Normal retina releases a diffusible factor stimulating cone survival in the retinal degeneration mouse

The role of cellular interactions in the mechanism of secondary cone photoreceptor degeneration in inherited retinal degenerations in which the mutation specifically affects rod photoreceptors was studied. We developed an organ culture model of whole retinas from 5-week-old mice carrying the retinal degeneration mutation, which at this age contain few remaining rods and numerous surviving cones cocultured with primary cultures of mixed cells from postnatal day 8 normal-sighted mice (C57BL/6) retinas or retinal explants from normal (C57BL/6) or dystrophic (C3H/He) 5-week-old mice. After 7 days, the numbers of residual cone photoreceptors were quantified after specific peanut lectin or anti-arrestin antibody labeling by using an unbiased stereological approach. Examination of organ cultured retinas revealed significantly greater numbers of surviving cones (15–20%) if cultured in the presence of retinas containing normal rods as compared with controls or cocultures with rod-deprived retinas. These data indicate the existence of a diffusible trophic factor released from retinas containing rod cells and acting on retinas in which only cones are present. Because cones are responsible for high acuity and color vision, such data could have important implications not only for eventual therapeutic approaches to human retinal degenerations but also to define interactions between retinal photoreceptor types.

本研究针对突变仅特异性累及视杆细胞（rod photoreceptor）的遗传性视网膜变性（inherited retinal degenerations）疾病，深入探讨了细胞相互作用在继发性视锥细胞（cone photoreceptor）变性机制中的作用。我们构建了携带视网膜变性突变的5周龄小鼠全视网膜器官培养模型（organ culture model）——该年龄段小鼠视网膜内仅存少量存活视杆细胞，同时尚存大量视锥细胞；随后将该模型与出生后第8天正常视力C57BL/6小鼠视网膜混合细胞原代培养物，或正常（C57BL/6）、营养不良型（C3H/He）5周龄小鼠的视网膜外植体（retinal explants）进行共培养。培养7天后，通过花生凝集素（peanut lectin）或抗抑制蛋白抗体（anti-arrestin antibody）进行特异性标记，采用无偏体视学方法（unbiased stereological approach）对残余视锥细胞数量进行定量分析。实验结果显示，相较于对照组或视杆细胞缺失的共培养体系，在含有正常视杆细胞的视网膜共培养环境中，存活视锥细胞数量显著提升15%~20%。上述数据表明，含有视杆细胞的视网膜可释放一种可扩散性神经营养因子，作用于仅存视锥细胞的视网膜组织。鉴于视锥细胞负责介导高视觉敏锐度与色觉，本研究结果不仅可为人类遗传性视网膜变性的治疗策略提供重要参考价值，也有助于阐明视网膜感光细胞类型间的相互作用机制。