Progressive telomere shortening with aging was studied in the normal liver tissue of 94 human subjects aged between 0 and 101 years old to determine the rate of telomere loss in 1 year. Telomere length demonstrated accelerated shortening with reduction of 55 base pairs (bp) per year. The mean telomere length in five neonates was 12.9 +/- 2.6 kilobase pairs (kbp), and that in one centenarian was 8.3 kbp. Mean telomere lengths by age group were 13.2 +/- 2.0 kbp (< or = 8 years; 10 subjects), 7.8 +/- 1.9 kbp (40-79 years; 29 subjects), and 7.5 +/- 2.0 kbp (> or = 80 years; 53 subjects), with reduction thus appearing to show slowing on the attainment of middle age. The difference of mean telomere lengths for two groups with or without advanced malignancies of other than liver origin was not significant in the older two groups. Despite the slow turnover of liver tissue, the overall reduction rate of telomere length decrease in 1 year was almost the same as that of digestive tract mucosa, with its very rapid renewal.
We investigated progressive telomere shortening in normal human epidermis and lingual epithelium during aging, and attempted, in particular, to ascertain whether the telomere shortening that accompanies aging occurs at the same rate in different tissues. We studied telomeric DNA integrity, and estimated annual telomere loss, in 52 specimens of epidermis and 48 specimens of lingual epithelium collected at autopsy from subjects who had died at ages between 0 and 101 y. Most of the DNA samples were measured twice by southern blot hybridization. In addition, the correlation between telomere lengths in the two types of tissues was examined. The telomere reduction rates in epidermis and lingual epithelium were 36 bp and 30 bp per y, respectively, and these were significantly different. The rates obtained by the second measurements in epidermis and lingual epithelium were 39 and 32 bp per y, respectively, and these were also significantly different. The mean telomere lengths in the epidermis of eight neonates and the lingual epithelium of seven neonates were 13.2+/-1.0 and 13.8+/-1.0 kb, respectively. Comparison of telomere lengths in the two tissues for 41 paired samples showed that the mean telomere length in the epidermis (10.7+/-2.3 kb) was less than that in the lingual epithelium (12.4+/-2.5 kb); however, statistical analysis revealed a very significant relationship between epidermal and lingual epithelial telomere length (r=0.842, p<0.0001). These results indicate that the telomeres in epidermis and lingual epithelium are characterized by tissue-specific loss rates.
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