Effect of beta-carotene on epithelio-mesenchymal interaction during ocbntogenesis and oncogenesis in NMU-treated hamster

我们已经报道了NMU处理的金黄地鼠门牙的牙齿发育障碍和牙源性肿瘤的诱导，并证明了维生素A在肿瘤发生和牙齿发育障碍中的作用。在本研究中，我们研究了天然和合成的β-胡萝卜素对NMU处理的仓鼠的影响。在服用β-胡萝卜素6小时后，每周进行两次NMU治疗，为期三个月。NMU诱导的下颌切牙牙本质发育障碍主要表现为牙釉质发育不全、釉质缺失、牙本质形成不规则等。在NMU处理的仓鼠中，过量的β-胡萝卜素略微抑制了牙齿发育、牙源性上皮的非典型增殖和上皮成分的角质化的干扰。在NMU抑制成釉细胞分化的情况下，未阻止成牙本质细胞的分化以及前成釉细胞与成牙本质细胞之间的细胞接触。β-胡萝卜素不能阻止NMU对成釉细胞分化的抑制，但能抑制NMU诱导的牙源性上皮角化。β-胡萝卜素对牙源性肿瘤的发生有一定的抑制作用。合成的β-胡萝卜素似乎比天然的β-胡萝卜素对NMU诱导的牙齿发育障碍略有效果。β-胡萝卜素可能作为一种生物学功能和维生素A原功能在牙源性上皮组织的正常分化中发挥作用。这项研究可能表明，β-胡萝卜素对牙源性肿瘤发展的抑制作用是一种生物学功能，而不是维生素A原功能。

We have reported the induction of disturbances in odontogenesis and odontogenic tumors in incisors of NMU-treated hamsters, and also demonstrated the effects of vitamin A on tumorigenesis and disturbances in odontogenesis. In the present study, we investigated the effect of natural and synthetic beta-carotene on NMU-treated hamsters. Six hours after administration of beta-carotenes, NMU treatment was conducted twice a week for three months. The NMU-induced disturbances in the odontogenesis of mandibular incisors were characterized by hypoplastic changes ranging from enamel hypoplasia to loss of enamel and irregular hypoplastic dentin formation. In NMU-treated hamsters, excess administration of beta-carotene slightly repressed disturbances in odontogenesis, atypical proliferation of odontogenic epithelium, and keratinization of epithelial components. In NMU inhibited ameloblast differentiation, the differentiation on odontoblasts and cell to cell contact between preameloblasts and odontoblasts were not prevented. The beta-carotene did not prevent NMU-induced inhibition of ameloblast differentiation but inhibited NMU-induced keratinization of odontogenic epithelium. The beta-carotene had a moderate suppressive effect on the development of the odontogenic tumors. Synthetic beta-carotene seems to be slightly more effective on NMU-induced disturbances in odontogenesis than natural beta-carotene. The beta-carotene may play a role in the normal differentiation of odontogenic epithelial tissue as a biological function and as a provitamin A function. This study may suggest inhibitory effects of beta-carotene on odontogenic tumor development as a biological function rather than as a provitamin A function.