根面齲蝕の進行におけるヒト好中球の酵素の役割に関するin vitro研究

In vitro Study of the Role of Human Neutrophil Enzymes on Root Caries Progression.

抄録

う蝕の進行における宿主免疫系の役割は主に推測されており、象牙質有機マトリックスの酵素分解を伴うと考えられている。本研究の目的は、根面齲蝕の進行に対するヒト好中球の酵素のタンパク質分解効果を評価することである。ウシ根部象牙質の標本を，う蝕（C），う蝕＋好中球（C＋N），う蝕なし（Control），う蝕なし＋好中球（Control＋N）の4群（n＝30）に分けた。Streptococcus mutansバイオフィルム（105 CFU/mL）を根面上で培養し、人工的に根面齲蝕病変を誘発した（C群およびC＋N群）。その後、標本に好中球（5×106個/mL）を48時間作用させた（C＋N群およびControl＋N群）。う蝕の発生と好中球の暴露は2回目と3回目に繰り返した。う蝕の深さ（CD）と象牙質の脱灰（DD）は，蛍光顕微鏡を用いてローダミンBの浸潤によって評価した。コラーゲン線維の超微細構造は，偏光顕微鏡下でピクロシリウスレッド染色を用いて評価した。C群とC＋N群の間では，1回，2回，3回の齲蝕好中球暴露でCDとDDに有意な差（p＞0.05）はなかった。未熟なコラーゲンは、最も表層の200μmにおいて、う蝕群（C, p = 0.003; C + N, p = 0.01）では非う蝕群に比べて有意に少なかった。以上のことから，ヒト好中球の酵素は短期間の根面齲蝕の進行には影響を与えず，S. mutansによる根面齲蝕の進行中には未熟なコラーゲン線維が分解されやすいと結論づけた．

The role of the host immune system in caries progression is mainly speculative, and it is believed that it entails the enzymatic degradation of the dentin organic matrix. The aim of this study was to evaluate the proteolytic effect of human neutrophil enzymes on root caries progression. For this, specimens of bovine root dentin were divided into 4 groups (n = 30): caries (C), caries + neutrophils (C + N), no caries (Control), and no caries + neutrophils (Control + N). Streptococcus mutans biofilm (105 CFU/mL) was grown on the root surface to artificially induce root carious lesions (C and C + N groups). Specimens were then exposed to neutrophils (5 × 106 cells/mL) for 48 h (C + N and Control + N groups). Caries development and neutrophil exposures were repeated a 2nd and 3rd time. Caries depth (CD) and dentin demineralization (DD) were assessed by infiltration of rhodamine B using fluorescence microscopy. Collagen fibril ultrastructure was characterized under a polarized microscope with Picrosirius red staining. There were no significant differences (p > 0.05) in CD and DD between the C and C + N groups for 1, 2, and 3 caries-neutrophil exposures. Immature collagen was significantly less present in the carious groups (C, p = 0.003; C + N, p = 0.01) than in the noncarious groups in the most superficial 200 µm. We thus concluded that human neutrophil enzymes did not influence short-term root caries progression, and immature collagen fibrils were more susceptible to degradation during S. mutans-induced root caries progression.