Murine Precision Cut Lung Slices as a model of heme-induced acute injury.

Abstract

<b>Background:</b> Precision Cut Lung Slices (PCLS) is an advanced, ex vivo model that has been widely introduced in respiratory research. Mouse PCLS represent a more cost-effective and more readily available model compared to human PCLS. We used mouse PCLS to investigate heme-induced acute injury. Heme is a hemolysis product with cytotoxic and pro-inflammatory properties. Elevated systemic heme levels have been associated with worse clinical outcomes in patients with sepsis and sepsis-related ARDS. <b>Methods:</b> PCLS (300µm thickness and 4mm diameter size) were obtained from 6 male C57BL/6 mice. Murine PCLS were stimulated with 100µM heme for 24h and visually inspected with a phase-contrast microscope. Cytotoxicity and viability in PCLS were measured by colorimetric LDH and XTT assays, respectively, at different concentrations and time points. In addition, inflammatory cytokines were evaluated by Multiplex and ELISAs. All experiments were performed in triplicates. <b>Results:</b> Heme-stimulated PCLS had reduced viability compared to untreated controls (p&lt;0.001 at 100µM, 24h). Additionally, strong pro-inflammatory and injury signals were observed after heme incubation. Inflammatory cytokines such as IL-6 (p=0.024), TNF-α (p&lt;0.001), G-CSF (p=0.042) and CXCL2 (p&lt;0.001) were significantly elevated in PCLS supernatants after heme. TGF-β levels were decreased after heme treatment (p&lt;0.001). Endothelial markers such as RANTES and Ang-2 levels were also significantly increased (p=0.030 and p&lt;0.001, respectively). <b>Conclusion:</b> Heme alters cell viability and induces inflammation in murine PCLS. Our data suggest that murine PCLS can be used as disease model to better understand heme-induced lung injury mechanism of action in ARDS.