Structural and hemodynamic analysis of the mouse retinal microcirculation.
OBJECTIVE
In the holangiotic retina, little is known about the connections between and the circulation within microvessel layers. The goal of the present study was to explore the three-dimensional arrangement and hemodynamics of mouse retinal microvessels.


METHODS
Confocal microscopy was performed on fluorescein dextran-filled retinal flatmounts. Capillary velocity in the deep layer was measured by epifluorescence intravital microscopy. The changes in the studied parameters after branch retinal vein occlusion were evaluated.


RESULTS
The superficial and intermediate layers are both asymmetric crossroads for capillary blood flow, with approximately 70% of the capillary connections directing the flow from the arterioles into the deep layer. The venous flow from the deep layer joins the major veins in the superficial layer through transverse venules, indicating that major veins are directly connected to the deep layer. Red and white blood cell velocities +/- SD in the deep layer were 1.26 +/- 0.34 and 0.8 +/- 0.32 mm/sec respectively. After branch vein occlusion, venule dilation and decreased velocity were observed in the deep layer.


CONCLUSIONS
In the mouse retina, a tridimensional model of retinal microcirculation was established, showing that most microvessel connections on the arteriolar side direct the flow from the superficial to the deep layer, and vice versa on the venular side. However, the presence of direct arteriovenous connections in the superficial layer and the longer vessel length in the deep layer offer the possibility of actively modulating intraretinal flow. Compared with other capillary beds, both the capillary velocity and microhematocrit are high, a situation that favors nutrient delivery to the inner retina.
Laboratory for the Study of Microcirculation, Fernand Widal Hospital, Paris, France.
Michel
M
Paques
Ramin
R
Tadayoni
Richard
R
Sercombe
Pierre
P
Laurent
Olivier
O
Genevois
Alain
A
Gaudric
Eric
E
Vicaut
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D003911:Dextrans; D005452:Fluoresceins; D007202:Indicators and Reagents; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000502:physiology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D012170:Retinal Vein Occlusion / Q000503:physiopathology; D012171:Retinal Vessels / Q000033:anatomy & histology / Q000502:physiology*
D003911:Dextrans; D005452:Fluoresceins; D007202:Indicators and Reagents; C052526:fluorescein-dextran