Anti-scarring effect of rapamycin following filtering surgery in rabbit eyes / 南方医科大学学报

OBJECTIVE@#To study the effect of rapamycin on scar formation in rabbit eyes following filtering operation and explore the possible mechanism.@*METHODS@#Ninety-six healthy adult rabbits were subjected to trabeculectomy of the left eye and subsequently randomly divided into 4 groups (=24) for treatment with castor oil (control) or rapamycin (1%, 3%, or 5%) eye drops of the operated eyes 4 times a day. The morphology and function of the filtering blebs of the rabbits were compared at 7, 14, 21 and 28 days after the operation; at each of the time points, 6 rabbits from each group were euthanized for detection of expressions of proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) in the tissues in the surgical area using immunohistochemistry. Cultured rabbit subconjunctival fibroblasts (RTFSs) were treated with different concentrations of rapamycin (0.06, 0.25, 1, and 4 mg/L) and the cell apoptosis was detected using flow cytometry.@*RESULTS@#In the first, second and third weeks after the operation, the rate of functional follicle formation was significantly higher in the 3 rapamycin groups than in the control group ( < 0.05), and the number of α- SMA-positive fibroblasts decreased over time in the 3 rapamycin groups. In cultured RTFSs, treatment with rapamycin at different concentrations resulted in increased apoptosis of the cells, and rapamycin above 0.25 mg/L significantly increased the cell apoptosis in a dose-dependent manner.@*CONCLUSIONS@#Rapamycin can inhibit hyperplasia of the filtering passage tissue, helps to preserve the functional filtering blebs and prolong their life span, and induces apoptosis of RTFS.

Use of Tissue Adhesive for Prevention of Fibrotic Breakdown of Filtration Bleb

In this experiment using 30 rabbits(40 normal eyes), the applicability of ocular adhesive, HISTOACRYL blue, as an implant beneath the scleral and conjunctival flap. Group 1 consisted of 10 left eyes. These eyes had undergone a fornix-based conjunctival flap and a triangular lamellar scleral flap without sclerectomy and served as a control on histologic examination. Group 2 consisted of 10 right eyes of the rabbits used in group 1. The Histoacryl was pasted on the sclera under the lamellar scleral flap and the conjunctiva. The pasted Histoacryl turned into a thin membrane. Group 3 consisted of 10 right eyes which had undergone a conventional trabeculectomy. Group 4 consisted of 10 right eyes. These eyes had undergone a trabeculectomy and placement of a Histoacryl membrane. The adhesive was applied closely to the limbus in 5 eyes and posteriorly away from the limbus in the remaining 5 eyes of group 4. At the eighth week after operation a filtering bleb was observed in all of the eyes in group In contrast to this, only two eyes showed filtering blebs in group 3. Filtering blebs were so confined over the Histoacryl membrane that their size and location was in accordance with the membrane. The vessels of the conjunctiva overlying the Histoacryl membrane were dilated and congested. This vascular congestion lasted long. The light microscopic examinations of the operation site showed a thick layer composed of macrophages, eosinophils, neutrophils, foreign body giant cells, and fibroblasts surrounding the Histoacryl membrane with cystic space between them. At the eight postoperative week, this wall remained thick measuring about 50-70 micro thick. From the result, Histoacryl appeared to be effective in preventing the fibrotic scarring down of the filtering bleb, but postoperative inflammatory changes indicated that the Histoacryl seemed to be rather unsuitable for clinical application.

A membranous drainage implant in glaucoma filtering surgery: animal trial

This experiment used 30 rabbits (40 normal eyes) to determine the applicability of an expanded polytetrafluoroethylene (e-PTFE) surgical membrane as a glaucoma seton. The e-PTFE membrane had 0.1 mm thickness and was cut into T-shaped pieces measuring about 2x7 mm. One end of the implant was introduced into the anterior chamber through a sclerectomy opening and the other ends were allowed to extend from the Iamellar scleral flap into the subconjunctival space. During the follew-up at the end of 8 weeks, all the eyes with an implant showed an apparent filtering bleb, while only one of 6 eyes that had undergone a trabeculectomy alone did. The location of the created filtering blebs depended on the implant position. Pestoperative inflammatory changes were unremarkable. Histologic examinations reyealed a tissue-free cystic space surrounding the e-PTFE implants which maintained their original color, thickness, pliability and size. Transmission electron microscopy showed few myofibroblast-like cells in the fibrous wall containing the implant. With scanning electron microscopy, the internal end of the implant strip had a clean surface and no adhesions to adjacent structures of the anterior chamber angle. The corneal endothelial cells were intact in the area close to the tip of the implant. Considering the clinical and histologic findings, it appeared that the e-PTFE was acceptably innocuous in the anterior segment of the eye and a convenient material as a glaucoma seton.