Clinical Molecular Imaging of Pulmonary CXCR4 Expression to Predict Outcome of Pirfenidone Treatment in Idiopathic Pulmonary Fibrosis

Chemokine receptor PET imaging: Bridging molecular insights with clinical applications

Chemokine receptors are important components of cellular signaling and play a critical role in directing leukocytes during inflammatory reactions. Their importance extends to numerous pathological processes, including tumor differentiation, angiogenesis, metastasis, and associations with multiple inflammatory disorders. The necessity to monitor the in vivo interactions of cellular chemokine receptors has been driven the recent development of novel positron emission tomography (PET) imaging agents. This imaging modality provides non-invasive localization and quantitation of these receptors that cannot be provided through blood or tissue-based assays. Herein, we provide a review of PET imaging of the chemokine receptors that have been imaged to date, namely CXCR3, CXCR4, CCR2, CCR5, and CMKLR1. The quantification of these receptors can aid in understanding various diseases, including cancer, atherosclerosis, idiopathic pulmonary fibrosis, and acute respiratory distress syndrome. The development of specific radiotracers targeting these receptors will be discussed, including promising results for disease diagnosis and management. However, challenges persist in fully translating these imaging advancements into practical therapeutic applications. Given the success of CXCR4 PET imaging to date, future research should focus on clinical translation of these approaches to understand their role in the management of a wide variety of diseases.

Noninvasive assessment of the lung inflammation-fibrosis axis by targeted imaging of CMKLR1

Precision management of fibrotic lung diseases is challenging due to their diverse clinical trajectories and lack of reliable biomarkers for risk stratification and therapeutic monitoring. Here, we validated the accuracy of CMKLR1 as an imaging biomarker of the lung inflammation-fibrosis axis. By analyzing single-cell RNA sequencing datasets, we demonstrated CMKLR1 expression as a transient signature of monocyte-derived macrophages (MDMφ) enriched in patients with idiopathic pulmonary fibrosis (IPF). Consistently, we identified MDMφ as the major driver of the uptake of CMKLR1-targeting peptides in a murine model of bleomycin-induced lung fibrosis. Furthermore, CMKLR1-targeted positron emission tomography in the murine model enabled quantification and spatial mapping of inflamed lung regions infiltrated by CMKLR1-expressing macrophages and emerged as a robust predictor of subsequent lung fibrosis. Last, high CMKLR1 expression by bronchoalveolar lavage cells identified an inflammatory endotype of IPF with poor survival. Our investigation supports the potential of CMKLR1 as an imaging biomarker for endotyping and risk stratification of fibrotic lung diseases.

Early, non-invasive detection of radiation-induced lung injury using PET/CT by targeting CXCR4

PURPOSE

Radiation-induced lung injury (RILI) is a severe side effect of radiotherapy (RT) for thoracic malignancies and we currently lack established methods for the early detection of RILI. In this study, we synthesized a new tracer, [18F]AlF-NOTA-QHY-04, targeting C-X-C-chemokine-receptor-type-4 (CXCR4) and investigated its feasibility to detect RILI.

METHODS

An RILI rat model was constructed and scanned with [18F]AlF-NOTA-QHY-04 PET/CT and [18F]FDG PET/CT periodically after RT. Dynamic, blocking, autoradiography, and histopathological studies were performed on the day of peak uptake. Fourteen patients with radiation pneumonia, developed during or after thoracic RT, were subjected to PET scan using [18F]AlF-NOTA-QHY-04.

RESULTS

The yield of [18F]AlF-NOTA-QHY-04 was 28.5-43.2%, and the specific activity was 27-33 GBq/μmol. [18F]AlF-NOTA-QHY-04 was mainly excreted through the kidney. Significant increased [18F]AlF-NOTA-QHY-04 uptake in the irradiated lung compared with that in the normal lung in the RILI model was observed on day 6 post-RT and peaked on day 14 post-RT, whereas no apparent uptake of [18F]FDG was shown on days 7 and 15 post-RT. MicroCT imaging did not show pneumonia until 42 days post-RT. Significant intense [18F]AlF-NOTA-QHY-04 uptake was confirmed by autoradiography. Immunofluorescence staining demonstrated expression of CXCR4 was significantly increased in the irradiated lung tissue, which correlated with results obtained from hematoxylin-eosin and Masson's trichrome staining. In 14 patients with radiation pneumonia, maximum standardized uptake values (SUVmax) were significantly higher in the irradiated lung compared with those in the normal lung. SUVmax of patients with grade 2 RILI was significantly higher than that of patients with grade 1 RILI.

