Quantifying Longitudinal Network Geometry Alterations in Rat Skeletal Microvasculature Subject to Ischemia

Abstract

Study objectiveIntra‐vital video microscopy (IVVM) data of rat subcutaneous skeletal muscle microvasculature under ischemic conditions at two time points (0 hours, 3 hours) was obtained from our collaborator. The objectives of this study are to elicit network geometries from the IVVM data and quantify the alterations in the network statistics of the geometries due to ischemia.HypothesisWe hypothesize that ischemia causes blood vessel de‐recruitment.MethodsIVVM data from six experiments was obtained, where each experiment provided a video at the start (0 hours) and end (3 hours) of the experiment. Using consecutive still images from the videos, vessel centerlines were manually drawn using Procreate and the NIH software, ImageJ. The included vessels were chosen based on two features: (1) visible red blood cell flow and (2) clearly defined edges. The centerlines were used to guide thresholding by identifying appropriate vessels. This was followed by the generation of binarized representations of the microvascular networks. The network statistics were quantified by measuring vessel segment lengths and diameters, counting the number of bifurcations, and calculating vessel density in ImageJ.ResultsAt 3 hours, the average vessel length changed from 283.91 + 252.14 pixels to 316.75 + 292.37 pixels, the average diameter changed from 16.02 + 7.99 pixels to 15.42 + 7.50 pixels, the average number of bifurcations changed from 32.42 to 18.92 and the average vessel density changed from 0.0085 + 0.0017 to 0.0061 + 0.0024.ConclusionThere is a clear decrease in average diameter, vessel density and the number of bifurcations characterizing the microvascular networks. However, an increase in the average vessel length accompanies these findings. The data indicates that ischemia may cause de‐recruitment of blood vessels.