Fibrosis imaging: Current concepts and future directions

Magnetic resonance diffusion tensor imaging is superior to arterial spin labeling in detecting renal allograft fibrosis

Background

Although both magnetic resonance (MR) diffusion tensor imaging (DTI) and arterial spin labeling (ASL) have been demonstrated to be useful for the assessment of renal allograft fibrosis, their diagnostic value for renal allograft fibrosis is rarely compared. In this study, we collected a relatively large sample size to compare the value of DTI and ASL in the assessment of renal transplantation (RT) fibrosis.

Methods

This study included 141 kidney transplant recipients who underwent DTI, ASL, and biopsy. The renal allograft fibrosis was divided into ci0, ci1, ci2, and ci3 fibrosis groups according to the biopsy results. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), and renal blood flow (RBF) were calculated. One-way analysis of variance (ANOVA) was used to compare the differences of functional magnetic resonance imaging (MRI) parameters between different fibrosis subgroups. The area under the receiver operating characteristic curve (AUC) was calculated to evaluate diagnostic performance.

Results

The medullary FA values in ci2 (0.27±0.04, P<0.001) and ci3 (0.21±0.03, P<0.001) groups were significantly lower than those in ci0 group (0.31±0.05). The medullary FA value in ci3 group (0.21±0.03) was significantly lower than that in ci1 group (0.30±0.07, P<0.001) and ci2 group (0.27±0.04, P<0.01). The AUC of DTI was found to be higher than that of ASL in accurately identifying renal allograft fibrosis, and the result was statistically significant in differentiating ci0-2 group and ci3 group (ci0 vs. ci1-3, 0.725 vs. 0.712, P>0.05; ci0-1 vs. ci2-3, 0.787 vs. 0.735, P>0.05; ci0-2 vs. ci3, 0.945 vs. 0.802, P<0.05).

Conclusions

DTI has a higher diagnostic value than ASL in noninvasive identification of the degree of renal allograft fibrosis.

PU.1/Spi1 exacerbates ischemia-reperfusion induced acute kidney injury via upregulating Gata2 and promoting fibroblast activation

Previous studies on acute kidney injury (AKI) have predominantly focused on renal tubular cells, while the specific role of fibroblasts has been largely neglected. Recent evidence shows that PU.1/Spi1, a transcription factor, is an important modulator of fibroblast activation, whereas pharmacological and genetic silencing of PU.1/Spi1 disrupts the fibrotic network and reprograms activated fibroblasts into quiescent fibroblasts. In this study we investigated whether and how PU.1/Spi1 regulated renal fibroblast activation during AKI. An AKI model was established in male mice by clamping bilateral renal arteries for 30 min. Mice were sacrificed and blood and kidney samples were collected 48 h after the surgery. We showed that the expression level of PU.1/Spi1 was significantly upregulated in ischemia/reperfusion (I/R)-induced AKI and PU.1/Spi1 was specifically localized in fibroblasts. Meanwhile, we observed that a massive activation of fibroblasts occurred at the early stage of AKI. PU.1/Spi1 knockout significantly attenuated the activation of fibroblasts along with the decreased release of inflammatory factors and tubular injury. Bioinformatic analysis revealed that GATA binding protein 2 (Gata2), an evolutionarily conserved gene, might be a downstream target gene of PU.1/Spi1. In primary cultured mouse kidney fibroblasts subjected to hypoxia/reoxygenation (H/R), the expression levels of PU.1/Spi1, Gata2 and α-SMA were significantly upregulated. Activated fibroblasts exhibited elevated proliferative capacity, evidenced by upregulated proliferating cell nuclear antigen (PCNA) and cell cycle proteins such as cyclin B1 and cyclin D3. The secretion of inflammatory factors was increased in the activated fibroblasts. Conditioned medium from H/R-treated fibroblasts induced tubular cell injury and increased apoptosis. Using chromatin immunoprecipitation and promoter-luciferase assays, we demonstrated that PU.1/Spi1 was able to bind to the promoter region of Gata2 and enhanced its transcription. Our results show that interstitial fibroblasts are activated at the early stage of I/R-induced AKI and involved in renal injury. Upregulated PU.1/Spi1 stimulates fibroblast activation by upregulating its downstream gene Gata2. Inhibiting the activation of fibroblasts may have a beneficial effect on AKI.

Targeted imaging of pulmonary fibrosis by a cyclic peptide LyP-1

Pulmonary fibrosis (PF) is an interstitial chronic lung disease characterized by interstitial inflammation and extracellular matrix deposition, resulting in progressive lung dysfunction and ultimate respiratory failure. However, lacking of precise and noninvasive tracers for fibrotic lesions limits timely diagnosis and treatment. Here, we identified LyP-1, a cyclic peptide, as a specific and sensitive tracer for PF detection using PET/CT imaging. FITC-LyP-1 selectively recognized fibrotic regions in bleomycin-induced PF mice, indicating its targeting capability. The colocalization of FITC-LyP-1 with extracellular collagen I within the fibrotic lesions validated its specificity, and further analysis revealed several potential target molecules. In the in vivo application studies, radiolabeled [68Ga]Ga-LyP-1 showed significantly increased lung uptake in PF mice, specifically enriching fibrotic regions on PET/CT imaging. Notably, compared to CT imaging that showed increased mean lung density throughout the phases after bleomycin-administration, lung uptake of [68Ga]Ga-LyP-1 was only increased in the later phase, indicating that LyP-1 recognizes the fibrous changes rather than the inflammatory cells in vivo. These results suggest that the new radiotracer [68Ga]Ga-LyP-1 specifically detects the extracellular matrix in fibrotic lungs. LyP-1 shows promise as a noninvasive tracer for assessing human pulmonary fibrosis, offering potential for improved diagnostic accuracy and timely intervention.

Therapy Combining Sorafenib and Natural Killer Cells for Hepatocellular Carcinoma: Insights from Magnetic Resonance Imaging and Histological Analyses

Background/Objectives: Hepatocellular carcinoma (HCC) remains a significant global health issue due to its high mortality rate and resistance to standard treatments. Sorafenib, the first-line systemic therapy for unresectable HCC, shows limited effectiveness due to resistance and severe side effects. Recent studies suggest that combining sorafenib with immunotherapy, particularly natural killer (NK) cells, may improve treatment outcomes. Methods: This study examined the effectiveness of sorafenib combined with NK cells pretreated with interleukin-12 (IL-12) and interleukin-18 (IL-18) in a rat HCC model. Tumor progression and treatment outcomes were assessed using MRI and histological analysis. Results: The results show that combination therapy significantly reduced tumor growth, increased tumor cell density, and inhibited angiogenesis and fibrosis in the tumor microenvironment. The sorafenib- and IL-12/IL-18-pretreated NK cell combination enhanced tumor inhibition by overcoming drug resistance and modulating the immune response. Conclusions: This study suggests that this combination therapy could be a promising strategy for treating HCC, offering both direct antitumor effects and modification of the tumor microenvironment for better clinical outcomes.

Role of Essential Oils and Antioxidants in the Treatment of Fibrosis

Fibrosis is the leading cause of many lethal diseases. It is characterized by the accumulation of extracellular matrix (ECM) components, which leads to damaged tissue functioning in the influenced organs. Essential oils are concentrated hydrophobic liquid having volatile compounds extracted from plant or plant parts while antioxidants are the compounds that help in scavenging free radicals and prevent reducing the oxidation processes. In this review, challenges that come during the treatment of fibrosis have been covered, mechanism of action of both essential oil and antioxidants is also outlined in this article. This review aimed to provide scientific fundamental and knowledge, ideas for the development and application of essential oils and antioxidants in the treatment of fibrosis.

Diagnostic and evaluative efficiency of 68Ga-FAPI-04 in skeletal muscle injury

BACKGROUND

Skeletal muscles are vital for daily function, yet assessing their injuries remain challenging. We aimed to elucidate the effectiveness of 68Ga-FAPI-04 in evaluating skeletal muscle remodeling.

RESULTS

C2C12 cells were subjected to graded H2O2 stimulation in vitro, revealing an initial rise and subsequent decline in fibroblast activation protein (FAP) expression as H2O2 concentration increased. In vivo, a murine triceps surae injury model was created using various solutions to simulate normal repair, mild repair failure, and severe repair failure. Assessments were conducted on days 1, 3, 7, and 14 using PET, MRI, and ultrasound. With 68Ga-FAPI-04, the normal and mild repair failure groups showed significantly higher SUVmax and T/B ratios on day 1 compared to the severe repair failure group. These values gradually decreased in the normal repair group, becoming negligible after day 7. MRI results for the normal repair group showed low to moderate signal intensity by day 7. A clinical study retrospectively evaluated post-hip arthroplasty patient images at intervals of 1 month, 2-3 months, 5-6 months, and over 7 months. In these patients, 18F-FDG SUVmax and volume remained relatively stable over time, while 68Ga-FAPI-04 SUVmax initially increased, then decreased, with a consistent reduction in volume.

