Optical tomographic imaging discriminates between disease-modifying anti-rheumatic drug (DMARD) and non-DMARD efficacy in collagen antibody-induced arthritis

Baricitinib ameliorates inflammatory and neuropathic pain in collagen antibody-induced arthritis mice by modulating the IL-6/JAK/STAT3 pathway and CSF-1 expression in dorsal root ganglion neurons

BACKGROUND

Janus kinase (JAK) inhibitors, such as baricitinib, are widely used to treat rheumatoid arthritis (RA). Clinical studies show that baricitinib is more effective at reducing pain than other similar drugs. Here, we aimed to elucidate the molecular mechanisms underlying the pain relief conferred by baricitinib, using a mouse model of arthritis.

METHODS

We treated collagen antibody-induced arthritis (CAIA) model mice with baricitinib, celecoxib, or vehicle, and evaluated the severity of arthritis, histological findings of the spinal cord, and pain-related behaviours. We also conducted RNA sequencing (RNA-seq) to identify alterations in gene expression in the dorsal root ganglion (DRG) following baricitinib treatment. Finally, we conducted in vitro experiments to investigate the direct effects of baricitinib on neuronal cells.

RESULTS

Both baricitinib and celecoxib significantly decreased CAIA and improved arthritis-dependent grip-strength deficit, while only baricitinib notably suppressed residual tactile allodynia as determined by the von Frey test. CAIA induction of inflammatory cytokines in ankle synovium, including interleukin (IL)-1β and IL-6, was suppressed by treatment with either baricitinib or celecoxib. In contrast, RNA-seq analysis of the DRG revealed that baricitinib, but not celecoxib, restored gene expression alterations induced by CAIA to the control condition. Among many pathways changed by CAIA and baricitinib treatment, the interferon-alpha/gamma, JAK-signal transducer and activator of transcription 3 (STAT3), and nuclear factor kappa B (NF-κB) pathways were considerably decreased in the baricitinib group compared with the celecoxib group. Notably, only baricitinib decreased the expression of colony-stimulating factor 1 (CSF-1), a potent cytokine that causes neuropathic pain through activation of the microglia-astrocyte axis in the spinal cord. Accordingly, baricitinib prevented increases in microglia and astrocytes caused by CAIA. Baricitinib also suppressed JAK/STAT3 pathway activity and Csf1 expression in cultured neuronal cells.

CONCLUSIONS

Our findings demonstrate the effects baricitinib has on the DRG in relation to ameliorating both inflammatory and neuropathic pain.

Antiarthritic activity of Physalis peruviana fruit extract via inhibition of inflammatory mediators: Integrated in vitro, in vivo and in silico study

ETHNOPHARMACOLOGICAL RELEVANCE

P. peruviana fruit, native to Andean region, is cultivated worldwide for its adaptability to various soil natures and climatic conditions. It is increasingly consumed for its high nutritional profile and history of ethnomedical uses including treatment of arthritis. Little pharmacological evidences support this folk use except for previous in vitro study that reported significant inhibition of protein denaturation.

AIM OF THE STUDY

The study aims at providing new in vivo evidence on antiarthritic activity of P. peruviana fruits in vivo that justifies its traditional use through mechanism-based experiment.

MATERIAL AND METHODS

Inhibition of inflammatory mediators is considered one of the key treatments to alleviate painful symptoms of rheumatoid arthritis (RA). Anti-inflammatory activity was assessed against COX-1 and COX-2 activity in vitro. Serum TNFα, IL-1β and IL-6 were traced using in vivo model of adjuvant-induced arthritis. Gross/inflammatory changes in rat paw, relative mass indices of spleen and liver were further investigated together with joint tissue histoarchitecture. Seven metabolites from different phytochemical classes, that were previously reported in P. peruviana fruit, were evaluated in silico against TNF-α target protein (PDB ID: 2AZ5) to assess their inhibitory effect. This was followed by assessment of their drug-likeness based on Lipinski's rule according to their physicochemical and pharmacokinetic properties.

RESULTS

High dose of extract (E-1000 mg) improved adjuvant-induced cachexia and attenuated immune-inflammatory responses in paw and serum parameters, with equipotent effect to MTX, in addition to minimal side effect profile on spleen and liver. Histopathological study of knee joint tissues confirmed dose-dependent improvement in arthritic groups treated with P. peruviana fruit extracts. The insilico study recommended steroidal lactones withaperuvin E/C and hydroxywithanolide E as promising lead compounds for inhibiting TNF enzyme as evidenced by docking scores of 6.301, 5.488 and 5.763 kcal/mol, respectively, fitting as well the Lipinski's rule of drug likeness.

CONCLUSION

The study provided novel approach that rationalize folk use of P. peruviana fruit in treatment of arthritis.

Enhancing Prednisone-Based Arthritis Therapy with Targeted IL-27 Gene Delivery

Rheumatoid arthritis (RA) is a chronic autoimmune disease which is characterized primarily by synovial hyperplasia and accumulation of several types of immune infiltrates that promote progressive destruction of the articular structure. Glucocorticoids are often prescribed to treat RA because of their strong anti-inflammatory and immunosuppressive effects. However, their application must be limited to the short-term due to a risk of adverse events. In the present study, we examined the potential combination of low-dose prednisone with gene delivery of an agent of promising and complementary effectiveness in RA, interleukin (IL)-27. IL-27 has been shown to have anti-inflammatory potential, while also acting as an effective bone-normalization agent in prior reports. The present report examined a version of IL-27 targeted at the C-terminus with a short ‘peptide L’ (pepL, LSLITRL) that binds the interleukin 6 receptor α (IL-6Rα) upregulated during inflammation. By focusing on this targeted form, IL-27pepL or 27pL, we examined whether the anti-inflammatory potential of prednisone (at a relatively low dose and short duration) could be further enhanced in the presence of 27pL as a therapy adjuvant. Our results indicate that 27pL represents a novel tool for use as an adjuvant with current therapeutics, such as prednisone, against inflammatory conditions.

MicroRNA‑1 regulates the development of osteoarthritis in a Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 mouse model of osteoarthritis through the downregulation of Indian hedgehog expression

The present study assessed the effects of microRNA‑1 (miR‑1) on the development of osteoarthritis using human tissues and a Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 mouse model of osteoarthritis. Human cartilage tissues (n=20) were collected for reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), histological analysis and immunohistochemistry experiments. A transgenic mouse model of osteoarthritis was established by subjecting Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 transgenic mice to anterior cruciate ligament transection (ACLT). Mice were subjected to radiography and in vivo fluorescence molecular tomography (FMT), while mouse tissues were collected for histological analysis, RT‑qPCR and Safranin O staining. It was found that the miR‑1 level was downregulated, whereas the levels of Indian hedgehog (Ihh), as well as those of its downstream genes were upregulated in human osteoarthritic cartilage. In the transgenic mice, treatment with tamoxifen induced miR‑1, as well as collagen, type II (Col2a1) and Aggrecan (Acan) expression; however, it decreased Ihh, glioma‑associated oncogene homolog (Gli)1, Gli2, Gli3, smoothened homolog (Smo), matrix metalloproteinase (MMP)‑13 and collagen type X (Col10) expression. Safranin O staining revealed cartilage surface damage in the non‑tamoxifen + ACLT group, compared with that in the tamoxifen + ACLT group. Histologically, an intact cartilage surface and less fibrosis were observed in the tamoxifen + ACLT group. Immunohistochemistry revealed that the protein expression of Ihh, Col10, and MMP‑13 was significantly higher in the joint tissues of the non‑tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. However, Col2a1 expression was lower in the joint tissues of the non‑tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. The results of RT‑qPCR and FMT further confirmed these findings. On the whole, the findings of the present study demonstrate that miR‑1 expression protects against osteoarthritis‑induced cartilage damage and gene expression by inhibiting Ihh signaling.

