Radiation-induced Fibrosis Research Articles

Efferocytosis and enhanced FPR2 expression following apoptotic cell instillation attenuate radiation-induced lung inflammation and fibrosis

Lung inflammation and fibrosis are common side effects of radiotherapy that can lead to serious reduction in the quality of life of patients. However, no effective treatment is available, and the mechanisms underlying its pathophysiology are poorly understood. Irradiation increases formyl peptide receptor 2 (FPR2) expression in lung tissue, and FPR2 agonists are known to promote the uptake of apoptosis cells, referred to as efferocytosis that is a hallmark of the resolution of inflammation. Herein, in a mouse model of radiation-induced lung injury (RILI), efferocytosis was induced by injecting apoptotic cells into the lung through the trachea, and its correlation with FPR expression and the effect of efferocytosis and FPR expression on RILI were assessed. Interestingly, when apoptotic cells were injected into the lung, the radiation-induced increase in FPR2 expression was further amplified. In the mouse model of RILI, apoptotic cell instillation reduced the volume of the damaged lung and prevented the decrease in lung function. Additionally, the expression of inflammatory cytokines, fibrosis-related markers, and oxidative stress-related markers was reduced by apoptotic cell instillation. Co-administration of apoptotic Jurkat cells and WRW4, the FPR2 antagonist, reversed these effects. These findings suggest that efferocytosis induced by apoptotic cell instillation and enhanced FPR2 expression attenuate RILI, thereby alleviating lung inflammation and fibrosis.

Establishment of a radiation-induced vocal fold fibrosis mouse model

Post-radiation fibrosis of the vocal folds is thought to cause vocal impairment. However, the mechanism by which this occurs has been poorly documented, probably because of the lack of an appropriate experimental animal model. The purpose of this study was to establish a simple and reproducible mouse model of laryngeal radiation to investigate the development of vocal fold fibrosis over time. C57BL/6 mice individually placed in a lead shield were irradiated with a single dose of 20 Gy. At 1, 2, and 6 months after irradiation, larynges were harvested and subjected to histological examination and gene expression analysis. Irradiated vocal folds showed time-dependent tissue contraction and increased collagen deposition, with no significant difference in the changes in hyaluronic acid levels. Transcriptional analysis revealed upregulated expressions of TGF-β1 and iNOS at 6 months, but downregulated expressions of Acta2, Col1a1, Col3a1, and MMP8. Moreover, elevated TGF-β1 and reduced downstream gene expression levels indicated the existence of an inhibitory factor over the TGF-β/Smad pathway. Discrepancies in histological and transcriptional studies of collagen might suggest that radiation-induced vocal fold fibrosis could be caused by the elongated turnover of collagen. Overall, we established a mouse model of radiation-induced vocal fold fibrosis using a simple protocol. Further investigations are warranted to elucidate the pathogenesis of irradiation-induced fibrosis in vocal folds.

Quercetin-3-Rutinoside alleviates radiation-induced lung inflammation and fibrosis via regulation of NF-κB/TGF-β1 signaling