CONCLUSION

In skeletal muscle injuries, FAP demonstrates a distinctive mechanism of action, and 68Ga-FAPI-04, in comparison to other tests, more precisely captures alterations in lesion site uptake intensity and volume.

TRIAL REGISTRATION

Trial registration: ChiCTR2000041204. Registered 22 December 2020, https://www.chictr.org.cn/showproj.html?proj=66211.

The current landscape of antifibrotic therapy across different organs: A systematic approach

Fibrosis is a common pathological process that can affect virtually all the organs, but there are hardly any effective therapeutic options. This has led to an intense search for antifibrotic therapies over the last decades, with a great number of clinical assays currently underway. We have systematically reviewed all current and recently finished clinical trials involved in the development of new antifibrotic drugs, and the preclinical studies analyzing the relevance of each of these pharmacological strategies in fibrotic processes affecting tissues beyond those being clinically studied. We analyze and discuss this information with the aim of determining the most promising options and the feasibility of extending their therapeutic value as antifibrotic agents to other fibrotic conditions.

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Imaging at the nexus: how state of the art imaging techniques can enhance our understanding of cancer and fibrosis

Both cancer and fibrosis are diseases involving dysregulation of cell signaling pathways resulting in an altered cellular microenvironment which ultimately leads to progression of the condition. The two disease entities share common molecular pathophysiology and recent research has illuminated the how each promotes the other. Multiple imaging techniques have been developed to aid in the early and accurate diagnosis of each disease, and given the commonalities between the pathophysiology of the conditions, advances in imaging one disease have opened new avenues to study the other. Here, we detail the most up-to-date advances in imaging techniques for each disease and how they have crossed over to improve detection and monitoring of the other. We explore techniques in positron emission tomography (PET), magnetic resonance imaging (MRI), second generation harmonic Imaging (SGHI), ultrasound (US), radiomics, and artificial intelligence (AI). A new diagnostic imaging tool in PET/computed tomography (CT) is the use of radiolabeled fibroblast activation protein inhibitor (FAPI). SGHI uses high-frequency sound waves to penetrate deeper into the tissue, providing a more detailed view of the tumor microenvironment. Artificial intelligence with the aid of advanced deep learning (DL) algorithms has been highly effective in training computer systems to diagnose and classify neoplastic lesions in multiple organs. Ultimately, advancing imaging techniques in cancer and fibrosis can lead to significantly more timely and accurate diagnoses of both diseases resulting in better patient outcomes.

Platelet-derived growth factor receptor β-targeted positron emission tomography imaging for the noninvasive monitoring of liver fibrosis

PURPOSE

Noninvasive quantifying activated hepatic stellate cells (aHSCs) by molecular imaging is helpful for assessing disease progression and therapeutic responses of liver fibrosis. Our purpose is to develop platelet-derived growth factor receptor β (PDGFRβ)-targeted radioactive tracer for assessing liver fibrosis by positron emission tomography (PET) imaging of aHSCs.

METHODS

Comparative transcriptomics, immunofluorescence staining and flow cytometry were used to evaluate PDGFRβ as biomarker for human aHSCs and determine the correlation of PDGFRβ with the severity of liver fibrosis. The high affinity affibody for PDGFRβ (ZPDGFRβ) was labeled with gallium-68 (68Ga) for PET imaging of mice with carbon tetrachloride (CCl4)-induced liver fibrosis. Binding of the [68Ga]Ga-labeled ZPDGFRβ ([68Ga]Ga-DOTA-ZPDGFRβ) for aHSCs in human liver tissues was measured by autoradiography.

RESULTS

PDGFRβ overexpressed in aHSCs was highly correlated with the severity of liver fibrosis in patients and CCl4-treated mice. The 68Ga-labeled ZPDGFRβ affibody ([68Ga]Ga-DOTA-ZPDGFRβ) showed PDGFRβ-dependent binding to aHSCs. According to the PET imaging, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ increased with the accumulation of aHSCs and collagens in the fibrotic livers of mice. In contrast, hepatic uptake of [68Ga]Ga-DOTA-ZPDGFRβ decreased with spontaneous recovery or treatment of liver fibrosis, indicating that the progression and therapeutic responses of liver fibrosis in mice could be visualized by PDGFRβ-targeted PET imaging. [68Ga]Ga-DOTA-ZPDGFRβ also bound human aHSCs and visualized fibrosis in patient-derived liver tissues.

CONCLUSIONS

PDGFRβ is a reliable biomarker for both human and mouse aHSCs. PDGFRβ-targeted PET imaging could be used for noninvasive monitoring of liver fibrosis in mice and has great potential for clinical translation.

Point-of-care diagnosis of tissue fibrosis: a review of advances in vibrational spectroscopy with machine learning

Histopathology is the gold standard for diagnosing fibrosis, but its routine use is constrained by the need for additional stains, time, personnel and resources. Vibrational spectroscopy is a novel technique that offers an alternative atraumatic approach, with short scan times, while providing metabolic and morphological data. This review evaluates vibrational spectroscopy for the assessment of fibrosis, with a focus on point-of-care capabilities. OVID Medline, Embase and Cochrane databases were systematically searched using PRISMA guidelines for search terms including vibrational spectroscopy, human tissue and fibrosis. Studies were stratified based on imaging modality and tissue type. Outcomes recorded included tissue type, machine learning technique, metrics for accuracy and author conclusions. Systematic review yielded 420 articles, of which 14 were relevant. Ten of these articles considered mid-infrared spectroscopy, three dealt with Raman spectroscopy and one with near-infrared spectroscopy. The metrics for detecting fibrosis were Pearson correlation coefficients ranging from 0.65-0.98; sensitivity from 76-100%; specificity from 90-99%; area under receiver operator curves from 0.83-0.98; and accuracy of 86-99%. Vibrational spectroscopy identified fibrosis in myeloproliferative neoplasms in bone, cirrhotic and hepatocellular carcinoma in liver, end-stage heart failure in cardiac tissue and following laser ablation for acne in skin. It also identified interstitial fibrosis as a predictor of early renal transplant rejection in renal tissue. Vibrational spectroscopic techniques can therefore accurately identify fibrosis in a range of human tissues. Emerging data show that it can be used to quantify, classify and provide data about the nature of fibrosis with a high degree of accuracy with potential scope for point-of-care use.

Iliopsoas fibrosis after revision of total hip arthroplasty revealed by 68Ga-FAPI PET/CT: a case report

Background

Total hip arthroplasty (THA) is a well-established surgical procedure that has been extensively validated to alleviate pain, enhance joint function, improve the ability to perform daily activities, and enhance overall quality of life. However, this procedure is associated with certain complications, among which skeletal muscle fibrosis is a frequently overlooked but significant complication that can lead to persistent pain. Currently, there is no effective method for diagnosing skeletal muscle fibrosis following total hip arthroplasty.

Case report

We report a 75-year-old male patient who complained of left groin pain after revision total hip arthroplasty. Serological examinations, X-rays, and bone scan results were all normal. However, during the 68Ga-FAPI PET/CT examination, we observed significant radiotracer uptake along the iliopsoas muscle. This abnormal uptake pattern suggested potential biological activity in this specific area. Combined with physical examination, the patient was diagnosed with iliopsoas fibrosis.

Conclusions

The presented images indicated that the uptake pattern was an important indicator for diagnosis, and the prospect of fibroblast activation protein in the diagnosis of skeletal muscle fibrosis has shown certain application value.

Role and new insights of microfibrillar-associated protein 4 in fibrotic diseases

Fibrosis is one of the most worrisome complications of chronic inflammatory diseases, leading to tissue damage, organ failure, and ultimately, death. The most notable pathological characteristic of fibrosis is the excessive accumulation of extracellular matrix (ECM) components such as collagen and fibronectin adjacent to foci of inflammation or damage. The human microfibrillar-associated protein 4 (MFAP4), an important member of the superfamily of fibrinogen-related proteins, is considered to have an extremely important role in ECM transformation of fibrogenesis. This review summarizes the structure, characteristics, and physiological functions of MFAP4 and the importance of MFAP4 in various fibrotic diseases. Meanwhile, we elaborated the underlying actions and mechanisms of MFAP4 in the development of fibrosis, suggesting that a better understand of MFAP4 broadens novel perspective for early screening, diagnosis, prognostic risk assessment, and treatment of fibrotic diseases.

