Neuroprotective properties of estrogen have poorly translated to reduced neurodegeneration in clinical trials of systemic estrogen replacement therapy. To more directly assess biological processes ass Show more
Neuroprotective properties of estrogen have poorly translated to reduced neurodegeneration in clinical trials of systemic estrogen replacement therapy. To more directly assess biological processes associated with brain estrogen (estrone, estradiol) levels, we recruited 81 women (42 non-white) and 28 men (13 non-white) for cerebrospinal fluid (CSF) hormone, targeted proteomic, and volumetric brain analysis. In the mostly post-menopausal women, we found CSF estrogen levels to only modestly correlate with their corresponding plasma levels, and were additionally influenced by body mass index or age. CSF estrone was also correlated with a marker of Alzheimer’s disease (AD) neuropathologic change (CSF Aβ42/Aβ40), but this was not the case for the more biologically active CSF estradiol. Aptamer-based proteomic analysis of 1,075 CSF markers for inflammation, proteolysis, signaling, and DNA/RNA regulation revealed CSF estrogen levels to associate with alternative complement pathway proteins, and shifts observed in AD (apoE, RAGE). Parallel MRI analysis correlated higher CSF estrogen with smaller volumes of the brain somatosensory and posterior-medial networks without influence from cognition or neurodegeneration. Analysis using plasma estrogens only partially reproduced CSF estrogens’ biochemical correlates but provided inconclusive relationships with brain volume correlates. These findings highlight the association between CSF levels of the more biologically active estradiol and CSF inflammatory pathways involving AD risk genes as potential mechanisms linking hormone status to AD risks, and suggest caution in using CSF estrone or plasma estrogens when interpreting treatment or preventive studies. The online version contains supplementary material available at 10.1186/s12974-025-03657-3. Show less
In mammals, auditory hair cells are generated only during embryonic development and loss or damage to hair cells is permanent. However, in non-mammalian vertebrate species, such as birds, neighboring Show more
In mammals, auditory hair cells are generated only during embryonic development and loss or damage to hair cells is permanent. However, in non-mammalian vertebrate species, such as birds, neighboring glia-like supporting cells regenerate auditory hair cells by both mitotic and non-mitotic mechanisms. Based on work in intact cochlear tissue, it is thought that Notch signaling might restrict supporting cell plasticity in the mammalian cochlea. However, it is unresolved how Notch signaling functions in the hair cell-damaged cochlea and the molecular and cellular changes induced in supporting cells in response to hair cell trauma are poorly understood. Here we show that gentamicin-induced hair cell loss in early postnatal mouse cochlear tissue induces rapid morphological changes in supporting cells, which facilitate the sealing of gaps left by dying hair cells. Moreover, we provide evidence that Notch signaling is active in the hair cell damaged cochlea and identify Hes1, Hey1, Hey2, HeyL, and Sox2 as targets and potential Notch effectors of this hair cell-independent mechanism of Notch signaling. Using Cre/loxP based labeling system we demonstrate that inhibition of Notch signaling with a γ- secretase inhibitor (GSI) results in the trans-differentiation of supporting cells into hair cell-like cells. Moreover, we show that these hair cell-like cells, generated by supporting cells have molecular, cellular, and basic electrophysiological properties similar to immature hair cells rather than supporting cells. Lastly, we show that the vast majority of these newly generated hair cell-like cells express the outer hair cell specific motor protein prestin. Show less