Role of host genetics in fibrosis

Mechanisms of lymphoma-stromal interactions focusing on tumor-associated macrophages, fibroblastic reticular cells, and follicular dendritic cells

The interaction between cancer cells and stromal cells contributes to the pathogenesis of various types of tumors in the tumor microenvironment (TME). Macrophages (Mφs), a type of stromal cell, are transformed into tumor-associated Mφs (TAMs) after integrating within solid tumors. TAMs are known to interact with cancer cells and induce tumor progression. Thus, the cancer cells construct an organ-specific TME, which is advantageous for the survival of cancer cells in the TME. The density of stromal cells is known to be involved in the prognosis of patients with lymphomas. A higher density of stromal cells increases the interaction between lymphoma cells and stromal cells, promoting lymphoma progression. This review focuses on stromal cells in lymphoid tissues, such as TAMs, fibroblastic reticular cells (FRCs), and follicular dendritic cells (FDCs). This review also focuses on the signal transduction caused by stromal cells and tumor cells via factors such as cytokines. IL-10 and other cytokines secreted by TAMs activate the JAK/STAT pathway in lymphoma cells of follicular lymphoma, classic Hodgkin lymphoma, and diffuse large B-cell lymphoma. FRCs play roles in tumor promotion in follicular lymphoma and diffuse large B-cell lymphoma. Cytokines/chemokines secreted by FDCs play essential roles in lymphoma cell survival, proliferation, invasion, and migration in follicular lymphoma. In conclusion, TAMs, FRCs, and FDCs play crucial roles in the TME of lymphomas. Furthermore, histological spatial analysis revealing the positional relationship of each cell could highlight lymphoma-stromal interactions.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

Arthrofibrosis After Total Knee Arthroplasty: A Critical Analysis Review

» Arthrofibrosis after total knee arthroplasty (TKA) is the new formation of excessive scar tissue that results in limited ROM, pain, and functional deficits.» The diagnosis of arthrofibrosis is based on the patient's history, clinical examination, absence of alternative diagnoses from diagnostic testing, and operative findings. Imaging is helpful in ruling out specific causes of stiffness after TKA. A biopsy is not indicated, and no biomarkers of arthrofibrosis exist.» Arthrofibrosis pathophysiology is multifactorial and related to aberrant activation and proliferation of myofibroblasts that primarily deposit type I collagen in response to a proinflammatory environment. Transforming growth factor-beta signaling is the best established pathway involved in arthrofibrosis after TKA.» Management includes both nonoperative and operative modalities. Physical therapy is most used while revision arthroplasty is typically reserved as a last resort. Additional investigation into specific pathophysiologic mechanisms can better inform targeted therapeutics.

Interleukin 4/13 signaling in cardiac regeneration and repair

Interleukin 4 (IL4) and interleukin 13 (IL13) are closely related cytokines that have been classically attributed to type II immunity, namely, differentiation of T-helper 2 (TH2) cells and alternative activation of macrophages. Although the role of IL4/13 has been well described in various contexts such as defense against helminth parasites, pathogenesis of allergic disease, and several models of wound healing, relatively little is known about the role of IL4/13 in the heart following injury. Emerging literature has identified various roles for IL4/13 in animal models of cardiac regeneration as well as in the adult mammalian heart following myocardial injury. Notably, although IL4 and IL13 signal to hematopoietic cell types following myocardial infarction (MI) to promote wound healing phenotypes, there is substantial evidence that these cytokines can signal directly to non-hematopoietic cell types in the heart during development, homeostasis, and following injury. Comprehensive understanding of the molecular and cellular actions of IL4/13 in the heart is still lacking, but overall evidence to date suggests that activation of these cytokines results in beneficial outcomes with respect to cardiac repair. Here, we aim to comprehensively review the role of IL4 and IL13 and their prospective mechanisms in cardiac regeneration and repair.

