Human Pancreatic Ductal Cells: Large-Scale Isolation and Expansion

Abstract

The in vitro differentiation of pancreatic stem cells has recently been shown to represent a new source of β cells for cell therapy in diabetes. Human ductal cell differentiation, in vitro, has been documented in three-dimensional (3D) culture and recently substantiated. Although encouraging, the optimization of the ductal cell source, expansion and differentiation ex vivo are mandatory for clinical relevance. We compared three sources of human ductal cells (hDC) (method A1-2, B, and C). The classical main duct isolation of hDC by explant (A1), or enzymatic digestion (A2), was compared with two indirect methods: from 3D cultured human islet/duct-enriched fractions (B) and dedifferentiated exocrine fractions (C). Method A: few viable hDC were obtained from the main duct. Method B: embedding islet/duct rich fraction in 3D collagen gels expands the cytokeratin 19 (CK19)-positive ductal component in the form of ductal cysts, as we described previously; monolayers derived from digested cysts were 80% ductal (CK19). Method C: initially adherent amylase-positive exocrine clusters contained 12% (CK19) to 22% (CK7) ductal cells. One-week exocrine cultures were amylase negative and 46% (CK19) to 63% (CK7) ductal. Cell viability varied: <20% (A1), 81 ± 12% (B), 91 ± 2% (C). Extrapolating total yields we obtained (±SEM): 10.5 ± 4.6 × 103 (A1), 36 ± 18 × 103 (A2), 292 ± 50 × 106 (B), 1696 ± 526 × 106 (C) viable hDC per pancreas. A secondary monolayer expansion of cyst-derived hDC (method B) was achieved with NuSerum® (4.2-fold on plastic, 2.6-fold on 804G matrix; p < 0.05 vs. control cells on plastic). First passage exocrine-derived ductal cells also responded to matrix and to growth factors, albeit not significantly. In conclusion, this study demonstrated that an abundant hDC supply can be obtained from islet/duct or exocrine fractions followed by monolayer expansion with NuSerum. If their differentiation capacity is confirmed, in particular exocrine-derived ductal cells may represent a promising abundant source of islets for allogenic and autologous diabetes cell therapy.