Improved airway healing using transforming growth factor beta-3 In a rabbit model

Establishment of a survival rabbit model for laryngotracheal stenosis: A prospective randomized study

Objective

To develop a reproducible survival rabbit model for laryngotracheal stenosis (LTS).

Methods

Seventy New Zealand white (NZW) rabbits were randomly divided into experimental groups (n = 30) and a control group (n = 40). In experimental groups, a nylon brush was inserted retrograde from the tracheotomy through the subglottis and rotated until a full layer circumferential mucosal injury to cartilage exposure, assisted by fiberoptic laryngoscopy (FOL) visualization. Experimental group 1 (n = 10), rotated 10 times; group 2 (n = 20), rotated 20 times. The control group underwent tracheotomy only without nylon brush scraping. The rabbits underwent FOL at 1st, 4th, 8th, and 12th week postinjury respectively to observe the formation of LTS. They were euthanized and the larynxes and tracheas were subjected to gross and histopathological examination at 12 weeks postinjury.

Results

The control group all survived, while five cases in experimental groups died from LTS and/or mucous plug. Histological observation showed that the control group had intact laryngotracheal mucosal epithelium without any stenosis; the experimental groups showed proliferation of fibroblasts and thickening of collagen fibers. The mean stenosis in control group was 9.31 ± 0.98%, while that in experimental group 1 was 32.78 ± 7.07% and 58.25 ± 8.96% in experimental group 2. The difference between the three groups was statistically significant (χ 2 = 47.98, p < .05).

Conclusions

We successfully developed a reproducible survival rabbit model for LTS using a nylon brush through FOL visualization combined with tracheostomy. This model can provide a mature and stable animal model for the exploration of wound-healing pathophysiology and the effect of interventions.

Level of evidence

NA.

TGF-β3 increases the severity of radiation-induced oral mucositis and salivary gland fibrosis in a mouse model

PURPOSE

Toxicities from head and neck (H&N) radiotherapy (RT) may affect patient quality of life and can be dose-limiting. Proteins from the transforming growth factor beta (TGF-β) family are key players in the fibrotic response. While TGF-β1 is known to be pro-fibrotic, TGF-β3 has mainly been considered anti-fibrotic. Moreover, TGF-β3 has been shown to act protective against acute toxicities after radio- and chemotherapy. In the present study, we investigated the effect of TGF-β3 treatment during fractionated H&N RT in a mouse model.

MATERIALS AND METHODS

30 C57BL/6J mice were assigned to three treatment groups. The RT + TGF-β3 group received local fractionated H&N RT with 66 Gy over five days, combined with TGF-β3-injections at 24-hour intervals. Animals in the RT reference group received identical RT without TGF-β3 treatment. The non-irradiated control group was sham-irradiated according to the same RT schedule. In the follow-up period, body weight and symptoms of oral mucositis and lip dermatitis were monitored. Saliva was sampled at five time points. The experiment was terminated 105 d after the first RT fraction. Submandibular and sublingual glands were preserved, sectioned, and stained with Masson's trichrome to visualize collagen.

RESULTS

A subset of mice in the RT + TGF-β3 group displayed increased severity of oral mucositis and increased weight loss, resulting in a significant increase in mortality. Collagen content was significantly increased in the submandibular and sublingual glands for the surviving RT + TGF-β3 mice, compared with non-irradiated controls. In the RT reference group, collagen content was significantly increased in the submandibular gland only. Both RT groups displayed lower saliva production after treatment compared to controls. TGF-β3 treatment did not impact saliva production.

CONCLUSIONS

When repeatedly administered during fractionated RT at the current dose, TGF-β3 treatment increased acute H&N radiation toxicities and increased mortality. Furthermore, TGF-β3 treatment may increase the severity of radiation-induced salivary gland fibrosis.

Poly-D,L-Lactic Acid Stimulates Angiogenesis and Collagen Synthesis in Aged Animal Skin

