Temporal Electroencephalography Traits Dissociating Tactile Information and Cross-Modal Congruence Effects.

To explore whether temporal electroencephalography (EEG) traits can dissociate the physical properties of touching objects and the congruence effects of cross-modal stimuli, we applied a machine learning approach to two major temporal domain EEG traits, event-related potential (ERP) and somatosensory evoked potential (SEP), for each anatomical brain region. During a task in which participants had to identify one of two material surfaces as a tactile stimulus, a photo image that matched ('congruent') or mismatched ('incongruent') the material they were touching was given as a visual stimulus. Electrical stimulation was applied to the median nerve of the right wrist to evoke SEP while the participants touched the material. The classification accuracies using ERP extracted in reference to the tactile/visual stimulus onsets were significantly higher than chance levels in several regions in both congruent and incongruent conditions, whereas SEP extracted in reference to the electrical stimulus onsets resulted in no significant classification accuracies. Further analysis based on current source signals estimated using EEG revealed brain regions showing significant accuracy across conditions, suggesting that tactile-based object recognition information is encoded in the temporal domain EEG trait and broader brain regions, including the premotor, parietal, and somatosensory areas.

Xanthine Oxidoreductase-Mediated Superoxide Production Is Not Involved in the Age-Related Pathologies in Sod1-Deficient Mice.

Reactive oxygen species (ROS) metabolism is regulated by the oxygen-mediated enzyme reaction and antioxidant mechanism within cells under physiological conditions. Xanthine oxidoreductase (XOR) exhibits two inter-convertible forms (xanthine oxidase (XO) and xanthine dehydrogenase (XDH)), depending on the substrates. XO uses oxygen as a substrate and generates superoxide (O2•-) in the catalytic pathway of hypoxanthine. We previously showed that superoxide dismutase 1 (SOD1) loss induced various aging-like pathologies via oxidative damage due to the accumulation of O2•- in mice. However, the pathological contribution of XO-derived O2•- production to aging-like tissue damage induced by SOD1 loss remains unclear. To investigate the pathological significance of O2•- derived from XOR in Sod1-/- mice, we generated Sod1-null and XO-type- or XDH-type-knock-in (KI) double-mutant mice. Neither XO-type- nor XDH-type KI mutants altered aging-like phenotypes, such as anemia, fatty liver, muscle atrophy, and bone loss, in Sod1-/- mice. Furthermore, allopurinol, an XO inhibitor, or apocynin, a nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor, failed to improve aging-like tissue degeneration and ROS accumulation in Sod1-/- mice. These results showed that XOR-mediated O2•- production is relatively uninvolved in the age-related pathologies in Sod1-/- mice.

Intentional internal drainage tube method for nonlocalized persistent pancreatic leakage: a case report.

BACKGROUND: Persistent pancreatic leakage (PL) due to disconnected pancreatic duct syndrome (DPDS) is associated with severe morbidity and mortality and it usually treated with internal drainage. However, in cases without localized fistula formation, internal drainage is challenging to perform. We report an original one-stage surgical approach for nonlocalized persistent PL, namely, the "intentional internal drainage tube method". CASE PRESENTATION: A 49-year-old woman whose main pancreatic duct was penetrated during endoscopic retrograde cholangiopancreatography experienced severe PL. Peritoneal lavage and a second operation involving central pancreatectomy failed to relieve the symptoms, and nonlocalized PL persisted due to DPDS. Although we attempted a radical resection of the pancreatic remnants as a third strategy, the highly inflamed tissue and massive bleeding prevented the completion of the procedure. We sutured the pancreatic head margin and performed a pancreaticojejunostomy to the distal margin. Because these two cut margins could possibly be the source of the persistent PL, we created a hole at the Roux-en-Y jejunal limb, and a silicone drainage tube was inserted into the peritoneal space via this hole. Postoperatively, we continuously suctioned the intentional internal drainage tube, and the residual PL cavity gradually diminished. Even after removal of the tube, the residual PL drained internally into the jejunum through this hole. CONCLUSIONS: We present this intentional internal drainage tube method as a novel alternative approach for the management of nonlocalized PL consequential of DPDS. Due to the simplicity and minimally invasive nature of this method, we propose this technique may also be used to treat various types of nonlocalized persistent PL or be used prophylactically for central pancreatectomy.

Pathological Relationship between Intracellular Superoxide Metabolism and p53 Signaling in Mice.

