Children's Health Research Institute, Western University, 800 Commissioners Road East, London, ON, Canada, N6C 2V5.
Diabetologia. 2014 Apr;57(4):754-64. doi: 10.1007/s00125-013-3147-y. Epub 2013 Dec 28.
AIMS/HYPOTHESIS: Aldehyde dehydrogenase 1 (ALDH1), a human stem-cell marker, is an enzyme responsible for converting retinaldehydes to retinoic acids (RAs) to modulate cell differentiation. However, data on expression levels and functional roles of ALDH1 during human fetal pancreatic development are limited. The focus of this study was to characterise ALDH1 expression patterns and to determine its functional role in islet cell differentiation.
The presence of ALDH1 in the human fetal pancreas (8-22 weeks) was characterised by microarray, quantitative RT-PCR, western blotting and immunohistological approaches. Isolated human fetal islet-epithelial cell clusters were treated with ALDH1 inhibitors, retinoic acid receptor (RAR) agonists and ALDH1A1 small interfering (si)RNA.
In the developing human pancreatic cells, high ALDH1 activity frequently co-localised with key stem-cell markers as well as endocrine transcription factors. A high level of ALDH1 was expressed in newly differentiated insulin(+) cells and this decreased as development progressed. Pharmacological inhibition of ALDH1 activity in human fetal islet-epithelial cell clusters resulted in reduced endocrine cell differentiation and increased cell apoptosis, and was reversed with co-treatment of RAR/RXR agonists. Furthermore, siRNA knockdown of ALDH1A1 significantly decreased RAR expression and induced cell apoptosis via suppression of the phosphoinositide 3-kinase (PI3K) pathway and activation of caspase signals.
CONCLUSIONS/INTERPRETATION: Our findings indicate that ALDH1(+) cells represent a pool of endocrine precursors in the developing human pancreas and that ALDH1 activity is required during endocrine cell differentiation. Inhibition of ALDH1-mediated retinoid signalling impairs human fetal islet cell differentiation and survival.
目的/假设：醛脱氢酶 1（ALDH1）是一种人类干细胞标志物，是一种将视黄醛转化为视黄酸（RAs）以调节细胞分化的酶。然而，关于 ALDH1 在人胎儿胰腺发育过程中的表达水平和功能作用的数据有限。本研究的重点是描述 ALDH1 的表达模式，并确定其在胰岛细胞分化中的功能作用。
通过微阵列、定量 RT-PCR、western blot 和免疫组织化学方法研究人胎儿胰腺（8-22 周）中 ALDH1 的存在。用 ALDH1 抑制剂、视黄酸受体（RAR）激动剂和 ALDH1A1 小干扰（si）RNA 处理分离的人胎儿胰岛上皮细胞簇。
在发育中的人胰腺细胞中，高 ALDH1 活性常与关键干细胞标志物以及内分泌转录因子共定位。高水平的 ALDH1 在新分化的胰岛素（+）细胞中表达，随着发育的进行而减少。在人胎儿胰岛上皮细胞簇中抑制 ALDH1 活性会导致内分泌细胞分化减少和细胞凋亡增加，并用 RAR/RXR 激动剂共同处理可逆转这种情况。此外，ALDH1A1 的 siRNA 敲低显著降低了 RAR 的表达，并通过抑制磷酸肌醇 3-激酶（PI3K）途径和激活半胱氨酸蛋白酶信号诱导细胞凋亡。
结论/解释：我们的研究结果表明，ALDH1（+）细胞代表人胰腺发育过程中的内分泌前体细胞池，ALDH1 活性是内分泌细胞分化所必需的。抑制 ALDH1 介导的视黄酸信号会损害人胎儿胰岛细胞的分化和存活。
