Measuring Retinal Vessel Diameter & Blood Flow Dynamics in Normal and MITF Mutant Mice

Purpose Despite data suggesting an important role in eye development, there is little data on the role of the Mitf gene in vascular development. This study aims to determine both the diameter and blood flow dynamics of retinal vasculature in normal and Mitf mutant mice. Methods In measuring the diameter, 6 Mitfmi-vga9/+ (heterozygote) and 6 Mitfmi-enu22(398)/mi-enu22(398) (homozygote) mice were compared to 6 wild type. A fundus camera was used to obtain still fundus images after intraperitoneal injection of sodium fluorescence salt. These images were processed with Photoshop and a custom written Matlab program to extract the mean vascular diameter at a specific distance from the optic disc. Each mutation was compared to the wild type. A separate comparison was done for arteries, veins and both combined. The comparison was done with respect to the number of vessels, average diameter and average total diameter (average diameter*number of vessels). The measuring of blood flow dynamics is still in progress. Therefore, only sample data from wild type, MitfMi-Wh/+ and MitfMi-Wh/mi/Mitfmi mice is provided in the results section. Results When comparing mice with the Mitfmi-enu22(398)/mi-enu22(398) mutation to the wild type we found a significant 24,8% increase in mean total arterial diameter (P=0,0243), a significant 18,8% increase in mean venular diameter (P=0,0259), a significant 38,6% increase in mean total venular diameter (P=0,004) and a significant 31% increase in mean total vessel diameter (P=0,00726). There was also a significant 18,8% increase in the number of arteries (P=0,026), a significant 15,6% increase in the number of veins (P=0,041) and a 17,2% increase in total number of vessels (P=0,026). When comparing mice with the Mitfmi-vga9/+ mutation to the wild type we found a significant 17,8% increase in mean total venular diameter (P=0,0303). Only sample data are provided as of now with respect to the blood flow dynamics. Conclusion The increase in retinal vasculature in mice with the Mitfmi-enu22(398)/mi-enu22(398) mutation compared to wild type mice suggests that there is an increased demand of blood flow to the retina in these mutations. The increase in retinal venular vasculature in the Mitfmi-vga9/+ mice without a corresponding increase in retinal arterial vasculature is a surprising finding which may be due to low number of samples. No conclusions can be drawn so far with respect to the blood flow dynamics