BackgroundRadiation exposure to lungs during nuclear catastrophes or radiotherapy poses long-term side effects and can induce pulmonary injury sufficient for causing death. The strategies for preventing or reversing radiation-induced lung injuries have not been yet developed. Quercetin-3-Rutinoside (Q-3-R), a polyphenolic bioflavonoid, has shown multifaceted pharmacological applications due to its high antioxidant and anti-inflammatory properties. PurposeIn the current study, the potential of Q-3-R against radiation-induced lung pneumonitis/fibrosis and the possible underlying mechanism was investigated. Study designTo evaluate the effect of Q-3-R against lung damage, C57Bl/6 mice were administered with Q-3-R (10 mg/kg b.wt.) and irradiated with a single dose of gamma radiation (12 Gy) at thoracic region. Methods16 weeks after irradiation lung damage was seen by histopathological studies and staining for collagen deposition. Expression of Nuclear factor kappa-B (NF-κB), transforming growth factor-β1 (TGF-β1), Smad3, intercellular adhesion molecule 1 (ICAM-1), α-smooth muscle actin protein (α-SMA), Aquaporin 5 (AQP 5), Interleukins (IL-6, IL-18, IL-1β), tumor necrosis factor-α (TNF-α) and caspase-3 was evaluated by immunohistochemistry/western blot/Elisa. Reactive oxygen species (ROS)/ Nitric oxide (NO) scavenging potential of Q-3-R and inhibition of cell death in irradiated lungs were also assessed. ResultsMice showed signs of pneumonitis and fibrotic changes in lungs following radiation treatment. A dramatic increase in inflammatory cells and cytokines contributing to lung disease pathogenesis was observed. Furthermore, expression of NF-κB, TGF-β1, Smad3, ICAM-1, AQP5and α-SMA was found markedly up-regulated. However, pretreatment of Q-3-R significantly attenuated radiation-induced pneumonitis and fibrosis. Histological examination revealed less structural and fibrotic changes with down-regulation of AQP 5, ICAM-1, α-SMA and caspase-3 in Q-3-R pretreated irradiated groups. The formulation significantly relieved lung injury by suppressing inflammatory and pro-fibrotic cytokines such as IL-6, IL-18, IL-1β, TNF-α and TGF-β1 via inhibition of NF-κB. Q-3-R also curtailed radiation-induced ROS/NO generation and minimized DNA damage in the irradiated lungs. ConclusionThe findings from the current study clearly demonstrate that Q-3-R provides radioprotection to the lungs by regulating NF-κB/TGF-β1 signaling, scavenging free radicals, preventing perivascular infiltration and prolonged inflammatory cascade which could otherwise lead to chronic radiation fibrosis. Q-3-R can be proved as a potential therapeutic agent for alleviating radiation-induced lung injury in case of planned or unplanned radiation exposure scenario.

ENAMPT Is a Novel Damage-associated Molecular Pattern Protein That Contributes to the Severity of Radiation-induced Lung Fibrosis.

The paucity of therapeutic strategies to reduce the severity of radiation-induced lung fibrosis (RILF), a life-threatening complication of intended or accidental ionizing radiation exposure, is a serious unmet need. We evaluated the contribution of eNAMPT (extracellular nicotinamide phosphoribosyltransferase), a damage-associated molecular pattern (DAMP) protein and TLR4 (Toll-like receptor 4) ligand, to the severity of whole-thorax lung irradiation (WTLI)-induced RILF. Wild-type (WT) and Nampt+/- heterozygous C57BL6 mice and nonhuman primates (NHPs, Macaca mulatta) were exposed to a single WTLI dose (9.8 or 10.7 Gy for NHPs, 20 Gy for mice). WT mice received IgG1 (control) or an eNAMPT-neutralizing polyclonal or monoclonal antibody (mAb) intraperitoneally 4 hours after WTLI and weekly thereafter. At 8-12 weeks after WTLI, NAMPT expression was assessed by immunohistochemistry, biochemistry, and plasma biomarker studies. RILF severity was determined by BAL protein/cells, hematoxylin and eosin, and trichrome blue staining and soluble collagen assays. RNA sequencing and bioinformatic analyses identified differentially expressed lung tissue genes/pathways. NAMPT lung tissue expression was increased in both WTLI-exposed WT mice and NHPs. Nampt+/- mice and eNAMPT polyclonal antibody/mAb-treated mice exhibited significantly attenuated WTLI-mediated lung fibrosis with reduced: 1) NAMPT and trichrome blue staining; 2) dysregulated lung tissue expression of smooth muscle actin, p-SMAD2/p-SMAD1/5/9, TGF-β, TSP1 (thrombospondin-1), NOX4, IL-1β, and NRF2; 3) plasma eNAMPT and IL-1β concentrations; and 4) soluble collagen. Multiple WTLI-induced dysregulated differentially expressed lung tissue genes/pathways with known tissue fibrosis involvement were each rectified in mice receiving eNAMPT mAbs.The eNAMPT/TLR4 inflammatory network is essentially involved in radiation pathobiology, with eNAMPT neutralization an effective therapeutic strategy to reduce RILF severity.

SAMiRNA Targeting Amphiregulin Alleviate Total-Body-Irradiation-Induced Renal Fibrosis.

