Effects of chronic Porphyromonas gingivalis lipopolysaccharide infusion on skeletal muscles in mice

Abstract

Periodontitis, which is caused by various oral organisms, predominantly affects adults, and is one of the main causes of tooth loss, as well as leading to progression of numerous systemic diseases. However, its relationship to sarcopenia (agingassociated degenerative loss of skeletal muscle mass and function) remains unclear. The aim of this study was to investigate the effects of Porphyromonas gingivalis lipopolysaccharide (PG-LPS) on skeletal muscle in mice, and to establish the underlying mechanisms. Mice (C57BL/6) were injected with PG-LPS (0.8 mg/kg/day) for 4 weeks. This treatment significantly decreased the weight of fast-twitch skeletal muscles (masseter and tibialis anterior muscles), but not that of slow-twitch skeletal muscle (soleus muscle). The area of fibrosis was significantly increased in masseter muscle, but remained unchanged in the other two muscles. The number of apoptotic myocytes was significantly increased (approximately eightfold) in masseter muscle. These data suggest that persistent subclinical exposure to PG-LPS might reduce the size of fast-twitch skeletal muscle, but not slow-twitch skeletal muscle. Masseter muscle appears to be especially susceptible to the adverse effects of PG-LPS, because muscle remodeling (muscle fibrosis and myocyte apoptosis) was induced solely in masseter muscle. Thus, periodontitis might be one of the major causes of oral sarcopenia.

Effects of occlusal disharmony on cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage in mice

“…Cross sections (10 μm) (Control: n = 6; BO: n = 6; Pro: n = 6; BO + Pro: n = 6) were cut with a cryostat (CM1900, Leica Microsystems, Nussloch, Germany) at -20°C. The sections were air-dried and fixed with 4% paraformaldehyde (v/v) in 0.1M phosphate-buffered saline (pH 7.5) [ 22 , 26 , 27 ].…”

“…Interstitial fibrosis was evaluated by Masson-trichrome staining using the Accustatin Trichrome Stain Kit (#HT15-1KT; Sigma) in accordance with the manufacturer's protocol [26,27]. Interstitial fibrotic regions were quantified using image software analysis (Image J 1.45) of the percentage of blue area in the Masson-trichrome sections [21,26,27].…”

“…Apoptosis was determined by terminal deoxyribonucleotidyl transferase (TdT)-mediated biotin-16-deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining using the Apoptosis in situ Detection Kit (#293-71501; Wako, Osaka, Japan). TUNEL-positive nuclei per field of view were manually counted in six sections from the four groups (Control; n = 6, BO; n = 6, Pro; n = 6, BO + Pro; n = 6) over a microscopic field of 20 x, averaged and expressed as the ratio of TUNEL-positive nuclei (%) [21,[26][27][28]. Limiting the counting of total nuclei and TUNEL-positive nuclei to areas with a true cross section of myocytes made it possible to selectively count only those nuclei that were clearly located within myocytes.…”

Effects of occlusal disharmony on susceptibility to atrial fibrillation in mice

“…Interstitial fibrosis was evaluated by Masson-trichrome staining using the Accustain Trichrome Stain Kit (#HT15-1KT; Sigma-Aldrich) in accordance with the manufacturer's protocol as described previously 22 . Interstitial fibrotic regions were quantified using Image J 1.48v software (National Institute of Health, Bethesda, MD, USA) to determine the percentage of blue-stained area in the Masson-trichrome sections 22,43,64 . DNA fragmentation was determined by TUNEL staining using an Apoptosis in situ Detection Kit (#293-71501; Wako, Osaka, Japan).…”

“…DNA fragmentation was determined by TUNEL staining using an Apoptosis in situ Detection Kit (#293-71501; Wako, Osaka, Japan). The total number of TUNEL-positive nuclei was counted manually in six sections of three groups (Control (n = 4), BO (n = 5), and Pro + BP (n = 4)) over a microscopic field of 20 x, averaged, and expressed as the ratio of TUNEL-positive nuclei (%) 20,22,43,64 .…”