Maruyama I

Overgrowth of human synovial cells driven by the human T cell leukemia virus type I tax gene

One of the salient pathological features of rheumatoid arthritis is synovial cell proliferation with bone erosion. Despite extensive investigation, the factors essential for synovial cell proliferation remain to be identified. Recent studies suggest that human T cell leukemia virus type I (HTLV-I) may play an important role in synovial overgrowth observed in patients with one type of chronic inflammatory synovitis. In order to confirm and extend these observations, we have established synovial cell clones (SCCs) from three HTLV-I carriers who demonstrated synovial overgrowth but were otherwise asymptomatic. HTLV-I proviral DNA randomly integrated into the cellular genome was present in 20-30% of SCCs. The SCCs carrying HTLV-I proviral DNA and expressing the tax gene exhibited high levels of proliferative potential. HTLV-I was found to function as a transcriptional trans-activator in these SCCs. Moreover, transfection of the tax expression plasmid into SCCs resulted in the same phenotype of increased proliferation and cytokine expression as exhibited by HTLV-I provirus-carrying and tax-expressing SCCs. These data suggest that tax plays a critical role not only in leukemogenesis but also in synovial overgrowth in humans.

Antithrombotic effect of recombinant human soluble thrombomodulin on endotoxin-induced disseminated intravascular coagulation in rats.

Thrombomodulin (TM) is an endothelial cell membrane glycoprotein which neutralizes thrombin procoagulant activity and accelerates the thrombin-catalyzed activation of protein C. We expressed recombinant human soluble TM (rhs-TM) in Chinese hamster ovary cells and compared the effects of rhs-TM and heparin on endotoxin-induced experimental disseminated intravascular coagulation (DIC) in rats. Experimental DIC was induced by a continuous intravenous infusion of endotoxin for four hours. rhs-TM or heparin was infused simultaneously with endotoxin. Treatment with rhs-TM significantly reversed the endotoxin-induced changes in significantly reversed the endotoxin-induced changes in following parameters: platelet count, fibrinogen level and fibrinogen and fibrin degradation products. Furthermore, glomerular fibrin deposits elevated by endotoxin treatment were reduced by the rhs-TM administration. Heparin showed the similar effects to rhs-TM. Activated partial thromboplastin time (APTT) in rats receiving rhs-TM were slightly longer than APTT in endotoxin-treated rats, but rats receiving heparin had much more prolonged APTT. From these results, we concluded that rhs-TM may be useful for the clinical treatment of DIC while having only minor adverse effects on APTT.

Glomerular localization of thrombomodulin in human glomerulonephritis

BACKGROUND Thrombomodulin (TM), a glycoprotein expressed on the surface of endothelial cells, transforms protein C into a potent anticoagulant by binding thrombin. TM may be an important regulator of intraglomerular coagulation because functional TM activity was demonstrated in glomeruli isolated from normal human and rat kidneys. The role of TM in glomerulonephritis is unknown. EXPERIMENTAL DESIGN Sections from 4 normal human kidneys and from kidneys of 100 patients with various forms of glomerulonephritis were studied by light and transmission electron microscopy, and by light and electron immunohistochemical techniques using polyclonal antibodies to recombinant human TM, and monoclonal antibodies to the membrane attack complex of the complement system. The expression of TM was graded from 0 to 4 according to the intensity and extent of the distribution, and the results were compared with the clinicopathologic findings. RESULTS In normal glomeruli and in glomeruli with minimal abnormalities, a small amount of TM was localized at the vascular pole only (grade 0-1). In membranoproliferative glomerulonephritis and lupus glomerulonephritis, the amount of TM found on the plasma membrane of endothelial cells was significantly increased (grades 2 to 4). The expression of TM was directly correlated with proteinuria (p < 0.001), glomerular hypercellularity (p < 0.01), and number of subendothelial immune deposits (p < 0.01). In contrast, in other forms of glomerular diseases, TM was not increased and no correlation was found with the clinicopathologic parameters. CONCLUSIONS In membranoproliferative glomerulonephritis and lupus glomerulonephritis, the amount of TM expressed by the plasma membranes of glomerular endothelial cells is increased, and this finding is a marker of disease activity. The significance of an increased expression of an endothelial anticoagulant glycoprotein in diseases characterized by pathologic intraglomerular coagulation is unknown, and requires further studies.

Expression of thrombomodulin in patients with spontaneous occlusion of the circle of Willis.

Background and Purpose We examined the expression of thrombomodulin, a recently isolated anticoagulant protein, in endothelial cells from patients with spontaneous occlusion of the circle of Willis (cerebrovascular moyamoya disease) to determine whether lack of the expression of thrombomodulin might lead to the thrombogenicity in patients with this disease. Methods The intracranial internal carotid arteries, the external carotid arteries, and the vertebral or basilar arteries from 12 autopsied patients who had this disease and eight control autopsied patients were examined immunohistochemically by using the antiserum against human thrombomodulin. Results All of the endothelial cells from the patients with this disease and from the control patients were positive for thrombomodulin. Immunoelectron microscopy also disclosed normal localization of thrombomodulin on the luminal plasma membrane. Immunohistochemically, we could find no significant differences in the expression of thrombomodulin among the arteries examined in this study. Conclusions We conclude that as far as we investigated immunohistochemically, the thrombogenicity in this disease is almost unlikely to depend on the abnormal expression of thrombomodulin.