Fibrosis is a serious unintended side effect of radiation therapy. In this study, we aimed to investigate whether amphiregulin (AREG) plays a critical role in fibrosis development after total-body irradiation (TBI). We found that the expression of AREG and fibrotic markers, such as α-smooth muscle actin (α-SMA) and collagen type I alpha 1 (COL1α1), was elevated in the kidneys of 6 Gy TBI mice. Expression of AREG and α-SMA was mainly elevated in the proximal and distal tubules of the kidney in response to TBI, which was confirmed by immunofluorescence staining. Knockdown of Areg mRNA using self-assembled-micelle inhibitory RNA (SAMiRNA) significantly reduced the expression of fibrotic markers, including α-SMA and COL1α1, and inflammatory regulators. Finally, intravenous injections of SAMiRNA targeting mouse Areg mRNA (SAMiRNA-mAREG) diminished radiation-induced collagen accumulation in the renal cortex and medulla. Taken together, the results of the present study suggest that blocking of AREG signaling via SAMiRNA-mAREG treatment could be a promising therapeutic approach to alleviate radiation-induced kidney fibrosis.

Interventions for Radiation-Induced Fibrosis in Patients With Breast Cancer: Systematic Review and Meta-analyses

PurposeRadiation therapy can affect normal tissues in patients with breast cancer, causing adverse effects such as fibrosis. Although there are several interventions for radiation-induced fibrosis, the efficacy of these procedures is still unclear. The purpose of this review is to evaluate the efficacy of interventions for radiation-induced fibrosis in patients with breast cancer. Methods and MaterialsThis is a systematic review of randomized clinical trials. Studies that compared any intervention for fibrosis to another intervention, placebo, or no intervention were included. Outcomes assessed were fibrosis, adverse events, quality of life, treatment adherence, pain, and functionality. ResultsA total of 2501 publications were found, and 7 studies were selected because they met the inclusion criteria. The interventions for fibrosis were pentoxifylline and vitamin E, grape seed extract, kinesiotherapy, and endermotherapy. The results showed great heterogeneity in the treatment protocols for radiation-induced fibrosis in patients with breast cancer and in their evaluation metrics. The meta-analyses showed no benefit in using pentoxifylline and vitamin E compared with placebo or no intervention (standardized mean difference: −0.30; 95% confidence interval, −0.79 to 0.20; P = .24 [very low evidence]) compared with placebo and vitamin E (standardized mean difference: −0.09; 95% confidence interval, −0.66 to 0.49; P = .77 [moderate evidence]), respectively, assessed by the Late Effects Normal Tissue Task Force–Subjective, Objective, Management, and Analytic (LENT-SOMA) scoring scale. ConclusionsThe effectiveness of these interventions for the treatment of radiation-induced fibrosis in patients with breast cancer could not be determined. Although isolated studies show significant results favorable to the experimental groups, caution should be exercised in these findings because of the small number, small sample size, and high risk of bias presented by some of the included studies, which makes the recommendation for clinical practice still weak.

Effect of Exercise on Sternoceleidomastoid Muscular Fibrosis after Radiotherapy for Nasopharyngeal Carcinoma Patients Analyzed by Shear-Wave Elastography

<sec><title>Objective</title> To evaluate the therapeutic effect of rehabilitation on sternoceleidomastoid muscular fibrosis after radiotherapy (RT) for nasopharyngeal carcinoma (NPC) patients by shear-wave elastography, and to provide a new clinical approach to solve radiation-induced muscular fibrosis. </sec><sec><title>Methods</title> A total of twenty NPC patients who had received radiotherapy for 1.5-5 years and rehabilitation therapy for three months were enrolled. Cervical spine range of movement (ROM), the thicknesses, widths and Youngs module values of sternoceleidomastoid muscles were assessed before and after treatment. </sec><sec><title>Results</title> The thickness of right and left sternoceleidomastoid muscles was significant different before and after treatment (<italic>P</italic><0.05). The widths of right and left sternoceleidomastoid muscles were significant different before and after treatment (<italic>P</italic><0.05). Compared with those before treatment, the Youngs module values of right and left sternoceleidomastoid muscles were significant different after treatment (<italic>P</italic><0.05). The left and right rotations and right flexion ROM of cervical spine were significant different before and after treatment (<italic>P</italic><0.05), while the left flexion, anteflexion and extension ROM of cervical spine were not significant different (<italic>P</italic>>0.05). </sec><sec><title>Conclusion</title> The Youngs module values of sternoceleidomastoid muscles for NPC patients decreased after rehabilitation, while the cervical spine ROM of left and right rotations and right flexion, as well as widths and thickness of sternoceleidomastoid muscles increased after rehabilitation. The shear-wave elastography is a feasible way to evaluate the effectiveness of radiation-induced muscular fibrosis rehabilitation for NPC patients. </sec>

