Inhibition of subglottic stenosis with mitomycin-C in the canine model

Critical Stenosis Because of Vocal Cord Synechiae in a Child

Stridor is a clinical sign of an underlying disease and a common reason for pediatric emergency department (PED) consultation. Patients presenting with stridor must be evaluated to determine the origin of this abnormality. We present the case of a 7-year-old female patient who presented to our Pediatric Emergency Department with a history of recurrent episodes of stridor with increasing frequency over the previous 4 years, for this reason she was previously admitted to the pediatric intensive care unit. Findings from the otorhinolaryngologic assessment with flexible fiber-optic endoscopy led to a diagnosis of congenital synechia of the vocal cords. The cervical CT scan evidenced critical stenosis of the airway. An initial cordectomy and placement of a silicone device for fixation were performed. Subsequently, the patient required 6 additional interventions for progressive dilation of the glottic space at the level of the vocal cords and injections of mitomycin C injections (an antineoplastic that inhibits collagen proliferation). This case highlights the importance of additional studies (especially examination of the upper airway) when atypical or recurrent findings are revealed by the clinical history, physical examination, or disease course in patients with croup to prioritize cases severe enough to require pediatric intensive care unit admission.

The effects of steroidal and non-steroidal anti-inflammatory drugs on tracheal wound healing in an experimental rat model

OBJECTIVES

The effect of non-steroidal anti-inflammatory drugs (NSAID), mostly used for postoperative analgesic purposes for wound healing, is still a matter of debate. Our goal was to evaluate the effects of the most widely used NSAID and corticosteroids after surgical operations on tracheal wound healing in an experimental rat model.

METHODS

Thirty-nine male Wistar albino rats were included in this study. Tracheotomy was performed in 32 rats; then they were divided into 3 groups. After the first day, the animals in group 1 were treated with an NSAID (diclofenac 10 mg/kg/day) (NSAID, n = 12) for 7 days; the animals in group 2 were treated with a corticosteroid (dexamethasone, 2 × 0.1 mg/kg/day) (steroid, n = 10) for 7 days; the animals in group 3 (control, n = 10) were not given any medications. For a fourth group (histological control, n = 7), in order to evaluate normal morphological and histological characteristics, neither surgery nor medication was used. Five rats were eliminated from the study (2 rats in the NSAID group died and 3 rats in the steroid group developed local wound infections). The drop-out rate was 12.8%. Histological characteristics, inflammation, fibrosis, necrosis, neochondrogenesis, neovascularization and epithelization were evaluated in 34 rats. Non-parametric tests were used for statistical analysis.

RESULTS

Inflammation, vascularization and number of fibroblasts and chondrocytes were significantly higher in the control group than in the histological control group. There was some reduction in all parameters except vascularization in the NSAID group (P > 0.05). When the steroid group was compared to the NSAID group, inflammation (P < 0.05), vascularization and number of chondrocytes (P > 0.05) were more suppressed in the steroid group. The number of fibroblasts increased in the steroid group (P > 0.05).

CONCLUSIONS

Steroids and NSAID may have negative effects on tracheal wound healing, probably by suppressing inflammation and fibroblast proliferation. NSAID was mostly used postoperatively for analgesic purposes and should be avoided.

Subglottic Stenosis in Children: Preliminary Experience from a Tertiary Care Hospital

INTRODUCTION

This retrospective study describes our experience in the evaluation and management of infants with subglottic stenosis.

MATERIALS AND METHODS

The study included 10 patients aged between 1 wk and 18 months with 6 cases having congenital subglottic stenosis and 4 cases having acquired subglottic stenosis.

RESULTS

6 patients had grade I, 3 patients had grade II, and 1 patient had grade III subglottic stenosis. Tracheostomy was required in 4 patients at the time of presentation. 7 patients were treated successfully with Bougie dilation followed by topical application of mitomycin, whereas 1 patient who failed to serial dilation needed open reconstructive procedure. Laser excision of the anterior subglottic web was performed in one patient. Another patient with underlying cerebral palsy could not be operated upon and was managed with tracheostomy.

CONCLUSION

Subglottic stenosis may be effectively man-aged with endoscopic surgical techniques, although the number of such sittings required varies with the type and severity of stenosis. Open surgical procedures need to be individualised as per the needs of the patient only after all the other endoscopic possibilities have been exhausted.

Mitomycin C in the endoscopic treatment of tracheal stenosis: a prospective cohort study

Objective:

To evaluate the efficacy of mitomycin C (MMC) in the endoscopic treatment of tracheal stenosis.

Methods:

Patients with laryngotracheal, tracheal, or tracheobronchial stenosis were treated with dilation and topical MMC. The inclusion criteria were as follows: being ineligible for surgery (for medical reasons) at the time of evaluation; membranous stenosis responding well to dilation; and postoperative stenosis at the anastomosis site. Etiology of stenosis and indication for treatment with MMC, as well as site, length, and percentage of stenosis, together with presence of tracheostomy and duration of follow-up, were analyzed. The outcomes evaluated were symptom-free interval ≥ 12 months, number of dilations with topical application of MMC, and complications.

Results:

Twenty-two patients (15 men and 7 women) were treated between 2003 and 2010. Stenosis was due to endotracheal intubation in 15 patients and surgery in 8. Pure tracheal stenosis was encountered in 13 patients, subglottic stenosis was encountered in 4, tracheobronchial stenosis was encountered in 3, and complex stenosis was encountered in 2. The length of stenosis ranged from 0.5 cm to 2.5 cm, and the percentage of stenosis ranged from 40% to 100%. Nine patients had undergone tracheostomy and had a Montgomery T-tube in situ. Treatment was successful in 14 patients, who remained free of symptoms for at least 12 months. The number of topical applications of MMC ranged from 1 to 5, and complications included fungal infection, keloid scarring, granuloma, and mediastinal emphysema.

