# PET Imaging of CD206 Macrophages in Bleomycin-Induced Lung Injury Mouse Model

## TL;DR

This study explores using PET imaging to detect CD206 macrophages in a mouse model of lung injury, which could help understand and treat lung fibrosis.

## Contribution

The study introduces and evaluates 68Ga-labeled RP832c peptides as potential PET imaging agents for CD206 macrophages in lung injury.

## Key findings

- PET/CT signals and CD206 staining were significantly higher in bleomycin-treated mice at one week.
- Healthy mice showed minimal CD206 staining and low radiopharmaceutical accumulation.
- Both linear and cyclic [68Ga]Ga-RP832c peptides showed promise for imaging CD206 macrophages.

## Abstract

Background/Objectives: The identification of inflammatory mediators and the involvement of CD206 macrophages in anti-inflammatory responses, along with the synthesis of fibrotic mediators, are crucial for the diagnosis and treatment of Idiopathic Pulmonary Fibrosis (IPF). Methods: In this study, the assessment of 68Ga-labeled linear and cyclic forms of the RP832c peptide, which demonstrate a specific affinity for CD206 macrophages, was performed to evaluate efficacy for CD206 imaging through PET/CT, biodistribution studies, and CD206 staining in a bleomycin-induced lung injury mouse model (BLM). This model serves as a representative framework for inflammation and fibrosis. Results: The findings reveal significant peak PET/CT signals (SUV means), ID/gram values, and CD206 staining scores in lung tissues at one week post bleomycin instillation, likely due to the heightened expression of CD206 in the bleomycin-induced lung injury model. In contrast, the healthy mice exhibited no detectable CD206 staining, lower PET signals, and reduced radiopharmaceutical accumulation in lung tissues at the same timepoint. Conclusions: These findings suggest that both linear and cyclic [68Ga]Ga-RP832c may function as promising PET imaging agents for CD206 macrophages, and thereby a strategy to non-invasively explore the role of macrophages during fibrogenesis.