Academic Background

Diabetes is a global health issue affecting over 500 million people. Both type 1 diabetes (T1D) and type 2 diabetes (T2D) share the common feature of a significant reduction in the number of functional insulin-secreting beta cells. Therefore, restoring or increasing beta cell mass is considered a key strategy in diabetes treatment. Although progress has been made through methods such as pancreas transplantation, islet transplantation, or stem cell-derived beta cell transplantation, these approaches are costly, donor-dependent, and difficult to scale. Consequently, developing drugs that promote endogenous beta cell regeneration has become a research focus.

Recent studies have found that small-molecule drugs such as DYRK1A inhibitors (e.g., harmine) can promote beta cell proliferation and enhance their differentiation and function. However, the precise mechanisms by which these drugs promote beta cell regeneration in vivo remain unclear. This study used single-cell RNA sequencing (scRNA-seq) to investigate the effects of DYRK1A inhibitors on islet cells, particularly the potential for alpha-to-beta cell transdifferentiation.

Source of the Paper

This paper was co-authored by Esra Karakose, Xuedi Wang, Peng Wang, and others, affiliated with the Diabetes, Obesity, and Metabolism Institute at the Icahn School of Medicine at Mount Sinai in New York, among other institutions. The paper was published on December 17, 2024, in Cell Reports Medicine, titled “Cycling Alpha Cells in Regenerative Drug-Treated Human Pancreatic Islets May Serve as Key Beta Cell Progenitors.”

Research Process and Results

Research Process

1. Single-Cell RNA Sequencing: The research team obtained islet cells from four adult donors and treated them with 10 µM harmine alone, harmine combined with 5 nM GLP-1 receptor agonist (GLP-1(7-36)), or harmine combined with 3 µM TGF-β inhibitor (LY364947) for 96 hours. Subsequently, scRNA-seq was performed on these treated islet cells, yielding 109,881 high-quality single-cell datasets.

2. Cell Type Annotation and Clustering Analysis: Using scRNA-seq data, the team identified 21 unique cell type clusters and confirmed all known islet cell types. Data integration and batch correction were performed using the “Harmony” tool to ensure consistency across donors. Additionally, feature plots were generated to display the expression levels of islet cell hormones (e.g., insulin, glucagon, somatostatin).

3. Cell Cycle Analysis: The team defined the cell cycle stage for each cell type and identified two cell types with high levels of proliferation markers (e.g., MKI67, TOP2A), one of which was labeled as “cycling alpha cells.” These cells primarily expressed alpha cell marker genes (e.g., GCG, CHGB) as well as genes associated with insulin granules (e.g., SCG2).

4. Impact of Drug Treatment on Cell Abundance: The team compared the proportions of each cell type under different treatment conditions and found that regenerative drug treatment significantly increased the proportion of cycling alpha cells. Differential abundance testing using the Milo statistical framework further confirmed the significant increase in cycling alpha cells after drug treatment.

5. Cell Transdifferentiation Analysis: To explore whether cycling alpha cells could transdifferentiate into beta cells, the team performed RNA velocity and pseudotime trajectory analyses. The results showed that cycling alpha cells could differentiate into alpha-beta2-type cells, which could further transform into beta cells. Additionally, immunocytochemistry experiments confirmed a significant increase in C-peptide+/glucagon+ alpha-beta cells after regenerative drug treatment.

Key Results

1. Identification of Cycling Alpha Cells: Through scRNA-seq, the team identified a unique population of cycling alpha cells that significantly increased after regenerative drug treatment and exhibited upregulation of beta cell phenotypic markers.

2. Impact of Drug Treatment on Cell Abundance: Regenerative drug treatment significantly increased the proportion of cycling alpha cells, suggesting these cells as primary targets of the drugs.

3. Evidence of Cell Transdifferentiation: RNA velocity and pseudotime trajectory analyses indicated that cycling alpha cells could differentiate into alpha-beta2-type cells and further transform into beta cells. Immunocytochemistry experiments also confirmed a significant increase in alpha-beta cells after drug treatment.

4. Acquisition of Beta Cell Phenotype: Cycling alpha cells exhibited upregulation of beta cell phenotypic markers after regenerative drug treatment, suggesting that these cells may contribute to beta cell mass expansion through transdifferentiation.

Conclusions and Significance

This study reveals that DYRK1A inhibitors promote beta cell mass expansion by inducing the proliferation and transdifferentiation of cycling alpha cells. This finding provides new insights into diabetes treatment, particularly for patients with severely reduced beta cell mass. Additionally, the study suggests that the effects of regenerative drugs may not be limited to beta cells but may also involve targeting alpha cell precursors for beta cell regeneration.

Research Highlights

1. Identification of Cycling Alpha Cells: The study is the first to identify cycling alpha cells through scRNA-seq and confirm their significant increase after regenerative drug treatment.

2. Evidence of Cell Transdifferentiation: RNA velocity and pseudotime trajectory analyses provide direct evidence of cycling alpha cell transdifferentiation into beta cells.

3. New Mechanism of Regenerative Drugs: The study reveals a novel mechanism by which DYRK1A inhibitors promote beta cell regeneration through the proliferation and transdifferentiation of alpha cell precursors.

Other Valuable Information

1. Technological Innovation: The study employed advanced techniques such as scRNA-seq, RNA velocity, and pseudotime trajectory analysis, providing new tools and methods for islet cell research.

2. Future Research Directions: The team highlights the need to develop human alpha cell lineage tracing technologies to further validate the mechanism of alpha-to-beta cell transdifferentiation. Additionally, these findings need to be validated in vivo to assess their potential for clinical applications.

This study offers new perspectives for diabetes treatment by revealing the mechanism of regenerative drugs in promoting alpha-to-beta cell transdifferentiation, with significant scientific and clinical implications.