Abstract
Purpose: :
To develop a robust method of CNV induction in rabbits by suprachoroidal technique, without physical breakage of Bruch’s membrane.
Methods: :
Growth factors were delivered into a posterior pole position of the OD suprachoroidal space in chinchilla rabbits by means of a modified irrigation handle, introduced into the suprachoroidal space through a 3 o'clock paralimbal sclerotomy. Growth factors were either 1) 1 mm3 Hydron/Sucralfate implants containing 20/15 µg bFGF/VEGF or 2) 0.5 x 105 homologous RPE and 0.5 x 105 Dynabeads in 50 µl PBS. The irrigation handle was used with either a stylet for implantation, or a PE 8 catheter attached to a 50 µl Hamilton syringe for injection. The resulting pathology was evaluated by IHC 1-3 weeks after surgery. IHC was performed on OCT embedded cryo sections. Angiogenesis was visualized by αvβ3 expression with MAB1976, secondary IgG/biotin and Avidin/AP with Vector Red.
Results: :
No breach of the RPE or angiogenesis anterior thereof was observed in any of the animals.After sucralfate implantation, marked granulomatous infiltration and minimal expression of αvβ3 and features of angiogenesis were observed 1-3 weeks after implantation in OD. OS was normal. The cellular infiltrate contained remnants of implant material surrounded by macrophages, lymphocytes, multinuclear giant cells and beginning fibrosis.After RPE/Dynabead injection, moderate-markedly increased expression of αvβ3 and marked presence of macrophages and collagen in the choroidal space were observed 11 days after injection in 11 of 12 OD. CNV was observed in 9 of 12 OD. Minimal-moderately increased expression of αvβ3, but no CNV and minimal-moderate presence of macrophages and collagen, was observed in the choroidal space in 7 of 7 OS.
Conclusions: :
Our model of suprachoroidal RPE/Dynabead injection is appropriate to initiate increased expression of choroidal αvβ3, macrophages and collagen and increased CNV, without physical breakage of Bruch’s membrane. These pathological changes are consistent with early inflammatory/degenerative lesions of the choroid and Bruch’s membrane in early stage AMD. Further characterization of the suprachoroidal RPE/Dynabead model is warranted. The marked and predominantly granulomatous infiltration of the Sucralfate implants and the modest degree of angiogenesis was a surprising finding that warrants a review on the use of such implants in various ocular models.
Keywords: choroid: neovascularization • pathology: experimental • growth factors/growth factor receptors