Detection of Subclinical Arthritis in Mice by a Thrombin Receptor–Derived Imaging Agent

Abstract

Objective Functional imaging of synovitis could improve both early detection of rheumatoid arthritis (RA) and long‐term outcomes. Given the intersection of inflammation with coagulation protease activation, this study was undertaken to examine coagulation protease activities in arthritic mice with a dual‐fluorescence ratiometric activatable cell‐penetrating peptide (RACPP) that has a linker, norleucine (Nle)‐TPRSFL, with a cleavage site for thrombin. Methods K/BxN‐transgenic mice with chronic arthritis and mice with day 1 passive serum‐transfer arthritis were imaged in vivo for Cy5:Cy7 emission ratiometric fluorescence from proteolytic cleavage and activation of RACPPNleTPRSFL. Joint thickness in mice with serum‐transfer arthritis was measured from days 0 to 10. The cleavage‐evoked release of Cy5‐tagged tissue‐adhesive fragments enabled microscopic correlation with immunohistochemistry for inflammatory markers. Thrombin dependence of ratiometric fluorescence was tested by ex vivo application of RACPPNleTPRSFL and argatroban to cryosections obtained from mouse hind paws on day 1 of serum‐transfer arthritis. Results In chronic arthritis, RACPPNleTPRSFL fluorescence ratios of Cy5:Cy7 emission were significantly higher in diseased swollen ankles of K/BxN‐transgenic mice than in normal mouse ankles. A high ratio of RACPPNleTPRSFL fluorescence in mouse ankles and toes on day 1 of serum‐transfer arthritis correlated with subsequent joint swelling. Foci of high ratiometric fluorescence localized to inflammation, as demarcated by immune reactivity for citrullinated histones, macrophages, mast cells, and neutrophils, in soft tissue on day 1 of serum‐transfer arthritis. Ex vivo application of RACPPNleTPRSFL to cryosections obtained from mice on day 1 of serum‐transfer arthritis produced ratiometric fluorescence that was inhibited by argatroban. Conclusion RACPPNleTPRSFL activation detects established experimental arthritis, and the detection of inflammation by RACPPNleTPRSFL on day 1 of serum‐transfer arthritis correlates with disease progression.

Belimumab for the Treatment of Early Diffuse Systemic Sclerosis

“…GSE9285, GSE32413, and GSE45485 were used to train and test a multinomial elastic net (25,33,34). The glmnet (35) and caret (36) packages implemented in R (www.r-project.org) were used with repeated cross-validation (10×, 3-fold) to train the classifier and assess robustness (37). The inflammatory subset score was quantified as the probability of being assigned to the inflammatory molecular subset from the multinomial elastic net.…”

Detection of free DNA based on metal-enhanced fluorescence triggered by CRISPR-Cas12a and colorimetric analysis

“…Cyanine7 (Cy7), as one of the commercial NIR cyanine uorescent dyes, is well-developed in uorescent probes. [36][37][38] However, with relatively low uorescence quantum yield just like other NIR dyes, Cy7 has been rarely applied to the construction of DNA nanoswitches so far. So, why not take AuNBPs as the substrate for the design of DNA nanoswitches, which can not only quench the uorescence with near-infrared wavelength, but also enhance the uorescence with absorption/emission wavelengths consistent with their longitudinal plasmon resonance wavelengths (LPRWs)?…”

Editorial: Ratiometric Optical Imaging of Subclinical Inflammation With a Thrombin‐Cleavable Probe: A Future Tool for the In Vivo Visualization of Clinically Silent Synovitis?

“…In this issue, Friedman and colleagues report successful noninvasive in vivo imaging of established and subclinical synovitis in mouse models of inflammatory arthritis using a thrombin‐cleavable dual‐fluorescence ratiometric probe. This ratiometric activatable cell‐penetrating peptide (RACPP) probe, recently developed by this group , takes advantage of fluorescence resonance energy transfer (FRET) and thrombin cleavage.…”