Rotational co-culture of clonal β-cells with endothelial cells: effect of PPAR-γ agonism in vitro on insulin and VEGF secretion

Aim: Delayed graft revascularization impedes the success of human islet transplantation. This study utilized rotational co-culture of insulin secreting beta-cells with human umbilical vein endothelial cells (HUVECs) and a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist to promote insulin and vascular endothelial growth factor (VEGF) secretory function. Methods: Clonal BRIN-BD11 (D11) cells were maintained in static culture (SC) and rotational culture (RC) +/- HUVEC and +/- the TZD (thiazolidinedione) rosiglitazone (10 mmol/l) as a specific PPAR-gamma agonist. HUVECs were cultured in SC and RC +/- D11 and +/- TZD. D11 insulin secretion was induced by static incubation with low glucose (1.67 mmol/l), high glucose (16.7 mmol/l) and high glucose with 10 mmol/l theophylline (G+T) and assessed by enzyme-linked immunosorbent assay (ELISA). HUVEC proliferation was determined by ATP luminescence, whereas VEGF secretion was quantified by ELISA. Co-cultured cells were characterized by immunostaining for insulin and CD31. Results: D11 SC and RC showed enhanced insulin secretion in response to 16.7 mmol/l and G+T (p < 0.01); without significant alteration by the TZD. Co-culture with HUVEC in SC and RC also increased D11 insulin secretion when challenged with 16.7 mmol/l and G+T (p < 0.01), and this was slightly enhanced by the TZD. The presence of HUVEC increased D11 SC and RC insulin secretion in response to high glucose and G+T, respectively (p < 0.01). Addition of the TZD increased SC and RC HUVEC ATP content (p < 0.01) and VEGF production (p < 0.01) in the presence and absence of D11 cells. Conclusions: Rotational co-culture of insulin secreting cells with endothelial cells, and exposure to a PPAR gamma agonist may improve the prospects for graft revascularization and function after implantation.