Expression of matrix metalloproteinase-9 (MMP-9) in human skin within 1 hour after injury through immunohistochemical staining: a pilot study.

Matrix metalloproteinase-9 (MMP-9) is involved in tissue remodeling and in skin wound healing. The present study focuses on the MMP-9 expression in epidermal wound healing within 1 h after injury, to test whether MMP-9 can be used to estimate the time of injury in forensic practice.A sample consisting of 5 individuals undergoing surgery was analyzed. With the consent of the patients, sections of skin were removed from the surgical wound at predefined time intervals. For each subject, 8 sections were taken, one for each time interval defined at 0 '- 1' - 3 '- 5' - 10 '- 15' - 30 '- 60' minutes. The specimens were immunostained with MMP-9, and the number of positively stained cells was examined.The number of positively stained cells showed an increasing trend as a function of time. Less than 30 positively stained cells were found in all cases within 3 min. At the post-infliction time of 5 min, the number of positively stained cells exceeded 30 in 3 out of 5 cases. The number of MMP-positive cells exceeded 40 in all cases in over 10 min.In the light of these results, the count of MMP-9 positive cells might be a useful marker in the wound-age estimation within 1 h in forensic setting. More research is required to collect more samples and to compare samples from the hyperacute phase with those from several days after injury.

Immunohistochemical analysis of PDGFR-α for wound age determination.

Immunohistochemical analysis of platelet-derived growth factor receptor-α (PDGFR-α) was performed on human skin wounds obtained from forensic autopsy cases. Thirty human skin wounds were collected at different post-infliction intervals as follows: Group I, 4 h to 3 days (n = 16); Group II, 4 to 7 days (n = 7); Group III, 9 to 10 days (n = 3); and Group IV, 14 to 20 days (n = 4). Immunopositive reactions for PDGFR-α were not observed in the uninjured human skin specimens. In a semi-quantitative morphometrical analysis, the number of PDGFR-α-positive cells was observed increased in Group II, with the average number of PDGFR-α-positive cells being the highest in Group II. Additionally, in Group II, all specimens showed PDGFR-α-positive cells, with an average number of > 200 cells in five fields of view, suggesting a wound age of 4 to 7 days. Taken together, the immunohistochemical detection of PDGFR-α in human skin wounds can be a useful tool for wound age determination.

A case of hemoperitoneum after percutaneous radiofrequency ablation in a patient with hepatocellular carcinoma.

We report a case of hemoperitoneum after percutaneous radiofrequency ablation in a patient with hepatocellular carcinoma. A 60-year-old female was hospitalized for the treatment of thrombasthenia and cirrhosis caused by chronic Hepatitis C, and computed tomography revealed hepatocellular carcinoma, which was treated by percutaneous radiofrequency ablation. After the ablation, hemoperitoneum was suspected because of the low hemoglobin level with abdominal pain. Approximately 6 h after the ablation treatment, the patient suddenly fell into a shock state and died. In this case, medical treatment-related death including malpractice was suspected, and forensic autopsy was performed. The abdominal cavity contained 910 mL of dark red fluid blood and 210 g of soft hemocoagula. Moreover, several puncture marks were observed on the liver surface and diaphragm, and there was no clear damage to the main arteries and veins. Considering the macroscopic and microscopic findings, the cause of death was assumed as hemorrhagic shock due to the hemoperitoneum caused by the damage to the liver by radiofrequency ablation. It is important to consider all the indications and adverse effects of radiofrequency ablation.

Essential Involvement of Neutrophil Elastase in Acute Acetaminophen Hepatotoxicity Using BALB/c Mice.

Intense neutrophil infiltration into the liver is a characteristic of acetaminophen-induced acute liver injury. Neutrophil elastase is released by neutrophils during inflammation. To elucidate the involvement of neutrophil elastase in acetaminophen-induced liver injury, we investigated the efficacy of a potent and specific neutrophil elastase inhibitor, sivelestat, in mice with acetaminophen-induced acute liver injury. Intraperitoneal administration of 750 mg/kg of acetaminophen caused severe liver damage, such as elevated serum transaminase levels, centrilobular hepatic necrosis, and neutrophil infiltration, with approximately 50% mortality in BALB/c mice within 48 h of administration. However, in mice treated with sivelestat 30 min after the acetaminophen challenge, all mice survived, with reduced serum transaminase elevation and diminished hepatic necrosis. In addition, mice treated with sivelestat had reduced NOS-II expression and hepatic neutrophil infiltration after the acetaminophen challenge. Furthermore, treatment with sivelestat at 3 h after the acetaminophen challenge significantly improved survival. These findings indicate a new clinical application for sivelestat in the treatment of acetaminophen-induced liver failure through mechanisms involving the regulation of neutrophil migration and NO production.