Hybrid ultrasound and single wavelength optoacoustic imaging reveals muscle degeneration in peripheral artery disease

Peripheral arterial disease (PAD) leads to chronic vascular occlusion and results in end organ damage in critically perfused limbs. There are currently no clinical methods available to determine the muscular damage induced by chronic mal-perfusion. This monocentric prospective cross-sectional study investigated n = 193 adults, healthy to severe PAD, in order to quantify the degree of calf muscle degeneration caused by PAD using a non-invasive hybrid ultrasound and single wavelength optoacoustic imaging (US/SWL-OAI) approach. While US provides morphologic information, SWL-OAI visualizes the absorption of pulsed laser light and the resulting sound waves from molecules undergoing thermoelastic expansion. US/SWL-OAI was compared to multispectral data, clinical disease severity, angiographic findings, phantom experiments, and histological examinations from calf muscle biopsies. We were able to show that synergistic use of US/SWL-OAI is most likely to map clinical degeneration of the muscle and progressive PAD.

Utilizing MRI, [18F]FDG-PET and [89Zr]Zr-DFO-28H1 FAP-PET tracer to assess inflammation and fibrogenesis in a reproducible lung injury rat model: a multimodal imaging study

Objective

Accurate imaging biomarkers that indicate disease progression at an early stage are highly important to enable timely mitigation of symptoms in progressive lung disease. In this context, reproducible experimental models and readouts are key. Here, we aim to show reproducibility of a lung injury rat model by inducing disease and assessing disease progression by multi-modal non-invasive imaging techniques at two different research sites. Furthermore, we evaluated the potential of fibroblast activating protein (FAP) as an imaging biomarker in the early stage of lung fibrosis.

Methods

An initial lung injury rat model was set up at one research site (Lund University, Lund, Sweden) and repeated at a second site (Radboudumc, Nijmegen, The Netherlands). To induce lung injury, Sprague-Dawley rats received intratracheal instillation of bleomycin as one single dose (1,000 iU in 200 µL) or saline as control. Thereafter, longitudinal images were acquired to track inflammation in the lungs, at 1 and 2 weeks after the bleomycin challenge by magnetic resonance imaging (MRI) and [18F]FDG-PET. After the final [18F]FDG-PET scan, rats received an intravenous tracer [89Zr]Zr-DFO-28H1 (anti-FAP antibody) and were imaged at day 15 to track fibrogenesis. Upon termination, bronchoalveolar lavage (BAL) was performed to assess cell and protein concentration. Subsequently, the biodistribution of [89Zr]Zr-DFO-28H1 was measured ex vivo and the spatial distribution in lung tissue was studied by autoradiography. Lung sections were stained and fibrosis assessed using the modified Ashcroft score.

Results

Bleomycin-challenged rats showed body weight loss and increased numbers of immune cells and protein concentrations after BAL compared with control animals. The initiation and progression of the disease were reproduced at both research sites. Lung lesions in bleomycin-exposed rats were visualized by MRI and confirmed by histology. [18F]FDG uptake was higher in the lungs of bleomycin-challenged rats compared with the controls, similar to that observed in the Lund study. [89Zr]Zr-DFO-28H1 tracer uptake in the lung was increased in bleomycin-challenged rats compared with control rats (p = 0.03).

Conclusion

Here, we demonstrate a reproducible lung injury model and monitored disease progression using conventional imaging biomarkers MRI and [18F]FDG-PET. Furthermore, we showed the first proof-of-concept of FAP imaging. This reproducible and robust animal model and imaging experimental set-up allows for future research on new therapeutics or biomarkers in lung disease.

Machine learning algorithm predicts fibrosis-related blood diagnosis markers of intervertebral disc degeneration

BACKGROUND

Intervertebral disc cell fibrosis has been established as a contributing factor to intervertebral disc degeneration (IDD). This study aimed to identify fibrosis-related diagnostic genes for patients with IDD.

METHODS

RNA-sequencing data was downloaded from Gene Expression Omnibus (GEO) database. The diagnostic genes was identified using Random forest based on the differentially expressed fibrosis-related genes (DE-FIGs) between IDD and control samples. The immune infiltration states in IDD and the regulatory network as well as potential drugs targeted diagnostic genes were investigated. Quantitative Real-Time PCR was conducted for gene expression valifation.

RESULTS

CEP120 and SPDL1 merged as diagnostic genes. Substantial variations were observed in the proportions of natural killer cells, neutrophils, and myeloid-derived suppressor cells between IDD and control samples. Further experiments indicated that AC144548.1 could regulate the expressions of SPDL1 and CEP120 by combininghsa-miR-5195-3p and hsa-miR-455-3p, respectively. Additionally, transcription factors FOXM1, PPARG, and ATF3 were identified as regulators of SPDL1 and CEP120 transcription. Notably, 56 drugs were predicted to target these genes. The down-regulation of SPDL1 and CEP120 was also validated.

CONCLUSION

This study identified two diagnostic genes associated with fibrosis in patients with IDD. Additionally, we elucidated their potential regulatory networks and identified target drugs, which offer a theoretical basis and reference for further study into fibrosis-related genes involved in IDD.

Collagenase treatment reduces the anisotropy of ultrasonic backscatter in rat myocardium by reducing collagen crosslinks

Dysregulation of collagen deposition, degradation, and crosslinking in the heart occur in response to increased physiological stress. Collagen content has been associated with ultrasonic backscatter (brightness), and we have shown that the anisotropy of backscatter can be used to measure myofiber alignment, that is, variation in the brightness of a left ventricular short-axis ultrasound. This study investigated collagen's role in anisotropy of ultrasonic backscatter; female Sprague-Dawley rat hearts were treated with a collagenase-containing solution, for either 10 or 30 min, or control solution for 30 min. Serial ultrasound images were acquired at 2.5-min intervals throughout collagenase treatment. Ultrasonic backscatter was assessed from anterior and posterior walls, where collagen fibrils are predominately aligned perpendicular to the angle of insonification, and the lateral and septal walls, where collagen is predominately aligned parallel to the angle of insonification. Collagenase digestion reduced backscatter anisotropy within the myocardium. Collagen remains present in the myocardium throughout collagenase treatment, but crosslinking is altered within 10 min. These data suggest that crosslinking of collagen modulates the anisotropy of ultrasonic backscatter. An Anisotropy Index, derived from differences in backscatter from parallel and perpendicularly aligned fibers, may provide a noninvasive index to monitor the progression and state of myocardial fibrosis.

Tissue fibrosis induced by radiotherapy: current understanding of the molecular mechanisms, diagnosis and therapeutic advances

Cancer remains the leading cause of death around the world. In cancer treatment, over 50% of cancer patients receive radiotherapy alone or in multimodal combinations with other therapies. One of the adverse consequences after radiation exposure is the occurrence of radiation-induced tissue fibrosis (RIF), which is characterized by the abnormal activation of myofibroblasts and the excessive accumulation of extracellular matrix. This phenotype can manifest in multiple organs, such as lung, skin, liver and kidney. In-depth studies on the mechanisms of radiation-induced fibrosis have shown that a variety of extracellular signals such as immune cells and abnormal release of cytokines, and intracellular signals such as cGAS/STING, oxidative stress response, metabolic reprogramming and proteasome pathway activation are involved in the activation of myofibroblasts. Tissue fibrosis is extremely harmful to patients' health and requires early diagnosis. In addition to traditional serum markers, histologic and imaging tests, the diagnostic potential of nuclear medicine techniques is emerging. Anti-inflammatory and antioxidant therapies are the traditional treatments for radiation-induced fibrosis. Recently, some promising therapeutic strategies have emerged, such as stem cell therapy and targeted therapies. However, incomplete knowledge of the mechanisms hinders the treatment of this disease. Here, we also highlight the potential mechanistic, diagnostic and therapeutic directions of radiation-induced fibrosis.

Kidney fibrosis: Emerging diagnostic and therapeutic strategies

An increasing number of patients worldwide suffers from chronic kidney disease (CKD). CKD is accompanied by kidney fibrosis, which affects all compartments of the kidney, i.e., the glomeruli, tubulointerstitium, and vasculature. Fibrosis is the best predictor of progression of kidney diseases. Currently, there is no specific anti-fibrotic therapy for kidney patients and invasive renal biopsy remains the only option for specific detection and quantification of kidney fibrosis. Here we review emerging diagnostic approaches and potential therapeutic options for fibrosis. We discuss how translational research could help to establish fibrosis-specific endpoints for clinical trials, leading to improved patient stratification and potentially companion diagnostics, and facilitating and optimizing development of novel anti-fibrotic therapies for kidney patients.

