Authors: Li Xia, Zhang Hua, Dai Xufeng, Pang Jijing
Retinitis pigmentosa (RP) is one of the causes of congenital blindness.It is well known that the degeneration process of rod cells is difficult to detect in RP.Retinal degeneration 12 (rd12) mice is a new, spontaneously arising mouse model for human Leber congenital amaurosis (LCA), and it is helpful for us to explore the pathogenesis and determine the treating target of RP.
This study was to investigate the natural disease process of short-length sensitive cone cells in rd12 mice, a LCA Rpe65rd12 (B6[A]-Rpe65rd12/J) mouse.
The rd12 mice at postnatal (P) 14, P21, P35 and P90 were selected (5 mice for each), and the wild-type C57BL/6J (B6) mice with matched ages were included as controls.Photopic full-field electroretinogram (ERG) was recorded with Roland Q450SC UV visual physiology instrument.Cone response was recorded using single white light-emitting diode (LED) stimulation with the flash intensity of 1.00 cds/m2 and 1.96 cds/m2, and short wave-length sensitive cone response was recorded using ultraviolet light ([363±6]nm) stimulation with the flash intensity of 2.0 mWs/m2 and 3.0 mW/m2.The mice were sacrificed and retinal whole-mounts were prepared.The distribution and number of cone cells and UV-sensitive cone cells were detected by FITC-peanut agglutinin (FITC-PNA) and Cy3 immunofluorescence stainning, respectively.
In P14 rd12 mice, the ERG responses of overall cone cells presented the negative waveform and the latency was delayed, and UV-sensitive cone response was unrecordable.The b-wave amplitude of overall cone cells reduced by 75% in P21 rd12 mice compared with wild-type B6 mice, and the mean latency of b-wave in the P21 rd12 mice was significantly longer than that in the wild-type B6 mice ([102.80±11.39]ms vs.[43.40±5.60]ms) (t=-8.106, P=0.001). The mean b-wave amplitudes of UV-sensitive cone cells were (59.60±36.00), (82.40±12.22) and (68.43±17.63)μV in the wild-type B6 mice, and those in the rd12 mice were unrecordable.Immunofluorescence showed that a lager number of cone cells with green fluorescence were seen, and the expression of opsin with red fluorescence was displayed in the UV-sensitive cone cells of nasal lateral on retinal ventral side in P14 wild-type B6 mice; while only a few opsin positive-response cells were seen in P14, P21 and P35 rd12 mice.
In rd12 mice, the functional abnormality and quantitative reduction of cone cells appear in the early postnatal days, and the loss of UV-sensitive cone cells is earlier and more obvious.