Paradigms in Fluorescence Molecular Imaging: Maximizing Measurement of Biological Changes in Disease, Therapeutic Efficacy, and Toxicology/Safety

Fluorescence molecular imaging (MI) is an important concept in preclinical research that focuses on the visualization of cellular and biological function in a non-invasive fashion to better understand in vivo disease processes and treatment effects. MI differs fundamentally from traditional preclinical imaging strategies in that it generally relies on reporter probes specific for particular targets or pathways that can be used to reveal biological changes in situ, at the site(s) of disease. In contrast, the more established imaging modalities, like magnetic resonance imaging, X-ray, micro X-ray computed tomography, and ultrasound, historically have relied primarily on late-stage anatomical or physiologic changes. The practical application of fluorescence MI, however, has drifted somewhat from the emphasis on quantifying biology, and based on the publication record, it now appears to include any imaging in which a probe or contrast agent is used to non-invasively acquire in vivo endpoint information. Unfortunately, the mere use of a defined biologically specific probe, in the absence of careful study design, does not guarantee that any useful biological information is actually gained, although often useful endpoint results still can be achieved. This review proposes to add subcategories of MI, termed MI biological assessment (or MIBA), that emphasize a focus on obtaining early and clear biological changes associated with disease development, therapeutic efficacy, and drug-induced tissue changes. Proper selection of probes and careful study design are critical for maximizing the non-invasive assessment of in vivo biological changes, and applications of these critical elements are described.

Harnessing the Power of Optical Microscopic and Macroscopic Imaging for Natural Products as Cancer Therapeutics

Natural products (NPs) are an important source for new drug discovery over the past decades, which have been demonstrated to be effectively used in cancer prevention, treatment, and adjuvant therapy. Many methods, such as the genomic and metabolomic approaches, immunochemistry, mass spectrometry, and chromatography, have been used to study the effects of NPs on cancer as well as themselves. Because of the advantages in specificity, sensitivity, high throughput, and cost-effectiveness, optical imaging (OI) approaches, including optical microscopic imaging and macroscopic imaging techniques have also been applied in the studies of NPs. Optical microscopic imaging can observe NPs as cancer therapeutics at the cellular level and analyze its cytotoxicity and mechanism of action. Optical macroscopic imaging observes the distribution, metabolic pathway, and target lesions of NPs in vivo, and evaluates NPs as cancer therapeutics at the whole-body level in small living animals. This review focuses on the recent advances in NPs as cancer therapeutics, with particular emphasis on the powerful use of optical microscopic and macroscopic imaging techniques, including the studies of observation of ingestion by cells, anticancer mechanism, and in vivo delivery. Finally, we prospect the wider application and future potential of OI approaches in NPs as cancer therapeutics.

Adenovirus-mediated transduction with Histone Deacetylase 4 ameliorates disease progression in an osteoarthritis rat model

BACKGROUND

Downregulation of histone deacetylase-4 (HDAC4) contributes to cartilage degeneration in osteoarthritis (OA) because it promotes upregulation of runt-related transcription factor-2 (Runx-2) and osteoarthritis-related genes. The effect of HDAC4 upregulation on cartilage damage in OA remains unknown.

METHODS

Rat chondrocytes were infected with Ad-GFP or Ad-HDAC4-GFP for 48 h, stimulated with interleukin-1β (IL-1β, 10 ng/mL) for 24 h, and then harvested for RT-qPCR. Male Sprague-Dawley rats in 3 groups were given anterior cruciate ligament transection (ACLT) or sham operation, and knee injections with different adenovirus (Ad) vectors at 48 h after surgery and every 3 weeks thereafter: ACLT+Ad-GFP (n = 17); ACLT+Ad-HDAC4-GFP (n = 20); and sham+Ad-GFP (n = 15). Three ACLT-Ad-HDAC4-GFP rats were sacrificed at different times to examine the expression of HDAC4. Two ACLT-Ad-GFP rats and two ACLT-Ad-HDAC4-GFP rats were euthanized at week-2; articular cartilage was harvested and expression of HDAC4 was determined by RT-qPCR. All other rats were euthanized at week-8. Cartilage damage and OA progression was assessed using radiography, fluorescence molecular tomography (FMT), histology, immunohistochemistry (IHC), ELISA, and RT-qPCR.

RESULTS

Overexpression of HDAC4 in chondrocytes stimulated by IL-1β reduced the levels of Runx-2, MMP-13, and Collagen X, but increased the levels of Collagen II and Aggrecan. Upregulation of HDAC4 reduced osteophyte formation and cartilage damage, and increased articular cartilage anabolism.

CONCLUSION

HDAC4 attenuated articular cartilage damage by repression of Runx-2, MMP-13, and collagen X and induction of collagen II and ACAN in this rat model of OA. Upregulation of HDAC4 may provide chondroprotection in OA patients.

Effect of methotrexate on collagen-induced arthritis in male Wistar rats

To evaluate the effect of methotrexate on collagen-induced arthritis, micro-computed tomography (micro-CT) and histopathological analyses were used in male Wistar rats. Rats were divided randomly into three groups. Group 1 was treated with 0.9% saline, and groups 2 and 3 were boosted with type Ⅱ collagen. From day 21 to 42, groups 1 and 2 were orally treated with 0.9% saline and group 3 was orally treated with 1.5 mg/kg methotrexate. All rats were sacrificed at day 42 after the first collagen treatment. Micro-CT analyses showed bony parameters, such as bone volume and trabecular number, were decreased in group 2 compared to group 1, and these parameters were recovered in group 3. Histopathological examination and pathological parameter scoring showed that the knee joints of rats in group 2 had severe joint destruction, showing cartilage and bone erosion, enlarged cavities with inflammatory cell infiltration and activation of synovial fibroblasts. By contrast, these changes were reduced in group 3. Taken together, methotrexate treatment showed therapeutic potential in male rat collagen-induced arthritis model, and micro-CT analysis and histopathological tools could be integrated to assess the quantification/qualification of arthritic lesions.