Clinical Management of Arthrofibrosis: State of the Art and Therapeutic Outlook

* Arthrofibrosis is a pathologic condition that is characterized by excessive periarticular scar-tissue formation. Arthrofibrosis may occur secondary to injury, surgical trauma, hemarthrosis, or infection, or it may occur idiopathically.* The pathogenesis of arthrofibrosis is incompletely understood but involves the dysregulation of normal reparative pathways, with transforming growth factor-beta (TGF-[beta]) as a principal mediator.* Current treatment options for arthrofibrosis primarily involve physiotherapy, operative manipulation, and surgical debridement, all with imperfect results.* Currently, there are no pharmacologic treatment options for arthrofibrosis. This has prompted increased investigational interest in the development of antifibrotic intra-articular therapies.

Interleukin-13 receptor α2 is a novel marker and potential therapeutic target for human melanoma

Malignant melanoma is one of the untreatable cancers in which conventional therapeutic strategies, including chemotherapy, are hardly effective. Therefore, identification of novel therapeutic targets involved in melanoma progression is urgently needed for developing effective therapeutic methods. Overexpression of interleukin-13 receptor α2 (IL13Rα2) is observed in several cancer types including glioma and pancreatic cancer. Although IL13Rα2 is implicated in the progression of various types of cancer, its expression and roles in the malignant melanoma have not yet been elucidated. In the present study, we showed that IL13Rα2 was expressed in approximately 7.5% melanoma patients. While IL13Rα2 expression in human melanoma cells decreased their proliferation in vitro, it promoted in vivo tumour growth and angiogenesis in melanoma xenograft mouse model. We also found that the expression of amphiregulin, a member of the epidermal growth factor (EGF) family, was correlated with IL13Rα2 expression in cultured melanoma cells, xenograft tumour tissues and melanoma clinical samples. Furthermore, expression of amphiregulin promoted tumour growth, implicating causal relationship between the expression of IL13Rα2 and amphiregulin. These results suggest that IL13Rα2 enhances tumorigenicity by inducing angiogenesis in malignant melanoma, and serves as a potential therapeutic target of malignant melanoma.

Low-grade infections as a possible cause of arthrofibrosis after total knee arthroplasty

Purpose

Arthrofibrosis after total knee arthroplasty represents a considerable burden for the patient and a therapeutic challenge for the practitioner. One possible cause discussed in the literature is a low-grade infection. This hypothesis should be examined within the scope of this retrospective study.

Patients and methods

Nineteen patients with clinical symptoms of arthrofibrosis after primary total knee arthroplasty were examined between January, 1999 and January, 2012. Incorrect positioning was radiologically ruled out. All patients were examined clinically (score of Freeman as well as Blauth and Jäger), radiologically (component and leg alignment, patella height according to Insall and Salvati), microbiologically (culture-based procedures), molecular biologically (PCR) and histologically in the course of an open revision of the prosthesis.

Results

According to the score of Freeman et al. (1977), a highly significant improvement in pain (p = 0.007) and in the overall score (p = 0.003) was shown. The knee joint mobility did not change significantly (p = 0.795). PCR was negative in 17 patients. One patient showed a PCR-positive result of the synovial membrane for Corynebacterium spp., while Staphylococcus warneri was detected in the culture. Another patient had a positive result of synovia PCR for Enterococcus cecorum as well as Corynebacterium spp. However, this culture was sterile. In 16 patient samples, no bacterial growth was detectable. Two samples were not evaluable. The main histopathological findings were synovialitis and fibrosis.

Conclusion

The hypothesis of low-grade-infection-induced arthrofibrosis after total knee arthroplasty could not be confirmed in this study. However, based on this small study population the conclusion needs to be confirmed by new and larger studies, ideally prospectively designed including a control group.

Upregulation of Foreign Body Response in Obese Mice

OBJECTIVE

Obesity is a highly prevalent multifactorial metabolic condition in which the need for functional bioengineered substitutes (e.g., scaffolds for tissue engineering) is likely to occur. However, the adverse foreign body response (FBR) that invariably takes place adjacent to implant devices impairing their function is poorly characterized in this condition. This study investigated the influence of obesity on the host response to a synthetic matrix implanted subcutaneously in high-fat-fed obese mice.