Intrathrombotic appearances of AQP-1 and AQP-3 in relation to thrombus age in murine deep vein thrombosis model.

Aquaporins (AQPs) are membrane-bound proteins for water transportation and are useful for diagnosing drowning and wound vitality in forensic pathology. Here, we examined intrathrombotic expression of AQP-1 and AQP-3 using deep vein thrombosis models in mice. To perform immunohistochemical analyses, we used anti-AQP-1 and anti-AQP-3 antibodies. In thrombus samples with the post-ligation intervals of 1 to 5 days, AQP-1+ areas were over 70%. At 7 days after the IVC ligation, AQP-1+ areas became less than 50%, eventually decreasing to 11% at 21 days. At 3 days after the IVC ligation, AQP-3+ cells started to appear from the peripheral area. Thereafter, the positive cell number progressively increased and reached to a peak at 10 days after the IVC ligation. When the intrathrombotic AQP-1+ area was as large as the intrathrombotic collagen area or smaller, it would indicate a thrombus age of ≥ 10 days. AQP-3+ cell number of > 30 would indicate a thrombus age of 10-14 days. Collectively, our study implied that the detection of AQP-1 and AQP-3 would be useful for the determination of thrombus age.

Complete decapitation by a self-constructed guillotine in a burned body - complex suicide or postmortem burning?

We report a suicide case of complete decapitation using a self-constructed guillotine. A 45-year-old man, whose body was severely burned, was found dead. The head was completely separated from the middle level of the neck, and a sharp blade with a steel frame was placed between the head and neck. The severance plane passed between the C4 and C5 vertebrae. Vital reactions such as hemorrhage could not be confirmed at the decapitated skin edge because the body was severely burned. Both common carotid arteries were sharply transected. Subendocardial hemorrhage was detected in the left ventricle. Only a little blood, but no soot, was detected in the respiratory tract, including the trachea and bilateral bronchi. Subarachnoid hemorrhage was noted at the edge of the cervical spinal cord. The saturation level of CO-Hb was 5.7% in the left cardiac blood, 5.9% in the right cardiac blood, and 5.8% in the peripheral blood from the femoral vein. Cervical transection was diagnosed as the cause of death. We believe that he was unintentionally burned by spread fire from an automobile after decapitation by a self-constructed guillotine.

The application of autophagy to thrombus age estimation in murine deep vein thrombosis model.

We immunohistochemically examined the intrathrombotic dynamics of autophagy during thrombogenesis using murine deep vein thrombosis (DVT) models. To perform the immunohistochemical analyses, we used anti-LC3 antibody and anti-p62 antibody for detecting the intrathrombotic autophagic functions. We estimated dynamics of the intrathrombotic autophagy as LC3+ cell number (×1000, five fields) with the thrombus ages (each group n = 5). The number of LC3+ cells was once decreased at 3 days, and then increased until 10 days. On the contrary, the number of p62+ cells progressively increased until 10 days after the inferior vena cava (IVC) ligation, and then gradually decreased. Especially, in all of thrombus samples with the postligation intervals of 5-10 days, both numbers were larger than 10. Subsequently, we compared the number of LC3+ cells to that of p62+ cells. Although, at 1 day after the IVC ligation, LC3+ cell number significantly exceeded p62+ cell number, the former was significantly or relatively less than the latter at 3 days or more after the IVC ligation. Thus, positive cells of > 10 in both LC3 and p62 indicated the thrombus age of 5-10 days. Upon comparison of immunopositive cells in LC3 and p62, the p62/LC3 ratio was > 1.0 in 29 out of 30 thrombus samples aged 3-21 days, and all of 1-day-old thrombus had the p62/LC3 ratio of < 0.5. Thus, the ratio of > 1.0 and that of < 0.5 could indicate thrombus age of 3 days or more and that of 1 day, respectively. Collectively, our study implied that the detection of autophagy-related molecules such as LC3 and p62 would be useful for the determination of thrombus age.

