Investigating the suspension culture on aggregation and function of mouse pancreatic β-cells.

The integrity and hierarchical structure of islet influence β-cells physiology dramatically. A culture substrate which can maintain or improve β-cells aggregation shall benefit cell therapy for diabetics. In this study, nontreated, type IV collagen, Lipidure, and ultralow attachment dishes were used to culture a murine β-cell line, MIN-6. The formation and biological performances of pseudoislets were investigated. Results showed that β-cells formed loose and irregular aggregates on nontreated dishes. Oppositely, pseudoislets formed on other three substrates. Most pseudoislets on Lipidure and type IV collagen dishes had a diameter between 100-150 μm with high survival rate, while large pseudoislets (>250 μm) with seriously central necrosis were found on ultralow attachment dishes. Western blot analysis revealed that pseudoislets had relatively higher connexin 36 protein productions relative to single cells. The glucose-stimulated insulin secretion test showed pseudoislets on type IV collagen have high stimulation index. Monolayers from TCPS dishes and pseudoislets from type IV collagen or Lipidure dishes were further transplanted into diabetic mice. Animals received both single cells and pseudoislets had decreasing blood glucose level and regained body weight. Histologic examination revealed that all implants successfully engrafted with positive insulin staining. Interestingly, the area under curve for the intraperitoneal glucose tolerance test showed pseudoislets had superior glucose disappearance rate. This study reveals that isolated islets or insulin-producing cells can be cultured on type IV collagen or Lipidure dishes to improve/maintain integrity prior to transplantation.