Development of a three-dimensional in vitro co-culture model to increase drug selectivity for humans.

Aim: Insulin resistance is a metabolic state where insulin sensitivity is lower than normal condition and strongly related to type 2 diabetes. However, an in vitro model mimicking insulin resistance is rare and thus screening drugs for insulin resistance severely depends on an in vivo model. Here, to increase anti-diabetic drug selectivity for humans, 3D ADMSCs and macrophages were co-cultured with in-house fabricated co-culture plates. Material and

Methods: 3D co-culture plates were designed to load ADMSCs and RAW264.7 cells containing hydrogels in separate wells while allowing cell-cell interaction with co-culturing media. Hydrogels were constructed using a 3D cell-printing system containing 20 mg/ml alginate, 0.5 mg/ml gelatin and 0.5 mg/ml type I collagen. Cells containing hydrogels in 3D co-culture plates were incubated for 10 min to allow stabilization before the experiment. 3D co-culture plates were incubated with the CaCl2 solution for 5 min to complete the cross linking of alginate hydrogel. Cells in 3D co-culture plates were cultured for up to 12 days depending on the experiment and wells containing adipocytes and macrophages were separated and used for assays.

Results: KR-1, KR-2 and KR-3 compounds were applied during differentiation (12 days) in 3D co-cultured mouse 3T3-L1 adipocytes and 3D co-cultured human ADMSCs. Glucose uptake assay using 2-DG6P and 2-NBDG and western blot analysis were performed to investigate changes of insulin resistance in the 3D co-cultured model for interspecies selectivity of drug screening. KR-1 (mouse potent enantiomer) and KR-3 (racemic mixture) showed improvement of 2-DG and 2-NBDG uptake compared with KR-2 (human potent enantiomer) in 3D co-cultured 3T3-L1 adipocytes. In connection with insulin resistance in a 3D 3T3-L1 co-cultured model, KR-1 and KR-3 showed improvement of insulin sensitivity compared to KR-2 by markedly increasing GLUT4 expression. In contrast to the result of 3D co-cultured 3T3-L1 adipocytes, KR-1 failed to significantly improve 2-DG and 2-NBDG uptake in 3D co-cultured ADMSC adipocytes. Results of 2-NBDG accumulation and western blot analysis also showed that KR-2 and KR-3 improved insulin sensitivity relatively better than KR-1.

Conclusions: Our 3D co-culture model with/without 3D co-culture plates can successfully mimic insulin resistance while allowing investigation of the effects of anti-obesity or anti-diabetic drugs on human or mouse co-culturing cell type. This 3D co-culture system may accelerate screening of drugs for insulin resistance depending on species.