New therapeutic approaches against pulmonary fibrosis

Pulmonary fibrosis is the end-stage change of a large class of lung diseases characterized by the proliferation of fibroblasts and the accumulation of a large amount of extracellular matrix, accompanied by inflammatory damage and tissue structure destruction, which also shows the normal alveolar tissue is damaged and then abnormally repaired resulting in structural abnormalities (scarring). Pulmonary fibrosis has a serious impact on the respiratory function of the human body, and the clinical manifestation is progressive dyspnea. The incidence of pulmonary fibrosis-related diseases is increasing year by year, and no curative drugs have appeared so far. Nevertheless, research on pulmonary fibrosis have also increased in recent years, but there are no breakthrough results. Pathological changes of pulmonary fibrosis appear in the lungs of patients with coronavirus disease 2019 (COVID-19) that have not yet ended, and whether to improve the condition of patients with COVID-19 by means of the anti-fibrosis therapy, which are the questions we need to address now. This review systematically sheds light on the current state of research on fibrosis from multiple perspectives, hoping to provide some references for design and optimization of subsequent drugs and the selection of anti-fibrosis treatment plans and strategies.

Development and Deployment of a Novel Diagnostic Tool Based on Conventional Ultrasound for Fibrosis Assessment in Chronic Kidney Disease

RATIONALE AND OBJECTIVES

Accurate identification of risk information about fibrosis severity is crucial for clinical decision-making and clinical management of patients with chronic kidney disease (CKD). This study aimed to develop an ultrasound (US)-derived computer-aided diagnosis tool for identifying CKD patients at high risk of developing moderate-severe renal fibrosis, in order to optimize treatment regimens and follow-up strategies.

MATERIALS AND METHODS

A total of 162 CKD patients undergoing renal biopsies and US examinations were prospectively enrolled and randomly divided into training (n = 114) and validation (n = 48) cohorts. A multivariate logistic regression approach was employed to develop the diagnostic tool named S-CKD for differentiating moderate-severe renal fibrosis from mild one in the training cohort by integrating the significant variables, which were screened out from demographic characteristics and conventional US features via the least absolute shrinkage and selection operator regression algorithm. The S-CKD was then deployed as both an online web-based and an offline document-based, easy-to-use auxiliary device. In both the training and validation cohorts, the S-CKD's diagnostic performance was evaluated through discrimination and calibration. The clinical benefit of using S-CKD was revealed by decision curve analysis (DCA) and clinical impact curves.

RESULTS

The proposed S-CKD achieved an area under the receiver operating characteristic curve of 0.84 (95% confidence interval (CI): 0.77-0.91) and 0.81 (95% CI: 0.68-0.94) in the training and validation cohorts, respectively, indicating satisfactory diagnosis performance. Results of the calibration curves showed that S-CKD has excellent predictive accuracy (Hosmer-Lemeshow test: training cohort, p = 0.497; validation cohort, p = 0.205). The DCA and clinical impact curves exhibited a high clinical application value of the S-CKD at a wide range of risk probabilities.

CONCLUSION

The S-CKD tool developed in this study is capable of discriminating between mild and moderate-severe renal fibrosis in patients with CKD and achieving promising clinical benefits, which may aid clinicians in personalizing medical decision-making and follow-up arrangement.

Vimentin-targeted radiopeptide 99m Tc-HYNIC-(tricine/EDDA)-VNTANST: a promising drug for pulmonary fibrosis imaging

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by the accumulation of extracellular matrix. Because there is no effective treatment for advanced IPF to date, its early diagnosis can be critical. Vimentin is a cytoplasmic intermediate filament that is significantly up-regulated at the surface of fibrotic foci with a crucial role in fibrotic morphological changes.

METHODS

In the present study, VNTANST sequence as a known vimentin-targeting peptide was conjugated to hydrazinonicotinic acid (HYNIC) and labeled with 99m Tc. The stability test in saline and human plasma and log P determination were performed. Next, the biodistribution study and single photon emission computed tomography (SPECT) integrated with computed tomography (CT) scanning were performed in healthy and bleomycin-induced fibrosis mice models.

RESULTS

The 99m Tc-HYNIC-(tricine/EDDA)-VNTANST showed a hydrophilic nature (log P  = -2.20 ± 0.38) and high radiochemical purity > 97% and specific activity (336 Ci/mmol). The radiopeptide was approximately 93% and 86% intact in saline and human plasma within 6 h, respectively. The radiopeptide was substantially accumulated in the pulmonary fibrotic lesions (test vs. control = 4.08 ± 0.08% injected dose per gram (ID/g) vs. 0.36 ± 0.01% ID/g at 90 min postinjection). SPECT-CT images in fibrosis-bearing mice also indicated the fibrotic foci and kidneys.

CONCLUSION

Because there is no available drug for the treatment of advanced pulmonary fibrosis, early diagnosis is the only chance. The 99m Tc-HYNIC-(tricine/EDDA)-VNTANST could be a potential tracer for SPECT imaging of pulmonary fibrosis.

Novel Imaging Technologies for Accurate Assessment of Cardiac Allograft Performance

Purpose of the Review

The current lack of objective and quantitative assessment techniques to determine cardiac graft relative viability results in risk-averse decision-making, which negatively impact the utilization of cardiac grafts. The purpose of this review is to highlight the current deficiencies in cardiac allograft assessment before focusing on novel cardiac assessment techniques that exploit conventional and emerging imaging modalities, including ultrasound, magnetic resonance, and spectroscopy.

Recent Findings

Extensive work is ongoing by the scientific community to identify improved objective metrics and tools for cardiac graft assessment, with the goal to safely increasing the number and proportion of hearts accepted for transplantation.

Summary

This review briefly discusses the in situ and ex vivo tools currently available for clinical organ assessment, before focusing on the individual capabilities of ultrasound, magnetic resonance, and spectroscopy to provide insightful, non-invasive information regarding cardiac graft functional and metabolic status that may be used to predict outcome after transplantation.

Multifaced roles of desmoplastic reaction and fibrosis in pancreatic cancer progression: Current understanding and future directions

Desmoplastic reaction is a fibrosis reaction that is characterized by a large amount of dense extracellular matrix (ECM) and dense fibrous stroma. Fibrotic stroma around the tumor has several different components, including myofibroblasts, collagen, and other ECM molecules. This stromal reaction is a natural response to the tissue injury process, and fibrosis formation is a key factor in pancreatic cancer development. The fibrotic stroma of pancreatic cancer is associated with tumor progression, metastasis, and poor prognosis. Reportedly, multiple processes are involved in fibrosis, which is largely associated with the upregulation of various cytokines, chemokines, matrix metalloproteinases, and other growth factors that promote tumor growth and metastasis. Fibrosis is also associated with immunosuppressive cell recruitment, such as regulatory T cells (Tregs) with suppressing function to antitumor immunity. Further, dense fibrosis restricts the flow of nutrients and oxygen to the tumor cells, which can contribute to drug resistance. Furthermore, the dense collagen matrix can act as a physical barrier to block the entry of drugs into the tumor, thereby further contributing to drug resistance. Thus, understanding the mechanism of desmoplastic reaction and fibrosis in pancreatic cancer will open an avenue to innovative medicine and improve the prognosis of patients suffering from this disease.

Potential Effect of Combined Exposure of Crystalline Silica Dust and Cigarette Smoking on the Incidence of Silicosis among Chinese Male Stone Processing Workers: A Cross-Sectional Study

Background: Silicosis is a progressive and irreversible disease primarily caused by exposure to crystalline silica dust and, to a lesser extent, cigarette smoking. However, further research is needed to validate the potential combined effect of these risk factors on the increased incidence of the disease. Methods: A total of 1688 male workers employed at a Chinese stone processing plant between 1 January 1999 and 31 December 2019, were included in the study. Cumulative exposure to industrial crystalline silica dust and packyears of smoking were collected through health surveillance, and odds ratios (ORs) with 95% confidence intervals (CIs) for silicotic changes due to industrial silica exposure and cigarette smoking were estimated using logistic regression models. Results: Among all participants, a significant exposure-response relationship was observed between long-term exposure to industrial silica dust and radiographic findings resembling silicosis (OR 1.74, 95% CI 1.25 to 2.41). However, among middle-aged workers, a weak and statistically insignificant relationship was found between prolonged cigarette smoking and X-ray evidence of lung silicosis (OR 1.59, 95% CI 1.00 to 2.53). Furthermore, significant combined effects, exceeding the additive models, were identified in each age group and employment sector (relative risk due to interaction 0.51, 95% CI 0.08 to 3.42). Conclusions: It is critically important to implement effective dust removal measures and tobacco control strategies in order to enhance respiratory health among employees across all age groups in the stone processing industry.

