Analysis of the Trajectory of Osteoarthritis Development in a Mouse Model by Serial Near‐Infrared Fluorescence Imaging of Matrix Metalloproteinase Activities

Abstract

Objectives A major hurdle in osteoarthritis (OA) research is the lack of sensitive detection and monitoring methods. It is hypothesized that proteases, such as matrix metalloproteinases (MMPs), are upregulated at early stages of OA development. The aim of this study was to investigate if a near infrared fluorescence (NIRF) probe activated by MMPs could visualize in vivo OA progression starting from its early stages. Methods Using an MMP activatable NIRF probe (MMPSense680), we assessed the upregulation of MMP activity in vitro by incubating human chondrocytes with the pro-inflammatory cytokine IL-1β. MMP activity was then evaluated in vivo serially in a chronic, injury-induced OA mouse model. For tracking MMP activity over time, mice were imaged 1 – 8 weeks post OA inducing surgery. Imaging results were correlated with histology. Results In vitro studies confirmed that NIRF imaging could identify enhanced MMP activity in IL-1β-treated human chondrocytes. In vivo imaging showed significantly higher fluorescent intensity in OA knees compared to sham knees (control) of the same mice. Additionally, the total emitted fluorescence intensity steadily increased over the entire course of OA progression that was examined. NIRF imaging results correlated with histological analysis, which showed an increase in articular cartilage structural damage over time. Conclusions Imaging of MMP activity in an OA mouse model provided sensitive and consistent visualization of OA progression, beginning from the early stages of OA. In addition to facilitating the preclinical study of OA modulators, this approach has the potential for future human translation.

In Vivo Imaging of MMP‐13 Activity Using a Specific Polymer‐FRET Peptide Conjugate Detects Early Osteoarthritis and Inhibitor Efficacy

“…Currently there are a few molecular probes available to image specific protease activities in vivo in articular joints, but as previously pointed out, they have limitations and several parameters need to be optimized to foster their application to image OA progression. Furthermore, multiple proteases most likely act in different combinations at different progressive stages of OA.…”

“…In our study PGA‐P‐ 18 was administered systemically and we detected specifically MMP‐13 activity in the affected joints. More recently, Leahy et al detected increased MMP activity at 4 weeks after DMM surgery in mice. While their study is interesting, they used the general MMP probe MMPSense 680, which does not discriminate specific MMP activity, avoiding conclusions regarding the identity of the MMP(s) cleaving this probe.…”

Using mouse models to investigate the pathophysiology, treatment, and prevention of post‐traumatic osteoarthritis

“…Standard imaging such as radiographic joint space narrowing or 3T‐MRI lack sensitivity to detect cartilage damage in mice, impeding clinical translation . Recent technological advances and development of novel imaging modalities may bridge this gap Unlike humans, meniscal ossification is a common feature even in normal mouse knee joints, limiting the translational value of exploring molecular changes in this tissue in PTOA.…”

Design, construction, and biological testing of an implantable porous trilayer scaffold for repairing osteoarthritic cartilage

“…To evaluate the degradation of the scaffolds for cartilage regeneration in vivo, a total of seven male C57BL/6Jico 12 weeks old mice were purchased from Charles River, France. Two of them were kept healthy as negative control, and five were injected with collagenase in the left knee to achieve the chemically induced OA (Leahy et al, ). Non‐cell scaffolds (1 mm 3 cubes) were grafted into five OA mice and two healthy controls and then studied for in vivo stability over 35 days.…”