Angiogenesis promotes rejuvenation in multiple organs, including the skin. Heat shock protein 90 (HSP90), hypoxia-inducible factor-1 alpha (HIF-1α), and vascular endothelial growth factor (VEGF) are proangiogenic factors that stimulate the activities of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and extracellular signal-regulated kinase 1/2 (ERK1/2). Poly-D,L-lactic acid (PDLLA), polynucleotide (PN), and calcium hydroxyapatite (CaHA) are dermal fillers that stimulate the synthesis of dermal collagen. However, it is not yet known whether these compounds promote angiogenesis, which leads to skin rejuvenation. Here, we evaluated whether PDLLA, PN, and CaHA stimulate angiogenesis and skin rejuvenation using H₂O₂-treated senescent macrophages and endothelial cells as an in vitro model for skin aging, and we used young and aged C57BL/6 mice as an in vivo model. Angiogenesis was evaluated via endothelial cell migration length, proliferation, and tube formation after conditioned media (CM) from senescent macrophages was treated with PDLLA, PN, or CaHA. Western blot showed decreased expression levels of HSP90, HIF-1α, and VEGF in senescent macrophages, but higher expression levels of these factors were found after treatment with PDLLA, PN, or CaHA. In addition, after exposure to CM from senescent macrophages treated with PDLLA, PN, or CaHA, senescent endothelial cells expressed higher levels of VEGF receptor 2 (VEGFR2), PI3K, phosphorylated AKT (pAKT), and phosphorylated ERK1/2 (pERK1/2) and demonstrated greater capacities for cell migration, cell proliferation, and tube formation. Based on the levels of 4-hydroxy-2-nonenal, the oxidative stress level was lower in the skin of aged mice injected with PDLLA, PN, or CaHA, while the tumor growth factor (TGF)-β1, TGF-β2, and TGF-β3 expression levels; the density of collagen fibers; and the skin elasticity were higher in the skin of aged mice injected with PDLLA, PN, or CaHA. These effects were greater in PDLLA than in PN or CaHA. In conclusion, our results are consistent with the hypothesis that PDLLA stimulates angiogenesis, leading to the rejuvenation of aged skin. Our study is the first to show that PDLLA, PN, or CaHA can result in angiogenesis in the aged skin, possibly by increasing the levels of HSP90, HIF-1α, and VEGF and increasing collagen synthesis.

The Role of TGF-β3 in Radiation Response

Transforming growth factor-beta 3 (TGF-β3) is a ubiquitously expressed multifunctional cytokine involved in a range of physiological and pathological conditions, including embryogenesis, cell cycle regulation, immunoregulation, and fibrogenesis. The cytotoxic effects of ionizing radiation are employed in cancer radiotherapy, but its actions also influence cellular signaling pathways, including that of TGF-β3. Furthermore, the cell cycle regulating and anti-fibrotic effects of TGF-β3 have identified it as a potential mitigator of radiation- and chemotherapy-induced toxicity in healthy tissue. This review discusses the radiobiology of TGF-β3, its induction in tissue by ionizing radiation, and its potential radioprotective and anti-fibrotic effects.

The role of tracheal wall injury in the development of benign airway stenosis in rabbits

To investigate the role of tracheal wall injury in the development of benign airway stenosis in rabbits. Prospective study. We injured the tracheal walls of 28 New Zealand white rabbits using four different methods. Experimental group: Group A (n = 7, mild injury of tracheal mucosa by ordinary brush under bronchoscopy); Group B (n = 7, severe injury of tracheal mucosa by nylon brush under tracheotomy); Group C (n = 7, tracheal cartilage was injured by vascular clamp after tracheotomy); Group D (n = 7, the tracheal cartilage was injured with vascular forceps and the tracheal mucosa was injured with a nylon brush after tracheotomy). Bronchoscopy was performed on each experimental rabbit at 1, 2, 3 and 4 weeks after operation. High-resolution computed tomography (HRCT) and endobronchial optical coherence tomography (EB-OCT) were performed at 4 weeks, and the rabbits were sacrificed after the examination. Their gross and histological findings were comparatively determined whether the experimental rabbit stenosis was established. No airway stenosis was observed in group A. In group B, 28.57% of experimental rabbits developed tracheal stenosis (granulation tissue proliferation was observed in rabbits No. 2 and No. 6 at 1, 2 and 3 weeks after operation, and the tracheal scar contracture was observed in No.6 rabbit at 4 weeks after operation). Fourteen rabbits in group C and group D had tracheal stenosis caused by granulation tissue proliferation at 1, 2 and 3 weeks after operation. At the fourth week after operation, 71.43% of experimental rabbits had tracheal stenosis due to granulation tissue hyperplasia, 7.14% of experimental rabbits had tracheal stenosis due to scar contracture and granulation hyperplasia, and 21.43% of experimental rabbits had tracheal stenosis due to scar contracture. EB-OCT scan showed that the cartilage layer with low signal reflection band was discontinuous. The injury of cartilage is the key factor of benign airway stenosis. Acute injury of airway mucosa alone is unlikely to cause airway stenosis, but combined with cartilage injury may aggravate airway stenosis. EB-OCT can clearly identify the airway layers of rabbits, which is helpful to evaluate the damage of tracheal cartilage and mucosa. The diagnostic potential of this technique makes EB-OCT a promising approach for the study and monitoring of airway diseases.

