Researchers at Stanford Medicine have achieved a groundbreaking advancement by administering a combination of blood-forming stem cells and pancreatic islet cells from an immunologically incompatible donor to mice. This innovative treatment either entirely prevented the onset of Type 1 diabetes or completely reversed it in the animals. Type 1 diabetes occurs when the body’s immune system erroneously identifies and destroys the insulin-producing islet cells located in the pancreas.
Remarkably, none of the mice exhibited signs of graft-versus-host disease, a potentially dangerous complication where the immune cells derived from the donated blood stem cells assault the recipient’s healthy tissues. Furthermore, the recipient mice’s original immune system ceased its destructive assault on the islet cells. Following the transplantation procedure, the mice required no immunosuppressive medications or insulin injections throughout the entire six-month observation period.
Seung K. Kim, MD, PhD, who holds the KM Mulberry Professorship and serves as a professor in developmental biology, gerontology, endocrinology, and metabolism, expressed profound enthusiasm about the potential for these discoveries to benefit humans. “The prospect of applying these results to human patients is incredibly promising,” he stated. “The critical elements of our experimental protocol-which foster the development of a hybrid immune system incorporating cells from both the donor and the recipient-are already employed in clinical settings for treating various other disorders. We are confident that this methodology will revolutionize care for individuals battling Type 1 diabetes, other autoimmune conditions, and those requiring solid organ transplants.”
As the senior author of the study, Kim oversees the Stanford Diabetes Research Center and the Northern California Breakthrough T1D Center of Excellence. The research appeared online on November 18 in the Journal of Clinical Investigation. Preksha Bhagchandani, a graduate and medical student, served as the lead author on this pivotal work.
Expanding on Prior Stem Cell and Islet Cell Research
These latest findings represent a significant evolution from a 2022 investigation conducted by Kim and his team. In that preliminary study, the scientists induced diabetes in mice through the use of toxins that selectively eliminated the pancreas’s insulin-producing cells. Subsequently, they employed a mild preparatory regimen prior to transplantation, which included immune-targeting antibodies and a low dose of radiation. This was followed by the infusion of blood stem cells and islet cells sourced from a donor with no immunological match, successfully reinstating normal blood sugar regulation in the subjects.
In their most recent experiment, the research group tackled a far more complex issue: the prevention or cure of autoimmune-driven diabetes. This condition arises when the immune system spontaneously attacks and eliminates the body’s own islet cells-a scenario directly analogous to Type 1 diabetes in humans. Unlike the toxin-induced model, where the primary objective was to avert rejection of the donor islets by the recipient’s immune defenses, the autoimmune model presented dual threats to the transplanted islets. Not only were they perceived as foreign entities, but they were also vulnerable to an immune system already conditioned to target islet cells indiscriminately, regardless of origin.
Kim elaborated, “Much like the pathology observed in human Type 1 diabetes, the condition in these mice stems from an immune response that autonomously destroys the beta cells responsible for insulin production within pancreatic islets.” He emphasized, “Our strategy must simultaneously replenish the depleted islets and reprogram the recipient’s immune system to halt further destruction. The creation of a hybrid immune system effectively addresses both imperatives.”
However, the very immunological characteristics that precipitate autoimmune diabetes in these mice also complicate the safe preconditioning necessary for blood stem cell transplantation.
A Straightforward Medication Adjustment Yields Complete Protection Against Diabetes
The research team devised an elegantly simple solution to this hurdle. Preksha Bhagchandani and Stephan Ramos, PhD-a postdoctoral fellow and co-author-incorporated a widely used medication for autoimmune disorders into the preconditioning protocol established in 2022. This refined approach, culminating in blood stem cell transplantation, enabled the mice to cultivate a hybrid immune system composed of donor and recipient cells. Consequently, none of the 19 mice developed Type 1 diabetes. In a parallel cohort of mice with pre-existing, long-term Type 1 diabetes, all nine subjects achieved full remission following the dual transplant of blood stem cells and islet cells.
Since the antibodies, pharmaceuticals, and low-dose radiation employed in these experiments are already integral to standard clinical protocols for blood stem cell transplants, the researchers view the transition to human trials for Type 1 diabetes patients as a feasible and imminent progression.
From Kidney Transplant Tolerance to Hybrid Immunity for Diabetes Management
This breakthrough builds upon foundational work pioneered by the late Samuel Strober, MD, PhD, a distinguished professor of immunology and rheumatology, alongside colleagues including Judith Shizuru, MD, PhD, a professor of medicine and co-author on the current study. Strober, Shizuru, and fellow Stanford researchers had previously demonstrated that a bone marrow transplant from a partially matched human donor could engender a hybrid immune system in the recipient, facilitating enduring acceptance of a kidney transplant from the identical donor. In certain cases, they observed that the transplanted kidney maintained stable function for decades, obviating the need for continuous anti-rejection therapies.
Blood stem cell transplants are routinely utilized in the treatment of hematologic malignancies and immune disorders, such as leukemia and lymphoma. Traditionally, these interventions necessitate aggressive chemotherapy and high-dose radiation to eradicate the patient’s endogenous blood and immune systems, frequently resulting in severe adverse effects. Shizuru and her collaborators have pioneered a gentler, less toxic preparatory method tailored for patients with non-malignant conditions like Type 1 diabetes. This approach modestly suppresses bone marrow function, creating an environment conducive to the engraftment and proliferation of donor stem cells.
Shizuru noted, “Drawing from extensive foundational research by our group and others, we recognize the broad therapeutic potential of blood stem cell transplants for numerous autoimmune diseases.” She added, “The primary obstacle has been refining a preconditioning regimen that minimizes risks, making it palatable for patients with autoimmune conditions that, while debilitating, are not acutely life-threatening.”
Kim further explained, “The transplanted blood stem cells effectively retrain the recipient’s immune apparatus to tolerate the donor islets without assaulting the host’s own healthy tissues, including its native islets. Reciprocally, the donor-derived immune system adapts to spare the recipient’s tissues, thereby circumventing graft-versus-host disease.”
Anticipated Challenges in Advancing Type 1 Diabetes Therapies
While the outcomes in mice are highly promising, several substantial barriers must be surmounted before this technique can be broadly implemented for Type 1 diabetes treatment in humans. Presently, pancreatic islets are procurable solely from deceased donors, and the requisite blood stem cells must originate from the same donor as the islets. Moreover, it remains unclear whether the quantity of islets harvested from a single donor will consistently suffice to ameliorate longstanding Type 1 diabetes.
To address these constraints, the investigators are pursuing innovative strategies. These include the laboratory generation of vast quantities of islet cells from human pluripotent stem cells and the refinement of techniques to enhance the longevity and efficacy of transplanted donor islets post-implantation.
Extending beyond diabetes, Kim, Shizuru, and their associates posit that their mild preconditioning paradigm could pave the way for stem cell therapies in additional autoimmune pathologies, such as rheumatoid arthritis and lupus, as well as non-oncologic hematologic conditions like sickle cell anemia-where extant transplant protocols remain unduly rigorous. It also holds promise for solid organ transplants from immunologically mismatched donors.
Kim concluded optimistically, “Safely recalibrating the immune system to enable sustained organ replacement stands poised to catalyze profound advancements in medicine.”
Funding for the study was provided by 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.
