Regular re-characterization of the phenotype of preclinical in vivo models is an essential prerequisite for high-quality efficacy studies of new drug candidates. It assures that genetically modified models are not affected by a genetic drift that can alter the model’s phenotype. Such genetic drift could cause a change in the temporal appearance of symptoms or in worst cases even a total loss of symptoms. To prevent such scenarios, Scantox Neuro not only applies highest breeding standards for its genetically modified rodent models but also re-characterizes them on a regular basis as part of R&D efforts.
The latest re-characterization of the well-known Line 61 mouse model of Parkinson’s disease validates a stable high expression of α-synuclein and phosphorylated α-synuclein in the cortex and hippocampus of Line 61 mice as early as 2 months of age (Figure 1). Similar results were found in the caudate putamen of Line 61 mice (data not shown).
Figure 1: Quantification of immunoreactive area of human α-synuclein and phosphorylated α-synuclein in Line 61 mice. Immunoreactive (IR) area of human α-synuclein (A, B) and phosphorylated α-synuclein (C, D) labeling in the cortex (A, C) and hippocampus (B, D) of Line 61 mice compared to non-transgenic (ntg) littermates at the age of 2 and 6 months. Line 61: n = 8, ntg: n = 4. Mean ± SEM. Two-way ANOVA with Bonferroni’s post hoc test. ***p <0.001.
Additional analyses of inflammatory processes by quantification of Iba1 and GFAP as markers of activated microglia and astrocytosis, respectively, validates that Line 61 mice do not present neuroinflammation in the cortex and hippocampus of young and older animals (Figure 2). Neuroinflammation was also absent from the caudate putamen, although previous data might have suggested some minor neuroinflammatory processes in this brain region (data not shown).
Figure 2: Quantification of immunoreactive area of Iba1 and GFAP in Line 61 mice. Immunoreactive (IR) area of Iba1 (A, B) and GFAP (C, D) labeling in the cortex (A, C) and hippocampus (B, D) of Line 61 mice compared to non-transgenic (ntg) littermates at the age of 2 and 6 months. Line 61: n = 8, ntg: n = 4. Mean ± SEM. Two-way ANOVA with Bonferroni’s post hoc test.
Analysis of motor impairments in 2 to 6 months old Line 61 mice validates very early motor deficits in the beam walk and wire hanging test that are already very pronounced at the age of 2 months (Figure 3).
Figure 3: Behavioral deficits of Line 61 mice. Number of slips in the beam walk test (A) and time spent hanging in the wire hanging test (B) of 2, 3, and 6 months old Line 61 mice compared to age-matched non-transgenic (ntg) littermates; mean ± SEM; n = 7-15. Mixed-effects analysis with Bonferroni’s post hoc test.
The re-characterization of Line 61 mice validates their PD-like symptoms and pathologies, but in parallel also shows some minor changes compared to previous characterizations. Results of this new characterization of Line 61 mice prove this model to be valuable for preclinical efficacy studies.
More details about the pathology of this model are available in our Line 61 mouse model brochure that we are happy to share upon request.
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