Modeling and simulation of bone mineral density in Japanese osteoporosis patients treated with zoledronic acid using tartrate-resistant acid phosphatase 5b, a bone resorption marker.

Annual intravenous administration of zoledronic acid is used in the treatment of osteoporosis. A mathematical model was developed to predict bone mineral density up to 2 years after two annual doses of zoledronic acid from the early values of a bone resorption marker in osteoporosis patients. INTRODUCTION: The measurement of bone mineral density (BMD) has been used as a surrogate marker instead of the observation of incident fractures to detect the efficacy of treatment. However, this method requires a long time to obtain significant changes. On the other hand, bone resorption markers respond to bone resorption inhibitors within a few weeks. Therefore, the aim of this study was to develop a mathematical model predicting long-term BMD after two annual doses of zoledronic acid (ZOL) using the early response of a bone resorption marker in osteoporosis patients. METHODS: The model was constructed using 3410 tartrate-resistant acid phosphatase 5b (TRACP-5b) serum concentrations and 1146 lumbar spine (L2-L4) BMD values from 306 patients with primary osteoporosis. A mathematical model was developed to describe the time-dependent profiles of TRACP-5b and BMD. RESULTS: The percentage changes from baseline of the BMD (%BMD) at up to 2 years were predicted from patients' baseline BMD and baseline and 12-week TRACP-5b values by the model obtained. The simulated 90% prediction interval almost covered the observed %BMD distribution at each time point, and the predictions were comparable to the observed %BMD. CONCLUSIONS: This is the first model to predict BMD for up to 2 years following two annual doses of ZOL using patients' background characteristics and the early response of TRACP-5b. This model allows us to inform patients at the initial stage of ZOL treatment of their predicted response to treatment.

Pharmacokinetics of recombinant human soluble thrombomodulin, thrombomodulin alfa in the rat.

1. The study aimed to investigate the pharmacokinetics of thrombomodulin alpha (TM-alpha), human-soluble thrombomodulin in rats. 2. Intravenously administered TM-alpha was eliminated in two phases (T(1/2 alpha) = 0.2-0.3 h and T(1/2 beta) = 6-8 h), and the elimination curve was linear in a dose range of 10-250 microg kg(-1). Based on the results of tissue concentration studies after reaching the steady-state, the highest concentration of TM-alpha was seen in the plasma, suggesting the low levels of transfer to tissues (< or = 22% of plasma levels). 3. In vivo metabolism of TM-alpha was also analysed using high-performance liquid chromatography. The main peak observed in the plasma was TM-alpha, and even 72 h after the last dose of repeated administrations, 80% or more was unchanged form. Approximately half of the radioactivity excreted in the urine was recovered as a peak corresponding to TM-alpha. 4. The results reveal that although plasma clearance was lower in the renally impaired rats, the decrease was not large, with a difference of only about 20%. As a result, although the cause remains unclear, it is considered unlikely that the plasma concentrations of TM-alpha will vary considerably in patients with renal impairment.

Phase I study of a novel recombinant human soluble thrombomodulin, ART-123.

BACKGROUND: Anticoagulants are often given for extended periods of time to patients at high risk for venous thromboembolism, such as after orthopedic surgery. Daily subcutaneous (sc) injections can be inconvenient to the patient. A long-acting anticoagulant requiring less frequent dosing could make treatment more acceptable. Thrombomodulin is a natural anticoagulant that activates protein C, which leads to inactivation of factor (F)Va and FVIIIa and decreased thrombin formation. Recombinant human thrombomodulin is a novel anticoagulant with a long half-life in animal models. METHODS AND RESULTS: This phase I study examined pharmacokinetics, pharmacodynamics, and safety of recombinant human soluble thrombomodulin (ART-123) after administration of doses between 0.02 and 0.06 mg kg(-1) body weight intravenously (iv), and between 0.02 and 0.45 mg kg(-1) sc in 55 healthy volunteers. The plasma half-life was 2-3 days after sc injection of various single doses. Plasma ART-123 levels estimated to be needed for prevention of thrombus formation in humans were maintained for at least 6 days after single sc injection of 0.30 and 0.45 mg kg(-1) ART-123. Antithrombotic activity with these doses was demonstrated by achieving prothrombinase inhibition of more than 80% for more than 6 days after administration. No major bleeding occurred. Pharmacodynamic modeling revealed that adequate antithrombotic ART-123 levels can be achieved for 6 days with one dose of 0.45 mg kg(-1) ART-123, and for 12 days with 2 doses of 0.30 mg kg(-1), given 5 days apart. CONCLUSIONS: Recombinant human soluble thrombomodulin (ART-123) has a long half-life after sc injection and is well tolerated, making it a suitable agent to be tested in clinical thromboprophylaxis trials.

Role of MOG-stimulated Th1 type "light up" (GFP+) CD4+ T cells for the development of experimental autoimmune encephalomyelitis (EAE).

