Identification and functional analysis of a candidate stem cell population in the adult mouse pancreas

胰腺是致人衰弱和致命疾病的起源，包括糖尿病和胰腺癌。因此，了解维持器官功能的内稳态机制是很重要的，因为它们的脱轨可能是这些疾病的起源或显著促成这些疾病。鉴定常驻胰腺干细胞可以为这些疾病的起源提供新的见解，并提出新的治疗场所。然而，尽管器官在各种损伤或刺激下表现出可塑性，但真正的成人胰腺干细胞的存在尚未得到证实。我们推断，假定的成体干细胞可能保留胚胎祖标记基因的表达，特别是由于成体干细胞的特定代谢需求而可能参与代谢调节的基因。因此，我们发现一种新的醛脱氢酶（Aldh）基因，编码线粒体酶Aldh1b1，在发育过程中在所有胰腺祖细胞中表达，并且在罕见的成年胰腺中央腺泡细胞中保留其表达。实验诱导胰腺再生导致Aldh1b1+细胞数量大量增加。我们使用小鼠Aldh1b1谱系追踪系的初步结果显示，在稳态状态下，成年Aldh1b1+细胞产生内分泌、腺泡和导管细胞，作为真正的成年胰腺干细胞；以前从未见过的东西。这些细胞可以在体外自我更新和扩增数代，并保留祖细胞的特征。此外，我们已经在人类成人胰腺中分离出类似的群体，也可以在培养中扩大，保持祖细胞的特征。在本应用中，我们拟记录小鼠群体的自我更新和寿命，其在胰腺稳态和损伤后的贡献，并探讨Aldh1b1表达在小鼠成体胰腺干细胞自我更新和分化中的功能意义。为了进一步了解这个群体自我更新和分化的分子需求，并确定额外的特定标记，我们将进行单细胞RNA序列分析。这些发现将有助于在体外扩增过程中更好地维持这些细胞的干细胞特性，移植实验将用于评估它们在体外扩增后的发育潜力。这些研究旨在对小鼠中新发现的候选成人胰腺干细胞进行全面分析，并将为鉴定其人类同类细胞铺平道路。这些发现将有助于了解胰腺功能障碍和疾病的起源，并确定治疗糖尿病和胰腺癌的可能替代方法。

The pancreas is the origin of debilitating and fatal diseases, including diabetes and pancreatic cancer. Thus it is important to understand the homeostatic mechanisms that maintain organ function because their derailment might be at the origin of or significantly contribute to these diseases. Identification of resident pancreatic stem cells could provide fresh insights in the origin of these diseases and suggest new therapeutic venues. However, despite the demonstrated plasticity of the organ under various insults or stimuli, the presence of bona fide adult pancreas stem cells has not been documented.We reasoned that putative adult stem cells may retain expression of embryonic progenitor marker genes, particularly genes that may be involved in metabolic regulation due to the specific metabolic requirements of adult stem cells. Accordingly, we have found that a novel aldehyde dehydrogenase (Aldh) gene, encoding the mitochondrial enzyme Aldh1b1, is expressed in all pancreas progenitors during development and that its expression is retained in the rare centroacinar cells of the adult pancreas. Experimental induction of pancreas regeneration resulted in a large expansion of the number of Aldh1b1+ cells. Preliminary results using a mouse Aldh1b1 lineage tracing line that we generated, showed that adult Aldh1b1+ cells give rise to endocrine, acinar and duct cells acting as bona fide adult pancreas stem cells during homeostasis; something never seen before. These cells can self-renew and expand in vitro for several passages retaining progenitor character. Furthermore, we have isolated a similar population in the human adult pancreas that can also be expanded in culture retaining progenitor character. In this application we propose to document the self-renewal and longevity of the mouse population, its contribution during pancreas homeostasis and after injury and to address the functional significance of Aldh1b1 expression in self-renewal and differentiation of the adult pancreas stem cells in the mouse. To further understand the molecular requirements for self-renewal and differentiation of this population and identify additional specific markers we will perform single cell RNA Seq analysis. Findings will help to better maintain the stem cell character of these cells during in vitro expansion and transplantation experiments will be used to assess their developmental potential following in vitro expansion. These studies aim at a comprehensive analysis of the newly identified candidate adult pancreas stem cells in the mouse and will pave the way for the identification of their human counterparts. The findings will help understand the origins of pancreatic dysfunction and disease and identify possible alternative means to address diabetes and pancreatic cancer.