Detrimental Effects of UVB on Retinal Pigment Epithelial Cells and Its Role in Age-Related Macular Degeneration

Table 1

Characteristics and drawbacks of various established and primary RPE cell lines.

Model	Species	Type of cell line	Source	General characteristics and drawbacks	References
ARPE-19	Human	Established	Globes of a 19-year-old male donor who had passed away 2 h before extraction	General characteristics: (i) “Cobblestone appearance” and forms a monolayer; (ii) Increasing pigmentation in cells with passages; (iii) Formation of domes, indicating ability to pump ions vectorially; (iv) Expresses cellular retinaldehyde-binding protein (CRALBP) and RPE-specific protein (RPE65), which are components in the retinoid visual cycle; (v) Diploid karyology; Drawbacks: (i) Low transepithelial resistance (TER) measurement which could compromise barrier functions; (ii) Unable to obtain complete polarization; (iii) Heterogenous expression of CRALBP; (iv) Varied in pigmentation across different cells; (v) Inconsistent formation of microvilli; (vi) Deletion in chromosome 8 and addition in chromosome 19; (vii) Features such as morphology, retinoid metabolism, secretion of vascular endothelial growth factor (VEGF), and pigment epithelium-derived factor (PDEF) become compromised with increasing passages	[24, 40, 41]
D407	Human	Established	Globes of a 12-year-old white male	General characteristics: (i) “Cobblestone appearance” and forms a monolayer; (ii) Has intercellular junctional complexes linking tightly apposed membranes by N-cadherin; (iii) Has cortical microfilaments parallel to the plasma membrane and actin filaments bound to the lateral surface of the cells; (iv) Short microvilli on apical surfaces of the cells; (v) Contained keratins 7, 8, 18, and 19 and formed the keratin filament network throughout the cytoplasm in confluent cells; (vi) Expresses CRALBP, indicating the transport of retinoids; (vii) Expresses vimentin, which is commonly expressed in many epithelial cells; (viii) Able to subculture for more than 200 times; Drawbacks: (i) Lack of pigmentation; (ii) Form triploid karyotype when cells are more than 50 passages; (iii) Low TER measurement; (iv) Did not localize tight junction protein zonula occludens-1 (ZO-1) to cell borders, indicating impairment in barrier function; (v) Loss of polarization in spectrin associated with the actin and transmembrane proteins; (vi) Only one out of the three enzymatic reactions in the metabolism of vitamin A, retinol dehydrogenase (RDH) activity was observed	[25, 42]
DrRPE	Zebrafish	Primary cell line	Eyes of 15 3-month-old adult zebrafish	General characteristics: (i) Cell diameter is 15-19 μm; (ii) Optimum growth condition is at 28°C with 15% FBS; (iii) Doubling time is around 40 h; (iv) Forms monolayer of majority mononucleate; (v) Cells form pigment granules in 10 days; (vi) Expresses RPE65 and cytokeratin 19; (vii) Cells were able to be subculture more than 75 times and were able to recover from a year of liquid nitrogen storage even at passage 75; (viii) High plating efficiency; (ix) Diploid chromosomes, ranging from 38-53 chromosomes, with 50 chromosomes being the most common number; (x) Able to convert all-trans-retinol to retinyl esters, producing retinosomes; Drawbacks: (i) Some binucleate cells were found in culture; (ii) Loss of melanin granules with increasing passages	[33]
Bovine RPE cells	Bovine	Primary cell line	Globes of freshly slaughtered bovine	General characteristics: (i) Polygonal or cuboidal shaped lightly pigmented cells with round nuclei; (ii) Expresses vimentin, S100, and cytokeratin proteins; (iii) Has a slower growth rate as compared to the iris pigment epithelium, iris melanocyte, and choroidal melanocyte	[43]