Dose-dependent myopia-suppressing effect of 4-phenlybutyric acid eye drops in a mouse myopia model under masked condition

BACKGROUND: Myopia, characterized by excessive axial elongation of the eyeball, has become a significant global public health issue, particularly in Asia. Severe myopia increases the risk of ocular complications, including retinal degeneration and glaucoma. Recent studies have identified the role of scleral extracellular matrix remodeling and endoplasmic reticulum (ER) stress in myopia pathogenesis. Our previous study identified scleral ER stress as a critical factor in myopia development. This study aimed to investigate the therapeutic potential of 4-phenylbutyric acid (4-PBA), a chemical chaperone, in mitigating scleral ER stress and its effects on myopia progression in a mouse myopia model under masked condition. METHODS: A lens-induced myopia (LIM) mouse model was utilized to evaluate the effects of 4-PBA administered as eye drops. Mice received varying concentrations of 4-PBA or phosphate-buffered saline (PBS) as a control. Changes in refractive error and axial length were measured to assess myopia progression. In addition, further experiments were also conducted under masked conditions, where the experimenter was unaware of the treatment was being applied, for the three conditions of 2%, 0.5% 4-PBA eye drops or vehicle treatment of LIM mice. RESULTS: Administration of 4-PBA at concentrations of 0.5% and higher significantly suppressed the myopic shift in refraction and axial elongation associated with myopia compared to mice in the PBS control group. In a blinded, masked experiment, 2% and 0.5% 4-PBA eye drops also suppressed the progression of myopia in a dose-dependent manner. CONCLUSIONS: This study demonstrated that 4-PBA effectively mitigated myopia progression in a mouse model by targeting scleral ER stress. The dose-dependent suppression of myopic shifts and axial elongation under masked experimental condtion highlights the potential of 4-PBA as a therapeutic agent for managing myopia. These findings pave the way for further research and potential clinical applications in myopia treatment.