Outflow tract ablation using a conditionally cytotoxic feline immunodeficiency viral vector.
OBJECTIVE
To create an in vivo model of vector-mediated trabecular meshwork (TM) ablation and replacement.


METHODS
We generated a conditionally cytotoxic, trackable vector, HSVtkiG, that expressed herpes simplex virus 1 thymidine kinase (HSVtk) and enhanced green fluorescent protein (eGFP). We optimized HSVtkiG ablation in vitro with ganciclovir (GCV) in comparison to eGFP control vector GINSIN and investigated the mechanism. Right eyes of 24 rats were then injected intracamerally with either HSVtkiG or GINSIN, before intraperitoneal GCV was administered 1 week later. Intraocular pressure, central corneal thickness (CCT), and slit-lamp exams were assessed for 8 weeks. Transduction and ablation were followed by gonioscopic visualization of eGFP. Histology was obtained with TM cell counts and immunohistochemistry markers of inflammation.


RESULTS
Transduction and ablation parameters were established in vitro. Apoptosis was the cause of cell death. In vivo, transduction was seen gonioscopically to be targeted to the TM, followed by disappearance of eGFP marker fluorescence in HSVtkiG-transduced cells after injection of GCV. Ablation resulted in an IOP decrease of 25% in HSVtkiG-injected eyes 2 days after GCV but not in GINSIN or noninjected control eyes (P < 0.05). Trabecular meshwork cellularity was decreased at the time of lowest IOP and recovered thereafter, while CCT remained unchanged. Inflammation was absent.


CONCLUSIONS
A vector-based system for inducible ablation of cells of the outflow tract was developed. Trabecular meshwork ablation lowered IOP, and recovery of cellularity and IOP followed. This model may be useful to study pressure regulation by the TM, its stem cells, and migration patterns.
Yale University School of Medicine, New Haven, Connecticut.
Ze
Z
Zhang
Amardeep S
AS
Dhaliwal
Harry
H
Tseng
James D
JD
Kim
Joel S
JS
Schuman
Robert N
RN
Weinreb
Nils A
NA
Loewen
D000818:Animals; D000867:Anterior Chamber / Q000821:virology; D000998:Antiviral Agents / Q000494:pharmacology; D016590:Aphidicolin / Q000494:pharmacology; D001082:Aqueous Humor / Q000378:metabolism; D002460:Cell Line; D005260:Female; D015774:Ganciclovir / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D016089:Immunodeficiency Virus, Feline / Q000235:genetics*; D056965:Injections, Intraocular; D007429:Intraocular Pressure / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014129:Trabecular Meshwork / Q000378:metabolism*; D014161:Transduction, Genetic
D000998:Antiviral Agents; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D016590:Aphidicolin; D015774:Ganciclovir
ablation; gene therapy; glaucoma; trabecular meshwork