Intracellular superoxide dismutases (SODs) maintain tissue homeostasis via superoxide metabolism. We previously reported that intracellular reactive oxygen species (ROS), including superoxide accumulation caused by cytoplasmic SOD (SOD1) or mitochondrial SOD (SOD2) insufficiency, induced p53 activation in cells. SOD1 loss also induced several age-related pathological changes associated with increased oxidative molecules in mice. To evaluate the contribution of p53 activation for SOD1 knockout (KO) (Sod1-/-) mice, we generated SOD1 and p53 KO (double-knockout (DKO)) mice. DKO fibroblasts showed increased cell viability with decreased apoptosis compared with Sod1-/- fibroblasts. In vivo experiments revealed that p53 insufficiency was not a great contributor to aging-like tissue changes but accelerated tumorigenesis in Sod1-/- mice. Furthermore, p53 loss failed to improve dilated cardiomyopathy or the survival in heart-specific SOD2 conditional KO mice. These data indicated that p53 regulated ROS-mediated apoptotic cell death and tumorigenesis but not ROS-mediated tissue degeneration in SOD-deficient models.

Oxidative stress and Liver X Receptor agonist induce hepatocellular carcinoma in Non-alcoholic steatohepatitis model.

BACKGROUND AND AIM: The incidence of non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC) is progressively increasing. However, the pathophysiology and etiology of NASH progression to HCC are unknown. We hypothesized that steatosis was the key factor in NASH-related hepatocarcinogenesis and aimed to evaluate the effects of long-term liver X receptor (LXR) agonist stimulation on hepatic steatosis induced by a high-fat diet and oxidative stress. METHODS: We used an LXR agonist (T0901317) and CCl4 to induce hepatic steatosis and oxidative stress, respectively. C57BL/6 mice fed with a high-fat diet were treated with either T0901317 + CCl4 (T09 + CCl4 group) or CCl4 alone (CCl4 group). T0901317 (2.5 mg/kg) and CCl4 (0.1 mL/kg) were intraperitoneally administered twice weekly for 24 weeks. RESULTS: The liver-to-body weight ratio was significantly higher in the T09 + CCl4 group than in the CCl4 group. Mice in the T09 + CCl4 group exhibited abnormal lipid metabolism and NASH-like histopathological features. Additionally, all mice in the T09 + CCl4 group developed liver tumors diagnosed as well-differentiated HCC. The genes identified via microarray analysis were related to NASH and HCC development. CONCLUSIONS: By combining long-term LXR agonist stimulation with oxidative stress and a high-fat diet, we successfully reproduced liver conditions in mice similar to those in humans with NASH and progression to HCC. Our results provide new insight into NASH-related HCC progression and therapy.

A novel hydrogel sheet prevents postoperative pancreatic fistula in a rat model.

AIM: To evaluate the efficacy of a novel hydrogel sheet in preventing postoperative pancreatic fistula (POPF). BACKGROUND: Postoperative pancreatic fistula is a life-threatening complication. As no study has reported the use of hydrogel sheets in preventing POPF, their effectiveness for that purpose remains unclear. METHODS: A novel hydrogel sheet made of polyvinyl alcohol (PVA) was prepared by the freeze-thaw method. The pancreatic ducts and surrounding pancreatic parenchyma of rats were transected to induce a pancreatic fistula. Next, the sheet was attached to the transection site. Ascitic fluid amylase and lipase concentrations were measured. Neoveil® , a nonwoven polyglycolic acid (PGA) felt, is already clinically used as an absorbable reinforcing material at pancreatic transection sites. Neoveil® was used for comparison, as was VIEWGEL® , which is marketed as a wound dressing. RESULTS: The hydrogel sheet remained in place 48 hours postoperatively. The ascitic amylase concentrations in the control, VIEWGEL® -treated, Neoveil® -treated, and hydrogel-treated rats, respectively, were 4992.4 ± 5355.7, 1068.4 ± 269.1, 730.2 ± 425.2, and 303.1 ± 240.1 IU/L; the ascitic lipase concentrations were 2279.8 ± 3395.2, 169.5 ± 100.6, 90.4 ± 71.0, and 86.8 ± 59.8 IU/L. The ascitic amylase and lipase levels were significantly lower in the hydrogel group than in the other groups (P < .05). CONCLUSIONS: This novel hydrogel sheet effectively prevents pancreatic fistulas and has promising clinical application potential.

Correction: Interleukin-1 Receptor Antagonist Has a Novel Function in the Regulation of Matrix Metalloproteinase-13 Expression.