A case of complex suicide due to acute nicotine intoxication caused by cigarette ingestion.

This paper presents an unusual complex suicide case that died of nicotine addiction. The deceased was a 40-year-old male who was found lying dead on the floor in his room. In external findings, many incision wounds on his forearms and skin discoloration with epidermolysis on his cervical region could be seen. In the room, a blood-stained scissors and electric cord hanged on the exercise bike were found. Moreover, nine cigarette residues which were only the filter part and empty bottle of coffee were found on his side. At autopsy, we found that those injuries were not serious enough to lead him to the death. Toxicologically, caffeine, nicotine, cotinine, mirtazapine, and olanzapine could be detected, and the concentrations of nicotine were 3.740, 2.140, 3.100, and 451.100 µg/ml in cardiac blood, peripheral blood, urine, and stomach contents, respectively. These concentrations were evaluated as the fatal levels, and the cause of his death was diagnosed as acute nicotine intoxication.

Forensic pathological study on temporal appearance of dendritic cells in skin wounds.

Dendritic cells (DCs) can essentially contribute to innate and adaptive immune system in various organs. A double-color immunofluorescence analysis was carried out with anti-CD11c and -HLA-DRα antibodies to detect DCs in 53 skin wounds (their postinfliction intervals: group I, 0-3 days; group II, 4-7 days; group III, 9-14 days; and group IV, 17-21 days). CD11c+HLA-DRα+ DCs were first observed in skin wounds with postinfliction intervals of 3 days, and the DC numbers were found to be elevated in skin wounds with the subsequent increase in postinfliction intervals. Semi-quantitative morphometric analyses showed that the DC number was the highest in the 12-day-old wound. More than 50 DCs were present in 8 of 10 samples (80%) in group II and 14 of 16 samples (87.5%) in group III, and there was no difference between the two groups. Thus, the presence of DCs in a skin wound was possibly estimated as postinfliction intervals of at least 3 days. Furthermore, when a skin wound contained > 50 DCs, its age would be judged as 4-14 days. Collectively, the appearance of DCs in human skin wounds may provide useful information in determining the age of a wound.

Programmed cell death ligand 1 disruption by clustered regularly interspaced short palindromic repeats/Cas9-genome editing promotes antitumor immunity and suppresses ovarian cancer progression.

Programmed cell death ligand 1 (PD-L1) on tumor cells suppresses anti-tumor immunity and has an unfavorable prognostic impact in ovarian cancer patients. We herein report the pathophysiological and therapeutic impacts of PD-L1 disruption in ovarian cancer. PD-L1 was genetically disrupted in the murine ovarian cancer cell line ID8 using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome editing. PD-L1 knockout (KO) and control ovarian cancer cells were intraperitoneally inoculated into syngeneic mice, and survival and tumor dissemination were evaluated. Survival times were significantly longer in the PD-L1-KO ID8-inoculated groups than in their control groups, and its therapeutic benefit was enhanced in combination with the cisplatin treatment. Tumor weights and ascites volumes were significantly lower in the PD-L1-KO ID8 groups than in their control groups. Immunohistochemical and immunofluorescence analyses showed that intratumoral CD4+ T cells, CD8+ T cells, NK cells and CD11c+ M1 macrophages were significantly increased, whereas regulatory T cells were significantly decreased in the PD-L1-KO ID8 groups compared with those in their control groups. The intratumoral mRNA expression of interferon-γ, tumor-necrosis factor-α, interleukin (IL)-2, IL-12a, CXCL9 and CXCL10 was significantly stronger, while that of IL-10, vascular endothelial growth factor, CXCL1 and CXCL2 was significantly weaker in the PD-L1-KO ID8 groups. These results indicate that CRISPR/Cas9-mediated PD-L1 disruption on tumor cells promotes anti-tumor immunity by increasing tumor-infiltrating lymphocytes and modulating cytokine/chemokine profiles within the tumor microenvironment, thereby suppressing ovarian cancer progression. These results suggest that PD-L1-targeted therapy by genome editing may be a novel therapeutic strategy for ovarian cancer.

Contribution of the TNF-α (Tumor Necrosis Factor-α)-TNF-Rp55 (Tumor Necrosis Factor Receptor p55) Axis in the Resolution of Venous Thrombus.

