Mitotic index maximization with no effect on radiation-induced dicentric chromosome frequency
Creators: name: Takebayashi, Kai
name: Echizenya, Keito
name: Kameya, Yuki
name: Nakajima, Daichi
name: Nakayama, Ryo
name: Fujishima, Yohei
name: Goh, Valerie Swee Ting
name: Abe, Yu
name: Kasai, Kosuke
name: Anderson, Donovan A.
name: Blakely, William F.
name: Miura, Tomisato
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Biophysics
subject: 29999 Physical Sciences not elsewhere classified
subject: FOS: Physical sciences
subject: Medicine
subject: Microbiology
subject: FOS: Biological sciences
subject: Cell Biology
subject: Genetics
subject: Molecular Biology
subject: Physiology
subject: Pharmacology
subject: 69999 Biological Sciences not elsewhere classified
subject: Marine Biology
subject: Cancer
subject: Hematology
subject: Plant Biology
subject: 60506 Virology

description: The dicentric chromosome (Dic) assay, which is the gold standard for biological dose assessment in radiation emergency medicine, requires an analysis of at least 500 lymphocyte metaphases or 100 Dic aberrations. Therefore, peripheral blood culture conditions able to obtain metaphases with high frequency for efficient dose evaluation should be optimized. However, the type of blood cultures (i.e., whole blood (WB) or isolated peripheral blood mononuclear cell (PBMC)-culture) and blood volume differ between biodosimetry laboratories. The purpose of this study is to investigate the blood volume at which a high mitotic index is obtained in peripheral whole blood (WB)-culture and isolated peripheral blood mononuclear cell (PBMC)-culture, and to examine the possible effect of blood volume on radiation-induced Dic frequency. Peripheral blood was collected from three healthy donors with their informed consent. The complete and differential blood counts were performed using an automated hematology analyzer. After blood count, peripheral blood was irradiated with 0 or 2 Gy X-ray. Blood was cultured with phytohemagglutinin (180 µg/ml) and demecolcine (0.05 µg/ml) for 48 hrs. The mitotic index (MI) and Dic frequency were analyzed in 5, 10, 15, 20, 25, and 30% WB-cultures and 0.6, 1.2, 1.8, 2.4, 3.0, 3.6-, and 4.2-ml WB-equivalent PBMC-cultures. In WB-culture, MI showed the highest value (∼22%) in 5-15% WB-culture and then gradually decreased to ∼9% with 30% WB-culture. In PBMC-culture, MI peaked (∼ 36 and 31%) at 1.8 mL and 2.4 mL-WB equivalent volumes, respectively, and MI progressively decreased by ∼30% as the amount of PBMCs increased. Although individual differences were observed in the MI values among the three subjects, all the subjects showed the same tendency and higher MI was seen in PBMC- than WB-cultures. However, none of the factors has a significant impact on the yield of Dics. In all culture conditions, the estimated dose calculated based on the Dic frequency was equivalent to the absorbed dose of <i>ex vivo</i> X-ray irradiated blood. While MI was affected by the blood culture type and the volume of cultured blood, Dic yield did not differ significantly between these conditions. These results could be used by relevant laboratories to optimize MI in certain circumstances.