Image quality and evaluation ability of magnetic resonance imaging techniques for thyroid-associated ophthalmopathy: Dixon fat-suppression technique vs. spectral attenuated inversion recovery

Purpose

We aimed to compare two magnetic resonance imaging (MRI) techniques, Dixon and spectral attenuated inversion recovery (SPAIR) fat-suppression, in terms of image quality and suitability for evaluating thyroid-associated ophthalmopathy (TAO) lesion characteristics.

Methods

This cross-sectional, retrospective study involved 70 patients with TAO (140 eyes) who underwent orbital coronal MRI examinations, including Dixon-transverse relaxation (T2)-weighted imaging (T2WI) and SPAIR-T2WI, between 2020 and 2022. We compared the fat-suppression quality and artifacts, noise (N), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), signal intensity ratio (SIR) of extraocular muscles (SIR-EOM) and lacrimal glands (SIR-LG), and TAO activity evaluation efficiency.

Results

Dixon-T2WI showed a higher frequency of better subjective image quality and suitability for evaluating the characteristics of TAO lesions (65.7% vs. 14.3%) than SPAIR-T2WI. Fat-suppression quality and artifact scores were lower for Dixon-T2WI than for SPAIR-T2WI (p < 0.001). The N, SNR, and CNR values, EOM-SIR, and LG-SIR were higher for orbital coronal Dixon-T2WI than for SPAIR-T2WI (all p < 0.001). Clinical activity scores (CASs) showed positive correlations with SIR. The correlation between EOM-SIR and LG-SIR of orbital coronal Dixon-T2WI with CAS was higher than that of SPAIR-T2WI (0.590 vs. 0.493, all p < 0.001; 0.340 vs. 0.295, all p < 0.01). EOM-SIR and LG-SIR of Dixon-T2WI yielded a higher area under the curve than SPAIR-T2WI for evaluating TAO activity (0.865 vs. 0.760, p < 0.001; 0.695 vs. 0.617, p = 0.017).

Conclusion

Dixon-T2WI yields higher image quality than SPAIR-T2WI. Furthermore, it has a stronger ability to evaluate TAO inflammation than SPAIR, with higher sensitivity and specificity in active TAO staging.

Isorhamnetin Exerts Antifibrotic Effects by Attenuating Platelet-Derived Growth Factor-BB-induced HSC-T6 Cells Activation via Suppressing PI3K-AKT Signaling Pathway

Background

Currently, liver fibrosis is growing worldwide; unfortunately, there is no definite cure for this disease. Hence, understanding the molecular pathways involved in the development of liver fibrosis can help to find a proper treatment. In this study, we aimed to evaluate the effects of isorhamnetin as an antifibrotic agent on platelet-derived growth factor (PDGF)-BB-activated hepatic stellate cells (HSC)-T6 cells in a concentration-dependent manner. We have also attempted to assess signaling pathways that may affect liver fibrosis.

Methods

PDGF-BB was used to activate the HSC-T6 rat hepatic stellate cell line. The activated cells were treated with Isorhamnetin for 24 h. Finally, we compared the mRNA expression level of COLA1 and α-SMA and also the level of phosphorylated AKT protein with the control group.

Results

The obtained data revealed a significant increase in the expression level of the COLA1 and α-SMA genes (p > 0.05), as well as phosphorylated AKT protein, in the cells treated with PDGF-BB. In addition, 75 and 100 µM concentrations of Isorhamnetin markedly declined the COLA1 and α-SMA expression and also the phosphorylated AKT protein level in the HSC-T6 cells.

Conclusion

Our findings suggest that Isorhamnetin decreases HSC-T6 activation, the expression of COLA1 and α-SMA, in vitro, which could act as an antifibrotic element to reduce and treat liver fibrosis disease.

Isorhamnetin Exerts Antifibrotic Effects by Attenuating Platelet-Derived Growth Factor-BB-induced HSC-T6 Cells Activation via Suppressing PI3K-AKT Signaling Pathway

Background

Currently, liver fibrosis is growing worldwide; unfortunately, there is no definite cure for this disease. Hence, understanding the molecular pathways involved in the development of liver fibrosis can help to find a proper treatment. In this study, we aimed to evaluate the effects of isorhamnetin as an antifibrotic agent on platelet-derived growth factor (PDGF)-BB-activated hepatic stellate cells (HSC)-T6 cells in a concentration-dependent manner. We have also attempted to assess signaling pathways that may affect liver fibrosis.

Methods

PDGF-BB was used to activate the HSC-T6 rat hepatic stellate cell line. The activated cells were treated with Isorhamnetin for 24 h. Finally, we compared the mRNA expression level of COLA1 and α-SMA and also the level of phosphorylated AKT protein with the control group.

Results

The obtained data revealed a significant increase in the expression level of the COLA1 and α-SMA genes (p > 0.05), as well as phosphorylated AKT protein, in the cells treated with PDGF-BB. In addition, 75 and 100 µM concentrations of Isorhamnetin markedly declined the COLA1 and α-SMA expression and also the phosphorylated AKT protein level in the HSC-T6 cells.

Conclusion

Our findings suggest that Isorhamnetin decreases HSC-T6 activation, the expression of COLA1 and α-SMA, in vitro, which could act as an antifibrotic element to reduce and treat liver fibrosis disease.

Early Detection and Staging of Lung Fibrosis Enabled by Collagen-Targeted MRI Protein Contrast Agent

Chronic lung diseases, such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), are major leading causes of death worldwide and are generally associated with poor prognoses. The heterogeneous distribution of collagen, mainly type I collagen associated with excessive collagen deposition, plays a pivotal role in the progressive remodeling of the lung parenchyma to chronic exertional dyspnea for both IPF and COPD. To address the pressing need for noninvasive early diagnosis and drug treatment monitoring of pulmonary fibrosis, we report the development of human collagen-targeted protein MRI contrast agent (hProCA32.collagen) to specifically bind to collagen I overexpressed in multiple lung diseases. When compared to clinically approved Gd3+ contrast agents, hProCA32.collagen exhibits significantly better r1 and r2 relaxivity values, strong metal binding affinity and selectivity, and transmetalation resistance. Here, we report the robust detection of early and late-stage lung fibrosis with stage-dependent MRI signal-to-noise ratio (SNR) increase, with good sensitivity and specificity, using a progressive bleomycin-induced IPF mouse model. Spatial heterogeneous mapping of usual interstitial pneumonia (UIP) patterns with key features closely mimicking human IPF, including cystic clustering, honeycombing, and traction bronchiectasis, were noninvasively detected by multiple MR imaging techniques and verified by histological correlation. We further report the detection of fibrosis in the lung airway of an electronic cigarette-induced COPD mouse model, using hProCA32.collagen-enabled precision MRI (pMRI), and validated by histological analysis. The developed hProCA32.collagen is expected to have strong translational potential for the noninvasive detection and staging of lung diseases, and facilitating effective treatment to halt further chronic lung disease progression.

L-distance ratio: a new distance ratio-based evaluation method for the diagnosis of cirrhosis using enhanced computed tomography

Background

Early detection of liver cirrhosis is of great significance to the formulation of treatment plans and improving prognosis. Computed tomography (CT) is commonly used in the assessment of patients with chronic liver disease. In this study, we proposed a new distance ratio method for accurate diagnosis of cirrhosis using CT images.

Methods

This was a retrospective study of a consecutive series of patients in Guangdong Provincial People's Hospital. Sixty-two patients with pathologically diagnosed cirrhosis but whose morphologic changes were insufficient to diagnose cirrhosis were included in the cirrhosis group. Those who were pathologically confirmed to be free of cirrhosis and fibrosis and without a history of chronic hepatic were classified as the control group. A total of 124 patients underwent abdominal dynamic enhanced CT. Both the L-distance ratio-the ratio of the distance from the right portal vein bifurcation point to the anterior and posterior edges of the liver-and the caudate-right lobe ratio were measured by two independent radiologists. Intraclass correlation coefficients (ICCs) were used to assess the agreement between the radiologists. Binary logistic regression was performed for univariate analysis, and the odds ratio (OR) was also calculated. The discrimination ability of the two methods was evaluated by the area under the receiver operating characteristic curve (AUC).