Whole-Body Physiologically Based Pharmacokinetic Modeling of Trastuzumab and Prediction of Human Pharmacokinetics

In the present study, we evaluated the pharmacokinetics (PK) of trastuzumab and sought to predict human PK based on animal studies, through the use of optical imaging and a whole-body physiologically based pharmacokinetic (WB-PBPK) modeling approach. The PK study was conducted in 24 mice, where serial blood samples were withdrawn and major organs were isolated after the last blood withdrawal. The drug concentrations in blood and major organs were measured via optical imaging. The WB-PBPK model was constructed using known physiological values including the volumes of major organs and blood/lymphatic flow. The NONMEM software (version 7.3) was used to determine tissue partition coefficients. Using the WB-PBPK model, a clinical trial simulation was performed with reference to human physiological values acquired from the literature. The simulated human PK was then compared with the actual PK observed in the previous study in which healthy male subjects received 6 mg/kg trastuzumab (Herceptin^®) via intravenous route. The ratio of the simulated versus observed area under the concentration-time curve was 1.02 and that of maximal concentration was 0.72. The current study describes the potential synergistic applications of WB-PBPK and optical imaging in human PK prediction based on preclinical data obtained in early-stage drug development.

Early supplemental α2-macroglobulin attenuates cartilage and bone damage by inhibiting inflammation in collagen II-induced arthritis model

OBJECTIVE

To determine if early supplemental intra-articular α2-macroglobulin (A2M) has a chondroprotective effect in a collagen II-induced arthritis (CIA) mice model.

METHODS

DBA/1 mice were randomized into four groups (n = 15/group): (a) CIA + 1.2 μg of A2M; (b) CIA + 0.8 μg of A2M; (c) CIA + 0.4 μg of A2M; (d) vehicle + phosphate-buffered saline (PBS). A2M was injected into right ankles and PBS was injected into the left ankles simultaneously as internal control at days 36, 43 and 50. The CIA inflammation clinical score and ankle thickness were recorded every other day starting on day 21 until sacrifice. Changes in inflammation were monitored by in vivo fluorescence molecular tomography (FMT). Inflammation, cartilage and bone damage were assessed with X-ray, histology and immunohistochemistry. Cartilage and inflammation-related gene expression was quantified by real-time polymerase chain reaction (PCR).

RESULTS

All mice showed ankle inflammation on day 33. After day 43, lower clinical scores, ankle thickness and Sharp/van der Heijde method scores in A2M-treated ankles compared with PBS-treated ankles. FMT data indicated that the inflammation markers MMPSense and ProSense were significantly elevated in the PBS-treated ankles than A2M-treated ankles. Histology and X-ray analyses indicated that A2M administration resulted in lower levels of inflammatory infiltration and synovial hyperplasia, as well as more typical cartilage and bone organization with increased COL II and Aggrecan staining when compared with PBS-treated ankles. In addition, real-time PCR showed that,matrix metalloproteinase-3, -9, -13, COL X and Runx2 were significantly less expressed in A2M-treated groups than PBS-treated animals.

CONCLUSION

Early supplemental intra-articular A2M exerts an anti-inflammatory effect and attenuates cartilage and bone damage in a CIA model.

Evaluation of the anti-arthritic activity of Cinnamomum cassia bark extract in experimental models

BACKGROUND

Cinnamomum cassia iswidely used as a traditional medicinal plant for the treatment of rheumatoid arthritis.

OBJECTIVE

The present study aimed to assess the anti-arthritic activity of C. cassia bark hydroalcoholic extract (CCHE) in different arthritic animal models.

METHODS

In formaldehyde model, sub-plantar administration of 0.1 ml of formaldehyde (2% v/v) into the right hind paws of Wistar albino rats on days 0 and 3. The rats were divided into six groups as follows: normal control, disease control, indomethacin group (3 mg/kg, p.o.) and three groups, treated with 50, 100 and 200 mg/kg CCHE (p.o.). Joint diameter was measured, and ankle joints were collected for MDA and GSH measurements. In complete Freund's adjuvant (CFA)-induced arthritis model, CFA was injected into the sub-plantar surface of the right hind paw in rats. Joint diameter was measured, and serum TNF-α and IL-1β were measured. Histopathological and immunohistochemical analyses were also performed.

RESULTS

CCHE treatment significantly (p < 0.01) reduced MDA levels and joint swelling in a concentration-dependent manner in rats with formaldehyde-induced arthritis, in which GSH levels were elevated (p < 0.01). In rats with CFA-induced arthritis, CCHE treatment significantly reduced joint swelling as well as IL-1β and TNF-α levels (p < 0.01). TNF-α receptor expression was decreased in rats treated with indomethacin or CCHE.

CONCLUSION

Based on these findings, it can be concluded that C. cassia possesses anti-arthritic properties.

A novel therapeutic strategy for cartilage diseases based on lipid nanoparticle-RNAi delivery system

Background

Cartilage degeneration affects millions of people but preventing its degeneration is a big challenge. Although RNA interference (RNAi) has been used in human trials via silencing specific genes, the cartilage RNAi has not been possible to date because the cartilage is an avascular and very dense tissue with very low permeability.

Purpose

The objective of this study was to develop and validate a novel lipid nanoparticle (LNP)-siRNA delivery system that can prevent cartilage degeneration by knocking down specific genes.

Methods

LNP transfection efficiency was evaluated in vitro and ex vivo. Indian Hedgehog (Ihh) has been correlated with cartilage degeneration. The in vivo effects of LNP-Ihh siRNA complexes on cartilage degeneration were evaluated in a rat model of surgery-induced osteoarthritis (OA).

Results

In vitro, 100% of chondrocytes were transfected with siRNA in the LNP-siRNA group. In accordance with the cell culture results, red positive signals could be detected even in the deep layer of cartilage tissue cultures treated by LNP-beacon. In vivo data showed that LNP is specific for cartilage, since positive signals were detected by fluorescence molecular tomography and confocal microscopy in joint cartilage injected with LNP-beacon, but not on the surface of the synovium. In the rat model of OA, intraarticular injection of LNP-Ihh siRNA attenuated OA progression, and PCR results showed LNP-Ihh siRNA exerted a positive impact on anabolic metabolism and negative impact on catabolic metabolism.

Conclusion

This study demonstrates that our LNP-RNAi delivery system has a significantly chondroprotective effect that attenuates cartilage degeneration and holds great promise as a powerful tool for treatment of cartilage diseases by knocking down specific genes.

