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Biomedical Imaging and Instrumentation

Biomedical Imaging and Instrumentation - Poster Session A

Poster F8 - AGE-DEPENDENT VASCULAR RESPONSES TO EXPERIMENTAL ENDOTOXEMIA IN NEONATAL RAT PUPS ASSESSED USING PHOTOACOUSTIC IMAGING

Thursday, October 24, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

AD

Arion Dey (he/him/his)

Student
Wake Forest University School of Medicine
Aurora, Illinois, United States

Primary Investigator(s)

JW

Jared Weis, PhD

Assistant Professor
Wake Forest University School of Medicine, United States

Last Author(s)

VW

Victoria Weis, PhD

Assistant Professor
Wake Forest Institute for Regenerative Medicine, United States

Co-Author(s)

GD

Gia Dadhania

Student
Wake Forest Institute for Regenerative Medicine, United States

Introduction: Using translational in vivo photoacoustic imaging (PAI) methods, we have previously shown significant differences in intestinal function with decreased intestinal tissue oxygenation and motility in an experimental model of necrotizing enterocolitis (NEC) [1], a devastating and life-threatening intestinal disease affecting premature infants. However, changes in intestinal function due to endotoxemia and generalized systemic inflammation are unknown but may confound NEC diagnosis with overlapping physiological changes in the intestine. In this study, we sought to measure oxygenation, blood volume, and motility in the developing intestine using an experimental neonatal animal model of endotoxemia to assess intestinal vascular and motility responses to inflammation. To assess the potential of PAI for specific diagnostic measures of infant intestinal disease, we also compared our results to prior results obtained in our NEC animal model.

Materials and

Methods: 2-day and 4-day-old rat pups were given a single injection of lipopolysaccharide (LPS) at a sub-septic dose (5 mg/kg, IP) to induce systemic inflammation as an experimental model of acute endotoxemia (n = 5). Non-injected 2-day and 4-day old rat pups were used as healthy controls (n = 5). In a second cohort, pups received 2 injections of LPS on Day 2 and Day 4 of life as an experimental model of more severe endotoxemia in early life. Four-to-six-hours post-LPS administration, rat pups were imaged via ultrasound and PAI (Vevo F2 LAZR-X) to assess intestinal vasculature and intestinal motility. Vascular assessments yielded measures of intestinal tissue oxygen saturation (sO2) and total hemoglobin (HbT) as measures of intestinal hypoxia and intestinal blood volume, respectively. Motility measures were analyzed from high-frequency ultrasound imaging video data using computational deformation analysis to yield a spatial map of the intestinal motility index, quantifying a combined measure of intestinal peristaltic motility strength and frequency. Statistical analysis was performed using GraphPad Prism.

Results, Conclusions, and Discussions:

Results: In the 2-day old animals, LPS pups exhibited a statistically significant hyperemia response with a 2.22-fold increase in HbT as compared to controls (p < 0.0001). Conversely, in the 4-day old animals, LPS pups showed no significant differences in HbT as compared to controls. No changes in intestinal sO2 or motility were observed in either 2- or 4-day old LPS rat pups. No significant differences were found in 4-day old pups receiving 2 LPS injections compared to 1 injection. In contrast, NEC pups show a 0.79- and 0.69-fold decrease in sO2 as compared to controls at 2- and 4-days old (p < 0.05, p < 0.01), respectively, with no significant differences in HbT. NEC pups also show a 0.50- and 0.54-fold decease in intestinal motility compared to controls at 2- and 4-days old (p < 0.001, p < 0.05).

Discussion: The neonatal rat experimental endotoxemia model used in this study corroborates the many facets of histological damage and aligns with human endotoxemia cases. The endotoxemia rat model has been shown to have inflammatory effects throughout the body, including the intestines. With samples at 2-Days and 4-days following LPS injections, this endotoxemia model establishes a time course illustrating the response of the neo-natal immune system to endotoxicity and contrasting it to the appearance of early disease initiation and progression/establishment of NEC, which further helps elucidate generalized inflammation versus NEC.

Conclusions: Our results in 2- and 4-day old LPS-treated rat pups demonstrate an age-dependent inflammatory vascular response to endotoxemia. 2-day old endotoxemia pups exhibit an exaggerated hyperemia response as compared to 4-day old endotoxemia pups, with no changes in intestinal tissue oxygenation or motility. Our results also demonstrate that the combined metrics of intestinal oxygenation, blood volume, and motility assessed using combined ultrasound/PAI imaging measures can discriminate between healthy, endotoxemia, and NEC animals, providing significant motivation for continued translational efforts to enhance diagnostic imaging technology for premature infant intestinal diseases.

Acknowledgements (Optional): These studies were supported by the Wake Forest Institute for Regenerative Medicine Pilot Award, NIH-NIDDK R01DK135955, NIH-NIDDK K01DK125633, and American Gastroenterological Association Research Scholar Award in Health Disparities.