Scarring Response Research Articles

ECM Stiffness Controls the Activation and Contractility of Corneal Keratocytes in Response to TGF-β1

After surgery or traumatic injury, corneal wound healing can cause a scarring response that stiffens the tissue and impairs ocular function. This fibrosis is caused in part by the activation of corneal keratocytes from a native mechanically quiescent state to an activated myofibroblastic state. This transformation is tied to signaling downstream of transforming growth factor-β1 (TGF-β1). Here, to better understand how biochemical and biophysical cues interact to regulate keratocyte activation and contractility, we cultured primary rabbit corneal keratocytes on flexible substrata of varying stiffness in the presence (or absence) of TGF-β1. Time-lapse fluorescence microscopy was used to assess changes in keratocyte morphology, as well as to quantify the dynamic traction stresses exerted by cells under different experimental conditions. In other experiments, keratocytes were fixed after 5 days of culture and stained for markers of both contractility and myofibroblastic activation. Treatment with TGF-β1 elicited distinct phenotypes on substrata of different stiffnesses. Cells on soft (1 kPa) gels formed fewer stress fibers and retained a more dendritic morphology, indicative of a quiescent keratocyte phenotype. Keratocytes cultured on stiff (10 kPa) gels or collagen-coated glass coverslips, however, had broad morphologies, formed abundant stress fibers, exhibited greater levels of α-smooth muscle actin (α-SMA) expression, and exerted larger traction forces. Confocal images of phospho-myosin light chain (pMLC) immunofluorescence, moreover, revealed stiffness-dependent differences in the subcellular distribution of actomyosin contractility, with pMLC localized at the tips of thin cellular processes in mechanically quiescent cells. Importantly, keratocytes cultured in the absence of TGF-β1 showed no stiffness-dependent differences in α-SMA immunofluorescence, suggesting that a stiff microenvironment alone is insufficient to induce myofibroblastic activation. Taken together, these data suggest that changes in ECM stiffness can modulate the morphology, cytoskeletal organization, and subcellular pattern of force generation in corneal keratocytes treated with TGF-β1.

Structural mechanics modeling reveals stress-adaptive features of cutaneous scars.

The scar is a predominant outcome of adult mammalian wound healing despite being associated with partial function loss. Here in this paper, we have described the structure of a full-thickness normal scar as a "di-fork" with dual biomechanical compartments using in vivo and ex vivo experiments. We used structural mechanics simulations to model the deformation fields computationally and stress distribution in the scar in response to external forces. Despite its loss of tissue components, we have found that the scar has stress-adaptive features that cushion the underlying tissues from external mechanical impacts. Thus, this new finding can motivate research to understand the biomechanical advantages of a scar in maintaining the primary function of the skin, i.e., mechanical barrier despite permanent loss of some tissues and specialized functions.

Promoting 3D neuronal differentiation in hydrogel for spinal cord regeneration

Spinal cord injury (SCI) affects millions of people worldwide, and results in the loss of neurons and limited recovery of functions. Bone mesenchymal stem cells (BMSCs) and neural stem cells (NSCs) can proliferate or differentiate into other specific cell types. These cells represent potential treatments for SCIs. However, recent studies have shown that NSCs mainly differentiate into astrocytes, rather than neurons, in the microenvironment of an SCI. BMSCs have been reported to promote neuronal differentiation of NSCs and reduce the formation of astrocytes. Furthermore, three-dimensional (3D) gelatin methacryloyl (GelMA) provides superior mechanical properties and functional characteristics for cell proliferation, migration, and differentiation. In this study, we proposed a functional scaffold developed by loading BMSCs and NSCs into 3D GelMA hydrogel. BMSCs and NSCs that were photo-encapsulated in the 3D GelMA hydrogel survived and demonstrated good proliferation in vitro. The NSCs differentiated more toward neurons and oligodendrocytes than toward astrocytes, a phenomenon more noticeable in low-modulus hydrogels. When functional hydrogel scaffolds, loaded with BMSCs and NSCs, were implanted into the hemisection site of the rat spinal cord, they could significantly promote motor function recovery and neuronal differentiation, and decrease glial scarring, fibrotic scarring, and inflammatory responses. The immense therapeutic potential of this system to promote axonal regeneration was thereby demonstrated. Taken together, loading of the GelMA scaffold with BMSCs and NSCs is a promising therapeutic strategy to trigger functional regeneration of the spinal cord.