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis in humans. EAE can be passively transferred into naive syngeneic animals by administration of MOG-specific T cell clones. Lymphocytes isolated from green fluorescent protein (GFP)-transgenic (Tg) mice can light up by emitting green fluorescence, thus making it feasible to use such animals in a passive transfer model for EAE. When MOG-sensitized splenic lymphocytes from GFP-Tg mice were adoptively transferred to irradiated, syngeneic C57BL/6 and RAG-1(-/-)mice, typical symptoms of EAE developed. Analysis of the reconstituted mice with EAE revealed prominent infiltration of fluorescing (GFP+), CD4+ T cells into the central nervous system (CNS). Real-time confocal imaging revealed these cells in the spinal cords and brains of recipient mice. This infiltration was also confirmed by anti-GFP monoclonal antibodies. Furthermore, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) evaluation indicated that the infiltrating GFP+, CD4+ T cells exclusively produced T helper type 1 (Th1) cytokines, especially interferon-gamma (IFN-gamma). These results clearly show that MOG-specific CD4+ T cells preferentially invade into the CNS and mediate the development of EAE by producing Th1-biased cytokines.

Reciprocal regulation of prothrombin secretion and tyrosine aminotransferase induction in hepatocytes.

Multicellular spheroids of hepatocytes are known to maintain liver functions for a long period. Rat hepatocytes were isolated to form spheroids by rotation culture and immobilized within calcium alginate. Immobilized spheroids had a much higher extent of tyrosine aminotransferase induction, which is one of the liver-specific differentiated functions, than immobilized non-aggregated cells, while the spheroids secreted significantly less prothrombin than non-aggregated cells. Co-culture of hepatocytes and non-parenchymal liver cells in a monolayer enhanced tyrosine aminotransferase induction and suppressed prothrombin secretion, while conditioned medium prepared from non-parenchymal cells greatly stimulated tyrosine aminotransferase induction and suppressed the prothrombin secretion and DNA synthesis in monolayer-cultured hepatocytes. Prothrombin secretion in hepatocytes was subjected to cell-density-dependent regulation. In a similar manner to other growth-related functions, prothrombin secretion was stimulated at low cell density. It has been reported that thrombin activates the zymogen of hepatocyte growth factor activator [Shimomura, T., Kondo, J., Ochiai, M., Naka, D., Miyazawa, K., Morimoto, Y. & Kitamura, N. (1993) J. Biol. Chem. 268, 22,927-22,932]. Therefore, prothrombin secretion could be one of the growth-related functions and involved in wound healing and liver regeneration.

Rapid formation of multicellular spheroids of adult rat hepatocytes by rotation culture and their immobilization within calcium alginate.

Tyrosine aminotransferase (TAT) induction and albumin secretion abilities were examined in rat hepatocytes immobilized within calcium alginate; the immobilized hepatocytes lost these abilities within a week. An attempt was then made to immobilize multicellular spheroids of hepatocytes for the purpose of stabilizing the liver functions. Although it takes at least 4 days to form spheroids in the conventional method using monolayer-cultured cells, in this study we developed a new method for rapid spheroid formation. Isolated hepatocytes were seeded into a polystyrene dish and incubated on a rotary shaker. Hepatocytes started to aggregate after 6 h of the rotation culture, and spheroids approximately 100 microns in diameter formed within 24 h. The immobilized spheroids had higher TAT induction and albumin secretion abilities, which were maintained for a longer time, than the immobilized nonaggregated cells. Further stabilization was observed in immobilized heterospheroids formed in the presence of nonparenchymal liver cells. This method for the rapid formation of spheroids consisting of hepatocytes and nonparenchymal liver cells could be utilized in the construction of a bioartificial liver support system.

Stimulative effect of non-parenchymal liver cells on ability of tyrosine aminotransferase induction in hepatocytes.

Hepatocytes and non-parenchymal liver cells were isolated from adult rat liver and co-cultured for 48 hours as a monolayer on polystyrene culture dishes. The ability of tyrosine aminotransferase (TAT) induction in hepatocytes was examined in the presence of dexamethasone and dibutyryl cAMP. Non-parenchymal cells greatly enhance the ability of TAT induction of hepatocytes. A soluble factor with molecular weight of more than 10,000 is responsible for this enhancement, because conditioned medium prepared from non-parenchymal cells is also stimulatory. Non-parenchymal cells restored the ability in hepatocytes damaged with the addition of D-galactosamine. Conditioned medium prepared from non-parenchymal cells treated with D-galactosamine had higher activity of enhancement than the medium from normal cells. The soluble factor might be released in response to some signal of injury. Hepatocytes and non-parenchymal cells were immobilized within Ca-alginate, and although immobilized hepatocytes rapidly lost the ability to induce TAT, hepatocytes co-immobilized with non-parenchymal cells maintained the ability during 4 days of culture. These results indicated that non-parenchymal liver cells, as well as hepatocytes, could be used to construct a bioartificial liver support system.