Effects of Ascorbic Acid on Cataract Formation in in vitro Porcine Lenses

Abstract

Purpose : The concentration of ascorbic acid (AA) in the vitreous humor is considerably higher than that of blood or other tissues. Vitrectomy is associated with high incidence of subsequent cataract, potentially due to the loss of anti-oxidant capacity. This study evaluated potential protective effects of addition of AA to the culture environment of whole porcine lenses.

Methods : Pairs of lenses were removed from freshly acquired eyes and cultured in 4 different normoxic environments containing M199 cell culture media, M199 with 365 mg/mL of AA, M199 with the vitreous humor of the eye, and M199 with both vitreous humor and 365 mg /mL of AA. AA concentration was matched to values reported in prior research on theconcentration of AA in samples of human vitreous humor.Paired lenses were cultured under similar conditions but with one lens exposed to the additional AA. Media was refreshed every 24 hours during culture to maintain constant levels of AA. Lenses were removed at various time points between 12 hours and 8 days and examined in a series of 5 experimental assays of optical, biochemical, and biomechanical properties. Lenses were first photographed to measure opacity, and then analyzed in a mechanical spinning and compression test. The nucleus of each lens was then removed and tested in Raman spectroscopy and shear rheometry.

Results : In 8 pairs incubated with the vitreous humor and in 2 pairs incubated without vitreous the lens in each pair that was subject to additional AA had a lower elastic moduli when measured with rheometry at 0.1 Hz. Pilot data suggest that elastic moduli increased with incubation times and AA showssome reduction in this progression.

Conclusions : These findings support the hypotheses that higher levels of AA found naturally in the vitreous humor may have a protective effect on the aging lens, especially with regard tocataract formation in in the lens. Incubating lenses in the presence of additional AA reduced lens degradation over time and resulted in softer lenses with lower elastic moduli. Incorporation of AA into vitreous substitutes could reduce the incidence of postoperative cataract formation and benefit long term lens health.

This is a 2020 ARVO Annual Meeting abstract.

 

The elastic shear modulus tended to increase with incubation time in the absence of supplemental AA. The addition of AA was protective against this stiffening.