Objective
The objective of this proposal is to 3D bioprint computationally generated, multiscale vascular networks to control islet loading within the 3D device space to enhance scalability and reproducibility, as well as integrate vascular features to support nutritional delivery and glucose responsiveness. This is enabled by FRESH 3D bioprinting, which provides powerful biofabrication and ease in translation to larger scale manufacturing. Further, by integrating optical coherence tomography (OCT) imaging into the bioprinting process, we will achieve in-process monitoring and post-print validation to provide accelerated development and the quality control required for clinical translation.
Background Rationale
For pancreatic islet transplants, the surrounding ECM is critical for cell support (mitigation of anoikis), as well as promoting vascularization. While others have demonstrated the benefits of using biomaterials and growth factors in promoting islet survival and function, these methods lack reproducibility, control of vascular infiltration, and effective islet distribution within the material platform]. Researchers have also shown that 3D bioprinting can be used to engineer 3D vascular-like channels to achieve perfusion and maintain viability and function of cells. However, the direct 3D bioprinting of ECM has proved challenging and been largely limited to photocrosslinked gelatin methacrylate or casting fibrin or collagen gels around sacrificial filaments, neither of which can recreate the multiscale vasculature found within the pancreas. We have developed freeform reversible embedding of suspended hydrogels (FRESH) 3D bioprinting, which can create functional tissues and computationally-generated multiscale vasculature with distinct 3D control of the ECM and cells. Importantly, with FRESH we can simultaneously address multiple factors that drive vascularization including (i) direct printing of vascular-like channels within collagen scaffolds with diameters from 100 µm up to 10 mm, (ii) microporosity that enables rapid cell infiltration, (iii) the ability to form microvasculature within the scaffolds down to the capillary scale (~8 µm), (iv) controlled release of growth factors such as platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) to promote angiogenesis, and (v) formation of confluent human endothelial monolayers on the luminal surfaces of the FRESH printed collagen. Thus, FRESH printing provides a broad biofabrication platform uniquely suited for engineering high-density islet tissue constructs with integrated vasculature.
Description of Project
This proposal aims to develop, integrate and validate new technologies for the advanced manufacturing of vascularized tissue constructs composed of high-density human islets. Specifically, we are focused on 3D bioprinting pro-angiogenic ECM scaffolds to improve construct manufacturing and quality. Furthermore, we seek to address key capabilities needed to transform 3D bioprinting from a laboratory-scale, one-off fabrication approach, towards industrial scalability for the development of cellular implants for treating Type 1 diabetes (T1D). The goal for the 2-year proposal is to meet critical milestones: (i) a new biofabrication approach integrating high-density human islets within a computationally-designed multiscale vascular network created using FRESH printing of collagen-based scaffolds, (ii) an integrated 3D bioprinter and optical coherence tomography (OCT) system to provide in process monitoring and feedback of tissue fidelity and reproducibility during fabrication, and (iii) in vitro and in vivo validation of islet viability and function within the 3D bioprinted ECM scaffolds. This work will establish key manufacturing capabilities, address unmet clinical needs in terms of high-density and high-viability islet tissue constructs, and impact noted JDRF priorities in terms of reproducible processes for integrating cells, biomaterials, and other components into complex engineered tissue constructs for implantation, which are amenable to large scale manufacturing.
Anticipated Outcome
We anticipate being able to 3D print a collagen-based scaffold with a perfusable vascular-like channels that support the viability and function of islets in millimeter to centimeter scale volumetric constructs. These constructs will be validated using a combination of in vitro perfusion bioreactors and in vivo pre-clinical animal models.
Relevance to T1D
The relevance of the engineered islet constructs is to provide an improved bioengineered device for islet transplantation into Type I diabetics. The multiscale vascularization we are bioprinting is intended to improve the viability and glucose responsiveness of the islets by accelerating the speed of, and degree of vascularization once implanted.