First Characterization of the Transcriptome of Lung Fibroblasts of SSc Patients and Healthy Donors of African Ancestry

Systemic sclerosis (SSc) is a connective tissue disorder that results in fibrosis of the skin and visceral organs. SSc-associated pulmonary fibrosis (SSc-PF) is the leading cause of death amongst SSc patients. Racial disparity is noted in SSc as African Americans (AA) have a higher frequency and severity of disease than European Americans (EA). Using RNAseq, we determined differentially expressed genes (DEGs; q < 0.1, log2FC > |0.6|) in primary pulmonary fibroblasts from SSc lungs (SScL) and normal lungs (NL) of AA and EA patients to characterize the unique transcriptomic signatures of AA-NL and AA-SScL fibroblasts using systems-level analysis. We identified 69 DEGs in "AA-NL vs. EA-NL" and 384 DEGs in "AA-SScL vs. EA-SScL" analyses, and a comparison of disease mechanisms revealed that only 7.5% of DEGs were commonly deregulated in AA and EA patients. Surprisingly, we also identified an SSc-like signature in AA-NL fibroblasts. Our data highlight differences in disease mechanisms between AA and EA SScL fibroblasts and suggest that AA-NL fibroblasts are in a "pre-fibrosis" state, poised to respond to potential fibrotic triggers. The DEGs and pathways identified in our study provide a wealth of novel targets to better understand disease mechanisms leading to racial disparity in SSc-PF and develop more effective and personalized therapies.

Clinical, Histological, and Profibrotic Extracellular Matrix Protein Changes in a Model of Tracheal Stenosis Induced by Cervical Tracheal Autotransplantation

BACKGROUND

Tracheal stenosis (TS) is a complication of prolonged intubation, tracheotomy, and tracheal surgery that compromises the vascular supply. Animal models are essential for studying its pathophysiology and the effect of interventions.

OBJECTIVE

To establish a TS model in rats secondary to tracheal autotransplantation with a graft submerged in bleomycin (Atx-Bleo). Additionally, to evaluate the clinical and histological changes, as well as the expression of newly formed collagen (NFC), isoforms of transforming growth factor beta (TGFβ), fibronectin (FN), elastin (ELN), integrin β1 (ITGβ1), and matrix metalloproteinase 1 (MMP1) in TS.

METHODS

Twenty Wistar rats were divided into three groups: group I (n = 20) control; group II (n = 10) end-to-end anastomosis of the trachea (tracheoplasty); and group III (n = 10) Atx-Bleo. The animals were evaluated clinically, tomographically, macroscopically, morphometrically, and microscopically. NFC deposition, and the expression of profibrotic and antifibrotic proteins were evaluated in tracheal scars.

RESULTS

All animals survived the surgical procedure and the study period. Compared with the other study groups, the Atx-Bleo group developed TS and fibrosis, exhibited higher expression of NFC, TGFβ1, TGFβ2, FN, ELN, and ITGβ1, and mild expression of TGFβ3 and MMP1 (p < 0.005; analysis of variance, Dunnett and Tukey tests).

CONCLUSION

Atx-Bleo in TS model rats produces tomographic and histological changes, and induces the upregulation of profibrotic proteins (TGFβ1, TGFβ2, collagen, FN, ELN, ITGβ1) and downregulation of antifibrotic proteins (TGFβ3, MMP1). Therefore, this model may be used to test new pharmacological treatments for reversing or preventing TS, and conduct basic studies regarding its pathophysiology.

TGF beta -1, -2 and -3 in the modulation of fibrosis in the cornea and other organs

The TGF beta-1, -2 and -3 isoforms are transcribed from different genes but bind to the same receptors and signal through the same canonical and non-canonical signal transduction pathways. There are numerous regulatory mechanisms controlling the action of each isoform that include the organ-specific cells producing latent TGF beta growth factors, multiple effectors that activate the isoforms, ECM-associated SLRPs and basement membrane components that modulate the activity and localization of the isoforms, other interactive cytokine-growth factor receptor systems, such as PDGF and CTGF, TGF beta receptor expression on target cells, including myofibroblast precursors, receptor binding competition, positive and negative signal transduction effectors, and transcription and translational regulatory mechanisms. While there has long been the view that TGF beta-1and TGF beta-2 are pro-fibrotic, while TGF beta-3 is anti-fibrotic, this review suggests that view is too simplistic, at least in adult tissues, since TGF beta-3 shares far more similarities in its modulation of fibrotic gene expression with TGF beta-1 and TGF beta-2, than it does differences, and often the differences are subtle. Rather, TGF beta-3 should be seen as a fibro-modulatory partner to the other two isoforms that modulates a nuanced and better controlled response to injury. The complex interplay between the three isoforms and numerous interactive proteins, in the context of the cellular milieu, controls regenerative non-fibrotic vs. fibrotic healing in a response to injury in a particular organ, as well as the resolution of fibrosis, when that occurs.

Transforming growth factor-β in tissue fibrosis

TGF-β is extensively implicated in the pathogenesis of fibrosis. In fibrotic lesions, spatially restricted generation of bioactive TGF-β from latent stores requires the cooperation of proteases, integrins, and specialized extracellular matrix molecules. Although fibroblasts are major targets of TGF-β, some fibrogenic actions may reflect activation of other cell types, including macrophages, epithelial cells, and vascular cells. TGF-β–driven fibrosis is mediated through Smad-dependent or non-Smad pathways and is modulated by coreceptors and by interacting networks. This review discusses the role of TGF-β in fibrosis, highlighting mechanisms of TGF-β activation and signaling, the cellular targets of TGF-β actions, and the challenges of therapeutic translation.

