Where Do Transplanted Beta Cells Go In The Body?

Islet transplantation is an emerging therapy that aims to restore insulin-producing beta cells in people with type 1 diabetes (T1D). But an important question is: where in the body should these cells be placed?

Transplantation sites can be broadly divided into two categories: intravascular (through blood vessels) and extravascular (into tissues outside the bloodstream).

In the healthy pancreas, insulin released by beta cells enters a blood vessel called the portal vein, which carries blood directly to the liver. For this reason, the portal vein is usually used to inject islets into the liver. This intravascular approach allows transplanted islets to quickly access oxygen, glucose and nutrients through the bloodstream. However, the contact with blood triggers an inflammatory, clotting and immune response that destroys a large portion of the transplanted islets.

To address this challenge, researchers are exploring extravascular sites, where islets are directly placed within tissues. Two such sites that are being tested are the subcutaneous space (under the skin), and beside a muscle in the abdomen (the rectus sheath). The subcutaneous space is easy to reach and transplanted cells can be removed if needed. However, because there are not many blood vessels there to provide oxygen and nutrients, strategies to promote blood vessel growth need to be used. The rectus sheath of the abdominal is directly in front of the rectus muscle. This site has lots of blood vessels and can support new blood vessel formation.

In summary, the site of islet transplantation is critical for the survival and function of transplanted islets. The best site for islet transplantation remains unknown. Ongoing research is focused on identifying or engineering sites that provide the optimal balance of oxygen, blood supply, safety, and effectiveness.

About the author

Ying Deng

Ying Deng is a PhD student in Molecular Biology at the University of Montreal and Institut de recherches cliniques de Montréal (IRCM). Her research focuses on understanding the roles of vascular cells in beta cell development and function to improve cell therapies for Type 1 Diabetes.