Ionizing radiation (IR) isthe primarytherapeutic tool to treat patients with cancerous lesions located in the head and neck. In many patients, IR results in irreversible and severe salivary gland dysfunction or xerostomia. Currently there are no effective treatment options to reduce the effects of xerostomia. More recently, salivary gland gene therapy utilizing the water-specific protein aquaporin 1 (AQP1) has been of great interest to potentially correct salivary dysfunction. In this study, we used CRISPR-Cas9 gene editing along with the endogenous promoter of AQP1 within theHEK293 and MDCK cell lines. The successful integration of the cytomegalovirus (CMV) promoterresultedin a significant increase of AQP1 gene transcription and translation. Additionalfunctional experiments involvingthe MDCK cell line confirmedthat over-expressed AQP1increasedtransmembrane fluid flux indicative of increased intracellular fluid flux. The off-target effect of designed guided RNA sequence was analyzed and demonstrateda high specificity for the Cas9 cleavage. Considering the development of new methods for robust DNA knock-in, our results suggest that endogenous promoter replacement may be a potential treatment forsalivary gland dysfunction.