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Jeanette Christophel, Lars-Olof Hattenbach, Josef Pfeilschifter, Waltraud Pfeilschifter; Sphingosine kinase 2 induces angiogenic effects by enhancing neovascularisation in the mouse model of retinopathy of prematurity. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3187.
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© ARVO (1962-2015); The Authors (2016-present)
The roles of Sphingosine kinase 2 (Sphk2), a key regulator of the cell fate dictating Sphingolipid balance, are complex and not well characterized but its dysfunctions has been shown to facilitate the development of various diseases. To decipher the - so far unknown - functions of Sphk2 in retinal vascular diseases, Sphk2 overexpressing mice were used in an experimental model of oxygen-induced retinopathy (OIR).
Neonatal C57BL/6J (WT) and EllaCrexJos5a (humane Sphk2 expressing mice with C57BL/6J background, leading to a general overexpression of Sphk2) were used in the OIR model. Neonates were subjected to 75% O2 for 5 days (postnatal day (P) 7 to 12) and then returned to room air. Lipid analysis by LC-MS/MS (n=4), immunhistochemistry on wholemount (n=12), and paraffin embedded retina slides (n=3) were performed on P12, P14 and P17 old retinae. Avascular areas and neovascularisation (NV) were analysed with Adobe Photoshop and ImageJ. One-way ANOVA was used for statistical analysis.
Sphk2 overexpression (Sphk2↑) is reducing retinal layer thickness at P12 (outer nuclear layer (ONL): WT 72.33µm±3.26, Sphk2↑ 43.33±1.98, p<0.001), as well as OIR treatment (ONL: WT Normoxie 72.33µm±3.26, WT OIR 53.29±2.85, p<0.001). Furthermore, more deep thick blood vessels are found in Sphk2↑ mice (2.86 fold, p<0.001). In the OIR model, the avascular area at P12 was significantly (p<0.0001) decreased in Sphk2↑ mice (28.34%±4.78; WT 43.30%±3.32). In Sphk2↑ NV is increased from P14 (1.48%, p<0.01) but blood vessels show a more chaotic organization at P17. In this state, Sphk2↑ induces more GFAP-positive Müller cell processes, interestingly glutamine synthetase stainings do not indicate morphologic changes. The proproliferative Sphk2 metabolite Sphingosine-1-phosphate is increased (p<0.001) in Sphk2↑, particular at P17 (43.90pg/mg±5.30) compared to WT (29.18pg/mg±4.24), but is not influenced by OIR treatment.
Our results show that Sphk2 plays a role in the development of the retina and its vascular structure under normal and pathophysiologic conditions, as shown by the reduced vessel loss in the initial stage followed by increased NV with more pathologic vessel formation. Further studies are needed to unravel the cellular and molecular mechanisms to deepen the knowledge regarding Sphk2, especially during pathological angiogenesis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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