Whole mount of adult ear skin as a model to study vascular malformations.

Background: Genetic analysis in human patients has linked mutations in PIK3CA, the catalytic subunit of PI-3'Kinase, to sporadic incidences of vascular malformations.

Methods: We have developed a mouse model with inducible and endothelial-specific expression of PIK3CA , resulting in the development of vascular malformations. Systemic induction of this mutation in adult mice results in rapid lethality, limiting our ability to track and study these lesions; therefore, we developed a topical and local induction protocol using the active metabolite of tamoxifen, 4OH-T, on the ear skin of adults.

Results: This approach allows us to successfully model the human disease in a mature and established vascular bed and track the development of vascular malformations. To validate the utility of this model, we applied a topical rapamycin ointment, as rapamycin is therapeutically beneficial to patients in clinical trials. We found that the induced ear lesions showed significant attenuation after treatment, which was easily quantified.

Conclusions: These data collectively provide evidence of a new model to study vascular malformations in adult tissues, which should be particularly useful in environments lacking specialized small-animal imaging facilities.