CONCLUSION

This study indicated that [18F]AlF-NOTA-QHY-04 PET/CT imaging can detect RILI non-invasively and earlier than [18F]FDG PET/CT in a rat model. Clinical studies verified its feasibility, suggesting the clinical potential of [18F]AlF-NOTA-QHY-04 as a PET/CT tracer for early monitoring of RILI.

Advances in PET Imaging of the CXCR4 Receptor: [68Ga]Ga-PentixaFor

[68Ga]Ga-PentixaFor, a PET agent targeting CXCR4 is emerging as a versatile radiotracer with promising applications in oncology, cardiology and inflammatory disease. Preclinical work in various cancer cell lines have demonstrated high specificity and selectivity. In human investigations of several tumors, the most promising applications may be in multiple myeloma, certain lymphomas and myeloproliferative neoplasms. In the nononcologic setting, [68Ga]Ga-PentixaFor could greatly improve detection for primary aldosteronism and other endocrine abnormalities. Similarly, atherosclerotic disease and other inflammatory conditions could also benefit from enhanced identification by CXCR4 targeting. Rapidly cleared from the body with a favorable imaging and radiation dosimetry profile that has been already studied in over 1000 patients, [68Ga]Ga-PentixaFor is a worthy agent for further clinical exploration with potential for theranostic applications in hematologic malignancies.

Homeostatic chemokines as putative therapeutic targets in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal chronic interstitial lung disease (ILD) that affects lung mechanical functions and gas exchange. IPF is caused by increased fibroblast activity and collagen deposition that compromise the alveolar-capillary barrier. Identifying an effective therapy for IPF remains a clinical challenge. Chemokines are key proteins in cell communication that have functions in immunity as well as in tissue homeostasis, damage, and repair. Chemokine receptor signaling induces the activation and proliferation of lung-resident cells, including alveolar macrophages (AMs) and fibroblasts. AMs are an important source of chemokines and cytokines during IPF. We highlight the complexity of this system and, based on insights from genetic and transcriptomic studies, propose a new role for homeostatic chemokine imbalance in IPF, with implications for putative therapeutic targets.

99mTc-Labeled FAPI SPECT Imaging in Idiopathic Pulmonary Fibrosis: Preliminary Results

AIM

Idiopathic pulmonary fibrosis (IPF) is associated with a poor prognosis, presenting the most aggressive form of interstitial lung diseases (ILDs). Activated fibroblasts are crucial for pathological processes. Fibroblast activation protein (FAP) inhibitor (FAPI) tracers would be promising imaging agents for these diseases. The purpose of this study was to evaluate a 99mTc-labeled FAPI tracer, 99mTc-HFAPI imaging in IPF patients.

METHODS

Eleven IPF patients (nine males and two females; age range 55-75 year) were included in this pilot study. 99mTc-HFAPI serial whole-body scintigraphy at 5 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, and 6 h was acquired for dynamic biodistribution and dosimetry estimation in seven representative patients. SPECT/CT tomography fusion imaging of the chest region was performed in all patients at 4 h post-injection, which was considered as the optimal acquisition time. Dosimetry was calculated using OLINDA/EXM software (version 2.0; HERMES Medical Solutions). The quantified or semi-quantified standardized uptake values (SUVs) and lesion-to-background ratios (LBRs) of affected lung parenchyma were also calculated. The high-resolution CT (HRCT) stage was determined with visual evaluation, and the total HRCT score of each patient was measured using a weighting factor formula. Pulmonary function tests (PFTs) were recorded as well. Then, the relationships between the 99mTc-HFAPI results, disease extent on HRCT, and PFT results were investigated.

