Isolation and Induction of Differentiation of Seine Adipose-Derived Mesenchymal Stem Cells

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.

Hydration of hydrogels regulates vascularization in vivo

The key barrier to the clinical application of tissue engineering scaffolds is the limitation of rapid and sufficient vascularization. Adipose-derived stem cells (ASCs), especially multicellular aggregates, exhibited a promising angiogenic activity. Herein, we designed a series of poly(l-glutamic acid) (PLGA)-based hydrogels with tunable hydration to control the in situ formation of multicellular spheroids. Oligo(ethylene glycol)s (OEGs) were employed to regulate the hydration of hydrogels. The hydrogel cross-linked with ethylene glycol (OEG1) supported the most excellent adhesion and proliferation of human ASCs in vitro. However, as the hydration of hydrogels strengthened, the adherent ASCs were gradually replaced with multicellular spheroids. Moreover, the in situ formation of spheroids was more effective in upregulating hypoxia-adaptive signals (e.g., hypoxia-inducible factor-1α, HIF-1α) and enhancing the secretion of angiogenic factors (e.g., vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF-2)) compared to adherent cells in OEG1 hydrogels. The hydrogel cross-linked with oligo(ethylene glycol)400 (OEG9) carrying spheroids induced a high angiogenic response of host tissue in vivo, resulting in an improved system vascularization, compared to adherent cells in the OEG1 hydrogel. These features indicated that the PLGA-based hydrogels were expected to be applied toward bone and fat tissue regeneration.