By Hendra Lukman 
Stanford, CA – In a significant leap forward for autoimmune disease research, scientists at Stanford Medicine have reported a groundbreaking development in the treatment of Type 1 diabetes. Their latest study, published in the esteemed Journal of Clinical Investigation, details a novel approach that successfully prevented or completely reversed Type 1 diabetes in mice by administering a combination of blood-forming stem cells and pancreatic islet cells from immunologically mismatched donors. This pioneering strategy effectively re-educates the recipient’s immune system, creating a state of tolerance that halts the autoimmune assault on insulin-producing cells.
The implications of this research are profound, offering a glimmer of hope for millions worldwide affected by Type 1 diabetes, an autoimmune condition characterized by the body’s immune system mistakenly attacking and destroying its own insulin-producing beta cells within the pancreas. The chronic nature of this disease necessitates lifelong insulin therapy and careful blood sugar management, with significant long-term health risks.
A Hybrid Immune System: The Key to Tolerance
At the heart of this breakthrough lies the creation of a "hybrid immune system" within the recipient mice. This innovative approach involves transplanting both hematopoietic stem cells (which give rise to all blood and immune cells) and pancreatic islet cells from a donor who is not genetically matched to the recipient. Crucially, the study found that none of the treated animals developed graft-versus-host disease (GVHD), a potentially life-threatening complication where the donor’s immune cells attack the recipient’s healthy tissues. Furthermore, the autoimmune destruction of the recipient’s own islet cells ceased entirely.
"The possibility of translating these findings into humans is very exciting," stated Seung K. Kim, MD, PhD, the KM Mulberry Professor and a distinguished figure in developmental biology, gerontology, and endocrinology and metabolism at Stanford University. "The key steps in our study—which result in animals with a hybrid immune system containing cells from both the donor and the recipient—are already being used in the clinic for other conditions. We believe this approach will be transformative for people with Type 1 diabetes or other autoimmune diseases, as well as for those who need solid organ transplants."
The study’s senior author, Dr. Kim, who also directs the Stanford Diabetes Research Center and the Northern California Breakthrough T1D Center of Excellence, highlighted the dual action of this therapeutic strategy. It not only replaces the damaged insulin-producing cells but also fundamentally alters the immune system’s destructive response. Preksha Bhagchandani, a graduate and medical student at Stanford, served as the lead author of the research, underscoring the collaborative nature of this significant scientific endeavor.
Building on a Foundation: From Induced Diabetes to Autoimmunity
This latest achievement is a significant advancement building upon earlier work by Dr. Kim and his team. In a landmark study published in 2022, the researchers demonstrated the potential of combined stem cell and islet transplantation in a model of chemically induced diabetes. In that research, they first triggered diabetes in mice using toxins to eliminate their insulin-producing cells. They then employed a carefully orchestrated pre-transplant regimen involving immune-targeting antibodies and low-dose radiation. This preparation, followed by the transplantation of blood stem cells and islet cells from an unrelated donor, successfully restored blood sugar control in these animals.
However, the current study presented a far more formidable challenge: addressing Type 1 diabetes driven by the body’s own aberrant immune response. In human Type 1 diabetes, the immune system spontaneously identifies islet cells as foreign invaders and launches a persistent attack, leading to their destruction. Unlike the induced diabetes model, where the primary hurdle was overcoming the recipient’s immune rejection of donor islets, this new model involved transplanted islets facing a dual threat. They were recognized as foreign, and simultaneously, the recipient’s immune system was already primed to destroy islet cells regardless of their origin.
"Just like in human Type 1 diabetes, the diabetes that occurs in these mice results from an immune system that spontaneously attacks the insulin-producing beta cells in pancreatic islets," Dr. Kim explained. "We need to not only replace the islets that have been lost but also reset the recipient’s immune system to prevent ongoing islet cell destruction. Creating a hybrid immune system accomplishes both goals." The inherent biological characteristics that drive autoimmune diabetes in these mouse models also posed a greater difficulty in safely preparing them for blood stem cell transplantation.
A Refined Protocol: Overcoming Autoimmune Obstacles
The research team identified a surprisingly simple yet effective modification to their existing protocol to overcome these challenges. By incorporating a medication commonly used in the treatment of autoimmune diseases into the pre-transplant regimen, they achieved remarkable success. Bhagchandani and Stephan Ramos, PhD, a postdoctoral fellow and co-author of the study, integrated this additional drug into the protocol that had been established in 2022.
