Cytogenetic methods in human biomonitoring: principles and uses

Exploring cytokinesis block micronucleus assay in Croatia: A journey through the past, present, and future in biomonitoring of the general population

In this study, we used the cytokinesis-block micronucleus (CBMN) assay to evaluate the background frequency of cytogenetic damage in peripheral blood lymphocytes of the general population concerning different anthropometric data and lifestyle factors. The background frequency of CBMN assay parameters was analysed in 850 healthy, occupationally non-exposed male and female subjects (average age, 38±11 years) gathered from the general Croatian population from 2000 to 2023. The mean background values for micronuclei (MNi) in the whole population were 5.3±4.3 per 1000 binucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 0.7±1.3 and of nuclear buds (NBUDs) 3.1±3.2. The cut-off value, which corresponds to the 95th percentile of the distribution of 850 individual values, was 14 MNi, 3 NPBs, and 9 NBUDs. Results from our database also showed an association of the tested genomic instability parameters with age and sex but also with other lifestyle factors. These findings underscore the importance of considering several anthropometric and lifestyle factors when conducting biomonitoring studies. Overall, the normal and cut-off values attained here present normal values for the general population that can later serve as baseline values for further human biomonitoring studies either in Croatia or worldwide.

Identification of Genomic Instability in Cows Infected with BVD Virus

An important factor for dairy cattle farmers is the profitability of cattle rearing, which is influenced by the animals' health and reproductive parameters, as well as their genomic stability and integrity. Bovine viral diarrhea (BVD) negatively affects the health of dairy cattle and causes reproductive problems. The aim of the study was to identify genomic instability in cows with reproductive disorders following infection with the BVD virus. The material for analysis was peripheral blood from Holstein-Friesian cows with reproductive problems, which had tested positive for BVD, and from healthy cows with no reproductive problems, which had tested negative for BVD. Three cytogenetic tests were used: the sister chromatid exchange assay, fragile sites assay, and comet assay. Statistically significant differences were noted between the groups and between the individual cows in the average frequency of damage. The assays were good biomarkers of genomic stability and enabled the identification of individuals with an increased frequency of damage to genetic material that posed a negative impact on their health. The assays can be used to prevent disease during its course and evaluate the genetic resistance of animals. This is especially important for the breeder, both for economic and breeding reasons. Of the three assays, the comet assay proved to be the most sensitive for identifying DNA damage in the animals.

Assessment of radiation doses and DNA damage in pediatric patients undergoing interventional procedures for vascular anomalies

Interventional procedures (IPs) have been widely used to treat vascular anomalies (VA) in recent years. However, patients are exposed to low-dose X-ray ionizing radiation (IR) during these fluoroscopy-guided IPs. We collected clinical information and IR doses during IPs and measured biomarkers including γ-H2AX, chromosome aberrations (CA), and micronuclei (MN), which underpin radiation-induced DNA damage, from 74 pediatric patients before and after IPs. For the 74 children, the range of dose-area product (DAP) values was from 1.2 to 1754.6 Gy∙cm², with a median value of 27.1 Gy∙cm². DAP values were significantly higher in children with lesions in the head and neck than in the limbs and trunk; the age and weight of children revealed a strong positive correlation with DAP values. The treated patients as a group demonstrated an increase in all three endpoints relative to baseline following IPs. Children with vascular tumors have a higher risk of dicentric chromosome + centric ring (dic+r) and cytokinesis-block micronucleus (CBMN) after IPs than children with vascular malformations. The younger the patient, the greater the risk of CA after IPs. Moreover, rogue cells (RCs) were found in five children (approximately 10%) after IPs, and the rates of dic+r and CBMN were significantly higher than those of other children (Z = -3.576, p < 0.001). These results suggest that there may be some children with VA who are particularly sensitive to IR, but more data and more in-depth experiments will be needed to verify this in the future.

