Single-cell resolution analysis of the human pancreatic ductal progenitor cell niche.

We have described multipotent progenitor-like cells within the major pancreatic ducts (MPDs) of the human pancreas. They express PDX1, its surrogate surface marker P2RY1, and the bone morphogenetic protein (BMP) receptor 1A (BMPR1A)/activin-like kinase 3 (ALK3), but not carbonic anhydrase II (CAII). Here we report the single-cell RNA sequencing (scRNA-seq) of ALK3bright+-sorted ductal cells, a fraction that harbors BMP-responsive progenitor-like cells. Our analysis unveiled the existence of multiple subpopulations along two major axes, one that encompasses a gradient of ductal cell differentiation stages, and another featuring cells with transitional phenotypes toward acinar tissue. A third potential ducto-endocrine axis is revealed upon integration of the ALK3bright+ dataset with a single-cell whole-pancreas transcriptome. When transplanted into immunodeficient mice, P2RY1+/ALK3bright+ populations (enriched in PDX1+/ALK3+/CAII- cells) differentiate into all pancreatic lineages, including functional ß-cells. This process is accelerated when hosts are treated systemically with an ALK3 agonist. We found PDX1+/ALK3+/CAII- progenitor-like cells in the MPDs of types 1 and 2 diabetes donors, regardless of the duration of the disease. Our findings open the door to the pharmacological activation of progenitor cells in situ.

The Role of MicroRNAs in Diabetes-Related Oxidative Stress.

Cellular stress, combined with dysfunctional, inadequate mitochondrial phosphorylation, produces an excessive amount of reactive oxygen species (ROS) and an increased level of ROS in cells, which leads to oxidation and subsequent cellular damage. Because of its cell damaging action, an association between anomalous ROS production and disease such as Type 1 (T1D) and Type 2 (T2D) diabetes, as well as their complications, has been well established. However, there is a lack of understanding about genome-driven responses to ROS-mediated cellular stress. Over the last decade, multiple studies have suggested a link between oxidative stress and microRNAs (miRNAs). The miRNAs are small non-coding RNAs that mostly suppress expression of the target gene by interaction with its 3'untranslated region (3'UTR). In this paper, we review the recent progress in the field, focusing on the association between miRNAs and oxidative stress during the progression of diabetes.

Temporal single-cell regeneration studies: the greatest thing since sliced pancreas?

The application of single-cell analytic techniques to the study of stem/progenitor cell niches supports the emerging view that pancreatic cell lineages are in a state of flux between differentiation stages. For all their value, however, such analyses merely offer a snapshot of the cellular palette of the tissue at any given time point. Conclusions about potential developmental/regeneration paths are solely based on bioinformatics inferences. In this context, the advent of new techniques for the long-term culture and lineage tracing of human pancreatic slices offers a virtual window into the native organ and presents the field with a unique opportunity to serially resolve pancreatic regeneration dynamics at the single-cell level.

Long-term culture of human pancreatic slices as a model to study real-time islet regeneration.

The culture of live pancreatic tissue slices is a powerful tool for the interrogation of physiology and pathology in an in vitro setting that retains near-intact cytoarchitecture. However, current culture conditions for human pancreatic slices (HPSs) have only been tested for short-term applications, which are not permissive for the long-term, longitudinal study of pancreatic endocrine regeneration. Using a culture system designed to mimic the physiological oxygenation of the pancreas, we demonstrate high viability and preserved endocrine and exocrine function in HPS for at least 10 days after sectioning. This extended lifespan allowed us to dynamically lineage trace and quantify the formation of insulin-producing cells in HPS from both non-diabetic and type 2 diabetic donors. This technology is expected to be of great impact for the conduct of real-time regeneration/developmental studies in the human pancreas.

Publisher Correction: Long-term culture of human pancreatic slices as a model to study real-time islet regeneration.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Pancreatic Progenitors: There and Back Again.

Adult pancreatic regeneration is one of the most contentious topics in modern biology. The long-held view that the islets of Langerhans can be replenished throughout adult life through the reactivation of ductal progenitor cells has been replaced over the past decade by the now prevailing notion that regeneration does not involve progenitors and occurs only through the duplication of pre-existing mature cells. Here we dissect the limitations of lineage tracing (LT) to draw categorical conclusions about pancreatic regeneration, especially in view of emerging evidence that traditional lineages are less homogeneous and cell fates more dynamic than previously thought. This new evidence further suggests that the two competing hypotheses about regeneration are not mutually exclusive.

P2RY1/ALK3-Expressing Cells within the Adult Human Exocrine Pancreas Are BMP-7 Expandable and Exhibit Progenitor-like Characteristics.

Treatment of human pancreatic non-endocrine tissue with Bone Morphogenetic Protein 7 (BMP-7) leads to the formation of glucose-responsive ß-like cells. Here, we show that BMP-7 acts on extrainsular cells expressing PDX1 and the BMP receptor activin-like kinase 3 (ALK3/BMPR1A). In vitro lineage tracing indicates that ALK3+ cell populations are multipotent. PDX1+/ALK3+ cells are absent from islets but prominently represented in the major pancreatic ducts and pancreatic duct glands. We identified the purinergic receptor P2Y1 (P2RY1) as a surrogate surface marker for PDX1. Sorted P2RY1+/ALK3bright+ cells form BMP-7-expandable colonies characterized by NKX6.1 and PDX1 expression. Unlike the negative fraction controls, these colonies can be differentiated into multiple pancreatic lineages upon BMP-7 withdrawal. RNA-seq further corroborates the progenitor-like nature of P2RY1+/ALK3bright+ cells and their multilineage differentiation potential. Our studies confirm the existence of progenitor cells in the adult human pancreas and suggest a specific anatomical location within the ductal and glandular networks.