Gritli-Linde A, Ruch J V, Linde A
Department of Oral Biochemistry, Faculty of Odontology, Göteborg University, Sweden.
Int J Dev Biol. 1995 Apr;39(2):383-93.
Polyamines are known to play a central role in processes such as growth and development. Virtually nothing is known about their importance in tooth development, an attractive and frequently used experimental model for studies of developmental processes. A polyamine-depleted state was created in tooth cells in an organ culture system. First lower molar germs from 16-and 17.5-day old mouse fetuses were used. alpha-difluoromethylornithine (DFMO) and methylglyoxal bis-(guanylhydrazone) (MGBG) were used to deplete the cells from their polyamine content. Polyamine interconversion and catabolism were prevented by aminoguanidine sulfate (AG). In day-16 germs cultured in serum-containing medium, DFMO reduced the frequency of cycling cells as shown by [3H]thymidine incorporation, and induced a delay of odontoblast differentiation of about 24 h. Under the same conditions, MGBG induced an arrest of histo-morphogenesis, correlated to a significant decrease in the rate of cell proliferation. Addition of polyamines prevented DFMO- and MGBG-induced delay of tooth differentiation. Interestingly, MGBG did not delay the terminal differentiation of odontoblasts and ameloblasts in cultured day-17.5 molars; in these, cells at the tip of the cusps are only a few hours before their withdrawal from the cell cycle. In serum-deprived medium, dental cytodifferentiations did not occur. Addition of putrescine or spermidine to serum-free media, however, allowed for tooth morphogenesis and cytodifferentiation. Tooth explants in a serum-deprived medium reacted to DFMO in a cytocidal fashion, whereas MGBG showed only a mild toxicity in some cell types. Addition of putrescine to DFMO-containing medium prevented its cytotoxic effect. Addition of spermidine to MGBG-containing medium not only prevented its mild toxicity but also allowed for predentin secretion by differentiated odontoblasts. The results are discussed with regard to the well-established developmental events of tooth germs cultured in vitro and with respect to present knowledge of polyamine metabolism and their involvement in cellular processes.
多胺在生长和发育等过程中发挥着核心作用。然而，对于它们在牙齿发育中的重要性几乎一无所知，而牙齿发育是研究发育过程的一个有吸引力且常用的实验模型。在器官培养系统中，使牙齿细胞处于多胺缺乏状态。首先使用16和17.5日龄小鼠胎儿的下颌第一磨牙牙胚。α-二氟甲基鸟氨酸（DFMO）和甲基乙二醛双（脒腙）（MGBG）用于去除细胞内的多胺。硫酸氨基胍（AG）可防止多胺的相互转化和分解代谢。在含血清培养基中培养的16日龄牙胚中，DFMO降低了[3H]胸苷掺入所显示的细胞周期循环频率，并使成牙本质细胞分化延迟约24小时。在相同条件下，MGBG诱导组织形态发生停滞，这与细胞增殖速率的显著降低相关。添加多胺可防止DFMO和MGBG诱导的牙齿分化延迟。有趣的是，MGBG并未延迟培养的17.5日龄磨牙中成牙本质细胞和成釉细胞的终末分化；在这些磨牙中，牙尖顶端的细胞仅在退出细胞周期前几个小时。在无血清培养基中，牙齿细胞分化未发生。然而，向无血清培养基中添加腐胺或亚精胺可使牙齿形态发生和细胞分化。无血清培养基中的牙齿外植体对DFMO有细胞毒性反应，而MGBG在某些细胞类型中仅表现出轻微毒性。向含DFMO的培养基中添加腐胺可防止其细胞毒性作用。向含MGBG的培养基中添加亚精胺不仅可防止其轻微毒性，还可使分化的成牙本质细胞分泌前期牙本质。本文结合体外培养牙胚的既定发育事件以及关于多胺代谢及其参与细胞过程的现有知识对结果进行了讨论。
