Department of Metabolism and Endocrinology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, Sagamihara, Japan.
Diabetologia. 2024 Jan;67(1):156-169. doi: 10.1007/s00125-023-06028-w. Epub 2023 Oct 23.
AIMS/HYPOTHESIS: Glucagon-expressing pancreatic alpha cells have attracted much attention for their plasticity to transdifferentiate into insulin-producing beta cells; however, it remains unclear precisely when, and from where, alpha cells emerge and what regulates alpha cell fate. We therefore explored the spatial and transcriptional heterogeneity of alpha cell differentiation using a novel time-resolved reporter system.
We established the mouse model, 'Gcg-Timer', in which newly generated alpha cells can be distinguished from more-differentiated cells by their fluorescence. Fluorescence imaging and transcriptome analysis were performed with Gcg-Timer mice during the embryonic and postnatal stages.
Fluorescence imaging and flow cytometry demonstrated that green fluorescence-dominant cells were present in Gcg-Timer mice at the embryonic and neonatal stages but not after 1 week of age, suggesting that alpha cell neogenesis occurs during embryogenesis and early neonatal stages under physiological conditions. Transcriptome analysis of Gcg-Timer embryos revealed that the mRNAs related to angiogenesis were enriched in newly generated alpha cells. Histological analysis revealed that some alpha cells arise close to the pancreatic ducts, whereas the others arise away from the ducts and adjacent to the blood vessels. Notably, when the glucagon signal was suppressed by genetic ablation or by chemicals, such as neutralising glucagon antibody, green-dominant cells emerged again in adult mice.
CONCLUSIONS/INTERPRETATION: Novel time-resolved analysis with Gcg-Timer reporter mice uncovered spatiotemporal features of alpha cell neogenesis that will enhance our understanding of cellular identity and plasticity within the islets.
Raw and processed RNA sequencing data for this study has been deposited in the Gene Expression Omnibus under accession number GSE229090.
目的/假设：表达胰高血糖素的胰腺α细胞因其向产生胰岛素的β细胞转分化的可塑性而备受关注；然而，α细胞的确切出现时间、来源以及调控α细胞命运的因素仍不清楚。因此，我们使用新型时间分辨报告系统探索了α细胞分化的空间和转录异质性。
我们建立了小鼠模型“Gcg-Timer”，其中新生成的α细胞可以通过其荧光与更分化的细胞区分开来。在胚胎和出生后阶段，使用 Gcg-Timer 小鼠进行荧光成像和转录组分析。
荧光成像和流式细胞术表明，在胚胎和新生小鼠中存在绿色荧光占主导的细胞，但在 1 周龄后不存在，这表明在生理条件下，α细胞新生发生在胚胎发生和新生儿早期阶段。Gcg-Timer 胚胎的转录组分析表明，与血管生成相关的 mRNAs 在新生成的α细胞中富集。组织学分析显示，一些α细胞起源于靠近胰腺导管的位置，而另一些起源于远离导管且靠近血管的位置。值得注意的是，当通过基因敲除或化学物质（如中和胰高血糖素的抗体）抑制胰高血糖素信号时，成年小鼠中再次出现绿色荧光占主导的细胞。
结论/解释：使用 Gcg-Timer 报告小鼠进行的新型时间分辨分析揭示了α细胞新生的时空特征，这将增强我们对胰岛内细胞身份和可塑性的理解。
本研究的原始和处理 RNA 测序数据已在基因表达综合数据库中以 GSE229090 号存档。