METHODS

Histological analysis of 14-day-old implants was performed to identify collagen deposition, capsule thickness, fibroblast-like cells, foreign body giant cells, and mast cells. In addition, transforming growth factor β1 (TGF-β1) levels in the implants and serum were determined.

RESULTS

All fibrogenic markers (and TGF-β1 levels) increased in the implants of obese mice compared with their nonobese counterparts. Particularly relevant was the fibrous capsule thickness in implants of obese mice (234.2 ± 22.1 µm vs. 109.2 ± 13.4 µm in implants of nonobese animals).

CONCLUSIONS

The study results showing that obesity upregulates the main features of the FBR induced by subcutaneous implants in mice may be relevant in understanding biomaterial integration and performance in this condition. This is crucial to the development of strategies to maintain the integrity and function of implantable devices.

Tissue Engineered Skin Substitutes

The fundamental skin role is to supply a supportive barrier to protect body against harmful agents and injuries. Three layers of skin including epidermis, dermis and hypodermis form a sophisticated tissue composed of extracellular matrix (ECM) mainly made of collagens and glycosaminoglycans (GAGs) as a scaffold, different cell types such as keratinocytes, fibroblasts and functional cells embedded in the ECM. When the skin is injured, depends on its severity, the majority of mentioned components are recruited to wound regeneration. Additionally, different growth factors like fibroblast growth factor (FGF), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) are needed to orchestrated wound healing process. In case of large surface area wounds, natural wound repair seems inefficient. Inspired by nature, scientists in tissue engineering field attempt to engineered constructs mimicking natural healing process to promote skin restoration in untreatable injuries. There are three main types of commercially available engineered skin substitutes including epidermal, dermal, and dermoepidermal. Each of them could be composed of scaffold, desired cell types or growth factors. These substitutes could have autologous, allogeneic, or xenogeneic origin. Moreover, they may be cellular or acellular. They are used to accelerate wound healing and recover normal skin functions with pain relief. Although there are a wide variety of commercially available skin substitutes, almost none of them considered as an ideal equivalents required for proper wound healing.

Determining Candidate Single Nucleotide Polymorphisms in Acquired Laryngotracheal Stenosis

OBJECTIVES/HYPOTHESIS

Despite wide adoption of strategies to prevent injury from prolonged intubation and tracheotomy, acquired laryngotracheal stenosis (ALTS) has not disappeared. ALTS' persistence may be due to patient factors that confer unique susceptibility for some. We sought to identify genetic markers in genes associated with wound healing that could be associated with ALTS.

STUDY DESIGN

Case-control study.

METHODS

One hundred thirty-eight patients were recruited, 53 patients with ALTS and 85 control patients who underwent intubation or tracheotomy without evidence of ALTS. The patients' DNA was isolated from whole blood. Custom primers were designed, and the TaqMan assay employing allele-specific polymerase chain reaction was used to interrogate single nucleotide polymorphisms (SNPs) rs1799750, rs522616, rs2276109, rs2569190, rs1800469, and rs1024611 of candidate wound healing genes MMP1, MMP3, MMP12, CD14, TGFβ1, and MCP1, respectively. A logistic regression model was used to examine the association of candidate gene polymorphisms with the presence or absence of ALTS.

RESULTS

All 138 patients were successfully genotyped. No significant association was found between candidate SNPs and development of ALTS in the overall group. However, subgroup analysis within each ethnicity identified SNPs that are associated with ALTS depending upon the ethnic background.

CONCLUSIONS

Patient factors such as variations in wound healing due to functional SNPs may shed light on the development of ALTS. There may be a difference in susceptibility to developing ALTS in different ethnic backgrounds. These preliminary findings need to be corroborated in larger population studies.

LEVEL OF EVIDENCE

3b. Laryngoscope, 128:E111-E116, 2018.

Arthrofibrosis Associated With Total Knee Arthroplasty

BACKGROUND

Arthrofibrosis is a debilitating postoperative complication of total knee arthroplasty (TKA). It is one of the leading causes of hospital readmission and a predominant reason for TKA failure. The prevalence of arthrofibrosis will increase as the annual incidence of TKA in the United States rises into the millions.

