
シュレム管細胞は血管内皮細胞と リンパ管内皮細胞の特性を併せ持ち、リンパ管系の特徴が優勢であることが明らかになった。また、シュレム管の内壁と外壁で異なる3つの分子クラスが存在することが初めて示された。


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Schlemm’s canal (SC) is central in intraocular pressure regulation but requires much characterization. It has distinct inner and outer walls, each composed of Schlemm’s canal endothelial cells (SECs) with different morphologies and functions. Recent transcriptomic studies of the anterior segment added important knowledge, but were limited in power by SEC numbers or did not focus on SC. To gain a more comprehensive understanding of SC biology, we performed bulk RNA sequencing on C57BL/6J SC, blood vessel, and lymphatic endothelial cells from limbal tissue (∼4500 SECs). We also analyzed mouse limbal tissues by single-cell and single-nucleus RNA sequencing (C57BL/6J and 129/Sj strains), successfully sequencing 903 individual SECs. Together, these datasets confirm that SC has molecular characteristics of both blood and lymphatic endothelia with a lymphatic phenotype predominating. SECs are enriched in pathways that regulate cell-cell junction formation pointing to the importance of junctions in determining SC fluid permeability. Importantly, and for the first time, our analyses characterize 3 molecular classes of SECs, molecularly distinguishing inner wall from outer wall SECs and discovering two inner wall cell states that likely result from local environmental differences. Further, and based on ligand and receptor expression patterns, we document key interactions between SECs and cells of the adjacent trabecular meshwork (TM) drainage tissue. Also, we present cell type expression for a collection of human glaucoma genes. These data provide a new molecular foundation that will enable the functional dissection of key homeostatic processes mediated by SECs as well as the development of new glaucoma therapeutics.

Significance statement Schlemm’s canal is a critical ocular drainage structure that maintains intraocular pressure with important consequences for glaucoma. Despite this, Schlemm’s canal has been relatively understudied with the molecular process that mediate its function, maintain its health, or that are compromised in glaucoma needing much deeper characterization. This study is important as it provides the most comprehensive molecular characterization of Schlemm’s canal cells to date providing a wealth of molecular details. In addition to highlighting important biological pathways, this information will guide studies to develop new treatments against glaucoma.

### Competing Interest Statement

The authors have declared no competing interest.

Transcriptomic profiling of Schlemm’s canal cells reveals a lymphatic-biased identity and three major cell states

眼圧調節に重要なシュレム管細胞の詳細な転写プロファイリング