Human islet amyloid polypeptide (hIAPP) was used to mimic T2DM and was co-oligomerized with Aβ1-42 peptide, and delivered to the central of human iPSC-derived mature COs through intermittently repeated microinjections, so as to simulate the chronic exposure to Aβ within the brain. The gene discussed is IAPP; the disease is type 2 diabetes mellitus.