RESULTS

Normal physiological uptake of 99mTc-HFAPI was observed mainly in the liver, intestinal tract, pancreas, gallbladder, and to a lesser extent in the spleen, kidneys, and thyroid, with no apparent retention in the blood circulation at the late time point. The mean injected activity of 99mTc-HFAPI was 813.4 MBq (range 695.6-888.0 MBq). No subjective side effects were noticed. The average whole-body effective dose was 0.0041 mSv/MBq per patient. IPF patients exhibited elevated pulmonary 99mTc-HFAPI uptake in abnormal lung regions, which was correlated with fibrotic regions on HRCT. Among different HRCT stage groups, both SUVmax and LBR showed significant differences (p < 0.001). The higher HRCT stage demonstrated significantly higher SUVmax and LBR. A linear correlation between 99mTc-HFAPI uptake and total HRCT score was observed for SUVmax (r = 0.7839, F = 54.41, p = 0.0094) and LBR (r = 0.7402, F = 56.33, p = 0.0092). 99mTc-HFAPI uptake also had moderate correlations with PFT results.

CONCLUSIONS

Our preliminary data show that the 99mTc-HFAPI SPECT imaging is a promising new imaging modality in IPF patients. Investigations of its clinical value in monitoring disease progression and treatment response are needed in the future.

Optimization of an Allysine-Targeted PET Probe for Quantifying Fibrogenesis in a Mouse Model of Pulmonary Fibrosis

PURPOSE

Idiopathic pulmonary fibrosis (IPF) is a destructive lung disease with a poor prognosis, an unpredictable clinical course, and inadequate therapies. There are currently no measures of disease activity to guide clinicians making treatment decisions. The aim of this study was to develop a PET probe to identify lung fibrogenesis using a pre-clinical model of pulmonary fibrosis, with potential for translation into clinical use to predict disease progression and inform treatment decisions.

METHODS

Eight novel allysine-targeting chelators, PIF-1, PIF-2, …, PIF-8, with different aldehyde-reactive moieties were designed, synthesized, and radiolabeled with gallium-68 or copper-64. PET probe performance was assessed in C57BL/6J male mice 2 weeks after intratracheal bleomycin challenge and in naïve mice by dynamic PET/MR imaging and with biodistribution at 90 min post injection. Lung hydroxyproline and allysine were quantified ex vivo and histological staining for fibrosis and aldehyde was performed.

RESULTS

In vivo screening of probes identified 68GaPIF-3 and 68GaPIF-7 as probes with high uptake in injured lung, high uptake in injured lung versus normal lung, and high uptake in injured lung versus adjacent liver and heart tissue. A crossover, intra-animal PET/MR imaging study of 68GaPIF-3 and 68GaPIF-7 confirmed 68GaPIF-7 as the superior probe. Specificity for fibrogenesis was confirmed in a crossover, intra-animal PET/MR imaging study with 68GaPIF-7 and a non-binding control compound, 68GaPIF-Ctrl. Substituting copper-64 for gallium-68 did not affect lung uptake or specificity indicating that either isotope could be used.

CONCLUSION

A series of allysine-reactive PET probes with variations in the aldehyde-reactive moiety were evaluated in a pre-clinical model of lung fibrosis. The hydrazine-bearing probe, 68GaPIF-7, exhibited the highest uptake in fibrogenic lung, low uptake in surrounding liver or heart tissue, and low lung uptake in healthy mice and should be considered for further clinical translation.

