Nucleic Acid Tetrahedron Delivery of saRNA: Bringing New Hope for the Treatment of Retinal Diseases

Retinal ischemia - reperfusion injury (such as glaucoma and diabetic retinopathy) and oxidative stress injury (such as age - related macular degeneration) are among the main causes of vision loss. Existing therapies have limited effectiveness and cannot reverse cell death. In recent years, scientists have discovered that DJ - 1 protein, as an endogenous antioxidant, can inhibit cell death, but its efficient delivery has always been a challenge. 

Recently, the research team led by Professor Yanping Song from the Ophthalmology Department of the General Hospital of the Central Theater Command successfully used tetrahedral framework nucleic acids (tFNAs) to deliver DJ - 1 small activating RNA (saRNA). This significantly enhanced the antioxidant capacity of retinal cells and protected the retina from ischemia - reperfusion injury by inhibiting ferroptosis, providing a novel treatment strategy for related eye diseases. The research findings were recently published in the internationally renowned academic journal *Cell Proliferation* under the titles "The antioxidant effect of tetrahedral framework nucleic acid - based delivery of small activating RNA targeting DJ - 1 on retinal oxidative stress injury" and "Tetrahedral Framework Nucleic Acid - Based Delivery of DJ - 1 - saRNA Prevent Retinal Ischaemia–Reperfusion Injury via Inhibiting Ferroptosis".

Introduction to the DJ - 1 Small Activating RNA Delivery System

In this study, tetrahedral framework nucleic acids (tFNAs) were used as an effective delivery vector for DJ - 1 small activating RNA (saRNA), thus synthesizing a new nanocomposite (tFNAs - DJ - 1 - saRNA). Nucleic acid tetrahedrons are nanostructures self - assembled from four DNA strands. They can efficiently penetrate cell membranes, protect saRNA from degradation, and possess antioxidant properties themselves, which can synergize with DJ - 1 to enhance the effect of antioxidant damage. Experiments have confirmed that tFNAs - DJ - 1 - saRNA has no immunogenicity and excellent biocompatibility. The small activating RNA targeting the promoter region of the DJ - 1 gene can activate the transcription of the endogenous DJ - 1 gene and increase its protein expression, successfully achieving the delivery and targeted treatment of DJ - 1 saRNA in the retina.

Antioxidant and Anti - apoptotic Effects of tFNAs - DJ - 1 - saRNA 

Under H₂O₂ - induced oxidative stress, tFNAs - DJ - 1 - saRNA reduced the intracellular ROS level by 50% and restored the survival rate of HUVECs from 50% to nearly normal levels. It upregulated the anti - apoptotic protein Bcl - 2, downregulated the pro - apoptotic proteins Bax and Caspase - 3, and improved the Bcl - 2/Bax ratio. tFNAs - DJ - 1 - saRNA effectively blocked the mitochondrial - dependent apoptosis pathway by regulating the Bcl - 2/Bax balance and reduced the activation of Caspase - 3. In the H₂O₂ - induced oxidative stress model, this tFNAs - DJ - 1 - saRNA complex significantly increased cell survival rate, reduced ROS levels, and alleviated cytoskeleton damage, achieving a synergistic protective effect of antioxidant and anti - apoptosis.

Protection of Mitochondrial Function by tFNAs - DJ - 1 - saRNA

 tFNAs - DJ - 1 - saRNA protected mitochondrial function and restored cellular metabolic homeostasis under oxidative stress by maintaining the integrity of the mitochondrial membrane structure (transmission electron microscopy showed inhibition of swelling and cristae rupture), stabilizing the mitochondrial membrane potential (the red/green fluorescence ratio was restored as shown by the JC - 10 probe), and activating the Erk/Nrf2 pathway to promote ATP production (confirmed by Seahorse experiments that the OCR/ECAR and total ATP levels increased).

Anti - ferroptosis Effect of tFNAs - DJ - 1 - saRNA 

Treatment with tFNAs - DJ - 1 - saRNA significantly reduced the levels of lipid ROS and Fe²⁺, and simultaneously improved the mitochondrial morphology and membrane potential of damaged R28 cells, thereby inhibiting ferroptosis.

Protection of the Retina from Ischemia - Reperfusion Injury by tFNAs - DJ - 1 - saRNA 

After tFNAs - DJ - 1 - saRNA was delivered to the retina, it successfully activated DJ - 1. The activated DJ - 1 inhibited the core ferroptosis pathway (reduced lipid peroxidation and maintained glutathione homeostasis) by activating the xCT/GPX4 signaling axis. At the same time, it decreased the accumulation of intracellular Fe²⁺ and the level of oxidative stress, and repaired mitochondrial function and cytoskeleton integrity. In the retinal ischemia - reperfusion injury model, tFNAs - DJ - 1 - saRNA effectively alleviated acute - phase retinal edema, inhibited the apoptosis of retinal ganglion cells (RGCs) and gliosis, maintained the thickness of the retina and the morphology of blood vessels, and ultimately achieved multi - dimensional protection of retinal tissue and inhibited the pathological process of ischemia - reperfusion injury.

Protective Effect of tFNAs - DJ - 1 - saRNA on Rat Retinal Injury

Traditional gene therapies rely on viral vectors, which carry a risk of carcinogenesis. In contrast, the tFNAs - saRNA system does not require viruses and is safer. Currently, the research team has achieved targeted delivery through intravitreal injection. In the future, it is expected to develop an innovative therapy that can provide long - term protection for the retina with a single injection. 

The Ophthalmology Department of the General Hospital of the Central Theater Command is the first unit. Professor Yanping Song and Professor Ming Yan from the Ophthalmology Department are the corresponding authors, and Dr. Qiaowei Wu, Dr. Jingyi Zhu, Dr. Xianggui Zhang, and Dr. Zhende Deng are the co - first authors.

Original article links:

 https://doi.org/10.1111/cpr.13635   

 https://doi.org/10.1111/cpr.13820