Peyronie’s disease: Contemporary evaluation and management

Peyronie's disease is a common yet poorly understood condition characterized by penile pain, curvature, sexual dysfunction and psychological bother. Peyronie's disease represents a penile wound healing disorder, and is thought to arise from exuberant scarring in response to penile trauma in genetically predisposed men. In the absence of active treatment, the majority of men experience stable or worsening symptoms, with few reporting spontaneous resolution in penile curvature or other deformity. In contrast, penile pain improves or resolves in the majority of men. Treatment options vary based on symptom severity and stability. Several oral therapies are commonly prescribed, although to date there are no strong data to support any oral agents as monotherapy for Peyronie's disease. Other options including penile traction therapy and intralesional injections result in modest improvements for many patients, particularly when used early after symptom onset. Penile straightening through approaches, such as penile plication and plaque incision or partial excision and grafting, represent the most rapid and reliable approach to correct penile curvature once the symptoms have stabilized. Side-effects vary based on the type of surgery carried out, and include penile shortening, sensation changes and erectile dysfunction in the minority of men. In patients with drug refractory erectile dysfunction and Peyronie's disease, placement of a penile prosthesis will address both issues, and is associated with high levels of patient satisfaction. The current review provides a practical approach to the modern evaluation and management of patients presenting with Peyronie's disease.

Contemporary management of refractory pediatric glaucoma

The management of pediatric glaucoma poses a unique challenge in terms of maintaining lifelong vision and combating an aggressive scarring response from surgery. Contemporary literature regarding the surgical management of children with pediatric glaucoma who fail, or are at a high risk of failure, from conventional surgery is limited. The aim of this review is to highlight recent developments in relation to the current opinion regarding the management of children with refractory pediatric glaucoma. Some studies have reported impressive success rates with circumferential trabeculotomy, even in eyes with previous failed surgery. Early results of deep sclerectomy in populations which may not respond well to conventional angle surgery are encouraging but data is limited for the pediatric age group. In compliant patients in whom multiple postoperative examinations under anesthesia are possible, trabeculectomy remains an effective procedure. Multiple recent studies have demonstrated that glaucoma drainage device (GDD) surgery is associated with 5-year success rates of over 70% in primary childhood glaucomas. Glaucoma drainage device surgery is likely to remain a mainstay of surgical management for refractory glaucoma in older children. More prospective data are needed on the success of circumferential trabeculotomy, deep sclerectomy and micropulse laser in pediatric eyes with previous failed surgery. VIDEO ABSTRACT: http://links.lww.com/COOP/A34.

CPEB1 or CPEB4 knockdown suppresses the TAK1 and Smad signalings in THP-1 macrophage-like cells and dermal fibroblasts

Post-burn hypertrophic scar (HTS) is a form of excessive dermal fibrosis characterized by cutaneous scarring, which is common in patients following burn injury. Moreover, at least 50% of HTS are accompanied by inflammation. Cytoplasmic polyadenylation element binding (CPEB) proteins are key mRNA-binding proteins that control the translation of several mRNAs. However, their potential roles in treating dermal fibrosis and scarring remain unknown. Therefore, in this study, we aimed to investigate the effects of small interfering RNA (siRNA)-mediated knockdown of CPEB1 or CPEB4 in human THP-1 macrophages and dermal fibroblasts treated with LPS and TGF-β1. We found significantly increased CPEB1 and CPEB4 mRNA and protein levels in LPS-treated THP-1 cells and TGF-β1–treated fibroblasts. CPEB1 and CPEB4 knockdowns suppressed LPS-activated TAK1 signaling cascades by reducing the levels of TNF-α and phosphorylated TAK1, p38, ERK, JNK, and NF-κB-p65 in THP-1 cells. CPEB1 and CPEB4 knockdowns also attenuated TGF-β1-activated Smad-dependent and -independent signaling cascades by reducing the levels of TAK1, p38, ERK, JNK, and phosphorylated Smad 2 and Smad 1/5/8 in fibroblasts. Furthermore, CPEB1 or CPEB4 knockdown markedly decreased the levels of fibrosis markers, including α-SMA, type I collagen, and fibronectin in fibroblasts. Our findings indicate that CPEB1 and CPEB4 are involved in the regulation of the TAK1 and Smad signalings in human macrophages and dermal fibroblasts. These activities may play a role in cutaneous scarring responses.

