A novel mouse model reproducing frontal alterations related to the prodromal stage of dementia with LEWY bodies.

Background: Dementia with Lewy bodies (DLB) is the second most common age-related neurocognitive pathology after Alzheimer's disease. Animal models characterizing this disease are lacking and their development would ameliorate both the understanding of neuropathological mechanisms underlying DLB as well as the efficacy of pre-clinical studies tackling this disease.

Methods: We performed extensive phenotypic characterization of a transgenic mouse model overexpressing, most prominently in the dorsal hippocampus (DH) and frontal cortex (FC), wild-type form of the human α-synuclein gene (mThy1-hSNCA, 12 to 14-month-old males). Moreover, we drew a comparison of our mouse model results to DH- and FC- dependent neuropsychological and neuropathological deficits observed in a cohort of patients including 34 healthy control subjects and 55 prodromal-DLB patients (males and females).

Results: Our study revealed an increase of pathological form of soluble α-synuclein, mainly in the FC and DH of the mThy1-hSNCA model. However, functional impairment as well as increase in transcripts of inflammatory markers and decrease in plasticity-relevant protein level were exclusive to the FC. Furthermore, we did not observe pathophysiological or Tyrosine Hydroxylase alterations in the striatum or substantia nigra, nor motor deficits in our model. Interestingly, the results stemming from the cohort of prodromal DLB patients also demonstrated functional deficits emanating from FC alterations, along with preservation of those usually related to DH dysfunctions.

Conclusions: This study demonstrates that pathophysiological impairment of the FC with concomitant DH preservation is observed at an early stage of DLB, and that the mThy1-hSNCA mouse model parallels some markers of this pathology.