Translational models for vascular cognitive impairment: a review including larger species.

BACKGROUND: Disease models are useful for prospective studies of pathology, identification of molecular and cellular mechanisms, pre-clinical testing of interventions, and validation of clinical biomarkers. Here, we review animal models relevant to vascular cognitive impairment (VCI). A synopsis of each model was initially presented by expert practitioners. Synopses were refined by the authors, and subsequently by the scientific committee of a recent conference (International Conference on Vascular Dementia 2015). Only peer-reviewed sources were cited. METHODS: We included models that mimic VCI-related brain lesions (white matter hypoperfusion injury, focal ischaemia, cerebral amyloid angiopathy) or reproduce VCI risk factors (old age, hypertension, hyperhomocysteinemia, high-salt/high-fat diet) or reproduce genetic causes of VCI (CADASIL-causing Notch3 mutations). CONCLUSIONS: We concluded that (1) translational models may reflect a VCI-relevant pathological process, while not fully replicating a human disease spectrum; (2) rodent models of VCI are limited by paucity of white matter; and (3) further translational models, and improved cognitive testing instruments, are required.

Cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL).

OBJECTIVE: To characterize the clinical and MRI features of 2 families with adult-onset dominant leukoencephalopathy and strokes and identify the underlying genetic cause. METHODS: We applied MRI pattern recognition, whole-exome sequencing, and neuropathology. RESULTS: Based on brain imaging, 13 family members of 40 years or older from 2 families were diagnosed with the disease; in 11 family members of the same age, MRI was normal. In the affected family members, MRI showed a leukoencephalopathy that was disproportionately severe compared to the clinical disease. The clinical picture was dominated by ischemic and hemorrhagic strokes, slow and late cognitive deterioration, and therapy-resistant hypertension. With whole-exome sequencing, we identified one variant shared by both families and segregating with the disease: c.973C>T in CTSA. Haplotype analysis revealed a shared 1,145-kb interval encompassing the CTSA variant on chromosome 20q13.12, suggesting a common ancestor. Brain autopsy of 3 patients showed a leukoencephalopathy that was disproportionately extensive compared to the vascular abnormalities. CTSA encodes cathepsin A. Recessive CTSA mutations cause galactosialidosis. One of the numerous cathepsin A functions is to degrade endothelin-1. In the patients, striking endothelin-1 immunoreactivity was found in white matter astrocytes, correlating with increased numbers of premyelinating oligodendrocyte progenitors. This finding supports a role for endothelin-1 in the leukoencephalopathy through inhibition of oligodendrocyte progenitor maturation. CONCLUSIONS: CARASAL (cathepsin A-related arteriopathy with strokes and leukoencephalopathy) is a novel hereditary adult-onset cerebral small vessel disease. It is of interest that, next to the cerebral vascular abnormalities, endothelin-1 may have a role in the pathogenesis of the extensive leukoencephalopathy.

Amyloid ß in hereditary cerebral hemorrhage with amyloidosis-Dutch type.

Hereditary cerebral hemorrhage with amyloidosis - Dutch type is an autosomal dominant hereditary disease caused by a point mutation in the amyloid precursor protein gene on chromosome 21. The mutation causes an amino acid substitution at codon 693 (E22Q), the 'Dutch mutation'. Amyloid ß, the product after cleavage of the amyloid precursor protein, is secreted into the extracellular space. The Dutch mutation leads to altered amyloid ß cleavage and secretion, enhanced aggregation properties, higher proteolysis resistance, lowered brain efflux transporter affinity, and enhanced cell surfaces binding. All these result in amyloid ß accumulation in cerebral vessel walls, causing cell death and vessel wall integrity loss, making cerebral vessel walls in hereditary cerebral hemorrhage with amyloidosis-Dutch type more prone to rupture and obstruction, leading to hemorrhages and infarcts. Studying the effects of altered amyloid ß metabolism due to mutations like the 'Dutch' provides us with a better understanding of amyloid ß toxicity, also in other amyloid ß diseases like sporadic cerebral amyloid angiopathy and Alzheimer's disease.