A hydrogel ‘invisibility cloak’ could protect transplanted diabetes cells from immune attack and reduce the need for immunosuppressive drugs.
The experimental coating was tested on insulin-producing cells transplanted into diabetic mice, restoring healthy blood sugar within a week in treated animals.
Researchers said the approach could eventually make cell therapies less reliant on drugs that suppress the immune system, although further studies and human clinical trials will be needed.
The work was led by researchers at Penn State, who developed an ultrathin hydrogel coating called the biomimetic zona pellucida, or BZP.
“Specific clusters of cells, known as islets, can release sugar-sustaining insulin in the bodies of patients with diabetes,” said Yong Wang, professor of biomedical engineering and corresponding author on the research.
“However, these donor islets are targeted and attacked by the patient’s immune system.
“Existing treatment options require patients to continuously take immunosuppressants to stop this response, which can lead to significant side effects, including cancer.”
Hydrogels are water-rich, jelly-like materials that can be engineered to surround and protect living cells.
The BZP coating was designed to mimic the zona pellucida, the natural protective layer surrounding human egg cells.
In diabetes cell therapy, clusters of insulin-producing cells known as islets can be transplanted into patients to help regulate blood sugar.
However, because donor cells can be recognised as foreign by the immune system, patients may need immunosuppressant medicines to stop the transplanted cells being attacked.
These medicines reduce immune activity but can increase the risk of infections and other serious complications.
The researchers developed a BZP layer around 20 micrometres thick, considerably thinner than a human hair.
The coating is permeable, meaning substances such as insulin can pass through it while the transplanted cells remain protected from immune attack.
The team said it took eight years to develop a coating thin enough to conform to living cells without interfering with their function.
“Our body is amazing, by mimicking the natural, ultrathin coating formed by proteins on egg cells, we can fortify and cloak cells for therapeutic transplantation,” said Kyungsene Lee, first author of the research.
Scientists coated pancreatic islets with BZP before transplanting them into diabetic mice and monitored their blood glucose levels for 100 days.
Mice receiving the coated cells returned to healthy blood sugar levels within a week, and most remained diabetes-free for more than 100 days without continuous immunosuppressant treatment.
According to the researchers, uncoated transplanted cells typically remained effective for one week or less without systemic immunosuppression, meaning treatment that suppresses immune activity throughout the body.
The team now plans to investigate how long the protective effect lasts and whether the technology can be developed further towards human clinical testing.
Researchers also believe the approach could have uses beyond diabetes, including regenerative medicine, which aims to repair or replace damaged tissues, and immunotherapy, which uses the immune system to treat disease.
“This technique could be useful in immunotherapy, priming cells to resist chronic disease, or in regenerative medicine, stimulating cell growth to regenerate tissues in damaged or lost organs,” Wang explained.
“Simply speaking, BZP could be massively helpful across a broad span of biomedical engineering applications.”
