Abstract
Purpose:
To investigate and compare the chemical compositions of human RPE lipofuscin and melanolipofuscin. Understanding their chemical compositions will provide insight into the mechanisms or pathways that generate these granules. As such, these mechanisms or pathways could be targeted to prevent or retard pigment granule accumulation in the RPE.
Methods:
Human RPE lipofusicn and melanolipofuscin is extracted from human donor eyes as previously described by Feeney-Burns. Folch extraction is performed to obtain the organic soluble portion of each pigment granule. The organic soluble lipofuscin and melanolipofuscin is collected, dried under Argon, and reconstituted in HPLC grade methanol for use in high performance liquid chromatography tandem mass spectrometry (LC/MS/MS) coupled a fluorescent detector (Surveyor LC with PDA, Thermo Finigan LCQ Advantage MS, Surveyor FL). Tandem mass spectrometry data is analyzed for the investigation of differences in chemical compositions of human RPE lipofuscin and melanolipofuscin.
Results:
Lipofuscin and melanolipofuscin extracts from human donor tissue have been subjected to LC/MS/MS. Base peak chromatograms observed from LC/MS/MS analysis suggest that both similarities and differences exist between the chemical compositions of human RPE lipofuscin and melanolipofuscin. This supports the working models for their formation but also suggests that their respective formations are more complex than originally perceived.
Conclusions:
Human RPE melanolipofuscin is thought to form as accreting human RPE lipofuscin fuses with human RPE melanosomes. The similarities in chemical compositions observed further support this working model. However, the differences observed also suggest additional pathways or mechanisms. As such, melanolipofusicn formation may be more complex than originally perceived.