METHODS

In a narrative review of the literature, the etiology, economic burden, treatment strategies, and future research directions of arthrofibrosis after TKA are examined.

RESULTS

Characterized by excessive proliferation of scar tissue during an impaired wound healing response, arthrofibrotic stiffness causes functional deficits in activities of daily living. Postoperative, supervised physiotherapy remains the first line of defense against the development of arthrofibrosis. Also, adjuncts to traditional physiotherapy such as splinting and augmented soft tissue mobilization can be beneficial. The effectiveness of rehabilitation on functional outcomes depends on the appropriate timing, intensity, and progression of the program, accounting for the patient's ability and level of pain. Invasive treatments such as manipulation under anesthesia, debridement, and revision arthroplasty improve range of motion, but can be traumatic and costly. Future studies investigating novel treatments, early diagnosis, and potential preoperative screening for risk of arthrofibrosis will help target those patients who will need additional attention and tailored rehabilitation to improve TKA outcomes.

CONCLUSION

Arthrofibrosis is a multi-faceted complication of TKA, and is difficult to treat without an early, tailored, comprehensive rehabilitation program. Understanding the risk factors for its development and the benefits and shortcomings of various interventions are essential to best restore mobility and function.

The Pressure of Aging

Significant hemodynamic changes ensue with aging, leading to an ever-growing epidemic of hypertension. Alterations in central arterial properties play a major role in these hemodynamic changes. These alterations are characterized by an initial decline in aortic distensibility and an increase of diastolic blood pressure, followed by a sharp increase in pulse wave velocity (PWV), and an increase in pulse pressure (PP) beyond the sixth decade. However, the trajectories of PWV and PP diverge with advancing age. There is an increased prevalence of salt-sensitive hypertension with advancing age that is, in part, mediated by marinobufagenin, an endogenous sodium pump ligand.

Tumor necrosis factor-α -G308A polymorphism is associated with liver pathological changes in hepatitis C virus patients

AIM

To investigate the association of tumor necrosis factor alpha (TNFα) -G308A polymorphism with different liver pathological changes in treatment-naïve Egyptian patients infected with hepatitis C virus (HCV) genotype 4.

METHODS

This study included 180 subjects, composed of 120 treatment-naïve chronic HCV patients with different fibrosis grades (F0-F4) and 60 healthy controls. The TNFα -G308A region was amplified by PCR and the different genotypes were detected by restriction fragment length polymorphism analysis. The TNFα protein was detected by enzyme-linked immunosorbent assay. The influence of different TNFα -G308A genotypes on TNFα expression and liver disease progression were statistically analyzed. The OR and 95%CI were calculated to assess the relative risk confidence.

RESULTS

Current data showed that the TNFα -G308A SNP frequency was significantly different between controls and HCV infected patients (P = 0.001). Both the AA genotype and A allele were significantly higher in late fibrosis patients (F2-F4, n = 60) than in early fibrosis patients (F0-F1, n = 60) (P = 0.05, 0.04 respectively). Moreover, the GA or AA genotypes increased the TNFα serum level greater than the GG genotype (P = 0.002). The results showed a clear association between severe liver pathological conditions (inflammation, steatosis and fibrosis) and (GA + AA) genotypes (P = 0.035, 0.03, 0.04 respectively). The stepwise logistic regression analysis showed that the TNFα genotypes (GA + AA) were significantly associated with liver inflammation (OR = 3.776, 95%CI: 1.399-10.194, P = 0.009), severe steatosis (OR = 4.49, 95%CI: 1.441-14.0, P = 0.010) and fibrosis progression (OR = 2.84, 95%CI: 1.080-7.472, P = 0.034). Also, the A allele was an independent risk factor for liver inflammation (P = 0.003), steatosis (P = 0.003) and fibrosis (P = 0.014).

