COVID-19 is a disease caused by the coronavirus SARS-CoV-2. Millions of patients display neurological symptoms, including headache, impairment of memory, seizures, and encephalopathy, as well as anatomical abnormalities, such as changes in brain morphology.

Background: The ε4 isoform of apolipoprotein E (ApoE) is the most significant genetic risk factor for Alzheimer’s disease. Glial cells are the main source of ApoE in the brain, and in microglia, the ε4 isoform of ApoE has been shown to impair mitochondrial metabolism and the uptake of lipids and Aβ42. However, whether the ε4 isoform alters autophagy or lysosomal activity in microglia in basal and inflammatory conditions is unknown. Methods: Altogether, microglia-like cells (iMGs) from eight APOE3/3 and six APOE4/4 human induced pluripotent stem cell (iPSC) lines were used in this study. The responses of iMGs to Aβ42, LPS and IFNγ were studied by metabolomics, proteomics, and functional assays. Results: Here, we demonstrate that iMGs with the APOE4/4 genotype exhibit reduced basal pinocytosis levels compared to APOE3/3 iMGs. Inflammatory stimulation with a combination of LPS and IFNγ or Aβ42 induced PI3K/AKT/mTORC signaling pathway, increased pinocytosis, and blocked autophagic flux, leading to the accumulation of sequestosome 1 (p62) in both APOE4/4 and APOE3/3 iMGs. Exposure to Aβ42 furthermore caused lysosomal membrane permeabilization, which was significantly stronger in APOE4/4 iMGs and positively correlated with the secretion of the proinflammatory chemokine IL-8. Metabolomics analysis indicated a dysregulation in amino acid metabolism, primarily L-glutamine, in APOE4/4 iMGs. Conclusions: Overall, our results suggest that inflammation-induced metabolic reprogramming places lysosomes under substantial stress. Lysosomal stress is more detrimental in APOE4/4 microglia, which exhibit endo-lysosomal defects.

Background: Patients with Alzheimer's disease (AD) frequently present with cerebral amyloid angiopathy (CAA), characterized by the accumulation of beta-amyloid (Aβ) within the cerebral blood vessels, leading to cerebrovascular dysfunction. Pericytes, which wrap around vascular capillaries, are crucial for regulating cerebral blood flow, angiogenesis, and vessel stability. Despite the known impact of vascular dysfunction on the progression of neurodegenerative diseases, the specific role of pericytes in AD pathology remains to be elucidated. Methods: To explore this, we generated pericyte-like cells from human induced pluripotent stem cells (iPSCs) harboring the Swedish mutation in the amyloid precursor protein (APPswe) along with cells from healthy controls. We initially verified the expression of classic pericyte markers in these cells. Subsequent functional assessments, including permeability, tube formation, and contraction assays, were conducted to evaluate the functionality of both the APPswe and control cells. Additionally, bulk RNA sequencing was utilized to compare the transcriptional profiles between the two groups. Results: Our study reveals that iPSC-derived pericyte-like cells (iPLCs) can produce Aβ peptides. Notably, cells with the APPswe mutation secreted Aβ1-42 at levels ten-fold higher than those of control cells. The APPswe iPLCs also demonstrated a reduced ability to support angiogenesis and maintain barrier integrity, exhibited a prolonged contractile response, and produced elevated levels of pro-inflammatory cytokines following inflammatory stimulation. These functional changes in APPswe iPLCs correspond with transcriptional upregulation in genes related to actin cytoskeleton and extracellular matrix organization. Conclusions: Our findings indicate that the APPswe mutation in iPLCs mimics several aspects of CAA pathology in vitro, suggesting that our iPSC-based vascular cell model could serve as an effective platform for drug discovery aimed to ameliorate vascular dysfunction in AD.

The PSEN1 ΔE9 mutation causes a familial form of Alzheimer’s disease (AD) by shifting the processing of amyloid precursor protein (APP) towards the generation of highly amyloidogenic Aβ42 peptide. We have previously shown that the PSEN1 ΔE9 mutation in human-induced pluripotent stem cell (iPSC)-derived astrocytes increases Aβ42 production and impairs cellular responses. Here, we injected PSEN1 ΔE9 mutant astrosphere-derived glial progenitors into newborn mice and investigated mouse behavior at the ages of 8, 12, and 16 months. While we did not find significant behavioral changes in younger mice, spatial learning and memory were paradoxically improved in 16-month-old PSEN1 ΔE9 glia-transplanted male mice as compared to age-matched isogenic control-transplanted animals. Memory improvement was associated with lower levels of soluble, but not insoluble, human Aβ42 in the mouse brain. We also found a decreased engraftment of PSEN1 ΔE9 mutant cells in the cingulate cortex and significant transcriptional changes in both human and mouse genes in the hippocampus, including the extracellular matrix-related genes. Overall, the presence of PSEN1 ΔE9 mutant glia exerted a more beneficial effect on aged mouse brain than the isogenic control human cells likely as a combination of several factors.

