Exposure to hypoxic environments leads to neurological dysfunction, with recent studies implicating microglia-derived neuroinflammation involved in hypoxia-induced neuronal impairment. However, the underlying pathological mechanisms remain largely unclear. Lipid-droplet-accumulating microglia (LDAM) have been linked to age-related and genetic forms of neurodegeneration, prompting the investigation of their role in hypoxia-induced neuronal impairment. In this study, we observed that hypoxia induced lipid droplets accumulation in microglia, accompanied by increased levels of RETSAT, an enzyme involved in lipid metabolism regulation. Conditional knockout of RETSAT in microglia decreased lipid droplets accumulation and alleviates hypoxia-induced microglial-derived neuroinflammation and oxidative stress, both in vitro and in vivo. Our biological studies indicate that the beneficial effects of RETSAT knockout on lipid droplets degradation are primarily mediated through enhanced activity of hormone-sensitive lipase (HSL). Furthermore, we found that the hypoxic adaptation-related RETSAT mutation Q247R promotes microglia lipolysis under hypoxic conditions. These findings suggest that RetSat is a potential therapeutic target for the prevention and treatment of hypoxia-induced microglial activation.
© 2025 Wiley Periodicals LLC.

This study aims to investigate whether two stress keratins, KRT6A or KRT17, label self-renewing stem cells (SCs) in adult mouse Meibomian gland (MG), the palpebral conjunctiva (PC) homeostasis, and to explore the mechanisms regulating their expression.
KRT6A and KRT17 expression in adult mouse MG and PC were examined by single-nucleus RNA sequencing and immunofluorescence (IF). Lineage-tracing experiments were performed using Krt6a-CreERT2 and Krt17-CreERT2 mice carrying the Rosa26RnTnG or Rosa26RmTmG reporter. As Hedgehog (Hh) signaling, the histone deacetylase HDAC3, and the transcription factor KLF4 regulate KRT6A and KRT17 in other contexts, IF was conducted to assess the in vivo effects of overexpression of the Hh pathway activator GLI2ΔN, and inducible epithelial deletion of Hdac3 or Klf4 on KRT6A and KRT17 expression in the MG and PC.
KRT6A and KRT17 are primarily expressed in the MG central duct and ductules. KRT6A also shows robust expression in PC. Lineage tracing indicated that Krt17 labels self-renewing SCs in the MG, whereas Krt6a labels SCs in the PC. GLI2ΔN overexpression induced ectopic KRT17 expression in MG acini and PC but did not affect KRT6A expression in either MG or PC. Hdac3 deficiency caused expanded expression of KRT6A and KRT17 in MG acini, ectopic KRT17 expression in PC, and increased KRT6A expression in PC basal layer. Klf4 deletion resulted in ectopic KRT17 expression in PC but did not influence KRT6A expression in MG or PC.
Krt6a- and Krt17-expressing cells contribute to adult PC and MG homeostasis, respectively. KRT17 expression is enhanced by GLI2ΔN, and suppressed by HDAC3 and KLF4, whereas KRT6A expression is controlled only by HDAC3. These findings provide important biological insight into tissue-specific maintenance mechanisms and may inform future therapeutic strategies for regenerating MG and PC tissues affected by SC exhaustion or dysregulation.

The mammalian brain is the most cholesterol-rich organ of the body, relying on in situ de novo cholesterol synthesis. Maintaining cholesterol homeostasis is crucial for normal brain function. Oxysterol-binding protein (OSBP)-related proteins (ORPs) are highly conserved cytosolic proteins that coordinate lipid homeostasis by regulating cell signaling, interorganelle membrane contact sites, and non-vesicular transport of cholesterol. Here, we show that ORP6 is highly enriched in the mammalian brain, particularly within neurons and astrocytes, with widespread expression across distinct brain regions, including the hippocampus, which is essential for learning and memory. Whole-body ablation of ORP6 (Osbpl6-/-) in mice resulted in dysregulation of systemic and brain lipid homeostasis, with elevated levels of brain desmosterol and amyloid-beta oligomers (AβOs). Mechanistically, ORP6 knockdown in astrocytes altered the expression of cholesterol metabolism genes, promoting the accumulation of esterified cholesterol in lipid droplets, reducing cholesterol efflux and plasma membrane cholesterol content, and increasing amyloid-beta precursor protein (APP) processing. Our findings underscore the role of ORP6 in systemic and brain lipid homeostasis, highlighting its importance in maintaining overall brain health.
Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.

Metabolic dysfunction-associated steatohepatitis (MASH) is characterized by injury to steatotic hepatocytes that triggers the release of endogenous danger-associated molecular patterns. Recent work demonstrated that exposed lipid droplets (LDs) serve as a pathogenic signal that promotes monocyte infiltration and its maturation into triggering receptor expressed in myeloid cells 2 (TREM2+) macrophages in MASH liver. Here we explore the role of LD exposure in modulating inflammatory signaling in macrophages. We found that LD efferocytosis triggers a global transcriptional response and dampens pro-inflammatory signaling in macrophages. LD treatment attenuated NLRP3 inflammasome activation via mechanisms independent of lysosomal LD hydrolysis. While TREM2 was dispensable for LD efferocytosis by macrophages, it was required for the attenuation of proinflammatory signaling upon LD exposure. Additionally, MS4A7 downregulation contributes to LD efferocytosis-mediated dampening of inflammatory response. These results underscore the dual role of LD exposure in MASH liver by promoting monocyte infiltration and TREM2+ macrophage induction, while restraining proinflammatory response in macrophages.
Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.

Meibomian glands secrete lipid-rich meibum, which prevents tear evaporation. Aging-related Meibomian gland shrinkage may result in part from stem cell exhaustion and is associated with evaporative dry eye disease, a common condition lacking effective treatment. The identities and niche of Meibomian gland stem cells and the signals controlling their activity are poorly defined. Using snRNA-seq, in vivo lineage tracing, ex vivo live imaging, and genetic studies in mice, we identify markers for stem cell populations that maintain distinct regions of the gland and uncover Hedgehog (Hh) signaling as a key regulator of stem cell proliferation. Consistent with this, we show that human Meibomian gland carcinoma exhibits increased Hh signaling. Aged glands display decreased Hh and EGF signaling, deficient innervation, and loss of collagen I in niche fibroblasts, indicating that alterations in both glandular epithelial cells and their surrounding microenvironment contribute to age-related degeneration. These findings suggest new approaches to treat aging-associated Meibomian gland loss.
© 2025. The Author(s).