We aimed to study the karyotype structure of human adult stem cells after X-ray irradiation. Cultured endometrial mesenchymal stem cells (eMSC) isolated from desquamated endometrium of menstrual blood of the healthy woman were the object of this research. The eMSC at the 9^th passage were irradiated with the sublethal X-ray dose (5Gy). Irradiated cells were cultivated under standard conditions and, at the 13^th passage, they underwent to the karyotyping assay with the G-banding technique. The cytogenetic analysis revealed that the progeny of irradiated cells exhibited genetic instability. Most of analyzed cells had chromosomal abnormalities. Karyotypic changes were manifested mostly as aneuploidy and near-centromeric and other breaks. Within a particular karyotype, various chromosomes may be involved in breaks. Chromosome 1, 4 and X were not involved in chromosomal rearrangements randomly. About 80% of the control not irradiated eMSC metaphase plates had the standard karyotype at the same 13^th passage. Deviations from the normal karyotype were random. Chromosomal breaks were not observed. Our findings show that sublethal X-ray irradiation of eMSC resulted in multiple disorders of the genetic apparatus at the karyotype level. The cells that survived irradiation entered replicative senescence and avoided immortalization or transformation.

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