A systematic review of simulated laryngotracheal reconstruction animal models

OBJECTIVES

Review of the literature to identify practical, high-fidelity, commercially available animal models for simulation training and surgical skills maintenance in laryngotracheal reconstruction (LTR).

METHODS

A systematic review of PubMed and Embase databases was conducted independently by two authors, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Search terms included "laryngotracheal reconstruction," "laryngotracheoplasty," "pig and larynx," "sheep and larynx," and "rabbit and larynx." Articles were then assessed, identifying model cost and availability, model validation, feasibility as a training tool, and verisimilitude to pediatric LTR.

RESULTS

In total, 79 articles were considered suitable for inclusion in the study, incorporating both in vitro and in vivo models. Models utilized included rabbit (n = 69), pig (n = 7), sheep (n = 1), and goat (n = 2). The rabbit model was similar in size to the neonate, but differences in laryngeal anatomy and cartilage texture made graft insertion difficult. The anatomy of the pig, sheep, and goat larynges more closely resembled the pediatric patient, allowing improved grafting, but corresponded more in size to that of an older child. Commercial availability of the pig and sheep was considered greatest, and was reflected in cost. None of the animal models identified in the literature have been validated as a simulation tool.

CONCLUSIONS

The rabbit, sheep and pig models seemed to demonstrate the greatest potential for use as advanced pediatric airway surgery simulation models, with the rabbit model being most utilized in the literature. However, as yet there have been no models formally validated as a simulation training tool. Laryngoscope, 129:235-243, 2019.

Effect of Fibrin Matrix and Vascular Endothelial Growth Factor on Reepithelialization of Orthotopic Murine Tracheal Transplants

To determine whether the administration of vascular endothelial growth factor (VEGF) alone and in combination with fibrin matrix accelerates murine tracheal allograft reepithelialization, we randomly assigned 40 age-matched mice to 5 experimental groups. BALB/c tracheal grafts were transplanted orthotopically into allogeneic C57BL/6 recipients. The recipients were immunosuppressed with cyclosporine (25 mg/kg per day) and treated with a single topical dose of fibrin matrix, a single topical dose of VEGF, or a single topical dose of a combination of VEGF and fibrin matrix. Thirty-five and 50 days after transplantation, a mixed lymphocyte reaction was performed to assess adequate immunosuppression and the grafts were assessed for rejection, rate and quality of allograft reepithelialization, and cartilage viability. The administration of a combination of fibrin matrix and VEGF to tracheal allografts demonstrated an increased rate of reepithelialization and increased density (37% ± 2.9%) of morphologically normal ciliated pseudostratified epithelium when compared with an immunosuppressed control group (29.3% ± 9.1%) 35 days after transplantation. The treated allografts demonstrated no significant change in cartilage viability or rejection. We conclude that the administration of fibrin matrix and VEGF to immunosuppressed tracheal allografts improves the rate and density of tracheal allograft reepithelialization. Carrier-bound growth factors may represent a novel approach to accelerating tracheal allograft reepithelialization and decreasing the need for prolonged immunosuppression following tracheal transplantation.

Outcomes from Cyanoacrylate Use in Tracheal Anastomosis in a Rat Model

OBJECTIVES

We aimed to investigate the histologic effects of N-butyl-2-cyanoacrylate (NBCA) and metacryloxisulfolane (MS) comonomer on tracheal anastomosis in vivo on a rat model of tracheal resection and end-to-end anastomosis.

STUDY DESIGN

Animal experiment. Rat model of tracheal resection and end-to-end anastomosis.

SETTING

Animal laboratory.

SUBJECTS AND METHODS

Tracheal resection and end-to-end anastomosis were performed in 28 Wistar albino rats. Rats were randomly divided into 2 groups: control (n = 14), in which anastomoses were performed with 8/0 Vicryl, and study (n = 14), in which NBCA and MS comonomer was used in addition to 8/0 Vicryl to perform anastomosis. Seven rats from each group were sacrificed on day 7 and the remaining on day 28 for gross and histologic examination.

RESULTS

Indurations at the site of anastomoses were detected in all rats of study group. Slight narrowing at the site of anastomosis was observed in 8 rats of the study group and in only 1 of the control group. The difference was significant on day 28 (P = .021). The inflammatory cell infiltration was significantly increased in the study group on day 28 (P = .022). Epithelial regeneration was found to be worse in the study group on day 28 (P = .022).

CONCLUSIONS

The use of NBCA and MS comonomer increased the inflammation in rat tracheal anastomosis with respect to inflammatory cell count and epithelial regeneration. So the use of NBCA and MS comonomer in tracheal surgery cannot be recommended yet in the light of our data.

