A Comparison of Subconjunctival Wound Healing between Different Methods of Dissecting Subconjunctival Tissues

Knockdown of lncRNA PVT1 protects human trabecular meshwork cells against H2O2-induced injury via the regulation of the miR-29a-3p/VEGF/MMP-2 axis

Purpose

Human trabecular meshwork cell (HTMC) dysfunction results in imbalanced aqueous humor inflow and outflow, leading to an increase in intraocular pressure (IOP). Uncontrolled high IOP can promote the occurrence of glaucoma, an irreversible optic neuropathy. Here, we explored whether the long non-coding RNA plasmacytoma variant translocation 1 (lncRNA PVT1)/microRNA-29a-3p (miR-29a-3p) axis could ameliorate HTMC dysfunction under oxidative stress by modulating the expression of the proangiogenic factor vascular endothelial growth factor (VEGFA) and the profibrotic factor metalloproteinase-2 (MMP-2).

Methods

HTMCs were cultured under H2O2-induced oxidative stress for 48 h. The expression of lncRNA PVT1, miR-29a-3p, VEGFA, MMP-2, intracellular adhesion molecule-1 (ICAM-1), and alpha-smooth muscle actin (α-SMA) was detected by reverse transcription quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence. Interference experiments were conducted via the transfection of HTMCs with small interfering RNA (siRNA) targeting lncRNA PVT1 or miR-29a-3p mimics. A luciferase reporter assay was undertaken to identify the presence of a miR-29a-3p binding site in lncRNA PVT1. Flow cytometry and Transwell and Cell Counting Kit-8 assays were employed to evaluate HTMC functions under oxidative stress with different treatments.

Results

In HTMCs, the expression of lncRNA PVT1 was induced by H2O2 treatment, whereas that of miR-29a-3p was inhibited. The levels of angiogenic factors (VEGFA, ICAM-1) and fibrosis-associated mediators (MMP-2, α-SMA) were upregulated in HTMCs under oxidative stress. The siRNA-mediated suppression of lncRNA PVT1 or the upregulation of miR-29a-3p significantly suppressed the expression of VEGFA, MMP-2, ICAM-1, and α-SMA. A luciferase reporter assay confirmed that lncRNA PVT1 directly targeted miR-29a-3p and acted as a miR-29a-3p sponge. The knockdown of lncRNA PVT1 restored the level of miR-29a-3p in H2O2-treated HTMCs, thereby inhibiting VEGFA and MMP-2, its target mRNAs. HTMC dysfunction, including increased apoptosis and decreased cell mobility and viability, could be effectively ameliorated by lncRNA PVT1 downregulation or miR-29a-3p overexpression under oxidative stress.

Conclusion

LncRNA PVT1 has potential as a therapeutic target for inhibiting VEGFA and MMP-2, thus protecting HTMCs, suppressing the progression of fibrosis, and, consequently, improving the outcome of glaucoma filtration surgery.

Matrix Metalloproteinases and Glaucoma

Matrix metalloproteinases (MMPs) are enzymes that decompose extracellular matrix (ECM) proteins. MMPs are thought to play important roles in cellular processes, such as cell proliferation, differentiation, angiogenesis, migration, apoptosis, and host defense. MMPs are distributed in almost all intraocular tissues and are involved in physiological and pathological mechanisms of the eye. MMPs are also associated with glaucoma, a progressive neurodegenerative disease of the eyes. MMP activity affects intraocular pressure control and apoptosis of retinal ganglion cells, which are the pathological mechanisms of glaucoma. It also affects the risk of glaucoma development based on genetic pleomorphism. In addition, MMPs may affect the treatment outcomes of glaucoma, including the success rate of surgical treatment and side effects on the ocular surface due to glaucoma medications. This review discusses the various relationships between MMP and glaucoma.

Wound Healing Response After Bleb-Forming Glaucoma Surgery With a SIBS Microshunt in Rabbits

Purpose

The PreserFlo MicroShunt is an innovative implant for the surgical treatment of glaucoma. Although usually effective, surgeries can still fail due to fibrosis. This study was conducted to gain insight into the histological aspects of the fibrotic response and find potential targets to reduce postoperative fibrosis.

Methods

Fifteen New Zealand White rabbits were implanted with a microshunt and followed up for 40 days. Animals were euthanized at postoperative days (PODs) 1, 5, and 40 to collect eyes for histological evaluation. Bleb formation and ocular health were assessed by slit-lamp (SL) biomicroscopy and optical coherence tomography (OCT). Intraocular pressure (IOP) was measured using rebound tonometry.

Results

Blebs failed after approximately 2 weeks based on bleb survival and IOP measurements. No severe complications were observed with OCT and SL. Histology revealed a wide variety of cells, in the bleb and around the microshunt, including polymorphonuclear leucocytes (PMNs), myofibroblasts, and foreign body giant cells, at different PODs.

Conclusions

Implantation of a poly(styrene-b-isobutylene-b-styrene) microshunt in rabbits resulted in the occurrence of a wide variety of cells during the wound-healing response. Future research should further elucidate the potential of these (earlier often overlooked) cells to target the fibrotic response in vivo—for example, by developing novel antifibrotic drugs, methods for sustained delivery of medications, or augmenting material properties.

Translational Relevance

Current antifibrotic therapies aim to inhibit myofibroblasts; however, a wide variety of cells are involved in the fibrotic response. Future research focusing on these cells could offer novel methods for reducing the fibrotic response after glaucoma surgery.