When trying to reproduce pancreatic development from stem cells, investigators often focus on an individual aspect of the process -- identifying and characterizing either:
- The signals that drive the step-by-step progression to islets, or
- The genes activated by those signals
This "molecular environment” is obviously critical for success. But there are other factors that, thus far, have gone largely ignored.
Perhaps the most significant of these is the "physical environment.”
Oxygen a key
Islets are one of the most oxygenated compartments of the body. While they make up only one to two per cent of the total pancreas, they require 20 to 25 per cent of the total blood flow to the organ.
A network of vessels, which provides the oxygen, is quickly lost during the isolation process, and is one of the most likely culprits responsible for islet loss.
Novel research conducted by the DRI’s Tissue Engineering and Stem Cell Development teams has shed new light on how important the physical environment is for proper pancreatic beta cell development.
Using the embryonic mouse pancreas as a model, DRI researchers were able to enhance beta cell development by supplying the tissue with oxygen in a more physiologic manner.
A new cell culture device, designed by the DRI investigators, closely mimics the natural oxygen environment.
The device "sandwiches” the stem cells with oxygen from two sources:
- One from the top (air diffusing through the culture medium)
- The second from the bottom (air diffusing through a silicon membrane mixed with perfluorocarbon, a very powerful oxygen reservoir).
New device delivers ample oxygen levels
Extensive mathematical modeling showed that the stem cells cultured in the new device and receiving the higher levels of oxygen were in the natural physiologic range of islets. The standard culture conditions fell well short of the target range.
The results showed that the increased oxygen levels delivered through the device led to a massive differentiation of pancreatic endocrine cells. The stem cells cultured in conventional conditions did not achieve anywhere near the same level of differentiation.
The researchers also observed that insulin levels, as well as many critical pancreatic genes, skyrocketed.
These results are the first comprehensive analysis of the influence of oxygen levels on beta cell differentiation, and open the door to much more efficient protocols for the differentiation of embryonic stem cells into beta cells.