytes was noted in these haematomas, but there was no evidence of fragmentation of erythrocytes prior to or after ingestion by macrophages as has been reported in other sites such as the peritoneal cavity and the joint cavity. The phagocytosis of intact erythrocytes, lysed erythrocytes and haemoglobin led to the formation of three main types of lysosomal bodies; (1) myelinosomes containing whorled osmiophilic membranes, (2) siderosomes containing haemosiderin, and (3) myelinosiderosomes containing a mixture of osmiophilic membranes and haemosiderin.

Ultrastructure of the haemophilic synovial membrane and electron-probe X-ray analysis of haemosiderin

An ultrastructural study of the haemophilic synovial membrane revealed the presence of solitary siderosomes, compound siderosomes and a peppering of the cell cytoplasm with electron-dense particles. These changes were found in synovial intimal cells, subsynovial macrophages and fibroblasts. Electron-probe X-ray analysis of siderosomes revealed the presence of iron and traces of phosphorus. On the basis of previous and present studies it is postulated that haemosiderin is essentially a condensate of hydrated ferric oxide and that a variable amount of phospholipid material lies in company with it in the siderosome.

Electron probe x-ray analysis of siderosomes in the rabbit haemarthrotic synovial membrane

Electron probe x-ray analysis of siderosomes produced in the rabbit synovial membrane by repeated injections of autologous blood revealed two kinds of siderosomes; (1) those containing a small amount of phosphorus and, (2) those in which no phosphorus was detectable. On the basis of these findings and past studies it is concluded that haemosiderin is an inorganic compound of iron, probably a hydrated ferric oxide and that a variable amount of organic material (proteins, lipids, phospholipids, etc.,) probably occurs in company with the haemosiderin in the siderosome, but these variable components which decrease in amount with the passage of time cannot be considered as an integral part of haemosiderin.

Articular cartilage in corn oil-induced lipoarthrosis

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Ultrastructural characteristics of the synovial membrane in idiopathic haemochromatosis

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Clearance of Fe59-labelled erythrocytes from normal and inflamed rabbit knee joints. II. Autoradiographic and histological studies

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