Poster Presentation Australian Diabetes Society and the Australian Diabetes Educators Association Annual Scientific Meeting 2017

Bioengineering a biofunctionalised synthetic capsule for in vivo implantation of MIN6 beta cells (#210)

Jason Tong 1 2 , Wan J Gan 1 2 , Elena Kosobrodova 2 3 , Anthony S Weiss 2 4 , Steven G Wise 5 , Marcela MM Bilek 3 , Peter Thorn 1 2
  1. Discipline of Physiology, School of Medical Sciences, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
  2. Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia
  3. School of Physics, Faculty of Science, The University of Sydney, Sydney, NSW, Australia
  4. School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Sydney, NSW, Australia
  5. Heart Research Institute, Sydney, NSW, Australia

Implantation to replace lost beta-cells is an attractive treatment option for Type 1 diabetes (T1D). However, the autoimmune disorder in patients necessitates immunosuppression, which is undesirable. Any successful approach must protect implanted cells from autoimmune destruction. Encapsulation is a promising solution. Several challenges remain: long-term maintenance of implanted cell function, and poor vascularisation and fibrotic rejection of implants. We address these issues by generating a synthetic capsule to provide an optimal environment for beta-cell implantation.

We biofunctionalised polymers by depositing basement membrane (BM) proteins using plasma ion immersion implantation (PIII), a treatment that allows strong, non-toxic adhesion of proteins onto surfaces. Using microcontact-printing, we patterned polymer surfaces with fibronectin and BSA. PIII-treatment increases specific binding of the proteins on surfaces compared to untreated controls.

As a proof-of-concept, we selected hollow PIII-treated polymer fibres containing 10µm pores. These pores allow insulin secretion and nutrient exchange, but prevent immune cell penetration. We coated fibre interiors with BM-protein fibronectin for enhancement of cell survival and growth (1), then injected MIN6 beta-cells. Secretion assays show that cells grown in fibronectin-coated capsules secrete insulin in a glucose-dependent manner similar to controls on coated glass-coverslips. Furthermore, microscopy of fibre interiors show similar morphology to controls.

Next, fibres were PIII-treated and exteriorly coated with tropoelastin. Fibres were bundled and implanted subcutaneously in mice. Implants were retrieved at multiple timepoints. Fluorescent microscopy of tissue slices shows that tropoelastin-exterior coated capsules show no fibrosis and improved vascularisation compared to uncoated controls. Finally, immune cell staining showed no luminal invasion.

This work has provided evidence for a novel encapsulation technique for beta-cell implants in T1D-patients. Ongoing work is refining these methods and will lead to testing of beta cell-containing implants in animal disease models, including streptozotocin-treated and non-obese-diabetic mice, to examine long-term beta cell function, survival and reversal of the diabetic phenotype.

  1. Gan, W.J., Zavortink, M., Ludick, C., Templin, R., Webb, R., Webb, R., Ma, W., Poronnik, P., Parton, R.G., Gaisano, H.Y. and Shewan, A.M., 2017. Cell polarity defines three distinct domains in pancreatic β-cells. J Cell Sci, 130(1), pp.143-151.