Kieffer, A. C. | Search bioRxiv

bioRxiv2026

Reproducible transversal mouse brain sections using low-cost 3D printable resin matrix

Rodent brain matrices that produce coronal or sagittal brain sections for histology confer reproducibility and enable high throughput processing of tissues. However, a stainless steel or acrylic brain matrix that produces tissue sections in a transversal (or horizontal) orientation is currently unavailable as a standard tool. This limits the direct comparison of bilateral brain hemispheres within a single histological section, as freehand trimming to obtain horizontal planes is not easily replicable across samples. To mitigate this challenge, we designed a low-cost (USD 7 per unit), 3D-printed resin-based transverse brain matrix that accommodates mouse brains ranging from 12 to 16 mm in length from the olfactory bulb to the brainstem. Our matrix reproducibly generates horizontal tissue sections with a minimum of 1-mm-thickness without causing visible tissue deformation, which is comparable to the performance of commercial rodent brain matrices. Users may adapt the accompanying CAD code using our video tutorials to customize the transverse brain matrix for their specific needs, including alternative brain size, shape, and tissue thickness.

neuroscience↗

bioRxiv2026

Spatiotemporal Characterization of Amyloidosis-Associated Microglial States Reveals Sex Difference in Early Plaque Formation

Twice as many women develop Alzheimer's disease (AD) compared to men. Several key aspects, such as genetic risk factors, hormonal vulnerability, social responsibilities, and differences in longevity, contribute to the strong female bias in AD. To assess whether sex differences can be detected during the onset of AD, we examined the amyloid-{beta} (A{beta}) plaque burden--one of the hallmarks of AD--and microglial states in young 5XFAD mouse models of amyloid pathology. We hypothesized that an elevated A{beta} burden will directly correlate with an increase in microglial cell number and phagocytic activity, shaping the appearance of compact dense-core plaques in the cortex from 2 to 6 months of age. As expected, no change in microglial density and phenotype was found in A{beta} plaque-free hypothalamus of 5XFAD male and female mice when compared to age-matched wildtype controls. By quantifying the number and coverage of diffuse and dense-core plaques in the cortex, we discovered a pronounced increase in A{beta} plaques and microglial clustering in 4-month-old female 5XFAD compared to male mice. Conversely by 6 months, higher total plaque load in males and no sex difference in the number of plaque-associated microglial (PAM) cluster was observed. Our spatiotemporal characterization of microglial CD68, Dectin-1 (Clec7a), and CD11c (Itgax) expression revealed transient sex differences in the upregulation of only CD68 among these phagocytic markers in cortical microglia. In 4-months-old males, greater phagolysosomal activity may benefit A{beta} clearance and delay plaque formation. In females, lower microglial phagolysosomal activity and increased microgliosis may have led to the increase in plaque deposition and compaction from 2-4 months. Our results suggest that during early amyloidosis, sex differences in CD68-associated phagolysosomal activity and microglia-driven plaque compaction may cause disproportionate AD risk and severity that is compounded by other exacerbating factors during aging. Taken together, sex-specific targeting of microglial proliferation and phagocytic activity may be a promising intervention in presymptomatic patients with known AD risks.

neuroscience↗