# Comparative lipidomics of iPSC-derived microglia protocols reveal lipid droplet and immune differences mediated by media composition

## TL;DR

Different methods to make microglia-like cells from stem cells lead to big differences in their lipid content, which affects their function and could impact Alzheimer's research.

## Contribution

The study reveals that media composition, particularly B-27 and L-carnitine, strongly influences the lipidome and immune state of iPSC-derived microglia.

## Key findings

- iMGL generated via different protocols show major differences in lipid classes like triglycerides.
- B-27 and L-carnitine reduce triglyceride levels and promote a homeostatic microglial state.
- B-27 makes iMGL metabolically responsive to immune stimuli.

## Abstract

Altered microglial lipid metabolism is heavily implicated in Alzheimer’s disease (AD) and aging. Recently, protocols were developed to generate human induced pluripotent stem cell-derived microglia-like cells (iMGL) to study microglial function in vitro, including embryoid body-based methods and induced transcription factor (iTF)-dependent approaches. Here, we performed comparative lipidomics on iMGL from these methods and report major differences in multiple lipid classes, including triglycerides (TGs), a storage form of fatty acids implicated in microglial reactivity. TGs are strongly increased in iTF microglia due to the absence of a media supplement (B-27). Supplementing iTF microglia with B-27, or its component L-carnitine, reduces TGs and promotes a homeostatic state. B-27 also renders iTF microglia metabolically responsive to immune stimuli. Overall, our data show that iMGL differentiation methods have a major impact on microglial lipidomes and warrant attention when studying AD and neuroinflammatory processes involving lipids.

•iMGL from different generation methods shows major differences in lipid metabolism•B-27 supplement drastically alters the iMGL lipidome and microglial state markers•The B-27 effect is mainly driven by L-carnitine, a cofactor in mitochondrial fatty acid import

iMGL from different generation methods shows major differences in lipid metabolism

B-27 supplement drastically alters the iMGL lipidome and microglial state markers

The B-27 effect is mainly driven by L-carnitine, a cofactor in mitochondrial fatty acid import

Van der Kant and colleagues uncover that the lipidome of iPSC-derived microglia is strongly affected by the selection of differentiation protocol and media supplements. The authors show that the B-27 supplement, and specifically the L-carnitine present in B-27, reduces fatty acid storage in triglycerides, thereby decreasing lipid droplet content and inducing a more homeostatic microglial state.