Figure 7.

Effect of MMF on cGMP IHC in rd10 and rd1 mice. (A) Nuclear stain with DAPI (blue) and immunostaining of cGMP 1:500 (red) show that rd10 mice treated with MMF starting at P12 (MMFP12) and c57 mice had no cGMP staining of the ONL as compared with naïve rd10 mice, which had scattered staining of the ONL cell bodies and residual photoreceptor outer segments. Compared with naïve rd1 mice, treatment with MMF starting at P8 (MMFP8) inhibited cGMP immunostaining when normalized to the ONL area. (B) cGMP IHC quantified as positive cell counts per ONL area showed that naïve rd10 mice exhibited an abrupt onset of cGMP staining beginning at P16 and spiked even higher at P22-24. Naïve rd1 mice had an even more dramatic rise in cGMP immunostaining from P8 to P11/12 with an inflection at P13 and an even greater peak at P15. Wild type c57 mice had no appreciable cGMP positive cell counts at all time points analyzed: P15, P22, and P35. Compared with naïve rd10 mice, treatment with MMFP12 significantly suppressed cGMP staining at P16 (n = 4 and 4, P = 0.0019), P17 (n = 4 and 4; P = 0.0003), P19 (n = 3 and 4; P = 0.0071), and P22 (n = 11 and 9; P < 0.0001). At P27, MMFP12-treated rd10 mice still had significantly lower cGMP staining than naïve rd10 mice (n = 6 and 4; P = 0.0013), but at P35 it was not significantly different (n = 3 and 3; P = 0.40). Compared with naive rd1 mice, MMFP8 treatment significantly suppressed cGMP immunoreactivity at P15 (n = 8 and 7; P < 0.0001). (C) The inhibitory effect of MMF on cGMP staining in rd10 mice at P22 was significantly diminished when treatment initiation was delayed from P12 to P14 (MMFP14, n = 6; P = 0.05). INL, inner nuclear layer; ns, nonsignificant; ^*P ≤ 0.05.