Objective
The aim of this proposal is to develop ECM-based, macroporous, prevascularized, retrievable biological platform favoring islet vascularization, survival and function in the subcutaneous space. Constructs will be composed of biological ECM and proteins. The highly interconnected, macroporous cryogels will be generated from placental ECM. Produced scaffolds will be seeded with islets and endothelial cells to generate a prevascularized insulin-secreting constructs. Constructs will be easy to implant, biocompatible and fully retrievable. They will have the translational potential of scaling up for preclinical testing, and ultimately clinical application.
Background Rationale
General Audience Summary - Background/Rationale
Beta cell replacement by transplantation of the whole pancreas or isolated islets of Langerhans is an efficient way of restoring glycemic control, thus preventing the occurrence of severe hypoglycemia and protecting kidney grafts from the progression of diabetic nephropathy. However, pancreas transplantation is an invasive surgical procedure, associated with a high rate of complications. Islet transplantation is less invasive, but less efficient at reversing diabetes. Additionally, several factors such as the lack of suitable pancreas donors, chronic toxicity caused by lifelong immunosuppression, and other issues are limiting the application of these modalities.
The understanding and mimicking of the β‐cell microenvironment is a critical step for the successful development of novel approaches for the bio engineering of functional constructs. The importance of cell‐ECM interaction within the islet has been extensively studied. ECM provides support for islet morphological integrity and transmits biochemical and biomechanical cues regulating cell adhesion, migration, proliferation, differentiation, and survival. It is evident that ECM is an essential component in the design of functional bioengineered insulin-secreting constructs, yet engineering a stable vascular network near the encapsulated cells is critical to allow efficient glucose sensing and insulin secretion upon implantation in the clinically relevant but poorly vascularized subcutaneous space. Among the different technologies under development, both synthetic and naturally derived extracellular matrix (ECM) based hydrogels have been extensively used as a polymeric scaffold due to their high-water content, biocompatibility, and physical properties similar to soft tissues. However, the relatively small pore sizes of conventional hydrogels have hindered their biomedical application due to limited cellular motion, cell spreading, and molecular diffusion of proteins, oxygen, and nutrients/waste products. Moreover, provision of immediate vascularization and optimization of islet cell engraftment remains the major challenge with this approach. An ideal construct would incorporate a biological extracellular matrix and have a high-density, functional, and stable vascular network in contact to the encapsulated cells, to enable attachment, protection, revascularization, and adequate perfusion. In addition, the bio-engineered vasculature of the scaffold should integrate with the islets to allow efficient glucose sensing and insulin secretion upon implantation. We hypothesize that use of an ECM-based cryogel could provide a supportive microenvironment for the islets. In addition, in vitro pre-vascularization of the constructs achieved through seeding of endothelial cells (EC) would overcome the limitations associated with delayed vascularization. In this regard, the characteristics of the human placenta and its membranes suggests that this organ might represent a promising candidate to be used as a foundation for a biological scaffold for the insulin-secreting constructs.The human amniotic membrane (hAM) and placenta ECM comprise heparan sulfate proteoglycans, types I, III, IV, V and VI collagens and glycoproteins (laminins, nidogen, fibronectin and vitronectin), which exhibit anti-inflammatory properties and beneficially influence cell function, proliferation and differentiation. Human placentas are generally discarded after birth and are thus an easily accessible raw material of consistent quality obtained without harm to the donor.
Description of Project
The low clinical performance of pancreatic islet transplantation has been ascribed to the high early loss (70%) of the engrafted cells in first 2 weeks after transplantation due to the host inflammatory reaction and the failure of early vascularization. The long-term efficacy of the surviving cells is also reduced, either by rejection if lifetime heavy immune suppressive therapy cannot be assured or by collateral effects of the systemic immunosuppressant therapy together with the progression of a fibrotic process induced by on-going biochemical inflammatory stress. Our goal is to develop ECM-based, macroporous, prevascularized, retrievable biological platform favoring islet vascularization, survival and function in the subcutaneous space. Constructs will be composed of biological ECM and proteins. The highly interconnected, macroporous cryogels will be generated from the placental ECM. Next, these scaffolds will be seeded with islets and endothelial cells to generate prevascularized insulin secreting construct. Constructs will be easy to implant, biocompatible and fully retrievable. They will have the translational potential of scaling up for preclinical testing, and ultimately clinical application.
Anticipated Outcome
We will engineer ECM-based, highly porous, prevascularized, retrievable biological platform to improve engraftment and survival of islets transplanted into the subcutaneous site.
The subcutaneous site selected for implantation will solve the issues of safety and retrieval. This project offers a major shift from the current paradigm of encapsulation, by replacing devices made of synthetic or inorganic materials with ECM-based, prevascularized, retrievable biological platform.
If successful, our innovative strategy will open new horizons in the field of regenerative medicine toward unlimited personalized cell-based treatments for type 1diabetes, thus overcoming the constraint of donor organ shortage and reducing the costs of disease management.
Relevance to T1D
Diabetes concerns a large and rapidly growing patient group. According to the International Diabetes Federation (IDF), 425 million people worldwide were estimated to be affected by diabetes in 2017. This number is predicted to reach 642 million by the year 2040. In Europe, 66 million people suffer from diabetes, and this number is expected to rise to 81 million by 2045. Type 1 diabetes accounts for about 10% of all cases of diabetes.
Developing a highly porous, prevascularized, retrievable biological platform for islet delivery will pave the way to offering a cure to patients with type 1 diabetes. If successful, our technology would offer a breakthrough in the field and open the possibility to utilize xenogeneic islets or stem cell-derived insulin-producing cells, thereby abrogating the problem of donor organ shortage. This strategy might dramatically reduce the long-term financial burden of the diabetic disease as well as the human consequences in terms of chronic complications altering general health and quality of life, permitting the large-scale treatment of diabetes at noncomplicated stages by means of functional transplantation