Alzheimer's disease (AD) is characterized by a specific pattern of neuropathological changes, including extracellular amyloid beta (Aβ) deposits, intracellular neurofibrillary tangles (NFTs), granulovacuolar degeneration (GVD) representing cytoplasmic vacuolar lesions, and synapse and neuronal loss. Necroptosis, a programmed form of necrosis, has recently been shown to be involved in AD. Necroptotic cell death is characterized by the assembly of the necrosome complex, consisting of phosphorylated proteins, i.e. receptor-interacting serine/threonineprotein kinase 1 and 3 (pRIPK1 and pRIPK3), and mixed lineage kinase domain-like protein (pMLKL). However, it is not yet clear whether necrosome assembly takes place in the brain regions showing AD-related neuronal loss, and whether it is associated with AD-related neuropathological changes. Here, we analyzed brains of AD, pathologically defined preclinical AD, and non-AD control cases to determine the neuropathological characteristics and distribution pattern of the necrosome components. We demonstrated that all three activated necrosome components can be detected in GVD lesions (GVDn+, i.e. GVD with activated necrosome) in neurons, and colocalized with classical GVD markers, such as pTDP-43 and CK1δ. GVDn+ neurons were inversely associated with the neuronal density in the early affected CA1 region of the hippocampus and in the late affected frontal cortex layer III. Finally, the distribution of non-phosphorylated proteins was studied. RIPK1 was mainly expressed in astrocytes and in GVD lesions, RIPK3 was detected in dystrophic neurites of neuritic plaques and in neurons. GVD lesions remained negative for non-phosphorylated RIPK3. MLKL could only be detected by western blotting showing an increase in p-preAD and AD cases. Accordingly, AD-related GVD lesions exhibited all components of the activated necrosome and were associated with reduced neuronal densities in the affected anatomical regions, and with AD-defining parameters, showing the strongest correlation and partial colocalization with NFT pathology. Therefore, we conclude that the presence of the necrosome in GVD plays a role in AD, possibly by representing an AD-specific form of necroptosis-related neuron death. Hence, necroptosis-related neuron loss could be an interesting therapeutic target for treating AD.

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The co-existence of multiple pathologies and proteins is a common feature in the brains of cognitively impaired elderly individuals. Transactive response DNA-binding protein (TDP-43) has been discovered to accumulate in limbic brain regions of a portion of late-onset Alzheimer’s disease (AD) patients, in addition to amyloid-β and τ protein. However, it is not yet known whether the TDP-43 species in the AD brain differ in their composition, when compared among different AD cases and to frontotemporal lobar degeneration cases with TDP-43 inclusions (FTLD-TDP). Furthermore, it is not known whether TDP-43 pathology in AD is related to symptoms of the frontotemporal dementia (FTD) spectrum. In this study, we investigated the molecular pattern of TDP-43 lesions with five different antibodies against different phosphorylated (pTDP-43) and non-phosphorylated TDP-43 epitopes. We analyzed a cohort of 97 autopsy cases, including brains from 20 non-demented individuals, 16 cognitively normal pathologically-defined preclinical AD (p-preAD), 51 neuropathologically-confirmed AD cases and 10 FTLD-TDP cases as positive controls. We observed distinct neuropathological patterns of TDP-43 among AD cases. In 11 neuropathologically-confirmed AD cases we found dystrophic neurites (DNs), neuronal cytoplasmic inclusions (NCIs) and/or neurofibrillary tangle (NFT)-like lesions not only positive for pTDP-43409/410, but also for pTDP-43 phosphorylated at serines 403/404 (pTDP-43403/404) and non-phosphorylated, full-length TDP-43, as seen with antibodies against C-terminal TDP-43 and N-terminal TDP-43. These cases were referred to as ADTDP + FL because full-length TDP-43 was presumably present in the aggregates. FTLD-TDP cases showed a similar molecular TDP-43 pattern. A second pattern, which was not seen in FTLD-TDP, was observed in most of p-preAD, as well as 30 neuropathologically-confirmed AD cases, which mainly exhibited NFTs and NCIs stained with antibodies against TDP-43 phosphorylated at serines 409/410 (pTDP-43409, pTDP-43409/410). Because only phosphorylated C-terminal species of TDP-43 could be detected in the lesions we designated these AD cases as ADTDP + CTF. Ten AD cases did not contain any TDP-43 pathology and were referred to as ADTDP-. The different TDP-43 patterns were associated with clinically typical AD symptoms in 80% of ADTDP + CTF cases, 63,6% of ADTDP + FL and 100% of the ADTDP- cases. On the other hand, clinical symptoms characteristic for FTD were observed in 36,4% of ADTDP + FL, in 16,6% of the ADTDP + CTF, and in none of the ADTDP- cases. Our findings provide evidence that TDP-43 aggregates occurring in AD cases vary in their composition, suggesting the distinction of different molecular patterns of TDP-43 pathology ranging from ADTDP- to ADTDP + CTF and ADTDP + FL with possible impact on their clinical picture, i.e. a higher chance for FTD-like symptoms in ADTDP + FL cases.

