Islet transplantation is the only minimally invasive therapy for Type I diabetes that is able to achieve glycemic control without exogenous insulin. However, islet transplantation shows variable success rates, mainly due to the inconsistent quality of human islet preparations. For islet transplantation to become a FDA licensed biologic product, a well- established islet preparation process and product manufacturing consistency will need to be demonstrated. Federal regulations mandate that each biologic product lot be tested for potency before being released for clinical use. At present, there is no reliable potency test available for human pancreatic islets. We hypothesize that an appropriate islet potency test must be beta-cell specific and simultaneously assess key factors associated with islet physiology, including glucose- stimulated changes in mitochondrial potentials, calcium influx and dynamic insulin secretion. To test this hypothesis, an innovative islet perfusions system with functional, live microscopy was developed using microfluidic chip technology to enable simultaneous measurement of glucose-induced changes in mitochondrial potentials, calcium influx and dynamic insulin secretion. Preliminary results indicate that this system can adequately distinguish low potency from high potency human islet preparations. This project will focus on the following aims: (1) To further improve the resolution of the microfluidic system through modification of the chip design. Specifically, our proposal focuses on: a. improving temporal resolution by reducing the volume of the chamber within the microfluidic chip, b. improving flow dynamic control and increasing ease of use by adding a fluid mixer into the chip, c. establishing glucose ramps to evaluate insulin kinetics, d. integrating multiple perfusion chambers into the chip on a motorized platform to increase the sample size of human islets that can be evaluated and provide a better representation of the final islet product. e. developing a rapid insulin secretion measurement. (2) To validate the microfluidic system in a pre-clinical nude mouse model using human islet cell grafts and develop an "Islet Potency Index " predictive of post-transplant islet graft function. Briefly, multivariable regression modeling will determine which islet cell characteristics are significantly associated with in vivo outcome and these will be used to calculate the index. (3) To test the microfluidic system in setting of a clinical human islet transplant trial and investigate the validity of the Islet Potency Index to predict islet graft function. This proposal will test an innovative microfluidic system that provides detailed analysis of pancreatic beta-cell physiology. In the future, it is likely that further developments addressing an unlimited islet cell source and new immunoprotective strategies will make islet transplantation available to a broader proportion of the diabetic population. This microfluidic system could represent a reliable islet potency assay for current and future islet replacement therapies, as well as for the study of new diabetes therapies in general.
An innovative microfluidic system will be optimized and standardized for human islet potency testing. If successful, the microfluidic-based assay could be used for islet product release testing, which represents a yet unmet regulatory requirement for FDA biologic licensure of islet transplants.
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