Association of specific Streptococcus mutans strains
with development of non-alcoholic steatohepatitis
Keiko Tabata*, Shuhei Naka, Sodai Nakano, Michiyo Matsumoto-Nakano
Department of Pediatric Dentistry, Okayama University Graduate School of Medicine,
Dentistry and Pharmaceutical Sciences, Japan

Objective
Non-alcoholic steatohepatitis (NASH) is a fatty liver condition that leads to liver
inflammation. In our previous studies, collagen-binding protein (Cnm)- and 190-kDa
cell surface protein antigen (PA)-positive Streptococcus mutans strains were frequently
detected in NASH patients. Here, the involvement of these specific S. mutans strains indevelopment of NASH was assessed using a mouse model.
Methods
C57BL/6J mice (6-week-old males) were fed a high-fat diet for four weeks, then aCnm- and PA-positive (Cnm+/PA+) S. mutans KT3 strain isolated from a patient withsevere NASH, was intravenously injected via the jugular vein. After 12 weeks, the mice
were euthanized and blood samples collected, and whole body, extirpated liver tissue,and visceral fat weight measurements performed. Hematoxylin-eosin (HE) staining wasused to assess inflammatory cell infiltration and fat deposition in the liver, andMasson's-trichrome (MT) staining to evaluate fibrosis. In another experiment, KT3,KT4 (Cnm-/PA+), KT2 (Cnm+/PA-), and KT44 (Cnm-/PA-) strains were injected. After 1
or 3 hours, liver, visceral fat, and subcutaneous fat specimens were collected and placed
into Mitis-salivarius agar plates including bacitracin, and the number of bacterialcolonies was counted.
Results
Liver weight as well as serum levels of ALT, AST, TC, and LDL was significantly
increased after injection of the KT3 strain as compared to the control group without
infection (P<0.05). In liver tissues, HE staining revealed marked lipid accumulation
with lobular inflammation and MT staining showed marked fibrosis. All strains of S.
mutans were detected in all specimens from injected mice, though the number was
significantly higher in liver specimens obtained at 1 hour after infection of with the KT3strain.
Conclusion
These findings suggest that when Cnm- and PA-positive S. mutans organisms in thebloodstream reach a liver with fat accumulation, NASH aggravation is induced.
(291/300 words max)*Key words: non-alcoholic steatohepatitis, Streptococcus mutans, collagen-binding
protein, protein antigen*Keiko Tabata
Department of Pediatric Dentistry, Okayama University Graduate School of Medicine,Dentistry and Pharmaceutical Sciences, Okayama City, Japan,
Email: psb83inz@s.okayama-u.ac.jp

Collagen-binding Protein Pathogenicity in Rat Model of IgA Nephropathy
K. SUEHARA*1, D. MATSUOKA1, S. NAKA1, T. MISAKI2, Y. NAGASAWA3, S.
ITO4, R. NOMURA5, K. NAKANO6, M. MATSUMOTO-NAKANO1
1

Department of Pediatric Dentistry, Okayama University Graduate School of Medicine,Dentistry and Pharmaceutical Sciences, Japan
2Division of Nephrology, Seirei Hamamatsu Genaral Hospital, Japan3
Department of General Internal Medicine, Hyogo College of Medicine, Japan
4
Department of Internal Medicine, Japan Seif-Defense Iruma Hospital, Japan
5
Department of Pediatric Dentistry, Graduate School of Biomedical and Health Sciences,
Hiroshima University, Japan
6
Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry,Japan
Objectives: We previously reported that administration of collagen-binding protein(Cnm)-positive S. mutans in a rat model caused IgA nephropathy-like nephritis in thejugular vein. The present study investigated involvement of Cnm in development of
IgAN-like nephritis in a jugular vein model using a Cnm deletion mutant strain and its
complement strain, as well as recombinant Cnm (rCnm).
Methods: An S. mutans SN74 strain, that with Cnm deletion (CND), a complement
strain (Comp), and rCnm were used, with each administered through the jugular vein ofindividual Sprague-Dawley rats (4-week-old males). After 45 days, the rats wereeuthanized, then urine and blood samples collected, and kidneys extracted. Evaluationsof renal tissue pathology in the kidneys were performed using periodic acid-schiff (PAS)staining and fluorescent immunostaining with IgA, C3 antibodies.
Results: There were no significant differences in major serum measurements or urinary
protein levels among the groups. On the other hand, the hematuria positivity rate wassignificantly higher in the SN74 group as compared with the CND (P<0.05) and control(PBS) (P<0.01) groups. Histopathological analyses of sections stained with PAS
revealed prominent proliferation of mesangial cells and mesangial matrix in rats in theSN74, Comp, and rCnm groups. Mesangial proliferation scores were significantly higher
in the SN74 and Comp groups as compared to the PBS and CND groups, while thatscore for the rCnm protein group was significantly higher than that of the CND group.
Furthermore, immunohistochemical analyses using IgA- and C3-specific antibodies
showed prominent positive reactions in mesangial regions of rats inoculated with SN74,Comp, or rCnm protein.
Conclusions: These results led us to speculate that Cnm protein on the surface of S.
mutans, but not the bacterium itself, is an important virulence factor involved in S.
mutans-related IgAN.
【Key words】
1. Streptococcus mutans 2. Collagen-binding protein 3. IgA nephropathy
4. Recombinant Cnm