Chromosome Instability in Pony of Esperia Breed Naturally Infected by Intestinal Strongylidae

The Pony of Esperia is an Italian autochthonous horse breed reared in the wild on the Aurunci and Ausoni Mountains. Currently, it is considered an endangered breed, as its population consists of 1623 animals. It is therefore essential to identify all aspects that can improve the management and economy of its breeding, favoring its diffusion. In this paper, the effects of intestinal strongyle infection on the chromosome stability of peripheral blood lymphocytes (PBLs) was evaluated through aneuploidy and chromosome aberration (gap, chromatid and chromosome breaks, and the number of abnormal cells) test. Statistical difference in the mean values of aneuploidy, cells with chromosome abnormalities, and chromosome and chromatid breaks were observed between ponies with high fecal egg counts (eggs per gram > 930) and those with undetectable intestinal strongylosis. The causes of this phenomenon and possible repercussions on the management of Pony of Esperia are discussed in the paper.

The association of three DNA repair genes polymorphisms on the frequency of chromosomal alterations detected by fluorescence in situ hybridization

PURPOSE

Gas station workers (GSWs) are exposed to carcinogenic agents. The aim was to study the association of high somatic chromosome alterations (CAs) rates in the blood of GSWs and the polymorphisms of three genes playing a role in DNA double-strand break repair.

METHODS

This is a cross-sectional study with 114 GSWs and 115 age-matched controls. Cytogenetic analyses, blood exams, medical interviews and genotypes for RAD51/G135C (rs1801320), ATM/P1054R (rs1800057) and CHEK2/T470C (rs17879961) genes were performed.

RESULTS

The CA rate in GSWs was 9.8 CAs/1000 metaphases, and 19.1% of the workers had > 10 CAs per 1000 metaphases (group two). GSWs had decreased levels of monocytes (P = 0.024) in their blood exams. The number of variant alleles of the RAD51/G135C polymorphism was higher in GSWs (P = 0.011) compared to the controls, and were associated with enhanced number of CAs per worker (P = 0.008). No allele variant was found for CHEK2/T470C in this study.

CONCLUSION

The RAD51/G135C polymorphism appears to be related to genome instability in gas station workers. Increasing the knowledge of DNA repair gene variations involved in maintaining genomic stability in GSWs may be crucial for future cancer prevention.

Effects of GSTT1 Genotype on the Detoxification of 1,3-Butadiene Derived Diepoxide and Formation of Promutagenic DNA-DNA Cross-Links in Human Hapmap Cell Lines

Smoking is a leading cause of lung cancer, accounting for 81% of lung cancer cases. Tobacco smoke contains over 5000 compounds, of which more than 70 have been classified as human carcinogens. Of the many tobacco smoke constituents, 1,3-butadiene (BD) has a high cancer risk index due to its tumorigenic potency and its abundance in cigarette smoke. The carcinogenicity of BD has been attributed to the formation of several epoxide metabolites, of which 1,2,3,4-diepoxybutane (DEB) is the most toxic and mutagenic. DEB is formed by two oxidation reactions carried out by cytochrome P450 monooxygenases, mainly CYP2E1. Glutathione-S-transferase theta 1 (GSTT1) facilitates the conjugation of DEB to glutathione as the first step of its detoxification and subsequent elimination via the mercapturic acid pathway. Human biomonitoring studies have revealed a strong association between GSTT1 copy number and urinary concentrations of BD-mercapturic acids, suggesting that it plays an important role in the metabolism of BD. To determine the extent that GSTT1 genotype affects the susceptibility of individuals to the toxic and genotoxic properties of DEB, GSTT1 negative and GSTT1 positive HapMap lymphoblastoid cell lines were treated with DEB, and the extent of apoptosis and micronuclei (MN) formation was assessed. These toxicological end points were compared to the formation of DEB-GSH conjugates and 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) DNA-DNA cross-links. GSTT1 negative cell lines were more sensitive to DEB-induced apoptosis as compared to GSTT1 positive cell lines. Consistent with the protective effect of GSH conjugation against DEB-derived apoptosis, GSTT1 positive cell lines formed significantly more DEB-GSH conjugate than GSTT1 negative cell lines. However, GSTT1 genotype did not affect formation of MN or bis-N7G-BD cross-links. These results indicate that GSTT1 genotype significantly influences BD metabolism and acute toxicity.