[This corrects the article DOI: 10.1371/journal.pone.0140942.].

Acai Extract Transiently Upregulates Erythropoietin by Inducing a Renal Hypoxic Condition in Mice.

Acai (Euterpe oleracea Mart. Palmae, Arecaceae) is a palm plant native to the Brazilian Amazon. It contains many nutrients, such as polyphenols, iron, vitamin E, and unsaturated fatty acids, so in recent years, many of the antioxidant and anti-inflammatory effects of acai have been reported. However, the effects of acai on hematopoiesis have not been investigated yet. In the present study, we administered acai extract to mice and evaluated its hematopoietic effects. Acai treatment significantly increased the erythrocytes, hemoglobin, and hematocrit contents compared to controls for four days. Then, we examined the hematopoietic-related markers following a single injection. Acai administration significantly increased the levels of the hematopoietic-related hormone erythropoietin in blood compared to controls and also transiently upregulated the gene expression of Epo in the kidney. Furthermore, in the mice treated with acai extract, the kidneys were positively stained with the hypoxic probe pimonidazole in comparison to the controls. These results demonstrated that acai increases the erythropoietin expression via hypoxic action in the kidney. Acai can be expected to improve motility through hematopoiesis.

Isorhamnetin Alleviates Steatosis and Fibrosis in Mice with Nonalcoholic Steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is the most severe and progressive form of nonalcoholic fatty liver disease (NAFLD), which can lead to life-threatening conditions, however, there is still no approved drug for the treatment of NASH. In this study we used human-like NASH mouse model and treated orally with isorhamnetin at a dose of 50 mg/kg to analyze the effect of isorhamnetin on the progression of NASH. NASH-induced mice represented severe steatosis with inflammation, and fibrosis in liver accompanied with high level of liver injury markers in serum. Isorhamnetin treatment reduced intrahepatic lipid accumulation and TG content by inhibiting de novo lipogenic pathway in NASH-induced mice. Consistent with this, isorhamnetin-treated NASH mice showed improved liver injury markers, reduced collagen deposition as well as decreased gene expression of fibrogenic markers. Taken together, here we showed for the first time that synthesized isorhamnetin alleviates pathologic features of NASH and thus can potentially contribute to NASH drug development.

Syringaresinol Reverses Age-Related Skin Atrophy by Suppressing FoxO3a-Mediated Matrix Metalloproteinase-2 Activation in Copper/Zinc Superoxide Dismutase-Deficient Mice.

Aging is characterized by accumulation of chronic and irreversible oxidative damage, chronic inflammation, and organ dysfunction. Superoxide dismutase (SOD) serves as a major enzyme for cellular superoxide radical metabolism and physiologically regulates cellular redox balance throughout the body. Copper/zinc superoxide dismutase-deficient (SOD1-/-) mice showed diverse phenotypes associated with enhanced oxidative damage in whole organs. Here, we found that oral treatment with syringaresinol (also known as lirioresinol B), which is the active component in the berries of Korean ginseng (Panax ginseng C.A. Meyer), attenuated the age-related changes in Sod1-/- skin. Interestingly, syringaresinol morphologically normalized skin atrophy in Sod1-/- mice and promoted fibroblast outgrowth from Sod1-/- skin in vitro. These protective effects were mediated by the suppression of matrix metalloproteinase-2 overproduction in Sod1-/- skin, but not by increased collagen expression. Syringaresinol also decreased the oxidative damage and the phosphorylation of FoxO3a protein, which was a transcriptional factor of matrix metalloproteinase-2, in Sod1-/- skin. These results strongly suggest that syringaresinol regulates the FoxO3-matrix metalloproteinase-2 axis in oxidative damaged skin and exhibits beneficial effects on age-related skin involution in Sod1-/- mice.

Heterosis extends the reproductive ability in aged female mice†.

Heterosis is the beneficial effect of genetical heterogeneity in animals and plants. Although heterosis induces changes in the cells and individual abilities, few reports have described the effect of heterosis on the female reproductive ability during aging. In this study, we investigated the reproductive capability of genetically heterogeneous (HET) mice established by the four-way crossing of C57BL/6N, BALB/c, C3H/He, and DBA/2. We found the HET females naturally and repeatedly produced offspring, even in old age (14-18 months of age). We also found that HET females showed a significantly enlarged body and organ sizes in both youth and old age. In histological analyses, the numbers of primordial follicles, primary follicles, secondary follicles, and corpora lutea were significantly increased in the old ovaries of HET females compared with those in inbred C57BL/6 mice of the same age. In vitro fertilization experiments revealed that aged HET oocytes showed identical rates of fertilization, early development, and birth compared to those of young and old C57BL/6 oocytes. We further found the significantly increased expression of sirtuin genes concomitant with the up-regulation of R-spondin2 in old HET ovaries. These results confirm the novel phenotype, characterized by fertility extension and follicular retention due to heterosis, in old HET females. The HET female will be a valuable model for clarifying the mechanism underlying the effect of heterosis in the field of reproduction.

