Immunohistochemical characterisation of surgically excised choroidal neovascularisations in age-related macular degeneration

Aim The objective of the study was to gather further information about the pathogenesis of choroidal neovascularisations (CNV), which is still not cle arly understood, and to establish criteria for making decisions on a approp riate therapy. Immunohistochemical characterisation should allow a more com prehensive evaluation of cellular components of the membranes and their fun ctional role. Patients and methods In 29 patients (16 women, 13 men) with age-related mac ular degeneration ranging in age from 46 to 91 years (mean age, 76.4 years) , CNV were excised by pars-plana vitrectomy. Sections were stained with hem atoxylin-eosin (HE) and periodic acid-Schiff (PAS) and examined by light mi croscopy. For the immunohistochemical characterisation of the surgical spec imens the following antigenetic determinants were used: glial fibrillary ac id protein (GFAP) for glial cells, synaptophysin for neuronal cells, neuron -specific enolase (NSE) for neuronal and neuroectodermal cells, CD 31 for e ndothelial cells and pancytokeratin (KL1) for cells of the retinal pigment epithelium (RPE). Cells undergoing apoptosis were labeled with the TUNEL te chnique. Results 22 (76%) surgical specimens showed TUNEL positive cells in the conn ective tissue, vascular endothelium and retinal pigment epithelium. Positiv e immunostaining of neuronal antigenetic determinants was found for glial f ibrillary acid protein in 22 patients (76%), for synaptophysin in 28 patien ts (97%) and for neuron-specific enolase in 21 patients (72%) CNV. The epit helial marker KL1 was positive in 28 patients (97%) and the endothelial mar ker CD 31 in 20 patients (69%). Conclusion The immunohistochemical analyses of CNV showed that in the major ity of cases during the excision of choroidal neovascularizations in additi on to scar tissue and connective tissue also parts of the native retinal pi gment epithelium and of the neurosensory retina are removed which is only p artly visible with standard staining techniques. These findings suggest tha t the mostly not satisfying postoperative results are partly due to the dam age of neuronal cells and a partial loss of the retinal pigment epithelium. Apoptosis as a regulating mechanism in choroidal neovascularization. The v ariable appearence of apoptosis suggests that it is possibly related to the degree of activity of CNV.