Increased serum levels and sinusoidal expression of thrombomodulin in acute liver damage

Plasma thrombomodulin as a candidate biomarker for the diagnosis and prognosis of HBV-related acute-on-chronic liver failure

Background and Aim

Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) is a complicated syndrome with high short-term mortality. Effective biomarkers are required for its early diagnosis and prognosis. This study aimed to determine the diagnostic and prognostic value of thrombomodulin (TM) in patients with HBV-ACLF.

Methods

The expression of TM during disease progression was evaluated through transcriptomics analysis. The plasma TM concentrations of 393 subjects with HBV-ACLF (n=213), acute-on-chronic hepatic dysfunction (ACHD, n=50), liver cirrhosis (LC, n=50) or chronic hepatitis B (CHB, n=50), and normal controls (NC, n=30) from a prospective multicenter cohort, were measured to verify the diagnostic and prognostic significance of plasma TM for HBV-ACLF patients by enzyme-linked immunosorbent assay (ELISA).

Results

TM mRNA was highly expressed in the HBV-ACLF group compared with the ACHD group (AUROC=0.710). High expression of TM predicted poor prognosis for HBV-ACLF patients at 28/90 days (AUROCs=0.823/0.788). Functional analysis showed that TM was significantly associated with complement activation and the inflammatory signaling pathway. External validation confirmed its high diagnostic accuracy for HBV-ACLF patients (AUROC=0.796). Plasma TM concentrations were correlated with organ failure, including coagulation and kidney failure. Plasma TM concentrations showed a potential prognostic value for 28-day mortality rates (AUROC=0.702). Risk stratification specifically identified HBV-ACLF patients with a high risk of death as having a plasma TM concentration of ≥8.4 ng/mL.

Conclusion

This study reveals that the plasma TM can be a candidate biomarker for early diagnosis and prognosis of HBV-ACLF, and might play a vital role in coagulation and inflammation.

High plasma soluble thrombomodulin levels indicated poor prognosis of decompensated liver cirrhosis: a prospective cohort study

OBJECTIVE

Hepatic sinusoidal endothelial injury is a prominent characteristic of liver cirrhosis. We determined plasma soluble thrombomodulin (sTM) levels in cirrhosis patients to evaluate the relationship between vascular injury and long-term prognosis.

METHODS

A prospective single-center study was performed. The participants were followed up for every 6 months or until death or transplantation. A chemiluminescent enzyme immunoassay was used to establish a baseline sTM.

RESULTS

Among the 219 patients with decompensated liver cirrhosis, 53.42% were caused by hepatitis B and hepatitis C. Plasma sTM levels were much higher in cirrhosis than in healthy controls and increased parallel with Child-Pugh classification ( P < 0.01) and the amount of ascites ( P = 0.04). After adjusting for sex, age, international normalized ratio, bilirubin, and other potential factors, multivariate Cox regression revealed that per TU/ml elevation of plasma sTM causes an increase of 8% in mortality, and per-SD elevation of thrombomodulin causes a 53% increase in mortality. As the mortality rates in low (5.90-12.60 TU/ml) and medium (12.70-18.00 TU/ml) sTM levels were similar, so we chose the cutoff of 18.00 TU/ml to divide into two groups, and K-M analysis indicated that patients with sTM >18.0 TU/ml demonstrated an additional 2.01 times death risk (95% CI, 1.13-7.93; P = 0.01) than those with sTM ≤18.0 TU/ml.

CONCLUSION

Plasma sTM in cirrhosis was significantly increased in parallel with the severity of liver dysfunction. sTM elevation than 18 TU/ml indicated a poor prognosis of decompensated liver cirrhosis.

Circulating Thrombomodulin: Release Mechanisms, Measurements, and Levels in Diseases and Medical Procedures

Thrombomodulin (TM) is a type-I transmembrane protein that is mainly expressed on endothelial cells and plays important roles in many biological processes. Circulating TM of different forms are also present in biofluids, such as blood and urine. Soluble TM (sTM), comprised of several domains of TM, is the major circulating TM which is generated by either enzymatic or chemical cleavage of the intact protein under different conditions. Under normal conditions, sTM is present in low concentrations (<10 ng/mL) in the blood but is elevated in several pathological conditions associated with endothelial dysfunction such as cardiovascular, inflammatory, infection, and metabolic diseases. Therefore, sTM level has been examined for monitoring disease development, such as disseminated intravascular coagulation (DIC), sepsis and multiple organ dysfunction syndrome in patients with novel coronavirus disease 2019 (COVID-19) recently. In addition, microvesicles (MVs) that contain membrane TM (MV-TM) have been found to be released from activated cells which also contribute to levels of circulating TM in certain diseases. Several release mechanisms of sTM and MV-TM have been reported, including enzymatic, chemical, and TM mutation mechanisms. Measurements of sTM and MV-TM have been developed and explored as biomarkers in many diseases. In this review, we summarize all these advances in three categories as follows: (1) release mechanisms of circulating TM, (2) methods for measuring circulating TM in biological samples, and (3) correlation of circulating TM with diseases. Altogether, it provides a whole picture of recent advances on circulating TM in health and disease.

