P2-032: Three-dimensional telomere analysis in Alzheimer's disease (AD)

Telomeres are linear TTAGGG repeats capping human chromosomes maintaining chromosomal integrity. Telomeres shorten progressively with each cell division and with age. The aims of our study was to analyze the three-dimensional (3D) architecture of telomeres in AD patients compared to age-matched normal controls in cells obtained from buccal swaps. 3D analysis allows for quantification of telomere numbers, length and aggregates. Buccal swaps were chosen because cells derive from the neuroectoderm from which brain tissue also originates, and they can be collected non-invasively. Twenty six patients with AD diagnosed and staged by standard procedures (mild = 14, moderate = 7, and severe = 6) and 26 cognitively normal age-matched controls were included in the study. Cells were obtained from buccal swaps using sterile Epicentre Biotechnologies swabs, smeared on VWR micro slides and frozen at -20° C. Quantitative fluorescence in situ hybridization (Q-FISH) technique was used for telomere numbers and length analysis in 30 interphase cells/person. Digital images were taken using Zeiss AxioImager Z1 with a cooled AxioCam HR B&W, DAPI, Cy3 filters in combination with a Planapo 63x/1.4 oil objective lens. Images were acquired by using AXIOVISION 4.8 (Zeiss) in multichannel mode followed by constrained iterative deconvolution. For every fluorochrome, 120 images stacks were acquired with a sampling distance of 200 nm along the z, and 102 nm in the XY axis. Quantitation of 3D nuclear telomeric signals was performed using TeloView. Differences in telomere intensity between AD patients and normal controls, were analyzed by Fisher exact test (number of telomeres) and Chi-Square (telomere length). Patients with mild to severe AD had significantly less number of telomeres and shorter telomeres than the control subjects (range from P