ENGINEERING OF NEOVASCULARIZED-PANCREAS-ON-A-CHIP MODEL
Open Access
- Author:
- Hospodiuk, Monika
- Graduate Program:
- Biorenewable Systems
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 26, 2019
- Committee Members:
- Jeffrey M Catchmark, Dissertation Advisor/Co-Advisor
Jeffrey M Catchmark, Committee Chair/Co-Chair
Ibrahim Tarik Ozbolat, Committee Chair/Co-Chair
Paul Heinz Heinemann, Committee Member
William O Hancock, Outside Member
Nicole Brown, Committee Member - Keywords:
- pancreas
vascularization
organ on a chip
tissue engineering
ECM
perfusion
hydrogel
3D bioprinting - Abstract:
- Tissue engineering is relatively new interdisciplinary application of the biological and biomedical sciences. A deeper understanding of the relationships between structure and function of healthy and pathological tissues is necessary in order to develop substitutes to restore or improve organ function. A fundamental idea of tissue engineering is cell growth and proliferation in three-dimensional (3D) matrix materials to mimic their natural environment. The classic approach of cell culture bases on flat surfaces, like multi-well plates, unrepresentative of most tissues in a human body. Therefore, controlled cell-matrix microenvironments that enable healthy cell-cell interactions are critical for understanding tissue formation. This research focuses on the development of simulated 3D printable extracellular matrix materials and perfusion devices needed to create functional organ-on-chip pancreas systems. Due to the limited supply of organs for transplantation, successfully engineered and fully functional human organoid will be a milestone in tissue engineering and regenerative medicine. Novel approaches have been investigated for vascularization of 3D soft tissues, highly essential for successful fabrication of physiologically-relevant tissue models. Here, the focus is on creating vascularized pancreatic islets, which brings new perspectives in the treatment for patients with type I diabetes. It is urgent, since diabetes type I will double over the next decade if current rates of increase continue. The pancreatic spheroids were formed by β-cells and endothelial cells co-cultured together, which maintained over 80% viability and at least twice higher insulin secretion as compared to non-vascularized β-cell-only spheroids. In the co-cultured spheroids, angiogenesis provided a network within the scaffold that supplied nutrients to cells and drained metabolites, including insulin. The spheroids were cultured in fibrin-only scaffold with a high level of cellular performance; however, due the ultimate goal of creating pancreas-on-a-chip model, the mechanical properties of fibrin were insufficient. Also, fibrin is characterized by rapid degradation and non-shear thinning nature, preventing extrusion-based bioprinting. Therefore, an ionically crosslinking and bioprintable hydrogel was developed based on functionalized bacterial cellulose, where its charge ratio influenced stiffness, morphology, and pore size. The new hydrogel and fibrin were combined with Matrigel®, collagen, and hyaluronic acid as a series of engineered hydrogel scaffolds that simulated the natural pancreas environment to provide an improved local microenvironment for sprouting spheroids. The tissue model was examined for at least a seven-day culture to provide data of cellular and molecular changes accompanying the tissue formation. It resulted in elevated gene expression of endothelial cell-related genes as VEGF-A, endothelin1, and NOS3 as well as twice higher insulin secretion on the 4th and 7th day of culture compared to the control. Later, the pancreatic tissue spheroids were deposited into a perfusable, hydrogel-based device under dynamic culture conditions. The perfused tissue model responded to glucose by insulin secretion that was detectable in real-time at the outlet of the device. Also, perfusion with a Sunitinib pharmaceutical stopped the growth of the vascularization over a 7-day dynamic culture by the inhibition of VEGFRs. In conclusion, the pancreas-on-a-chip device fabricated based on vascularized engineered islets combined with the pancreas simulated ECM scaffold can be used for both insulin detection as well as for drug testing. This approach preserved the functionality of the pancreatic islets and is potentially useful for type I diabetes research as well as drug testing therapy for cancer models.