Electrical impedance spectroscopy of young and old mouse multiple tissues.

Characterizing age-related changes in the passive electrical properties of biological tissues is important for understanding tissue aging and developing biophysical assessment strategies. Electrical impedance spectroscopy (EIS) serves as a robust tool for characterizing tissue electrical properties. However, the systematic and quantitative effects of age and frequency on complex impedance parameters-such as magnitude (Z), resistance (R), and reactance (X)-across multiple tissues remain inadequately explored. In this study, we applied EIS to systematically profile the complex impedance spectra of ten major tissues from 2- to 18 month-old male and female mice, including skin, brain, spleen, heart, lung, liver, kidney, muscle, testis, and adipose tissue, over a frequency range of 20 Hz to 1 MHz. Our results indicate that aging significantly alters key impedance parameters (Z, R, andX) of skin, muscle, adipose, and liver tissue in a frequency-dependent manner, whereas other tissues exhibited minimal age-related changes. Using nonlinear least-squares regression, we performed an exploratory fitting analysis to elucidate the relationships among frequency, age, and impedance parameters under the currentex vivomeasurement conditions. The resulting fitting equations served as empirical descriptors of the observed impedance spectra. This study quantitatively reveals the substantial impact of age and frequency on impedance parameters in specific tissues, offering novel insights into the bioimpedance characteristics linked to tissue aging. Furthermore, it underscores the potential of EIS as a rapidex vivobiophysical approach for characterizing tissue-specific bioimpedance alterations associated with aging.