APOE2, E3, and E4 differentially modulate cellular homeostasis, cholesterol metabolism, and inflammatory response in isogenic iPSC-derived astrocytes

Stem Cell Reports. 2022 Jan 11;17(1):110-126. doi: 10.1016/j.stemcr.2021.11.007. Epub 2021 Dec 16.


The apolipoprotein E4 (APOE4) variant is the strongest genetic risk factor for Alzheimer disease (AD), while the APOE2 allele is protective. A major question is how different APOE genotypes affect the physiology of astrocytes, the main APOE-producing brain cells. Here, we differentiated human APOE-isogenic induced pluripotent stem cells (iPSCs) (APOE4, E3, E2, and APOE knockout [APOE-KO]) to functional "iAstrocytes". Mass-spectrometry-based proteomic analysis showed genotype-dependent reductions of cholesterol and lipid metabolic and biosynthetic pathways (reduction: APOE4 >E3 >E2). Cholesterol efflux and biosynthesis were reduced in APOE4 iAstrocytes, while subcellular localization of cholesterol in lysosomes was elevated. An increase in immunoregulatory proteomic pathways (APOE4 >E3 >E2) was accompanied by elevated cytokine release in APOE4 cells (APOE4 >E3 >E2 >KO). Activation of iAstrocytes exacerbated proteomic changes and cytokine secretion mostly in APOE4 iAstrocytes, while APOE2 and APOE-KO iAstrocytes were least affected. Taken together, APOE4 iAstrocytes reveal a disease-relevant phenotype, causing dysregulated cholesterol/lipid homeostasis, increased inflammatory signaling, and reduced β-amyloid uptake, while APOE2 iAstrocytes show opposing effects.

Keywords: APOE; Alzheimer disease; Aβ; astrocytes; cholesterol; homeostasis; iPSCs; inflammation; isogenic; lipid metabolism; proteomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Apolipoprotein E2 / genetics*
  • Apolipoprotein E2 / metabolism
  • Apolipoprotein E3 / genetics*
  • Apolipoprotein E3 / metabolism
  • Apolipoprotein E4 / genetics*
  • Apolipoprotein E4 / metabolism
  • Astrocytes / metabolism*
  • Cell Cycle / genetics
  • Cell Differentiation / genetics*
  • Cholesterol / metabolism
  • Genotype
  • Homeostasis*
  • Humans
  • Immunohistochemistry
  • Induced Pluripotent Stem Cells / cytology*
  • Induced Pluripotent Stem Cells / metabolism
  • Inflammation / genetics
  • Inflammation / metabolism
  • Lipid Metabolism
  • Neural Stem Cells / cytology
  • Neural Stem Cells / metabolism


  • Apolipoprotein E2
  • Apolipoprotein E3
  • Apolipoprotein E4
  • Cholesterol