Fibrinolytic markers could be useful predictors of severity in patients with pulmonary arterial hypertension: a retrospective study

Background

The severity of pulmonary arterial hypertension (PAH) is classified based on mean pulmonary artery pressure (mPAP) levels. However, other markers have not been elucidated. Fibrinolytic markers, such as total plasminogen activator inhibitor-1 (tPAI-1) and thrombomodulin (TM), are known to reflect arterial endothelial function. However, the relationship between serum tPAI-1, TM and pulmonary circulation has not been completely determined.

Methods

This study included 100 consecutive patients (38 men), with a mean age of 68.9 ± 12.0 years, with cardiac diseases who underwent right heart catheterization. Serum coagulation and fibrinolytic marker levels were measured.

Results

The average mPAP value was 25.1 ± 13.1 mmHg for all patients. The mPAP levels revealed a significant positive correlation with serum tPAI-1 (ρ = 0.24, p = 0.042) and uric acid (ρ = 0.29, p = 0.0031) levels. In the group with mPAP levels less than 25 mmHg (n = 58, ave. 17.3 ± 4.3 mmHg), mPAP levels showed a significant positive correlation with serum tPA-1 (ρ = 0.34, p = 0.034) and TM (ρ = 0.34, p = 0.043) values. The mean tPAI-1 (29.8 ± 23.3 ng/ml, p = 0.047) and uric acid (5.7 ± 1.8 mg/dl, p = 0.026) levels were significantly less in those with lower mPAP levels. A multivariate analysis revealed that tPAI-1 alone was a significant independent characteristic marker of PAH (odds ratio 1.02, 95%CI 1.000–1.036, p = 0.034).

Conclusions

These results indicate that serum tPAI-1 and TM may be useful predictors of severity, similar to mPAP in patients with PAH. They could be beneficial in predicting PAH among patients in the early stage of the disease.

Serological tests for diagnosis and staging of hand-arm vibration syndrome (HAVS)

The current gold standard for the diagnosis and staging of hand-arm vibration syndrome (HAVS) is the Stockholm workshop scale, which is subjective and relies on the patient's recalling ability and honesty. Therefore, great potentials exist for diagnostic and staging errors. The purpose of this study is to determine if objective serum tests, such as levels of soluble thrombomodulin (sTM) and soluble intercellular adhesion molecule-1 (sICAM-1), may be used in the diagnosis and staging of HAVS. Twenty two nonsmokers were divided into a control group (n = 11) and a vibration group (n = 11). The control group included subjects without history of frequent vibrating tool use. The vibration group included construction workers with average vibrating tool use of 12.2 years. All were classified according to the Stockholm workshop scale (SN, sensorineural symptoms; V, vascular symptoms. SN0, no numbness; SN1, intermittent numbness; SN2, reduced sensory perception; SN3, reduced tactile discrimination; V0, no vasospasmic attacks; V1, intermittent vasospasm involving distal phalanges; V2, intermittent vasospasm extending to middle phalanges; V3, intermittent vasospasm extending to proximal phalanges; V4, skin atrophy/necrosis). All control subjects were SN0 V0. Seven out of 11 vibration subjects were SN1 V1, and 4 out of 11 were SN1 V2. A 10-cm(3) sample of venous blood was collected from each subject. The sTM and sICAM-1 levels were determined by enzyme-linked immunosorbent assay. The mean plasma sTM levels were as follows: control group = 2.93 +/- 0.47 ng/ml, and vibration group = 3.61 +/- 0.24 ng/ml. The mean plasma sICAM-1 levels were as follows: control group = 218.8 +/- 54.1 ng/ml, and vibration group = 300.3 +/- 53.2 ng/ml. The sTM and sICAM-1 differences between control and vibration groups were statistically significant (p < 0.0002 and p < 0.001, respectively). When reference ranges provided by Hemostasis Reference Lab were used as cut-off values, all sTM and sICAM-1 levels were within range, except three vibration individuals (27%) who had sICAM-1 levels greater than the reference range. This was not statistically significant (p = 0.08). When subjects were compared based on the Stockholm workshop scale, mean plasma sTM levels were SN0 V0 group = 2.93 +/- 0.47 ng/ml, SN1 V1 group = 3.59 +/- 0.25 ng/ml, and SN1 V2 group = 3.65 +/- 0.27 ng/ml, and mean plasma sICAM-1 levels were SN0 V0 = 219 +/- 54.1 ng/ml, SN1 V1 = 275 +/- 33.5 ng/ml, and SN1 V2 = 345 +/- 54.6 ng/ml. The difference in sTM level among the three groups was statistically significant (p < 0.001). The difference in sICAM-1 level among the three groups was also statistically significant (p < 0.002). The sTM and sICAM-1 levels are statistically higher in subjects with HAVS, with levels proportional to the disease severity. However, large population studies are needed to determine the "real-life" standard reference ranges for sTM and sICAM-1.

