Takahiko Irisa

Bone marrow fat cell enlargement and a rise in intraosseous pressure in steroid-treated rabbits with osteonecrosis

The etiology of steroid-induced osteonecrosis (ON) is unclear. This study was designed to determine whether bone marrow fat cell size, intraosseous pressure, and blood flow rate differed between steroid-treated rabbits with ON and those without. Twenty-nine rabbits were intramuscularly injected once with 20 mg/kg of methylprednisolone acetate (MPSL), and five rabbits were injected once with physiologic saline (PS) as a control. Intraosseous pressure and blood flow rate in the proximal femur were determined before and at 2 weeks after the injection. After these measurements, both femora and humeri were histopathologically examined for the presence of ON, and size of bone marrow fat cells were morphologically examined. At 2 weeks after steroid injection, the intraosseous pressure was significantly higher in rabbits with ON than in those without (p = 0.0251), and the blood flow rate had decreased significantly more in rabbits with ON than in those without (p = 0.0051). The size of the bone marrow fat cells was significantly (p = 0.0004) larger in rabbits with ON (diameter, 63.5 +/- 5.8 microm) than in those without (diameter, 53.3 +/- 6.9 microm). Injection of PS (5 rabbits), 1 (10 rabbits), 5 (10 rabbits), and 20 (10 rabbits) mg/kg of body weight of MPSL showed that a larger dose of steroid increased both fat cell size and prevalence of ON. These results suggest that bone marrow fat cell enlargement and a rise in intraosseous pressure may be important when considering the pathophysiology of steroid-induced ON in rabbits.

Fibroblast growth factor-2 determines severity of joint disease in adjuvant-induced arthritis in rats.

Rheumatoid arthritis (RA), a systemic inflammatory disease of unknown etiology, mainly affects synovial joints. Although angiogenic growth factors, including fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF), may play a critical role in the development and progression of RA joint disease, little information is now available regarding their exact role in initiation and/or progression of RA. In this study, we show that both polypeptides were up-regulated in the rat joint synovial tissue of an adjuvant-induced model of arthritis (AIA), as well as human subjects with RA. FGF-2 overexpression via Sendai virus-mediated gene transfer significantly worsened clinical symptoms and signs of rat AIA, including hind paw swelling and radiological bone destruction, as well as histological findings based on inflammatory reaction, synovial angiogenesis, pannus formation, and osteocartilaginous destruction, associated with up-regulation of endogenous VEGF. FGF-2 gene transfer to non-AIA joints was without effect. These findings suggested that FGF-2 modulated disease progression, but did not affect initiation. Reverse experiments using anti-FGF-2-neutralizing rabbit IgG attenuated clinical symptoms and histopathological abnormalities of AIA joints. To our knowledge, this is the first report indicating direct in vivo evidence of disease-modulatory effects of FGF-2 in AIA, as probably associated with endogenous VEGF function. FGF-2 may prove to be a possible therapeutic target to treat subjects with RA.

Prediction of the outcome of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head.

We have studied the correlation between the prevention of progressive collapse and the ratio of the intact articular surface of the femoral head, after transtrochanteric rotational osteotomy for osteonecrosis. We used probit analysis on 125 hips in order to assess the ratio necessary to prevent progressive radiological collapse over a ten-year period. The results show that a minimum postoperative intact ratio of 34% was required. This critical ratio may be useful for surgical planning and in assessing the natural history of the condition.

Prediction of the outcome of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head

We have studied the correlation between the prevention of progressive collapse and the ratio of the intact articular surface of the femoral head, after transtrochanteric rotational osteotomy for osteonecrosis. We used probit analysis on 125 hips in order to assess the ratio necessary to prevent progressive radiological collapse over a ten-year period. The results show that a minimum postoperative intact ratio of 34% was required. This critical ratio may be useful for surgical planning and in assessing the natural history of the condition.

Osteonecrosis induced by a single administration of low-dose lipopolysaccharide in rabbits.

We succeeded in developing a novel rabbit model of nonsteroid and nontraumatic osteonecrosis (ON) by use of a single- and low-dose lipopolysaccharide (LPS) injection. This model is simple and highly reproducible for the frequent development of multifocal and widespread ON lesions. Male adult Japanese white rabbits intravenously injected with a single injection of 10 microg/kg body weight of LPS were histopathologically examined in the early phase (3 [n = 3], 5 [n = 3], and 24 h [n = 3]) and at 4 weeks (n = 22). Seventy-seven percent of the rabbits developed multifocal ON 4 weeks after LPS injection. ON was also observed in the femoral and humeral condyle. The average percentage of necrotic area/total area examined was 86.7 +/- 29.1% and 78.8 +/- 16.7% in the proximal one third of both the femoral and humeral bones, respectively. Organized thrombi in the intraosseous small-sized arteries and arterioles were frequently seen in and around the necrotic tissues. In the early phase, LPS treatment prominently induced thrombocytopenia, hyperlipidemia, and increased plasma levels of plasminogen activator inhibitor-1 (PAI-1). The plasma level of PAI-1 was significantly higher in the rabbits with ON than in those without ON (p < 0.01). The immunohistochemical expression of tissue factor was exaggerated in monocytes/macrophages and adipocytes in both the femoral and humeral bones of the LPS-treated rabbits. Histologically, marrow necrosis and fibrin thrombi could be observed at 24 h. In addition, pretreatment with an anticoagulant, warfarin potassium, significantly decreased the incidence of LPS-induced ON (33%, n = 9, p < 0.05) associated with elongation of prothrombin time. The results of our study show that a single administration of low-dose lipopolysaccharide induces multifocal and widespread ON characterized by the pathophysiological participation of hypercoagulability in ON development. Therefore, this model would be useful for elucidating the pathogenesis of nonsteroid ON in humans especially inflammatory hypercoagulability-induced as well as for developing preventive and therapeutic strategies.