Fluorescence Detection of Cell Death in Liver of Mice Treated with Thioacetamide

The purpose of this study was to detect cell death in the liver of mice treated with thioacetamide (TAA) using fluorescence bioimaging and compare this outcome with that using conventional histopathological examination. At 6 weeks of age, 24 mice were randomly divided into three groups: group 1 (G1), control group; group 2 (G2), fluorescence probe control group; group 3 (G3), TAA-treated group. G3 mice were treated with TAA. Twenty-two hours after TAA treatment, G2 and G3 mice were treated with Annexin-Vivo 750. Fluorescence in vivo bioimaging was performed by fluorescence molecular tomography at two hours after Annexin-Vivo 750 treatment, and fluorescence ex vivo bioimaging of the liver was performed. Liver damage was validated by histopathological examination. In vivo bioimaging showed that the fluorescence intensity was increased in the right upper part of G3 mice compared with that in G2 mice, whereas G1 mice showed no signal. Additionally ex vivo bioimaging showed that the fluorescence intensity was significantly increased in the livers of G3 mice compared with those in G1 or G2 mice (p < 0.05). Histopathological examination of the liver showed no cell death in G1 and G2 mice. However, in G3 mice, there was destruction of hepatocytes and increased cell death. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining confirmed many cell death features in the liver of G3 mice, whereas no pathological findings were observed in the liver of G1 and G2 mice. Taken together, fluorescence bioimaging in this study showed the detection of cell death and made it possible to quantify the level of cell death in male mice. The outcome was correlated with conventional biomedical examination. As it was difficult to differentiate histological location by fluorescent bioimaging, it is necessary to develop specific fluorescent dyes for monitoring hepatic disease progression and to exploit new bioimaging techniques without dye-labeling.

Luminescent Probe Based Techniques for Hypoxia Imaging

Hypoxia is a condition of tissue environments wherein a lower than normal level of oxygen is available, and it serves as the root cause and indicator of various diseases. Detection of hypoxia in tumors is imperative for furthering our understanding of the pathological effects and the development of proper treatments, as it is well established that hypoxic tumors are able to impede the cancer treatment process by being resistant to many therapies. It is important therefore to be able to detect hypoxia in tissues and tumors through in vivo imaging methods. A growing area for detection of hypoxia in vivo is the use of fluorescent/luminescent probes which has accelerated in recent years. The continued quest for improvements in selectivity and sensitivity has inspired researchers to pursue new strategies for fluorescence/luminescent probe design. This review will discuss various luminescent probes based on small molecules, dyes, macromolecules, and nanoparticles for sensitive and specific detection of oxygen levels directly or by indirect mechanisms such as the presence of enzymes or related factors that arise in a hypoxic environment. Following the particular mechanism of detection, each probe has specific structural and photophysical properties which permit its selectivity and sensitivity. These probes show promise in terms of low toxicity and high specificity among other merits discussed, and in providing new dimensions for hypoxia detection, these works contribute to future potential methods for clinical diagnosis of hypoxic tissues and tumors.

Early Detection of Acute Drug-Induced Liver Injury in Mice by Noninvasive Near-Infrared Fluorescence Imaging

Hepatocellular and cholestatic forms of drug-induced liver injury (DILI) are major reasons for late-stage termination of small-molecule drug discovery research projects. Biochemical serum markers are limited in their ability to sensitively and specifically detect both of these common DILI forms in preclinical models, and tissue-specific approaches to assessing this are labor intensive, requiring extensive animal dosing, tissue preparation, and pathology assessment. In vivo fluorescent imaging offers noninvasive detection of biologic changes detected directly in the livers of living animals. Three different near-infrared fluorescent imaging probes, specific for cell death (Annexin-Vivo 750), matrix metalloproteases (MMPSense 750 FAST), and transferrin receptor (Transferrin-Vivo 750) were used to measure the effects of single bolus intraperitoneal doses of four different chemical agents known to induce liver injury. Hepatocellular injury–inducing agents, thioacetamide and acetaminophen, showed optimal injury detection with probe injection at 18–24 hours, the liver cholestasis-inducing drug rifampicin required early probe injection (2 hours), and chlorpromazine, which induces mixed hepatocellular/cholestatic injury, showed injury with both early and late injection. Different patterns of liver responses were seen among these different imaging probes, and no one probe detected injury by all four compounds. By using a cocktail of these three near-infrared fluorescent imaging probes, all labeled with 750-nm fluorophores, each of the four different DILI agents induced comparable tissue injury within the liver region, as assessed by epifluorescence imaging. A strategy of probe cocktail injection in separate cohorts at 2 hours and at 20–24 hours allowed the effective detection of drugs with either early- or late-onset injury.

Diagnosis and management of rheumatoid arthritis; What is the current role of established and new imaging techniques in clinical practice?

Ultrasound and magnetic resonance imaging (MRI) have become established imaging techniques for the management of rheumatoid arthritis. Several publications have pointed out the advantages of these techniques for a more complete evaluation of the inflammation and structural damage at joint level. Recently new imaging techniques as the positron emission tomography (PET) associated with computed tomography (CT) or MRI scan, and the optical imaging have been introduced in the panorama. This article presents the advantages and limitations of each imaging techniques in light with the recent publications.

T Cell-Independent Mechanisms Associated with Neutrophil Extracellular Trap Formation and Selective Autophagy in IL-17A-Mediated Epidermal Hyperplasia

IL-17A has been strongly associated with epidermal hyperplasia in many cutaneous disorders. However, because IL-17A is mainly produced by αβ and γδT cells in response to IL-23, the role of T cells and IL-23 has overshadowed any IL-17A-independent actions. In this article, we report that IL-17A gene transfer induces epidermal hyperplasia in Il23r^-/-Rag1^-/-- and Tcrδ-deficient mice, which can be prevented by neutrophil depletion. Moreover, adoptive transfer of CD11b⁺Gr-1^hi cells, after IL-17A gene transfer, was sufficient to phenocopy the disease. We further show that the IL-17A-induced pathology was prevented in transgenic mice with impaired neutrophil extracellular trap formation and/or neutrophils with conditional deletion of the master regulator of selective autophagy, Wdfy3. Our data demonstrate a novel T cell-independent mechanism that is associated with neutrophil extracellular trap formation and selective autophagy in IL-17A-mediated epidermal hyperplasia.

Assessment of collagen antibody-induced arthritis in BALB/c mice using bioimaging analysis and histopathological examination

The aim of this study was to examine the therapeutic potential of sulfasalazine and prednisolone in a mouse collagen antibody-induced arthritis (CAIA) model. Twenty-five male BALB/c mice were randomly divided into five groups: group 1 (G1): control, group 2 (G2): probe control, group 3 (G3): CAIA, group 4 (G4): CAIA+sulfasalazine (10 mg/kg, oral), and group 5 (G5): CAIA+prednisolone (100 mg/kg, oral). Fluorescence bioimaging was performed in vivo 24 and 48 h after treatment with a fluorescence probe (OsteoSense® 680 EX), and all mice were sacrificed. The hind knee joints were fixed in 10% neutral phosphate-buffered formalin, and micro-computed tomography (micro-CT) and histopathological analyses were performed. The paw thickness increased in a time-dependent manner in G3 mice, but trended toward a decrease in both G4 and G5 mice. Fluorescence intensity increased in G3 mice at 24 and 48 h after fluorescence probe treatment, but the fluorescence intensity in G4 and G5 mice was lower than that in G3. Micro-CT analyses showed that the joint surfaces of G3 mice had a rough and irregular articular appearance, but the occurrence of these irregularities was lower in G4 and G5. Hematoxylin and eosin and Safranin O-fast green staining confirmed that destruction of the cartilage and bony structures, synovial hyperplasia, and inflammatory cell infiltration all occurred in G3, and that the occurrence of these phenomena was lower in G4 and G5 than in G3. Taken together, these results suggest that sulfasalazine and prednisolone can reduce acute rheumatoid arthritis in mice.