Objective- Deep vein thrombosis results from a combination of risk factors including genetic conditions, obesity, drugs, pregnancy, aging, and malignancy. We examined pathophysiological roles of the TNF-α (tumor necrosis factor-α)-TNF-Rp55 (tumor necrosis factor receptor p55) axis in thrombus resolution using Tnfrp55-/- (TNF-Rp55-deficient) mice. Approach and Results- On ligating the inferior vena cava of wild-type (WT) mice, venous thrombi formed and grew progressively until 5 days but shrunk to <50% of the thrombus weight at day 14. Concomitantly, inferior vena cava ligation enhanced intrathrombotic gene expression of Tnfa and Tnfrp55, and intrathrombotic macrophages expressed both TNF-α and TNF-Rp55 proteins. In Tnfrp55-/- mice treated with the same manner, thrombus formed at a similar rate for 5 days, but shrinking was delayed compared with WT mice. Moreover, the blood flow recovery in thrombosed inferior vena cava was suspended in Tnfrp55-/- mice compared with WT mice. Intrathrombotic Plau (urokinase-type plasminogen activator), Mmp2 (matrix metalloproteinase 2), and Mmp9 (matrix metalloproteinase 9) mRNA expression was significantly reduced in Tnfrp55-/- mice, compared with WT ones. Supportingly, the administration of anti-TNF-α antibody or TNF-α inhibitor (etanercept) delayed the thrombus resolution in WT mice. Furthermore, TNF-α treatment enhanced gene expression of Plau, Mmp2, and Mmp9 in WT macrophages but not Tnfrp55-/- macrophages. These effects were significantly suppressed by ERK (extracellular signal regulated kinase) and NF-κB (nuclear factor-kappa B) inhibitors. Therefore, the lack of TNF-Rp55 has detrimental roles in the thrombus resolution by suppressing PLAU, MMP-2, and MMP-9 expression. In contrast, TNF-α administration accelerated thrombus resolution in WT but not Tnfrp55-/- mice. Conclusions- The TNF-α-TNF-Rp55 axis may have essential roles in the resolution of venous thrombus in mice.

Suicide by plastic bag suffocation combined with the mixture of citric acid and baking soda in an adolescent.

We describe a case of suicidal asphyxiation using a plastic bag combined with carbon dioxide (CO2) gas. A 20-year-old male, whose head was covered with a plastic bag, was found dead in his room. In the plastic bag, there were two glass-made cups containing liquid-like substance. Through crime scene investigation by police staffs, a bottle of citric acid and a box of baking soda were also discovered in his room. The forensic autopsy revealed that there were neither lesions nor injuries in all of the organs. Moreover, any drugs and poisons could not be detected in blood samples. Based on autopsy findings and crime scene investigation, the cause of death was diagnosed as acute asphyxia due to CO2 intoxication by the mixture of citric acid with baking soda in the plastic bag. To the best of our knowledge, there are no medical literatures describing plastic bag suffocation combined with CO2 gas generated from citric acid and baking soda, which has been widely distributed as suicidal means through websites. This case report promotes forensic pathologists and medical coroners to emphasize that the Internet has a crucial role on a source of suicidal information or a promoter of suicide all over the world.

Forensic application of epidermal AQP3 expression to determination of wound vitality in human compressed neck skin.

In forensic practices, it is often difficult to determine wound vitality in compression marks of the neck with naked eyes. AQP1 and AQP3 are the major water channels associated with skin. Thus, we immunohistochemically examined the expression of AQP1 and AQP3 in neck skin samples to discuss their forensic applicability to determination of the wound vitality. Skin samples were obtained from 56 neck compression cases (hanging, 35 cases; strangulation, 21 cases). The intact skin from the same individual was taken as a control. Although AQP1 was immnunostained in dermal capillaries in both the neck compression marks and intact skin samples, there was no significant difference in the magnitude of AQP1 expression between both groups. On the contrary, AQP3-positive signals could be faintly detected in uninjured skin samples, and the positive signals seemed more intense in the keratinocytes in compression regions. Morphometrical analyses revealed that the ratio of AQP3-expressed keratinocytes was significantly enhanced in neck compression regions, compared with control groups. From the viewpoints of forensic pathology, immunohistochemical detection of AQP3 in the neck skin can be considered a valuable marker to diagnose the trace of antemortem compression.