CONCLUSION

TNFα SNP at nucleotide -308 represents an important genetic marker that can be used for the prognosis of different liver pathological changes in HCV infected patients

Role of fibrogenic and inflammatory cytokines in HCV-induced fibrosis

HCV is one of the main causative agents of liver fibrosis and hepatocellular carcinoma. Liver inflammation resulting from HCV infection triggers fibrosis. In HCV-related fibrosis, differentiated hepatic stellate cells (HSCs) known as myofibroblasts participate in the fibrogenic and inflammatory response. TGF-β1 and CTGF, released from these HSCs, have been implicated as master cytokines mediating HCV induced hepatic fibrosis. PDGF is another potent mitogen, which facilitates the progression of liver fibrosis by enhancing the proliferation and migration of HSCs. In addition to these major cytokines, the release of TNF-α, IL-6, IL-1b and IL-10 by immune cells also promotes the effect of HCV induced fibrosis. Targeting these cytokines may offer the potential for treatments to prevent or cure fibrosis.

Impact of OAS1 Exon 7 rs10774671 Genetic Variation on Liver Fibrosis Progression in Egyptian HCV Genotype 4 Patients

The aim of this study was to assess the impact of genetic variants of oligoadenylate synthetase 1 (OAS1) single-nucleotide polymorphism (SNP) rs10774671 at the exon 7 splice acceptor site on liver fibrosis progression and hepatitis C virus (HCV) outcome in Egyptian HCV genotype 4 patients. In this study, 195 subjects were enrolled; 60 controls and 135 chronic HCV genotype 4 patients with different fibrosis grades. All subjects were genotyped for OAS1 SNP rs10774671 polymorphism by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. There was an increasing trend of liver fibrosis progression as 52.9% GG, 73.6% GA, and 83.3% AA genotypes were detected in late fibrosis patients (p = 0.025). The AA genotype was higher in the late fibrosis group than in the early fibrosis group (83.3% vs. 16.7%) (p = 0.001). The A allele was significantly affecting the liver fibrosis progression rate, more than the G allele (p = 0.001). The multivariate analysis showed that the OAS1 GA and AA genotypes were independent factors associated with liver progression (p = 0.009, odds ratio [OR] 3.467, 95% confidence interval [CI] 1.273-7.584). In addition, the A allele was associated with liver fibrosis progression (p = 0.014, OR 2.525, 95% CI 1.157-4.545). The polymorphism at OAS1 exon 7 rs3741981 might be a potential genetic marker and can be useful in the assessment of liver fibrosis progression and disease outcome in HCV-infected patients.

Advances in Skin Substitutes-Potential of Tissue Engineered Skin for Facilitating Anti-Fibrotic Healing

Skin protects the body from exogenous substances and functions as a barrier to fluid loss and trauma. The skin comprises of epidermal, dermal and hypodermal layers, which mainly contain keratinocytes, fibroblasts and adipocytes, respectively, typically embedded on extracellular matrix made up of glycosaminoglycans and fibrous proteins. When the integrity of skin is compromised due to injury as in burns the coverage of skin has to be restored to facilitate repair and regeneration. Skin substitutes are preferred for wound coverage when the loss of skin is extensive especially in the case of second or third degree burns. Different kinds of skin substitutes with different features are commercially available; they can be classified into acellular skin substitutes, those with cultured epidermal cells and no dermal components, those with only dermal components, and tissue engineered substitutes that contain both epidermal and dermal components. Typically, adult wounds heal by fibrosis. Most organs are affected by fibrosis, with chronic fibrotic diseases estimated to be a leading cause of morbidity and mortality. In the skin, fibroproliferative disorders such as hypertrophic scars and keloid formation cause cosmetic and functional problems. Dermal fibroblasts are understood to be heterogeneous; this may have implications on post-burn wound healing since studies have shown that superficial and deep dermal fibroblasts are anti-fibrotic and pro-fibrotic, respectively. Selective use of superficial dermal fibroblasts rather than the conventional heterogeneous dermal fibroblasts may prove beneficial for post-burn wound healing.

