LET-Dependent Low Dose and Synergistic Inhibition of Human Angiogenesis by Charged Particles: Validation of miRNAs that Drive Inhibition

Wuu et al., iScience, 2020 asked how the charged particle radiation found beyond low Earth orbit stops new blood vessels forming, and whether that damage can be undone. Human three dimensional micro-vessel cultures built from umbilical vein endothelial cells were irradiated at the NASA Space Radiation Laboratory at Brookhaven National Laboratory, both with single ion species and with a five ion simulation of galactic cosmic radiation. Two separate mechanisms emerged, split by linear energy transfer. Ions below 3 KeV per atomic mass unit blocked the early motile stage, cutting motile tips by about 80%, and could be rescued by a protein kinase C stimulator. Ions above 8 KeV per atomic mass unit blocked the later tube forming stage and could not be rescued that way. Mixing the two was synergistic rather than additive: a 1 to 1 mixture of protons and iron ions inhibited vessel formation significantly at a total dose of 0.03 Gy, more than four times lower than either ion needed on its own.

Three circulating microRNAs the group had previously tied to spaceflight and to cardiovascular risk, miR-16-5p, miR-125b-5p and let-7a-5p, were the candidate carriers of that damage between cells. To test them the study used AUMantagomir sdASO from AUM BioTech. The key resources table lists AUM as the supplier and prints the catalogue codes: twelve inhibitors, four against each microRNA, and a matched scramble control. All three inhibitors were applied to the micro-vessel cultures together, with no transfection reagent named anywhere in the paper, so the oligonucleotides reached endothelial cells inside a gel matrix unaided.

Micro-vessels irradiated with 0.5 Gy of the simulated galactic cosmic radiation beam failed to develop. In cultures given the three AUMantagomir sdASO, the micro-vessels formed, while the scramble control left them inhibited. A second experiment removed radiation from the picture altogether and grew micro-vessels in nutrient depleted medium, half normal growth medium and half basal medium with no additives; all the inhibitors significantly restored full micro-vessel growth over the depleted controls. The authors read the two results together as evidence that the radiation damage is carried by microRNAs and can be interrupted at that level.