Heterozygous Mutation of Vegfr3 Reduces Renal Lymphatics without Renal Dysfunction

Significance Statement Defects in renal lymphatics occur in various kidney diseases, but the role of the lymphatics in maintaining kidney structure and function is unknown. We combine tissue clearing, light-sheet microscopy, and computational analysis to characterize lymphatics and find that mice with a heterozygous mutation in Vegfr3 (Vegfr3(Chy/+)) have severely reduced renal lymphatics. Strikingly, these mice have indistinguishable renal function and histology compared with controls. Even after low-dose cisplatin injury, there are no differences in renal function, although Vegfr3(Chy/+) mice developed more perivascular inflammation. Our data present a novel method of lymphatic quantification and suggest that a normal complement of renal lymphatics is not essential for renal structure and function at baseline or after mild injury. Background Lymphatic abnormalities are observed in several types of kidney disease, but the relationship between the renal lymphatic system and renal function is unclear. The discovery of lymphatic-specific proteins, advances in microscopy, and available genetic mouse models provide the tools to help elucidate the role of renal lymphatics in physiology and disease. Methods We utilized a mouse model containing a missense mutation in Vegfr3 (dubbed Chy) that abrogates its kinase ability. Vegfr3(Chy/+) mice were examined for developmental abnormalities and kidney-specific outcomes. Control and Vegfr3(Chy/+) mice were subjected to cisplatin-mediated injury. We characterized renal lymphatics using tissue-clearing, light-sheet microscopy, and computational analyses. Results In the kidney, VEGFR3 is expressed not only in lymphatic vessels but also, in various blood capillaries. Vegfr3(Chy/+) mice had severely reduced renal lymphatics with 100% penetrance, but we found no abnormalities in BP, serum creatinine, BUN, albuminuria, and histology. There was no difference in the degree of renal injury after low-dose cisplatin (5 mg/kg), although Vegfr3(Chy/+) mice developed perivascular inflammation. Cisplatin-treated controls had no difference in total cortical lymphatic volume and length but showed increased lymphatic density due to decreased cortical volume. Conclusions We demonstrate that VEGFR3 is required for development of renal lymphatics. Our studies reveal that reduced lymphatic density does not impair renal function at baseline and induces only modest histologic changes after mild injury. We introduce a novel quantification method to evaluate renal lymphatics in 3D and demonstrate that accurate measurement of lymphatic density in CKD requires assessment of changes to cortical volume.

Automated summary

Defects in renal lymphatics occur in various kidney diseases, but the role of lymphatics in maintaining kidney structure and function is unknown. Using novel techniques, researchers found that reduced renal lymphatic density does not impair renal function at baseline and results in only modest histologic changes after mild injury. The study introduced a new method for quantifying renal lymphatics in 3D and emphasized the importance of assessing changes in cortical volume for accurate measurement of lymphatic density in chronic kidney disease.