The X-Linked Inhibitor of Apoptosis Protein Inhibitor Embelin Suppresses Inflammation and Bone Erosion in Collagen Antibody Induced Arthritis Mice

Objective. To investigate the effect of Embelin, an inhibitor of X-Linked Inhibitor of Apoptosis Protein (XIAP), on inflammation and bone erosion in a collagen antibody induced arthritis (CAIA) in mice. Methods. Four groups of mice (n = 6 per group) were allocated: CAIA untreated mice, CAIA treated with Prednisolone (10 mg/kg/day), CAIA treated with low dose Embelin (30 mg/kg/day), and CAIA treated with high dose Embelin (50 mg/kg/day). Joint inflammation was evaluated using clinical paw score and histological assessments. Bone erosion was assessed using micro-CT, tartrate resistant acid phosphatase (TRAP) staining, and serum carboxy-terminal collagen crosslinks (CTX-1) ELISA. Immunohistochemistry was used to detect XIAP protein. TUNEL was performed to identify apoptotic cells. Results. Low dose, but not high dose Embelin, suppressed inflammation as reflected by lower paw scores (P < 0.05) and lower histological scores for inflammation. Low dose Embelin reduced serum CTX-1 (P < 0.05) and demonstrated lower histological score and TRAP counting, and slightly higher bone volume as compared to CAIA untreated mice. XIAP expression was not reduced but TUNEL positive cells were more abundant in Embelin treated CAIA mice. Conclusion. Low dose Embelin suppressed inflammation and serum CTX-1 in CAIA mice, indicating a potential use for Embelin to treat pathological bone loss.

Attenuation of cartilage pathogenesis in post-traumatic osteoarthritis (PTOA) in mice by blocking the stromal derived factor 1 receptor (CXCR4) with the specific inhibitor, AMD3100

SDF-1 was found to infiltrate cartilage, decrease proteoglycan content, and increase MMP-13 activity after joint trauma. In this study, we tested the hypothesis that interference of the SDF-1/CXCR4 signaling pathway via AMD3100 can attenuate pathogenesis in a mouse model of PTOA. We also tested the predictive and confirmatory power of fluorescence molecular tomography (FMT) for cartilage assessment. AMD3100 was continuously delivered via mini-osmotic pumps. The extent of cartilage damage after AMD3100 or PBS treatment was assessed by histological analysis 2 months after PTOA was induced by surgical destabilization of the medial meniscus (DMM). Biochemical markers of PTOA were assessed via immunohistochemistry and in vivo fluorescence molecular tomography (FMT). Regression analysis was used to validate the predictive power of FMT measurements. Safranin-O staining revealed significant PTOA damage in the DMM/PBS mice, while the DMM/AMD3100 treated mice showed a significantly reduced response with minimal pathology. Immunohistochemistry showed that AMD3100 treatment markedly reduced typical PTOA marker expression in chondrocytes. FMT measurements showed decreased cathepsins and MMP activity in knee joints after treatment. The results demonstrate that AMD3100 treatment attenuates PTOA. AMD3100 may provide a viable and expedient option for PTOA therapy given the drug's FDA approval and well-known safety profile.

Quantifying not only bone loss, but also soft tissue swelling, in a murine inflammatory arthritis model using micro-computed tomography

In rodent models of inflammatory arthritis, bone erosion has been non-invasively assessed by micro-computed tomography (micro-CT). However, non-invasive assessments of paw swelling (oedema) are still based on clinical grading by visual evaluation, or measurements by callipers, not always reliable for the tiny mouse paws. The aim of this work was to demonstrate a novel straightforward 3D micro-CT analysis protocol capable of quantifying not only joint bone erosion, but also soft tissue swelling, from the same scans, in a rodent inflammatory arthritis model. Balb/c mice were divided into two groups: collagen antibody-induced arthritis (CAIA) and CAIA treated with prednisolone, the latter reflecting an established treatment in human rheumatoid arthritis. Clinical paw scores were recorded. On day 10, front paws were assessed by micro-CT and histology. Micro-CT measurements included paw volume (bone and soft tissue together) and bone volume at the radiocarpal joint, and bone volume from the radiocarpal to the metacarpophalangeal joint. Micro-CT analysis revealed significantly lower paw volume (−36%, P < 0.01) and higher bone volume (+17%, P < 0.05) in prednisolone-treated CAIA mice compared with untreated CAIA mice. Paw volume and bone volume assessed by micro-CT correlated significantly with clinical and histological scores (|r| > 0.5, P < 0.01). Untreated CAIA mice showed significantly higher clinical scores, higher inflammation levels histologically, cartilage and bone degradation, and pannus formation, compared with treated mice (P < 0.01). The presented novel micro-CT analysis protocol enables 3D-quantification of paw swelling at the micrometre level, along with the typically assessed bone erosion, using the same images/scans, without altering the scanning procedure or using contrast agents.

Effect of methotrexate on collagen-induced arthritis assessed by micro-computed tomography and histopathological examination in female rats

We tested the hypothesis that micro-computed tomography (micro-CT) analysis provides a better quantitative readout of the therapeutic potential of methotrexate (MTX) for treating collagen-induced arthritis (CIA) in rats and compared to conventional histopathological examination. Rats were divided into three groups: Group 1 (G1) was treated with 0.9% saline, whereas groups 2 (G2) and 3 (G3) were boosted with type II collagen at days 0 and 7. Following the first collagen immunization, rats in G1 and G2 were treated with 0.9% saline and those in G3 were treated with 1.5 mg/kg MTX from day 14 to 28. All rats were sacrificed on day 28, at which point and all hind knee joints were analyzed by micro-CT and histopathological examination. Micro-CT analyses showed that bone volume and trabecular number were significantly decreased in G2 and G3 compared to G1 (p<0.01), as was percent bone volume (p<0.05 and p<0.01, respectively). However, bone surface/bone volume was significantly increased in G2 and G3 compared to G1 (p<0.05 and p<0.01, respectively). Trabecular separation was significantly increased in G3 compared to G1 (p<0.05). Histopathological examination showed that knee joints of rats in G2 and G3 showed severe joint destruction with inflammatory cell infiltration. However, cartilage destruction was slightly reduced in G3 compared to G2. Taken together, these results suggest that MTX treatment reduced cartilage destruction in rats with CIA, and micro-CT analyses made it possible to quantify arthritic bony lesion.

