How Islet Size Shapes Cell Composition: What Scientists Found in Healthy Pancreases

One promising approach to treating Type 1 diabetes involves growing replacement islets from stem cells in the laboratory. These engineered islets could eventually be transplanted to restore the body's ability to produce insulin. To make these artificial islets work as well as possible, scientists need to understand how real, healthy islets are organized and what makes them function properly.

A major challenge in islet engineering is that researchers often take freshly grown islets and break them apart, then reassemble them into uniform, standardized sizes. While this standardization seems practical, scientists don't yet know whether uniform islets actually match how nature organizes these structures. To answer that question, researchers needed to carefully study how islets are built in healthy human pancreases.

A team examined whole pancreases from 10 healthy, non-diabetic men to map the relationship between islet size and cell composition. They identified three main hormone-producing cell types: beta cells (insulin), alpha cells (glucagon), and delta cells (somatostatin). They also studied scattered individual hormone cells and tiny clusters that exist outside formal islets.

The key finding: islet size strongly influences the mix of cell types. Larger islets tend to have more alpha cells and fewer beta cells, while smaller islets show different proportions. Interestingly, delta cells remained at consistent levels regardless of islet size.

The researchers also discovered that about 80% of all endocrine tissue—the hormone-producing area of the pancreas—is contained within islets that have all three hormone types present together. This suggests that multi-hormone islets are the dominant structure in healthy pancreases.

Beyond cell composition, the study revealed that islets are strategically positioned within the pancreas. Islets aren't scattered randomly throughout the tissue. Instead, they cluster together in distinct patterns, and different types of islets prefer different locations.

Islets containing all three hormone types tend to be found near the core of the pancreas, while islets containing only delta cells (somatostatin-producing cells) are often pushed toward the edges. This spatial organization held true across all three regions of the pancreas: head, body, and tail.

These findings establish a 'physiological blueprint'—a detailed map of how healthy islets should look and function. This blueprint is essential for scientists designing stem cell-derived islets for transplantation. Rather than assuming that uniform, standardized islets will work best, researchers now know that natural islets vary in size and composition in specific, predictable ways.

The next step will be testing whether engineered islets that more closely mimic this natural variation perform better than uniform versions. If they do, it could lead to more effective islet transplants for people with Type 1 diabetes. The research is still in early stages, but understanding the rules that nature follows is a necessary foundation for engineering tissue that works as well as the body's own.

Source: bioRxiv : the preprint server for biology. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.