Specific macrophage populations promote both cardiac scar deposition and subsequent resolution in adult zebrafish.

AimsA robust inflammatory response to tissue injury is a necessary part of the repair process but the deposition of scar tissue is a direct downstream consequence of this response in many tissues including the heart. Adult zebrafish not only possess the capacity to regenerate lost cardiomyocytes but also to remodel and resolve an extracellular scar within tissues such as the heart, but this scar resolution process remains poorly understood. This study aims to characterize the scarring and inflammatory responses to cardiac damage in adult zebrafish in full and investigate the role of different inflammatory subsets specifically in scarring and scar removal.Methods and resultsUsing stable transgenic lines, whole organ imaging and genetic and pharmacological interventions, we demonstrate that multiple inflammatory cell lineages respond to cardiac injury in adult zebrafish. In particular, macrophage subsets (tnfα+ and tnfα−) play prominent roles with manipulation of different phenotypes suggesting that pro-inflammatory (tnfα+) macrophages promote scar deposition following cardiac injury whereas tnfα− macrophages facilitate scar removal during regeneration. Detailed analysis of these specific macrophage subsets reveals crucial roles for Csf1ra in promoting pro-inflammatory macrophage-mediated scar deposition. Additionally, the multifunctional cytokine Osteopontin (Opn) (spp1) is important for initial scar deposition but also for resolution of the inflammatory response and in late-stage ventricular collagen remodelling.ConclusionsThis study demonstrates the importance of a correctly balanced inflammatory response to facilitate scar deposition during repair but also to allow subsequent scar resolution, and full cardiac regeneration, to occur. We have identified Opn as having both pro-fibrotic but also potentially pro-regenerative roles in the adult zebrafish heart, driving Collagen deposition but also controlling inflammatory cell resolution.

African Spiny Mice as a Comparative Model of Spinal Cord Injury Repair and Recovery

The adult mammalian central nervous system does not regeneration after injury. Spinal cord injury (SCI) results in a complex cascade of secondary damage responses that can exacerbate the initial injury or facilitate recovery. While inflammatory and fibrotic responses are known to be key regulators in promoting or repressing SCI repair, our understanding of their exact role in spinal regeneration is still evolving. While a mammalian model of enhanced regeneration would be invaluable for SCI studies, none currently exist. Translating therapies from non‐mammalian models that demonstrate spinal cord regeneration to mammals is complicated by a host of interspecific physiological differences. African spiny mice (genus Acomys) are a unique group of rodents that can regenerate full‐thickness skin, musculoskeletal tissue in the ear pinna, and recover from severe kidney injury. Multi‐organ tissue regeneration occurs coincident with inflammatory and scarring responses that are distinct from those of the non‐regenerating laboratory mouse (genus Mus). However, there are no published studies of Acomys regenerative capacity in the spinal cord. The objective of this study was to evaluate the potential of Acomys as a mammalian model of enhanced repair/recovery following spinal cord injury. Through histological analysis of uninjured tissue, we found that Acomys and Mus have similar gross neuroanatomical spinal structures. After SCI, motor and sensory functional tests revealed distinct functional recovery profiles between Acomys and Mus. Ongoing cellular studies of injured spinal tissue are investigating the macrophage and extracellular matrix profiles, which we predict to differ based on inflammatory and scarring responses to peripheral injuries. These preliminary data suggest that while Acomys and Mus have similar baseline spinal anatomy, the physiological response to injury is distinct and may provide insight to critical features leading mammalian SCI recovery and regeneration.Support or Funding Information5T32 NS077889This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Mouse mast cell protease 4 suppresses scar formation after traumatic spinal cord injury