Transcriptomic profiling of mare endometrium at different stages of endometrosis

In the current study, transcriptome profiles of mare endometrium, classified into categories I, IIA, and IIB according to Kenney and Doig, were compared using RNA sequencing, analyzed, and functionally annotated using in silico analysis. In the mild stage (IIA) of endometrosis compared to category I endometrium, differentially expressed genes (DEGs) were annotated to inflammation, abnormal metabolism, wound healing, and quantity of connective tissue. In the moderate stage (IIB) of endometrosis compared to category I endometrium, DEGs were annotated to inflammation, fibrosis, cellular homeostasis, mitochondrial dysfunction, and pregnancy disorders. Ingenuity pathway analysis (IPA) identified cytokines such as transforming growth factor (TGF)-β1, interleukin (IL)-4, IL-13, and IL-17 as upstream regulators of DEGs associated with cellular homeostasis, metabolism, and fibrosis signaling pathways. In vitro studies showed the effect of these cytokines on DEGs such as ADAMTS1, -4, -5, -9, and HK2 in endometrial fibroblasts at different stages of endometrosis. The effect of cytokines on ADAMTS members' gene transcription in fibroblasts differs according to the severity of endometrosis. The identified transcriptomic changes associated with endometrosis suggest that inflammation and metabolic changes are features of mild and moderate stages of endometrosis. The changes of ADAMTS-1, -4, -5, -9, in fibrotic endometrium as well as in endometrial fibroblast in response to TGF-β1, IL-4, IL-13, and IL-17 suggest the important role of these factors in the development of endometrosis.

Radiolabeled GPVI-Fc for PET Imaging of Multiple Extracellular Matrix Fibers: A New Look into Pulmonary Fibrosis Progression

Invariably fatal and with a particularly fast progression, pulmonary fibrosis (PF) is currently devoid of curative treatment options. Routine clinical diagnosis relies on breathing tests and visualizing the changes in lung structure by CT, but anatomic information is often not sufficient to identify early signs of progressive PF. For more efficient diagnosis, additional imaging techniques were investigated in combination with CT, such as 18F-FDG PET, although with limited success because of lack of disease specificity. Therefore, novel molecular targets enabling specific diagnosis are investigated, in particular for molecular imaging techniques. Methods: In this study, we used a 64Cu-radiolabeled platelet glycoprotein VI fusion protein (64Cu-GPVI-Fc) targeting extracellular matrix (ECM) fibers as a PET tracer to observe longitudinal ECM remodeling in a bleomycin-induced PF mouse model. Results: 64Cu-GPVI-Fc showed significant uptake in fibrotic lungs, matching histology results. Contrary to 18F-FDG PET measurements, 64Cu-GPVI-Fc uptake was linked entirely to the fibrotic activity of tissue and not was susceptible to inflammation. Conclusion: Our study highlights 64Cu-GPVI-Fc as a specific tracer for ECM remodeling in PF, with clear therapy-monitoring and clinical translation potential.

[89Zr]-immuno-PET prediction of response to rituximab treatment in patients with therapy refractory interstitial pneumonitis: a phase 2 trial

INTRODUCTION

Immune-mediated interstitial pneumonitis may be treated with anti-CD20 therapy after failure of conventional therapies. However, clinical response is variable. It was hypothesized that autoreactive CD20-positive cells may play an important role in this variability. This prospective study aims to elucidate if imaging of CD20-positive cells in the lungs allows prediction of the response to anti-CD20 treatment.

METHODS

Twenty-one patients with immune-mediated interstitial lung disease (ILD) with deteriorated pulmonary function received a dose of 1000 mg rituximab on day 1 and day 14 spiked with a tracer dose of radiolabeled [89Zr]-rituximab. PET/CT was performed on days 3 and 6. Standardized uptake values (SUV) were calculated as a measure for pulmonary CD20 expression. Based on pulmonary function tests (PFT), forced vital capacity (FVC), and diffusing capacity for carbon monoxide (DLCO), prior to and 6 months after treatment, patients were classified as responder (stable disease or improvement) or non-responder.

RESULTS

Fifteen patients (71%) were classified as responder. Pulmonary [89Zr]-rituximab PET SUVmean was significantly correlated with the change in FVC and DLCO (K = 0.49 and 0.56, respectively) when using target-to-background ratios, but not when using SUVmean alone. [89Zr]-rituximab SUVmean was significantly higher in responders than in non-responders (0.35 SD 0.09 vs. 0.23 SD 0.06; P = 0.02).

CONCLUSION

Rituximab treatment was effective in the majority of patients. As a higher pulmonary uptake of [89Zr]-rituximab correlated with improvement of PFT and treatment outcome, [89Zr]-rituximab PET imaging may serve as a potential predictive biomarker for anti-CD20 therapy.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT02251964.

