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Monitoring Air Pollution Impact on Vulnerable Populations Using Buccal Micronucleus Assay

Images of different types of nuclear changes detected in buccal cells

Air pollution remains a critical public health concern, particularly affecting vulnerable populations such as children with asthma. These individuals are more susceptible to the harmful effects of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs), both of which can trigger respiratory issues and other health problems. Recent advancements in biomonitoring have introduced noninvasive methods, such as buccal micronucleus (MN) cytome assays and exhaled breath condensate analysis, to assess the impact of these pollutants on genome integrity and inflammation status.

Buccal Micronucleus Assay: A Tool for Biomonitoring

The buccal MN assay is a pivotal technique used to detect genotoxic effects in the cells lining the oral cavity. As air pollutants are inhaled, they first come into contact with the buccal mucosa, making these cells prime indicators of potential DNA damage. By analysing swabs from the buccal mucosa, researchers can identify various nuclear abnormalities and DNA damage biomarkers. DNA damage in the form of MN correlates also with blood MN, which is a more invasive assay, and therefore less likely to be used in vulnerable populations such as children.

Nuclear Changes Detected by Buccal MN Assay

The buccal MN assay is capable of detecting several types of nuclear changes in buccal cells, including:

  1. Normal Basal Cells: Stem cells of the buccal mucosa that continuously regenerate the tissue.
  2. Normal Differentiated Cells: Mature cells that have undergone differentiation to perform specific functions.
  3. Binucleated Cells: Cells containing two nuclei, which may indicate a disruption in normal cell division.
  4. Cells with Condensed Chromatin (early apoptosis): Cells showing tightly packed chromatin, often a sign of apoptosis or other forms of cell death.
  5. Cells with Karyorrhectic Chromatin (late apoptosis): Cells displaying fragmented or dissolved nuclei, further indicators of cell death.
  6. Pyknotic Cells (early necrosis): Cells exhibiting condensed, shrunken nuclei.
  7. Karyolitic Cells (late necrosis): Cells displaying fragmented or dissolved nuclei, further indicators of cell death.
  8. DNA Damage Biomarkers: Differentiated cells with micronuclei (MN), small, extranuclear bodies indicating chromosomal fragments or whole chromosomes left behind during cell division.
  9. DNA Damage Biomarkers: Differentiated cells with broken eggs nuclei 
  10. DNA Damage Biomarkers: Differentiated cells with nuclei, with nuclear buds, gene amplification indicator. Usually, (i) and (j) are scored together although the origin of both is not well understood due to the limited repair mechanisms in buccal exfoliated cells.

Application to Vulnerable Populations

Children with asthma are particularly at risk from air pollution, making it essential to monitor their exposure and potential biological effects. The buccal MN assay, combined with exhaled breath condensate analysis, provides a comprehensive and noninvasive approach to assess genome integrity and inflammatory responses in these children. Exhaled breath condensate analysis complements the MN assay by evaluating inflammation markers, offering insights into respiratory health and the inflammatory status of the lungs. Together, these methods can help in the early detection of adverse effects, guiding interventions to reduce exposure and improve health outcomes for vulnerable populations.

Other air pollutants and xenobiotics that enter through the mouth can affect the cells, and these effects can be assessed with this assay. This includes environmental and occupational exposures (such as pesticides, herbicides, fertilisers, organic solvents, arsenic, boron, gas stations, antineoplastic drugs, metal exposures like chromium and nickel, welders, miners, battery production, dental technicians, the glass industry, asbestos, fibers, dust, anesthetic gases, formaldehyde, painters, paint production, wood dust, and air pollution), diet and lifestyle factors (such as smoking, alcohol intake, steroid or amphetamine use, dietary folate intake, and ionizing radiation), and disease-related factors (including aerodigestive tract disease, chemo and radiotherapy, chronic renal disease, breast cancer, Down syndrome, Alzheimer's disease, and amyotrophic lateral sclerosis).

Higher DNA damage or specific types of DNA damage in certain diseases can serve as potential early biomarkers. The value of this assay is particularly significant given that over 90% of human cancers originate in epithelial cells. Noninvasive detection of changes in exfoliated buccal cells can provide insight into an individual's genome instability and sensitivity, helping to identify vulnerable populations or individuals. These individuals can then be closely monitored to prevent disease development, reduce cancer risk, or mitigate the progression of the disease or condition severity.

The EDIAQI team members from the Institute for Medical Research and Occupational Health in Zagreb, Croatia, with their vast knowledge and equipped with state-of-the-art facilities, will continue to study the possible impact of air pollutants on genome stability using novel tools such as the buccal micronucleus (MN) cytome assays.

Note: This article has been published on behalf of Mirta Milić, Luka Kazensky & Goran Gajski, Institute for Medical Research and Occupational Health (IMROH), Zagreb, Croatia.


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