Photosynthetic co-culture system of algae and human umbilical vein endothelial cells: The effect on alleviating hypoxia and hypoxia/reoxygenation injury

It is a developed photosynthetic co-culture system to alleviate the hypoxia and hypoxia/reoxygenation (H/R)-injured human umbilical vein endothelial cells (HUVECs). The algae, Chlorella vulgaris, were encapsulated to slow their growth while not affecting the photosynthetic oxygen-producing capacity by Layer-by-layer (LbL) using gelatin and sodium alginate as the positive and negative charges materials, respectively. Then, the photosynthetic co-culture system of HUVECs and self-oxygenating alginate hydrogel (Algae-gel) was constructed in which the optimal ratios between algae and HUVECs were 5:1 and 20:1 for a 2D or 3D co-cultured manner, respectively. It indicated that the 3D co-cultured manner of HUVECs needed more O₂ by the production of algae than it did in a 2D co-cultured manner. The co-cultured Algae-gel could alleviate hypoxia and the oxidative stress injury of hypoxia and hypoxia/reoxygenation (H/R)-treated HUVECs in the proliferation, intracellular ROS and cellular migratory ability. In addition, the Algae-gel could downregulate the expression of hypoxia-inducible factors 1α (HIF-1α) and vascular endothelial growth factor (VEGF) of hypoxia and H/R-injured HUVECs due to the improvement of hypoxia and H/R injury. This photosynthetic co-culture system could offer a promising approach for repairing hypoxia and H/R-injured cells or tissue by providing safe and stable O₂.