Abstract: Objective To investigate the expression of C-C chemokine receptor 1（CCR1）, a major chemokine receptor for β-chemokines, in the ratina of  rd (retinal degeneration) mice and further explore its role in the photoreceptor degeneration. Design Experimental study. Partrcipants Sixty rd mice at postnatal days (P) 8, 10, 12, 14, 16 and 18 day (10 mice each) and 60 C57BL/6N control mice with the matcholde age (10 mice each). Methods The expression levels of CCR1mRNA in the whole control  rd mice were determined by RT-PCR assay. Location of CCR1 in the retina were studied by immunohistochemical analysis. Expression of CCR1 in the photoreceptor cells and apoptotic cells was determined by double labeling. Main Outcome Measures Expression of CCR1mRNA and CCR1 protein, cellular location of CCR1 and its relation to the apoptotic cells.  Results Expression of CCR1mRNA was noted in both control and rd mice retinas at each age group, but was markedly increased in the rd mice retinas at P12 and P14 day. CCR1-positive cells started to emerge in the rd mice retina at P8 day and reached a peak at P12 and P14 day. Double labeling of CCR1 with rhodopsin, CD11b or TUNEL staining showed expression of CCR1 in the photoreceptor cells, rather in the microglial cells. Partial CCR1 expression was observed in some of the apoptotic photoreceptor cells. Conclusion Expression of CCR1 in the photoreceptor cells was increased with progression of retinal degeneration in rd mice. Activation of CCR1 may play a role in the photoreceptor apoptosis.

Key words: β-chemokine receptor, microglia, photoreceptor apoptosis, rd mice