Abstract
Purpose::
The incidence of conjunctival melanoma increased in past decades and also increased with decreasing latitude in the US (Photochem Photobiol, 2006, in press), indicating that conjunctival melanoma is more similar to cutaneous melanoma than to uveal melanoma with respect to solar radiation. Epidermal melanocytes respond to α-melanocyte stimulating hormone (α -MSH) with increased proliferation and melanogenesis, but uveal melanocytes do not (Invest Ophthalmol Vis Sci 47:4507, 2006). The effect of α -MSH on CM is unknown. This study compared the effect of α -MSH on CM to that of epidermal and uveal melanocytes.
Methods::
Human CM were isolated from donor eyes and cultured with HU16 culture medium (F12 medium supplemented with bFGF, IBMX, cholera toxin and serum) as reported previously [Pigment Cell Res. 2005, 18(supl. 1):39]. Early passages of CM were seeded to 12-well plates and cultured with cAMP-deleted HU16 medium with various concentrations of α-MSH. After 6 days, cell number and melanin content were measured. Cells cultured in HU16 medium with or without cAMP-elevating agents were used as positive and negative controls. The effects of α-MSH on cultured human uveal and epidermal melanocytes were tested for comparison.
Results::
CM cultured with cAMP-deleted medium grew slowly and showed less pigmentation. α-MSH at concentrations from 0.01-10 µM had a dose-dependent stimulative effect on cell growth and melanogenesis. Cell number and melanin content of CM cultured with α-MSH at 1 µM were 164% and 182% of the negative controls, respectively. The difference between cells cultured with and without α-MSH was statistically significant (P < 0.01). α-MSH also showed stimulative effects on cell growth and melanogenesis of epidermal melanocytes but not on that of uveal melanocytes.
Conclusions::
CM and epidermal melanocytes respond to α-MSH with increased growth and melanogenesis, whereas uveal melanocytes do not.
Keywords: melanocytes • conjunctiva