An open question in radiobiology concerns whether low doses of radiation are harmful or if cells are able to tolerate such exposure with minimal or no disruption. This issue is relevant for evaluating public health risks associated with the increasing number of medical computed tomography (CT) diagnostic procedures. This study evaluated the impact of CT scan-level exposure on human adipose mesenchymal stem cells (hMSCs) by measuring DNA damage responses (γH2AX, 53BP1, pATM foci), proliferation (Ki-67), senescence (β-galactosidase), and multiple gene expressions. Responses to one or five CT exposures were compared to a 2 Gy X-ray dose at intervals from 1 h to 10 passages post-irradiation. It was shown that CT scan briefly increased DNA damage markers but showed no significant long-term effects. A high dose of 2 Gy X-ray exposure caused sustained DNA damage, decreased proliferation, increased senescence, and significant changes in hundreds of genes even after several cell generations. After a single CT exposure, gene expression changes were minimal, while high-dose exposure led to strong activation of DNA repair and stress response pathways. Five CT scans caused a slight activation of LIF and HSPA1B genes, but these effects were minor compared to the high-dose group. All detected effects from CT scans were not observed by ten cell passages, whereas high-dose effects persisted. In conclusion, typical CT scan exposures have only short-term, mild effects on hMSCs, while high-dose radiation causes lasting cellular and genetic changes.

The growing use of computed tomography (CT) in medicine requires a better understanding of how low-dose radiation affects human stem cells. This study investigated the long-term consequences of CT-level radiation on the secretory profile of human adipose-derived mesenchymal stem cells (AD-MSCs). AD-MSCs were exposed to radiation regimens simulating a single or multiple head CT scans, or to a single 2 Gy therapeutic dose, and their secretion of 41 cytokines, chemokines, and growth factors was monitored during long-term culture. At the early passage, AD-MSCs receiving a single 2 Gy dose showed a coordinated increase in several lymphocyte-regulating cytokines compared to cells exposed to multiple CT scans. However, these initial differences were not sustained. Long-term culturing led to a progressive and widespread decrease in the secretion of 26 cytokines, chemokines, and growth factors across all groups. By the latest passage, all irradiated cells showed a generalized reduction in secretory function compared to non-irradiated controls. These findings demonstrate that while different radiation regimens trigger distinct immediate responses, long-term culture results in a broad decline of the AD-MSCs secretome, which is accentuated by prior radiation exposure. This underscores the importance of assessing long-term consequences to fully evaluate the functional impact of diagnostic radiation on stem cells.