title: Capsule stiffness regulates the efficiency of pancreatic differentiation of human embryonic stem cells.
abstract: Encapsulation of donor islets using a hydrogel material is a well-studied strategy for islet transplantation, which protects donor islets from the host immune response. Replacement of donor islets by human embryonic stem cell (hESC) derived islets will also require a means of immune-isolating hESCs by encapsulation. However, a critical consideration of hESC differentiation is the effect of surrounding biophysical environment, in this case capsule biophysical properties, on differentiation. The objective of this study, thus, was to evaluate the effect of capsule properties on growth, viability, and differentiation of encapsulated hESCs throughout pancreatic induction. It was observed that even in the presence of soluble chemical cues for pancreatic induction, substrate properties can significantly modulate pancreatic differentiation, hence necessitating careful tuning of capsule properties. Capsules in the range of 4-7kPa supported cell growth and viability, whereas capsules of higher stiffness suppressed cell growth. While an increase in capsule stiffness enhanced differentiation at the intermediate definitive endoderm (DE) stage, increased stiffness strongly suppressed pancreatic progenitor (PP) induction. Signaling pathway analysis indicated an increase in pSMAD/pAKT levels with substrate stiffness likely the cause of enhancement of DE differentiation. In contrast, sonic hedgehog inhibition was more efficient under softer gel conditions, which is necessary for successful PP differentiation.
  
  
  CONCLUSIONS
  Cell replacement therapy for type 1 diabetes (T1D), affecting millions of people worldwide, requires the immunoisolation of insulin-producing islets by encapsulation with a semi-impermeable material. Due to the shortage of donor islets, human pluripotent stem cell (hPSC) derived islets are an attractive alternative. However, properties of the encapsulating substrate are known to influence hPSC cell fate. In this work, we determine the effect of substrate stiffness on growth and pancreatic fate of encapsulated hPSCs. We precisely identify the range of substrate properties conducive for pancreatic cell fate, and also the mechanism by which substrate properties modify the cell signaling pathways and hence cell fate. Such information will be critical in driving regenerative cell therapy for long term treatment of T1D.
authors.affiliation: Department of Chemical Engineering, University of Pittsburgh, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Richardson
authors.affiliation: Department of Chemical Engineering, University of Pittsburgh, United States.
authors.forename: Sierra
authors.initials: S
authors.lastname: Barner
authors.affiliation: Department of Bioengineering, University of Pittsburgh, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Candiello
authors.affiliation: Department of Chemical Engineering, University of Pittsburgh, United States; McGowan Institute of Regenerative Medicine, University of Pittsburgh, United States; Department of Bioengineering, University of Pittsburgh, United States; Department of Mechanical and Materials Science, University of Pittsburgh, United States; Department of Oral Biology, University of Pittsburgh, United States.
authors.forename: Prashant N
authors.initials: PN
authors.lastname: Kumta
authors.affiliation: Department of Chemical Engineering, University of Pittsburgh, United States; McGowan Institute of Regenerative Medicine, University of Pittsburgh, United States; Department of Bioengineering, University of Pittsburgh, United States. Electronic address: ipb1@pitt.edu.
authors.forename: Ipsita
authors.initials: I
authors.lastname: Banerjee
mesh_terms: D000464:Alginates / Q000494:pharmacology; D001672:Biocompatible Materials / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D018914:Cells, Immobilized / Q000166:cytology / Q000187:drug effects; D004058:Diffusion; D004707:Endoderm / Q000166:cytology; D020723:Glucuronic Acid / Q000494:pharmacology; D053823:Hedgehog Proteins / Q000378:metabolism; D006603:Hexuronic Acids / Q000494:pharmacology; D000066449:Human Embryonic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D010179:Pancreas / Q000166:cytology*; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D053823:Hedgehog Proteins; D006603:Hexuronic Acids; D016212:Transforming Growth Factor beta; D020723:Glucuronic Acid
keywords: Alginate encapsulation; Diabetes; Human embryonic stem cells; Pancreatic differentiation; Substrate stiffness