Morphological Characteristics and Extracellular Matrix Abnormalities in Astrocytes Derived From iPSCs of Children With Alexander Disease.

Aims: Alexander disease (AxD) is a leukodystrophy caused by mutations in the astrocytic filament gene GFAP. There are currently no effective treatments for AxD. Previous studies have rarely established AxD models with the patient's original GFAP mutations. In this study, we aimed to explore the morphological and transcriptomic characteristics of GFAP-mutant astrocytes via induced pluripotent stem cell (iPSC) models of AxD.

Methods: Fibroblasts from three AxD children were reprogrammed into iPSCs. Wild-type (WT) and AxD-iPSCs were differentiated into astrocytes. We compared the morphological and transcriptomic differences between WT- and AxD iPSC-derived astrocytes.

Results: Astrocytes induced from AxD-derived iPSCs exhibited the Rosenthal fibers (RFs), the main pathological phenotype of AxD. Compared with WT astrocytes, AxD astrocytes had shorter processes, more branches, and larger cell bodies. Transcriptomic analysis revealed that extracellular matrix (ECM) components, particularly chondroitin sulfate proteoglycans (CSPGs), were upregulated, and ECM-degrading enzymes were generally downregulated. These changes may lead to abnormalities in neurons and myelination.

Conclusions: We explored the morphological characteristics of AxD astrocytes via iPSC models and revealed the ECM, previously unexplored for AxD, may be an important new pathogenic mechanism of this disease.