Electrospun PLA matrices are a suitable substrate for short-term culture of AF-MSC. In rats, addition of AF-MSC to PLA matrices modulates the host response after subcutaneous implantation, yet without a difference in macrophage profile compared with control.

Proteome profile changes in Alzheimer's disease (AD) brains have been reported. However, it is unclear whether they represent a continuous process, or whether there is a sequential involvement of distinct proteins. To address this question, we used mass spectrometry. We analyzed soluble, dispersible, sodium dodecyl sulfate, and formic acid fractions of neocortex homogenates (mainly Brodmann area 17-19) from 18 pathologically diagnosed preclinical AD, 17 symptomatic AD, and 18 cases without signs of neurodegeneration. By doing so, we identified four groups of ADrelated proteins being changed in levels in preclinical and symptomatic AD cases: earlyresponding, late-responding, gradually-changing, and fraction-shifting proteins. Gene ontology analysis of these proteins and all known AD-risk/causative genes identified vesicle endocytosis and the secretory pathway-related processes as an early-involved AD component. In conclusion, our findings suggest that subtle changes involving the secretory pathway and endocytosis precede severe proteome changes in symptomatic AD as part of the preclinical phase of AD. The respective early-responding proteins may also contribute to synaptic vesicle cycle alterations in symptomatic AD.

In ALS and FTLD‐TDP necrosome formation (= formation of a complex consisting of pRIPK1, pRIPK3 and pMLKL) is observed in granulovacuolar degeneration in neurons of the medial temporal lobe and correlates with TDP‐43 neuronal cytoplasmic inclusions. Motor neurons in the spinal cord and in the primary motor cortex do not show these granulovacuolar degeneration lesions. Accordingly, necrosome accumulation is one type of cell death pathology probably relevant in medial temporal lobe neurons of ALS and FTLD‐TDP cases but not in ALS‐related motor neuron death, for which another cell death mechanism may be responsible.

providing sections stained for C9orf72 dipeptide repeats, and Klara Gawor for support with statistical analyses. Ethical ApprovalHuman brain and spinal cord tissues were collected in accordance with the applicable laws in Belgium (UZ Leuven) and Germany (Ulm). The recruitment protocols for collecting the human brains were approved by the ethical committees of the University of Ulm (Germany) and of UZ Leuven (Belgium). This study was approved by the UZ Leuven ethical committee (Leuven, Belgium). All animal care and experiments were approved by the KU Leuven Ethical Committee and were carried out according to the Belgian law.

Alzheimer’s disease is neuropathologically characterized by the deposition of the amyloid β-peptide (Aβ) as amyloid plaques. Aβ plaque pathology starts in the neocortex before it propagates into further brain regions. Moreover, Aβ aggregates undergo maturation indicated by the occurrence of post-translational modifications. Here, we show that propagation of Aβ plaques is led by presumably non-modified Aβ followed by Aβ aggregate maturation. This sequence was seen neuropathologically in human brains and in amyloid precursor protein transgenic mice receiving intracerebral injections of human brain homogenates from cases varying in Aβ phase, Aβ load and Aβ maturation stage. The speed of propagation after seeding in mice was best related to the Aβ phase of the donor, the progression speed of maturation to the stage of Aβ aggregate maturation. Thus, different forms of Aβ can trigger propagation/maturation of Aβ aggregates, which may explain the lack of success when therapeutically targeting only specific forms of Aβ.