Association of Radiation-induced CD4 and CD8 T-Lymphocyte Apoptosis with Radiation-induced Fibrosis after Breast Conserving Therapy

Background: Around 70% of early breast cancer patients choose breast conserving therapy (BCT), with equal overall and disease-free survival rates compared to mastectomy. As a result, treatment decisions are currently guided by cosmetic outcomes and quality of life (QoL). Unfortunately, 13.4% of all BCT patients are affected by a grade 2 of radiation-induced fibrosis (RIF) of the breast. The individual risk of RIF could be predicted based the reduced radiation-induced lymphocyte apoptosis (RILA).

Kinsenoside Protects Against Radiation-Induced Liver Fibrosis via Downregulating Connective Tissue Growth Factor Through TGF-β1 Signaling.

Radiation-induced liver fibrosis (RILF) is a serious complication of the radiotherapy of liver cancer, which lacks effective prevention and treatment measures. Kinsenoside (KD) is a monomeric glycoside isolated from Anoectochilus roxburghii, which has been reported to show protective effect on the early progression of liver fibrosis. However, the role of KD in affecting RILF remains unknown. Here, we found that KD alleviated RILF via downregulating connective tissue growth factor (CTGF) through TGF-β1 signaling. Sprague-Dawley rats were administered with 20 mg/kg KD per day for 8 weeks after a single 30Gy irradiation on the right part of liver, and tumor-bearing nude mice were administered with 30 mg/kg KD per day after a single fraction of 10Gy on the tumor inoculation site. Twenty-four weeks postirradiation, we found that the administration of KD after irradiation resulted in decreased expression of α-SMA and fibronectin in the liver tissue while had no adverse effect on the tumor radiotherapy. Besides, KD inhibited the activation of hepatic stellate cells (HSCs) postirradiation via targeting CTGF as indicated by the transcriptome sequencing. Results of the pathway enrichment and immunohistochemistry suggested that KD reduced the expression of TGF-β1 protein after radiotherapy, and exogenous TGF-β1 induced HSCs to produce α-SMA and other fibrosis-related proteins. The content of activated TGF-β1 in the supernatant decreased after treatment with KD. In addition, KD inhibited the expression of the fibrosis-related proteins by regulating the TGF-β1/Smad/CTGF pathway, resulting in the intervention of liver fibrosis. In conclusion, this study revealed that KD alleviated RILF through the regulation of TGFβ1/Smad/CTGF pathway with no side effects on the tumor therapy. KD, in combination with blocking the TGF-β1 pathway and CTGF molecule or not, may become the innovative and effective treatment for RILF.

A 3D Agent-Based Model of Lung Fibrosis

Understanding the pathophysiology of lung fibrosis is of paramount importance to elaborate targeted and effective therapies. As it onsets, the randomly accumulating extracellular matrix (ECM) breaks the symmetry of the branching lung structure. Interestingly, similar pathways have been reported for both idiopathic pulmonary fibrosis and radiation-induced lung fibrosis (RILF). Individuals suffering from the disease, the worldwide incidence of which is growing, have poor prognosis and a short mean survival time. In this context, mathematical and computational models have the potential to shed light on key underlying pathological mechanisms, shorten the time needed for clinical trials, parallelize hypotheses testing, and improve personalized drug development. Agent-based modeling (ABM) has proven to be a reliable and versatile simulation tool, whose features make it a good candidate for recapitulating emergent behaviors in heterogeneous systems, such as those found at multiple scales in the human body. In this paper, we detail the implementation of a 3D agent-based model of lung fibrosis using a novel simulation platform, namely, BioDynaMo, and prove that it can qualitatively and quantitatively reproduce published results. Furthermore, we provide additional insights on late-fibrosis patterns through ECM density distribution histograms. The model recapitulates key intercellular mechanisms, while cell numbers and types are embodied by alveolar segments that act as agents and are spatially arranged by a custom algorithm. Finally, our model may hold potential for future applications in the context of lung disorders, ranging from RILF (by implementing radiation-induced cell damage mechanisms) to COVID-19 and inflammatory diseases (such as asthma or chronic obstructive pulmonary disease).