Spinal cord injury (SCI) triggers the formation of a glial and fibrotic scar, which creates a major barrier for neuroregenerative processes. Previous findings indicate that mast cells (MCs) protect the spinal cord after mechanical damage by suppressing detrimental inflammatory processes via mouse mast cell protease 4 (mMCP4), a MC-specific chymase. In addition to these immunomodulatory properties, mMCP4 also plays an important role in tissue remodeling and extracellular matrix degradation. Therefore, we have investigated the effects of mMCP4 on the scarring response after SCI. We demonstrate that the decrease in locomotor performance in mMCP4−/− mice is correlated with excessive scar formation at the lesion. The expression of axon-growth inhibitory chondroitin sulfate proteoglycans was dramatically increased in the perilesional area in mMCP4−/− mice compared to wild type mice. Moreover, the fibronectin-, laminin-, and collagen IV-positive scar was significantly enlarged in mMCP4−/− mice at the lesion center. A degradation assay revealed that mMCP4 directly cleaves collagen IV in vitro. On the gene expression level, neurocan and GFAP were significantly higher in the mMCP4−/− group at day 2 and day 28 after injury respectively. In contrast, the expression of fibronectin and collagen IV was reduced in mMCP4−/− mice compared to WT mice at day 7 after SCI. In conclusion, our data show that mMCP4 modulates scar development after SCI by altering the gene and protein expression patterns of key scar factors in vivo. Therefore, we suggest a new mechanism via which endogenous mMCP4 can improve recovery after SCI.

Recent Progress on Non-Conventional Microfabricated Probes for the Chronic Recording of Cortical Neural Activity.

Microfabrication technology for cortical interfaces has advanced rapidly over the past few decades for electrophysiological studies and neuroprosthetic devices offering the precise recording and stimulation of neural activity in the cortex. While various cortical microelectrode arrays have been extensively and successfully demonstrated in animal and clinical studies, there remains room for further improvement of the probe structure, materials, and fabrication technology, particularly for high-fidelity recording in chronic implantation. A variety of non-conventional probes featuring unique characteristics in their designs, materials and fabrication methods have been proposed to address the limitations of the conventional standard shank-type (“Utah-” or “Michigan-” type) devices. Such non-conventional probes include multi-sided arrays to avoid shielding and increase recording volumes, mesh- or thread-like arrays for minimized glial scarring and immune response, tube-type or cylindrical probes for three-dimensional (3D) recording and multi-modality, folded arrays for high conformability and 3D recording, self-softening or self-deployable probes for minimized tissue damage and extensions of the recording sites beyond gliosis, nanostructured probes to reduce the immune response, and cone-shaped electrodes for promoting tissue ingrowth and long-term recording stability. Herein, the recent progress with reference to the many different types of non-conventional arrays is reviewed while highlighting the challenges to be addressed and the microfabrication techniques necessary to implement such features.

Wound healing and fibrosis: current stem cell therapies.

Scarring is a result of the wound healing response and causes tissue dysfunction after injury. This process is readily evident in the skin, but also occurs internally across organ systems in the form of fibrosis. Stem cells are crucial to the innate tissue healing response and, as such, present a possible modality to therapeutically promote regenerative healing while minimizing scaring. In this review, the cellular basis of scaring and fibrosis is examined. Current stem cell therapies under exploration for skin wound healing and internal organ fibrosis are discussed. While most therapeutic approaches rely on the direct application of progenitor-type cells to injured tissue to promote healing, novel strategies to manipulate the scarring response are also presented. As our understanding of developmental and stem cell biology continues to increase, therapies to encourage regeneration of healthy functional tissue after damage secondary to injury or disease will continue to expand.

Microglia are an essential component of the neuroprotective scar that forms after spinal cord injury

The role of microglia in spinal cord injury (SCI) remains poorly understood and is often confused with the response of macrophages. Here, we use specific transgenic mouse lines and depleting agents to understand the response of microglia after SCI. We find that microglia are highly dynamic and proliferate extensively during the first two weeks, accumulating around the lesion. There, activated microglia position themselves at the interface between infiltrating leukocytes and astrocytes, which proliferate and form a scar in response to microglia-derived factors, such as IGF-1. Depletion of microglia after SCI causes disruption of glial scar formation, enhances parenchymal immune infiltrates, reduces neuronal and oligodendrocyte survival, and impairs locomotor recovery. Conversely, increased microglial proliferation, induced by local M-CSF delivery, reduces lesion size and enhances functional recovery. Altogether, our results identify microglia as a key cellular component of the scar that develops after SCI to protect neural tissue.

