Nakamura Korefumi, Minami Kohtaro, Tamura Kanako, Iemoto Keisuke, Miki Takashi, Seino Susumu
Division of Cellular and Molecular Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan.
Biomed Res. 2011 Apr;32(2):167-74. doi: 10.2220/biomedres.32.167.
The mass of pancreatic β-cells is maintained throughout lifetime to control blood glucose levels. Although the major mechanism of the maintenance of β-cell mass after birth is thought to be selfreplication of pre-existing β-cells, it is possible that pancreatic β-cells are also generated from non-β-cells. Here, we address this issue by using the inducible Cre/loxP system to trace β-cells. We generated Ins2-CreERT2/R26R-YFP double knock-in mice, in which pancreatic β-cells can be labeled specifically and permanently upon injection of the synthetic estrogen analog tamoxifien, and then traced the β-cells by pulse and chase experiment in several different conditions. When β-cells were labeled in adults under physiological and untreated conditions, the frequency of the labeling (labeling index) was not altered significantly throughout the 12-month experimental period. In addition, the labeling index was not changed after ablation of β-cells by streptozotocin treatment. However, when tamoxifen was injected to pregnant mothers just before they gave birth, the labeling index in the neonates was decreased significantly around weaning, suggesting that β-cells are generated from non-β-cells. These results indicate that various mechanisms are involved in the maintenance of β-cells after birth, and that the present system using knock-in mice is useful for investigation of β-cell fate.
胰腺β细胞的数量在整个生命周期中得以维持，以控制血糖水平。尽管出生后β细胞数量维持的主要机制被认为是已存在的β细胞进行自我复制，但胰腺β细胞也有可能由非β细胞产生。在此，我们通过使用诱导型Cre/loxP系统追踪β细胞来解决这一问题。我们构建了Ins2-CreERT2/R26R-YFP双敲入小鼠，在注射合成雌激素类似物他莫昔芬后，胰腺β细胞能够被特异性且永久性地标记，然后在几种不同条件下通过脉冲追踪实验对β细胞进行追踪。当在生理和未处理条件下对成年小鼠的β细胞进行标记时，在整个12个月的实验期内，标记频率（标记指数）并未显著改变。此外，用链脲佐菌素处理使β细胞消融后，标记指数也没有变化。然而，当在即将分娩前给怀孕的母鼠注射他莫昔芬时，新生小鼠在断奶前后的标记指数显著降低，这表明β细胞是由非β细胞产生的。这些结果表明，出生后β细胞数量的维持涉及多种机制，并且目前使用敲入小鼠的系统对于研究β细胞命运很有用。
