Molecular mapping of articular cartilage CXCR4 expression after ACL injury via a novel small molecule-based probe.
Document Type
Article
Publication Date
6-2025
Publication Title
Bone
Abstract
PURPOSE: Molecular imaging is a powerful modality to spatially resolve molecular changes across tissues, but application to articular cartilage remains limited. CXCR4 is an established marker of chondrocyte hypertrophy and potential therapeutic target for osteoarthritis. The purpose of this study was to develop and apply a CXCR4-targeted, near-infrared fluorescent (NIR) probe to a rat model of post-traumatic osteoarthritis (PTOA).
METHODS: A CXCR4-targeted, small molecule-based NIR probe ("Cy7-AMD") was synthesized. Sensitivity and specificity of Cy7-AMD to CXCR4 was validated in vitro (HUVECs), and ex vivo (rat osteochondral explants). To induce PTOA, female Lewis rats underwent noninvasive anterior cruciate ligament (ACL) rupture. At 7- and 28-days post-injury, injured/contralateral femora and tibiae were dissected, incubated in Cy7-AMD vs a non-targeting control, and imaged via NIR imaging, as well as conventional and contrast-enhanced micro-computed tomography. Imaging datasets were co-registered, cartilage tissue volumes were segmented, and paired cartilage thickness and NIR signal maps were generated and analyzed for PTOA-relevant changes.
RESULTS: Compared to a non-targeting control probe, in vitro and ex vivo assays confirm sensitivity and specificity of Cy7-AMD to CXCR4. Flow cytometry confirmed high correspondence between Cy7-AMD- and antibody-based measurement of CXCR4 expression. Cy7-AMD rapidly equilibrated within cartilage, and fluorescent histology confirmed full-thickness penetration. Injured femoral cartilage exhibited heterogeneous CXCR4 expression, with increased signal deviation compared to contralateral femora. Spatial CXCR4 expression patterns correlated to cartilage thickness patterns; high CXCR4 expression at boundaries of low-thickness lesions suggests an association between CXCR4 expression and cartilage loss.
CONCLUSIONS: Small molecule-based probes are advantageous for mapping spatial patterns of molecular expression in rodent articular cartilage, deepening our understanding of PTOA progression.
Volume
195
First Page
117463
Recommended Citation
Newton MD, Fleischer MM, Matthew HWT, Maerz T. Molecular mapping of articular cartilage CXCR4 expression after ACL injury via a novel small molecule-based probe. Bone. 2025 Jun;195:117463. doi: 10.1016/j.bone.2025.117463. PMID: 40101879.
DOI
10.1016/j.bone.2025.117463
ISSN
1873-2763
PubMed ID
40101879