Induction of tracheal stenosis in a rabbit model-endoscopic versus open technique

OBJECTIVE

To evaluate and compare open versus endoscopic methods of inducing tracheal stenosis in the New Zealand white rabbit model.

STUDY DESIGN

Prospective randomized control, pilot study.

SUBJECTS AND METHODS

Fifteen New Zealand white rabbits were used in the study. Induction of tracheal stenosis was performed through an open incision in 6 rabbits, an endoscopic approach was utilized in 8 rabbits, and 1 rabbit served as the control. The open approach was performed by brushing the tracheal mucosa 10 times through an anterior tracheotomy with a nylon brush. The endoscopic method was achieved using a rigid bronchoscope and at a measured distance below the cricoid cartilage, passing the same nylon brush four times in each of four quadrants. Repeat endoscopies for evaluation of stenosis progression were performed at 2 and 3 weeks on all rabbits.

RESULTS

In the open group, we observed no stenosis with one mortality as a result of gastroenteritis due to antibiotic use. In the endoscopic group, all animals achieved some degree of stenosis by 14 days, with a mean airway narrowing of 43%. The two deaths in the endoscopic group occurred in the immediate postoperative period secondary to laryngeal edema. The endoscopic procedure was 5 minutes in duration.

CONCLUSION

The endoscopic technique is an effective method of achieving circumferential tracheal stenosis in the rabbit model. Advantages include simple instrumentation, an endoscopic approach, potential for decreased costs, and more reliable results.

The effect of prophylactic dose of a low molecular weight heparin on skin wound healing of rats

PURPOSE: To investigate the effect of prophylactic dose of a low molecular weight heparin, enoxaparin, on skin wound healing of rats. METHODS: Forty rats were used for the study. Rats were randomly assigned to two equal groups. Experimental group received prophylactic dose of enoxaparin. Physiologic saline was administered to the control group. Parameters of wound healing of experimental and control groups were compared. For comparison of the groups in terms of fibrosis, vascularization, inflammation, epithelization, and tensile strength test (Newton). Mann-Whitney-U test was used because variables were categorical data (fibrosis, vascularization, inflammation and epithelization). Differences between groups were analyzed with independent samples t-test (tensile strength). Significance was set at p<0.05. RESULTS: Skin wound of the experimental group presented tensile strength significantly decreased (p<0.001), histopathologic examination revealed a significant (p<0.001) delayed epithelization and decreased in fibrosis, vascularization, inflammation (p<0.001) in the experimental group. CONCLUSION: Enoxaparin delay wound healing by decreased inflammatory cells, fibroblast contents and their products (growth factors), and by promoted hemorrhage.

Transforming growth factor-beta in allergic inflammatory disease of the upper airways: friend or foe?

TGF-beta is a multi-functional cytokine with a huge array of effects on a variety of cell types. It is rapidly emerging as a key major player in the way the airway epithelium behaves and its ability to repair itself. This is not only of relevance to allergic airway diseases such as asthma and allergic rhinitis, which are increasing in prevalence worldwide, but in many other diseases. The full impact any disruption of TGF-beta signalling may have in the development and persistence of allergic inflammatory airway diseases is yet to be fully realized and remains the subject of ongoing research. There has been a recent revival of interest in the role of regulatory T cells in controlling allergic inflammation. Evidence is emerging of a significant contribution by TGF-beta to this regulatory process. This review aims to summarize current knowledge relating to TGF-beta in relation to allergic inflammatory upper airways disease, and attempts to clarify some of the discrepancies and inconsistencies in this area. It also considers the therapeutic implications of novel TGF-beta therapy, including potential future applications in the treatment of nasal polyposis and reduction of post-operative scar tissue formation following endoscopic sinus surgery.

Avaliação da resposta inflamatória traqueal ao curativo de celulose bacteriana após escarificação cirúrgica em coelhos

Dentre as causas de insucesso nas cirurgias para a estenose traqueal está a formação de tecidos de cicatrização exuberantes. O uso de curativos para evitar esta reação pode ser de grande valia nestes casos. A celulose bacteriana produzida por acetobacter xylinun pode ser útil nestes casos. Não há estudos na região laringotraqueal. OBJETIVO: Avaliar a resposta tecidual subglótica de coelhos após escarificação e colocação de curativo de celulose, comparando com grupo controle. FORMA DE ESTUDO: Experimental MATERIAL E MÉTODOS: Foram estudados 26 coelhos, submetidos a escarificação da região laringotraqueal e tratados com curativo e comparados com controle. Foram estabelecidos 4 tempos de seguimento. Os seguimentos laringotraqueais foram examinados histologicamente e os resultados foram avaliados estaticamente. RESULTADOS: O grupo de estudo evoluiu com o passar do tempo com resultados estatisticamente semelhantes ao do grupo controle, nos parâmetros Congestão vascular, Exsudato purulento, Inflamação aguda, Integridade do epitélio, Proliferação fibrosa e Reação granulomatosa. CONCLUSÃO: Não foram observadas diferenças entre os grupos controle e de estudo quanto aos parâmetros inflamatórios ou cicatriciais. Não houve sinais inflamatórios relacionados ao uso da membrana de celulose que não tivessem ocorrido devido ao traumatismo cirúrgico.

