Let-7a MicroRNA Expression in the Mediobasal Hypothalamus during Aging

The hypothalamus is a key integrator of autonomic and endocrine regulation and is also involved in aging mechanisms. It is hypothesized that aging processes may be regulated by changes in microRNA expression in the mediobasal hypothalamus. The aim of the study was to determine the localization and percentage of cells in the arcuate (ARN), dorsomedial (DMN), and ventromedial (VMN) nuclei of the hypothalamus expressing let-7a microRNA in male rats aged 2 months (young), 12 months (adult), and 24 months (aged) using fluorescence in situ hybridization. The results indicate that in the ARN and DMN, the percentage of let-7a microRNA-positive neurons did not differ significantly between young and adult rats, but decreased in the ARN from 51.7 ± 3.8 to 34.7 ± 4.2% and in the DMN from 35.8 ± 3.3 to 27.2 ± 3.6% in adult rats relative to old animals. The highest percentage of neurons expressing let-7a microRNA in all animals studied was observed in the VMN compared to the ARN and DMN. However, in the VMN, the percentage of neurons expressing let-7a during ontogenesis did not change significantly with aging.