Transcription Factor 4 Regulates the Regeneration of Corneal Endothelial Cells

Saikosaponin D alleviates inflammatory response of osteoarthritis and mediates autophagy via elevating microRNA-199-3p to target transcription Factor-4

OBJECTIVE

This study was to investigate the underlying mechanism by which Saikosaponin D (SSD) mitigates the inflammatory response associated with osteoarthritis (OA) and regulates autophagy through upregulation of microRNA (miR)-199-3p and downregulation of transcription Factor-4 (TCF4).

METHODS

A mouse OA model was established. Mice were intragastrically administered with SSD (0, 5, 10 μmol/L) or injected with miR-199-3p antagomir into the knee. Then, pathological changes in cartilage tissues were observed. Normal chondrocytes and OA chondrocytes were isolated and identified. Chondrocytes were treated with SSD and/or transfected with oligonucleotides or plasmid vectors targeting miR-199-3p and TCF4. Cell viability, apoptosis, inflammation, and autophagy were assessed. miR-199-3p and TCF4 expressions were measured, and their targeting relationship was analyzed.

RESULTS

In in vivo experiments, SSD ameliorated cartilage histopathological damage, decreased inflammatory factor content and promoted autophagy in OA mice. miR-199-3p expression was downregulated and TCF4 expression was upregulated in cartilage tissues of OA mice. miR-199-3p expression was upregulated and TCF4 expression was downregulated after SSD treatment. Downregulation of miR-199-3p attenuated the effect of SSD on OA mice. In in vitro experiments, SSD inhibited the inflammatory response and promoted autophagy in OA chondrocytes. Downregulation of miR-199-3p attenuated the effect of SSD on OA chondrocytes. In addition, upregulation of miR-199-3p alone inhibited inflammatory responses and promoted autophagy in OA chondrocytes. miR-199-3p targeted TCF4. Upregulation of TCF4 attenuated the effects of miR-199-3p upregulation on OA chondrocytes.

CONCLUSIONS

SSD alleviates inflammatory response and mediates autophagy in OA via elevating miR-199-3p to target TCF4.

Autophagy in the normal and diseased cornea

The cornea and covering tear film are together the 'objective lens' of the eye through which 80% of light is refracted. Despite exposure to a physically harsh and at times infectious or toxic environment, transparency essential for sight is in most cases maintained. Such resiliency makes the avascular cornea a superb model for the exploration of autophagy in the regulation of homeostasis with relevancy to all organs. Nonetheless, missense mutations and inflammation respectively clog or apparently overwhelm autophagic flux to create dystrophies much like in neurodegenerative diseases or further exacerbate inflammation. Here there is opportunity to generate novel topical therapies towards the restoration of homeostasis with potential broad application.

Corneal endothelial wound healing: understanding the regenerative capacity of the innermost layer of the cornea

Currently, there are very few well-established treatments to stimulate corneal endothelial cell regeneration in vivo as a cure for corneal endothelial dysfunctions. The most frequently performed intervention for a damaged or dysfunctional corneal endothelium nowadays is corneal endothelial keratoplasty, also known as lamellar corneal transplantation surgery. Newer medical therapies are emerging and are targeting the regeneration of the corneal endothelium, helping the patients regain their vision without the need for donor tissue. Alternatives to donor tissues are needed as the aging population requiring transplants, has further exacerbated the pressure on the corneal eye banking system. Significant ongoing research efforts in the field of corneal regenerative medicine have been made to elucidate the underlying pathways and effector proteins involved in corneal endothelial regeneration. However, the literature offers little guidance and selective attention to the question of how to fully exploit these pathways. The purpose of this paper is to provide an overview of wound healing characteristics from a biochemical level in the lab to the regenerative features seen in the clinic. Studying the pathways involved in corneal wound healing together with their key effector proteins, can help explain the effect on the proliferation and migration capacity of the corneal endothelial cells.

New Frontier in the Management of Corneal Dystrophies: Basics, Development, and Challenges in Corneal Gene Therapy and Gene Editing

ABSTRACT

Corneal dystrophies represent a group of heterogeneous hereditary disorders causing progressive corneal opacification and blindness. Current corneal transplant management for corneal dystrophies faces the challenges of repeated treatments, complex surgical procedures, shortage of appropriate donor cornea, and, more importantly, graft rejection. Genetic medicine could be an alternative treatment regime to overcome such challenges. Cornea carries promising scope for a gene-based therapy involving gene supplementation, gene silencing, and gene editing in both ex vivo and in vivo platforms. In the cornea, ex vivo gene therapeutic strategies were attempted for corneal graft survival, and in vivo gene augmentation therapies aimed to prevent herpes stromal keratitis, neovascularization, corneal clouding, and wound healing. However, none of these studies followed a clinical trial-based successful outcome. CRISPR/Cas system offers a broad scope of gene editing and engineering to correct underlying genetic causes in corneal dystrophies. Corneal tissue--specific gene correction in vitro with minimal off-target effects and optimal gene correction efficiency followed by their successful surgical implantation, or in vivo CRISPR administration targeting pathogenic genes finds a way to explore therapeutic intervention for corneal dystrophies. However, there are many limitations associated with such CRISPR-based corneal treatment management. This review will look into the development of corneal gene therapy and CRISPR-based study in corneal dystrophies, associated challenges, potential approaches, and future directions.