Effects of ageing on localizations of immunocompetent cells in periapical lesions in the rat mandibular molar

已有研究表明，根尖周病变主要由局部免疫防御反应和炎症反应引起。研究还表明，老年动物的免疫系统和组织修复受到损害：特别是T细胞依赖的细胞介导的免疫反应随着年龄的增长而降低。因此，年龄可能是影响根尖周病变进程的因素之一。我们的目的是比较年轻和老年大鼠磨牙实验性根尖周病变后免疫活性细胞的定位，并阐明增龄对根尖周病变过程的影响。为了引起根尖周损害，对下颌第一磨牙进行了牙髓切除术。然后，将他们自己的粪便溶解在无菌肉汤介质中，注入根管中。在牙髓治疗后4、7、14和28天，动物用…麻醉加用戊巴比妥钠，用4%对甲醛溶液灌流。每只动物游离解剖下颌骨，在相同的固定液中浸泡1天，然后在4℃的14%乙二胺四乙酸乙二胺溶液中脱钙2个月。下颌骨被石蜡包埋。以5μm厚连续切取近远端、纵切切片，用OX-6(抗II类分子)、ED1(也与树突状细胞反应的泛巨噬细胞抗体)和ED2(抗组织巨噬细胞)的单抗对切片进行免疫过氧化酶染色。与青年大鼠相比，老年大鼠的根尖周围炎症反应较轻，趋于慢性，修复有延迟的趋势。(1)ED1阳性细胞的定位：16月龄大鼠在4d和7d时，根尖周围及周围组织中可见大量ED1阳性的单核和多核细胞，14d和28d时，从根尖到根尖仍可见ED1阳性的多核细胞靠近骨面。在2月龄大鼠，28d时ED1阳性细胞似乎减少。(2)ED2和0x6阳性细胞的定位：16月龄大鼠牙周膜中ED2和0x6阳性细胞的分布和数量在4~14d基本相同，但在28d时有增加趋势。在2月龄大鼠中，这些阳性细胞的定位在7天和28天之间似乎没有差异。我们推测，老年大鼠的慢性炎症反应可能是由于巨噬细胞、淋巴细胞和浆细胞起主要作用的免疫机制随着年龄的增长而受损。较少

Periapical lesions have been shown to be induced mainly by local immune defense reactions against bacterial infection and inflammatory reactions. It has also been shown that the immune system and tissue repair are impaired in older animals : especially, T-cell dependent, cell mediated immunity reacts less efficiently with increasing age. Thus, ageing may be one of factors influencing the process of periapical lesions. Our aims here were to compare localizations of immunocompetent cells after experimental periapical lesions in molar teeth between young and old rats, and to elucidate the effects of ageing on the processes of periapical lesions.Eighteen old (16 month-old) and eighteen young (2 month-old) male Wistar rats were used. To induce periapical lesions, a pulpectomy was performed on the mandlbular first molar. Then, their own excrement dissolved in a sterile broth medium was infused into the root canal. At 4, 7, 14 and 28 days after pulp treatment, the animals were anaesthetized w … More ith pentobarbital and perfused with 4% parafolmaldehyde solution. In each animal, the mandibles were dissected free, immersed in the same fixative solution for a day, and then decalcified in 14% EDTA solution at 4℃ for 2 months. The mandibles were embedded in paraffin wax. Mesio-distal, longitudinal sections were cut serially at a thickness of 5 μm. Immunoperoxidase staining was done on sections by the use of monoclonal antibodies OX-6 (anti-class II molecules) , ED1 (a pan-macrophage antibody, reactive also with dendritic cells), and ED2 (anti-tissue macrophages).The present observation indicated that the processes of experimental periapical lesions were different between young and old rats. In the old rats, the inflammatory reactions around the periapical lesions appeared to be less severe, and to become chronic, and the repair tended to delay, as compared with the young rats. (1) localization of ED1-positive cells : In 16 month-old rats, there appeared to be many ED1-positive mononuclear and polynuclear cells in periapical lesions and surrounding tissues at 4 and 7 days ; at 14 and 28 days, ED1-positive polynuclear cells were still seen adjacent to bone surfaces from apical to apex. In 2 month-old rats, at 28 days ED1-positive cells appeared to decrease. (2) localizations of ED2 and 0X6-positive cells : In 16 month-old rats, distributions and numbers of ED2 and 0X6-positive cells appeared to be similar from 4 to 14 days, but the positive cells tended to increase at 28 days in the periodontal ligament at apical and mid-root levels. In 2 month-old rats, there appeared to be no differences in localizations of those positive cells between 7 and 28 days. We assume that the chronic inflammatory reactions in the old rats may be due to the impairment with ageing of the immune mechanisms where macrophages, lymphocytes, and plasma cells play main roles. Less