FLT-PET/CT in Non-Small Cell Lung Cancer Treated With SBRT- A Pilot Study

<h3>Purpose/Objective(s)</h3> To prospectively assess the value of FLT-PET in differentiating tumor recurrence from radiation-induced lung fibrosis. The primary objective was to compare FLT uptake in three cohort of patients: 1) before SBRT, 2) stable lung fibrosis after SBRT, and 3) suspicious/proven local recurrence. The secondary objective was to optimize FLT PET imaging sequences for lung cancer patients and compare FLT uptake in 4D (respiratory sorted) versus free-breathing FLT-PET scans. <h3>Materials/Methods</h3> Early-stage (T1-2N0M0 or T3N0M0 limited to the chest wall as per 7^th edition American Joint committee on cancer staging manual) presumed or biopsy-proven non-small cell lung carcinoma, aged more than 18 years and planned for SBRT at the institution or followed up after SBRT with radiographic findings of fibrosis or recurrence were considered eligible for the study. Patients were assigned to one of three study cohorts. All patients underwent imaging with FLT PET CT- prior to SBRT in cohort 1 and at fibrosis or recurrence in cohort 2 and 3. The planned sample size was 20 patients in each cohort, 60 patients in total. The FLT PET SUV variables like SUV max, SUV mean, SUV2Dpeak, SUV3Dpeak, SUV 50 and SUV95 were compared between the three cohorts using Kruskal Wallis test. The correlation of 4D phased matched and 3D PET SUV variables was performed using spearman correlation coefficient. Statistical significance was set at p<0.05. <h3>Results</h3> Forty one patients were accrued in the study (20 in cohort 1, 16 in cohort 2 and 5 in cohort3). The median age of the entire cohort was 77 years (range 46-89). Majority were diagnosed with stage I lung cancer (86%) and 48Gy in 4 fractions was the most commonly used dose fractionation (59%). A 4D FLT PET was performed in 35 patients. There was no significant difference in the FLT uptake SUV variables between 4D (respiratory sorted) versus free-breathing scans (r=0.8-1). Using the 3D FLT PET information, SUV peak, SUV mean, SUV max were significantly lower in fibrosis cohort compared to recurrence and pretreatment cohorts (Table 1). The delayed FLT PET values SUV 50 and 95 values in recurrence cohort were significantly similar to pretreatment cohort and significantly different compared to fibrosis. <h3>Conclusion</h3> FLT PET may be helpful in differentiating SBRT related fibrosis from recurrence. This study was limited by the small sample size in recurrence cohort and larger validation studies are needed to ascertain utility of FLT PET to confirm the findings.

Quantitative Analysis of Literature on Radiation-Induced Fibrosis Based on CNKI Database

Objective To carried a bibliometric analysis of the related researches on radiation-induced fibrosis in China, and provide some theoretical support for the corresponding research in future clinical work. Methods Searching the literatures related to radiation-induced fibrosis published from the establishment of China journal full-text database to January 15, 2022 were searched, and conducting statistical analysis on the time, journals, institutions, authors, citations, keywords, and research content of their publications combined with Citespace. Results A total of 37 papers were included, of which the earliest was published in 2003; the papers were sourced from 29 journals and 44 institutions; 69 authors were included in the included papers; 3 were funded by funds, and the research content was mainly about radiation pulmonary fibrosis, ionizing radiation, epithelial-mesenchymal transition (emt), etc. Conclusion At present, there are few studies on radiation-induced fibrosis in our country, and the distribution of research journals is relatively scattered. But it is closely related to ionizing radiation and cells, and it is unknown whether it may become an emerging research hotspot. At present, more evidence-based medical exploration is needed.

