Studies of bystander effects in human artificial 3D tissues after charged particle microbeam irradiation
Radioprotection - Revue de la Societé Francaise de Radioprotection
The bystander effect involves cells directly hit by radiation sending out signals to adjacent non hit cells. These signals have been demonstrated to increase the probabilities of a variety of different endpoints. It has been suggested that bystander effects may well dominate radiation effects at very low doses. Most studies to date have focused on two-dimensional monolayers, often with cells that are not in contact. We were studying radiation-induced bystander effects in three-dimensional human
... e-dimensional human tissue systems. In order to maintain good reproducibility, we were using novel EpiDerm artificial human skin tissue systems (MatTek Corporation). These artificial tissues, allowed us to model conditions present in vivo. The Radiological Research Accelerator Facility (RARAF) microbeam was used to irradiate tissue samples in a known pattern (well-separated points on a line, accuracy ±2µm) with a known number of α-particles. After irradiation, the tissues models were incubated for 3 days, fixed in 10% NBF, paraffin embedded and then sliced into 5 µm histological sections located at varying distances from the plane of the irradiated cells. We were utilised 3'-OH DNA end-labeling based in situ apoptosis assay for a quantitative assessment of the apoptosis contribution to the bystander effect. We demonstrated a clear bystander response in artificial human three-dimensional skin tissue systems, established a dose dependency and estimated the role of differentiation vs. damage induction processes. In particular, fractions of apoptotic cells were measured at different distances ranging 200 to 1100 µm away from irradiated region on day 3 after irradiation. Averaged fraction of apoptosis in irradiated samples for all layers was 3.7±0.6% versus 1.3±0.3% in control. Importantly there were no statistically significant variations in expression of bystander apoptosis over 900 µm distance, which suggest that hypothetical bystander factor has a long range, could travel through 3D tissue and possibly gap junctions mediated.