Exploring Telomere Dynamics in Aging Male Rat Tissues: Can Tissue-Specific Differences Contribute to Age-Associated Pathologies?

<b><i>Introduction:</i></b> Due to increasing lifespan, global aging rates are rising rapidly and age-associated diseases are increasing. To ensure that health span is concomitant with life span, a greater understanding of cellular mechanisms of aging is important. <b><i>Methods:</i></b> Telomere length analysis from a wide range of tissues from weaning, young adult, and middle-aged (3, 12 and 52 week) male Wistar rats were conducted using Southern blotting. Telomere lengths were compared between tissues and ages using regression models based on the ratios of longest-to-shortest telomere fragments. <b><i>Results:</i></b> Robust linear age-dependent telomere attrition was observed in the liver; 3 versus 12 weeks, 3 versus 52 weeks (<i>p</i> &#x3c; 0.01), 12 versus 52 weeks (<i>p</i> &#x3c; 0.05) and the heart; 3 versus 12 weeks (<i>p</i> &#x3c; 0.05) and 3 versus 52 weeks (<i>p</i> &#x3c; 0.001). More subtle shortening was observed in aorta and epididymal fat; 3 and 12 versus 52 weeks (<i>p</i> &#x3c; 0.001) and in skeletal muscle; 3 versus 52 weeks (<i>p</i> &#x3c; 0.05), 12 versus 52 weeks (<i>p</i> &#x3c; 0.01). Young thymus telomeres increased in length (3 vs. 12 weeks) and then shortened between 12 and 52 weeks (<i>p</i> &#x3c; 0.001). We also reported disparity in telomere shortening within tissues: telomeres in aging brain cortex significantly shortened; 3 versus 52 weeks (<i>p</i> &#x3c; 0.05), 12 versus 52 weeks (<i>p</i> &#x3c; 0.01). This was not seen in the hypothalamic region. A robust stepwise shortening was observed in the renal cortex; 3 versus 12 weeks, 12 versus 52 weeks (<i>p</i> &#x3c; 0.05), and 3 versus 52 weeks (<i>p</i> &#x3c; 0.001), which was not as apparent in the renal medulla; 3 versus 12 weeks (<i>p</i> &#x3c; 0.01) and 3 versus 52 weeks (<i>p</i> &#x3c; 0.01). The vastus lateralis skeletal muscle demonstrated the shortest telomere length at weaning and underwent robust age-associated attrition; 3 versus 52 weeks (<i>p</i> &#x3c; 0.05), 12 versus 52 weeks (<i>p</i> &#x3c; 0.01). We demonstrated that specific tissues exhibit unique telomere attrition profiles which may partially explain why certain diseases are more prevalent in aged individuals. <b><i>Discussion/Conclusion:</i></b> We show wide variations between tissues in vulnerability to the aging process. In the future, this may help target potential interventions to improve health span.