In Vitro Determination of Genotoxicity Induced by Brackets Alloys in Cultures of Human Gingival Fibroblasts

Orthodontic brackets release ions that can be reabsorbed in the oral mucosa, potentially causing complications, including cytotoxic effects and mutagenic alterations. The aim was to evaluate the genotoxicity induced by orthodontic appliance alloys in cultures of human gingival fibroblasts by comet assay. Eluates were obtained from the following brackets alloys: EconoLine (SS: stainless steel), MiniMirage (Ni-Ti: nickel-titanium), Nu-Edge (Co-Cr: cobalt-chromium), In-Vu (PC-polycrystals (PC) aluminum oxide), and Monocrystal IZE (monocrystalline (MC) aluminum oxide). Each bracket was sterilized and exposed to a corrosive process for 35 days. The obtained eluates were tested for genotoxicity of human gingival fibroblasts (HGFA) by the alkaline comet assay. All study groups showed genotoxic effects; there was a significant difference (p < 0.0001) among groups. The eluates obtained from Ni-Ti showed a 16-times greater genotoxic effect. There were differences in genotoxicity after comparing the Ni-Ti with SS (p < 0.01) and Co-Cr brackets (p < 0.001). The ceramic was more genotoxic than metallic brackets (SS and Co-Cr), but less than the Ni-Ti. This in vitro model will be useful for further study of early DNA damage caused by brackets and other biomaterials used in the oral cavity before their introduction into the clinical setting.

A systematic review on the genotoxic effect of serotonin and norepinephrine reuptake inhibitors (SNRIs) antidepressants

RATIONALE

Depression is a major mental disorder affecting millions of people worldwide. Serotonin and norepinephrine reuptake inhibitors (SNRIs) are one of the antidepressant drugs prescribed for depression treatment.

OBJECTIVE AND METHOD

There are many contradiction studies about the adverse effect and genotoxicity of SNRIs. So here, based on the guidelines proposed at the PRISMA statement, we performed a quantitative systematic review by searching international electronic databases (PubMed, Scopus, Embase, and Web of Science) for published documents on SSNRIs and their genotoxicity effects.

RESULTS

The database searches retrieved 336 records, 18 of which met the inclusion criteria. Evaluation of the selected articles showed that a total of 9 articles were appropriate for final review. Most of these studies (78%) reported positive results for the genotoxicity of SNRIs CONCLUSION: Finally, we can conclude that these drugs have the potential to damage DNA.

Bulky DNA adduct levels in normal-appearing colon mucosa, and the prevalence of colorectal adenomas

PURPOSE

Examine the association between bulky DNA adduct levels in colon mucosa and colorectal adenoma prevalence, and explore the correlation between adduct levels in leukocytes and colon tissue.

METHODS

Bulky DNA adduct levels were measured using ³²P-postlabelling in biopsies of normal-appearing colon tissue and blood donated by 202 patients. Multivariable logistic regression was used to examine associations between DNA adducts, and interactions of DNA adduct-DNA repair polymorphisms, with the prevalence of colorectal adenomas. Correlation between blood and tissue levels of DNA adducts was evaluated using Spearman's correlation coefficient.

RESULTS

An interaction between bulky DNA adduct levels and XPA rs1800975 on prevalence of colorectal adenoma was observed. Among individuals with lower DNA repair activity, increased DNA adduct levels were associated with increased colorectal adenoma prevalence (OR = 1.41 per SD increase, 95%CI: 0.92-2.18). Conversely, among individuals with normal DNA activity, an inverse association was observed (OR = 0.60 per SD increase, 95%CI: 0.34-1.07). Blood and colon DNA adduct levels were inversely correlated (ρ = -0.20).

CONCLUSIONS

Among genetically susceptible individuals, higher bulky DNA adducts in the colon was associated with the prevalence of colorectal adenomas. The inverse correlation between blood and colon tissue measures demonstrates the importance of quantifying biomarkers in target tissues.

