A hybrid of cells and pancreatic islets toward a new bioartificial pancreas

Abstract

Cell surface engineering using single-stranded DNA-poly(ethylene glycol)-conjugated phospholipid (ssDNA-PEG-lipid) is useful for inducing cell-cell attachment two and three dimensionally. In this review, we summarize our recent techniques for cell surface engineering and their applications to islet transplantation. Because any DNA sequence can be immobilized onto the cell surface by hydrophobic interactions between ssDNA-PEG-lipid and the cellular membrane without impairing cell function, a cell-cell hybrid can be formed through the DNA hybridization. With this technique, it would be possible to create three-dimensional hybrid structures of pancreatic islets coated with various accessory cells, such as patients' own cells, mesenchymal and adipose-derived stem cells, endothelial progenitor cells, neural crest stem cells or regulatory T cells, which might significantly improve the outcome of islet transplantation in diabetic patients.

Keywords: Cell surface modification; Diabetes; IBMIR, instant blood-mediated inflammatory reaction; Instant blood-mediated inflammatory reaction (IBMIR); PEG-conjugated phospholipid (PEG-lipid); PEG-lipid, poly(ethylene glycol)-conjugated phospholipid; PMPC, poly(2-methacryloyloxyethyl phosphorylcholine); Pancreatic islet; islets, islets of Langerhans.

Fig. 1

Amphiphilic polymers employed for cell surface modifications. (a) Chemical structures of amphiphilic polymers: polyethylene glycol-conjugated phospholipid (PEG-lipid). (b) Cell surface modification by hydrophobic interaction. Cell surfaces can be modified with PEG-lipid that interacts with the membrane through hydrophobic interactions. (c) Confocal laser scanning microscopy image of a CCRF-CEM cell that was modified with polyA20–PEG-lipids and then reacted with FITC-polyT20.

Fig. 2

Schematic illustration of a method for cell immobilization on a pattern printed in DNA. First, immobilization of DNA with a specific sequence on the cell surface was done with DNA–PEG-lipids. Second, printing a pattern with DNA′-SH was performed by an inkjet printer. The cells modified by DNA–PEG-lipid were applied to the substrate and immobilized on the pattern.

Fig. 3

(a) Schematic illustration of cell surface modification with ssDNA–PEG-lipid by hydrophobic interaction and of cell–cell attachment by DNA hybridization. Cells were modified with polyA20–PEG-lipid and polyT20–PEG-lipid and then mixed to induce attachment. (b) During the cell–cell attachment, ssDNA–PEG-lipid on the cell surface moved towards the interface between the two cells and elicited DNA hybridization, which induced the cell–cell attachment. (c) Influence of the shape of cells attached by DNA hybridization with different ssDNA ratios to PEG-lipid without DNA: 2.5, 10, and 100 mol%. With an increased ssDNA ratio on the cell surface, the cell–cell attachment strengthened with the larger contact area.

Fig. 4

A 3D hybrid of pancreatic islets and living cells created via DNA hybridization. (a) Schematic illustration of the coating of an islet within living cells. Both the cell and islet surfaces are modified with polyDNA. polyT20–PEG-lipid is immobilized on living HEK293 cells, and polyA20–PEG-lipid is immobilized on the islet surface. During mixing of the modified cells and islets, DNA hybridization causes the attachment of HEK293 cells onto the islet surfaces. After several days of culture, HEK293 proliferation encloses the islet within a cellular capsule. (b) Phase contrast microscopy and fluorescence microscopy of islets with attached HEK293 cells. At 0 day, GFP-HEK293 cells immobilized to islets were observed with confocal laser-scanning microscopy, and after 3 day, frozen sections of islets with attached GFP-HEK293 cells were stained with Alexa488-labeled anti-insulin antibody (green) and Hoechst 33342 dye (blue) for nuclear staining (Partially modified from Ref. [42]).