A single-cell transcriptomic atlas of the human ciliary body

RNA-seq transcriptomic profiling of TGF-β2-exposed human trabecular meshwork explants: Advancing insights beyond conventional cell culture models

Primary open-angle glaucoma (POAG), a leading cause of irreversible vision loss, is closely linked to increased intraocular pressure (IOP), with the trabecular meshwork (TM) playing a critical role in its regulation. The TM, located at the iridocorneal angle, acts as a sieve, filtering the aqueous humor from the eye into the collecting ducts, thus maintaining proper IOP levels. The transforming growth factor-beta 2 (TGF-β2) signaling pathway has been implicated in the pathophysiology of primary open-angle glaucoma POAG particularly, in the dysfunction of the TM. This study utilizes human TM explants to closely mimic in vivo conditions, thereby minimizing transcriptional changes that could arise from cell culture enabling an exploration of the transcriptomic impacts of TGF-β2. Through bulk RNA sequencing and immunohistological analysis, we identified distinct gene expression patterns and morphological changes induced by TGF-β2 exposure (5 ng/ml for 48 h). Bulk RNA sequencing identified significant upregulation in genes linked to extracellular matrix (ECM) regulation and fibrotic signaling. Immunohistological analysis further elucidated the morphological alterations, including cytoskeletal rearrangements and ECM deposition, providing a visual confirmation of the transcriptomic data. Notably, the enrichment analysis unveils TGF-β2's influence on both bone morphogenic protein (BMP) and Wnt signaling pathways, suggesting a complex interplay of molecular mechanisms contributing to TM dysfunction in glaucoma. This characterization of the transcriptomic modifications on an explant model of TM obtained under the effect of this profibrotic cytokine involved in glaucoma is crucial in order to develop and test new molecules that can block their signaling pathways.

The development and the genetic diseases of the ciliary body

The ciliary body, located at the junction of the choroid and iris, is crucial in the development of the embryonic eye. Notch2 signalling, Wnt signalling, transforming growth factor β (TGF-β) signalling, and Pax6 signalling are critical for coordinating the ciliary body formation. These signalling pathways are coordinated with each other and participate in the ciliary body development, ensuring the precise formation and optimal functioning of the eye structure. Although rare, ciliary body hypoplasia, ciliary tumours, and genetic-related iritis indicate the intricate nature of ciliary body development. Given the ciliary body's important biological significance and potential medical relevance, we aim to provide a comprehensive overview of the developmental molecular mechanisms governing ciliary body formation and function. Here, we focus on the intricate signalling pathways governing ciliary body development and corresponding genetic ciliary diseases.

PDGFRα+ITGA11+ fibroblasts foster early-stage cancer lymphovascular invasion and lymphatic metastasis via ITGA11-SELE interplay

Cancer-associated fibroblasts (CAFs) exhibit considerable heterogeneity in advanced cancers; however, the functional annotation and mechanism of CAFs in early-stage cancers remain elusive. Utilizing single-cell RNA sequencing and spatial transcriptomic, we identify a previously unknown PDGFRα+ITGA11+ CAF subset in early-stage bladder cancer (BCa). Multicenter clinical analysis of a 910-case cohort confirms that PDGFRα+ITGA11+ CAFs are associated with lymphovascular invasion (LVI) and poor prognosis in early-stage BCa. These CAFs facilitate LVI and lymph node (LN) metastasis in early-stage BCa, as evidenced in a PDGFRα+ITGA11+ CAFs-specific deficient mouse model. Mechanistically, PDGFRα+ITGA11+ CAFs promote lymphangiogenesis via recognizing ITGA11 surface receptor SELE on lymphatic endothelial cells to activate SRC-p-VEGFR3-MAPK pathway. Further, CHI3L1 from PDGFRα+ITGA11+ CAFs aligns the surrounding matrix to assist cancer cell intravasation, fostering early-stage BCa LVI and LN metastasis. Collectively, our study reveals the crucial role of PDGFRα+ITGA11+ CAFs in shaping metastatic landscape, informing the treatment of early-stage BCa LVI.

Alkali injury-induced pathological lymphangiogenesis in the iris facilitates the infiltration of T cells and ocular inflammation

Inflammatory lymphangiogenesis is intimately linked to immune regulation and tissue homeostasis. However, current evidence has suggested that classic lymphatic vessels are physiologically absent in intraocular structures. Here, we show that neolymphatic vessels were induced in the iris after corneal alkali injury (CAI) in a VEGFR3-dependent manner. Cre-loxP-based lineage tracing revealed that these lymphatic endothelial cells (LECs) originate from existing Prox1+ lymphatic vessels. Notably, the ablation of iridial lymphangiogenesis via conditional deletion of VEGFR3 alleviated the ocular inflammatory response and pathological T cell infiltration. Our findings demonstrate that iridial neolymphatics actively participate in pathological immune responses following injury and suggest intraocular lymphangiogenesis as a valuable therapeutic target for the treatment of ocular inflammation.

Macrophage-induced integrin signaling promotes Schlemm's canal formation to prevent intraocular hypertension and glaucomatous optic neuropathy

Schlemm's canal (SC) functions to maintain proper intraocular pressure (IOP) by draining aqueous humor and has emerged as a promising therapeutic target for glaucoma, the second-leading cause of irreversible blindness worldwide. However, our current understanding of the mechanisms governing SC development and functionality remains limited. Here, we show that vitronectin (VTN) produced by limbal macrophages promotes SC formation and prevents intraocular hypertension by activating integrin αvβ3 signaling. Genetic inactivation of this signaling system inhibited the phosphorylation of AKT and FOXO1 and reduced β-catenin activity and FOXC2 expression, thereby causing impaired Prox1 expression and deteriorated SC morphogenesis. This ultimately led to increased IOP and glaucomatous optic neuropathy. Intriguingly, we found that aged SC displayed downregulated integrin β3 in association with dampened Prox1 expression. Conversely, FOXO1 inhibition rejuvenated the aged SC by inducing Prox1 expression and SC regrowth, highlighting a possible strategy by targeting VTN/integrin αvβ3 signaling to improve SC functionality.

Single-cell transcriptomics of the ocular anterior segment: a comprehensive review

Elucidating the cellular and genetic composition of ocular tissues is essential for uncovering the pathophysiology of ocular diseases. Since the introduction of single-cell RNA sequencing (scRNA-seq) in 2009, vision researchers have performed extensive single-cell analyses to better understand transcriptome complexity and heterogeneity of ocular structures. This technology has revolutionized our ability to identify rare cell populations and to make cross-species comparisons of gene expression in both steady state and disease conditions. Importantly, single-cell transcriptomic analyses have enabled the identification of cell-type specific gene markers and signalling pathways between ocular cell populations. While most scRNA-seq studies have been conducted on retinal tissues, large-scale transcriptomic atlases pertaining to the ocular anterior segment have also been constructed in the past three years. This timely review provides vision researchers with an overview of scRNA-seq experimental design, technical limitations, and clinical applications in a variety of anterior segment-related ocular pathologies. We review open-access anterior segment-related scRNA-seq datasets and illustrate how scRNA-seq can be an indispensable tool for the development of targeted therapeutics.