Genetic variation of acquired structural chromosomal aberrations

Human malignancies are often hallmarked with genomic instability, which itself is also considered a causative event in malignant transformation. Genomic instability may manifest itself as genetic changes in the nucleotide sequence of DNA, or as structural or numerical changes of chromosomes. Unrepaired or insufficiently repaired DNA double-strand breaks, as well as telomere shortening, are important contributors in the formation of structural chromosomal aberrations (CAs). In the present review, we discuss potential mechanisms behind the formation of CAs and their relation to cancer. Based on our own studies, we also illustrate how inherited genetic variation may modify the frequency and types of CAs occurring in humans. Recently, we published a series of studies on variations in genes relevant to maintaining genomic integrity, such as those encoding xenobiotic-metabolising enzymes, DNA repair, the tumour suppressor TP53, the spindle assembly checkpoint, and cyclin D1 (CCND1). While individually genetic variation in these genes exerted small modulating effects, in interactions they were associated with CA frequencies in peripheral blood lymphocytes of healthy volunteers. Moreover, we observed opposite associations between the CCND1 splice site polymorphism rs9344 G870A and the frequency of CAs compared to their association with translocation t(11,14). We discuss the functional consequences of the CCND1 gene in interplay with DNA damage response and DNA repair during malignant transformation. Our review summarizes existing evidence that gene variations in relevant cellular pathways modulate the frequency of CAs, predominantly in a complex interaction. More functional/mechanistic studies elucidating these observations are required. Several questions emerge, such as the role of CAs in malignancies with respect to a particular phenotype and heterogeneity, the formation of CAs during the process of malignant transformation, and the formation of CAs in individual types of lymphocytes in relation to the immune response.

Cytokinesis-block micronucleus cytome assay parameters in peripheral blood lymphocytes of the general population: Contribution of age, sex, seasonal variations and lifestyle factors

The cytokinesis-block micronucleus cytome (CBMN Cyt) assay was used to evaluate the baseline frequency of cytogenetic damage in peripheral blood lymphocytes of the general population (average age, 38.28 ± 12.83 years) in relation to age, sex, body mass index, seasonal variations (season of sampling, period of sampling and different meteorological parameters) and lifestyle factors (smoking habit, alcohol consumption, exposure to medications and diagnostic radiation, physical activity, and family history of cancer). The background frequency of micronuclei (MNi) for the 200 subjects assayed was 5.06 ± 3.11 per 1000 binucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 1.21 ± 1.46 and of nuclear buds (NBUDs) 3.48 ± 2.14. The background frequency of apoptosis and necrosis was 1.58 ± 1.50 and 1.39 ± 1.56, respectively, while the mean nuclear division index (NDI) was 1.99 ± 0.14. The cut-off value, which corresponds to the 95th percentile of the distribution of 200 individual values, was 11 MNi, 4 NPBs and 7 NBUDs. The study also confirmed an association of the above mentioned parameters with age, sex and several lifestyle factors. Moreover, significant confounders based on our results are also sampling season, sampling period and different meteorological parameters that were dependent on the CBMN Cyt assay parameters. In line with the above mentioned, several factors should be taken into account when it comes to the monitoring of exposed populations using cytogenetic biomarkers. Moreover, the normal and cut-off values obtained in this study present background data for the general population, and can later serve as baseline values for further biomonitoring studies.

High chromosomal instability in workers occupationally exposed to solvents and paint removers

BACKGROUND

Painters are exposed to an extensive variety of harmful substances like aromatic hydrocarbons used as solvents and paint removers, some of which have shown clastogenic activity. These substances constitute a complex mixture of chemicals which contain well-known genotoxicants, such as Benzene, Toluene and Xylene. Thus, chronic occupational exposure to such substances may be considered to possess genotoxic risk. In Colombia the information available around the genotoxic damage (Chromosomal and DNA damage) in car paint shop workers is limited and the knowledge of this damage could contribute not only to a better understanding of the carcinogenic effect of this kind of substances but also could be used as biomarkers of occupational exposure to genotoxic agents.