Decreased plasma soluble thrombomodulin levels as a risk factor for pulmonary thromboembolism

OBJECTIVE

To observe the changes of the plasma soluble thrombomodulin (sTM) concentrations in patients with pulmonary thromboembolism (PTE) and assess the association between plasma sTM concentration and the risk of PTE.

PATIENTS AND METHODS

We measured plasma concentrations of sTM, protein C (PC) and protein S (PS) and examined the association between those plasma markers and the risk of PTE in 72 selected PTE patients and 70 controls.

RESULTS

Significant difference was identified in plasma sTM level between overall PTE patients and controls. Female PTE patients had statistically lower sTM concentrations than male patients. A positive linear correlation was found between plasma sTM concentration and age in female patients. Decreased plasma sTM concentration was associated with a continuously and progressively increased risk for PTE in women. The concentrations of plasma PC and PS did not differ between groups and no significant quantitative association was identified between the risk of PTE and the levels of plasma PC or PS.

CONCLUSION

Decreased plasma sTM concentration is associated with an increased risk of PTE in women.

Cell-derived microparticles and exosomes in neuroinflammatory disorders

All blood cells and the vascular endothelium shed microparticles (MP) from their plasma membranes when suitably stimulated, and assay of MP in patient blood has found increasing application to the monitoring of disease states. In addition, mounting evidence suggests that MP are not mere epiphenomena but play significant roles in the pathophysiology of thromboses, inflammation, and cancers. This chapter endeavors to summarize the limited number of studies thus far done on MP in neurological disorders such as multiple sclerosis (MS), transient ischemic attacks, and the neurological manifestations of antiphospholipid syndrome (APS). In addition, the chapter offers some plausible hypotheses on possible roles of MP in the pathophsyiology of these disorders, chiefly, the hypothesis that MP are indeed important participants in some neuropathologies, especially those which are ischemic in nature, but probably also inflammatory ones. The chapter also goes over the history and general principles of MP studies (e.g., assay methods and pitfalls), comparison with alternative methods (e.g., soluble markers of disease states), subclasses of MP (such as exosomes), and other topics aimed at helping readers to consider MP studies in their own clinical fields. Tables include a listing of bioactive agents known to be carried on MP, many of which were heretofore considered strictly soluble, and some of which can be transferred from cell to cell via MP vectors, for example certain cytokine receptors.

Expression patterns and action analysis of genes associated with blood coagulation responses during rat liver regeneration

AIM: To study the blood coagulation response after partial hepatectomy (PH) at transcriptional level.

METHODS: After PH of rats, the associated genes with blood coagulation were obtained through reference to the databases, and the gene expression changes in rat regenerating liver were analyzed by the Rat Genome 230 2.0 array.

RESULTS: It was found that 107 genes were associated with liver regeneration. The initially and totally expressing gene numbers occurring in initiation phase of liver regeneration (0.5-4 h after PH), G₀/G₁ transition (4-6 h after PH), cell proliferation (6-66 h after PH), cell differentiation and structure-function reconstruction (66-168 h after PH) were 44, 11, 58, 7 and 44, 33, 100, 71 respectively, showing that the associated genes were mainly triggered in the forepart and prophase, and worked at different phases. According to their expression similarity, these genes were classified into 5 groups: only up-, predominantly up-, only down-, predominantly down-, up- and down-regulation, involving 44, 8, 36, 13 and 6 genes, respectively, and the total times of their up- and down-regulation expression were 342 and 253, respectively, demonstrating that the number of the up-regulated genes was more than that of the down- regulated genes. Their time relevance was classified into 15 groups, showing that the cellular physiological and biochemical activities were staggered during liver regeneration. According to gene expression patterns, they were classified into 29 types, suggesting that their protein activities were diverse and complex during liver regeneration.

