Objective
The goal of this project is to converge synthetic biology with tissue engineering and apply it for subcutaneous islet transplantation to promote the survival, engraftment, and function in diabetic mice. We will use synthetic protein circuits to engineer cells to respond to specific physiological states to dynamically control vascularization , islet protective, or immunomodulatory proteins to support islet transplantation. Our strategy comprises three specific aims:
1) Engineer oxygen-sensing protein circuits to rapidly vascularize the subcutaneous space in a controlled manner to support the survival of transplanted pancreatic islets.
2) Develop and validate an ER stress-responsive protein sensor to monitor and control therapeutic proteins to improve islet viability following transplantation.
3) Combine oxygen-sensing circuits with ER stress-responsive protein sensors and user-defined activation to enable local immune modulation in the subcutaneous space to support the long-term engraftment of allogeneic pancreatic islets, without the need for systemic immunosuppression.
This highly innovative project will have broad impact on the islet transplantation field, making the subcutaneous space an amenable alternative site for islet transplantation, while simultaneously providing local immune modulation to support long-term function. The modularity and generalizability of our synthetic protein circuits will accelerate the successful and broad application of subcutaneous islet transplantation for the treatment of T1D.
Background Rationale
T1D is an autoimmune condition in which the insulin-producing beta-cells are targeted for destruction from the host's immune response. Individuals must regulate their blood glucose using insulin injections, however even with strict glucose control, secondary complications such as blindness, kidney failure and an increase risk of limb amputation still occur. Pancreatic islets infused into the liver have been shown to be a promising therapy for achieving insulin independence, but long-term survival remains poor and has driven the search for alternative transplant sites.
The subcutaneous space (space underneath the skin) is a promising alternative site due to its ability to support a large transplant volume, and ease of use; however, it must be vascularized before being able to support transplanted islets. In addition to ensuring the subcutaneous space is well-vascularized, the transplanted islets must be protected by the immune system. Instead of relying on life-long systemic immune suppression (with its own set of detrimental off-target effects), there has been a shift towards developing strategies for local immune modulation. This effectively protects the transplanted pancreatic islets from the host's immune response without affecting the rest of the body.'
Unfortunately, most local immune modulation strategies that have shown success in other transplant sites haven’t worked well in the subcutaneous space. We believe this is because many of the proteins used to modulate the immune response also interfere with how new blood vessels form. Since immune responses and vascular growth are closely linked, targeting one can unintentionally disrupt the other. Current strategies often rely on delivering islets alongside materials pre-loaded with growth factors or immune-modulating proteins, but these lack the ability to adapt to the dynamic and changing needs of the tissue environment.
To overcome these challenges, we are developing a new approach: engineering living cells that can sense local oxygen levels or cell stress and respond by secreting precisely timed and balanced combinations of factors to support both blood vessel formation and immune protection. This “smart” system can adapt as the tissue heals and matures, creating a supportive environment for islets in the subcutaneous space, potentially leading to long-lasting insulin independence without the need for systemic immunosuppression.
Description of Project
T1D is a chronic autoimmune disorder that causes the destruction of insulin-producing beta-cells. Individuals with T1D are on lifelong insulin injections to regulate blood glucose, however secondary complications can still occur. The transplantation of pancreatic islets from a cadaveric donor into the space underneath the skin (also known as the subcutaneous space) using engineered tissues has emerged as a promising therapy for T1D, but there is a need to generate robust blood vessels and implement strategies to shield the transplanted islets from the immune system to support their long-term engraftment. Recently, synthetic biology has emerged as powerful approach to create dynamic, and programmable cells capable of controlling the signals required to generate vessels and modulate the host's immune response. What remains is to develop specific sensors that can tell the engineered cells when to turn on these specific programs. The goal of this project is to develop these specific sensors, and combine the engineered cells with tissue engineering to deliver pancreatic islets into the subcutaneous space of diabetic mice and restore their blood glucose levels to normal. Our strategy is unique by converging synthetic biology and tissue engineering to address these major barriers in islet transplantation to accelerate the development of an effective and broadly applicable cure for T1D.
Anticipated Outcome
The major outcomes of this project will be: (1) the development of oxygen protein sensors to program rapid and mature vascularization of the subcutaneous space to support islet transplantation, (2) demonstration of the utility and applicability of protein sensors for non-invasive, real-time monitoring and therapeutic outputs in response to pancreatic islet ER stress, and (3) the application of programmable user-defined local immune modulation to support allogeneic islet transplantation in immune competent mice.
Relevance to T1D
This project will establish the compatibility of programmable cell therapies with tissue engineering to enable personalized approaches for pancreatic islet transplantation. Successful integration of these innovative technologies will have a broad impact on the islet transplantation field, by enabling transplanted islets to dynamically respond to changes from the host immune system using pre-defined factors to prolong the engraftment of pancreatic islets for the treatment of type 1 diabetes.