The Silk-protein Sericin Induces Rapid Melanization of Cultured Retinal Pigment Epithelial Cells by Activating the NF-κB Pathway
Abstract
Purpose
Restoration of the retinal pigment epithelial (RPE) cells to prevent further loss of vision in patients suffering from age-related macular degeneration represents one of the most promising novel treatment modalities in regenerative medicine. Development of RPE transplants in the laboratory, however, is a lengthy process requiring up to 3 months of cell differentiation. We explored whether the silk protein sericin can be used as a culture medium supplement to induce differentiation of human RPE.
Methods
Microarray analysis determined the expression of RPE-associated transcripts in control cultures and cultures supplemented with sericin. Quantitative immunofluorescence (QIM), spectrophotometry and transmission electron microscopy (TEM) validated the findings.
Results
Sericin supplementation increased the expression of RPE-associated transcripts (RPE65 and CRALBP). The NF-kB pathway was identified as one of the top sericin-induced regulators. Increased levels of RPE-associated proteins (including CRALB and the pigment melanin) in the sericin-supplemented cultures were confirmed by QIM, spectrophotometry and TEM. Sericin supplementation also increased cell survival following serum starvation. Inclusion of NF-kB agonists and antagonists in the culture medium showed that activation of the NF-kB pathway appears to be necessary, but not sufficient, for sericin-induced RPE pigmentation.
Conclusions
Sericin promotes pigmentation of cultured human RPE by activating the NF-kB pathway.