Royal Jelly Delays Motor Functional Impairment During Aging in Genetically Heterogeneous Male Mice.

Aging is associated with motor disorders that decrease the quality of life (QOL). Royal jelly (RJ), used as a dietary supplement, has shown various health benefits and, therefore, it has the potential to improve the QOL during aging. We have previously developed protease enzyme-treated RJ to avoid the anaphylactic response induced by RJ supplementation. However, the effects of a lifelong treatment with RJ on normal aging have not been fully clarified. In this study, we investigated the effects of enzyme-untreated RJ (NRJ) and enzyme-treated RJ (ERJ) on the aging process focusing on motor functions, by using a genetically heterogeneous (HET) mouse model experimentally endowed with genetic diversity. We performed four different physical performance tests (grip strength, wire hang, horizontal bar, and rotarod). We showed that the age-related impairment of the motor functions was significantly delayed in RJ-treated mice. Both NRJ and ERJ were similarly effective against these types of aging-associated declines. Histological analyses revealed that the RJ treatment affected the muscle fiber size at an advanced age. We also demonstrated that age-related changes in muscle satellite cell markers and catabolic genes were affected in RJ-treated mice. These results suggest that non-protein components of RJ improved the motor function in aging mice. These findings indicate that RJ has the potential to change the QOL during aging by regulating the motor function.

Probiotic Lactobacillus paracasei A221 improves the functionality and bioavailability of kaempferol-glucoside in kale by its glucosidase activity.

The interplay between food components and gut microbiota has been considered an important factor affecting the functionality of health-promoting foods. In this study, the effects of the probiotic Lactobacillus paracasei A221 on the functionality and bioavailability of kaempferol-3-o-sophroside (KP3S), a kaempferol-glucoside contained in kale, were investigated in vitro and in vivo. Unlike the type strain NBRC15889, the A221 strain converted standard KP3S as well as the kaempferol-glucosides in kale extract into kaempferol (KP). Using an intestinal barrier model, treatment with A221 significantly improved the effects of kale extract on the barrier integrity in vitro. KP, but not KP3S, clearly induced similar effects, suggesting that KP contributes to the functional improvement of the kale extract by A221. Pharmacokinetics analyses revealed that the co-administration of A221 and KP3S significantly enhanced the amount of deconjugated KP in murine plasma samples at 3 h post-administration. Finally, the oral administration of KP to Sod1-deficinet mice, which is a good mouse model of age-related disease, clearly ameliorated various pathologies, including skin thinning, fatty liver and anemia. These findings suggest that Lactobacillus paracasei A221 is effective for enhancing the anti-aging properties of kaempferol-glucosides by modulating their functionality and bioavailability through the direct bioconversion.

Apple procyanidins promote mitochondrial biogenesis and proteoglycan biosynthesis in chondrocytes.

Apples are well known to have various benefits for the human body. Procyanidins are a class of polyphenols found in apples that have demonstrated effects on the circulatory system and skeletal organs. Osteoarthritis (OA) is a locomotive syndrome that is histologically characterized by cartilage degeneration associated with the impairment of proteoglycan homeostasis in chondrocytes. However, no useful therapy for cartilage degeneration has been developed to date. In the present study, we detected beneficial effects of apple polyphenols or their procyanidins on cartilage homeostasis. An in vitro assay revealed that apple polyphenols increased the activities of mitochondrial dehydrogenases associated with an increased copy number of mitochondrial DNA as well as the gene expression of peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), suggesting the promotion of PGC-1α-mediated mitochondrial biogenesis. Apple  procyanidins also enhanced proteoglycan biosynthesis with aggrecan upregulation in primary chondrocytes. Of note, oral treatment with apple procyanidins prevented articular cartilage degradation in OA model mice induced by mitochondrial dysfunction in chondrocytes. Our findings suggest that apple procyanidins are promising food components that inhibit OA progression by promoting mitochondrial biogenesis and proteoglycan homeostasis in chondrocytes.

