KAI is a pharmacological inhibitor for VEGFR2 trafficking in vitro.
11 On the other hand, knockdown of KIF13B inhibits VEGFR2 trafficking and VEGF-induced angiogenesis in vitro.
12 Thus, in this article, we used both pharmacological inhibitor and genetic deletion to confirm the effect of the inhibition of KIF13B -mediated VEGFR2 trafficking in laser-induced CNV. The CNV in
KIF13BKO was significantly reduced compared to
WT control (
Figs. 4A–
4D). KIF13B global KO was characterized as no gross anomalies and no apparent changes in the major organs.
40 We have also examined the histology of the eyes of
KIF13BWT and
KIF13BKO by staining with VEGFR2, ILB4, GAD65, glutamine synthase, and rhodopsin (
Supplementary Fig. S3C), and the fundus image before applying laser burn (
Fig. 4A), but we did not see any difference between
KIF13BKO and
KIF13BWT. The structural change (for example, if there is any difference in the thickness of the Bruch's membrane) may affect the effectiveness of the laser burn; however, it is not likely the case, because we could not find any difference in
KIF13BWT and
KIF13BKO. Thus the inhibition of CNV seen in
KIF13BKO was not likely due to any developmental difference before the laser burn. After the laser burn, we observed that the disease progression was significantly less in
KIF13BKO. The disease progression in this model can be divided; early upregulation of VEGF from damaged tissue at day 3, leakage from the choroid to the retina at day 3,
46 inflammation and accumulation of neutrophils at days 1 to 3, and macrophages at days 3 to 5,
29 CNV and leakage at CNV lesion peaked at day 7.
29 We observed the mice at days 7 and 14 when the CNV was fully developed in control mice. WT control showed the increased thickness of the cross-section of CNV at the lesion and leaky CNV on day 7 and day 14, whereas these symptoms were reduced in
KIF13BKO. Because the phenotype is the neovascularization of choroidal vessels, we further confirmed it by ex vivo sprouting assay, where
KIF13BKO significantly reduced VEGF-induced sprouting from choroidal tissue (
Figs. 4E,
4F). On the basis of the previous mechanistic studies,
11,12 the simplest explanation is that the inhibition of KIF13B function by pharmacological inhibition or genetic deletion interferes with VEGFR2 trafficking, which is required for VEGF-induced angiogenesis in laser-induced CNV. Further investigation of the role of KIF13B on the early stage of the disease and the cell-types to affect will be the important future questions to define the further possibility of the efficacy of KAI on nonresponders for current therapies.