Spleen Replaces Pancreas
- Jenner Nex
- 5 days ago
- 4 min read
Reprogrammed Spleen Produces Insulin in Mice and Monkeys
Reprogrammed: There is a natural bioreactor in which vital cells can be grown and regenerated directly in the body – the spleen. As a new study demonstrates, the spleen of mice and monkeys can be modified so that it can, for example, replace the insulin-producing cells of the pancreas – essentially acting as a replacement organ within the body. If this becomes possible in humans in the future, it could revolutionize the treatment of type 1 diabetes. However, further tests are still needed.
In type 1 diabetes, the insulin-producing beta cells in the pancreas are damaged by an autoimmune reaction. Without these cells, blood sugar control is impossible. While insulin injections help many sufferers, some patients are left with an organ transplant as the only long-term solution to compensate for this loss. However, organs from human donors are far fewer than needed. Furthermore, the transplants are often rejected by the recipient's body. The same applies to organs from animals.
As an alternative, physicians are researching the transplantation of individual insulin-producing cells from multiple donors. However, these implanted cells have not yet survived long enough in the recipients' pancreases to regrow insulin-producing tissue and cure diabetes in the long term. The reasons for this include the invasive nature of the surgery and the poor nutrient supply in the pancreas.
The spleen as a bioreactor?
In light of this problem, a team led by Mi Liu from Wenzhou Medical University in China has researched a new method: They have modified the spleen of animals in such a way that new islet cells can be cultivated within it to form functional pancreatic tissue.
The idea behind it: Although the spleen purifies our blood, it is a comparatively little-used organ and not necessarily essential for the survival of adults. Therefore, when it is remodeled, no critical bodily functions are lost. Furthermore, the spleen, with its porous structure, offers ample space for additional cells, is easily accessible via surgery, and is well supplied with fresh, nutrient-rich blood. All of this makes the spleen an ideal location for organ maturation, so the thinking goes.
Remodeling the Spleen
"We are essentially converting the spleen into a high-performance bioreactor," explains co-author Lei Dong from Nanjing University. To this end, the researchers developed sugar-coated silicon nanoparticles (KSiNPs) that reprogram the spleen's microenvironment, thus preventing rejection of transplanted cells. For their experiment, the team injected these nanoparticles into the spleens of mice.
The results showed that the particles interact with the immune system's phagocytes and connective tissue cells in the spleen. As a result, they locally suppress the immune system and promote connective tissue growth in the organ. "By improving the support of the extracellular matrix, accelerating blood vessel growth, and suppressing immune attacks, we have created an ideal niche for the growth of transplanted cells," says Dong.
Successful Tests in Mice and Monkeys
Further tests confirmed this: When the researchers implanted 200 islet cells from mice or rats into the reprogrammed mouse spleens, they actually grew into functional tissue. The pancreatic tissue cultivated in this way was subsequently able to maintain blood sugar levels in the mice for at least 90 days by secreting insulin. In the animals, the retooled spleen thus took over the function of the pancreas when it was deactivated by medication.
But does this also work in primates? To test this, the researchers also applied this procedure to cynomolgus monkeys. They first reprogrammed their spleens using the nanoparticles and then populated them with thousands of human, insulin-producing islet cells. The result: The cells matured into human islet tissue in the monkey spleen, as Liu and colleagues discovered.
The pancreatic tissue grown in the monkey spleen also proved to be functional: For 28 days, the modified spleen produced enough insulin to keep the monkeys' blood sugar levels constant – even though their pancreas had been disabled. The researchers found no side effects.
Organ replacement in one's own spleen?
According to the research team, such a "remodeling" of the spleen could be a promising strategy against diabetes. Instead of transplanting entire organs, one would simply equip an existing organ – the spleen – with additional functions. According to Liu and colleagues, the method used is compatible with human and animal cells and provides a functional organ replacement that is not rejected. In theory, this procedure should therefore also work with the human spleen.
However, before such organ reconstruction can be tested and applied in humans, thorough safety tests and follow-up studies are still necessary, as the researchers also admit. In the future, they want to expand their spleen bioreactor technology so that it can be used to specifically cultivate the organ a patient needs from induced pluripotent stem cells (iPSCs).
Previous studies by the team have already shown that organs other than the pancreas can, in principle, grow in the spleen—such as liver or thyroid tissue. "With minimally invasive B-ultrasound-guided delivery, we could one day grow customized organs on demand," Dong hopes.
(Science Translational Medicine, 2025; doi: 10.1126/scitranslmed.adj9615)
Source: Nanjing University, American Association for the Advancement of Science (AAAS)
