Mitsiadis T A, Couble P, Dicou E, Rudkin B B, Magloire H
Laboratoire de Développement et Pathologie des Tissue Dentaires, CNRS-UPR 412, Faculté d'Oontologie de Lyon, France.
Differentiation. 1993 Oct;54(3):161-75. doi: 10.1111/j.1432-0436.1993.tb01599.x.
Nerve growth factor (NGF), a target-derived neurotrophic substance, may have broader biological functions in various types of non-neuronal differentiating cells. The effects of NGF are dependent on initial binding of NGF to specific cell-surface receptors (p75NGFR and p140prototrk) on responsive cells. The continuously growing rat incisor offers an excellent model demonstrating defined territories of differentiation of specific cell populations. We used immunohistochemistry to determine sites of NGF, proNGF and p75NGFR accumulation in the rat incisor, whereas NGF mRNA expression was visualized by in situ hybridization in the developing rat molar and incisor. Strictly similar patterns of NGF mRNA, proNGF and NGF expression were observed in differentiating cells responsible for the production of the main structural matrices of the tooth. Thus, proNGF-like and NGF-like immunoreactivity, as well as the NGF mRNA signal were observed in preameloblasts and young ameloblasts of the dental epithelium and in polarizing odontoblasts of the dental mesenchyme. In contrast, the distribution of p75NGFR was correlated with differentiation event only in dental mesenchyme: polarizing odontoblasts expressed p75NGFR whereas the molecule was absent in functional odontoblasts. In dental epithelium, the restricted expression of p75NGFR in ameloblast precursor cells was correlated with proliferative phenomena. The patterns of proNGF, NGF and p75NGFR expression in epithelium and mesenchyme implicate both an autocrine and paracrine mode of action of the NGF molecule in dental tissues. The findings reported here are important for understanding NGF action in specific dental cell populations and suggest that this molecule is involved in the cascade of events that directs tooth development.
神经生长因子（NGF）是一种靶源性神经营养物质，可能在各种类型的非神经元分化细胞中具有更广泛的生物学功能。NGF的作用取决于其与反应性细胞上特定细胞表面受体（p75NGFR和p140prototrk）的初始结合。持续生长的大鼠切牙提供了一个极好的模型，可展示特定细胞群体的明确分化区域。我们使用免疫组织化学来确定大鼠切牙中NGF、前体NGF和p75NGFR的积累部位，而通过原位杂交在发育中的大鼠磨牙和切牙中观察NGF mRNA的表达。在负责牙齿主要结构基质生成的分化细胞中，观察到NGF mRNA、前体NGF和NGF表达的模式极为相似。因此，在牙上皮的前成釉细胞和年轻成釉细胞以及牙间充质的极化成牙本质细胞中观察到了前体NGF样和NGF样免疫反应性以及NGF mRNA信号。相反，p75NGFR的分布仅在牙间充质中与分化事件相关：极化成牙本质细胞表达p75NGFR，而功能性成牙本质细胞中不存在该分子。在牙上皮中，p75NGFR在成釉细胞前体细胞中的限制性表达与增殖现象相关。上皮和间充质中前体NGF、NGF和p75NGFR的表达模式表明NGF分子在牙组织中具有自分泌和旁分泌作用模式。此处报道的研究结果对于理解NGF在特定牙细胞群体中的作用很重要，并表明该分子参与了指导牙齿发育的一系列事件。
