A saponin from astragalus promotes pancreatic ductal organoids differentiation into insulin-producing cells

Background: Islet transplantation is an effective treatment for the type 1 and severe type 2 diabetes, but it is restricted by the severe lack of pancreas donors. In vitro differentiation of pancreatic progenitors into insulin-secreting cells is one of the hopeful strategies in the cell transplantation therapy of diabetes. Isoastragaloside I is one of the saponin molecules found in Astragalus membranaceus, which has been demonstrated to alleviate insulin resistance and glucose intolerance in obese mice.

Study design: We established mouse pancreatic ductal organoids (mPDOs) with progenitor characteristics and an insulin promoter-driven EGFP reporter system to screen astragalus saponin components for monomers that can promote insulin-producing cell differentiation.

Methods: mPDOs treated with or without astragalus saponin monomers were investigated by the insulin promoter-driven EGFP reporter, quantitative PCR, immunofluorescence and flow cytometry to evaluate the expression of endocrine progenitor and β-cell markers.

Results: Isoastragaloside I significantly promoted the expression of β-cell differentiation genes, which was demonstrated by the activation of the insulin promoter-driven EGFP reporter, as well as the significant increase of mRNA levels of the endocrine progenitor marker Ngn3 and the β-cell markers insulin1 and insulin2. Immunostaining studies indicated that the β-cell-specific C-peptide was upregulated in isoastragaloside I-treated mPDOs. FACS analysis revealed that the ratio of C-peptide-secreting cells in isoastragaloside I-treated mPDOs was over 40%. Glucose tolerance tests demonstrated that the differentiated mPDOs could secrete C-peptide in response to glucose stimulation.

Conclusions: We discover a novel strategy of inducing pancreatic ductal progenitors to differentiate into insulin-producing cells using isoastragaloside I. This approach can be potentially applied to β-cell transplantation in diabetes therapies.