Evaluation of safety for hepatectomy in a novel mouse model with nonalcoholic-steatohepatitis.

AIM: To investigate whether the liver resection volume in a newly developed nonalcoholic steatohepatitis (NASH) model influences surgical outcome. METHODS: For establishment of a NASH model, mice were fed a high-fat diet for 4 wk, administered CCl4 for the last 2 wk, and administered T0901317 for the last 5 d. We divided these mice into two groups: A 30% partial hepatectomy (PH) of NASH liver group and a 70% PH of NASH liver group. In addition, a 70% PH of normal liver group served as the control. Each group was evaluated for survival rate, regeneration, apoptosis, necrosis and DNA expression after PH. RESULTS: In the 70% PH of NASH group, the survival rate was significantly decreased compared with that in the control and 30% PH of NASH groups (P < 0.01). 10 of 32 mice in the NASH 70% PH group died within 48 h after PH. Serum aspartate aminotransferase (AST) levels and total bilirubin (T-Bil) in the NASH 70% PH group were significantly higher than the levels in the other two groups (AST: P < 0.05, T-Bil: P < 0.01). In both PH of NASH groups, signaling proteins involved in regeneration were expressed at lower levels than those in the control group (P < 0.01). The 70% PH of NASH group also exhibited a lower number of Ki-67-positive cells and higher rates of apoptosis and necrosis than the NASH 30% PH group (P < 0.01). In addition, DNA microarray assays showed differences in gene expression associated with cell cycle arrest and apoptosis. CONCLUSION: The function of the residual liver is impaired in fatty liver compared to normal liver. A larger residual volume is required to maintain liver functions in mice with NASH.

Antioxidant treatment with vitamin C attenuated rotator cuff degeneration caused by oxidative stress in Sod1-deficient mice.

BACKGROUND: Rotator cuff degeneration is 1 of several factors that lead to rotator cuff tears; however, the mechanism of this degeneration remains unclear. We previously reported that deficiency of an antioxidant enzyme, superoxide dismutase 1 (Sod1), in mice induced degeneration in supraspinatus tendon entheses, a model that replicates human rotator cuff degeneration. In this study, we analyzed possible effects of vitamin C (VC), a major antioxidant, on the degenerative changes of supraspinatus entheses in Sod1 -/- mice. METHODS: We administered VC or vehicle, distilled water, for 8 weeks to Sod1 -/- and wild-type male mice beginning at 12 weeks of age (n = 5-8 per group). When mice were 20 weeks of age, we sectioned rotator cuff tissue samples and performed hematoxylin-eosin and toluidine blue staining for quantitative histologic evaluation. RESULTS: VC administration, compared with vehicle administration, attenuated the histologic changes, including a misaligned 4-layered structure, fragmented tidemark, and toluidine blue staining, in the supraspinatus entheses of Sod1 -/- mice. In the quantitative histologic evaluation, all parameters were significantly decreased in Sod1 -/- mice compared with wild-type mice, except for the number of nonchondrocytes. CONCLUSION: We demonstrated that an antioxidant treatment, VC administration, attenuated the rotator cuff degeneration, similar to that observed in humans, that is caused by oxidative stress in Sod1 -/- mice. VC effects included improvements in quantitative histologic parameters and other histologic changes. These results suggest that VC treatment can prevent oxidative stress-induced degeneration of the rotator cuff.

Novel non-alcoholic steatohepatitis model with histopathological and insulin-resistant features.

Although several non-alcoholic steatohepatitis (NASH) models have been reported to date, few of these models fully reflect the histopathology and pathophysiology of human NASH. The aim of this study was to establish a novel NASH model by feeding a high-fat (HF) diet and administering both carbon tetrachloride (CCl4 ) and the Liver X receptor agonist T0901317. Male C57BL/6J mice were divided into four groups (each n = 5): HF, HF + CCl4 , HF + T0901317, and the novel NASH model (HF + CCl4 + T0901317). CCl4 (0.1 mL/kg) and T0901317 (2.5 mg/kg) were intraperitoneally administered four times and five times, respectively. The livers of the novel NASH model group presented a whitish colour. The serum levels of TNF-α and IL-6 were significantly increased in the novel NASH model group, and mice in this group exhibited histopathological features and insulin resistance reflective of NASH, i.e., macrovesicular hepatic steatosis, ballooning hepatocytes, Mallory-Denk bodies, lobular inflammation and fibrosis. The novel NASH model group presented significantly upregulated expression levels of mRNAs related to lipogenesis, oxidative stress, fibrosis and steatosis and significantly downregulated expression levels of mRNAs related to triglyceride export. We successfully established a novel experimental NASH model that exhibits similar histopathology and pathophysiology to human NASH.

