MicroRNA-204-5p (miR-204-5p) is a critical regulator of differentiation, structural maintenance, and inflammation in limbal epithelial cells (LECs). This study examined the role of miR-204-5p in modulating the gene expression related to transcription factors, cell structure, extracellular matrix remodeling, and retinoic acid signaling under normal and lipopolysaccharide (LPS)-induced inflammatory conditions. Using qPCR, we analyzed the mRNA levels of FOSL2, FOXC1, Meis2, PPARγ, ABCG2, PTGES2, IL-1β, IL-6, KRT3, KRT12, MMP2, MMP9, RARA, RARB, RXRA, RXRB, CRABP2, RBP1, RDH10, ADH7, ADH1A1, FABP5, CYP1B1, and CYP26A1, while changes in protein levels were assessed via Western blot or ELISA. Our data revealed that the overexpression of miR-204-5p reduced the mRNA levels of FOXC1, KRT12, and RDH10 under normal and inflammatory conditions (p ≤ 0.039). Additionally, it decreased FOSL2 and RXRA mRNA under normal conditions (p = 0.006, p = 0.011) and KRT3 and FABP5 mRNA under inflammatory conditions (p = 0.010, p = 0.001). The IL-6 mRNA expression was significantly increased following the LPS treatment in cells overexpressing miR-204-5p (p = 0.029). A protein analysis revealed significant reductions in FOXC1 and KRT3 in the miR-204-5p-transfected cells during LPS-induced inflammation (p = 0.020, p = 0.030). These findings suggest that miR-204-5p modulates genes critical to the differentiation, migration, and inflammatory response of LECs. The modulation of FOXC1 and KRT3 by miR-204-5p highlights these proteins as novel targets under inflammatory conditions.

Progressive aniridia associated keratopathy is worsening visual acuity of congenital aniridia subjects lifelong. Restoration of PAX6 expression in PAX6 haploinsufficient limbal epithelial cells could be one therapeutic option. In a previous study using aniridia-like CRISPR/Cas9 genome-edited corneal epithelial cells, the antipsychotic drugs duloxetine and ritanserin increased PAX6 mRNA and protein expression. Our purpose was to investigate the effect of duloxetine and ritanserin on cultured primary limbal epithelial cells (pLECs) without and with PAX6 knockdown. pLECs were isolated from 11 aniridia patients and corneoscleral rims of 8 healthy human donors and were treated with 5 µM duloxetine or ritanserin for 24 hours. In addition, pLECs were transfected with small interfering RNA (siRNA) (PAX6 knockdown) in the siRNA-based aniridia cell model and were also treated by 5 µM duloxetine or ritanserin for 24 hours. Gene and protein expression were analyzed using qPCR and Western blot. In both primary aniridia limbal epithelial cells and the siRNA-based aniridia cell model, the expression of PAX6 at the transcriptional or translational level did not show significant changes through duloxetine or ritanserin treatment (p > 0.5). The target genes of PAX6 such as KRT3, KRT12, DSG1, ALDH1A1, ADH7, FABP5, ABCG2 also did not change significantly (p ≥ 0.2). Our study shows that primary cultures of limbal epithelial cells from both aniridia patients and healthy donors were unresponsive to drug treatment. Therefore, our data suggest that different aniridia cell models or cell culture conditions exhibit varying responses to duloxetine and ritanserin. The use of in vivo models could further enhance our understanding of duloxetine and ritanserin treatment in aniridia-associated keratopathy.

