Dutch-type cerebral amyloid angiopathy (D-CAA) is a rare neurodegenerative/neurovascular disease caused by a point mutation in the amyloid precursor protein (APP) gene that leads to aggregation of... Show moreDutch-type cerebral amyloid angiopathy (D-CAA) is a rare neurodegenerative/neurovascular disease caused by a point mutation in the amyloid precursor protein (APP) gene that leads to aggregation of the amyloid beta peptide in the brain vasculature. It is characterized by intracerebral hemorrhages, infarcts, cognitive decline and vascular dementia. To date there are no therapies that prevent or delay D-CAA onset or progression. In this thesis we aimed to model the disease using patient-derived cell models, develop and test an RNA-targeting therapy and look into the mutated protein trafficking in the cell. Using D-CAA patient-derived induced pluripotent stem cells as template, we generated state-of-the-art 3D brain organoids and successfully modeled the amyloid beta aggregation and other D-CAA disease signatures, also found in the D-CAA human brain. We developed and tested an RNA-targeting therapy that showed efficient and significant reduction of the amyloid beta peptide in D-CAA patient-derived cells and control mice. Finally, when looking into the mutated APP protein trafficking we have found that the Dutch mutation affects the processing and trafficking of APP protein prior to the generation of the amyloid beta fragment, a phenotype that was reversed when the RNA-targeting therapy was applied. With the data generated in this thesis we hope to further advance the knowledge on D-CAA disease mechanisms as well as the possibility for therapeutics that will benefit D-CAA patients. Show less
Aims: The aim of this work is to study the association of urokinase plasminogen activator (uPA) with development and progression of cerebral amyloid angiopathy (CAA). Materials and methods: We... Show moreAims: The aim of this work is to study the association of urokinase plasminogen activator (uPA) with development and progression of cerebral amyloid angiopathy (CAA). Materials and methods: We studied the expression of uPA mRNA by quantitative polymerase chain reaction (qPCR) and co-localisation of uPA with amyloid-beta (A beta) using immunohistochemistry in the cerebral vasculature of rTg-DI rats compared with wild-type (WT) rats and in a sporadic CAA (sCAA) patient and control subject using immunohistochemistry. Cerebrospinal fluid (CSF) uPA levels were measured in rTg-DI and WT rats and in two separate cohorts of sCAA and Dutch-type hereditary CAA (D-CAA) patients and controls, using enzyme-linked immunosorbent assays (ELISA). Results: The presence of uPA was clearly detected in the cerebral vasculature of rTg-DI rats and an sCAA patient but not in WT rats or a non-CAA human control. uPA expression was highly co-localised with microvascular A beta deposits. In rTg-DI rats, uPA mRNA expression was highly elevated at 3 months of age (coinciding with the emergence of microvascular A beta deposition) and sustained up to 12 months of age (with severe microvascular CAA deposition) compared with WT rats. CSF uPA levels were elevated in rTg-DI rats compared with WT rats (p = 0.03), and in sCAA patients compared with controls (after adjustment for age of subjects, p = 0.05 and p = 0.03). No differences in CSF uPA levels were found between asymptomatic and symptomatic D-CAA patients and their respective controls (after age-adjustment, p = 0.09 and p = 0.44). Increased cerebrovascular expression of uPA in CAA correlates with increased quantities of CSF uPA in rTg-DI rats and human CAA patients, suggesting that uPA could serve as a biomarker for CAA. Show less
Scherlek, A.A.; Kozberg, M.G.; Nicoll, J.A.R.; Perosa, V.; Freeze, W.M.; Weerd, L. van der; ... ; Veluw, S.J. van 2022
Haemorrhagic amyloid-related imaging abnormalities on MRI are frequently observed adverse events in the context of amyloid beta immunotherapy trials in patients with Alzheimer's disease. The... Show moreHaemorrhagic amyloid-related imaging abnormalities on MRI are frequently observed adverse events in the context of amyloid beta immunotherapy trials in patients with Alzheimer's disease. The underlying histopathology and pathophysiological mechanisms of haemorrhagic amyloid-related imaging abnormalities remain largely unknown, although coexisting cerebral amyloid angiopathy may play a key role. Here, we used ex vivo MRI in cases that underwent amyloid beta immunotherapy during life to screen for haemorrhagic lesions and assess underlying tissue and vascular alterations. We hypothesized that these lesions would be associated with severe cerebral amyloid angiopathy. Ten cases were selected from the long-term follow-up study of patients who enrolled in the first clinical trial of active amyloid beta immunization with AN1792 for Alzheimer's disease. Eleven matched non-immunized Alzheimer's disease cases from an independent brain brank were used as 'controls'. Formalin-fixed occipital brain slices were imaged at 7 T MRI to screen for haemorrhagic lesions (i.e. microbleeds and cortical superficial siderosis). Samples with and without haemorrhagic lesions were cut and stained. Artificial intelligence-assisted quantification of amyloid beta plaque area, cortical and leptomeningeal cerebral amyloid angiopathy area, the density of iron and calcium positive cells and reactive astrocytes and activated microglia was performed. On ex vivo MRI, cortical superficial siderosis was observed in 5/10 immunized Alzheimer's disease cases compared with 1/11 control Alzheimer's disease cases (kappa = 0.5). On histopathology, these areas revealed iron and calcium positive deposits in the cortex. Within the immunized Alzheimer's disease group, areas with siderosis on MRI revealed greater leptomeningeal cerebral amyloid angiopathy and concentric splitting of the vessel walls compared with areas without siderosis. Moreover, greater density of iron-positive cells in the cortex was associated with lower amyloid beta plaque area and a trend towards increased post-vaccination antibody titres. This work highlights the use of ex vivo MRI to investigate the neuropathological correlates of haemorrhagic lesions observed in the context of amyloid beta immunotherapy. These findings suggest a possible role for cerebral amyloid angiopathy in the formation of haemorrhagic amyloid-related imaging abnormalities, awaiting confirmation in future studies that include brain tissue of patients who received passive immunotherapy against amyloid beta with available in vivo MRI during life. Show less
Daoutsali, E.; Hailu, T.T.; Buijsen, R.A.M.; Pepers, B.A.; Graaf, L.M. van der; Verbeek, M.M.; ... ; Roon-Mom, W.M.C. van 2021
Dutch-type cerebral amyloid angiopathy (D-CAA) is a monogenic form of cerebral amyloid angiopathy and is inherited in an autosomal dominant manner. The disease is caused by a point mutation in exon... Show moreDutch-type cerebral amyloid angiopathy (D-CAA) is a monogenic form of cerebral amyloid angiopathy and is inherited in an autosomal dominant manner. The disease is caused by a point mutation in exon 17 of the amyloid precursor protein (APP) gene that leads to an amino acid substitution at codon 693. The mutation is located within the amyloid beta (A beta) domain of APP, and leads to accumulation of toxic A beta peptide in and around the cerebral vasculature. We have designed an antisense oligonucleotide (AON) approach that results in skipping of exon 17, generating a shorter APP isoform that lacks part of the A beta domain and the D-CAA mutation. We demonstrate efficient AON-induced skipping of exon 17 at RNA level and the occurrence of a shorter APP protein isoform in three different cell types. This resulted in a reduction of A beta 40 in neuronally differentiated, patient-derived induced pluripotent stem cells. AON-treated wild-type mice showed successful exon skipping on RNA and protein levels throughout the brain. These results illustrate APP splice modulation as a promising therapeutic approach for D-CAA. Show less
