Effect of recombinant adeno-associated virus mediated transforming growth factor-beta1 on corneal allograft survival after high-risk penetrating keratoplasty

Role of Decorin in the Lens and Ocular Diseases

Decorin is an archetypal member of the small leucine-rich proteoglycan gene family and is involved in various biological functions and many signaling networks, interacting with extra-cellular matrix (ECM) components, growth factors, and receptor tyrosine kinases. Decorin also modulates the growth factors, cell proliferation, migration, and angiogenesis. It has been reported to be involved in many ischemic and fibrotic eye diseases, such as congenital stromal dystrophy of the cornea, anterior subcapsular fibrosis of the lens, proliferative vitreoretinopathy, et al. Furthermore, recent evidence supports its role in secondary posterior capsule opacification (PCO) after cataract surgery. The expression of decorin mRNA in lens epithelial cells in vitro was found to decrease upon transforming growth factor (TGF)-β-2 addition and increase upon fibroblast growth factor (FGF)-2 addition. Wound healing of the injured lens in mice transgenic for lens-specific human decorin was promoted by inhibiting myofibroblastic changes. Decorin may be associated with epithelial-mesenchymal transition and PCO development in the lens. Gene therapy and decorin administration have the potential to serve as excellent therapeutic approaches for modifying impaired wound healing, PCO, and other eye diseases related to fibrosis and angiogenesis. In this review, we present findings regarding the roles of decorin in the lens and ocular diseases.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Gene-based Therapeutic Tools in the Treatment of Cornea Disease

BACKGROUND

As one of the main blinding ocular diseases, corneal blindness resulted from neovascularization that disrupts the angiogenic privilege of corneal avascularity. Following neovascularization, inflammatory cells are infiltrating into cornea to strengthen corneal injury. How to maintain corneal angiogenic privilege to treat corneal disease has been investigated for decades.

METHODOLOGY

Local administration of viral and non-viral-mediated anti-angiogenic factors reduces angiogenic protein expression in situ with limited or free of off-target effects upon gene delivery. Recently, Mesenchymal Stem Cells (MSCs) have been studied to treat corneal diseases. Once MSCs are manipulated to express certain genes of interest, they could achieve superior therapeutic efficacy after transplantation.

DISCUSSION

In the text, we first introduce the pathological development of corneal disease in the aspects of neovascularization and inflammation. We summarize how MSCs become an ideal candidate in cell therapy for treating injured cornea, focusing on cell biology, property and features. We provide an updated review of gene-based therapies in animals and preclinical studies in the aspects of controlling target gene expression, safety and efficacy. Gene transfer vectors are potent to induce candidate protein expression. Delivered by vectors, MSCs are equipped with certain characters by expressing a protein of interest, which facilitates better for MSC-mediated therapeutic intervention for the treatment of corneal disease.

CONCLUSION

As the core of this review, we discuss how MSCs could be engineered to be vector system to achieve enhanced therapeutic efficiency after injection.

Effects of an intravitreal injection of interleukin-35-expressing plasmid on pro-inflammatory and anti-inflammatory cytokines

In order to explore the potential effects of interleukin (IL)-35 on IL-10, transforming growth factor-β (TGF-β), interferon-γ (INF)-γ, IL-12 and IL-17, a pcDNA3.1‑IL-35 plasmid was injected into the vitreous cavity of BALB/c mice. Enzyme-linked immunosorbent assay, western blot analysis and quantitative PCR analysis were performed to confirm the successful expression of IL-35. Slit-lamp biomicroscopy, hematoxylin and eosin staining and immunofluorescence were employed to detect the status of eyes, and western blot analysis was performed to examine the expression of corneal graft rejection-related cytokines. There were no abnormalities in the eyes pre-mydriasis or post-mydriasis and no injuries to the cornea or retina following the injection of IL-35-expressing plasmid. An immunofluorescence assay detected the positive expression of IL-35 in corneal epithelial cells from IL-35‑injected mice and negative staining in the control group. Further study revealed that IL-35 enhanced the expression of IL-10 and TGF-β which reached their highest levels at 1 and 2 weeks after injection, respectively (p<0.01). Moreover, the expression of INF-γ and IL-12 was decreased significantly at 2 weeks after the injection of IL-35-expressing plasmid (p<0.05), and the expression of IL-17 was suppressed notably at 4 weeks after the injection (p<0.05). The intravitreal injection of IL-35-expressing plasmid in mice downregulates the expression of pro-inflammatory cytokines and upregulates the expression of anti-inflammatory cytokines. Thus, IL-35 may further be assessed as a potential target for the treatment of corneal graft rejection.