Alarmin S100A8/S100A9 as a biomarker for molecular imaging of local inflammatory activity

Inflammation has a key role in the pathogenesis of various human diseases. The early detection, localization and monitoring of inflammation are crucial for tailoring individual therapies. However, reliable biomarkers to detect local inflammatory activities and to predict disease outcome are still missing. Alarmins, which are locally released during cellular stress, are early amplifiers of inflammation. Here, using optical molecular imaging, we demonstrate that the alarmin S100A8/S100A9 serves as a sensitive local and systemic marker for the detection of even sub-clinical disease activity in inflammatory and immunological processes like irritative and allergic contact dermatitis. In a model of collagen-induced arthritis, we use S100A8/S100A9 imaging to predict the development of disease activity. Furthermore, S100A8/S100A9 can act as a very early and sensitive biomarker in experimental leishmaniasis for phagocyte activation linked to an effective Th1-response. In conclusion, the alarmin S100A8/S100A9 is a valuable and sensitive molecular target for novel imaging approaches to monitor clinically relevant inflammatory disorders on a molecular level.

Indian hedgehog in synovial fluid is a novel marker for early cartilage lesions in human knee joint

To determine whether there is a correlation between the concentration of Indian hedgehog (Ihh) in synovial fluid (SF) and the severity of cartilage damage in the human knee joints, the knee cartilages from patients were classified using the Outer-bridge scoring system and graded using the Modified Mankin score. Expression of Ihh in cartilage and SF samples were analyzed with immunohistochemistry (IHC), western blot, and enzyme-linked immunosorbent assay (ELISA). Furthermore, we detected and compared Ihh protein levels in rat and mice cartilages between normal control and surgery-induced osteoarthritis (OA) group by IHC and fluorescence molecular tomography in vivo respectively. Ihh expression was increased 5.2-fold in OA cartilage, 3.1-fold in relative normal OA cartilage, and 1.71-fold in OA SF compared to normal control samples. The concentrations of Ihh in cartilage and SF samples was significantly increased in early-stage OA samples when compared to normal samples (r = 0.556; p < 0.001); however, there were no significant differences between normal samples and late-stage OA samples. Up-regulation of Ihh protein was also an early event in the surgery-induced OA models. Increased Ihh is associated with the severity of OA cartilage damage. Elevated Ihh content in human knee joint synovial fluid correlates with early cartilage lesions.

Disrupting the Indian hedgehog signaling pathway in vivo attenuates surgically induced osteoarthritis progression in Col2a1-CreERT2; Ihhfl/fl mice

INTRODUCTION

Previous observations implicate Indian hedgehog (Ihh) signaling in osteoarthritis (OA) development because it regulates chondrocyte hypertrophy and matrix metallopeptidase 13 (MMP-13) expression. However, there is no direct genetic evidence for the role of Ihh in OA, because mice with cartilage or other tissue-specific deletion of the Ihh gene die shortly after birth. We evaluated the role of Ihh in vivo via a Cre-loxP-mediated approach to circumvent the early death caused by Ihh deficiency.

METHODS

To evaluate the role of Ihh in OA development, Ihh was specifically deleted in murine cartilage using an Ihh conditional deletion construct (Col2a1-CreER(T2); Ihh(fl/fl)). The extent of cartilage degradation and OA progression after Ihh deletion was assessed by histological analysis, immunohistochemistry, real-time PCR and in vivo fluorescence molecular tomography (FMT) 2 months after OA was induced by partial medial meniscectomy. The effect of Ihh signaling on cartilage was compared between Ihh-deleted mice and their control littermates.

RESULTS

Only mild OA changes were observed in Ihh-deleted mice, while control mice displayed significantly more cartilage damage. Typical OA markers such as type X collagen and MMP-13 were decreased in Ihh-deleted mice. In vivo FMT demonstrated decreased cathepsins and MMP activity in knee joints of animals with deletion of Ihh.

CONCLUSIONS

These findings support the protective role of Ihh deletion in surgically induced OA. Thus, our findings suggest the potential to develop new therapeutic strategies that can prevent and treat OA by inhibiting Ihh signaling in chondrocytes.

Continuous monitoring of arthritis in animal models using optical imaging modalities

Given the several difficulties associated with histology, including difficulty in continuous monitoring, this study aimed to investigate the feasibility of optical imaging modalities—cross-polarization color (CPC) imaging, erythema index (EI) imaging, and laser speckle contrast (LSC) imaging—for continuous evaluation and monitoring of arthritis in animal models. C57BL/6 mice, used for the evaluation of arthritis, were divided into three groups: arthritic mice group (AMG), positive control mice group (PCMG), and negative control mice group (NCMG). Complete Freund’s adjuvant, mineral oil, and saline were injected into the footpad for AMG, PCMG, and NCMG, respectively. LSC and CPC images were acquired from 0 through 144 h after injection for all groups. EI images were calculated from CPC images. Variations in feet area, EI, and speckle index for each mice group over time were calculated for quantitative evaluation of arthritis. Histological examinations were performed, and the results were found to be consistent with those from optical imaging analysis. Thus, optical imaging modalities may be successfully applied for continuous evaluation and monitoring of arthritis in animal models.

Optical tomographic imaging of near infrared imaging agents quantifies disease severity and immunomodulation of experimental autoimmune encephalomyelitis in vivo

Background

Experimental autoimmune encephalomyelitis (EAE) is an animal model that captures many of the hallmarks of human multiple sclerosis (MS), including blood–brain barrier (BBB) breakdown, inflammation, demyelination and axonal destruction. The standard clinical score measurement of disease severity and progression assesses functional changes in animal mobility; however, it does not offer information regarding the underlying pathophysiology of the disease in real time. The purpose of this study was to apply a novel optical imaging technique that offers the advantage of rapid imaging of relevant biomarkers in live animals.

Methods

Advances in non-invasive fluorescence molecular tomographic (FMT) imaging, in combination with a variety of biological imaging agents, offer a unique, sensitive and quantifiable approach to assessing disease biology in living animals. Using vascular (AngioSense 750EX) and protease-activatable cathepsin B (Cat B 680 FAST) near infrared (NIR) fluorescence imaging agents to detect BBB breakdown and inflammation, respectively, we quantified brain and spinal cord changes in mice with relapsing-remitting PLP_139-151-induced EAE and in response to tolerogenic therapy.

Results

FMT imaging and analysis techniques were carefully characterized and non-invasive imaging results corroborated by both ex vivo tissue imaging and comparison to clinical score results and histopathological analysis of CNS tissue. FMT imaging showed clear differences between control and diseased mice, and immune tolerance induction by antigen-coupled PLGA nanoparticles effectively blocked both disease induction and accumulation of imaging agents in the brain and spinal cord.

Conclusions

Cat B 680 FAST and AngioSense 750EX offered the combination best able to detect disease in both the brain and spinal cord, as well as the downregulation of disease by antigen-specific tolerance. Non-invasive optical tomographic imaging thus offers a unique approach to monitoring neuroinflammatory disease and therapeutic intervention in living mice with EAE.

Synovitis in patients with early inflammatory arthritis monitored with quantitative analysis of dynamic contrast-enhanced optical imaging and MR imaging

PURPOSE

To evaluate quantitative perfusion measurements of dynamic indocyanine green (ICG)-enhanced optical imaging for monitoring synovitis in the hands of patients with inflammatory arthritis compared with dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging and clinical outcome.