CONCLUSION: The blood coagulation response is enhanced mainly in the forepart, prophase and anaphase of liver regeneration, in which the response in the forepart, prophase of liver regeneration can prevent the bleeding caused by partial hepatectomy, whereas that in the anaphase contributes to the structure-function reorganization of regenerating liver. In the process, 107 genes associated with liver regeneration play an important role.

Endothelial protein C receptor plasma levels increase in chronic liver disease, while thrombomodulin plasma levels increase only in hepatocellular carcinoma

INTRODUCTION

Thrombomodulin (TM) and endothelial protein C receptor (EPCR) are two transmembrane endothelial receptors involved in the protein C pathway, that regulates coagulation and inflammation processes. We postulated that soluble thrombomodulin and EPCR are plasmatic markers of progression to hepatocellular carcinoma (HCC) and prognostic indicators in cirrhotic patients.

MATERIALS AND METHODS

Plasma levels of TM and EPCR were measured in 104 patients affected by different stages of liver diseases (66 patients with HCC, and 38 without HCC), and in 52 healthy controls.

RESULTS

EPCR levels were higher in patients than in controls (239+/-1.8 ng/mL vs. 127+/-1.5 ng/mL, p<0.0001). TM levels were higher in patients with HCC than in those without (42.1+/-2.0 ng/mL vs. 28.3+/-2.1 ng/mL; p=0.039), while EPCR levels were similar in the two groups. No association between TM and clinical outcome was found, while high levels of EPCR were associated with death and thrombosis of the portal vein.

CONCLUSIONS

We surmise a possible role for high levels of TM as a marker of HCC development in patients with cirrhosis, whereas high levels of EPCR are a possible marker of worse HCC prognosis, being a sign of endothelial damage of large vessels.

Recombinant human factor VIIa-induced alterations in tissue factor and thrombomodulin in patients with advanced liver cirrhosis

BACKGROUND

Recombinant human factor VIIa (rhFVIIa) is used to treat hemophilia and occasionally individuals with liver disease. The aim of the present study was to investigate the consequences of rhFVIIa in individuals with advanced liver disease in an attempt to understand the mechanism of action of rhFVIIa in this unique population.

METHODS

Levels of plasma tissue factor, plasminogen activator inhibitor-1, tissue factor pathway inhibitor, fibrin split products, D-dimers and free thrombomodulin were measured following the administration of rhFVIIa in 17 subjects. The results were compared to normal controls.

RESULTS

The prothrombin time declined from 20.2 +/- 2.8 s to 14.3 +/- 3.9 s (P < 0.01). No change in the activated partial thromboplastin time occurred. A 15.6% reduction in thrombomodulin was observed (P < 0.05). A mean 75.2% reduction in plasma tissue factor occurred (P < 0.01). Tissue factor pathway inhibitor levels declined to less than the control value (P < 0.05). No changes in plasminogen activator inhibitor-1, fibrin split products or D-dimer levels occurred.

CONCLUSIONS

These data demonstrate that rhFVIIa administration to individuals with liver disease results in (i) a transient improvement in the prothrombin time; (ii) no change in the activated partial thromboplastin time; and (iii) a marked reduction in the levels of thrombomodulin and tissue factor. These data suggest that rhFVIIa binds tissue factor and enhances tissue factor and thrombomodulin clearance from the circulation.

Plasma and hepatic tissue levels of thrombomodulin, tissue factor, NFkappaB and nitric oxide in responders and nonresponders to IFNalpha therapy

