To investigate the effects and mechanism of exosome (EXO)-loaded kringle V11 (KV11) delivery on corneal neovascularization (CNV).

KV11 was bound to the surface of endothelial cell-derived exosomes by using CP05, an EXO-targeting anchoring peptide, to produce EXO-KV11.The binding efficiency and optimal concentration ratio were determined using the Apogee flow system.A total of 100 8-week-old healthy male SPF grade SD rats were selected, 10 of which were randomly selected as a normal control group without any treatment.The CNV model was established by alkali burn in the other 90 rats, which were randomly divided into three groups, EXO-KV11 group, KV11 group, and normal saline group by the random number table method, with 30 rats in each group.Each group was injected subconjunctivally with 100 μl of EXO-KV11 (25 μg), KV11 (25 μg), or normal saline every other day from the first day after the alkali burn, respectively.The CNV of rats was observed on days 1, 4, 7, and 14 after alkali burn.The CNV area was calculated by ventricular perfusion with fluorescein isothiocyanate-dextran (FITC-dextran) and corneal angiography.The amount of CNV lumen was observed by hematoxylin and eosin staining.The distribution of CD31 in rat corneas was determined by immunohistochemical method.The expression levels of voltage-dependent anion channel 1(VDAC1), endoplasmic reticulum stress, autophagy and apoptosis-associated proteins were detected by Western blot.This study was approved by the Animal Ethics Committee of Peking University People's Hospital (No.20210019). All animal procedures complied with the regulations of the Vision and Ophthalmology Association and the Animal Protection and Use Committee of Peking University.

The optimal concentration ratio of KV11 to EXO was 4∶1 and the binding affinity reached up to 87.5% by Apogee flow cytometers.On days 7 and 14 after alkali burn, there were significant differences in CNV area among the four groups (F=4.613, 15.590; both at P<0.05). On day 7 after alkali burn, the CNV area was smaller in EXO-KV11 group than in KV11 and normal saline groups, with statistically significant differences (both at P<0.05). On day 14 after alkali burn, the CNV area was smaller in EXO-KV11 and KV11 groups than in normal saline group, and smaller in EXO-KV11 group than in KV11 group, showing statistically significant differences (all at P<0.05). The results of quantitative analysis of corneal fluorescence mounts showed that the relative CNV fluorescence area of the normal saline group, KV11 group and EXO-KV11 group were (8.3±1.7)%, (5.2±1.6)%and (3.4±0.7)%, respectively, showing a statistically significant overall comparison difference (F=11.735, P<0.01). The relative CNV fluorescence area was larger in KV11 and normal saline groups than in EXO-KV11 group, and larger in normal saline group than in KV11 group, showing statistically significant differences (all at P<0.05). On day 14 after alkali burn, massive neovascular lumens were observed in the matrix of the normal saline group.The number of neovascular lumens in KV11 group was smaller than that in normal saline group.The corneal structure appeared normal in EXO-KV11 group, and neovascular lumens were rare.Numerous CD31-positive cells were observed in the corneal stroma of the normal saline group, which formed into lumen structures.The number of lumens surrounded by CD31-positive cells in the corneal stroma was smaller in KV11 group than in normal saline group, and smaller in EXO-KV11 group than in KV11 group.There were significant differences in the relative expression levels of VDAC1, protein kinase R-like endoplasmic reticulum kinase (PERK), p62, cleaved caspase 3 among the four groups (F=35.960, 8.947, 17.791, 101.168; all at P<0.01). The relative expression levels of VDAC1, PERK, p62, cleaved caspase 3 were higher in EXO-KV11 group than in KV11 and normal saline groups, showing statistically significant differences (all at P<0.001). There was no significant difference in the relative expression of microtubule-associated proteins 1A/1B light chain 3B (LC3B)Ⅱ/LC3BⅠ protein among all four groups (F=0.445, P=0.727).

EXO-KV11 can inhibit CNV more remarkably than KV11.EXO-KV11 inhibits CNV by promoting the expression of VDAC1 and PERK and suppressing the autophagic flux.

Corneal neovascularization; Autophagy; Exosomes; Plasminogen kringle 5; Voltage-dependent anion channel 1