Increased level of apolipoprotein B/apolipoprotein A1 ratio as a potential risk for osteonecrosis

OBJECTIVE This study was performed to investigate whether a high ratio of apolipoprotein B to apolipoprotein A1 (apo B/apo A1 ratio) is significantly associated with the risk of developing non-traumatic osteonecrosis of the femoral head (ON). METHODS Fifty consecutive non-traumatic ON cases were compared with 50 age and sex matched controls, using both univariate and stepwise discriminant analyses, regarding the factors of corticosteroid, alcohol, cigarettes, cholesterol, triglyceride, and apo B/apo A1 ratio. To eliminate the possibility that ON or osteoarthritic change itself can increase the apo B/apo A1 ratio, a further 32 consecutive cases comprising nine traumatic ON and 23 osteoarthritis (OA) patients were analysed using Scheffe’s test. RESULTS There was a significant association between a high apo B/apo A1 ratio and the development of non-traumatic ON with both univariate (p=0.0001) and stepwise discriminant analyses (partialr 2=0.1239, p=0.0004). The apo B/apo A1 ratio in the non-traumatic ON group was significantly higher than that in the traumatic ON (p<0.01), control (p<0.001), or the OA groups (p<0.001). CONCLUSION A high apo B/apo A1 ratio is significantly associated with the risk of developing ON. This ratio may be useful for assessing the potential risk of developing osteonecrosis.

Dose effects of corticosteroids on the development of osteonecrosis in rabbits.

Objective The relationship between dose of corticosteroids and the prevalence of osteonecrosis (ON) has not been established. We examined the dose effects of corticosteroids on the development of ON in a rabbit model. Methods Rabbits were injected once intramuscularly with 1 (12 rabbits), 5 (12 rabbits), 20 (20 rabbits), and 40 (25 rabbits) mg/kg of methylprednisolone acetate (MPSL) into the right gluteus medius muscle. Four weeks after the MPSL injection, the proximal and distal parts of both the femora and humeri were histopathologically examined for the presence of ON. Hematological examinations were performed before and after the corticosteroid injection. Results In rabbits with 1, 5, 20, and 40 mg/kg MPSL, the incidence of ON was 0, 42%, 70%, and 96%, respectively. The dose of MPSL showed a significant association with the incidence of ON. Histologically, reparative tissues around the ON sites were observed in the rabbits with 5 mg/kg MPSL, but not observed in rabbits with 20 and 40 mg/kg MPSL. On hematological examination, hyperlipidemia and thrombocytopenia were most apparent in the rabbits receiving 40 mg/kg MPSL. Conclusion The study suggested that the dose of corticosteroids plays an important role in the development of ON in rabbits. The repair process was also found to be influenced by the dose of corticosteroids. Corticosteroid-induced hyperlipidemia and thrombocytopenia seemed to be associated with the incidence of ON.

Effects of cyclosporin A on the development of osteonecrosis in rabbits.

Background Osteonecrosis (ON) of the femoral head is a serious complication in patients who have undergone organ transplantation. Introduction of cyclosporin A has resulted in lower-dosage steroid treatment and a decrease in the occurrence of ON. We examined the effect of cyclosporin A on the development of ON in rabbits. Methods In experiment A, rabbits were given cyclosporin A and 20 mg/kg methylprednisolone acetate. The control group was given 20 mg/kg methylprednisolone acetate only. Experiment B was then performed to mimic the clinical situation in which the use of cyclosporin A and lower steroid doses resulted in a decrease in occurrence of ON. In Experiment C, the effects of treatment with cyclosporin A only on development of ON were examined. 4 weeks after injection, bilateral femora and humeri were examined histopathologically for ON. Results Cyclosporin A increased the incidence of ON in rabbits when given in combination with steroid (p = 0.04). No ON lesions were observed in rabbits treated with cyclosporin A alone. Interpretation Our findings suggest that the clinically reported reduction in occurrence of ON following the use of cyclosporin A is probably attributable to the lower steroid doses used.

Effects of Tacrolimus (FK506) on the Development of Osteonecrosis in a Rabbit Model

The present study examined the effects of tacrolimus (FK506) on the development of osteonecrosis in rabbits. In Experiment A, rabbits were given FK506, and also given a single dose of steroid. Control rabbits were given the same dose of steroid only. In Experiment B, rabbits were given FK506 and a reduced dose of steroid. The results showed that addition of FK506 did not change the number of rabbits with osteonecrosis when an identical steroid dose was given. When the steroid dose was reduced, the osteonecrosis incidence significantly decreased (p < 0.01). These results suggest that the clinically reported decrease in the osteonecrosis incidence following the introduction of FK506 is most likely attributable to the lower doses of steroids.

Brodie's abscess of the proximal femoral epiphysis in an adult woman with systemic lupus erythematosus

Abstract. We report an unusual case of pathologically proved femoral head Brodies abscess mimicking avascular necrosis of bone in a 51-year-old woman with a 2-year history of corticosteroid treatment for systemic lupus erythematosus. On plain radiographs, a rounded lucency and thin sclerotic margins together with subchondral collapse and a lytic region were observed in the femoral head. The histopathologic examination revealed a central abscess formation surrounded by fibrous tissue with the aggregation of neutrophils and plasma cells. To our knowledge, this is the first case report describing a Brodies abscess which had developed within the proximal femoral epiphysis in an adult.