Uncovering SPP1+ Macrophage, Neutrophils and Their Related Diagnostic Biomarkers in Intracranial Aneurysm and Subarachnoid Hemorrhage

Semaglultide targets Spp1+ microglia/macrophage to attenuate neuroinflammation following perioperative stroke

Peripheral surgery evokes neuroimmune activation in the central nervous system and modulates immune cell polarization in the ischemic brain. However, the phenotypic change of microglia and myeloid cells within post-surgical ischemic brain tissue remain poorly defined. Using an integrated approach that combines single-cell RNA sequencing with comprehensive biological analysis in a perioperative ischemic stroke (PIS) model, we identified a distinct Spp1-positive macrophage/microglia (Spp1+ Mac/MG) subgroup that exhibit enriched anti-inflammatory pathways with distinct lipid metabolic reprogrammed profile. Moreover, using immunofluorescence staining, we identified the expression of Glucagon-like peptide-1 receptor (GLP1R) in Spp1+F4/80+ cells and Spp1+Iba-1+ cells. Intraperitoneal administration of semaglutide, a GLP1R agonist clinically approved for the treatment of type 2 diabetes mellitus, resulted in a significant reduction of cerebral infarct volume in PIS mice compared to that in ischemic stroke (IS) mice. Meanwhile, semaglutide treatment also increased the proportion of Spp1+Edu+Iba-1+ cells 3 days after PIS. Using high-parameter flow cytometry, immunofluorescence staining and RNA sequencing, we demonstrated that semaglutide treatment significantly attenuated the expression of neuroinflammatory markers in mice following PIS. We also found that semaglutide treatment significantly ameliorated sensorimotor dysfunction up to 3 days after PIS in mice. Our current finding reveal a novel protective Spp1+Mac/MG subset after PIS and demonstrated that it can be upregulated by semaglutide. We propose that targeting Spp1+Mac/MG subsets using semaglutide could serve as a promising strategy to attenuate the exacerbated neuroinflammation in PIS.

Spatiotemporal dynamic changes of meningeal microenvironment influence meningeal lymphatic function following subarachnoid hemorrhage: from inflammatory response to tissue remodeling

BACKGROUND

Meningeal lymphatic vessels (mLVs) play a critical role in clearing erythrocytes from the subarachnoid space and immune cells from the brain parenchyma following subarachnoid hemorrhage (SAH). However, the drainage function of mLVs is impaired during the acute stage after SAH and gradually recovers in the subacute phase. We aimed to investigate the meningeal transcriptional response post-SAH and elucidate the dynamic influence of meningeal microenvironment on meningeal lymphatic function.

METHODS

We employed bioinformatics analysis of single-cell RNA sequencing and spatial transcriptomics to characterize the spatiotemporal dynamic changes in the early meningeal microenvironment post-SAH. In a mouse model of SAH, the early dynamic changes of the meningeal immune cells and the potential growth factor that promoted the early repair of the mLVs were further investigated and validated.

RESULTS

During the acute phase, myeloid cells early infiltrated the meninges and triggered inflammatory responses. In the subacute phase, the fibroblast population expanded significantly, contributing to tissue remodeling. The interplay between immune cells and fibroblasts regulated cell migration and phenotypic transition, potentially affecting the function of mLVs. Notably, placental growth factor (PGF) emerged as the most prominent ligand within the VEGF signaling pathway received by meningeal lymphatic endothelial cells (mLECs) post-SAH. This signaling event was associated with the early recovery of mLVs after acute immune responses.

CONCLUSIONS

Our study revealed a spatiotemporal transformation of the meningeal microenvironment from an "inflammatory response" phase to a "tissue remodeling" phase following SAH. Monocyte-derived macrophages and self-recruiting neutrophils contributed to impairment of mLVs in the acute stage, while PGF might serve as a key factor promoting early meningeal lymphatic function repair following the inflammatory response. These findings provided novel insights into the cellular dynamics underlying mLVs dysfunction and recovery post-SAH.

Single-Cell RNA Sequencing Revealed Functional Conjunctival Keratinocytes Loss via TGF-β-Wnt/β-Catenin Signaling in Sjögren's Syndrome Related Dry Eye

Purpose

The role of the conjunctiva in the pathophysiology of Sjögren's syndrome (SS) related dry eye disease (DED) remains obscure especially in the view of functional conjunctival epithelia. In order to illustrate effects of conjunctiva in SS, we investigated the interactions between parenchymal cells and immune cells in the conjunctiva with single-cell RNA sequencing technique.

Methods

Freshly collected conjunctiva from a canonical SS model was prepared for 10 × Genomics single-cell RNA sequencing and T cell receptor (TCR) sequencing. Conjunctiva was collected for Western blot, immunofluorescence, multiplex immunohistochemical (mIHC), and flow cytometry. Phenol red thread test, lissamine staining, and qRT-PCR were applied to evaluate signs of DED.

Results

DED phenotype was validated in the SS model. Loss of water-secreting keratinocyte was projected in scRNA-seq data and proved by mIHC test in SS mice. The proportion of Lgr4+ basal epithelial cells with poor ability to differentiate into mature keratinocyte increased, and Wnt/β-catenin signaling was upregulated in it under regulation of TGF-β derived from macrophages. Such macrophages promoted angiogenesis through secretion of VEGFA to activate endothelial cells. Immuno-fibroblasts had an increased population, which were implicated in specifically activated T cell chemotaxis.

Conclusions

In SS conjunctiva, a TGF-β-Wnt/β-catenin axis downregulated the formation of functional keratinocytes accompanied by infiltration of pro-angiogenetic and pro-fibrotic macrophage and pro-inflammatory T cell.