Immunohistochemical analysis on aquaporin-1 and aquaporin-3 in skin wounds from the aspects of wound age determination.

Immunohistochemical investigation of aquaporin (AQP)1 and AQP3 was performed in human skin wounds obtained from forensic autopsy cases. A total of 55 human skin wounds of different postinfliction intervals were collected as follows: group I, 0-3 days (n = 16); II, 4-7 days (n = 11); III, 9-14 days (n = 16); and IV, 17-21 days (n = 12). In uninjured skin samples, AQP1 and AQP3 could be slightly detected in dermal vessels and keratinocytes, respectively. The percentage of AQP1+ vessels and the number of AQP3+ keratinocytes were apparently elevated in accordance with wound ages. The number of AQP3+ keratinocytes was distinctly evident in groups II and III. Morphometrically, both AQP1+ vessel area and AQP3+ cell number were markedly increased in group II, compared with other three groups. With regard to forensic safety, AQP1+ vessel area of over 5% would imply wound ages of 4-12 days. Moreover, the positive area of > 15% would suggest wound age of 7-10 days. Especially, most samples of skin wounds aged 5-10 days except for only one sample (a 10-day-old wound) showed AQP3+ cell number of > 300, and the remaining other samples had that of < 300. Thus, the AQP3+ cell number of > 300 would indicate wound ages of 5-10 days. Collectively, immunohistochemical analyses of AQP1 and AQP3 in human skin wounds would support the objective accuracy of wound age determination.

Severer lupus erythematosus-like skin lesions in MRL/lpr mice with homozygous Kitwsh/wsh mutation.

OBJECTIVE: To clarify the roles of mast cells (MCs) on the pathogenesis of lupus erythematosus (LE)-like skin lesions on MRL/lpr mice. METHODS: MRL/lpr mice were mated with C57BL/6-Kitwsh/wsh mice and the heterozygous F1 mice were 10 times backcrossed with the parental MRL/lpr to generate MRL/lpr-Kitwsh/wsh mice. MC-deficient MRL/lpr-Kitwsh/wsh mice were compared with MRL/lpr-Kit+/+ and MRL/lpr-Kitwsh/+ mice with intact MCs. RESULTS: MRL/lpr-Kitwsh/wsh mice developed skin lesions without infiltrating MCs. As similar skin lesions on MRL/lpr-Kit+/+ mice and MRL/lpr-Kitwsh/+ mice contain comparable number of MCs, these mice were collectively analyzed as MRL/lpr mice with MCs. Compared with MRL/lpr mice with MCs, skin lesions developed earlier and showed consistently higher severity, with significantly higher mRNA expressions of many inflammatory cytokines in the dorsal skin on MRL/lpr mice without MCs. Furthermore, survival rate was significantly lower in MRL/lpr mice without MCs. The number of infiltrating MCs significantly increased in association with the severity of skin lesions in MRL/lpr mice with MCs. CONCLUSIONS: These results demonstrated that MCs are infiltrated to suppress the progression of LE-like skin lesions in MRL/lpr mice.

Immunohistochemical detection of intrathrombotic fibrocytes and its application to thrombus age estimation in murine deep vein thrombosis model.

Deep vein thrombi are dissolved after fibrosis process along with an increase of thrombus age. Fibrocytes are circulating bone marrow-derived cells with mesenchymal features that potentially have a unique and critical function in fibrosis. In this study, a double-color immunofluorescence analysis was carried out by using anti-CD45 and anti-collagen type I antibodies to examine the time-dependent appearance of fibrocytes in the murine model of stasis-induced deep vein thrombosis. The thrombus ages were 1, 3, 5, 7, 10, 14, and 21 days. In a thrombus age of less than 5 days, CD45+ and collagen type I+ fibrocytes were never detected. The intrathrombotic fibrocytes were initially observed in thrombi aged 7 days, and their number increased with advances in thrombus age. In a quantitative morphometrical analysis, the average number of intrathrombotic fibrocytes was highest in 14-day-old thrombi, and all of the five samples aged 14 days had the fibrocyte number of more than 25, and in three out of them, the number of intrathrombotic fibrocytes was over 30. On the contrary, in all of thrombus samples with the postligation intervals of 10 and 21 days, the number of intrathrombotic fibrocytes was less than 25. These observations imply that thrombi containing fibrocytes are at least 7 days old and that a fibrocyte number exceeding 30 would indicate the thrombus age of approximately 14 days. Our observations indicate that the detection of fibrocytes could be useful for thrombus age determination.