Radiation-Induced Fibrosis in Patients with Head and Neck Cancer: A Review of Pathogenesis and Clinical Outcomes.

Radiotherapy-related fibrosis remains one of the most challenging treatment related side effects encountered by patients with head and neck cancer. Several established and ongoing novel therapies have been studied with paucity of data in how to best treat these patients. This review aims to provide researchers and health care providers with a comprehensive review on the presentation, etiology, and therapeutic options for this serious condition.

Targeting senescence-like fibroblasts radiosensitizes non-small cell lung cancer and reduces radiation-induced pulmonary fibrosis.

Cancer cell radioresistance is the primary cause of the decreased curability of non–small cell lung cancer (NSCLC) observed in patients receiving definitive radiotherapy (RT). Following RT, a set of microenvironmental stress responses is triggered, including cell senescence. However, cell senescence is often ignored in designing effective strategies to resolve cancer cell radioresistance. Herein, we identify the senescence-like characteristics of cancer-associated fibroblasts (CAFs) after RT and clarify the formidable ability of senescence-like CAFs in promoting NSCLC cell proliferation and radioresistance through the JAK/STAT pathway. Specific induction of senescence-like CAF apoptosis using FOXO4-DRI, a FOXO4-p53–interfering peptide, resulted in remarkable effects on radiosensitizing NSCLC cells in vitro and in vivo. In addition, in this study, we also uncovered an obvious therapeutic effect of FOXO4-DRI on alleviating radiation-induced pulmonary fibrosis (RIPF) by targeting senescence-like fibroblasts in vivo. In conclusion, by targeting senescence, we offer a strategy that simultaneously decreases radioresistance of NSCLC and the incidence of RIPF.

Late cardiac toxicity of neo-adjuvant chemoradiation in esophageal cancer survivors: A prospective cross-sectional pilot study

PurposeAlthough cure rates in esophageal cancer (EC) have improved since the introduction of neoadjuvant chemoradiation (nCRT), evidence for treatment-related cardiac toxicity is growing, of which the exact mechanisms remain unknown. The primary objective of this study was to identify (subclinical) cardiac dysfunction in EC patients after nCRT followed by surgical resection as compared to surgery alone. Materials and MethodsEC survivors followed for 5–15 years after curative resection with (n = 20) or without (n = 20) nCRT were enrolled in this prospective cross-sectional pilot study. All patients underwent several clinical and diagnostic tests in order to objectify (sub)clinical cardiac toxicity including cardiac CT and MRI, echocardiography, ECG, 6-minutes walking test, physical examination and EORTC questionnaires. ResultsWe found an increased rate of myocardial fibrosis (Linear late gadolinium enhancement (LGE) 4 vs. 1; p = 0.13; mean extracellular volume (ECV) 28.4 vs. 24.0; p < 0.01), atrial fibrillation (AF) (6 vs. 2; p = 0.07) and conduction changes in ECG among patients treated with nCRT as compared to those treated with surgery alone. The results suggested an impact on quality of life in terms of worse role functioning for this patient group (95.0 vs. 88.8; p = 0.03). ConclusionBased on our analyses we hypothesize that in EC patients, radiation-induced myocardial fibrosis plays a central role in cardiac toxicity leading to AF, conduction changes and ultimately to decreased role functioning. The results emphasize the need to verify these findings in larger cohorts of patients.

TGF-beta signaling in cancer radiotherapy

Transforming growth factor beta (TGF-β) plays key roles in regulating cellular proliferation and maintaining tissue homeostasis. TGF-β exerts tumor-suppressive effects in the early stages of carcinogenesis, but it also plays tumor-promoting roles in established tumors. Additionally, it plays a critical role in cancer radiotherapy. TGF-β expression or activation increases in irradiated tissues, and studies have shown that TGF-β plays dual roles in cancer radiosensitivity and is involved in ionizing radiation-induced fibrosis in different tumor microenvironments (TMEs). Furthermore, TGF-β promotes radioresistance by inducing the epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and cancer-associated fibroblasts (CAFs), suppresses the immune system and facilitates cancer resistance. In particular, the links between TGF-β and the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) axis play a critical role in cancer therapeutic resistance. Growing evidence has shown that TGF-β acts as a radiation protection agent, leading to heightened interest in using TGF-β as a therapeutic target. The future of anti-TGF-β signaling therapy for numerous diseases appears bright, and the outlook for the use of TGF-β inhibitors in cancer radiotherapy as TME-targeting agents is promising.

