Updated FTP location. CARASIL (cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy) is a hereditary cerebral small-vessel disease caused by loss of function mutations of HTRA1, which is a serine protease with a variety of targets, including extracellular matrix proteins. We isolated pial arteries (the anterior cerebral artery and the middle cerebral artery) from Htra1-KO and wild type mice at 24 months of age.