Hepatitis C virus (HCV) infects hepatocytes and utilizes the hepatocyte to replicate. In so doing, many hepatocyte activities are shifted from their native state to one reflecting liver cell stress. Thrombomodulin and tissue factor are endothelial cell proteins that are expressed as a result of tissue injury or stress. Urokinase is a serine protease, which has been implicated in a number of physiologic and pathologic processes related to cellular stress and or injury. Nitric oxide is produced by cells in response to injury and functions both as a vasodilator and as an activator of a large number of cytokine cascades. NFkappaB is a transcription factor that forms one of the first lines of cellular defense against infection and hepatocellular stress. The levels of these four factors in plasma, hepatocyte cytosol and hepatocyte nuclear extracts provide a precise panoramic measure of cellular stress. Plasma, hepatocyte cytosol and nuclear extracts of hepatocytes were assayed for these four factors in 17 patients treated with alphaIFN for chronic hepatitis C. Five of the 17 were responders while 12 were nonresponders. Ten normal controls and 1 normal control liver were assayed also for each parameter. Nonresponders had 2x the plasma urokinase levels of responders and normals. The cytosol prepared from hepatocytes of nonresponders had a urokinase level 15-fold that of the controls and responders to IFN therapy. Plasma thrombomodulin levels in nonresponders were sixfold greater than those of responders and controls. The levels of all of the other measures in plasma, cytosol and nuclear extracts of liver tissue varied minimally between responders and nonresponders and the normal controls. These data demonstrate that: (i) urokinase levels in plasma and more clearly in cytosol are greater in nonresponders than responders, and (ii) plasma thrombomodulin levels in nonresponders are sixfold greater than those of responders and controls. These data suggest that urokinase and thrombomodulin may be unique markers of cellular and endothelial stress present in individuals with chronic hepatitis C. These markers might be useful during the clinical course of chronic hepatitis C, as a means of gauging the tissue response to therapy.

Bacterial lipopolysaccharide decreases thrombomodulin expression in the sinusoidal endothelial cells of rats -- a possible mechanism of intrasinusoidal microthrombus formation and liver dysfunction

BACKGROUND/AIMS

To elucidate the mechanism of liver dysfunction occurring in patients with sepsis, we evaluated the effect of bacterial lipopolysaccharide (LPS) on the expression of thrombomodulin (TM) in rat sinusoidal endothelial cells (SECs) and the therapeutic efficacy of exogenous recombinant TM.

METHODS

We induced endotoxemia in rats by bolus intraperitoneal injection of LPS. TM antigen levels within tissues were assessed by immunohistochemistry. We measured TM in cultured SECs by enzyme immunoassay, functional analysis and real-time polymerase chain reaction (PCR).

RESULTS

TM antigen and activity levels were significantly decreased in SECs isolated from LPS-treated rats after 3 and 6 h treatment, and recovered after 12 h treatment, correlating with immunohistochemical observations. In contrast, TM messenger RNA was decreased after 6 and 12 h treatment, and slightly recovered after 24 h treatment. TM expression in cultured SECs isolated from normal rats was also reduced after treatment with LPS and tumor necrosis factor (TNF)-alpha in vitro. The increased levels of serum fibrin degradation products (FDP), fibrin deposition within liver sinusoids, injury of SECs and liver dysfunction induced by LPS in our rat model was improved by recombinant TM treatment.

CONCLUSIONS

Decreased TM expression in SECs of LPS-treated rats may result in intrasinusoidal microthrombus formation and subsequent liver dysfunction during sepsis.

Tissue factor and thrombomodulin in hemodialysis patients: associations with endothelial injury, liver disease, and erythropoietin therapy

Patients receiving maintenance hemodialysis (HD) present with hemostatic abnormalities, which may be aggravated by comorbid conditions, especially liver disease. The factors that influence plasma levels of thrombomodulin (TM), an initiator of the anticoagulant protein C pathway, and those of tissue factor (TF), which triggers the extrinsic coagulation pathway, were assessed. In 63 HD patients, TM and TF levels were higher than those in healthy controls. In bivariate analysis, TF positively correlated with TM, and both were directly associated with the presence of viral hepatitis B or C marker, serum liver enzymes, use of erythropoietin therapy, hemoglobin levels, and duration of HD therapy, and inversely correlated with body mass index. TF was also positively associated with plasma von Willebrand factor (vWF) antigen, and inversely associated with activated partial thromboplastin time. In multivariate analysis, increased vWF, alanine aminotransferase, and use of erythropoietin independently predicted both TF and TM levels. HD patients with vWF and ALT levels lower than middle, and not treated with erythropoietin had normal TF but increased TM concentrations compared with levels in healthy controls. Increased plasma levels of TM and TF in patients on maintenance HD are surrogates of vascular endothelial injury. Liver disease and use of erythropoietin treatment are also important determinants of these markers, and should be considered in further studies.