MicroRNAs (miRNAs) play critical roles in ocular surface diseases. In our recent study, through microarray analysis, miR-138-5p was identified as one of the most prominent miRNAs expressed in aniridia patients derived primary limbal epithelial cells (pLECs). Although miR-138-5p expression was significantly elevated in aniridia samples, its specific role in the pathogenesis of aniridia-associated keratopathy (AAK) remained unclear. Therefore, the present study focused on exploring the potential functional impact of upregulated miR-138-5p on limbal epithelial stem cell maintenance and function. Cultured pLECs of healthy human donors isolated from corneoscleral rims were transfected with miR-138-5p mimics. The gene and protein expression level of direct target genes of miR138-5p were evaluated. Additionally, cell proliferation, apoptosis, and cell cycle progression was assessed. Overexpression of miR-138-5p significantly downregulated the expression of several target genes, including Cyclin D (CCND1 and CCND3), Hypoxia-Inducible Factor 1-alpha (HIF1A), Forkhead Box C1 (FOXC1), Caspase 3 (CASP3), and Fos-like 1 (FOSL1). Protein levels of Cyclin D1 were also significantly reduced. Additionally, miR-138-5p transfection markedly inhibited cell proliferation and cell cycle progression. Our results demonstrate that miR138-5p can regulate CCND1 expression, and that its overexpression inhibits limbal epithelial cell proliferation and induces cell cycle arrest, suggesting that miR-138-5p acts as a negative regulator in limbal epithelial cells. Therefore, identifying strategies to suppress miR-138-5p expression at the ocular surface in congenital aniridia could have therapeutic potential for slowing the progression of AAK. Nonetheless, further in vivo studies are needed to fully elucidate the mechanistic link between miR-138-5p and AAK pathogenesis.

The dysfunction of limbal epithelial cells (LECs) and limbal stromal cells (LSCs) in congenital aniridia remains incompletely understood. We aimed to analyze mRNA expression profiles of primary human LECs and LSCs, as well as microRNA (miRNA) expression in LSCs, from patients with congenital aniridia (AN-LECs and AN-LSCs). mRNA sequencing of primary human LECs and mRNA and miRNA sequencing of LSCs were performed from patients with aniridia and healthy controls. Gene ontology and pathway analyses were used to evaluate biological processes, cellular components, and molecular functions. Selected deregulated mRNAs and miRNAs were validated by quantitative real-time PCR (RT-qPCR). A total of 188 differentially expressed genes (DEGs) were identified in AN-LECs, and 3001 DEGs in AN-LSCs. In AN-LECs, the top hub genes were associated with inflammatory and interferon-related responses. In contrast, AN-LSCs showed predominant deregulation of mitochondrial and metabolic genes. Pathway analysis revealed involvement of inflammation-related pathways in AN-LECs and metabolic pathways in AN-LSCs. Additionally, 48 deregulated miRNAs were identified in AN-LSCs. This study provides comprehensive mRNA profiles of LECs and LSCs and miRNA profiles of LSCs in congenital aniridia. The findings emphasize the importance of LSC influence and offer insights into molecular mechanisms underlying aniridia-associated keratopathy (AAK), supporting future research and potential therapeutic target identification.

Retinal ribbon synapses are continuously active chemical synapses. The eponymous synaptic ribbon is anchored to the active zone neurotransmitter release sites of ribbon synapses, recruits synaptic vesicles and guides ribbon-associated synaptic vesicles to the release sites. RIBEYE is the major protein component of synaptic ribbons. But likely, additional proteins contribute to ribbon synapse function. The synaptic ribbon of photoreceptor synapses is embedded into a highly polarized microtubule cytoskeleton. Interestingly, proteins of the photoreceptor primary cilium, such as NPHP4 and other ciliary proteins, including KIF3A, were shown to be localized to photoreceptor synaptic ribbons. Previous studies demonstrated that the microtubule motor protein KIF13B catalyzes secretory vesicle transport to the plus ends of microtubules and identified an interaction of KIF13B with NPHP4 at primary cilia. However, the localization of KIF13B, a kinesin-3 family motor protein, in the retina is still unknown. In the present study, we used two different antibodies against KIF13B and high-resolution confocal microscopy, super-resolution structured illumination microscopy (SR-SIM), and post-embedding immunogold electron microscopy to determine the localization of KIF13B in retinal photoreceptors. Apart from its localization at the primary photoreceptor cilium, we found a strong enrichment of KIF13B at photoreceptor synaptic ribbons. The synaptic ribbon is needed for the synaptic enrichment of KIF13B as shown by analyses of synaptic ribbon-deficient RIBEYE knockout mice. These findings suggest that KIF13B performs vesicle trafficking functions at the photoreceptor synaptic ribbon complex at the interface between the synaptic ribbon and the presynaptic microtubule transport system.