Academic Background and Problem Statement

Retinopathy of Prematurity (ROP) is a common retinal neurovascular disorder in premature infants, primarily occurring in those whose retinal vascular development is incomplete. Due to exposure to a relatively hyperoxic environment after birth, especially with supplemental oxygen therapy, hyperoxia suppresses normal retinal vascular development, leading to vaso-obliteration (VO) and subsequent pathological neovascularization (NV) in ischemic areas. This neovascular formation represents the second phase of ROP (Phase II ROP), which can cause severe visual impairment or even blindness.

Current treatments for ROP mainly include laser photocoagulation and intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) drugs. However, these treatments have significant limitations: laser photocoagulation destroys avascular retinal areas, while anti-VEGF therapy is not only costly but also carries a risk of neovascular recurrence, and the drug may persist in the systemic circulation for an extended period, potentially inhibiting vascular development in other organs. Therefore, there is an urgent need to develop effective, economical, and safe preventive treatments for ROP.

Dexamethasone, a glucocorticoid agonist, has shown some efficacy in inhibiting retinal neovascularization, but its specific mechanisms remain unclear. Additionally, the route, timing, and dosage of dexamethasone administration significantly impact its effectiveness. Topical dexamethasone eye drops are globally accessible and more convenient to administer compared to laser and intravitreal injections. Thus, investigating the role of dexamethasone eye drops in preventing ROP holds significant clinical importance.

Research Team and Publication Information

This study was conducted by a team of scholars from several internationally renowned institutions, with primary authors including Ann Hellström and Lois E.H. Smith. The research team is affiliated with Boston Children’s Hospital, Harvard Medical School, Keio University School of Medicine, the University of Freiburg Medical Center, and the University of Gothenburg, among others. The study was published online on September 17, 2024, in the journal Angiogenesis, titled Timed Topical Dexamethasone Eye Drops Improve Mitochondrial Function to Prevent Severe Retinopathy of Prematurity.

Research Process and Methods

The study was divided into preclinical research and animal experiments, aiming to explore the role and mechanisms of dexamethasone eye drops in preventing ROP.

Preclinical Research

The research team first conducted a prospective clinical study evaluating the use of 0.1% dexamethasone eye drops in five extremely preterm infants (gestational age 22 to 27 weeks). These infants were all in Type 2 ROP (Stage 3, Zone II) without “plus disease” (i.e., retinal vascular dilation and tortuosity). Dexamethasone eye drops were administered before the progression to severe ROP, and the results showed that none of the five infants progressed to Type 1 ROP, and none required laser or anti-VEGF treatment.

Animal Experiments

To further investigate the mechanisms of dexamethasone, the research team used the Oxygen-Induced Retinopathy (OIR) mouse model. The OIR model induces retinal vaso-obliteration and subsequent neovascularization by exposing newborn mice to a 75% hyperoxic environment. The team administered 0.1% dexamethasone eye drops at different time points (P12-P14, P14-P16, P17-P19) and assessed its impact on neovascularization.

Experimental Methods

1. OIR Model Establishment and Evaluation: Newborn mice were exposed to a 75% hyperoxic environment from P7 to P12, then returned to room air. Retinal vascular staining and image analysis were used to quantify the areas of retinal neovascularization and vaso-obliteration.
2. Dexamethasone Eye Drop Treatment: Mice were administered 0.1% dexamethasone eye drops daily during three periods: P12-P14, P14-P16, and P17-P19, with the control group receiving phosphate-buffered saline (PBS).
3. Proteomics Analysis: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze protein expression changes in P17 mouse retinas to explore the mechanisms of dexamethasone.
4. Mitochondrial Function Assessment: Real-time quantitative PCR (RT-qPCR) was used to detect the expression of mitochondrial-related genes, and the mitochondrial ATP synthase inhibitor oligomycin was used to assess the impact of mitochondrial function on neovascularization.

Main Research Findings

Clinical Research Results

In the five extremely preterm infants, the use of dexamethasone eye drops successfully prevented the progression of ROP and promoted normal retinal vascular development. None of the infants developed severe ROP, and none required laser or anti-VEGF treatment. These results suggest that dexamethasone eye drops have potential applications in preventing ROP.

Animal Experiment Results

1. Time-Dependent Effects of Dexamethasone Eye Drops: In the OIR mouse model, dexamethasone eye drops administered during P14-P16 (before the peak of neovascularization) significantly inhibited neovascularization at P17, with an inhibition rate of 30%. Administration during P12-P14 had a weaker effect, while administration during P17-P19 showed no significant effect and may even exacerbate neovascularization.
2. Role of Mitochondrial Function: Proteomics analysis revealed that dexamethasone eye drops significantly increased the expression of mitochondrial-related genes in the retina and reduced the expression of inflammatory markers. Inhibition of mitochondrial ATP synthase reversed the inhibitory effect of dexamethasone on neovascularization, indicating that mitochondrial function plays a key role in the anti-angiogenic effects of dexamethasone.
3. Relationship Between Inflammation and Neovascularization: Dexamethasone eye drops significantly reduced the expression of pro-inflammatory factors (e.g., TNF, IL-1β, IL-6) and pro-angiogenic factors (e.g., EPO) in OIR mouse retinas but had no significant effect on VEGF expression. This suggests that dexamethasone may inhibit neovascularization by modulating inflammatory responses.

Research Conclusions and Significance

This study is the first to reveal that dexamethasone eye drops inhibit pathological neovascularization in ROP by improving mitochondrial function. The results demonstrate that dexamethasone eye drops administered before the peak of neovascularization can significantly inhibit neovascular formation and promote normal retinal vascular development. This finding provides new strategies for the prevention and treatment of ROP, especially in resource-limited regions, where dexamethasone eye drops offer a simple and economical treatment option.

Furthermore, this study highlights the important role of mitochondrial function in ROP, providing new insights into the relationship between mitochondria and retinal vascular diseases. Modulating mitochondrial function may offer new approaches for treating other retinal vascular diseases.

Research Highlights

1. Time-Dependent Effects: The study found that the efficacy of dexamethasone eye drops is time-dependent, with the optimal timing being before the peak of neovascularization.
2. Modulation of Mitochondrial Function: The study is the first to reveal that dexamethasone inhibits neovascularization by improving mitochondrial function, offering a new direction for ROP mechanism research.
3. Potential for Clinical Application: Dexamethasone eye drops, as a simple and economical treatment, have broad clinical application prospects, particularly in resource-limited regions.

Summary

Through preclinical research and animal experiments, this study systematically explored the role and mechanisms of dexamethasone eye drops in preventing ROP. The results demonstrate that dexamethasone eye drops effectively inhibit pathological neovascularization by improving mitochondrial function and suppressing inflammatory responses. This finding provides new strategies for the prevention and treatment of ROP, holding significant scientific and clinical value.