Abstract
Purpose :
Intraocular sustained release bimatoprost and topically applied prostaglandin analogues can have a sustained IOP lowering effect long after the pharmacologic half-life is expired. Although the role of matrix metalloproteinases (MMPs) and their kinetic inhibitors (TIMPs) are well-established acute effects, it is unclear if the MMP and TIMP balance is the sole mechanism. Monkeys treated with topical bimatoprost for one year have partially endothelial lines with empty spaces within the ciliary body stroma. In 2009, Yucel et al. described a potential uveolymphatic pathway for drainage of aqueous humor from the anterior chamber of the eye and regulation of IOP. The goal of this study is to further investigate the mechanism of the sustained hypotensive effect of bimatoprost. We hypothesized that bimatoprost induces lymphangiogenesis.
Methods :
We sought the presence and relative change of several markers associated with lymphangiogenesis. We treated primary cultures of human ciliary body smooth muscle (CBSM) cells with therapeutic dosages of bimatoprost free acid for 72 hrs. Protein and mRNA from cell lysates were harvested for immunoblotting and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), respectively. Wild type BL6-SVJ129 mice received topical Lumigan in one eye; eyes that experienced an IOP decrease were harvested and fixed with formaldehyde for immunohistochemistry. Fold-changes in the expression of the lymphatic markers ANG-1, ANG-2, LYVE-1, NRP-2, PDPN, PROX-1, and TIE-1 in the treatment groups as compared to the control groups were calculated and two-tailed paired t-tests with significance set at p < 0.05 were used for statistical analysis.
Results :
In human CBSM cells, the markers LYVE-1, TIE-1, and ANG-1 were increased by bimatoprost free acid by 20% (p=0.03, n=8), 31% (p=0.004, n=7), and 20% (p<0.05, n=8), respectively. qRT-PCR showed an increase of ANG-1 (p=0.02, n=8) mRNA. Immunohistochemistry of bimatoprost treated mouse eyes preliminarily demonstrated an increase in TIE-1 (p=0.05, n=3) within the ciliary body stroma.
Conclusions :
We have validated the presence of lymphatics in the ciliary body. Induction of lymphangiogenesis may be a mechanism of sustained IOP reduction from bimatoprost. To our knowledge, induction of lymphangiogenesis from a small molecule has not been previously reported.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.