Objective   To observe the relationship of activation of retinal cells in the proliferating marginal region of Royal College of Surgeon’s rats (RCS rats

an animal model for inherited retinal degeneration)

and the expressional changes of sonic hedgehog-patched (Shh/Ptc) signaling during development of retinitis pigmentosa.    Methods   Totally 28 RCS rats were divided into 4 groups randomly

that is

postnatal day (PND) 15

30

60 and 90 group according to the severity of degeneration (in each group

4 rats for immunofluorescence staining and the left 3 for PCR analysis). Age-matched Long-Evan’s rats without retinal degeneration served as controls. The thickness of outer nuclear layer (ONL) was detected by using DAPI immunofluorescence staining. Ki67

a proliferating marker was detected using immunofluorescence staining

and positive cells were counted per counting-field in the proliferating marginal region of the retinal. mRNA expressions of Shh

Ptc1

Smo and Gli1 in Shh/Ptc signaling pathway were detected by fluorescent quantitation PCR.    Results   Compared with age-matched Long-Evan’s rats

the thickness of ONL of RCS rats had been decreased with aging since PND 15

and almost disappeared at PND 90 RCS rats. There were more Ki67 positive cells at PND 30 and PND 60 RCS rats than in age-matched Long-Evan’s rats (P0.05); compared with PND 15

PND 30 and PND 90 RCS rats

the positive cells at PND 60 RCS rats were increased markedly (P0.01). mRNA levels of Shh

Ptc1

Smo and Gli1 in Shh/Ptc signaling pathway were upregulated at PND 60 RCS rats compared with PND 15

PND 30

PND 90 RCS rats and age-matched Long-Evan’s rats.    Conclusion   Retinal cells are activated to proliferate at the proliferating marginal region within a short time in the retinal of RCS rats at PND 60

which might be regulated by Shh/Ptc pathway.