Novel tracers for molecular imaging of interstitial lung disease: A state of the art review

Interstitial lung disease is an overarching term for a wide range of disorders characterized by inflammation and/or fibrosis in the lungs. Most prevalent forms, among others, include idiopathic pulmonary fibrosis (IPF) and connective tissue disease associated interstitial lung disease (CTD-ILD). Currently, only disease modifying treatment options are available for IPF and progressive fibrotic CTD-ILD, leading to reduction or stabilization in the rate of lung function decline at best. Management of these patients would greatly advance if we identify new strategies to improve (1) early detection of ILD, (2) predicting ILD progression, (3) predicting response to therapy and (4) understanding pathophysiology. Over the last years, positron emission tomography (PET) and single photon emission computed tomography (SPECT) have emerged as promising molecular imaging techniques to improve ILD management. Both are non-invasive diagnostic tools to assess molecular characteristics of an individual patient with the potential to apply personalized treatment. In this review, we encompass the currently available pre-clinical and clinical studies on molecular imaging with PET and SPECT in IPF and CTD-ILD. We provide recommendations for potential future clinical applications of these tracers and directions for future research.

C-X-C-Chemokine-Receptor-Type-4 Inhibitor AMD3100 Attenuates Pulmonary Inflammation and Fibrosis in Silicotic Mice

Background

Silicosis is a severe pulmonary disease caused by inhaling dust containing crystalline silica. The progression of silicosis to pulmonary fibrosis is usually unavoidable. Recent studies have revealed positivity for the overexpression of C-X-C chemokine receptor type 4 (CXCR4) in pulmonary fibrosis and shown that the CXCR4 inhibitor AMD3100 attenuated pulmonary fibrosis after bleomycin challenge and paraquat exposure. However, it is unclear whether AMD3100 reduces crystalline silica-induced pulmonary fibrosis.

Methods

C57BL/6 male mice were instilled intranasally with a single dose of crystalline silica (12 mg/60 μL) to establish an acute silicosis mouse model. Twelve hours later, the mice were injected intraperitoneally with 5 mg/kg AMD3100 or control solution. Then, the mice were weighed daily and sacrificed on day 7, 14, or 28 to collect lung tissue and peripheral blood. Western blotting was also applied to determine the level of CXCR4, while different histological techniques were used to assess pulmonary inflammation and fibrosis. In addition, the level of B cells in peripheral blood was measured by flow cytometry.

Results

CXCR4 and its ligand CXCL12 were upregulated in the lung tissues of crystalline silica-exposed mice. Blocking CXCR4 with AMD3100 suppressed the upregulation of CXCR4/CXCL12, reduced the severity of lung injury, and prevented weight loss. It also inhibited neutrophil infiltration at inflammatory sites and neutrophil extracellular trap formation, as well as reduced B-lymphocyte aggregates in the lung. Additionally, it decreased the recruitment of circulating fibrocytes (CD45⁺collagen I⁺CXCR4⁺) to the lung and the deposition of collagen I and α-smooth muscle actin in lung tissue. AMD3100 also increased the level of B cells in peripheral blood, preventing circulating B cells from migrating to the injured lungs.

Conclusion

Blocking CXCR4 with AMD3100 delays pulmonary inflammation and fibrosis in a silicosis mouse model, suggesting the potential of AMD3100 as a drug for treating silicosis.

[68Ga]Ga-Pentixafor and Sodium [18F]Fluoride PET Can Non-Invasively Identify and Monitor the Dynamics of Orthodontic Tooth Movement in Mouse Model

The cellular and molecular mechanisms of orthodontic tooth movement (OTM) are not yet fully understood, partly due to the lack of dynamical datasets within the same subject. Inflammation and calcification are two main processes during OTM. Given the high sensitivity and specificity of [⁶⁸Ga]Ga-Pentixafor and Sodium [¹⁸F]Fluoride (Na[¹⁸F]F) for inflammation and calcification, respectively, the aim of this study is to assess their ability to identify and monitor the dynamics of OTM in an established mouse model. To monitor the processes during OTM in real time, animals were scanned using a small animal PET/CT during week 1, 3, and 5 post-implantation, with [⁶⁸Ga]Ga-Pentixafor and Na[¹⁸F]F. Both tracers showed an increased uptake in the region of interest compared to the control. For [⁶⁸Ga]Ga-Pentixafor, an increased uptake was observed within the 5-week trial, suggesting the continuous presence of inflammatory markers. Na[¹⁸F]F showed an increased uptake during the trial, indicating an intensification of bone remodelling. Interim and end-of-experiment histological assessments visualised increased amounts of chemokine receptor CXCR4 and TRAP-positive cells in the periodontal ligament on the compression side. This approach establishes the first in vivo model for periodontal remodelling during OTM, which efficiently detects and monitors the intricate dynamics of periodontal ligament.

