Targeted gene transfer to Schlemm's canal by retroperfusion

The goal of the present study was to specifically modify protein expression in the resistance-generating region of the conventional outflow pathway, namely the inner wall of Schlemm's canal (SC) and the juxtacanalicular region of the trabecular meshwork, in perfused human anterior segments. Anterior segments from human cadaveric eyes were prepared for organ culture using standard techniques and were perfused at constant flow while recording pressure. After reaching a stable outflow facility within physiological limits, forward perfusion was stopped and a fluid-tight fence encircling the limbus was installed and filled with media containing an adenovirus encoding the lacZ reporter gene (either 2 × 106 or 6 × 106 PFU/ml). With the limbus submerged, pressure inside the chamber was lowered to −1 mmHg to facilitate reverse perfusion of virus into SC (“retroperfusion”). After 30–60 min at zero pressure (with some mixing), forward perfusion was restarted and continued for 5–7 days, after which anterior segments were fixed and processed for visualization of lacZ activity. Retroperfusion of nine anterior segments with adenovirus encoding a reporter gene did not appreciably alter baseline outflow facility (0.27 ± 0.05 versus 0.29 ± 0.08 μl/min per mmHg post-retroperfusion). Gross examination of outflow tissues showed focal distribution of lacZ activity around the circumference of SC, presumably near collector channels. In segments that were sequentially tilted during retroperfusion, the distribution of lacZ activity appeared more uniform. Sagittal histological sections showed lacZ activity in all portions of the conventional drainage tract, particularly cells in the resistance-generating region. Taken together, the results demonstrate that candidate protein expression by cells in the resistance-generating region of the conventional drainage pathway can be specifically modified by retroperfusion of adenovirus and examined for effects on outflow facility.