Background: Microglia are the main immune cells of the central nervous system clearing invaded pathogens, damaged cells and toxic aggregates, thus maintaining tissue homeostasis. However, in Alzheimer’s disease (AD), microglia do not perform their job that well anymore. Recent genome‐wide association studies (GWAS) have strongly implicated microglia in AD pathogenesis. One of the genetic variants recently identified is rs616338/p.S209F in ABI3 gene (OR 1.43), which is stronger expressed in microglia than other types of brain cells. ABI3 (ABI family member 3) is a structural component of WAVE2 complex known to regulate formation of lamellipodia, membrane ruffling and phagocytosis. However, the role of ABI3 and its functional difference from a similar protein ABI1 in microglia is not clear.Method: We have used CRISPR/Cas9 technique to generate a knockout iPS line (ABI3 KO) producing truncated protein that lacks Src‐homology 3 domain crucial for the regulation of actin remodeling. We have further differentiated ABI3 KO line and the original isogenic control line (WT) into microglia according to the previously published protocol of McQuade et al (2018).Result: We have found that ABI3 KO microglia exhibited significantly lower uptake of zymosan‐conjugated pHrodo beads, lower expression level of scavenger receptor MSR1 and higher expression level of glucose transporter SLC2A1 as compared to the WT control. ABI3 KO cells were also significantly less responsive to ADP in Transwell migration assay although the mRNA expression of P2RY12 receptor was higher in the KO cells. The protein level of WAVE2 was similar but the level of ABI1 was strongly increased in ABI3 KO cells suggesting a compensatory effect. ABI3 deficiency did not significantly affect secretion of Aβ42, phosphorylation of TAU at Ser214 and phosphorylation of APP at Thr668 in co‐culture with human iPS‐derived neurons harboring Swedish mutation in APP.Conclusion: In conclusion, ABI3 deficiency in microglia significantly impaired phagocytosis and ADP‐induced migration but did not have an effect on AD‐like pathology in co‐culture with diseased iPS‐derived neurons.

Background: Brain endothelial cells (ECs) lining blood vessels are essential for the normal function of the brain. They form the first layer of the blood-brain barrier (BBB) and regulate nutrient exchange, immune responses, and angiogenesis. Numerous studies have reported the disruption of the BBB in neurodegenerative diseases, including Alzheimer’s disease (AD). However, the impact of cell-intrinsic amyloid pathology on EC function remains to be clarified. Methods: To optimize the method for producing functional ECs from human induced pluripotent stem cells (hiPSCs), we compared two different protocols. The first, a widely used method, relies on spontaneous differentiation after mesoderm specification. The second method involves transient overexpression of ETV2 to guide EC differentiation. To study the impact of beta-amyloid overproduction on EC function, we generated ECs from hiPSC lines carrying the APP Swedish mutation (APPswe), which causes AD. We assessed the functionality of both control and APPswe ECs using in vitro permeability assays, 2D and 3D vessel formation assays, and adhesion assays. Results: ECs generated using transient ETV2 overexpression exhibited higher levels of canonical EC markers, tight junction proteins, transporters, leukocyte adhesion molecules, and angiogenesis-associated receptors than ECs derived by spontaneous differentiation. Additionally, ETV2-ECs responded robustly to inflammatory and angiogenic stimuli, displaying functional and transcriptional changes, whereas spontaneously differentiated ECs did not. Consequently, we chose the ETV2 overexpression protocol to study the impact of APPswe mutation on endothelial function. We found that ETV2-ECs carrying the APPswe mutation displayed a reduced angiogenic potential following exposure to the sprouting mix and elevated expression of leukocyte adhesion molecules following inflammatory stimulation, leading to increased adhesion of monocyte-like cells. Conclusions: Overall, our study suggests that APPswe mutation in ECs impairs their response to inflammatory and angiogenic stimuli, potentially contributing to AD progression. Additionally, we confirmed that ETV2 overexpression during a critical window effectively guides hiPSCs toward the EC lineage, resulting in a stable and pure population of ECs suitable for disease modeling and drug screening.