Abstract 1851: A murine model of von Hippel-Lindau associated retinal hemangioblastoma

Purpose: von Hippel-Lindau disease (VHL) is an autosomal dominant condition that features a constellation of cysts or highly vascularized tumors due to loss of heterozygosity (LOH) of the VHL gene, resulting in deregulated hypoxia-induced factors (HIFs). Clinical manifestations of VHL include hemangioblastomas in the central nervous system and retina. To date, no VHL animal model has reproduced retinal capillary hemangioblastomas (RCH), the hallmark lesion of ocular VHL. The RCHs may arise from arrested hemangioblast progenitor cells, with VHL LOH in the tumor stroma. The stem cell leukemia (SCL) gene encodes a basic helix-loop-helix (bHLH) transcription factor, a critical regulator of hematopoiesis and vasculogenesis. We aim to generate a murine model of VHL-associated RCH by conditionally inactivating Vhl in a hemangioblast progenitor population with the angioblast-specific Cre line, (SCL) Cre-ERt2. Methods: We established a genetic mouse model in which the inducible Vhl gene is specifically “knocked-out” in angioblast cells using the stem cell leukemia (SCL) Cre-ERt2 transgenic mice. Two-week-old SCL-CreERt2;Vhl-F/F mice were administrated tamoxifen (2mg/40g body weight) for 5 consecutive days to activate the Cre recombinase that induces Vhl deletion in angioblast-derived cells. Fundoscopy was done monthly to detect retinal lesions. Fluorescein angiography (FA) was performed on affected mice. All retinas were analyzed by histology at 4 months of age. Genome typing of the Vhl conditional KO allele was conducted in retinal lesions using microdissection, nest-PCR and Sanger sequencing. Results: About 64% (18/28) of the transgenic mice exhibited various retinal vascular defects following induction. Affected mice demonstrated retinal vascular lesions that were variably associated with prominent vessels, anomalous capillary networks, hemorrhage, exudates, and localized fibrosis. FA revealed vascular leakage from the lesions. Histological analyses showed RCH-like lesions of tortuous, dilated vessels surrounded by “tumorlet” cells, isolated foamy stromal cells, and glia, classically found in RCH. Vhl LOH was detected in the tumor-like area as verified by sequencing. Conclusion: This is the first demonstration of VHL-associated RCH in a transgenic mouse model. This model may be useful for studying RCH pathogenesis, including HIF-dependent and HIF-independent pathways, and for testing potential therapies. Citation Format: Herui Wang, Qi Zhang, Lijin Dong, Liliana