LAUSR

Cerebral autosomal‐dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a stroke and dementia syndrome with degeneration and loss of vascular smooth muscle cells (VSMCs). The disease is due to mutations in NOTCH3 playing an important role in VSMC differentiation, proliferation and apoptosis. Searching for a possible cause of VSMC dysfunction in CADASIL, we investigated morphology and proliferative activity the affected myocytes. In material from autopsy brains and skin‐muscle biopsies of patients with CADASIL diagnosis, assessment of VSMCs in arterial vessels at the level of light and electron microscopy was performed. Proliferative activity of VSMCs was evaluated in immune reactions to proliferative markers: proliferating cell nuclear antigen, and cyclins B1 and D. In CADASIL, abnormal morphology of VSMC nuclei was observed in 18.1%, 11.5%, and 6.9% of the cerebral, skin, and skeletal muscle vessels, respectively. The affected myocytes showed variability in nuclear size, irregularity in nuclear shape, and abnormal chromatin appearance. Frequently, double nuclei of equal size or micronuclei were observed. Sometimes, even multinuclear myocytes were found. In some of the nuclei immune reactions to the examined proliferative markers were positive. Aberrant structure and number of VSCM nuclei, and their immunoreactivity to proliferative markers suggest mitotic instability of vascular myocytes in CADASIL. We speculate that mutant NOTCH3 which is unable to control properly VSMC proliferation, and may be responsible for their premature or inappropriate entry into mitosis, irreversible arrest of the cell cycle, senescence or degeneration and loss.