The Role of Dermoscopy in Assessment of the Activity and Scarring Response in Discoid Lupus Erythematosus

Background:The diagnosis of Discoid Lupus Erythematosus (DLE) is usually made by clinical examination and by histopathology. Recently, dermoscopy has become an integral part in diagnoses of many inflammatory disorders and one of these is DLE.Aims:This research emphasizes the utility of dermoscopy in the assessing lesions of DLE from the point of activity of the disease.Patients and Methods:Thirty-one patients diagnosed with DLE were included in this study. The total number of examined lesions was 125 lesions. All of the lesions were assessed by dermoscopy at different stages of the activity of the diseases.Results:The dermoscopic features of DLE vary according to the stage of activity of the disease. There are characteristic dermoscopic features for the lesions of the scalp different from that of the body. In the active and early phase, the most common dermoscopic features were the presence of lesional and perilesional scales, follicular keratotic plugging, telangiectasia, arborized blood vessels, follicular red dots and perifollicular scales. In addition, there are less common dermoscopic features such as pigmentary changes, white rosettes and pinpoint white dots. For active scalp lesions, the follicular plugging and perifollicular scales were more prominent than that of the body DLE lesions. For inactive and late DLE lesions, the most significant dermoscopic changes were perifollicular whitish halos, variable patchy whitish hypopigmented areas, and the presence of white colored structureless areas.Conclusion:The present study provides new insights into the dermoscopic variability of DLE lesions at different levels of activity.

Heart Regeneration in the Mexican Cavefish

SummaryAlthough Astyanax mexicanus surface fish regenerate their hearts after injury, their Pachón cave-dwelling counterparts cannot and, instead, form a permanent fibrotic scar, similar to the human heart. Myocardial proliferation peaks at similar levels in both surface fish and Pachón 1 week after injury. However, in Pachón, this peak coincides with a strong scarring and immune response, and ultimately, cavefish cardiomyocytes fail to replace the scar. We identified lrrc10 to be upregulated in surface fish compared with Pachón after injury. Similar to cavefish, knockout of lrrc10 in zebrafish impairs heart regeneration without affecting wound cardiomyocyte proliferation. Furthermore, using quantitative trait locus (QTL) analysis, we have linked the degree of heart regeneration to three loci in the genome, identifying candidate genes fundamental to the difference between scarring and regeneration. Our study provides evidence that successful heart regeneration entails a delicate interplay between cardiomyocyte proliferation and scarring.

Advanced in Molecular Mechanisms of Atherosclerosis: From Lipids to Inflammation

BACKGROUND: Atherosclerosis is a leading cause of vascular disease worldwide. During the past several decades, landmark discoveries in the field of vascular biology have evolved our understanding of the biology of blood vessels and the pathobiology of local and systemic vascular disease states and have led to novel disease-modifying therapies for patients. This review is made to understand the molecular mechanism of atherosclerosis for these future therapies.CONTENT: Advances in molecular biology and -omics technologies have facilitated in vitro and in vivo studies which revealed that blood vessels regulate their own redox milieu, metabolism, mechanical environment, and phenotype, in part, through complex interactions between cellular components of the blood vessel wall and circulating factors. Dysregulation of these carefully orchestrated homeostatic interactions has also been implicated as the mechanism by which risk factors for cardiopulmonary vascular disease lead to vascular dysfunction, structural remodeling and, ultimately, adverse clinical events.SUMMARY: Atherosclerosis is a heterogeneous disease, despite a common initiating event of apoB-lipoproteins. Despite of acute thrombotic complications, an adequate resolution response is mounted, where efferocytosis prevents plaque necrosis and a reparative scarring response (the fibrous cap) prevents plaque disruption. However, a small percentage of developing atherosclerotic lesions cannot maintain an adequate resolution response, which leading to the formation of clinically dangerous plaques that can trigger acute lumenal thrombosis and tissue ischemiaand infarction.KEYWORDS: atherosclerosis, oxidative stress, inflammation, efferocytosis, foam cells, thrombosis

Criocirurgia no tratamento do carcinoma de células escamosas em gato: relato de caso

O carcinoma de células escamosas (CCE) que atinge a espécie felina acomete regiões como o tecido subcutâneo, pele e junções mucocutâneas. Sua etiologia ainda é pouco conhecida, mas tem como fator desencadeante a radiação ultravioleta associada a pouca queratinização do tecido. As lesões são caracterizadas por aspectos inflamatórios e proliferativos, muitas vezes friáveis ao toque e com formação de crostas. O diagnóstico é realizado com o emprego de citologia aspirativa por agulha fina e biopsia local. O tratamento preconizado é a criocirurgia que apresenta uma resposta cicatricial adequada. Este relato descreve o tratamento para CCE em um gato, macho, com 10 anos de idade, valendo-se da criocirurgia.

