Telomere shortening during aging of human osteoblasts in vitro and leukocytes in vivo: lack of excessive telomere loss in osteoporotic patients

We have compared the telomere length, as assessed by Southern analysis, of telomere restriction fragments (TRFs) generated by RsaI/HinfI digestion of genomic DNA in: (i) in vitro cultured human trabecular osteoblasts undergoi ng cellular aging; and (ii) peripheral blood leukocytes (PBL) obtained from three groups of women: young (aged 20-26 years, n = 15), elderly (aged 48- 85 years, n = 15) and osteoporotic (aged 52-81 years, n = 14). The mean TRF length in human osteoblasts undergoing aging in vitro decreased from an av erage of 9.32 kilobasepairs (kb) in middle-aged cells to an average of 7.80 kb in old cells. The rate of TRF shortening was about 100 bp per populatio n doubling, which is similar to what has been reported for other cell types , such as human fibroblasts. Furthermore, there was a 30% decline in the to tal amount of telomeric DNA in senescent osteoblasts as compared with young cells. In the case of PBL, TRF length in the DNA extracted from young wome n was slightly longer (6.76 +/- 0.64 kb) than that from a group of elderly women (6.42 +/- 0.71 kb). A comparison of TRFs in the DNA extracted from th e PBL from osteoporotic patients and from age-matched controls did not show any significant differences (6.47 +/- 0.94 versus 6.42 +/- 0.71 kb, respec tively). Therefore, using TRF length as a marker for cellular aging in vitr o and in vivo, our data comparing TRFs from osteoporotic patients and age-m atched controls do not support the notion of the occurrence of a generalize d premature cellular aging in osteoporotic patients. (C) 1999 Elsevier Scie nce Ireland Ltd. All rights reserved.