Positron Emission Tomography to Improve Assessment of Interstitial Lung Disease in Patients With Systemic Sclerosis Eligible for Autologous Stem Cell Transplantation

Positron emission tomography (PET) is a promising technique to improve the assessment of systemic sclerosis associated interstitial lung disease (SSc-ILD). This technique could be of particular value in patients with severe diffuse cutaneous SSc (dcSSc) that are possibly eligible for autologous hematopoietic stem cell transplantation (aHSCT). aHSCT is a potentially effective therapy for patients with severe dcSSc and ILD, leading to stabilization or improvement of lung function. However, there is a high need to improve patient selection, which includes (1) the selection of patients with rapidly progressive ILD for early rather than last-resort aHSCT (2) the prediction of treatment response on ILD and (3) the understanding of the mechanism(s) of action of aHSCT in the lungs. As previous studies with 18F-FDG PET in SSc-ILD and other forms of ILD have demonstrated its potential value in predicting disease progression and reactivity to anti-inflammatory treatment, we discuss the potential benefit of using this technique in patients with early severe dcSSc and ILD in the context of aHSCT. In addition, we discuss the potential value of other PET tracers in the assessment of ILD and understanding the mechanisms of action of aHSCT in the lung. Finally, we provide several suggestions for future research.

Challenges for Clinical Drug Development in Pulmonary Fibrosis

Pulmonary fibrosis is a pathologic process associated with scarring of the lung interstitium. Interstitial lung diseases (ILDs) encompass a large and heterogenous group of disorders, a number of which are characterized by progressive pulmonary fibrosis that leads to respiratory failure and death. Idiopathic pulmonary fibrosis (IPF) has been described as an archetype of progressive fibrosing ILD, and the development of pirfenidone and nintedanib has been a major breakthrough in the treatment of patients with this deadly disease. Both drugs principally target scar-forming fibroblasts and have been shown to significantly slow down the accelerated decline of lung function by approximately 50%. In addition, nintedanib has been approved for patients with other progressive fibrosing ILDs and systemic sclerosis-associated ILD. However, there is still no cure for pulmonary fibrosis and no meaningful improvement of symptoms or quality of life has been shown. Advancement in research, such as the advent of single cell sequencing technology, has identified additional pathologic cell populations beyond the fibroblast which could be targeted for therapeutic purposes. The preclinical and clinical development of novel drug candidates is hampered by profound challenges such as a lack of sensitive clinical outcomes or suitable biomarkers that would provide an early indication of patient benefit. With the availability of these anti-fibrotic treatments, it has become even more difficult to demonstrate added efficacy, in particular in short-term clinical studies. Patient heterogeneity and the paucity of biomarkers of disease activity further complicate clinical development. It is conceivable that future treatment of pulmonary fibrosis will need to embrace more precision in treating the right patient at the right time, explore novel measures of efficacy, and likely combine treatment options.

In Vivo Targeting of CXCR4-New Horizons

Given its pre-eminent role in the context of tumor cell growth as well as metastasis, the C-X-C motif chemokine receptor 4 (CXCR4) has attracted a lot of interest in the field of nuclear oncology, and clinical evidence on the high potential of CXCR4-targeted theranostics is constantly accumulating. Additionally, since CXCR4 also represents a key player in the orchestration of inflammatory responses to inflammatory stimuli, based on its expression on a variety of pro- and anti-inflammatory immune cells (e.g., macrophages and T-cells), CXCR4-targeted inflammation imaging has recently gained considerable attention. Therefore, after briefly summarizing the current clinical status quo of CXCR4-targeted theranostics in cancer, this review primarily focuses on imaging of a broad spectrum of inflammatory diseases via the quantification of tissue infiltration with CXCR4-expressing immune cells. An up-to-date overview of the ongoing preclinical and clinical efforts to visualize inflammation and its resolution over time is provided, and the predictive value of the CXCR4-associated imaging signal for disease outcome is discussed. Since the sensitivity and specificity of CXCR4-targeted immune cell imaging greatly relies on the availability of suitable, tailored imaging probes, recent developments in the field of CXCR4-targeted imaging agents for various applications are also addressed.