Donor caveolin 1 (CAV1) genetic polymorphism influences graft function after renal transplantation

Background

Identification of the culprit genes underlying multifactorial diseases is one of the most important current challenges of molecular genetics. While recent advances in genomics research have accelerated the discovery of susceptibility genes, much remains to be learned about the functions of disease-associated genetic variants. Recently, Moore and co-workers identified, in the donor genome, an association between a common genetic variant (rs4730751) in the gene encoding caveolin-1 (CAV1), a major structural component of caveolae, and long-term allograft survival.

Methods

Four hundred seventy-five renal recipients consecutively transplanted were included in this study. Donor genomic DNA was extracted and used to genotype CAV1 rs4730751 Single Nucleotide Polymorphism.

Results

Patients receiving a graft carrying CAV1 rs4730751 AA genotype displayed a significant decrease in estimated glomerular filtration rate and a significant increase in serum creatinine in both univariate and multivariate analyzes. Moreover, patients receiving a graft with CAV1 AA genotype significantly developed more interstitial fibrosis lesions on systematic biopsies performed 3 months post-transplantation.

Conclusions

Genotyping of CAV1 may be relevant to identify patients at risk of adverse renal transplant outcome.

Autoimmune Myelofibrosis in Systemic Lupus Erythematosus Report of Two Cases and Review of the Literature

Autoimmune myelofibrosis (AIMF) is a rare entity of steroid-responsive bone marrow fibrosis that accompanies a variety of autoimmune diseases, particularly systemic lupus erythematosus (SLE). Rarely it may occur in patients with autoimmune markers but no definable autoimmune disease (Primary-AIMF). We report the cases of two young women with SLE-associated AIMF (SLE-AIMF). The first patient was a young woman who had pancytopenia, massive splenomegaly and reticulin fibrosis in the marrow biopsy. The pancytopenia and splenomegaly resolved completely within weeks of treatment with corticosteroids. Repeat marrow biopsy showed marked regression of marrow fibrosis. The second patient was a young woman with fever, anasarca, bicytopenia and reticulin fibrosis in the marrow biopsy. Steroid therapy resulted in rapid clinical improvement and resolution of pancytopenia. A review of the literature revealed a total of 30 patients with SLE-AIMF reported to-date. Patients with SLE-AIMF are young women with SLE and blood cytopenia who are found to have increased bone marrow reticulin on marrow biopsy. Steroid therapy results in rapid hematological recovery and regression of marrow fibrosis. Whether AIMF is one of several hematological complications of SLE, or represents a unique and distinct subset of patients with SLE in not clear. Prospective studies with longer follow-up are needed to better define the prevalence and clinical spectrum of SLE-AIMF.

The effect of keratinocytes on the biomechanical characteristics and pore microstructure of tissue engineered skin using deep dermal fibroblasts

Fibrosis affects most organs, it results in replacement of normal parenchymal tissue with collagen-rich extracellular matrix, which compromises tissue architecture and ultimately causes loss of function of the affected organ. Biochemical pathways that contribute to fibrosis have been extensively studied, but the role of biomechanical signaling in fibrosis is not clearly understood. In this study, we assessed the effect keratinocytes have on the biomechanical characteristics and pore microstructure of tissue engineered skin made with superficial or deep dermal fibroblasts in order to determine any biomaterial-mediated anti-fibrotic influences on tissue engineered skin. Tissue engineered skin with deep dermal fibroblasts and keratinocytes were found to be less stiff and contracted and had reduced number of myofibroblasts and lower expression of matrix crosslinking factors compared to matrices with deep fibroblasts alone. However, there were no such differences between tissue engineered skin with superficial fibroblasts and keratinocytes and matrices with superficial fibroblasts alone. Also, tissue engineered skin with deep fibroblasts and keratinocytes had smaller pores compared to those with superficial fibroblasts and keratinocytes; pore size of tissue engineered skin with deep fibroblasts and keratinocytes were not different from those matrices with deep fibroblasts alone. A better understanding of biomechanical characteristics and pore microstructure of tissue engineered skin may prove beneficial in promoting normal wound healing over pathologic healing.

