A recent study led by a team of researchers at Northwestern University has discovered a technique to help make immunomodulation more effective. The method used nanocarriers to re-engineer the commonly used immunosuppressant rapamycin.

Their paper was published in the journal Nature Nanotechnology. The Northwestern team was led by Evan Scott, the Kay Davis Professor and an associate professor of biomedical engineering at Northwestern's McCormick School of Engineering and microbiology-immunology at Northwestern University Feinberg School of Medicine, and Guillermo Ameer, the Daniel Hale Williams Professor of Biomedical Engineering at McCormick and Surgery at Feinberg. Ameer also serves as the director of the Center for Advanced Regenerative Engineering (CARE).

Individuals living with Type 1 diabetes have to carefully follow prescribed insulin regimens every day, receiving injections of the hormone via syringe, insulin pump or some other device. And without viable long-term treatments, this course of treatment becomes a lifelong sentence.

Islet transplantation emerged over the past few decades as a potential cure for Type 1 diabetes. But transplantation efforts faced setbacks as the immune system continued to eventually reject new islets. Current immunosuppressive drugs have offered inadequate protection for transplanted cells and tissues and have been plagued by undesirable side effects.

Now, using the rapamycin-loaded nanocarriers, the team of researchers from Northwestern generated a new form of immunosuppression, capable of targeting specific cells related to the transplant, without suppressing wider immune responses. Ameer had been working on improving the outcomes of islet transplantation by providing islets with an engineered environment, using biomaterials to optimise their survival and function. However, problems associated with traditional systemic immunosuppression remained a barrier to the clinical management of patients and hence, had to be addressed to truly have an impact on their care, said Ameer.

"This was an opportunity to partner with Evan Scott, a leader in immune engineering, and engage in a convergence research collaboration that was well executed with tremendous attention to detail by Jacqueline Burke, a National Science Foundation Graduate Research Fellow," Ameer said.

Rapamycin is well-studied and commonly used to suppress immune responses during other types of treatment and transplants, notable for its wide range of effects on many cell types throughout the body. Typically delivered orally, rapamycin's dosage needs to be carefully monitored to prevent toxic effects. Yet, at lower doses, it has poor effectiveness in cases such as islet transplantation.
Scott, also a member of CARE, said he wanted to see how the drug could be enhanced by putting it in a nanoparticle and "controlling where it goes within the body."

"To avoid the broad effects of rapamycin during treatment, the drug is typically given at low dosages and via specific routes of administration, mainly orally," Scott said. "But in the case of a transplant, you have to give enough rapamycin to systemically suppress T cells, which can have significant side effects like hair loss, mouth sores and an overall weakened immune system."

Following a transplant, immune cells, called T cells, will reject newly introduced foreign cells and tissues. Immunosuppressants are used to inhibit this effect but can also impact the body's ability to fight other infections by shutting down T cells across the body. But the team formulated the nanocarrier and drug mixture to have a more specific effect. Instead of directly modulating T cells -- the most common therapeutic target of rapamycin -- the nanoparticle would be designed to target and modify antigen-presenting cells (APCs) that allow for more targeted, controlled immunosuppression.

Using nanoparticles also enabled the team to deliver rapamycin through a subcutaneous injection, which they discovered uses a different metabolic pathway to avoid extensive drug loss that occurs in the liver following oral administration. This route of administration requires significantly less rapamycin to be effective -- about half the standard dose.

"We wondered, can rapamycin be re-engineered to avoid non-specific suppression of T cells and instead stimulate a tolerogenic pathway by delivering the drug to different types of immune cells?" Scott said. "By changing the cell types that are targeted, we actually changed the way that immunosuppression was achieved."

The concept of enhancing and controlling side effects of drugs via nano delivery is not a new one, Scott said. "But here we're not enhancing an effect, we are changing it -- by repurposing the biochemical pathway of a drug, in this case mTOR inhibition by rapamycin, we are generating a totally different cellular response."

The team's discovery could have far-reaching implications. "This approach can be applied to other transplanted tissues and organs, opening up new research areas and options for patients," Ameer said. "We are now working on taking these very exciting results one step closer to clinical use."

For Burke, a doctoral candidate studying biomedical engineering, the research hit closer to home. She was diagnosed with Type 1 diabetes when she was nine and daily shots became a well-known part of her life. For a long time, she wanted to somehow contribute to the field.

"At my past program, I worked on wound healing for diabetic foot ulcers, which are a complication of Type 1 diabetes," Burke said. "As someone who's 26, I never really want to get there, so I felt like a better strategy would be to focus on how we can treat diabetes now in a more succinct way that mimics the natural occurrences of the pancreas in a non-diabetic person."

The all-Northwestern research team has been working on experiments and publishing studies on islet transplantation for three years, and both Burke and Scott say the work they just published could have been broken into two or three papers. What they've published now, though, they consider a breakthrough and say it could have major implications on the future of diabetes research.

Scott has begun the process of patenting the method and collaborating with industrial partners to ultimately move it into the clinical trials stage. Commercialising his work would address the remaining issues that have arisen for new technologies like Vertex's stem-cell-derived pancreatic islets for diabetes treatment.