Progress and Research Priorities in Imaging Genomics for Heart and Lung Disease: Summary of an NHLBI Workshop

Imaging genomics is a rapidly evolving field that combines state-of-the-art bioimaging with genomic information to resolve phenotypic heterogeneity associated with genomic variation, improve risk prediction, discover prevention approaches, and enable precision diagnosis and treatment. Contemporary bioimaging methods provide exceptional resolution generating discrete and quantitative high-dimensional phenotypes for genomics investigation. Despite substantial progress in combining high-dimensional bioimaging and genomic data, methods for imaging genomics are evolving. Recognizing the potential impact of imaging genomics on the study of heart and lung disease, the National Heart, Lung, and Blood Institute convened a workshop to review cutting-edge approaches and methodologies in imaging genomics studies, and to establish research priorities for future investigation. This report summarizes the presentations and discussions at the workshop. In particular, we highlight the need for increased availability of imaging genomics data in diverse populations, dedicated focus on less common conditions, and centralization of efforts around specific disease areas.

Pirfenidone attenuates synovial fibrosis and postpones the progression of osteoarthritis by anti-fibrotic and anti-inflammatory properties in vivo and in vitro

Background

Osteoarthritis (OA) is a disease of the entire joint involving synovial fibrosis and inflammation. Pathological changes to the synovium can accelerate the progression of OA. Pirfenidone (PFD) is a potent anti-fibrotic drug with additional anti-inflammatory properties. However, the influence of PFD on OA is unknown.

Methods

Proliferation of human fibroblast-like synoviocytes (FLSs) after treatment with TGF-β1 or PFD was evaluated using a Cell Counting Kit-8 assay and their migration using a Transwell assay. The expression of fibrosis-related genes (COL1A1, TIMP-1, and ACTA-2) and those related to inflammation (IL-6 and TNF-α) was quantified by real-time quantitative PCR. The protein expression levels of COL1A1, α-SMA (coded by ACTA-2), IL-6 and TNF-α were measured by enzyme-linked immunosorbent assay. A rabbit model of OA was established and then PFD was administered by gavage. The expression of genes related to fibrosis (COL1A1, TIMP-1, and ADAM-12) and inflammation (IL-6 and TNF-α) was measured using RNA extracted from the synovium. Synovial tissue was examined histologically after staining with H&E, Masson’s trichrome, and immunofluorescence. Synovitis scores, the volume fraction of collagen, and mean fluorescence intensity were calculated. Degeneration of articular cartilage was analyzed using a Safranin O-fast green stain and OARSI grading.

Results

The proliferation of FLSs was greatest when induced with 2.5 ng/ml TGF-β1 although it did not promote their migration. Therefore, 2.5 ng/ml TGF-β1 was used to stimulate the FLSs and evaluate the effects of PFD, which inhibited the migration of FLSs at concentrations as low as 1.0 mg/ml. PFD decreased the expression of COL1A1 while TGF-β1 increased both mRNA and protein expression levels of IL-6 but had no effect on α-SMA or TNF-α expression. PFD decreased mRNA expression levels of COL1A1, IL-6, and TNF-α in vivo. H&E staining and synovitis scores indicated that PFD reduced synovial inflammation, while Masson’s trichrome and immunofluorescence staining suggested that PFD decreased synovial fibrosis. Safranin O-Fast Green staining and the OARSI scores demonstrated that PFD delayed the progression of OA.

Conclusions

PFD attenuated synovial fibrosis and inflammation, and postponed the progression of osteoarthritis in a modified Hulth model of OA in rabbits, which was related to its anti-fibrotic and anti-inflammatory properties.