Influence of resveratrol on liver fibrosis induced by dimethylnitrosamine in male rats.

Liver fibrosis is a significant health problem which represents the liver’s scarring process and response to injury through deposition of collagen and extracellular matrix, and ultimately leads to cirrhosis. Resveratrol is a naturally occurring phytoalexin found predominantly in grapes. This study aimed to investigate the antifibrotic role of resveratrol on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Rats were divided into four groups and treated for three weeks; control, resveratrol administered orally (20 mg/kg daily), DMN intraperitoneally injected (10 mg/kg 3 days/week), and the last group was pre-treated daily with resveratrol then injected with DMN, 3 days/week. DMN administration induced severe liver pathological alterations. However, oral administration of resveratrol before DMN significantly prevented the induced loss in body weight, as well as the increase in liver weight which arise from DMN administration. Resveratrol has also inhibited the elevation of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin levels. Furthermore, resveratrol significantly increased hepatic reduced glutathione (GSH) levels and reduced the levels of malondialdehyde (MDA) due to its antioxidants effect as well as increased serum protein levels. In addition, DMN induced elevation in hydroxyproline content. On the other hand, hydroxyproline level was significantly reduced in the resveratrol pretreated rats. Resveratrol has also remarkably maintained the normal liver lobular architecture. Moreover, resveratrol had displayed potent potentials to prevent collagen deposition, lymphocytic infiltration, necrosis, steatosis, vascular damage, blood hypertention, cholangiocyte proliferation. It can be concluded that resveratrol has a marked protective role on DMN-induced liver fibrosis in rats, and can be considered as antiproliferative, antihypertensive, as well as antifibrotic agent and may be used to block the development of liver fibrosis.

Nrf2 activation is required for curcumin to induce lipocyte phenotype in hepatic stellate cells

Hepatic fibrosis is a reversible scarring response that commonly occurs with chronic liver injury. During hepatic fibrogenesis, the major effector hepatic stellate cells (HSCs) become activated, featured by disappeared intracellular lipid droplets, decreased retinoid storage, and dysregulated expression of genes associated with lipid and retinoid metabolism. Compelling evidence suggested that recovery of retinoid droplets could inhibit HSC activation, while the precise molecular basis underlying the phenotypical switch still remained unclear. In this study, curcumin increased the abundance of lipid droplets and content of triglyceride in activated HSCs. In addition, curcumin could concentration-dependently regulate genes associated with lipid and retinoid metabolism. Further, consistent results were obtained from in vivo experiments. Curcumin increased Nrf2 expression and nuclear translocation, and its binding activity to DNA, which might be associated with suppression of Kelch-like ECH-associated protein 1 in HSCs. Of interest was that Nrf2 overexpression plasmids, in contract to Nrf2 siRNA, strengthened the effect of curcumin on induction of lipocyte phenotype. In in vivo system, Nrf2 knockdown mediated by Nrf2 shRNA lentivirus not only accelerated the lipid degradation in HSCs but also promoted the progression of CCl4-induced hepatic fibrosis in mice. Noteworthily, Nrf2 knockdown abolished the protective effect of curcumin. In conclusion, curcumin could induce lipocyte phenotype of activated HSCs via activating Nrf2. Nrf2 could be a target molecule for antifibrotic strategy.

Anti-scarring effects of butaprost on human subconjunctival Tenon's fibroblasts.

