In the eye, the choroid (between the retina and sclera) plays an important role in supplying nutrients and oxygen and removing metabolites from the retinal pigment epithelium and retina. The choroid stroma contains melanin-containing melanocytes within an extracellular matrix that includes blood vessels, immune cells, nerves, and fibroblasts. As the most numerous cells within the choroid, melanocytes contribute significantly to the normal intraocular environment, with both ‘melanin’ and ‘non-melanin’ functions including light absorption, antioxidant, free-radical scavenging activities and may modulate local inflammation and angiogenesis.
The current understanding of eye melanocyte biology and function is mostly from skin melanocyte studies, but they have major biological differences as well as different tissue microenvironment and relative exposure to light (Including UV). In response to UV exposure, skin melanocytes produce melanin with a melanocortin ligand-receptor system. Conversely, inside the human eye only receives <1% UV light. Skin melanocytes are also vulnerable to oxidative stress, induced by light exposure or inflammation, which can disrupt cell function, reduce cell survival and may induce genetic changes associated with malignant transformation. Endogenous melanocortin peptide, α-MSH, can reduce the impact of UV-induced oxidative stress for skin melanocytes. This system also downregulates inflammation and induces protective immune responses in several tissues in the body and may repair and stabilise damaged DNA and prevent cell death.
Recent studies highlight an emerging immunomodulatory role for choroid melanocytes, including expression of immune-related Toll-like receptors, normal and enhanced secretion of proinflammatory chemokines after inflammatory stimulation, and capacity to attract monocytes when stimulated. Interestingly, the dogma remains that melanocortin-induced melanin synthesis is absent in the eye (even for iris melanocytes exposed to significant levels of UV). Furthermore, there is no recognised expression of melanocortin-1 receptor (MC1R) or functional alpha-MSH-MC1R interaction in human eye melanocytes. However, our preliminary data suggests that MC1R is expressed in the human choroidal melanocytes. There is also no clear evidence for melanocortin to reduce oxidative stress and inflammation in eye melanocytes.
Based on current literature, my thesis aims to improve our understanding of the biological signalling pathways involved in human eye melanocyte responses to light exposure (UV versus visible light), oxidative stress and inflammation-related molecules, and the role of the melanocortin system in regulating these responses.
Stanley is a PhD candidate at the School of Optometry and Vision Science, UNSW. He received a Master of Science in Molecular and Cellular Biology from National Taiwan University (2008) and Master of Optometry (Coursework) from UNSW (2017). He is a lecturer at the Department of Optometry, Asia University, Taiwan. He is also the representative Optometrist at Taiwan Optometry Clinical Centre. With a passion for both Cell Biology and Optometry, he commenced his PhD study which aims to further understand the role choroidal melanocytes play in responding to oxidative stress and inflammation in choroidal microenvironment.
Master of Optometry, The University of New South Wales, Sydney, Australia (2017)
Postgraduate Bachelor of Optometry, Chung Shan Medical University, Taichung, Taiwan (2015)
Master of Science in Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan (2008)
Bachelor of Science in Life Science, National Dong Hwa University, Hualien, Taiwan (2006)
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