Tracheal inflammatory response to bacterial cellulose dressing after surgical scarification in rabbits

Exuberant scarring tissue formation is among the failure causes of tracheal stenosis surgery. Dressings that could avoid such reaction could be very helpful in these cases. Bacterial cellulose, produced by acetobacter xylinun can be useful in these cases. There are no studies in the laryngotracheal region.

Aim

to assess subglottic tissue response in rabbits after scarification and placement of cellulose dressing, and comparing it to a control group.

Study design

experimental.

Materials and Methods

26 rabbits underwent laryngotracheal scarification, received the dressing and were compared to the control group. We established four follow up periods. Laryngotracheal specimens underwent histological exam and the results were statistically assessed.

Results

the study group had statistically similar results when compared to the control group in the following parameters: vascular congestion, purulent oozing, acute inflammation, epithelial integrity, fibrous proliferation and granulous proliferation.

Conclusion

we did not observe differences between the study and control groups as far as inflammation and scarring are concerned. There were no inflammatory signs associated with the use of the cellulose membrane that did no occur because of surgery.

The effects of granulocyte colony-stimulating factor on the healing of tracheal anastomosis following radiation therapy in rats

OBJECTIVE

This study evaluates the effects of granulocyte colony-stimulating factor on the healing of tracheal anastomosis following radiation therapy in rats.

METHODS

Fifty-six male Wistar rats were divided into four groups. Group 1 underwent tracheal anastomosis. Group 2 underwent radiation therapy followed by tracheal anastomosis. Group 3 underwent radiation therapy followed by tracheal anastomosis and received granulocyte colony-stimulating factor. Group 4 underwent sham radiation therapy followed by sham tracheal anastomosis. At 10 days following radiation therapy, the trachea was dissected for histopathological, mechanical and biochemical evaluation.

RESULTS

Median scores for inflammation were three points for Group 1, two points for Group 2, two points for Group 3 and one point for Group 4. Median scores for angiogenesis were four points for Group 1, two points for Group 2, three points for Group 3 and one point for Group 4. Median scores for connective tissue regeneration were four points for Group 1, two points for Group 2, three points for Group 3 and one point for Group 4. Median scores for epithelial regeneration were two points for Group 1, one point for Group 2, one point for Group 3 and one point for Group 4. Mean anastomotic bursting pressures were 853 mmHg for Group 1, 293 mmHg for Group 2, 417 mmHg for Group 3 and 966 mmHg for Group 4. Mean hydroxyproline concentrations were 159 microg/mg for Group 1, 177 microg/mg for Group 2, 120 microg/mg for Group 3 and 117 microg/mg for Group 4.

CONCLUSIONS

This study suggests that granulocyte colony-stimulating factor contributes to the healing of tracheal anastomosis following radiation therapy through improved connective tissue regeneration.

Cross-linked hyaluronan-coated stents in the prevention of airway stenosis

OBJECTIVE

This project studies the use of airway stents coated with a cross-linked derivative of hyaluronan (HA) in a rabbit airway model of subglottic stenosis (SGS).

STUDY DESIGN AND SETTING

An acute subglottic mucosal injury and airway stent placement design were used in a rabbit model. Thirty-six rabbits were randomized to 6 different study groups. Four groups had the subglottic mucosa denuded at the cricoid, and 2 groups received no injury. Airway stents coated with Carbylan-SX, a cross-linked derivative of HA, and controls were placed for 3 weeks. After sacrifice at 6 weeks, morphometric measurements of subglottic lumen were taken.

RESULTS

In posttraumatic models, no significant differences were seen in airway area measures between groups (P = 0.86). In non-injury groups, a significant difference between Carbylan-SX versus non-HA-derivative-coated stents was seen (P = 0.05).

CONCLUSION

In this model of acute subglottic mucosal injury, the HA-derivative-coated stent did not improve healing. However, in the absence of mucosal injury, the Carbylan-SX film-coated stent yielded significantly larger airway areas compared with a noncoated stent.

SIGNIFICANCE

Stents or endotracheal tubes coated with a cross-linked derivative of HA may prevent stenosis in patients without airway injury but require long-term intubation or laryngotracheal stenting.

High-Level Expression of Matrix-Associated Transforming Growth Factor-β 1 in Benign Airway Stenosis

STUDY OBJECTIVES

Acquired tracheal and subglottic stenosis frequently leads to severe airway narrowing, which requires repeated interventions, such as dilatation, laser resection, stent implantation, or surgery. To get a more detailed insight into the pathogenesis of this condition, we investigated the expression of profibrotic cytokines and the proliferation of the airway wall in benign human airway stenoses.

