Imaging fibrosis in inflammatory diseases: targeting the exposed extracellular matrix

Abstract

In a variety of diseases, from benign to life-threatening ones, inflammation plays a major role. Monitoring the intensity and extent of a multifaceted inflammatory process has become a cornerstone in diagnostics and therapy monitoring. However, the current tools lack the ability to provide insight into one of its most crucial aspects, namely, the alteration of the extracellular matrix (ECM). Using a radiolabeled platelet glycoprotein VI-based ECM-targeting fusion protein (GPVI-Fc), we investigated how binding of GPVI-Fc on fibrous tissue could uncover the progression of several inflammatory disease models at different stages (rheumatoid arthritis, cutaneous delayed-type hypersensitivity, lung inflammation and experimental autoimmune encephalomyelitis). Methods: The fusion protein GPVI-Fc was covalently linked to 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and subsequently labeled with 64 Cu. We analyzed noninvasively in vivo 64 Cu-GPVI-Fc accumulation in murine cutaneous delayed-type hypersensitivity, anti-glucose-6-phosphate isomerase serum-induced rheumatoid arthritis, lipopolysaccharide-induced lung inflammation and an experimental autoimmune encephalomyelitis model. Static and dynamic Positron Emission Tomography (PET) of the radiotracer distribution was performed in vivo , with ex vivo autoradiography confirmation, yielding quantitative accumulation and a distribution map of 64 Cu-GPVI-Fc. Ex vivo tissue histological staining was performed on harvested samples to highlight the fusion protein binding to collagen I, II and III, fibronectin and fibrinogen as well as the morphology of excised tissue. Results: 64 Cu-GPVI-Fc showed a several-fold increased uptake in inflamed tissue compared to control tissue, particularly in the RA model, with a peak 24 h after radiotracer injection of up to half the injected dose. Blocking and isotype control experiments indicated a target-driven accumulation of the radiotracer in the case of chronic inflammation. Histological analysis confirmed a prolonged accumulation at the inflammation site, with a pronounced colocalization with the different components of the ECM (collagen III and fibronectin notably). Binding of the fusion protein appeared to be specific to the ECM but unspecific to particular components. Conclusion: Imaging of 64 Cu-GPVI-Fc accumulation in the ECM matrix appears to be a promising candidate for monitoring chronic inflammation. By binding to exposed fibrous tissue (collagen, fibronectin, etc.) after extravasation, a new insight is provided into the fibrotic events resulting from a prolonged inflammatory state.

Location, location, location: how the tissue microenvironment affects inflammation in RA

“…to image nascent exposure of extracellular matrix during tissue damage, and synthesis of new fibrous tissue in GPI-serum induced experimental arthritis 137 . These approaches constitute the first steps towards detailed molecular analysis of the synovial matrix in real time in vivo.…”

Multi-omics Analysis Reveals Adipose–tumor Crosstalk in Patients with Colorectal Cancer

“…In the inflammatory state, the activation of platelets via GPVI signaling has been reported to induce formation of platelet-derived microparticles in the bloodsuggesting a key role for GPVI signaling in the amplification of inflammation. Aligned with evidence that platelet microparticles are known to include transcription factors (e.g., PPARG) and cytokines and chemokines (e.g., IL1), and are hypothesized to function in interactions with other cells (50)(51)(52)(53), our multiomics study reports that key VAT signals from molecular pathways upregulated in patients with high PTGS2 tumor expression involve interacting pathways associated with fibrosis, including GPVI signaling, dendritic cell maturation, and inflammation in patients with colorectal cancer. Our findings were substantiated via independent serum-based inflammatory biomarker profiling, as the elevated expression of SAA2 and enrichment of IL6 signaling were also associated with high tumor PTGS2 expression.…”

Rheumatoid cachexia: the underappreciated role of myoblast, macrophage and fibroblast interplay in the skeletal muscle niche

“…Fibrosis has been demonstrated in several tissues from RA patients and rodent studies. For example, increased fibrous tissue deposition was demonstrated in the joint of RA rodents 6 days post induction with fluorescent visualization of collagen III and fibrinogen [90]. Similarly, research from our group has demonstrated a significant increase in collagen accumulation within the vastus lateralis, soleus and gastrocnemius muscles in CIA rodents compared to that of control rodents [38], as well as impaired molecular remodelling with fibrotic deposition and impaired cardiomyofibre contractile function [91].…”