MATERIALS AND METHODS

This study was approved by the ethics committee at the institution. Individual joints (n = 840) in the hands and wrists of 28 patients (14 women; mean age, 53.3 years) with inflammatory arthritis were examined at three different time points: before start of therapy and 12 and 24 weeks after start of therapy or therapy escalation. Treatment response was assessed by using clinical measures (simple disease activity index [SDAI]), ICG-enhanced optical imaging, and DCE MR imaging. Dynamic images were obtained for optical imaging and DCE MR imaging. The rate of early enhancement (REE) of the perfusion curves of each joint was calculated by using in-house developed software. Correlation coefficients were estimated to evaluate the associations of changes of imaging parameters and SDAI change.

RESULTS

Quantitative perfusion measurements with optical imaging and MR imaging correctly identified patients who responded (n = 18) and did not respond to therapy (n = 10), as determined by SDAI. The difference of REE after 24 weeks of treatment compared with baseline in responders was significantly reduced in optical imaging and MR imaging (optical imaging: mean, -21.5%; MR imaging: mean, -41.0%; P < .001 for both), while in nonresponders it was increased (optical imaging: mean, 10.8%; P = .075; MR imaging: mean, 8.7%; P = .03). The REE of optical imaging significantly correlated with MR imaging (ρ = 0.80; P < .001) and SDAI (ρ = 0.61; P < .001).

CONCLUSION

Quantitative analysis of contrast-enhanced optical imaging allows for potential therapeutic monitoring of synovitis in patients with inflammatory arthritis.

Detection of DSS-induced gastrointestinal mucositis in mice by non-invasive optical near-infrared (NIR) imaging of cathepsin activity

Approximately 1.4 million people of the US population suffer from Inflammatory Bowel Disease (IBD) of which the most common conditions are ulcerative colitis (UC) and Crohn disease (CD). Colonoscopy and small bowel follow through are considered the current gold standard in diagnosing IBD. However, improved imaging and increased diagnostic sensitivity could be beneficial. Optical molecular imaging has the potential to become a powerful and practical tool for early detection, image-guided biopsy, and surgery in diagnosing and treating patients with IBD. Here we used a well characterized chemical model to initiate experimental IBD in mice by feeding with dextran sulfate sodium (DSS) containing drinking water in an attempt to investigate the utility of non-invasive infrared (NIR) optical imaging in the detection gastrointestinal (GI) injury. We employed a "smart probe" (ProSense680) cleaved and fluorescently activated in the NIR-spectrum by various forms of secreted cathepsins. This probe has previously been shown to serve as a biomarker for the homing of inflammatory cells to injury. Our investigation suggests that NIR optical imaging can detect cathepsin-dependent probe cleavage non-invasively in animals with DSS-induced IBD. Increased tissue probe-retention and fluorescence was associated with increased infiltration of inflammatory cells, epithelial atrophy and sterilization of the mucosa. Furthermore, using NIR-imaging ex vivo we were able to document regional "hot spots" of inflammatory damage to the large intestine suggesting this method potentially could be coupled with colonoscopy investigation to aid in the sampling and the diagnostics of IBD.

Evaluation of a candidate anti-arthritic drug using the mouse collagen antibody induced arthritis model and clinically relevant biomarkers

The most rigorous scenario for testing a candidate rheumatoid arthritis therapeutic would be to use clinically relevant biomarkers and readouts to monitor disease development in an animal model that has a mechanism of disease that reflects the human condition. Treatment should begin when the full spectrum of arthritic processes, including bone damage, is present. We have tried to take this approach to evaluate a novel EP4 receptor antagonist (ER-886046) for its anti-arthritic potential. This work aimed not only to test a potential drug, but to also demonstrate a strategy for performing a more clinically relevant evaluation of future candidate arthritis treatments. A variety of biomarkers including: radiographic evaluation, clinical scoring, histology analysis, F4/80 macrophage immunohistochemistry, luminol bioluminescent imaging and (99m)Tc-MDP-SPECT imaging were evaluated as disease readouts in the mouse anti-collagen antibody induced arthritis model (CAIA). CAIA mice were treated either prophylactically or therapeutically with ER-886046 and the compound's efficacy was probed using the various biomarkers and compared to the reference drugs prednisolone and celecoxib. The various biomarkers effectively measured different aspects of arthritis pathology and consistently demonstrated the efficacy of ER-886046. The compound was found to be effective even when dosed therapeutically after bone damaging processes had initiated. The results presented herein demonstrate how biomarkers and a clinically relevant experimental design can be used to evaluate a candidate therapeutic. Utilization of clinically relevant biomarkers may provide a means for more translatable pre-clinical testing of candidate therapeutics and may provide information on their mechanism of action.

Molecular imaging of gastric neoplasia with near-infrared fluorescent activatable probes

Gastric cancer is the second leading cause of cancer mortality worldwide and is projected to rise to tenth in all-cause mortality in the near term. Early detection requires improved sensitivity and specificity of endoscopic imaging with novel methods. The objective of this study was to evaluate the utility of activatable molecular probes for the detection of gastric cancer both in vivo and ex vivo in a preclinical model. Smad4⁺/⁻ mice, which develop spontaneous gastric neoplasia, were compared to normal wild-type controls. Cathepsin-activatable and matrix metalloproteinase (MMP)-activatable molecular probes were injected 24 hours and 6 hours before imaging, respectively. In vivo imaging was performed using quantitative tomographic near-infrared fluorescence (NIRF) imaging. For validation, ex vivo imaging and histologic examination were performed. Molecular imaging in vivo of Smad4⁺/⁻ gastric cancer murine models revealed intense activation of both cathepsin B and MMP probes. Ex vivo imaging and histology confirmed that the detected neoplasms were adenocarcinomas and hyperplastic lesions. This study provides proof of principle that the cathepsin- and MMP-activatable molecular probes are activated in the Smad4⁺/⁻ murine model of spontaneous gastric adenocarcinoma and can be imaged by both in vivo and ex vivo NIRF methods. The cathepsin probe also detects hyperplastic lesions.

Characterization of human osteoarthritic cartilage using optical and magnetic resonance imaging

Purpose

Osteoarthritis (OA) is a degenerative disease starting with key molecular events that ultimately lead to the breakdown of the cartilage. The purpose of this study is to use two imaging methods that are sensitive to molecular and macromolecular changes in OA to better characterize the disease process in human osteoarthritic cartilage.

Procedures

Human femoral condyles were collected from patients diagnosed with severe OA during total knee replacement surgeries. T_1ρ and T₂ magnetic resonance measurements were obtained using a 3-Tesla whole body scanner to assess macromolecular changes in the damaged cartilage matrix. Optical imaging was performed on specimens treated with MMPSense 680 to assess the matrix metalloproteinase (MMP) activity. A linear regression model was used to assess the correlation of MMP optical data with T_1ρ magnetic resonance (MR) measurements. Slices from a representative specimen were removed from regions with high and low optical signals for subsequent histological analysis.

