Conjunctival Fibrosis after Application of Mitomycin C: An Animal Experimental Study

Anti-fibrosis potential of pirarubicin via inducing apoptotic and autophagic cell death in rabbit conjunctiva

This study investigated the potential efficacy of pirarubicin (THP) in modulating rabbit conjunctival fibrosis both in vitro and in vivo and characterized the underlying mechanisms. Primary rabbit conjunctival fibroblasts (RCF) were cultured and treated with THP or mitomycin C (MMC) for 5 min, followed by assaying for cell viability, cell cycle distribution, apoptotic and autophagic pathways. The production of reactive oxygen species (ROS) and chemotaxis of macrophages by RCF were evaluated using 2',7'-dichlorofluorescein diacetate (DCFH-DA) labeling and transwell migration assay, respectively. Limbal stem cell excision in combination with alkali burn was performed on the rabbits to establish a model of limbal deficiency and conjunctival fibro-vascular invasion. After three months, the modeled fibro-vascular tissue was excised combined with topical subconjunctival 5-min exposure to THP compared with MMC intraoperatively. The recurrence of postoperative fibrosis and the expression of apoptosis, autophagy, and inflammation markers were evaluated by immunohistochemistry. All modeled rabbits developed conjunctival fibro-vascular lesions, which were similar to human recurrent pterygium (HRP). Both THP and MMC inhibited RCF proliferation and arrested cell cycle at the G0/G1 phase. In particular, 7.5 μmol/L THP remarkably promoted RCF autophagy by upregulating the levels of Beclin 1, Atg 5/12 conjugate, and LC3B, whereas, 15 μmol/L THP significantly triggered a cascade of mitochondrial-associated RCF apoptosis. THP induced the production of ROS and enhanced the chemoattraction of macrophages by RCF. Similar to 600 μmol/L MMC, both 7.5 μmol/L and 15 μmol/L THP attenuated postoperative conjunctival fibrosis in the models; 7.5 μmol/L THP preferentially enhanced autophagy while causing fewer side effects. THP exerted its antifibrotic action by modulating autophagy in RCF, inducing cell cycle arrest, and mitochondrial-mediated apoptosis. THP at the dose of 7.5 μmol/L prevented postoperative conjunctival fibrosis in an animal model.

Effect of human RAD50 gene therapy on glaucoma filtering surgery in rabbit eye

PURPOSE

To investigate the antiproliferative effects of the subconjunctival injection of human RAD50 (hRAD50) on fibroblasts after glaucoma filtering surgery.

METHODS

After glaucoma filtering surgery in normal rabbit eye, the subconjunctival injection of hRAD50 was performed. Morphologic changes in the subconjunctival area of hRAD50-treated eyes were compared with those of mitomycin C (MMC)-treated and control eyes using light and electron microscopy. Results. Two weeks after hRAD50 treatment (2 microg), the conjunctival epithelium increased in thickness and had many tonofilaments, but the basal lamina was intact. The subconjunctival fibroblasts exhibited a granular endoplasmic reticulum without distension. Most of the collagen bundles and fibers around the fibroblasts disappeared, and apoptotic cells with many fragmented nuclei and condensed chromatin were observed. Four weeks after hRAD50 treatment, the findings were similar with those of 2 weeks except for a slight increase in the number of collagen bundles and fibers and the appearance of macrophages. In MMC-treated eyes, the conjunctival epithelium also increased in thickness and had many tonofilaments. However, intercellular spaces were widened and the basal lamina was interrupted in some areas. Most of the collagen bundles and fibers were shortened, and apoptotic cells were also observed.

CONCLUSIONS

These results demonstrate that the histologic antiproliferative effects of local hRAD50 on the conjunctival fibroblasts are similar to those of MMC, but without damage to the basal lamina of the conjunctival epithelium, and suggest that hRAD50 may be useful as a possible antifibroblastic agent for glaucoma filtering surgery. However, further investigations are needed to test for possible systemic complications, which so far have not been reported.