Different rate of chromosome breakage in human fibroblast strains after storage in liquid nitrogen.

Cytogenetic investigation was carried out on fibroblasts stored in liquid nitrogen during a period of 7-99 months. Cell strains were from 9 individuals, 2 of whom were affected by xeroderma pigmentosum group C (XPC), and 2 XPC heterozygotes. In cell samples from 3 normal subjects and from 1 patient, high frequencies of abnormal mitoses were observed at the first passage after thawing, which returned to normal values after a few subcultures. The most frequent lesions were chromosome gaps and breaks. The cells damaged the most were those from one XP patient. These findings indicate that cells from some individuals are hypersensitive to clastogenic factors acting during freezing and thawing procedures. This sensitivity could be related to the genetic constitution, although the XP homozygous condition is not an essential or sufficient factor.