Results

All specimens exhibit high T_1ρ and T₂ measurements in the range of 48–75 ms and 36–69 ms, respectively. They also show intense photon signals (0.376 to 7.89 × 10⁻⁴ cm²) from the activated MMPSense 680 probe, indicative of high MMP activity. The analysis of variance test of the regression model indicates a positive correlation between the MMP optical signal and T_1ρ measurements (R² = 0.8936, P = 0.0044). Histological data also confirmed that regions with high MMP optical signal and intense T_1ρ relaxation exhibit severe clefting, abnormal tidemarks, and irregular cellularity.

Conclusions

The high T_1ρ and T₂ measurements suggest that there is a severe loss of proteoglycans with high water mobility in the damaged cartilage. The intense optical signals found in these specimens indicate the presence of active MMPs, and the positive correlation with T_1ρ measurements implicates MMP’s involvement in OA progression, characterized by a severe loss of proteoglycans in the cartilage matrix. The bimodal approach using optical and MR imaging may provide key molecular and macromolecular information of the disease pathway, offering insights toward the development of new tools for the early detection, treatment, and/or prevention of OA.

A fluorogenic near-infrared imaging agent for quantifying plasma and local tissue renin activity in vivo and ex vivo

The renin-angiotensin system (RAS) is well studied for its regulation of blood pressure and fluid homeostasis, as well as for increased activity associated with a variety of diseases and conditions, including cardiovascular disease, diabetes, and kidney disease. The enzyme renin cleaves angiotensinogen to form angiotensin I (ANG I), which is further cleaved by angiotensin-converting enzyme to produce ANG II. Although ANG II is the main effector molecule of the RAS, renin is the rate-limiting enzyme, thus playing a pivotal role in regulating RAS activity in hypertension and organ injury processes. Our objective was to develop a near-infrared fluorescent (NIRF) renin-imaging agent for noninvasive in vivo detection of renin activity as a measure of tissue RAS and in vitro plasma renin activity. We synthesized a renin-activatable agent, ReninSense 680 FAST (ReninSense), using a NIRF-quenched substrate derived from angiotensinogen that is cleaved specifically by purified mouse and rat renin enzymes to generate a fluorescent signal. This agent was assessed in vitro, in vivo, and ex vivo to detect and quantify increases in plasma and kidney renin activity in sodium-sensitive inbred C57BL/6 mice maintained on a low dietary sodium and diuretic regimen. Noninvasive in vivo fluorescence molecular tomographic imaging of the ReninSense signal in the kidney detected increased renin activity in the kidneys of hyperreninemic C57BL/6 mice. The agent also effectively detected renin activity in ex vivo kidneys, kidney tissue sections, and plasma samples. This approach could provide a new tool for assessing disorders linked to altered tissue and plasma renin activity and to monitor the efficacy of therapeutic treatments.

Early diagnosis of arthritis in mice with collagen-induced arthritis, using a fluorogenic matrix metalloproteinase 3-specific polymeric probe

OBJECTIVE

Early treatment based on an early diagnosis of rheumatoid arthritis (RA) could halt progression of the disease, but early diagnosis is often difficult. Matrix metalloproteinase 3 (MMP-3) is thought to be particularly important in the pathogenesis of RA. The aim of this study was to investigate whether an MMP-3-specific polymeric probe could be used for early diagnosis and for visualizing the progression of arthritis, using a near-infrared fluorescence (NIRF) imaging system.

METHODS

The MMP-3-specific polymeric probe was developed by conjugating NIRF dye, MMP substrate peptide, and dark quencher to self-assembled chitosan nanoparticles. One hour after intravenous administration of the probe, fluorescent images of mice with collagen-induced arthritis at different stages of disease development were obtained. The correlation between the fluorescence recovered in in vivo imaging when using an MMP-3-specific polymeric probe and up-regulated MMP-3 activity in the joint tissues was evaluated by Western blotting and immunohistochemical staining. Histologic analysis and micro-computed tomography (micro-CT) were also used to assess arthritis progression.

RESULTS

A significantly higher NIRF signal was recovered from arthritic joints compared with normal joints at 14 days after the first immunization, before any erythema or swelling could be observed with the naked eye or any erosion was detected by histologic analysis or micro-CT. The results of immunohistochemical analysis and Western blotting confirmed that the fluorescence recovered in the in vivo imaging was related to up-regulated MMP-3 activity in the joint tissues.

CONCLUSION

An MMP-3-specific polymeric probe provided clear early diagnosis of arthritis and visualization of arthritis progression using an NIRF imaging system. This approach could be used for early diagnosis and for monitoring drug and surgical therapies in individual cases.

Quantitative whole body biodistribution of fluorescent-labeled agents by non-invasive tomographic imaging

When small molecules or proteins are injected into live animals, their physical and chemical properties will significantly affect pharmacokinetics, tissue penetration, and the ultimate routes of metabolism and clearance. Fluorescence molecular tomography (FMT) offers the ability to non-invasively image and quantify temporal changes in fluorescence throughout the major organ systems of living animals, in a manner analogous to traditional approaches with radiolabeled agents. This approach is best used with biotherapeutics (therapeutic antibodies, or other large proteins) or large-scaffold drug-delivery vectors, that are minimally affected by low-level fluorophore conjugation. Application to small molecule drugs should take into account the significant impact of fluorophore labeling on size and physicochemical properties, however, the presents studies show that this technique is readily applied to small molecule agents developed for far-red (FR) or near infrared (NIR) imaging. Quantification by non-invasive FMT correlated well with both fluorescence from tissue homogenates as well as with planar (2D) fluorescence reflectance imaging of excised intact organs (r²  =  0.996 and 0.969, respectively). Dynamic FMT imaging (multiple times from 0 to 24 h) performed in live mice after the injection of four different FR/NIR-labeled agents, including immunoglobulin, 20-50 nm nanoparticles, a large vascular imaging agent, and a small molecule integrin antagonist, showed clear differences in the percentage of injected dose per gram of tissue (%ID/g) in liver, kidney, and bladder signal. Nanoparticles and IgG1 favored liver over kidney signal, the small molecule integrin-binding agent favored rapid kidney and bladder clearance, and the vascular agent, showed both liver and kidney clearance. Further assessment of the volume of distribution of these agents by fluorescent volume added information regarding their biodistribution and highlighted the relatively poor extravasation into tissue by IgG1. These studies demonstrate the ability of quantitative FMT imaging of FR/NIR agents to non-invasively visualize and quantify the biodistribution of different agents over time.

Optical imaging of rheumatoid arthritis

Optical Imaging (OI) for rheumatoid arthritis is a novel imaging modality. With the high number of people affected by this disease, especially in western countries, the availability of OI as an early diagnostic imaging method is clinically highly relevant. In this article we describe the current techniques of OI and discuss potential future applications of this promising technology. Overall, we demonstrate that OI is a fast, inexpensive, noninvasive, nonionizing and accurate imaging modality. Furthermore, OI is a clinically applicable tool allowing for the early detection of inflammation and potentially facilitating the monitoring of therapy.