METHODS

Specimens from patients with subglottic and tracheal stenosis and stent-related stenoses were obtained (n = 20) for reverse transcription (RT) polymerase chain reaction (PCR) analysis and immunohistochemistry testing.

RESULTS

Transforming growth factor (TGF)-beta1 messenger RNA expression was significantly increased in biopsy specimens from stent-related stenoses compared to nonstenotic control sections. In contrast, TGF-beta3 and interleukin-1beta showed no such differences in messenger RNA expression. Immunohistochemistry revealed a strong matrix-associated, subepithelial expression of TGF-beta1 in tracheal stenosis. Proliferating Ki-67-positive cells were mainly localized in the basal epithelial layer. Only 2 of 16 patients with tracheal stenoses and 3 of 4 patients with stent-related stenoses showed a weak expression of Ki-67-positive cells in the subepithelium. Furthermore, TGF-beta1 dose-dependently enhanced the proliferation of human lung fibroblasts in vitro, even in the presence of mitomycin-C.

CONCLUSION

While a weak subepithelial proliferation occurs in stent-related stenoses, the dominant factor in late stages of untreated tracheal stenoses seems to be the high-level expression of TGF-beta1 and the deposition of extracellular matrix.

The effects of estradiol and progesterone on the synthesis of collagen in tracheal surgery

OBJECTIVE

Estrogen and progesterone have the decreasing effect on massive collagen synthesis in wound healing. Here, it is aimed to determine their decreasing effect on collagen accumulation and fibroblast proliferation in trachea histologically and to understand if they would be protective for tracheal stenosis.

METHODS

Thirteen male Winstar rats were divided randomly into two groups: estrogen-progesterone group (group 1, eight rats) and control group (group 2, five rats). Under general anesthesia, tracheas were incised vertically extending from second to fifth tracheal ring. Incision was closed with absorbable sutures. Estrodiol benzoat and progesterone was given intramuscularly to estrogen progesterone group, saline solution to control group. After 4 weeks they were sacrificed and tracheas were excised. Horizontal cross section of the narrowest part of the incised trachea was examined histologically. Epithelial regeneration, inflammatory cell infiltration, angiogenesis, fibroblast proliferation and collagen deposition were evaluated by histological grading.

RESULTS

Statistically significant difference was found between the groups in collagen deposition and fibroblast proliferation (p=0.011, <0.05). For epithelial regeneration, inflammatory cell infiltration, and angiogenesis there was no difference.

CONCLUSION

As a result, it was proved that sex hormones inhibit massive collagen deposition and fibroblast proliferation in wound healing of tracheal surgery. Hence, they may prevent tracheal stenosis.

Comparison of the effectiveness of gene therapy with transforming growth factor-beta or extracorporal shock wave therapy to reduce ischemic necrosis in an epigastric skin flap model in rats

The induction of neoangiogenesis by exogenous growth factors in failing skin flaps has recently yielded promising results. Gene transfer with virus vectors has been introduced as a highly capable route of administration for growth factors, such as vascular endothelial growth factor or fibroblast growth factor. Extracorporal shock waves (ESW) deliver energy by means of high amplitudes of sound to the target tissue and have been shown to induce angiogenesis. We compared the effectiveness of gene therapy with adenovirus-mediated transforming growth factor-beta (TGF-beta) and ESW therapy to treat ischemically challenged epigastric skin flaps in a rat model. Thirty male Sprague-Dawley rats were divided into three groups of 10 each with an 8 x 8 cm epigastric skin flap. Rats received either subdermal injections of adenovirus (Ad) encoding TGF-beta (10(8) pfu) or ESW treatment with 750 impulses at 0.15 mJ/mm2. The third group received no treatment and served as a control group. Flap viability was evaluated after 7 days and digital images of the epigastric flaps were taken and areas of necrotic zones relative to total flap surface area calculated. Histologic evaluation and increased angiogenesis were confirmed by CD31 immunohistochemistry. Overall, there was a significant increase in mean percent surviving area in the Ad-TGF-beta group and the ESW group compared to the control group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0% and control group: 82.6 +/- 4.3%; p < 0.05). Furthermore, in the ESW group mean percent surviving areas were significantly larger than in the Ad-TGF-beta group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0%; p < 0.05). Flap vascularization was increased by Ad-TGF-beta and ESW with numerous vessels, however, there was no significant difference between the two treatment groups. We conclude that treatment with ESW enhances epigastric skin flap survival significantly more than Ad-TGF-beta treatment and thus represents a modality that is feasible, cost-effective, and less invasive compared to gene therapy with growth factors to improve blood supply to ischemic tissue.

