Sustained telomere length in hepatocytes and cholangiocytes with increasing age in normal liver

Abstract

Telomeres, a validated biomarker of aging, comprise multiple nucleotide repeats capping chromosomes that shorten with each cell cycle until a critical length is achieved, precipitating cell senescence. Only two previous studies focused on the effect of aging in ''normal'' liver tissue, but these studies were compromised by small sample size, limited age range, tissue derived from individuals with an increased risk of senescence, and the use of liver homogenates. We developed a robust large-volume, four-color quantitative fluorescent in situ hybridization technique to measure telomere length in large numbers of hepatocytes, Kupffer cells, hepatic stellate cells, CD4-positive and CD8-positive lymphocytes, and cholangiocytes. Following validation against the gold standard (Southern blotting), the technique was applied to normal archived paraffin-embedded liver tissue obtained following reperfusion of implanted donor liver. We studied 73 highly selected donors aged 5-79 years with a short medical illness preceding death and no history of liver disease, reperfusion injury, or steatosis and normal graft function 1-year posttransplantation. Cholangiocytes had significantly longer telomeres compared with all other intrahepatic lineages over a wide age range (P < 0.05). Age-related telomere attrition was restricted to sinusoidal cells (i.e., Kupffer cells [P 5 0.0054] and stellate cells [P 5 0.0001]). Cholangiocytes and hepatocytes showed no age-related telomere shortening. Conclusion: In normal liver and over a broad age range, cholangiocytes have longer telomeres than all other intrahepatic lineages. Age-related telomere length decline is restricted to Kupffer cells and stellate cells. (HEPATOLOGY 2012;56:1510-1520

Cellular senescence drives age-dependent hepatic steatosis

“…However, the mechanisms are not yet completely understood, and in some cases, senescence has been associated with detrimental effects but in others it is not. For instance, telomere dysfunction, a major driver of hepatocyte senescence, has been shown to impair liver regeneration and induce liver cirrhosis in mice36 but was not significantly changed during ageing in the human liver37 and did not predict NAFLD32. Furthermore, chronic inflammation has been reported to drive hepatocyte senescence and contribute to liver fibrosis18 and HCC38.…”

Aging and liver disease

“…Although the number of desmin-positive HSCs goes up with aging, the number of α-smooth muscle actin (SMA)-positive HSCs is observed to maintain the same level [24]. Meanwhile, a recent study analyzing the lengths of telomeres in 73 donors has reported that aging-induced decrease in the length of telomeres was limited only to the ones in Kupffer cells and HSCs, and the length of telomeres in cholangiocytes and hepatocytes was not reduced [25]. …”

Hepatocyte senescence predicts progression in non-alcohol-related fatty liver disease

“…Nuclear area and telomere intensity (a surrogate marker of telomere length) of hepatocytes were assessed using Q-FISH, as previously described in detail [23]. Hepatocytes were identified using unconjugated mouse monoclonal anti-Hepar-1 (Dako, concentration 1:100).…”