Vomeronasal organ condition in 5XFAD Alzheimer mouse model: preliminary results of a histological study

The vomeronasal organ (VNO) plays a crucial role in chemical cues detection and animal behaviour. Recent studies revealed that this organ can be affected by degenerative changes induced by natural and pathological aging in mice, strongly affecting the vomeronasal sensory epithelium (VNSE) and reducing semiochemicals detection. Since the Alzheimer’s disease (AD) induces olfaction deficits, the aim of this study was to evaluate if also the VNO can be affected by cellular changes in a commonly used AD mouse model, the 5XFAD. The protocol was approved by the Italian Ministry of Health (authorization n. 406/2021-PR of the 04/06/2021) and involved 48 VNOs from 24 5XFAD mice and 36 VNOs from 18 wild type mice, which were submitted to histological analysis (hematoxylin-eosin and PAS stain) to assess the presence of VNSE vacuolization and degeneration, VNSE thickness and glycogen accumulation. The statistical analysis revealed that no differences were observed between the two groups concerning the presence of vacuolization (MOLR, p=0.79) and degenerative changes (MOLR, p=0.22) of the VNSE. In WT and in 5XFAD mice, VNSE mean thickness was 103,18 µm (±17,61) and 103,69 µm (±10,19), respectively, with no statistical difference among the two genotypes (GLMM, p=0.9). Similarly, glycogen accumulation, assessed on PAS-stained sections, did not differ among groups (GLMM, p=0,12). Interestingly, also WT mice presented higher VNSE degeneration levels than our previous studies in mice of different strains of similar age. These preliminary results seem to suggest that the pathological aging induced in the 5XFAD AD mouse model does not affect the condition of the VNSE compared to WT, as we previously observed in natural aging. Finally, VNSE conditions of the WT mice suggest that the choice of the model is a crucial stage in semiochemical research, since it is possible that the strain can influence the condition, and possibly the functionality, of the VNO.