The effects of single-dose dexamethasone on wound healing in rats

Dexamethasone effectively decreases the incidence of nausea and vomiting among pediatric and adult patients. In this study, we evaluated the effects of single-dose dexamethasone on wound healing in a prospective, randomized, experimental animal model. Anesthesia was induced with thiopental 100 mg/kg intraperitoneally. Dexamethasone 1 mg/kg was administered intraperitoneally in a dexamethasone group, and physiological saline was administered in a control group. Collagenization, epithelization, and fibroblast content were significantly less in the dexamethasone group compared with the control group (P values of 0.002, 0.041, and 0.023, respectively). The vascularity and the degree of inflammatory cells were more intense in the dexamethasone group compared with the control group (P values of 0.023 and 0.002, respectively). The white blood cell count was similar in the control (7.84 +/- 2.09) and dexamethasone (6.98 +/- 2.12) groups. The mean hydroxyproline level was 0.72 +/- 0.13 mg/g in the dexamethasone and 1.03 +/- 0.19 mg/g in the control group. Hydroxyproline levels were significantly less in the dexamethasone group (P = 0.001). We conclude that dexamethasone at 1 mg/kg may have negative effects on wound healing.

IMPLICATIONS

We evaluated the effects of dexamethasone on wound healing in a prospective, randomized, experimental animal model. Our results show that dexamethasone at 1 mg/kg may have negative effects on wound healing.

The effects of corticosteroids and vitamin A on the healing of tracheal anastomoses

OBJECTIVE

This study investigates the deleterious effects of corticosteroids on tracheal anastomotic healing and the ability of vitamin A to reverse these effects in a rat model.

METHODS

Forty-two adult Wistar rats were randomly divided into five groups. The animals underwent tracheal transection and primary anastomoses. The groups were assigned as follows: Group I, sham (N=6); Group II, control (N=6); Group III, dexamethasone, 0.1 mg/kg/day intramuscularly (N=10); Group IV, dexamethasone 0.1 mg/kg/day intramuscularly+vitamin A 10000 IU/kg/day by gavages (N=10); and Group V, vitamin A 10000 IU/kg/day by gavages for a week (N=10). After 7 days, anastomotic healing was assessed by measurement of bursting pressure, hydroxyproline content and subsequent histological grading using the modified Ehrlich/Hunt scale.

RESULTS

Bursting pressures and hydroxyproline contents were as follows: Group I: 977+/-8 mmHg and 11.80+/-0.3 microg/mg (mean+/-standard error of the mean); Group II: 890+/-55 mmHg and 9.93+/-0.6 microg/mg; Group III: 555+/-26 mmHg and 11.90+/-1.3 microg/mg; Group IV: 873+/-73 mmHg and 10.24+/-2.2 microg/mg; Group V: 905+/-45 mmHg and 7.51+/-0.8 microg/mg, respectively. Bursting pressure of Group III was found to be significantly lower when compared to other groups (P<0.0001). However, statistical significance was not found among the study groups for the hydroxyproline content. Except for inflammatory cell infiltration, histological parameters including epithelial regeneration, fibroblast proliferation, collagen content, and angiogenesis demonstrated significant differences among the groups.

CONCLUSION

The present study demonstrates that dexamethasone significantly impairs the healing of tracheal anastomoses in rats and postoperative administration of vitamin A appreciably reverses this inhibitory effect. Patients receiving corticosteroids may benefit from vitamin A when undergoing prolonged intubation and laryngotracheal reconstruction.

The effects of corticosteroids on the healing of tracheal anastomoses in a rat model

The deleterious effects of corticosteroids on anastomotic healing have been widely demonstrated in various tissues. This study is designed to investigate the effects of corticosteroids on the healing of tracheal anastomoses. Forty-two adult female Wistar rats, randomly divided into five groups, underwent tracheal transection and primary anastomoses. The groups were assigned as follows: Group I, sham, ( N= 6); Group II, control, ( N= 6); Group III, dexamethasone, 0.1 mg kg (-1) per day, intramuscularly for a week ( N= 10); Group IV, dexamethasone, 1 mg kg (-1) per day, intramuscularly for a week (N= 10); Group V, dexamethasone, 6 mg kg (-1) intramuscularly as a single dose ( N= 10). After 7 days, anastomotic healing was assessed by measurement of bursting pressure and hydroxyproline content. Histological examination was performed according to the modified Ehrlich/Hunt scale. The bursting pressure was significantly decreased in Group III and Group IV when compared to the control group (P< 0.0001 for both groups). There was also significance between the bursting pressures of Group III and Group IV (P< 0.01). However, the difference failed to reach significance between Group V and the control group. The reduction of bursting pressure was not reflected in diminished hydroxyproline content. The hydroxyproline content of the study groups (GIII, GIV and GV) were not statistically different compared with the control group. Except for inflammatory cell infiltration, histological parameters including epithelial regeneration, fibroblast proliferation, collagen content, and angiogenesis also demonstrated significant differences among the groups (P< 0.05). The present study demonstrates that daily administration of dexamethasone for a week significantly impairs the healing of tracheal anastomoses in a dose-dependent manner while a single-dose postoperatively does not affect the healing process.