The expression of the Ink4a/Arf locus, which encodes tumor suppressor proteins p16INK4a and Arf, increases with aging in most rodent tissues. This increase is restricted to specific cell compartments within each organ and occurs in both epithelial and stromal cells. Caloric restriction reduces this age-related increase in Ink4a/Arf expression in the kidney, ovary, and heart, correlating with reduced senescence markers and pathology. The age-related increase in Ink4a/Arf expression is attributed to the transcriptional activator Ets-1 and unknown coregulatory molecules. These findings suggest that Ink4a/Arf expression is a robust biomarker of mammalian aging. The study also shows that Ink4a/Arf expression is closely linked to cellular senescence, with increased expression in tissues such as the kidney, ovary, and testis. Caloric restriction reduces Ink4a/Arf expression in several tissues, including the kidney, and is associated with decreased disease states like nephritis. The expression of Ink4a/Arf is strongly correlated with Ets-1 expression, indicating a significant role of Ets-1 in regulating p16INK4a expression with aging. The study also highlights the importance of Ink4a/Arf in aging, suggesting that its expression is not merely a biomarker but also an effector of aging. The results indicate that Ink4a/Arf expression can be used as a clinical marker for aging, as it is a robust and measurable indicator of physiological age. The study provides evidence that Ink4a/Arf expression is a key factor in the aging process and its regulation by various factors such as caloric restriction and genetic mutations. The findings have implications for understanding the molecular mechanisms of aging and could lead to new therapeutic strategies for age-related diseases.The expression of the Ink4a/Arf locus, which encodes tumor suppressor proteins p16INK4a and Arf, increases with aging in most rodent tissues. This increase is restricted to specific cell compartments within each organ and occurs in both epithelial and stromal cells. Caloric restriction reduces this age-related increase in Ink4a/Arf expression in the kidney, ovary, and heart, correlating with reduced senescence markers and pathology. The age-related increase in Ink4a/Arf expression is attributed to the transcriptional activator Ets-1 and unknown coregulatory molecules. These findings suggest that Ink4a/Arf expression is a robust biomarker of mammalian aging. The study also shows that Ink4a/Arf expression is closely linked to cellular senescence, with increased expression in tissues such as the kidney, ovary, and testis. Caloric restriction reduces Ink4a/Arf expression in several tissues, including the kidney, and is associated with decreased disease states like nephritis. The expression of Ink4a/Arf is strongly correlated with Ets-1 expression, indicating a significant role of Ets-1 in regulating p16INK4a expression with aging. The study also highlights the importance of Ink4a/Arf in aging, suggesting that its expression is not merely a biomarker but also an effector of aging. The results indicate that Ink4a/Arf expression can be used as a clinical marker for aging, as it is a robust and measurable indicator of physiological age. The study provides evidence that Ink4a/Arf expression is a key factor in the aging process and its regulation by various factors such as caloric restriction and genetic mutations. The findings have implications for understanding the molecular mechanisms of aging and could lead to new therapeutic strategies for age-related diseases.