A Novel Therapeutic Strategy for Pancreatic Cancer: Targeting Cell Surface Glycan Using rBC2LC-N Lectin-Drug Conjugate (LDC).

Various cancers, including pancreatic ductal adenocarcinoma (PDAC), remain intractable even with costly tumor-targeting antibody drugs. Because the outermost coatings of cancer cells are composed of cell-specific glycan layers (glycocalyx), lectins, proteins with glycan-binding potential, were evaluated for possible use as drug carriers in PDAC treatment. A human PDAC cell line with well-to-moderately differentiated properties (Capan-1) was subjected to lectin microarray analysis to identify specific lectin-glycan pairs. The selected lectin was fused with a bacterial exotoxin for the construction of a lectin-drug conjugate (LDC), and its safety and antitumor effects were evaluated. A specific affinity between a recombinant bacterial C-type lectin (rBC2LC-N) and Capan-1 was identified, and its positivity was confirmed in 69 human samples. In contrast to the belief that all lectins mediate harmful hemagglutination, rBC2LC-N did not cause hemagglutination with human erythrocytes and was safely administered to mice. The 50% inhibitory concentration of LDC to Capan-1 (1.04 pg/mL = 0.0195 pmol/L) was 1/1,000 lower than that reported for conventional immunotoxins. The intraperitoneal administration of LDC reduced the tumor weight from 390 to 130.8 mg (P < 0.01) in an orthotopic model and reduced the number of nodules from 48 to 3 (P < 0.001) and improved survival from 62 to 105 days in a peritoneal dissemination model (P < 0.0001). In addition, the effect of LDC was reproduced in nodules from patient-derived PDAC xenografts through intravenous injection. Herein, we show the concept of utilizing lectins as drug carriers to target glycans on the cancer cell surface, highlighting new insights into cancer treatments. Mol Cancer Ther; 17(1); 183-95. ©2017 AACR.

Interleukin-1 Receptor Antagonist Has a Novel Function in the Regulation of Matrix Metalloproteinase-13 Expression.

Interleukin-1 receptor antagonist (IL-1Ra) is an IL-1 family member, which binds to IL-1 receptors but does not induce any intracellular signaling. We addressed whether IL-1Ra has a novel function in regulation of the extracellular matrix or adhesion molecules. Polymerase chain reaction array analysis demonstrated a ~5-fold increase in matrix metalloproteinase 13 (MMP-13) mRNA expression of IL-1Ra siRNA-transfected Ca9-22 human oral squamous epithelial carcinoma cells compared with the control. In fact, MMP-13 mRNA and protein expression as well as its activity in IL-1Ra siRNA-transfected Ca9-22 cell lines were significantly higher than those in the control. IL-1Ra siRNA treatment resulted in strong elevation of MMP-13 expression, whereas addition of rhIL-1Ra (40 ng/ml) suppressed MMP-13 expression, suggesting that IL-1Ra had a specific effect on MMP-13 induction. IL-1Ra siRNA could potently suppress IL-1α. No significant difference was found between the MMP-13 mRNA expression of IL-1Ra siRNA-transfected cells and those treated with anti-IL-1α or anti-IL-1ß antibodies. These results suggested that continuous supply of IL-1 had no effect on the induction of MMP-13 by IL-1Ra siRNA. Histopathological investigation of MMP-13 in periodontal tissue showed specific localization in the junctional epithelial cells of IL-1Ra knockout (KO) mice. Furthermore, infection with Aggregatibacter actinomycetemcomitans to establish an experimental periodontitis model resulted in predominant localization of MMP-13 along apical junctional epithelial cells. Laminin-5, which is degraded by MMP-13, was found in the internal basal lamina of wild-type mice, whereas the internal basal lamina of IL-1Ra KO mice did not show obvious laminin-5 localization. In particular, laminin-5 localization almost disappeared in the internal basal lamina of IL-1Ra KO mice infected with A. actinomycetemcomitans, suggesting that the suppression of IL-1Ra resulted in strong induction of MMP-13 that degraded laminin-5. In conclusion, IL-1Ra is associated with MMP-13 expression and has a novel function in such regulation without interference of the IL-1 signaling cascade.