Following this adjusted protocol and subsequent blood stem cell transplantation, the mice developed a hybrid immune system comprising cells from both the donor and the recipient. In a striking outcome, 19 out of 19 mice in this group did not develop Type 1 diabetes. In a separate cohort of animals that already had established Type 1 diabetes, a remarkable nine out of nine were fully cured after receiving the combined blood stem cell and islet cell transplant. This dual success in both prevention and reversal underscores the potency of their refined approach.
The significance of this finding is amplified by the fact that the antibodies, drugs, and low-dose radiation used in the mouse protocol are already integral components of standard clinical practice for blood stem cell transplantation. This existing clinical familiarity significantly de-risks the transition of this strategy toward human trials for Type 1 diabetes.
Legacy of Tolerance: From Kidney Transplants to Autoimmune Reset
This groundbreaking research draws heavily on decades of foundational work by the late Samuel Strober, MD, PhD, a revered professor of immunology and rheumatology at Stanford, and his colleagues, including study co-author Judith Shizuru, MD, PhD, a professor of medicine. Their pioneering research demonstrated that bone marrow transplants from partially immunologically matched human donors could induce a hybrid immune system in recipients, leading to the long-term acceptance of kidney transplants from the same donor. In some patients, this resulted in stable kidney function for decades without the need for continuous immunosuppressive drugs, a testament to achieved immune tolerance.
While blood stem cell transplants are a well-established treatment for hematologic malignancies such as leukemia and lymphoma, these procedures typically involve high-dose chemotherapy and radiation to eradicate the recipient’s original immune system. This aggressive conditioning can lead to severe side effects. Dr. Shizuru and her team have been instrumental in developing safer, less intensive conditioning regimens for patients with non-cancerous conditions, including Type 1 diabetes. Their aim has been to reduce bone marrow activity just enough to allow donor blood stem cells to engraft and flourish, minimizing toxicity.
"Based on many years of basic research by us and others, we know that blood stem cell transplants could also be beneficial for a wide range of autoimmune diseases," Dr. Shizuru commented. "The challenge has been to devise a more benign pre-treatment process, diminishing risk to the point that patients suffering from an autoimmune deficiency that may not be immediately life-threatening would feel comfortable undergoing the treatment."
The current study appears to have met this challenge. "Now we know that the donated blood stem cells re-educate the recipient animal’s immune system to not only accept the donated islets, but also not attack its healthy tissues, including islets," Dr. Kim elaborated. "In turn, the donated blood stem cells and the immune system they produce learn to not attack the recipient’s tissues, and graft-versus-host disease can be avoided." This elegant reciprocal tolerance is the cornerstone of their therapeutic success.
Navigating Future Hurdles and Broadening Impact
Despite the overwhelmingly positive results in the mouse models, significant obstacles remain before this promising strategy can be widely implemented for Type 1 diabetes treatment in humans. A primary challenge is the current reliance on islets obtained solely from deceased donors. Furthermore, the blood stem cells must originate from the same donor as the islets, creating a logistical hurdle in sourcing matched donor pairs. The adequacy of islet cells typically recovered from a single donor to reverse established Type 1 diabetes also remains an open question.
The Stanford team is actively pursuing solutions to these limitations. Research is underway to develop methods for generating vast quantities of functional islet cells in the laboratory from pluripotent human stem cells. Concurrently, efforts are focused on enhancing the survival and efficiency of transplanted donor islets post-transplantation.
Beyond Type 1 diabetes, Dr. Kim, Dr. Shizuru, and their collaborators envision a broader application for their gentle pre-conditioning strategy. They believe it holds immense potential for treating other autoimmune conditions, such as rheumatoid arthritis and lupus, as well as non-cancerous blood disorders like sickle cell anemia, where current stem cell transplant methods are particularly harsh. The approach could also revolutionize solid organ transplantation, enabling transplants between mismatched donors and recipients with reduced risk of rejection and long-term immunosuppression.
"The ability to reset the immune system safely to permit durable organ replacement could rapidly lead to great medical advances," Dr. Kim concluded, emphasizing the transformative potential of their work.
The research was generously supported by funding from the National Institutes of Health (grants T32 GM736543, R01 DK107507, R01 DK108817, U01 DK123743, P30 DK116074 and LAUNCH 1TL1DK139565-0), the Breakthrough T1D Northern California Center of Excellence, Stanford Bio-X, the Reid Family, the H.L. Snyder Foundation and Elser Trust, the VPUE Research Fellowship at Stanford, and the Stanford Diabetes Research Center. This multifaceted support underscores the national and institutional commitment to advancing Type 1 diabetes research and finding a cure.
