Glaucoma News: South Korean Scientists Develop Novel Gene Therapy For Glaucoma Using AAV2-Based Thioredoxin 2 (Trx2)-Exoenzyme C3 Transferase

Glaucoma News: Glaucoma, a pervasive cause of global visual impairment impacting an estimated 80 million individuals, remains a formidable challenge in the realm of public health. Characterized by progressive damage to the optic nerve head and subsequent visual field loss, glaucoma is intricately linked to elevated intraocular pressure (IOP). Primary open-angle glaucoma (POAG) and steroid-induced glaucoma (SIG) are predominant forms, both contributing to changes in the trabecular meshwork (TM) and compromising aqueous humor outflow. While existing treatments primarily focus on IOP reduction, they fall short in addressing the underlying retinal ganglion cell (RGC) degeneration and optic nerve damage.


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In a groundbreaking endeavor covered in this Glaucoma News report, researchers from the Institute of New Drug Development Research at Cdmogen Co., Ltd., Republic of Korea, and the University of Ulsan have unveiled an innovative gene therapy approach utilizing an adeno-associated virus 2 (AAV2)-based vector expressing a fusion protein of thioredoxin 2 (Trx2) and exoenzyme C3 transferase (C3).
 
Decoding Glaucoma Pathophysiology
Understanding the pathophysiological intricacies of glaucoma is essential for developing targeted therapies. Both POAG and SIG induce TM changes, leading to reduced aqueous humor outflow, heightened IOP, and subsequent optic nerve damage. Recent studies underscore the crucial role of the actin cytoskeleton in TM cells, with fibronectin and alpha-smooth muscle actin (alpha-SMA) being pivotal players in TM remodeling.
 
Exoenzyme C3 transferase, derived from Clostridium botulinum, emerges as a key protagonist in this narrative. It exerts its influence by inhibiting Rho GTPases, upstream regulators of Rho-associated kinase (ROCK) signaling. Elevated Rho-GTPase activity enhances TM contractility, amplifying IOP and contributing to glaucomatous damage. Simultaneously, oxidative stress emerges as a critical factor in RGC degeneration associated with ocular hypertension.
Thioredoxin 2 (Trx2), a redox protein residing in mitochondria, responds to oxidative stress and plays a crucial role in supporting RGC survival in experimental glaucoma models. Recognizing the therapeutic potential of these proteins, the researchers engineered a fusion gene, Trx2-C3, to simultaneously address multiple aspects of glaucoma pathology.
 
Gene Therapy Advancements: Leveraging scAAV2-Based Vector
The delivery of the Trx2-C3 fusion gene necessitated a sophisticated delivery system. Enter the self-complementary adeno-associated virus 2 (scAAV2) vector—a modified version of AAV2. Unlike conventional AAV2, scAAV2 boasts a self-complementary genome, facilitating faster and more efficient transgene expression in target cells. This vector design provides a promising platform for gene therapy, offering sustained effects with a single administration.
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Results and Therapeutic Efficacy
 
-Constructing scAAV2-Trx2-C3
The researchers successfully constructed the scAAV2-Trx2-C3 vector, ensuring controlled expression of the fusion gene Trx2-C3 in treated cells. Rigorous examination via polymerase chain reaction and western blotting confirmed elevated mRNA and protein levels of the fusion gene in response to scAAV2-Trx2-C3 treatment.
 
-Inhibiting RhoA Activation and Cofilin Phosphorylation
In vitro experiments shed light on the efficacy of scAAV2-Trx2-C3 in inhibiting RhoA activation and cofilin phosphorylation at Ser 3. These crucial findings underscore the vector's potential in modulating the RhoA/LIMK-cofilin pathway, thereby influencing cytoskeletal dynamics and cell functions.
 
-Mitigating Oxidative Stress and Fibronectin Expression
Beyond cytoskeletal dynamics, scAAV2-Trx2-C3 demonstrated prowess in mitigating oxidative stress and fibronectin expression in dexamethasone-treated cells. Fibronectin immunocytochemistry revealed a significant reduction in fibronectin expression levels in cells treated with scAAV2-Trx2-C3, pointing towards its ability to curtail fibronectin deposits associated with glaucoma progression.
 
-Lowering IOP in a Dexamethasone-Induced Mouse Model
Moving into in vivo experiments, the researchers utilized a dexamethasone-induced mouse model to evaluate the vector's efficacy in lowering IOP. Intracameral delivery of scAAV2-Trx2-C3 showcased remarkable results, significantly reducing IOP levels for up to four weeks post-injection compared to control vectors. This sustained effect positions scAAV2-Trx2-C3 as a promising candidate for long-term IOP management in glaucoma patients.
 
-Modulating Fibronectin/Alpha-SMA Expression in the Trabecular Meshwork
Histological analysis further elucidated the vector's impact on the extracellular matrix (ECM) in the trabecular meshwork. scAAV2-Trx2-C3 administration led to a significant reduction in fibronectin and alpha-SMA expression, suggesting its potential in modulating the outflow resistance of the TM.
 
-Neuroprotective Effects on Retinal Ganglion Cells
The neuroprotective effects of scAAV2-Trx2-C3 were evident in the preservation of RGCs in the dexamethasone-induced glaucoma mouse model. Immunohistochemistry revealed a higher number of NeuN-positive cells in mice treated with scAAV2-Trx2-C3, underscoring its potential in safeguarding RGCs from degeneration. TUNEL assay results further supported this, showcasing a reduced number of apoptotic cells in the ganglion cell layer.
 
Conclusion
The development of scAAV2-Trx2-C3 as a gene therapy vector marks a significant stride in glaucoma treatment. By concurrently targeting RhoA signaling, oxidative stress, and TM remodeling, this innovative therapy offers a comprehensive approach to address the multifaceted pathophysiology of glaucoma. The sustained effects, coupled with the neuroprotective benefits, position scAAV2-Trx2-C3 as a promising candidate for the future of glaucoma treatment. As research in gene therapy advances, this vector emerges as a beacon of hope for millions affected by this sight-threatening condition, promising a brighter future for glaucoma management.
 
The study findings were published in the peer reviewed International Journal of Molecular Sciences.
https://www.mdpi.com/1422-0067/24/22/16253
 
Thailand Medical News would like to add that studies are also underway by other research teams using plant-based phytochemicals to deliver naturally occurring analogues of thioredoxin 2 (Trx2) and exoenzyme C3 transferase (C3) to retinal ganglion cells.
 
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