# Noninvasive Optoacoustic Imaging of Oxygen Saturation Reveals Hypoxic Hematopoietic Bone Marrow during Systemic Inflammation

## TL;DR

This paper introduces a noninvasive imaging method to study oxygen levels in bone marrow during inflammation, revealing hypoxia linked to immune cell activity.

## Contribution

A novel noninvasive optoacoustic imaging approach for real-time monitoring of marrow oxygen saturation during systemic inflammation.

## Key findings

- MSOT imaging showed reduced oxygen saturation in bone marrow during LPS-induced inflammation.
- Hypoxia was confirmed with ex vivo staining and linked to increased neutrophil counts and hematopoietic activation.
- MSOT enables label-free, real-time oxygen tracking and vascular mapping in bone marrow.

## Abstract

Inflammation drives various diseases, including cardiovascular,
neurodegenerative, and oncological disorders, by altering immune cell
dynamics in hematopoietic niches. The bone marrow is the primary site
for hematopoietic stem and progenitor cell activity. Here, we present
a novel, noninvasive approach using multispectral optoacoustic tomography
(MSOT) to track oxygenation dynamics in the murine calvarial bone
marrow during acute systemic inflammation induced by lipopolysaccharide
(LPS). Our MSOT system provided real-time, label-free imaging of hemoglobin
oxygen saturation (sO2), revealing significant reductions
in sO2 levels in lipopolysaccharide-treated mice, indicative
of increased oxygen consumption. Co-registration with microCT enabled
precise vascular mapping. Hypoxia was confirmed by ex vivo Pimonidazole
staining and optical imaging and was associated with elevated neutrophil
counts and enhanced hematopoietic activation. These findings demonstrate
MSOT’s potential for noninvasive imaging of marrow oxygenation,
offering insights into inflammation-driven hematopoietic activation
and supporting the development of therapies targeting oxygen-sensitive
pathways.