Results

For both the L-distance ratio and the caudate-right lobe ratio, high agreement was observed between the two radiologists, although the ICC value of the L-distance ratio was slightly higher than that of the caudate-right lobe ratio (0.916 vs. 0.907). Binary logistic regression suggested that higher ratios were correlated with cirrhosis [the L-distance ratio, high vs. low OR =4.41, 95% confidence interval (CI): 2.08-9.36, P<0.001; the caudate-right lobe ratio, high vs. low OR =2.19, 95% CI: 1.07-4.49, P=0.031]. The AUCs of the L-distance ratio and the caudate-right lobe ratio were 0.823 (95% CI: 0.752-0.894) and 0.663 (95% CI: 0.569-0.757), respectively.

Conclusions

The L-distance ratio method proposed in this paper is more simple, accurate, and reliable than the caudate-right lobe ratio method in the diagnosis of cirrhosis.

Regulating Lymphatic Vasculature in Fibrosis: Understanding the Biology to Improve the Modeling

Fibrosis occurs in many chronic diseases with lymphatic vascular insufficiency (e.g., kidney disease, tumors, and lymphedema). New lymphatic capillary growth can be triggered by fibrosis-related tissue stiffening and soluble factors, but questions remain for how related biomechanical, biophysical, and biochemical cues affect lymphatic vascular growth and function. The current preclinical standard for studying lymphatics is animal modeling, but in vitro and in vivo outcomes often do not align. In vitro models can also be limited in their ability to separate vascular growth and function as individual outcomes, and fibrosis is not traditionally included in model design. Tissue engineering provides an opportunity to address in vitro limitations and mimic microenvironmental features that impact lymphatic vasculature. This review discusses fibrosis-related lymphatic vascular growth and function in disease and the current state of in vitro lymphatic vascular models while highlighting relevant knowledge gaps. Additional insights into the future of in vitro lymphatic vascular models demonstrate how prioritizing fibrosis alongside lymphatics will help capture the complexity and dynamics of lymphatics in disease. Overall, this review aims to emphasize that an advanced understanding of lymphatics within a fibrotic disease-enabled through more accurate preclinical modeling-will significantly impact therapeutic development toward restoring lymphatic vessel growth and function in patients.

Protective effect of acrocarpus fraxinifolius extract against hepatic fibrosis induced by Gamma irradiation and carbon tetrachloride in albino rats

PURPOSE

Liver fibrosis is considered as one of the ultimate outcomes of chronic liver disorders, characterized by outrageous cell proliferation and abnormal deposition of extracellular matrix, resulting in sever pathological distortions in the architecture and performance of liver tissues. The present study aimed to investigate the protective properties of aqueous methanol extract of Acrocarpus fraxinifolius leaves (AFL) against liver fibrosis induced by dual toxicity of γ-irradiation and carbon tetrachloride (CCl₄) in rats.

METHODS

The animals were exposed to 2 Gy irradiation once/week concurrently with intraperitoneal administration of CCl₄ (0.2 mL/100 g body weight) for seven weeks. Afterwards, liver toxicity and fibrosis were assessed biochemically at cellular and molecular as well as histopathological levels.

RESULTS

The livers of intoxicated rats showed distinct structural and functional changes, compared with the normal rats. The administration of AFL (500 mg/kg, p.o) significantly ameliorated the histopathological manifestations of fibrotic liver evidenced by mitigated steatosis progression, necrosis, fibrotic septa, apoptotic bodies, and immunochistochemical studies of alpha-smooth muscle actin. Also, AFL increased the final body weight, total protein, albumin levels and albumin/globulin ratio. While, the absolute liver weight, liver enzymes, total cholesterol and triglycerides were reduced. A significant modulation was observed in hydroxyproline, transforming growth factor-β and collagen-1expression. Furthermore, AFL exerted a direct effect on liver fibrosis by promoting extracellular matrix degradation via overexpression of the tissue inhibitor metalloproteinase-1, coupled with decease of metalloproteinase-9 activity.

CONCLUSIONS

Our findings suggested that AFL effectively improved the architecture of fibrotic liver and modified the biochemical markers of liver fibrosis.

Signaling Pathways and Potential Therapeutic Strategies in Cardiac Fibrosis

Cardiac fibrosis constitutes irreversible necrosis of the heart muscle as a consequence of different acute (myocardial infarction) or chronic (diabetes, hypertension, …) diseases but also due to genetic alterations or aging. Currently, there is no curative treatment that is able to prevent or attenuate this phenomenon that leads to progressive cardiac dysfunction and life-threatening outcomes. This review summarizes the different targets identified and the new strategies proposed to fight cardiac fibrosis. Future directions, including the use of exosomes or nanoparticles, will also be discussed.

A Water-Soluble AIEgen for Noninvasive Diagnosis of Kidney Fibrosis via SWIR Fluorescence and Photoacoustic Imaging

Early diagnosis of renal fibrosis is crucially significant on account of its worldwide prevalent tendency. Optical imaging in the near-infrared window has been recognized as an appealing technique for the timely detection of renal dysfunction. However, formulating a contrast agent that allows early monitoring of renal fibrosis and concurrently renally clearable in a normal group is still challenging. Herein, a nanosized fluorophore with aggregation-induced emission (AIE) features, namely AIE-4PEG550 NPs, is well-tailored and amenable to longitudinal visualization of the fibrosis progression specifically in the early-stage via short-wave infrared (SWIR, 900-1700 nm) fluorescence and photoacoustic bimodal imaging. The small size (≈26 nm), renally filtrable molecular weight (3.3 kDa), high renal clearance efficiency (93.1 ± 1.7% excretion through the kidneys within 24 h), outstanding imaging performance, and good biocompatibility, together make AIE-4PEG550 NPs remarkably impressive and far superior to clinical diagnostic assays. The finding in this study would provide a blueprint for the next generation of diagnostic agents for the extent of renal fibrosis.

Revealing stromal and lymphoid sources of Col3a1-expression during inflammation using a novel reporter mouse

One of the earliest signs of dysregulation of the homeostatic process of fibrosis, associated with pathology in chronic conditions such as rheumatoid arthritis, is the overexpression of collagen type III (COL-3). Critically, there is still relatively little known regarding the identity of the cell types expressing the gene encoding COL-3 (Col3a1). Identifying and characterizing Col3a1-expressing cells during the development of fibrosis could reveal new targets for the diagnosis and treatment of fibrosis-related pathologies. As such, a reporter mouse expressing concomitantly Col3a1 and mKate-2, a fluorescent protein, was generated. Using models of footpad inflammation, we demonstrated its effectiveness as a tool to measure the expression of COL-3 during the repair process and provided an initial characterization of some of the stromal and immune cells responsible for Col3a1 expression.

Advances and opportunities in nanoimaging agents for the diagnosis of inflammatory lung diseases

The development of rapid, noninvasive diagnostics to detect lung diseases is a great need after the COVID-2019 outbreak. The nanotechnology-based approach has improved imaging and facilitates the early diagnosis of inflammatory lung diseases. The multifunctional properties of nanoprobes enable better spatial-temporal resolution and a high signal-to-noise ratio in imaging. Targeted nanoimaging agents have been used to bind specific tissues in inflammatory lungs for early-stage diagnosis. However, nanobased imaging approaches for inflammatory lung diseases are still in their infancy. This review provides a solution-focused approach to exploring medical imaging technologies and nanoprobes for the detection of inflammatory lung diseases. Prospects for the development of contrast agents for lung disease detection are also discussed.

Diagnosis and monitoring of systemic sclerosis-associated interstitial lung disease using high-resolution computed tomography

Patients with systemic sclerosis are at high risk of developing systemic sclerosis-associated interstitial lung disease. Symptoms and outcomes of systemic sclerosis-associated interstitial lung disease range from subclinical lung involvement to respiratory failure and death. Early and accurate diagnosis of systemic sclerosis-associated interstitial lung disease is therefore important to enable appropriate intervention. The most sensitive and specific way to diagnose systemic sclerosis-associated interstitial lung disease is by high-resolution computed tomography, and experts recommend that high-resolution computed tomography should be performed in all patients with systemic sclerosis at the time of initial diagnosis. In addition to being an important screening and diagnostic tool, high-resolution computed tomography can be used to evaluate disease extent in systemic sclerosis-associated interstitial lung disease and may be helpful in assessing prognosis in some patients. Currently, there is no consensus with regards to frequency and scanning intervals in patients at risk of interstitial lung disease development and/or progression. However, expert guidance does suggest that frequency of screening using high-resolution computed tomography should be guided by risk of developing interstitial lung disease. Most experienced clinicians would not repeat high-resolution computed tomography more than once a year or every other year for the first few years unless symptoms arose. Several computed tomography techniques have been developed in recent years that are suitable for regular monitoring, including low-radiation protocols, which, together with other technologies, such as lung ultrasound and magnetic resonance imaging, may further assist in the evaluation and monitoring of patients with systemic sclerosis-associated interstitial lung disease. A video abstract to accompany this article is available at: https://www.globalmedcomms.com/respiratory/Khanna/HRCTinSScILD.

