Regenerative Biology Section, Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
PLoS One. 2010 Jan 13;5(1):e8653. doi: 10.1371/journal.pone.0008653.
Insulin-producing pancreatic islet beta cells (beta-cells) are destroyed, severely depleted or functionally impaired in diabetes. Therefore, replacing functional beta-cell mass would advance clinical diabetes management. We have previously demonstrated the importance of Cdk4 in regulating beta-cell mass. Cdk4-deficient mice display beta-cell hypoplasia and develop diabetes, whereas beta-cell hyperplasia is observed in mice expressing an active Cdk4R24C kinase. While beta-cell replication appears to be the primary mechanism responsible for beta-cell mass increase, considerable evidence also supports a contribution from the pancreatic ductal epithelium in generation of new beta-cells. Further, while it is believed that majority of beta-cells are in a state of 'dormancy', it is unclear if and to what extent the quiescent cells can be coaxed to participate in the beta-cell regenerative response. Here, we address these queries using a model of partial pancreatectomy (PX) in Cdk4 mutant mice. To investigate the kinetics of the regeneration process precisely, we performed DNA analog-based lineage-tracing studies followed by mathematical modeling. Within a week after PX, we observed considerable proliferation of islet beta-cells and ductal epithelial cells. Interestingly, the mathematical model showed that recruitment of quiescent cells into the active cell cycle promotes beta-cell mass reconstitution in the Cdk4R24C pancreas. Moreover, within 24-48 hours post-PX, ductal epithelial cells expressing the transcription factor Pdx-1 dramatically increased. We also detected insulin-positive cells in the ductal epithelium along with a significant increase of islet-like cell clusters in the Cdk4R24C pancreas. We conclude that Cdk4 not only promotes beta-cell replication, but also facilitates the activation of beta-cell progenitors in the ductal epithelium. In addition, we show that Cdk4 controls beta-cell mass by recruiting quiescent cells to enter the cell cycle. Comparing the contribution of cell proliferation and islet-like clusters to the total increase in insulin-positive cells suggests a hitherto uncharacterized large non-proliferative contribution.
胰岛素产生的胰岛β细胞（β细胞）在糖尿病中被破坏、严重耗竭或功能受损。因此，替代功能性β细胞量将推进临床糖尿病管理。我们之前已经证明了 Cdk4 在调节β细胞量中的重要性。Cdk4 缺陷小鼠表现出β细胞发育不良并发展为糖尿病，而表达活性 Cdk4R24C 激酶的小鼠则观察到β细胞增生。虽然β细胞复制似乎是导致β细胞量增加的主要机制，但大量证据也支持胰腺导管上皮细胞在产生新的β细胞方面的贡献。此外，虽然人们认为大多数β细胞处于“休眠”状态，但不清楚静止细胞是否以及在何种程度上可以被诱导参与β细胞再生反应。在这里，我们使用 Cdk4 突变小鼠的部分胰腺切除术（PX）模型来解决这些问题。为了准确研究再生过程的动力学，我们进行了基于 DNA 类似物的谱系追踪研究，并进行了数学建模。在 PX 后一周内，我们观察到胰岛β细胞和导管上皮细胞的大量增殖。有趣的是，数学模型表明，静止细胞被招募到活跃的细胞周期中，促进了 Cdk4R24C 胰腺中β细胞量的重建。此外，在 PX 后 24-48 小时内，表达转录因子 Pdx-1 的导管上皮细胞显著增加。我们还在导管上皮细胞中检测到胰岛素阳性细胞，并且在 Cdk4R24C 胰腺中显著增加了胰岛样细胞簇。我们得出结论，Cdk4 不仅促进β细胞复制，而且还促进导管上皮中β细胞祖细胞的激活。此外，我们表明 Cdk4 通过招募静止细胞进入细胞周期来控制β细胞量。比较细胞增殖和胰岛样簇对胰岛素阳性细胞总增加的贡献表明存在迄今为止尚未表征的大量非增殖性贡献。