Translational genomics of acquired laryngotracheal stenosis

OBJECTIVES/HYPOTHESIS

Acquired laryngotracheal stenosis (ALTS) results from abnormal mucosal wound healing after laryngeal and/or tracheal injury. Patients with ALTS often present late after significant reduction of the airway lumen and onset of symptoms. Motivated by the need for earlier detection of affected patients, we sought to investigate genetic markers for ALTS that would identify susceptible patients.

STUDY DESIGN

Pilot Case-Control Study.

METHODS

Seventy-six patients were recruited, 40 patients with ALTS and 36 control patients with airway injury but without ALTS. DNA was isolated from whole blood and formalin-fixed paraffin-embedded specimens from patients. Custom primers were designed and the TaqMan assay employing allele-specific polymerase chain reaction was used to interrogate single nucleotide polymorphisms (SNPs): rs2569190, rs1799750, and rs1800469 located in candidate genes CD14, matrix metalloproteinase-1 (MMP-1), and transforming growth factor-β1 (TGF-β1), respectively. A logistic regression model was used to examine the association of candidate gene polymorphisms with the presence or absence of ALTS.

RESULTS

All 76 patients were successfully genotyped at the three loci of interest by optimizing the genotyping protocol. MMP-1 SNP rs1799750 was most significantly associated with development of ALTS (P = 0.005).

CONCLUSION

Identification of SNPs associated with development of ALTS will provide new experimental targets to study wound healing in human subjects. The association found in the current study between ALTS and SNP rs1799750 is being validated in a larger population examining an expanded set of relevant SNPs. Identifying patients with genetic susceptibility to ALTS and poor wound healing in the upper airway will be useful for management of patients after upper-airway injury.

Molecular and cellular mechanisms of loss of residual hearing after cochlear implantation

OBJECTIVES

We describe the various molecular and cellular pathways that lead to early and delayed loss of residual hearing after cochlear implantation.

METHODS

We performed a systematic review using the Medline database with the key words cochlear implant, residual hearing, inflammation, apoptosis, and necrosis.

RESULTS

The mechanisms underlying the loss of residual hearing after cochlear implantation are multiple. Early hearing loss may be provoked by the surgical access to the inner ear spaces and by trauma caused by insertion of the electrode array. After the initial trauma, an acute inflammatory response promotes elevated levels of cytokines and reactive oxygen species, which in turn promote sensory cell loss by apoptosis, necrosis, and necrosis-like programmed cell death. Treatments that counteract such an inflammatory reaction, production of reactive oxygen species, and apoptosis are effective at preventing hair cell degeneration. However, delayed hearing loss appears to be a consequence of chronic inflammation with development of fibrotic tissue. The mechanisms that lead to fibrosis are poorly understood, and standard antiinflammatory drugs are insufficient for preventing its development.

CONCLUSIONS

Cochlear implantation is followed by an inflammatory response involving several pathways that lead to either short-term or long-term sensory hair cell degeneration. Future studies should focus on revealing the precise molecular mechanisms induced by cochlear implantation to allow the discovery of new targets for the effective prevention and treatment of loss of residual hearing.

Transforming growth factor β-induced peritoneal fibrosis is mouse strain dependent

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is a rare but devastating complication of peritoneal dialysis. The etiology is unclear, but genetic predisposition may be a contributing factor. We used adenovirus-mediated gene transfer of transforming growth factor (TGF) β1 to the peritoneum in four genetically distinct laboratory mouse strains to assess differences in fibrogenic response.

METHODS

Mice from four genetic backgrounds (C57BL/6J, DBA/2J, C3H/HeJ and SJL/J) received an intraperitoneal injection of an adenovirus expressing TGFβ1 (AdTGFβ1) or control adenovirus (AdDL) and were assessed 4 and 10 days after infection. Submesothelial thickening, angiogenesis and gene expression were quantified from peritoneal tissue. Protein was extracted from omental tissue and assessed for collagen, E-cadherin and TGFβ signaling pathway proteins.