RESULTS

In this study, the genotoxic effect of aromatic hydrocarbons was assessed in peripheral blood lymphocytes of 24 workers occupationally exposed and 24 unexposed donors, by using Cytogenetic analysis and comet assay. A high frequency of Chromosomal alterations was found in the exposed group in comparison with those observed in the unexposed group. Among the total of CAs observed in the exposed group, fragilities were most frequently found (100 %), followed by chromosomal breaks (58 %), structural (41.2 %) and numerical chromosomal alterations (21 %). Numerical chromosomal alterations, fragilities and chromosomal breaks showed significant differences between exposed and unexposed groups. Among the fragilities, fra(9)(q12) was the most frequently observed. DNA damage index was also significantly higher in the exposed group compared to the unexposed group (p < 0.000).

CONCLUSIONS

Our results revealed that occupational exposure to aromatic hydrocarbons is significantly associated with Chromosomal and DNA damage in car paint shops workers and are also indicative of high chromosomal instability. The high frequency of both Chromosomal Alterations and DNA Damage Index observed in this study indicates an urgent need of intervention not only to prevent the increased risk of developing cancer but also to the application of strict health control and motivation to the use of appropriate protecting devices during work.

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.

Evaluation of cytogenetic and DNA damage caused by thallium(I) acetate in human blood cells

Although thallium is detrimental to all living organisms, information regarding the mutagenic and genotoxic effects of this element and its compounds remains scarce. Therefore, we tested the genotoxic and cytotoxic effects of thallium(I) acetate on human peripheral blood cells in vitro using structural chromosomal aberrations (SCAs), sister chromatid exchanges (SCEs), and single-cell gel electrophoresis (at pH >13 or 12.1) analysis. Whole blood samples were incubated with 0.5, 1, 5, 10, 50, or 100 µg/mL thallium salt. Exposure to this metal compound resulted in a clear dose-dependent reduction in the mitotic and replicative indices. An increase in SCAs was evident in the treated group compared with the control group, and significant differences were observed in the percentage of cells with SCAs when metaphase cells were treated with 0.5-10 µg/mL of thallium(I). The SCE test did not reveal any significant differences. We observed that a 1-h treatment with thallium(I) at pH > 13 significantly increased the comet length for all the concentrations tested; however, at pH 12.1, only the two highest concentrations affected the comet length. These results suggested that thallium(I) acetate induces cytotoxic, cytostatic, and clastogenic effects, as well as DNA damage.

Induction and repair of DNA damage measured by the comet assay in human T lymphocytes separated by immunomagnetic cell sorting

The comet assay is widely used in human biomonitoring to measure DNA damage in whole blood or isolated peripheral blood mononuclear cells (PBMC) as a marker of exposure to genotoxic agents. Cytogenetic assays with phytohemagglutinin (PHA)-stimulated cultured T lymphocytes are also frequently performed in human biomonitoring. Cytogenetic effects (micronuclei, chromosome aberrations, sister chromatid exchanges) may be induced in vivo but also occur ex vivo during the cultivation of lymphocytes as a consequence of DNA damage present in lymphocytes at the time of sampling. To better understand whether DNA damage measured by the comet assay in PBMC is representative for DNA damage in T cells, we comparatively investigated DNA damage and its repair in PBMC and T cells obtained by immunomagnetic cell sorting. PBMC cultures and T cell cultures were exposed to mutagens with different modes of genotoxic action and DNA damage was measured by the comet assay after the end of a 2h exposure and after 18h post-incubation. The mutagens tested were methyl methanesulfonate (MMS), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), 4-nitroquinoline-1-oxide (4NQO), styrene oxide and potassium bromate. MMS and potassium bromate were also tested by the modified comet assay with formamido pyrimidine glycosylase (FPG) protein. The results indicate that the mutagens tested induce DNA damage in PBMC and T cells in the same range of concentrations and removal of induced DNA lesions occurs to a comparable extent. Based on these results, we conclude that the comet assay with PBMC is suited to predict DNA damage and its removal in T cells.