Cancer-associated fibroblasts: Origin, function, imaging, and therapeutic targeting

The tumor microenvironment (TME) is emerging as one of the primary barriers in cancer therapy. Cancer-associated fibroblasts (CAF) are a common inhabitant of the TME in several tumor types and play a critical role in tumor progression and drug resistance via different mechanisms such as desmoplasia, angiogenesis, immune modulation, and cancer metabolism. Due to their abundance and significance in pro-tumorigenic mechanisms, CAF are gaining attention as a diagnostic target as well as to improve the efficacy of cancer therapy by their modulation. In this review, we highlight existing imaging techniques that are used for the visualization of CAF and CAF-induced fibrosis and provide an overview of compounds that are known to modulate CAF activity. Subsequently, we also discuss CAF-targeted and CAF-modulating nanocarriers. Finally, our review addresses ongoing challenges and provides a glimpse into the prospects that can spearhead the transition of CAF-targeted therapies from opportunity to reality.

Visceral adipose volume is correlated with surgical tissue fibrosis in Crohn's disease of the small bowel

Background

This study explored the diagnostic performance of visceral adiposity to predict the degree of intestinal inflammation and fibrosis.

Methods

The patients with Crohn’s disease (CD) who underwent surgical small bowel resection at the First Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) between January 2007 and December 2017 were enrolled. We evaluated the intestinal imaging features of computed tomography enterography (CTE), including mesenteric inflammatory fat stranding, the target sign, mesenteric hypervascularity, bowel wall thickening, lymphadenopathy, stricture diameter, and maximal upstream diameter. We used A.K. software (Artificial Intelligence Kit, version 1.1) to calculate the visceral fat (VF) and subcutaneous fat (SF) volumes at the third lumbar vertebra level. Pathological tissue information was recorded. Diagnostic models were established based on the multivariate regression analysis results, and their effectiveness was evaluated by area under the curve (AUC) and decision curve analyses.

Results

Overall, 48 patients with CD were included in this study. The abdominal VF/SF volume ratio (odds ratio, 1.20; 95% confidence interval, 1.05–1.38; P = 0.009) and the stenosis diameter/upstream intestinal dilatation diameter (ND) ratio (odds ratio, 0.90; 95% confidence interval, 0.82–0.99; P = 0.034) were independent risk factors for the severe fibrosis of the small intestine. The AUC values of the VF/SF ratio, the ND ratio, and their combination were 0.760, 0.673, and 0.804, respectively. The combination of the VS/SF volume ratio and ND ratio achieved the highest net benefit on the decision curve.

Conclusion

The VF volume on CTE can reflect intestinal fibrosis. The combination of the VF/SF volume ratio and ND ratio of CD patients assessed using CTE can help predict severe fibrosis stenosis of the small intestine.

Reverse translation approach generates a signature of penetrating fibrosis in Crohn's disease that is associated with anti-TNF response

OBJECTIVE

Fibrosis is a common feature of Crohn's disease (CD) which can involve the mesenteric fat. However, the molecular signature of this process remains unclear. Our goal was to define the transcriptional signature of mesenteric fibrosis in CD subjects and to model mesenteric fibrosis in mice to improve our understanding of CD pathogenesis.

DESIGN

We performed histological and transcriptional analysis of fibrosis in CD samples. We modelled a CD-like fibrosis phenotype by performing repeated colonic biopsies in mice and analysed the model by histology, type I collagen-targeted positron emission tomography (PET) and global gene expression. We generated a gene set list of essential features of mesenteric fibrosis and compared it to mucosal biopsy datasets from inflammatory bowel disease patients to identify a refined gene set that correlated with clinical outcomes.

RESULTS

Mesenteric fibrosis in CD was interconnected to areas of fibrosis in all layers of the intestine, defined as penetrating fibrosis. We found a transcriptional signature of differentially expressed genes enriched in areas of the mesenteric fat of CD subjects with high levels of fibrosis. Mice subjected to repeated colonic biopsies showed penetrating fibrosis as shown by histology, PET imaging and transcriptional analysis. Finally, we composed a composite 24-gene set list that was linked to inflammatory fibroblasts and correlated with treatment response.

CONCLUSION

We linked histopathological and molecular features of CD penetrating fibrosis to a mouse model of repeated biopsy injuries. This experimental system provides an innovative approach for functional investigations of underlying profibrotic mechanisms and therapeutic concepts in CD.

Protective effects of Longhu Rendan on chronic liver injury and fibrosis in mice

Background and aim

Liver fibrosis resulting from persistent liver injury represents a major healthcare problem globally. Traditional Chinese medicine has played an essential role in the treatment of liver fibrosis in recent years. Thus, this study aims to assess the effect of Longhu Rendan (LHRD), a Chinese traditional patent medicine, on liver fibrosis and its potential mechanism.

Methods

The liver fibrosis in mice was induced via the intraperitoneal injection of carbon tetrachloride (CCl4) for 6 weeks or bile duct ligation for 15 days. Various methods were used to judge the therapeutic effect of LHRD.

Results

LHRD significantly suppressed the activity of serum index of abnormal liver function, liver cell apoptosis, and necrosis, attenuating liver injury. Moreover, LHRD treatment alleviated liver fibrotic features, such as the reduction of collagen deposition and hepatic stellate cell activation as well as profibrotic gene expression. Mechanistically, LHRD treatment inhibited nuclear transcription factor-kappa B signaling and inflammatory gene expression and diminished the production of reactive oxygen species and 4-hydroxynonenal, along with the downregulation of NADPH oxidase 4.

Conclusions

Overall, the present study demonstrates that LHRD ameliorates liver injury and fibrosis via the inhibition of inflammation and oxidative stress in mice, indicating that LHRD is a potential medicine for the treatment of liver fibrosis.

Heterogeneous Iron Oxide/Dysprosium Oxide Nanoparticles Target Liver for Precise Magnetic Resonance Imaging of Liver Fibrosis

Challenges remain in precisely diagnosing the progress of liver fibrosis in a noninvasive way. We here synthesized small (4 nm) heterogeneous iron oxide/dysprosium oxide nanoparticles (IO-DyO NPs) as a contrast agent (CA) for magnetic resonance imaging (MRI) to precisely diagnose liver fibrosis in vivo at both 7.0 and 9.4 T field strength. Our IO-DyO NPs can target the liver and show an increased T₂ relaxivity along with an increase of magnetic field strength. At a ultrahigh magnetic field, IO-DyO NPs can significantly improve spatial/temporal image resolution and signal-to-noise ratio of the liver and precisely distinguish the early and moderate liver fibrosis stages. Our IO-DyO NP-based MRI diagnosis can exactly match biopsy (a gold standard for liver fibrosis diagnosis in the clinic) but avoid the invasiveness of biopsy. Moreover, our IO-DyO NPs show satisfactory biosafety in vitro and in vivo. This work illustrates an advanced T₂ CA used in ultrahigh-field MRI (UHFMRI) for the precise diagnosis of liver fibrosis via a noninvasive means.

In Vivo and In Vitro Fibroblasts' Behavior and Capsular Formation in Correlation with Smooth and Textured Silicone Surfaces

BACKGROUND

As the most principal complication following breast augmentation with silicone breast implants, capsular contracture is greatly influenced by surface texture. However, there have long been widespread debates on the function of smooth or textured surface implants in reducing capsular contracture.

MATERIALS AND METHODS

Three commercially available silicone breast implants with smooth and textured surfaces were subjected to surface characterization, and in vitro and in vivo assessments were then implemented to investigate the effect of these different surfaces on the biological behaviors of fibroblasts and capsular formation in rat models.

RESULTS

Surface characterization demonstrated that all three samples were hydrophobic with distinct roughness values. Comparing the interactions of fibroblasts or tissues with different surfaces, we observed that as surface roughness increased, the adhesion and cell spreading of fibroblasts, the level of echogenicity, the density of collagen and α-SMA-positive immunoreactivity decreased, while the proliferation of fibroblasts and capsule thickness increased.

