Noninvasive in vivo assessment of the skeletal muscle and small intestine serous surface microcirculation in rat: sidestream dark-field (SDF) imaging

The pathophysiology of microcirculation is intensivelyinvestigated to understand disease development at themicroscopic level. Orthogonal polarization spectral (OPS) imagingand its successor sidestream dark-field (SDF) imaging arerelatively new noninvasive optical techniques allowing directvisualization of microcirculation in both clinical and experimentalstudies. The goal of this experimental study was to describe basicmicrocirculatory parameters of skeletal muscle and ileal seroussurface microcirculation in the rat using SDF imaging and tostandardize the technical aspects of the protocol. Interindividualvariability in functional capillary density (FCD) and small vessels(<25 μm in diameter) proportion was determined in anesthetizedrats on the surface of quadriceps femoris (m. rectus femoris andm. vastus medialis) and serous surface of ileum. Special custommade flexible arm was used to fix the SDF probe minimizing thepressure movement artifacts. Clear high contrast images wereanalyzed off-line. The mean FCD obtained from the surface ofskeletal muscle and ileal serous surface was 219 (213-225cm/cm2) and 290 (282-298 cm/cm2) respectively. There was nostatistically significant difference between rats in mean values ofFCD obtained from the muscle (P = 0.273) in contrast to ilealserous surface, where such difference was statistically significant(P = 0.036). No statistically significant differences in smallvessels percentage was detected on either the muscle surface(P = 0.739) or on ileal serous surface (P = 0.659). Our study hasshown that interindividual variability of basic microcirculatoryparameters in rat skeletal muscle and ileum is acceptable whenusing SDF imaging technique according to a highly standardizedprotocol and with appropriate fixation device. SDF imagingrepresents promising technology for experimental and clinicalstudies.