Aging is Associated with Sex-Specific Alteration in the Expression of Genes Encoding for Neuroestradiol Synthesis and Signaling Proteins in the Mouse Trigeminal Somatosensory Input.

Pain perception is influenced by sex and aging, with previous studies indicating the involvement of aromatase, the estradiol synthase enzyme, in regulating pain perception. Previous research has established the presence of aromatase in dorsal root ganglia sensory neurons and its role in modulating pain perception. The present study aims to explore the implications of aging and sex on the expression of aromatase and estrogen receptors in the trigeminal ganglion. The study examined mRNA levels of aromatase, ERs, and the androgen receptor (AR) in the trigeminal ganglion of 3-month-old and 27-month-old male and female mice, as well as 3-month-old mice from the four-core genotype (FCG) transgenic model. The latter facilitates the assessment of gonadal hormone and sex chromosome implications for sex-specific traits. Aromatase localization in the ganglion was further assessed through immunohistochemistry. Aromatase immunoreactivity was observed for the first time in sensory neurons within the trigeminal ganglion. Trigeminal ganglion gene expressions were detected for aromatase, ERs, and AR in both sexes. Aromatase, ERβ, and GPER gene expressions were higher in young males versus young females. Analyses of the FCG model indicated that sex differences depended solely on gonadal sex. The aging process induced an enhancement in the expression of aromatase, ERs, and AR genes across both sexes, culminating in a reversal of the previously observed gender-based differences. the potential impact of estrogen synthesis and signaling in the trigeminal ganglion on age and sex differences warrants consideration, particularly in relation to trigeminal sensory functions and pain perception. Age and gonadal sex influence ERs, AR, and ARO levels in the trigeminal ganglion. Although somatosensory perception shows a decline in the elderly, the incidence of trigeminal neuralgia intensifies in aged adults and is predominantly prevalent in women relative to men. The increased expression of aromatase and estrogen receptors in aged female animals suggests that the modulatory influence that neuroestradiol exerts over the trigeminal somatosensory input, inclusive of pain, undergoes changes in elderly male and female individuals in a sex-specific manner.