Poor eyesight reveals a new vision gene

The mouse retinal pigment epithelium mounts an innate immune defense response following retinal detachment

The retinal pigment epithelium (RPE) maintains photoreceptor viability and function, completes the visual cycle, and forms the outer blood-retinal barrier (oBRB). Loss of RPE function gives rise to several monogenic retinal dystrophies and contributes to age-related macular degeneration. Retinal detachment (RD) causes separation of the neurosensory retina from the underlying RPE, disrupting the functional and metabolic relationships between these layers. Although the retinal response to RD is highly studied, little is known about how the RPE responds to loss of this interaction. RNA sequencing (RNA-Seq) was used to compare normal and detached RPE in the C57BL6/J mouse. The naïve mouse RPE transcriptome was compared to previously published RPE signature gene lists and from the union of these 14 genes (Bmp4, Crim1, Degs1, Gja1, Itgav, Mfap3l, Pdpn, Ptgds, Rbp1, Rnf13, Rpe65, Slc4a2, Sulf1 and Ttr) representing a core signature gene set applicable across rodent and human RPE was derived. Gene ontology enrichment analysis (GOEA) of the mouse RPE transcriptome identified expected RPE features and functions, such as pigmentation, phagocytosis, lysosomal and proteasomal degradation of proteins, and barrier function. Differentially expressed genes (DEG) at 1 and 7 days post retinal detachment (dprd) were defined as mRNA with a significant (padj≤0.05) fold change (FC) of 0.67 ≥ FC ≥ 1.5 in detached versus naïve RPE. The RPE transcriptome exhibited dramatic changes at 1 dprd, with 2297 DEG identified. The KEGG pathways and biological process GO groups related to innate immune responses were significantly enriched. Lipocalin 2 (Lcn2) and several chemokines were upregulated, while numerous genes related to RPE functions, such as pigment synthesis, visual cycle, phagocytosis, and tight junctions were downregulated at 1 dprd. The response was largely transient, with only 18 significant DEG identified at 7 dprd, including upregulation of complement gene C4b. Validation studies confirmed RNA-Seq results. Thus, the RPE quickly downregulates cell-specific functions and mounts an innate immune defense response following RD. Our data demonstrate that the RPE contributes to the inflammatory response to RD and may play a role in attraction of immune cells to the subretinal space.

Lipid nanoparticles for gene therapy in ocular diseases

OBJECTIVES

Lipid nanoparticles, as a nucleic acid delivery system, have been used as an alternative to treat ocular diseases, since they can cross the ocular barrier and efficiently transfecting nucleic acids to various cells of the eye. The size influences the transfection of genes, biological distribution, diffusion, and cellular uptake. It is therefore important to establish a relationship between size, formulation, and encapsulation percentage.

EVIDENCE ACQUISITION

In this review, we used a search strategy to compare studies of nanomedicine systems aimed at eye diseases where the size of the nanoparticles and the efficiency of encapsulation of genetic material are reported based on the criteria of Preferred Reporting Items for Systematic Reviews (PRISMA ScR 2020 guidelines).

RESULTS

Out of the initial 5932, 169 studies met the inclusion criteria and were included to form the basis of the analysis. Nanoparticles reported are composed mainly of PEG-modified lipids, cholesterol, and cationic lipids, that in combination with messenger or interference RNA, allow the formulation of a nanoparticle with an encapsulation efficiency greater than 95%. The diseases treated mainly focus on conditions related to the retina and cornea. Certain characteristics of nanoparticles increase encapsulation efficiency, such as the size of the nanoparticle and the charge of the outer layer of the nanoparticle.

CONCLUSION

It is still unknown what characteristics lipid nanoparticles should have to successfully treat human eye illnesses. The in vitro and in vivo investigations covered in this review, however, present encouraging results. To improve encapsulation effectiveness and disease gene silencing, nanoparticle formulation is essential. The most stable nanoparticles are those made mostly of cationic lipids, PEG lipids, and cholesterol, which also effectively encapsulate RNA. The encapsulation efficiency is not only influenced by size, but also by other factors such as methods of preparation.