Research Projects
Tissue Engineering a Pancreatic Substitute Based on Autologous Cells
The development of tissue based therapies for a pancreatic substitute is hampered by the low
availability of donor tissue and/or the need to immunosuppress the transplant recipient. Tissue substitutes
based on non-pancreatic cells retrieved from the same patient and engineered for physiologically responsive
insulin secretion have the potential to overcome both of these limitations. The long-range goal associated with
this research program is to produce the fundamental knowledge and enabling technologies for developing an
efficacious and immune acceptable tissue substitute based on such cells. Our overall objective is to engineer a
pancreatic substitute consisting of two components: one, based on recombinant hepatic cells and the second,
based on recombinant enteroendocrine cells. For more information, please see our pertinent publications
and the work of Heather Bara. In this project, our lab collaborates
with
Professor Peter Thule, VA Hospital and Emory University, Atlanta, GA; and
Professor Nicholas Simpson,
Department of Medicine University of Florida, Gainesville, FL.
Cryopreservation of Tissue Engineered Substitutes
To realize its potential, tissue engineering must generate substitutes that can be preserved in the long-term.
Preservation is essential for off-the-shelf availability, storage and distribution of constructs fabricated at a
large-scale at centralized locations, as well as for sterlity testing and quality control. The long-range goal
associated with this research is to develop a fundamental understanding of how the various cryopreservation
parameters affect cellular and tissue construct function, and on the basis of this knowledge to develop widely
applicable preservation protocols. Our objective is to evaluate the effect of ice-forming and ice-free cry preservation (vitrification) on cell viability
and construct function for a model pancreatic tissue substitute consisting of insulin-secreting cells and a
hydrogel biomaterial. Specifically, we aim to: 1) determine cell osmotic tolerance limits and cryoprotectant
cytotoxicity and define the domain of conditions under which to cryopreserve cells used in tissue substitutes;
2) characterize in vitro the effect of cryopreservation on construct structure and function; 3) evaluate the in
vivo functionality of cryopreserved substitutes. The effect of cryopreservation on cells is assessed on the
basis of cell viability, apoptosis, and metabolic and secretory functions; and on biomaterials
on the basis of their structural integrity and functionality. For more information on this project, please see
the work of Neil Mukherjee (link), Hajira Ahmad and Alison Stucky. In this project, our lab
collaborates with Dr. Ying Song, Medical College of Georgia and Xytex, Inc., Augusta, GA; Professor
Nicholas Simpson, Department of Medicine University of Florida, Gainesville, FL; and Dr. Kelvin Brockbank,
Cell and Tissue Systems, Inc.
Non-Invasive Monitoring of Tissue Engineered Implants
Non-invasive monitoring of substitutes provides a very important link between construct implantation
and end-point physiologic effects. We have opted to use nuclear magnetic resonance (NMR) imaging and spectroscopy
methods to assess the structural integrity and functionality of tissue constructs in vitro and in vivo. Previous
work focused on using 1H NMR spectroscopy in vitro and in vivo, and 31P and 13C NMR spectroscopy in vitro to
assess aspects of construct function. More recently, we started to focus on monitoring the dissolved oxygen (DO)
concentration in tissue implants, as oxygen availability is a critical parameter that directly influences a
construct’s desired function and DO can be measured by 19F NMR spectroscopy. For this, we are co-encapsulating a
perfluorocarbon (PFC) emulsion with the cells and are using the correlation between the T1 relaxation of 19F and
the DO level to monitor the latter in the capsules. Initial experiments were performed in vitro using an
NMR-compatible perfusion bioreactor and support circuit. Fernie Goh is continuing these experiments and
expanding them to small animals in vivo. In this project, our lab collaborates with Dr. Robert C. Long, Jr.,
Department of Radiology, Emory University; and with Professor Nicholas Simpson, Department of Medicine
University of Florida, Gainesville, FL.
Bioreactor Systems for Islet Maturation and Evaluation
This project focuses on developing bioreactor systems for the maturation of neonatal porcine islets. Indeed, it
is expected that perfusion bioreactors providing a defined and controlled chemical and fluid mechanical
environment will allow for improved islet viability and functional development relative to static, fed-batch
cultures. Operating conditions for improved islet maturation are being explored. Furthermore, we are developing
single-pass perfusion systems for characterizing the secretory response of free and encapsulated insulin-secreting
cells as a measure of the functional quality of a prospective implant. For more information, please see the work of
Saif Al-Mamari. In this project, our lab
collaborates with Dr. Jose Avila, Department of Surgery, Emory University School of Medicine.