Ventricular androgenic-anabolic steroid-related remodeling: an immunohistochemical study.

BACKGROUND: Several fatal cases of bodybuilders, following a myocardial infarction after long exposure to androgenic-anabolic steroids (AAS), are reported. In recent years, evidence has emerged of cases of heart failure related to AAS consumption, with no signs of coronary or aorta atherosclerosis. This study aims to further investigate the pathogenesis of the ventricular AAS-related remodeling performing immunohistochemistry (IHC). METHOD: In order to examine innate immunity activity and myocytes and endothelial cell apoptosis, IHC analyses were performed on heart tissue of two cases of bodybuilders who died after years of supratherapeutic use of metelonone and nandrolone and where no atherosclerosis or thrombosis were found, using the following antibodies: anti-CD68, anti-iNOS, anti-CD163, anti-CD 15, anti-CD8, anti-CD4, anti-HIF1 α, and in situ TUNEL staining. RESULTS: Results confirm the experimental findings of recent research that, in the absence of other pathological factors, if intensive training is combined with AAS abuse, myocytes and endothelial cells undergo apoptotic alterations. The absence of inflammatory reactions and the presence of an increased number of M2 macrophages in the areas of fibrotic remodeling confirm that the fibrotic changes in the heart are apoptosis-related and not necrosis-related. CONCLUSIONS: In conclusion, the study indicates that, in very young subjects with chronic hypoxia-related alterations of the heart, signs of a heart failure in the other organs and a history of AAS abuse, death can be ascribed to progressive heart failure due to the direct apoptotic cardiac and endothelial changes produced by AAS.

Detection of intrathrombotic endothelial progenitor cells and its application to thrombus age estimation in a murine deep vein thrombosis model.

Endothelial progenitor cells (EPCs), a newly identified cell type, are bone marrow-derived progenitor cells that co-express stem cell markers and Flk-1 (one of the receptors for vascular endothelial growth factor). In this study, double-color immunofluorescence analysis was performed using anti-CD34 and anti-Flk-1 antibodies in order to examine the time-dependent intrathrombotic appearance of EPCs, using the thrombi of DVT model mice with different thrombus ages (1-21 days). In thrombus cross-section specimens with an age of less than 3 days, CD34+/Flk-1+ EPCs were not detected. EPCs were initially observed in wounds aged 5 days, and their number was increased in thrombi with the advance of thrombus ages. The number of EPCs was the largest in the 10-day thrombus. Moreover, all 15 samples aged 7-14 days had an EPC number of more than 10, and, in 9 of them, the number of intrathrombotic EPCs was over 20. In contrast, in all thrombus samples aged 21 days, the number of intrathrombotic EPCs was less than 20. However, in three of them, the intrathrombotic EPC number was ≥ 10. These observations suggested that an intrathrombotic EPC number exceeding 20 would indicate a thrombus age of approximately 7-14 days.

Immunohistochemical detection of intrathrombotic IL-6 and its application to thrombus age estimation.

We immunohistochemically examined intrathrombotic IL-6 expression using a murine model of deep vein thrombosis induced by the ligation of the inferior vena cava (IVC) and discussed the availability of intrathrombotic IL-6 for thrombus age estimation. IL-6(+) cells could be first detected at 1 day after IVC ligation in three of five samples, and all samples with postligation intervals of 3 days or more had intrathrombotic IL-6(+) cells. Thereafter, the numbers of IL-6(+) cells were elevated with the increase of postligation intervals. Double-color immunofluorescence analyses demonstrated that IL-6 was mainly expressed by intrathrombotic macrophages. In all samples with postligation intervals of 5 days or less, the IL-6/macrophage ratio (IL-6/Mϕ) was <0.5. In contrast, the IL-6/Mϕ was greater than 0.5 at ≥7 days after the IVC ligation. These observations implied that IL-6/Mϕ ratios of >0.5 would strongly indicate thrombus ages of ≥7 days. Reciprocally, the ratios of less than 0.5 would suggest thrombus ages of ≤5 days. The present study demonstrated that the immunohistochemical detection of IL-6 was suitable to estimate the age of venous thrombi.