Parental origin of transgene modulates amyloid-β plaque burden in the 5xFAD mouse model of Alzheimer's disease

Experimental modeling of Alzheimer's disease: Translational lessons from cross-taxon analyses

Alzheimer's disease (AD) is a severely debilitating neurodegenerative disease with a rapidly increasing global prevalence, poorly understood causes, and no efficient treatments. Experimental models are valuable for studying AD pathogenesis, including amyloid beta and tau accumulation, synaptic dysfunction, and neuroinflammation. While no model fully reproduces the disease, we take an evolutionary biology approach to discuss available models across taxa, from mammals (rodents, primates) to zebrafish, Drosophila melanogaster, and Caenorhabditis elegans. Evaluating their strengths and limitations provides insight into disease mechanisms and may refine research strategies for improved diagnostics and therapeutic screening. Traditional models have significantly contributed to AD research, yet their translational limitations highlight the need for physiologically relevant alternatives. Integrating humanized rodent models, zebrafish, organoids, and induced pluripotent stem cell-based systems-along with advances in bioengineering and genetic editing-may offer a more comprehensive framework to bridge the gap between preclinical research and clinical application. HIGHLIGHTS: Experimental models across rodents, primates, zebrafish, fruit flies, and worms provide key insights into Alzheimer's disease (AD). Cross-taxon comparisons assess strengths and weaknesses in AD models. Evolutionary biology approaches refine experimental strategies for AD research. Diverse animal models improve understanding of AD pathogenesis. Cross-species models enhance diagnostics and therapeutic strategy development.

Targeting CD38 immunometabolic checkpoint improves metabolic fitness and cognition in a mouse model of Alzheimer's disease

Protective immunity, essential for brain maintenance and repair, may be compromised in Alzheimer's disease (AD). Here, using high-dimensional single-cell mass cytometry, we find a unique immunometabolic signature in circulating CD4+ T cells preceding symptom onset in individuals with familial AD, featured by the elevation of CD38 expression. Using female 5xFAD mice, a mouse model of AD, we show that treatment with an antibody directed to CD38 leads to restored metabolic fitness, improved cognitive performance, and attenuated local neuroinflammation. Comprehensive profiling across distinct immunological niches in 5xFAD mice, reveals a high level of disease-associated CD4+ T cells that produce IL-17A in the dural meninges, previously linked to cognitive decline. Targeting CD38 leads to abrogation of meningeal TH17 immunity and cortical IL-1β, breaking the negative feedback loop between these two compartments. Taken together, the present findings suggest CD38 as an immunometabolic checkpoint that could be adopted as a pre-symptomatic biomarker for early diagnosis of AD, and might also be therapeutically targeted alone or in combination with other immunotherapies for disease modification.

Novel Approaches to Track Neurodegeneration in Murine Models of Alzheimer's Disease Reveal Previously Unknown Aspects of Extracellular Aggregate Deposition

This paper describes a novel transgenic-based platform to track degeneration of specific populations of neurons in 5xFAD mice, a murine model of Alzheimer's disease. We created a new double transgenic model by crossing 5xFAD mice with Rosa tdT reporter mice. 5xFAD +/- /Rosa tdT mice received intra-spinal cord injections of AAV-retrograde (rg)/Cre at 2-3 months of age to permanently label corticospinal neurons (CSNs). Brains and spinal cords were retrieved 2-3 weeks post-injection or at 12-14 months of age. Immunohistochemical studies of transgene expression throughout the brain and spinal cord, using an antibody selective for hAPP, revealed age-dependent accumulation of hAPP in extracellular aggregates in regions containing hAPP expressing neuronal cell bodies and in regions containing axons and synaptic terminals from hAPP expressing neurons. Permanent labeling of CSNs with tdT confirmed extensive loss of CSNs in old mice. Surprisingly, we discovered that tdT expressed by CSNs accumulated in extracellular aggregates that persisted after the neurons that expressed tdT degenerated. Extracellular aggregates of tdT also contained hAPP and co-localized with other markers of AD pathology. Overall, deposition of hAPP in extracellular aggregates in areas containing axons and synaptic terminals from hAPP expressing neurons is a prominent feature of AD pathophysiology in 5xFAD mice. In addition, accumulation of hAPP and reporter proteins in extracellular aggregates provides a secondary measure to track neurodegeneration of identified populations of neurons in these mice.

Highlights

Characterization of a new double transgenic strain allowing Cre-dependent labeling of populations of neurons that degenerate in 5xFAD mice.Selective labeling of layer V corticospinal neurons (CSNs) via retrograde transduction with AAV-rg allows quantification of previously un-recognized aspects of age-dependent CSN degeneration.Age-dependent deposition of extracellular hAPP by axons and synaptic terminals revealed by immunohistochemistry for mutant human APP in 5xFAD micePetal-shaped clusters of hAPP originate mainly due to axonal degeneration and fragmentation.Surprisingly, tdTomato expressed by neurons that degenerate, persists in extracellular deposits that co-localize with extracellular deposits of hAPP.