CONCLUSIONS

Our findings elucidated that the effect of silicone implant surface texture on fibroblasts' behaviors and capsular formation was associated with variations in surface roughness, and the number of myofibroblasts may have a more significant influence on the process of contracture than capsule thickness in the early stage of capsular formation. These results highlight that targeting myofibroblasts may be wielded in the prevention and treatment strategies of capsular contracture clinically.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

New Aspects of Kidney Fibrosis-From Mechanisms of Injury to Modulation of Disease

Organ fibrogenesis is characterized by a common pathophysiological final pathway independent of the underlying progressive disease of the respective organ. This makes it particularly suitable as a therapeutic target. The Transregional Collaborative Research Center “Organ Fibrosis: From Mechanisms of Injury to Modulation of Disease” (referred to as SFB/TRR57) was hosted from 2009 to 2021 by the Medical Faculties of RWTH Aachen University and the University of Bonn. This consortium had the ultimate goal of discovering new common but also different fibrosis pathways in the liver and kidneys. It finally successfully identified new mechanisms and established novel therapeutic approaches to interfere with hepatic and renal fibrosis. This review covers the consortium's key kidney-related findings, where three overarching questions were addressed: (i) What are new relevant mechanisms and signaling pathways triggering renal fibrosis? (ii) What are new immunological mechanisms, cells and molecules that contribute to renal fibrosis?, and finally (iii) How can renal fibrosis be modulated?

Quantitative T1 mapping MRI for the assessment of extraocular muscle fibrosis in thyroid-associated ophthalmopathy

PURPOSE

We aimed to investigate the performance of T1 mapping and its histological correlation with extraocular muscle fibrosis in thyroid-associated ophthalmopathy (TAO).

METHODS

We prospectively recruited 12 cases of active TAO, 12 cases of inactive TAO, and 15 cases of control subjects. All participants underwent magnetic resonance imaging (MRI) scan with pre-/postcontrast T1 mapping and short-time inversion-recovery (STIR) sequence. The images were analyzed to obtain precontrast T1, extracellular-volume (ECV) fraction on T1 mapping, and signal-intensity ratio (SIR) on STIR for each rectus. Muscle biopsy was performed at lateral rectus to quantify-collagen volume fraction, glycosaminoglycan (GAG)-volume fraction, and extracellular space component. The relationship between MRI and histopathology was examined with Pearson correlation coefficient.

RESULTS

The active TAO group was characterized with GAG accumulation, while the inactive TAO group presented with substantial fibrosis. The MRI parameters achieved acceptable interobserver and intraobserver agreement. The precontrast T1 and ECV remarkably increased in the TAO groups than the control group, and ECV positively correlated with collagen-volume fraction (r = 0.913) and extracellular-space component (r = 0.886) in the inactive TAO group. The SIR statistically increased in the active TAO group, and SIR positively correlated with GAG-volume fraction in all three groups. The performance of ECV (cutoff > 48.1%) to screen out extraocular muscle fibrosis in inactive TAO was 60.9% sensitivity and 93.3% specificity.

CONCLUSIONS

The ECV parameter on T1 mapping MRI is a reliable tool to quantify extraocular muscle fibrosis, providing insights into noninvasive evaluation of pathological changes in TAO orbit.

TRIAL REGISTRATION NUMBER

ChiCTR2000040394; Date of registration: 28 November 2020.

Fibrotic alterations in human annulus fibrosus correlate with progression of intervertebral disc herniation

BACKGROUND

Intervertebral disc (IVD) herniation is characterized by annulus fibrosus failure (AF) in containing the nucleus pulposus (NP). IVD herniation involves cellular and extracellular matrix (ECM) alterations that have been associated with tissue fibrosis, although still poorly investigated.

METHODS

Here, fibrotic alterations in human AF were evaluated, by characterizing the herniated ECM. Human AF samples (herniated lumbar IVD (n = 39, age 24-83) and scoliosis controls (n = 6, age 15-21)) were processed for transmission electron microscopy and histological/immunohistochemical analysis of fibrotic markers. Correlations between the fibrotic markers in AF ECM and the degree of NP containment (protused, contained and uncontained) and patients' age were conducted.

RESULTS

Our results demonstrate that with herniation progression, i.e. loss of NP containment, human AF presents less stained area of sulphated glycosaminoglycans and collagen I, being collagen I fibres thinner and disorganized. On the other hand, fibronectin stained area and percentage of α-smooth muscle actin+ cells increase in human AF, while matrix metalloproteinase-12 (MMP12) production and percentage of macrophages (CD68+ cells) remain constant. These structural and biochemical fibrotic alterations observed in human AF with herniation progression occur independently of the age.

CONCLUSIONS

The characterization of human AF here conducted evidence the presence of fibrosis in degenerated IVD, while highlighting the importance of considering the herniation progression stage, despite the patients' age, for a better understanding of the mechanisms behind AF failure and IVD herniation.

Liver Fibrosis-From Mechanisms of Injury to Modulation of Disease

The Transregional Collaborative Research Center "Organ Fibrosis: From Mechanisms of Injury to Modulation of Disease" (referred to as SFB/TRR57) was funded for 13 years (2009-2021) by the German Research Council (DFG). This consortium was hosted by the Medical Schools of the RWTH Aachen University and Bonn University in Germany. The SFB/TRR57 implemented combined basic and clinical research to achieve detailed knowledge in three selected key questions: (i) What are the relevant mechanisms and signal pathways required for initiating organ fibrosis? (ii) Which immunological mechanisms and molecules contribute to organ fibrosis? and (iii) How can organ fibrosis be modulated, e.g., by interventional strategies including imaging and pharmacological approaches? In this review we will summarize the liver-related key findings of this consortium gained within the last 12 years on these three aspects of liver fibrogenesis. We will highlight the role of cell death and cell cycle pathways as well as nutritional and iron-related mechanisms for liver fibrosis initiation. Moreover, we will define and characterize the major immune cell compartments relevant for liver fibrogenesis, and finally point to potential signaling pathways and pharmacological targets that turned out to be suitable to develop novel approaches for improved therapy and diagnosis of liver fibrosis. In summary, this review will provide a comprehensive overview about the knowledge on liver fibrogenesis and its potential therapy gained by the SFB/TRR57 consortium within the last decade. The kidney-related research results obtained by the same consortium are highlighted in an article published back-to-back in Frontiers in Medicine.

A Cross-Machine Comparison of Shear-Wave Speed Measurements Using 2D Shear-Wave Elastography in the Normal Female Breast

Quantitative measures of radiation-induced breast stiffness are required to support clinical studies of novel breast radiotherapy regimens and exploration of personalised therapy, however, variation between shear-wave elastography (SWE) machines may limit the usefulness of shear-wave speed (cs) for this purpose. Mean cs measured in four healthy volunteers’ breasts and a phantom using 2D-SWE machines Acuson S2000 (Siemens Medical Solutions) and Aixplorer (Supersonic Imagine) were compared. Shear-wave speed was measured in the skin region, subcutaneous adipose tissue and parenchyma. cs estimates were on average 2.3% greater when using the Aixplorer compared to S2000 in vitro. In vivo, cs estimates were on average 43.7%, 36.3% and 49.9% significantly greater (p << 0.01) when using the Aixplorer compared to S2000, for skin region, subcutaneous adipose tissue and parenchyma, respectively. In conclusion, despite relatively small differences between machines observed in vitro, large differences in absolute measures of shear wave speed measured were observed in vivo, which may prevent pooling of cross-machine data in clinical studies of the breast.

Non-invasive molecular imaging of kidney diseases

In nephrology, differential diagnosis or assessment of disease activity largely relies on the analysis of glomerular filtration rate, urinary sediment, proteinuria and tissue obtained through invasive kidney biopsies. However, currently available non-invasive functional parameters, and most serum and urine biomarkers, cannot capture intrarenal molecular disease processes specifically. Moreover, although histopathological analyses of kidney biopsy samples enable the visualization of pathological morphological and molecular alterations, they only provide information about a small part of the kidney and do not allow longitudinal monitoring. These limitations not only hinder understanding of the dynamics of specific disease processes in the kidney, but also limit the targeting of treatments to active phases of disease and the development of novel targeted therapies. Molecular imaging enables non-invasive and quantitative assessment of physiological or pathological processes by combining imaging technologies with specific molecular probes. Here, we discuss current preclinical and clinical molecular imaging approaches in nephrology. Non-invasive visualization of the kidneys through molecular imaging can be used to detect and longitudinally monitor disease activity and can therefore provide companion diagnostics to guide clinical trials, as well as the safe and effective use of drugs.