The aim of this study was to develop a scaleable process to expand pancreatic endocrine tissue (i.e., aggregates or islet-like structures) in suspension bioreactors. Key issues addressed included (i) serum-free media, (ii) cell inoculation density, (iii) medium pH, and (iv) aggregate dissociation. Suspension bioreactors were inoculated with pancreatic neonatal tissue and operated under controlled conditions for a 9-day period. Medium studies showed that a new serum-free medium developed in our laboratory was capable of supporting endocrine cell expansion. An inoculation density of 127,000 cells/mL resulted in more than a 7.5-fold increase in the number of insulin-positive cells after 9 days. The resulting population consisted of single cells and many islet-like aggregates that contained all of the endocrine cell types (including insulin-positive, glucagon-positive, somatostatin-positive, and pancreatic polypeptide-positive cells). Furthermore, the cell aggregates exhibited a glucose-responsive behavior. This study represents a significant milestone on the path to the effective expansion of human islet-like tissue in bioreactors that may be used for cell therapy to treat Type 1 diabetes.
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