Concise Review: The Effect of Low-Dose Ionizing Radiation on Stem Cell Biology: A Contribution to Radiation Risk

Abstract

Exposure to high levels of ionizing radiation (IR) (>0.5 Gy) negatively affects health, but less is known about the effects of low-dose ionizing radiation (LDIR). Recent evidence suggests that it may have profound effects on cellular functions. People are commonly exposed to LDIR over natural background levels from numerous sources, including LDIR from medical diagnosis and therapy, air travel, illegal IR waste dumpsites, and occupational exposures in the nuclear and medical sectors. Stem cells reside for long periods of time in our bodies, and this increases the possibility that they may accumulate genotoxic damage derived from extrinsic LDIR or intrinsic sources (such as DNA replication). In this review, we provide an overview of LDIR effects on the biology of stem cell compartments. The principal findings and issues reported in the scientific literature are discussed in order to present the current understanding of the LDIR exposure risk and assess whether it may impact human health. We first consider the general biological consequences of LDIR exposure. Following this, we discuss the effects of LDIR on stem cells as discovered through in vitro and in vivo studies. Stem Cells 2018;36:1146-1153.

In Reply

“…Our narrative literature review focuses on the state-of-art concerning the effect of LDIR on stem cell biology, acknowledging that it is a controversial issue. Although the majority of the available literature reported negative effects induced by LDIR on different stem cell populations, null or positive effects of IR on stem cell biology were also reported, as shown in Table 3 of our article and described in text [1,2].…”

“…Consequently, the mode of action of RF and IR are quite distinct [6][7][8].Our narrative literature review focuses on the state-of-art concerning the effect of LDIR on stem cell biology, acknowledging that it is a controversial issue. Although the majority of the available literature reported negative effects induced by LDIR on different stem cell populations, null or positive effects of IR on stem cell biology were also reported, as shown in Table 3 of our article and described in text [1,2].In addition, the epidemiological evidence demonstrating the increase of the risk of some cancers following a protracted or acute exposure to LDIR have been paired in the "Biological Consequences of LDIR Exposure" section on those claiming the LDIR-induced beneficial effects in humans, as described by hormetic and adaptive responses [2]. In any case, emerging epidemiological evidence in the human population clearly shows that exposure to low and protracted doses of IR is associable with a risk for human health [9,10].The authors also discuss the nondetrimental effects on human health that are associated with natural background radiation; actually, we noted that none of the cited studies are related to stem cell effects.…”

“…Nevertheless, we believe that a punctual response to the criticisms moved by the authors can provide useful insights aiming to a better elucidation of a controversial matter like the effects of lowdose ionizing radiation (LDIR) on cell biology.We agree with the authors that the effects of IR on proliferation and differentiation of stem cells depend on several factors (such as biological system, experimental conditions, radiation energy, and duration of exposure). Indeed, in the "Evidence and Criticism" section of our article, this issue was discussed, concluding that these plethora of factors have to be analyzed to get a complete perspective on the effects of LDIR on stem cell biology [2]. We are aware that caution is important when inferring the role of a given chemical or physical agent on a specific cell system by means of studies carried out on different systems.…”

Overview of Biological, Epidemiological, and Clinical Evidence of Radiation Hormesis

“…They are reviewed in other excellent articles [1,2,4], so in the present article, we will introduce studies related to us and those in which we are particularly interested. Meanwhile, recent studies suggest that stem cells reside in the body for a long time and they may accumulate genotoxic damages derived from low-dose radiation; therefore, further investigations on stem cell biology may also be important [22,23]. …”

The cellular effects of Pulsed Electromagnetic Fields on osteoblasts: A review

“…Electromagnetic fields (EMFs) are common in everyday life, as the world is permeated by EMFs, both natural and man‐made [Olson and Amit, ]. Besides ionizing radiations, for example, Ultraviolet C or gamma rays, which are well known to profoundly interact and harm living matter [Halls, ; Squillaro et al, ], there is a whole range of non‐ionizing radiations, spanning from electricity supply lines to radio waves, which do not possess enough energy to ionize matter but can still strongly interact with biological tissues and cells [Yost, ; Hardell and Sage, ].…”