Relationship between regression of the hyaloid vessels and development of retinal vessels in mice

Objective

To explore the process of regression of the hyaloid vessels and development of retinal vessels in C57BL/6J mice and the relationship between them.

Methods

Seventy-five healthy SPF C57BL/6J mice on postnatal day 1 (P1) were selected and divided into control group (65 mice) and oxygen-induced retinopathy (OIR) model group (10 mice) by the random number table method.No treatment was given to control group.Mice in OIR model group were continuously fed in (75±3)% oxygen for 5 days from P7 and in normoxic condition for 5 days from P12.In control group, 5 mice were randomly selected and killed from P1 to P12 and P17, and the eyeballs were collected.In OIR model group, 5 mice were randomly selected and killed on P12 and P17, and the eyeballs were collected.The number of hyaloid arteries (HA), vasa hyaloidea propria (VHP), and tunica vasculosa lentis (TVL) of mice at different time was observed with a microscope.Another 5 adult mice aged 15 months old were selected to detect the vitreous vasculature using optical coherence tomography.The relationship between retinal astrocytes and retinal vascular development, VHP was observed by immunofluorescence staining.This study was approved by the Ethics Committee of Nankai Hospital (No.NKYY-DWLL-2021-070). The use and care of experimental animals followed the Regulations for the Administration of Affairs Concerning Experimental Animals and the ARVO statement.

Results

In control group, HA did not degenerate rapidly during eyeball development, which still presented even 15 months after birth.The number of VHP reduced rapidly from P4 to P8, and tended to be stable at 2.33±1.32 on P10 and 1.80±0.92 on P17.The number of TVL reduced rapidly from P5 to P9, reduced to 2.30±1.42 on P10, with most of the TVL blood vessels being transparent without blood supply, and decreased to 0.30±0.48 on P17.Under the guidance of astrocytes, the retinal vessels of mice grew from the optic disc to the peripheral retina from P1 to P8, forming the primary retinal vascular layer.During the development of retinal superficial vessels, VHP showed synchronous regression and the decreased density and thinner diameter in the area covered by retinal vessels.VHP detached from the retina when retinal vessels developed to the peripheral retina, and there was no structural overlap between astrocytes and VHP.In OIR model group, the number of VHP increased from 2.14±0.90 on P12 to 4.60±1.35 on P17 and the number of TVL increased from 2.90±1.55 on P12 to 5.80±1.75 on P17, showing statistically significant differences (t=4.188, P<0.001; t=4.668, P<0.001). There was no significant difference in the number of VHP and TVL between the two groups on P12 (t=0.429, P=0.232; t=1.116, P=0.134). The number of VHP and TVL were significantly larger in OIR model group than in control group on P17 (t=5.422, 9.574; both at P<0.001).

Conclusions

In the vitreous vascular system of mice, the regression of VHP and TVL tends to be stable 10 days after birth, and the regression of HA was not obvious.The normal regression of vitreous vessels in mice depends on the normal development of retinal vessels and astrocytes.Retinal hypoxia delays vitreous vascular regression.

Vitreous Body; Retinal vessels; Astrocytes; Mice