Multicolour FISH analysis of ionising radiation induced micronucleus formation in human lymphocytes

Micronucleation of chromosomal DNA is an effective indicator of DNA damage and micronucleus (MN) analysis is a valuable tool for radiation biodosimetry studies. To gain a comprehensive knowledge of micronucleation process after ionising radiation (IR) exposure, whole genome-wide chromosome analysis is desirable. With this objective, multicolour fluorescence in situ hybridization (M-FISH) technique was utilised in the present study to characterise the chromosome content of spontaneous and IR-induced micronuclei in three human donors. M-FISH analysis revealed a radiation dose-dependant increase in the number of micronuclei with multi-chromosome material above 2 Gy and as many as 3-6 multicolour signals were detected in micronuclei after high γ-rays radiation doses (5-10 Gy). Involvement of each human chromosome material was more frequently detected in multicoloured micronuclei than in single-coloured micronuclei at high radiation doses (>2 Gy). Observation of dose-dependant increase in the MN frequency with multi-chromosome material may be due to misrepair of DNA double-strand breaks involving multiple chromosomes leading to asymmetric dicentric or ring chromosomes and acentric fragments. Chromosomes belonging to groups A (1, 2 and 3) and B (4 and 5) were frequently detected in 35-45% of the total micronuclei either as single entities or in combination with other chromosomes. Among the A and B groups, chromosome 1 material was consistently detected at high MN frequencies after radiation exposure in all the donors. Additionally, chromosomes 13 and 19 were more frequently observed in micronuclei than the expected frequency based on DNA content. Our whole genome approach utilising the M-FISH technique revealed that MN formation at high radiation doses might be complex involving multiple chromosome fragments. Understanding the fate and biological consequences of these multi-chromosome-containing micronuclei may provide key molecular insights for some aspects of IR-induced genomic instability and cancer development processes.

Assessment of genotoxicity associated with Behcet's disease using sister-chromatid exchange assay: vitamin E versus mitomycin C

Behcet's disease (BD) is a multisystemic chronic inflammatory disorder that presents throughout the world with high frequency in Turkey and Middle East. BD has been shown to be associated with genotoxicity as patients with the disease have demonstrated high rates of sister chromatid exchange (SCE) and oxidative DNA damage. In this study, we examined the effect of vitamin E, which is known for its strong antioxidant activity, on the rate of SCE in cultured lymphocytes obtained from BD patients. In addition, the susceptibility of patient lymphocytes to the mutagenic agent mitomycin C (MMC) was also investigated. The results showed significant elevation in the rate of SCE in lymphocytes obtained from patients compared to those from healthy subjects (P < 0.01). Treatment with vitamin E normalized the elevated rate of SCE to a comparable level observed in the control group (P < 0.01). Finally, treatment of cultures with MMC significantly increased the rate of SCE in the lymphocytes of both patients and controls (P < 0.001). The magnitude of change in the rate of SCE induced by MMC was equivalent in both groups. This result suggests similar sensitivity of BD lymphocytes and control ones to MMC. In conclusion, genotoxicity associated with BD can be overcome by treatment with vitamin E. Lymphocytes of BD have normal sensitivity to the mutagenic agent MMC.

Cytogenetic biomonitoring in oral mucosa cells following dental X-ray

OBJECTIVES

In the past decades, X-rays have been used widely for diagnosis in dentistry. However, it is well known that ionizing radiation causes damage (including single- and double-strand breaks) to deoxyribonucleic acid (DNA) and DNA-protein crosslinks, and induces cellular death. Therefore, outlining the cytogenetic effects induced by X-ray is necessary to identify the degree of cancer risk and minimize potential risks to patients and clinicians. To date, a variety of assays have been proposed in cytogenetic biomonitoring studies, including those that assess metaphase chromosomal aberrations and sister chromatid exchanges, and micronucleus and single-cell gel (comet) assay.

METHODS

Cytogenetic biomonitoring studies focusing on oral mucosa cells in individuals exposed to dental X-ray were reviewed.

RESULTS

Dental X-ray can induce DNA damage and cytotoxicity in oral mucosa cells.

CONCLUSION

These results will contribute to a better understanding of X-ray-induced effects upon the cellular system in individuals continually exposed to known genotoxic/cytotoxic agents.