In vivo phenotyping of the microvasculature in necrotizing enterocolitis with multicontrast optical imaging

Objective: Necrotizing enterocolitis (NEC) is the most prevalent gastrointestinal emergency in premature infants and is characterized by a dysfunctional gut microcirculation. Therefore, there is a dire need for in vivo methods to characterize NEC-induced changes in the structure and function of the gut microcirculation, that is, its vascular phenotype. Since in vivo gut imaging methods are often slow and employ a single-contrast mechanism, we developed a rapid multicontrast imaging technique and a novel analyses pipeline for phenotyping the gut microcirculation. Methods: Using an experimental NEC model, we acquired in vivo images of the gut microvasculature and blood flow over a 5000 × 7000 μm² field of view at 5 μm resolution via the following two endogenous contrast mechanisms: intrinsic optical signals and laser speckles. Next, we transformed intestinal images into rectilinear “flat maps,” and delineated 1A/V gut microvessels and their perfusion territories as “intestinal vascular units” (IVUs). Employing IVUs, we quantified and visualized NEC-induced changes to the gut vascular phenotype. Results: In vivo imaging required 60–100 s per animal. Relative to the healthy gut, NEC intestines showed a significant overall decrease (i.e. 64–72%) in perfusion, accompanied by vasoconstriction (i.e. 9–12%) and a reduction in perfusion entropy (19%)within sections of the vascular bed. Conclusions: Multicontrast imaging coupled with IVU-based in vivo vascular phenotyping is a powerful new tool for elucidating NEC pathogenesis.