Aquaporins (AQPs) are ubiquitously expressed throughout the human body. AQP1 and AQP4 have an extremely regulated distribution in the central nervous system (CNS), where they play important roles in cerebrospinal fluid production and absorption and the regulation of blood-brain barrier water permeability. Recent studies have reported a relationship between astrocytoma malignancy and the abnormal expression of AQPs in the CNS, particularly AQP1 and AQP4.1,2 These water channel proteins are highly expressed in malignant astrocytomas,3,4 and a positive correlation is observed between their expression levels and histological tumor grade.5,6 Both AQPs have significant roles in mesenchymal microvascular proliferation and infiltrative growth.6-10 Indeed, malignant astrocytoma is characterized by microvascular proliferation and diffuse, infiltrative growth, tumor characteristics that are believed to promote tumor progression and portend a poor prognosis. Therefore, the evaluation of both the AQPs’ expression in malignant astrocytoma patients in vivo would lead to an early diagnosis of malignancy and an accurate evaluation of the extent of malignant tumor regions. However, real-time in vivo visualization of AQPs in brain tumor has not been reported previously.
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