Feasibility study for inducing the skeletal muscle fibrosis via irradiation using two mouse strains.

Although the mechanism of onset and progression of radiation-induced fibrosis (RIF) has been studied, most studies to date have focused on pulmonary fibrosis. There are few studies on murine RIF in the skeletal muscle, and the pathogenic mechanism remains unclear. This pilot study aimed to evaluate the feasibility to create a murine model of RIF in the skeletal muscle and analyze strain differences in fibrosis sensitivity. Two mouse strains, C57BL/6 and C3H/He, were used. Their right hind limbs were irradiated at a dose of 25Gy once a week for three fractions. Gastrocnemius muscles were collected at day 4, and weeks 2, 4, 8, 12, and 24 after the third irradiation and subjected to histopathological examination and immunoblotting. In C57BL/6 mice, chronic inflammation and an increased expression of transforming growth factor-β (TGF-β) and fibronectin were observed 2weeks after irradiation. A significant increase in fibrosis was detected after 8weeks. However, in C3H/He mice, the expression of TGF-β and fibronectin increased 8weeks after irradiation, and fibrosis significantly increased after 12weeks. Moreover, the degrees of inflammation and fibrosis were more remarkable in C57BL/6 mice than in C3H/He mice. The onset and degree of fibrosis may be associated with the expression of TGF-β and fibronectin, and inflammation, in a strain-specific manner. Therefore, a murine model of RIF in the skeletal muscle could be created using the indicated method, suggesting that the C57BL/6 strain is more sensitive to fibrosis in the skeletal muscle, as well as the lung, than the C3H/He strain. Radiation-induced fibrosis in the skeletal muscle could be detected in C57BL/6 and C3H/He mice, with C57BL/6 mice being more sensitive to fibrosis in the skeletal muscle than C3H/He mice.

Connective-Tissue Growth Factor Contributes to TGF-β1-induced Lung Fibrosis.

Idiopathic pulmonary fibrosis is a fatal lung disease characterized by progressive and excessive accumulation of myofibroblasts and in the lung. Connective-tissue growth factor (CTGF) exacerbates pulmonary fibrosis in radiation-induced lung fibrosis, and in this study, we demonstrate upregulation of CTGF in a rat lung fibrosis model induced by an adenovirus vector encoding active TGF-β1 (AdTGF-β1). We show that CTGF is also upregulated in patients with idiopathic pulmonary fibrosis. Expression of CTGF was upregulated in vascular smooth muscle cells cultured from fibrotic lungs on Days 7 and 14 as well as endothelial cells sorted from fibrotic lungs on Days 14 and 28. These findings suggest contributions of different cells in maintaining the fibrotic phenotype during fibrogenesis. Treatment of fibroblasts with recombinant CTGF along with TGF-β increases profibrotic markers in fibroblasts, confirming the synergistic effect of recombinant CTGF with TGF-β in inducing pulmonary fibrosis. Also, the fibrotic extracellular matrix upregulated CTGF expression, compared with the normal extracellular matrix, suggesting that not only profibrotic mediators but also a profibrotic environment contributes to fibrogenesis. We also showed that pamrevlumab, a CTGF inhibitory antibody, partially attenuates fibrosis in the model. These results suggest that pamrevlumab could be an option for treatment of pulmonary fibrosis.

