Extracellular Matrix Scaffold Technology for Bioartificial Pancreas Engineering: State of the Art and Future Challenges

Abstract

Emergent technologies in regenerative medicine may soon overcome the limitations of conventional diabetes therapies. Collaborative efforts across the subfields of stem cell technology, islet encapsulation, and biomaterial carriers seek to produce a bioengineered pancreas capable of restoring endocrine function in patients with insulin-dependent diabetes. These technologies rely on a robust understanding of the extracellular matrix (ECM), the supportive 3-dimensional network of proteins necessary for cellular attachment, proliferation, and differentiation. Although these functions can be partially approximated by biosynthetic carriers, novel decellularization protocols have allowed researchers to discover the advantages afforded by the native pancreatic ECM. The native ECM has proven to be an optimal platform for recellularization and whole-organ pancreas bioengineering, an exciting new field with the potential to resolve the dire shortage of transplantable organs. This review seeks to contextualize recent findings, discuss current research goals, and identify future challenges of regenerative medicine as it applies to diabetes management.

Keywords: bioartificial pancreas; diabetes mellitus; extracellular matrix; insulin; regenerative medicine; stem cells.

Figure 1.

Schematic representation of decellularization–recellularization technology. (A) Whole organ consisting of both the cellular compartment (red shapes) and the ECM (blue network), which contains also growth factors (green dots). (B) Acellular organ, after stripping of all cells (red shapes have been cleared off). Native ECM (blue network) supposedly remains intact and preserved in all its fundamental components, growth factors (green dots) included. (C) The new organ is reconstituted with autologous cells (yellow shapes). Adapted from Orlando et al, with permission.

Figure 2.

Decellularization of whole porcine pancreas. (A) Porcine pancreas upon collection, with cannulated pancreatic duct. (B) The same pancreas after decellularization, showing a characteristic whitish/translucent appearance. (C, D) H&E staining of native and acellular porcine pancreas, respectively; the dense cellularity of the native pancreas is lost post detergent perfusion (arrow indicates an islet, which is extrapolated in the small cartoon). Adapted from Mirmalek-Sani et al, with permission.

Figure 3.

Appearance of the innate, intrinsic vasculature in the decellularized porcine pancreas. (A, B) Perfusion of fluorescein isothiocyanate (FITC)–labeled dextran beads inside the decellularized pancreas, shown under fluorescent and bright light microscopy, respectively. (C) High magnification of panel A shows intact vessels inside the decellularized pancreas perfused with FITC-labeled dextran beads. (D) Fluoroangiograph of acellular porcine pancreas vasculature following perfusion of Conray® contrast agent. (F) Scanning electron micrograph of a preserved blood vessel with intact and smooth basal lamina layer. Scale bar = 200 µm. Adapted from Mirmalek-Sani et al, with permission.

Figure 4.

Immunohistochemistry of acellular porcine pancreas ECM. IHC staining shows widespread expression of structural ECM proteins, namely collagen type I (A), collagen type III (B), collagen type IV (C), and laminin (D, E). (F) Scanning electron micrograph depicting dense and fibrous arrangement of matrix proteins (scale bars = 200 µm (A-C), 500 µm (D), 100 µm (E), and 20 µm (F)). Adapted from Mirmalek-Sani et al, with permission.

Figure 5.

Functionality test of porcine islets seeded on porcine ECM. Time course data from perfusion of control (unseeded) porcine islets (blue) or islets seeded onto acellular pancreatic matrix (green). Groups were cultured for 3 days then subjected to a glucose challenge. Low glucose levels (3.3 mM) represented physiological euglycemia of 60 mg/dL, and the transition to high glucose (11.1 mM) represented the upper limit postprandial levels of 200 mg/dL. Both groups displayed increased insulin secretion during high glucose perfusion, with islets seeded onto scaffolds demonstrating higher peak insulin secretion values, observed specifically at 50, 55 and 75 minutes. Both groups showed a reduction of insulin secretion after a return to low (basal) glucose concentration. Adapted from Mirmalek-Sani et al, with permission.