Abstract
Purpose:
Zebrafish are a popular model for studies of development and disease. Since they are an aquatic species, lens-relevant physiology may be different to terrestrial animal models. In this study we have compared the composition and concentration of the lipid species in the lens of zebrafish and mice at 2 and 12 months.
Methods:
Zebrafish and mice were fed standard laboratory diets. After euthanization, eyes were removed and lenses isolated and homogenized. Lipids were recovered under argon by Bligh-Dyer extraction and infused into an AB Sciex 5600 TripleTOF mass spectrometer to collect MSMS data at successive unit masses on ions from 200-1200 mass-to-charge ratio (m/z). LipidView™ software was used to deconvolute the data.
Results:
The principal phospholipids (PL) in the mouse and zebrafish lens in the positive mode were phosphatidylcholines (PC) and sphingomyelins (SM) with only minor amounts (<1.0%) of NAPEs, ceramides, phosphatidylethanolamines and phosphatidylglycerols. Zebrafish lens contains a higher proportion of SMs (56%) than mouse lens (46%). Equivalent and very low amounts of PEs and Ceramides were observed in both mouse and ZF lens. Interestingly, very small amounts of phosphatidylglycerol were observed in mouse lens and O-linked PCs were undetectable in zebrafish lens. Although the relative proportions of SMs, PCs and other major lipid classes in lens of mouse and zebrafish did not change with age, short chain PCs increased whereas long chain PCs decreased with age in both species (with long chain LPCs increasing reciprocally with long chain PC reductions). There were more individual lipid species that changed with aging in the zebrafish than in mice. Imaging mass spectrometry not only confirmed our previous observation that most phospholipids were confined to the outer cell layers of the lens, but also that they had discrete distribution throughout the eye.
Conclusions:
Zebrafish lens has a PL profile that closely matches that of mouse lens and is comparable to human lens. In addition, aging led to decreases in the length of the fatty acyl groups in PLs in both species. Mass spectrometry imaging demonstrated that intact phospholipids are limited to the outer cortex and undifferentiated cells of the lens of both species as well as prominently in the retina. These data suggest that zebrafish represent an excellent model of lipid biochemistry of the lens and ocular system.