Abstract 9889: Novel Mechanisms of Cardiac Macrophage-Mast Cell Interactions in Radiation-Induced Myocardial Fibrosis

Introduction: Both galectin-3 (gal3) and macrophages are implicated in myocardial fibrotic remodeling. Macrophages express gal3 on their surface, whereas mast cells express a high-affinity gal3 receptor, FcεRI. Understanding the mechanisms of their interactions will lead to highly targeted therapeutic approaches. Hypothesis: We hypothesize that a macrophage-expressed pro-fibrotic molecule, gal3, is a mediator of macrophage-mast cell interactions in a pre-clinical model of radiation-induced myocardial fibrosis. Methods: We studied myocardial fibrosis, cardiac macrophage-mast cell infiltration, and gal3 expression in a rodent model of thoracic radiation. We performed long-term culture of the bone-marrow cells isolated from gal3 KO (gal3 -/- ) and gal3 overexpression (gal3 +/+ ) mice. Recombinant M-CSF co-cultured cells transformed to macrophages (F4/80 + /CD11B + ), whereas IL-3-treated cells transformed to mast cells (FCεR1 + /c-kit + ). Then, we used microfluidic and transwell systems to examine the gal3-dependent macrophage-mast cell interactions in the live cell culture. Results: Thoracic radiation exposure induced myocardial fibrosis (% fibrosis, radiation: 5±2, controls: 2±0.6; p=0.01, N=5-8), which was also associated with macrophage (cells/cm 3 , radiation: 114±28, controls: 81±0.3; p=0.05, N=8) and mast cell (cells/cm 3 , radiation: 14±5, controls: 9±0.3; p=0.05, N=5-8) infiltration, and cardiac gal3 expression (pg/ng, radiation: 85±15, controls: 14±8; p=0.001, N=7). Exogenous gal3 treatment led to increased mast cell tryptase activity confirming their activation [tryptase (ng/ml), untreated: 291±46, gal3: 494±191; p&lt;0.01, N=3-8]. Quantitative macrophage-mast cell activity in a microfluidic system showed 7.5-fold increased macrophage-mast cell adhesion in gal3 +/+ cells suggesting increased interactions with gal3 overexpression [cell adhesion (cells/mm 2 ), WT: 23±5.8, Gal3 +/+ :175±38; p&lt;0.01, N=4]. Conclusion: In a pre-clinical model of radiation-induced myocardial fibrosis, gal3 can mediate crucial macrophage-mast cell interactions. Our data provide possible mechanistic evidence of gal3 involvement in macrophage-mast cell interactions en route to myocardial fibrosis after radiation exposure.

Abstract 9422: Assessment of Cardiotoxicity Following Thoracic Radiotherapy and Systemic Stem-Cell Derived Extracellular Vesicle Treatments

Introduction: Radiotherapeutic management of certain cancers provides distinct benefits, but also results in variable degrees of cardiac exposure. Resultant radiation-induced heart disease (RIHD) typically manifests at protracted post-irradiation times and can involve a wide range of underlying pathologies including heart failure. Past work from our lab has identified an intervention involving systemic administration of human embryonic stem cell (hESC) derived extracellular vesicles (EV) shown to resolve radiation-induced lung disease (RILD). However, potential treatment-associated complications to the heart were not investigated. Hypothesis: In this study, we hypothesized that 1) radiation would cause a certain level of heart dysfunction, and 2) that stem cell-derived EV would not further confound RIHD. Methods: Separate cohorts of control (no radiation +/- EV) and treated (radiation +/- EV) mice were implemented in this study. For the treatment groups, mice were subjected to a single dose of image guided thoracic irradiation (14 Gy) and then systemically injected with hESC-derived EV at different time points. Echocardiography was performed in 4 cohorts (n=46); control arm (n=9), radiation alone arm (n=24), EV alone arm (no radiation) (n=5) and toxicity control arm involving 4 EV doses at weeks 0, 1, 2, 3) (n=8). The following parameters were compared between the 4 cohorts: E/A ratio, ejection fraction (EF), shortening fraction (SF), left ventricular mass (LV mass), end diastolic volume (EDV). Results: Radiation caused statistically significant lower E/A ratios compared with mice that did not receive radiation, with non-significant changes in other key indicators of cardiac function. Importantly, EV treatments had no effect on E/A ratio or any other indices of cardiac function among the different cohorts. Conclusions: Irradiated mice had lower E/A ratios but EF was unchanged, suggesting that thoracic exposures compromised diastolic function without impacting EF. Diastolic dysfunction was most likely linked to increased radiation-induced fibrosis and myocardium stiffness. Importantly, EV treatments were not observed to adversely impact cardiac function, pointing to the safety of this potential intervention for RILD.