The effects of high ambient glucose on the radiosensitivity of retinal microvascular endothelial cells and pericytes

Enhancement of glycolysis-dependent DNA repair regulated by FOXO1 knockdown via PFKFB3 attenuates hyperglycemia-induced endothelial oxidative stress injury

The accumulation of DNA damage induced by oxidative stress is a crucial pathogenic factor of endothelial loss in diabetic vascular complications, but it is still unknown whether aberrant glucose metabolism leads to defective DNA repair and accounts for hyperglycemia-induced endothelial oxidative stress injury. Here, we showed that Foxo1 knockdown alleviated diabetes-associated retinal DNA damage and vascular dysfunction. Mechanistically, FOXO1 knockdown avoided persistent DNA damage and cellular senescence under high glucose in endothelial cells by promoting DNA repair mediated by the MRN (MRE11-RAD50-NBS1 complex)-ATM pathway in response to oxidative stress injury. Moreover, FOXO1 knockdown mediated robust DNA repair by restoring glycolysis capacity under high glucose. During this process, the key glycolytic enzyme PFKFB3 was stimulated and, in addition to its promoting effect on glycolysis, directly participated in DNA repair. Under genotoxic stress, PFKFB3 relocated into oxidative stress-induced DNA damage sites and promoted DNA repair by interaction with the MRN-ATM pathway. Our study proposed that defective glycolysis-dependent DNA repair is present in diabetic endothelial cells and contributes to hyperglycemia-induced vascular dysfunction, which could provide novel therapeutic targets for diabetic vascular complications.

Radiobiological Studies of Microvascular Damage through In Vitro Models: A Methodological Perspective

Ionizing radiation (IR) is used in radiotherapy as a treatment to destroy cancer. Such treatment also affects other tissues, resulting in the so-called normal tissue complications. Endothelial cells (ECs) composing the microvasculature have essential roles in the microenvironment's homeostasis (ME). Thus, detrimental effects induced by irradiation on ECs can influence both the tumor and healthy tissue. In-vitro models can be advantageous to study these phenomena. In this systematic review, we analyzed in-vitro models of ECs subjected to IR. We highlighted the critical issues involved in the production, irradiation, and analysis of such radiobiological in-vitro models to study microvascular endothelial cells damage. For each step, we analyzed common methodologies and critical points required to obtain a reliable model. We identified the generation of a 3D environment for model production and the inclusion of heterogeneous cell populations for a reliable ME recapitulation. Additionally, we highlighted how essential information on the irradiation scheme, crucial to correlate better observed in vitro effects to the clinical scenario, are often neglected in the analyzed studies, limiting the translation of achieved results.

Cytotoxic and genotoxic effects of matrices for cartilage tissue engineering

Customizing auricles with biodegradable polyurethane colonized with autologous chondrocytes as an approach for tissue engineering cartilage transplants has been suggested for the reconstruction of the external ear to repair auricular deformities. Dextrose, triethanolamine and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) are matrices of an open-pored polyurethane three-dimensional scaffold. After release from the polymer, these compounds can be absorbed into the human organism. Therefore, cytotoxic effects on human chondrocytes and lymphocytes and genotoxic effects on human lymphocytes were determined. Propidium iodide and fluoresceine diacetate staining as well as quantitative proliferations testing with EZ4U served to detect cytotoxic effects on chondrocytes. In lymphocytes cytotoxicity was checked by trypan blue staining and the alkaline single cell microgel electrophoresis (Comet) assay was used to study genotoxic effects. Dose-dependent cytotoxicity and genotoxicity of the matrices could be shown. Concentrations up to 4.25mg/ml for dextrose, 0.15 mg/ml for PEG-PPG-PEG and 0.9 mg/ml for triethanolamine did not show cytotoxic effects in chondrocytes or genotoxic effects in lymphocytes. These data suggest that dextrose, triethanolamine and PEG-PPG-PEG could be safely used if scaffolds made of open-pored polyurethane do not release these compounds at a rate giving higher concentrations at the site of implantation or in body fluids, respectively.