Tissue factor and thrombomodulin levels are correlated with stage of cirrhosis in patients with liver disease

Liver cirrhosis is associated with alterations of the coagulation system commonly causing bleeding as well as thromboembolic complications. The potential pathophysiological roles of tissue factor (TF) (the initiator of the extrinsic coagulation pathway) and thrombomodulin (TM) (an initiator of the anticoagulatory protein C pathway) are unknown. We therefore measured plasma concentrations of TF and TM in 111 patients with liver diseases who were evaluated for liver transplantation. We could demonstrate that the levels of both molecules increased with the Child's class of liver cirrhosis, independently of aetiology. TM was significantly elevated in Child A, B and C patients compared with patients without cirrhosis; TF only in Child C patients. The plasma TM and TF concentrations correlated with prothrombin time, activated partial thromboplastin time, and inversely with factor VII activity, cholinesterase serum activity, and serum albumin concentration. TM was elevated in patients with a bleeding tendency, but TM and TF did not differ between patients with or without prior thrombotic events. Further studies are warranted to clarify the underlying mechanisms that raise TM and TF plasma levels in liver disease with possible clinical consequences.

Soluble thrombomodulin is associated with viral hepatitis, blood pressure, and medications in haemodialysis patients

BACKGROUND

The level of soluble thrombomodulin (sTM), a traditional marker of endothelial injury, is also dependent on renal excretory function. We studied serum sTM in chronic haemodialysis (HD) patients to determine which factors are predictive of its levels in this population.

METHODS AND RESULTS

sTM levels of 10.7 (5.72-30.7) ng/ml in 100 HD patients were higher than in 30 controls (P<0.0001). In a bivariate regression analysis, immunoreactive sTM was positively associated with the presence of hepatitis B virus surface antigen and/or anti-hepatitis C virus antibodies measured by third generation ELISAs (P<0.0001), and was related to certain markers of liver injury and biosynthetic dysfunction. sTM was also directly associated with time on dialysis (P=0.001), or use of unfractionated heparin (UFH) (vs enoxaparin) (P=0.0007), erythropoietin (P=0.008), ACE-inhibitors (P=0.034), acetate-buffered dialysate (vs bicarbonate) (P=0.040), pre-dialysis systolic (P=0.012), and diastolic blood pressure (P=0.043). It was negatively associated with lipoprotein(a) (P=0.029). sTM was not related to age, sex, smoking, cause of renal failure, prevalence of cardiovascular disease, amount of HD delivered, preserved residual renal function, ferritin, C-reactive protein, and other vasoactive medications used. In a multivariable analysis, a positive hepatitis marker (P=0.0002), the use of UFH (P=0.030) and erythropoietin (P=0.019), and raised pre-dialysis blood pressure (P=0.024) were positive independent predictors of high sTM level.

CONCLUSION

These data indicate that, in addition to endothelial activation, elevated sTM levels in HD patients may be related to viral infection and/or liver dysfunction, and influenced by modifiable factors such as increased blood pressure, and the type of heparin and erythropoietin treatment used.

Elevation of soluble thrombomodulin antigen levels in the serum and urine of streptozotocin-induced diabetes model rats

The present study was designed to evaluate the serum thrombomodulin (TM) antigen levels, the TM content in several tissues, and vascular endothelium injury in a streptozotocin-induced diabetic mellitus model of rats with the basic observations concerning soluble serum TM antigen. The soluble TM antigen levels in the serum of 1-week-old Sprague-Dawley rats were 1028.7+/-56.8 ng/mL in the immunoassay using rabbit anti-rat TM IgG. The levels gradually decreased to about 400 ng/mL within 11 weeks during the development, and the levels in 11-week-old rats were preserved up to 31 weeks of age (experimental period). Identical patterns of five kinds of TM antigen subspecies (105, 52, 46, 31, and 28 kDa) in the serum were observed during normal development from 1 to 31 weeks in the Western blotting under reducing conditions. Soluble TM antigen levels in the serum and urine of the model rats were significantly increased to 1. 3 times the levels in the buffer-administrated control rats without an increase in the serum creatinine levels. In contrast to the TM antigen levels in the serum and urine, the TM content in several tissues including the lung, pancreas, kidney, and spleen of the model rats significantly decreased by 47% to 10% of those in the buffer-administrated control rats. Flattening of the longitudinal ridges in the endothelium, crevasse-like endothelial sloughing, platelet activation and aggregation, and/or leukocyte adherence on the endothelium were observed in the aorta of the model rats based on scanning electron microscopic observations, indicating endothelium injury. The present results indicate that the serum TM antigen levels increased with injury to the endothelium in the model, even when renal dysfunction was not present. It is suggested that increased TM antigen levels in diabetic patients could reflect endothelium injury as observed in this diabetic model experiment.