To investigate the toxicity of the E-prostanoid 2 (EP2) receptor agonist, butaprost against human subconjunctival (Tenon's capsule) fibroblasts, and to determine the underlying mechanism. We isolated Tenon's fibroblasts from the subconjunctival area of healthy subjects and evaluated the types of EP receptors expressed using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). The toxicity of butaprost against the fibroblasts was evaluated using methyl thiazolyl tetrazolium and lactic dehydrogenase assays. The inhibition of conjunctival fibroblast proliferation by butaprost was assessed by measuring α-actin levels. The underlying mechanism was assessed by measuring intracellular cyclic adenosine monophosphate (cAMP) levels. Intergroup differences were statistically analyzed using an independent t-test. Densitometry of the Western blot bands was performed using the Image J software. Quantitative real-time RT-PCR revealed that the fibroblast EP2 receptor levels were higher than those of the other EP receptors. Butaprost did not show toxicity against Tenon's tissue, but inhibited conjunctival fibroblast proliferation by reducing collagen synthesis. EP2 receptor activation enhanced the cAMP cascade, which might be an important mechanism underlying this effect. Butaprost effectively reduces the subconjunctival scarring response. Given the significance of wound healing modulation in blebs, butaprost's inhibitory effect on subconjunctival Tenon's fibroblasts may be beneficial in managing postoperative scarring in glaucoma surgery.

Abstract 5298: Lung cancer risk and scarring on imaging and histology in the National Lung Screening Trial

Abstract Background: The contribution of pulmonary scars to lung cancer development and the degree to which lung cancers cause a scarring response are unclear. Also unknown is how lung scarring impacts lung cancer screening. Methods: We evaluated associations between scarring and lung cancer in the National Lung Screening Trial (NLST), a lung cancer screening trial among current or former, heavy smokers, 55-74 years-old. Baseline scarring (presence vs. absence) on screening low dose computed tomography (LDCT) scan was assessed at baseline (T0). Associations of T0 scarring with screen-detected lung cancers and with interval-detected lung cancers missed on screening within 3 years of T0 screen were analyzed using multinomial logistic regression. Cox proportional hazards models were used to analyze the relationship between T0 scarring and incident lung cancers diagnosed >3 years after T0. Regression models included age, sex, race, smoking history, chronic obstructive pulmonary disease, history of pneumonia, and family history of lung cancer. A thoracic pathologist (first author) evaluated lung cancer pathology slides from the Lung Screening Study (LSS) subset of NLST for scar grade (none, sparse, dense) and maturity (none, immature, intermediate, mature). Associations between T0 scarring on LDCT and histological scarring were examined by logistic regression. Results: NLST’s LDCT arm enrolled 26,722 participants (65% from the LSS). T0 scars were present in 132 (22%) screen-detected, 12 (29%) interval-detected, and 94 (26%) incident lung cancer cases. T0 scarring did not increase or decrease screen-detection of cancers [odds ratio (OR) 95% CI: 1.03 (0.84-1.26)]. However, scarring might increase the chance of an interval-detected cancer [OR (95% CI): 1.54 (0.76-3.12)]. After screening stopped, T0 scarring was associated with increased incident lung cancer risk [hazard ratio (HR) (95% CI): 1.27 (1.00-1.62); P=0.048]. Pathology slides were available for 258 (38%) lung cancers in LSS. Lung scarring was found in 172 (67%) of these cancers with 58 (22%) being characterized as mature scars. On microscopic review, scars were found in 80 (66%) ADC, 46 (82%) squamous cell carcinomas, and 20 (51%) bronchioloalveolar carcinomas. Microscopic scarring tended to be more frequent among cases with T0 scarring than those without T0 scarring (75% vs. 64%; P=0.10) [OR (95% CI): 1.89 (0.98-3.86)]. Conclusion: The association between T0 scarring and incident lung cancer over a period of more than 3 years is consistent with an etiologic contribution of scarring to development of lung cancer. The relationship between T0 scarring and scarring on microscopic evaluation suggests that scarring preceded the cancer, further supporting an etiologic relationship. Finally, the borderline association of T0 scarring and interval cancers suggests that scarring may decrease the sensitivity of screening. Citation Format: Alison L. Van Dyke, Christine D. Berg, Neil E. Caporaso, Hormuzd A. Katki, Anil K. Chaturvedi, Eric A. Engels. Lung cancer risk and scarring on imaging and histology in the National Lung Screening Trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5298. doi:10.1158/1538-7445.AM2017-5298