RESULTS

There was a graded response among the mouse strains to the peritoneal overexpression of TGFβ1. TGFβ1 induced a significant fibrogenic response in the C57BL/6J mice, whereas the SJL/J mice were resistant. The DBA/2J and the C3H/HeJ mice had intermediate responses. A similar graded response was seen in collagen protein levels in the omental tissue and in fibrosis-associated gene expression. TGFβ type 1 receptor and SMAD signaling pathways appeared to be intact in all the mouse strains.

CONCLUSIONS

There were significant differences in mouse strain susceptibility to peritoneal fibrosis, suggesting that genetic factors may play a role in the development of peritoneal fibrosis and possibly EPS. As early TGFβ1 signaling mechanisms appear to be intact, we hypothesize that fibrosis resistance in the SJL/J mice lies further down the wound-healing cascade or in an alternate, non-SMAD pathway.

Activation of COL1A2 promoter in human fibroblasts by Escherichia coli

The relationship between bacterial infection and collagen production was investigated using human fibroblasts transfected with the promoter of COL1A2 , which encodes the α1 chain of human type I collagen, linked to a luciferase reporter. The cells were used to assess the gene promoter activity of COL1A2 following bacterial stimulation. The COL1A2 promoter was activated by stimulation with fixed Escherichia coli in a dose-dependent manner, but not by fixed Staphylococcus aureus. Enhancement of collagen production was observed in the E. coli-stimulated fibroblasts compared to those without stimulation. Both anti-human Toll-like receptor (TLR) 4 antibody and polymyxin B clearly blocked the COL1A2 promoter activity stimulated by E. coli, while antibodies against human TLR2 and human transforming growth factor-β (TGF-β) receptor type II did not. These results indicate that E. coli can directly interact with TLR4 expressed on the surface of fibroblasts and can further induce human type I collagen gene expression and collagen production in these cells. These data also suggest that infection by gram-negative bacteria may cause fibrosis.

Evolution of hepatic fibrosis research

Molecular analysis of hepatic fibrogenesis has progressed with respect to both fibrosis progression and regression by using cell biological, molecular biological and (epi)genetic approaches. Recent researches have revealed sources of collagen-producing cells other than hepatic stellate cells in the liver, and the involvement of the innate immune system and oxidative stress in the fibrotic process has attracted new attention. Together with these advancements in basic knowledge on the cellular and molecular biology of hepatic fibrosis, clinical researches have linked the clarification of the relationship between progression of the fibrosis stage and therapeutic efficacy for chronic viral hepatitis and non-alcoholic steatohepatitis and validation of the regression of advanced fibrosis, even cirrhosis, of appropriate therapies using modern medicines. Furthermore, non-invasive assessment of liver fibrosis using an ultrasound-based modality has become a focus in the clinical diagnosis of liver fibrosis instead of liver biopsy. Taken together, liver fibrosis research has been evolving both basically and clinically in the past three decades.

Evolving challenges in hepatic fibrosis

Continued elucidation of the mechanisms of hepatic fibrosis has yielded a comprehensive and nuanced portrait of fibrosis progression and regression. The paradigm of hepatic stellate cell (HSC) activation remains the foundation for defining events in hepatic fibrosis and has been complemented by progress in a number of new areas. Cellular sources of extracellular matrix beyond HSCs have been identified. In addition, the role of chemokine, adipokine, neuroendocrine, angiogenic and NAPDH oxidase signaling in the pathogenesis of hepatic fibrosis has been uncovered, as has the contribution of extracellular matrix stiffness to fibrogenesis. There is also increased awareness of the contribution of innate immunity and greater understanding of the complexity of gene regulation in HSCs and myofibroblasts. Finally, both apoptosis and senescence have been recognized as orchestrated programs that eliminate fibrogenic cells during resolution of liver fibrosis. Ironically, the progress that has been made has highlighted the growing disparity between advances in the experimental setting and their translation into new diagnostic tools and treatments. As a result, focus is shifting towards overcoming key translational challenges in order to accelerate the development of new therapies for patients with chronic liver disease.