Smith-Thomas L, Richardson P, Thody A J, Graham A, Palmer I, Flemming L, Parsons M A, Rennie I G, MacNeil S
University Department of Medicine, Northern General Hospital, Sheffield, UK.
Curr Eye Res. 1996 Nov;15(11):1079-91. doi: 10.3109/02713689608995139.
The vertebrate eye contains both melanocytes and retinal pigment epithelial (RPE) cells. Little is known of the pigmentary behaviour of these embryologically dissimilar cells. The aim of this study was to examine aspects of the pigmentary properties of both cell types in vitro and ex vivo to learn more of the function of these cells.
Sections of normal adult human eye were stained for tyrosinase related protein 1(TRP1), and cultures of RPE cells and choroidal melanocytes were examined immunocytochemically for TRP1 and 2 and enzymatically for tyrosinase activity (by assaying dopa oxidase activity).
Over half of the choroidal melanocytes expressed TRP1 ex vivo; in contrast, a very small percentage of RPE cells were TRP1 positive. In vitro, passage 1 to 3 ocular melanocytes expressed TRP1 and TRP2 and had tyrosinase activity, which was influenced by the choice of substrate on which the cells were grown. Tyrosinase activity was highest when cells were grown on fibronectin and plastic, intermediate on laminin and lowest on vitreous extracellular matrix (ECM) containing pigment to which they attached and spread out poorly. In contrast, passage 3 RPE cells (which were unpigmented) showed little evidence of tyrosinase activity in short-term culture, irrespective of the substrate on which they were grown, and failed to express TRP1 and TRP2. When cells were grown on plastic for greater than 3 weeks in culture, a very low percentage of cells (< 0.1%) became TRP1 positive and this percentage was increased threefold if cells were cultured on laminin in the presence of bFGF. A few cells were also seen to contain pigment but cultures failed to show any tyrosinase activity. In contrast, RPE cells (but not melanocytes) showed a marked ability to take up pigment granules in vitro.
The data suggest that normal human ocular melanocytes retain the capacity to produce pigment throughout adult life, and this can be demonstrated both ex vivo and in vitro. In contrast, we were unable to confirm that the majority of RPE cells play any significant role in active pigment production in the adult.
脊椎动物的眼睛包含黑素细胞和视网膜色素上皮（RPE）细胞。对于这些在胚胎学上不同的细胞的色素沉着行为知之甚少。本研究的目的是在体外和离体条件下研究这两种细胞类型的色素特性，以更多地了解这些细胞的功能。
对正常成人眼的切片进行酪氨酸酶相关蛋白1（TRP1）染色，并对RPE细胞和脉络膜黑素细胞培养物进行TRP1和TRP2的免疫细胞化学检测以及酪氨酸酶活性的酶学检测（通过测定多巴氧化酶活性）。
超过一半的脉络膜黑素细胞在离体条件下表达TRP1；相比之下，只有极少数百分比的RPE细胞为TRP1阳性。在体外，第1至3代眼黑素细胞表达TRP1和TRP2并具有酪氨酸酶活性，这受到细胞生长底物选择的影响。当细胞在纤连蛋白和塑料上生长时，酪氨酸酶活性最高，在层粘连蛋白上中等，而在含有色素且细胞附着和铺展较差的玻璃体胞外基质（ECM）上最低。相比之下，第3代RPE细胞（未色素沉着）在短期培养中几乎没有酪氨酸酶活性的迹象，无论它们生长在何种底物上，并且不表达TRP1和TRP2。当细胞在培养物中在塑料上生长超过3周时，极低百分比的细胞（<0.1%）变为TRP1阳性，如果细胞在存在碱性成纤维细胞生长因子（bFGF）的层粘连蛋白上培养，该百分比会增加三倍。还观察到少数细胞含有色素，但培养物未显示任何酪氨酸酶活性。相比之下，RPE细胞（而非黑素细胞）在体外显示出明显的摄取色素颗粒的能力。
数据表明，正常人类眼黑素细胞在成年期仍保留产生色素的能力，这在离体和体外均可得到证实。相比之下，我们无法证实大多数RPE细胞在成年人的活性色素产生中发挥任何重要作用。