Conclusions:

MMC appears to be effective in the endoscopic treatment of tracheal stenosis.

Role of Topical Medication in Prevention of Post-extubation Subglottic Stenosis

Iatrogenic laryngotracheal injury is the most serious complication of endotracheal intubation since this method of establishing airway was first described by Eugene Bouchut in 1858. Even today, subglottic stenosis is the most dreaded complication of intubation. This animal study is focused on the host tissue response to intubation induced injury resulting in subglottic stenosis and methods to prevent this complication. To assess the role of topically applied Mitomycin-C and Triamcinolone Acetonide in wound healing process following post-extubation subglottic injury. Prospective Randomized block, single-blinded, experimental study. Forty New-Zealand white rabbits where block randomized and allocated into 4 groups based on the type of topical medication that was applied post-extubation. Further these groups where subdivided into 3 subgroups based on the time of sacrifice (4, 6 and 12 weeks) to study the histopathological changes that occurred in a temporal sequence at the subglottis. It was observed that the rabbits in the control group and those that received Mitomycin-C only had more respiratory distress compared to those treated with Triamcinolone Acetonide. Statistically significant histopathological changes were observed in all the 4 groups. Mitomycin-C applied topically did not alter the wound healing process following post-extubation injury in the subglottis. Triamcinolone Acetonide significantly altered wound healing in the subglottis and prevented occurrence of respiratory distress.

The use of injectable calcium hydroxylapatite in the surgically pretreated larynx with glottal insufficiency

OBJECTIVES/HYPOTHESIS

To evaluate the efficacy of vocal fold (VF) augmentation with calcium hydroxylapatite (CaHA) microspheres in the surgically pretreated larynx with glottal insufficiency.

STUDY DESIGN

Prospective clinical pilot study.

METHODS

After several prior reconstructive attempts (following tumor resection, VF paralysis, in sulcus vocalis, and VF scarring), CaHA was injected under general anaesthesia using a transoral microlaryngoscopic approach in 10 patients with residual glottal insufficiency ≤1.5 mm. The postinterventional result was assessed after 1 day, and 1 and 3 months. Evaluation of augmentation comprised intraoperative video/photo documentation, pre-/postoperative videolaryngostroboscopy, as well as established subjective and objective voice function diagnostics (Grade, Roughness, Breathiness [GRB] Scale; Voice Handicap Index; voice range profile; and acoustic-aerodynamic analysis).

RESULTS

In the pretreated VF with no or minimal lamina propria remaining, the exact placement of CaHA was not possible due to unpredictable propagation into the scarred tissue. The results showed an insufficient postoperative augmentation. Accordingly, the voice function did not improve. However, a significant increase of the vocal range from 6.2 ± 3.2 to 8.7 ± 3.9 semitones was observed in the speaking voice profile (P =.02). All other acoustic and aerodynamic parameters remained on the whole unchanged; the slight differences between pre- and postoperative findings were not significant.

CONCLUSIONS

The application of CaHA in the surgically pretreated scarred larynx is not reliable to achieve a sufficient glottal closure and a satisfactory improvement of voice. Though CaHA is a welcome addition to our armamentarium against glottal insufficiency, the suitability for augmentation of scar tissue in the larynx must be considered carefully in each individual case.

LEVEL OF EVIDENCE

4 Laryngoscope, 127:1125-1130, 2017.

Refining indications for the use of mitomycin C using a randomized controlled trial with an animal model

Objectives

To evaluate the effect of mitomycin on the repair of acquired subglottic stenosis and to define the optimal concentration of mitomycin that would minimize restenosis after repair.

Study Design And Setting

A randomized prospective model was used in which 20 ferrets ( Mustela putorius furo) underwent simulated intubation injury that was then treated with CO2 laser lysis.

Results

Comparison of cross-sectional airway areas, after stenosis repair, showed no significant differences between control and mitomycin treatment groups. Comparison of histologic scores for both inflammation and mucosalization yielded no difference between control and treatment animals.

Conclusions

Mitomycin C appeared to have no benefit when placed after repair of an acquired stenosis.

Significance

This study closely models the injury experienced by children with acquired subglottic stenosis. These data provide clear evidence that mitomycin is limited in its effect on established wounds and help further define its role as an adjuvant for surgery in the aerodigestive tract.

Benefits and risks of mitomycin use in the traumatized tracheal mucosa

Objective

To investigate the efficacy and early complications of mitomycin C (MMC) in tracheal wound models.

Study Design and Setting

Rabbits (N = 60) were randomized to undergo mucosal injuries to the upper and lower trachea including anterior 120° full thickness (group A, n = 20), anterior 120° partial thickness (group B, 20), and circumferential partial thickness (group C, 20). In each rabbit, the wounds were separately treated with MMC 1.0 mg/mL or saline, and the animals were sacrificed after three weeks.

Results

Twenty-seven of the 60 animals experienced early death because of tracheal rupture or airway obstruction caused by unresolved scabs on the preinjured tracheal mucosa; the incidence of early death was higher in groups A and C than in group B. In each group, the degree of tracheal stenosis was comparable in wounds treated with MMC and saline.

Conclusion

These findings suggest that topical MMC has no benefit when used to prevent tracheal stenosis. Acute airway obstruction may occur in MMC-treated rabbits with tracheal wounds.

Bilateral Superior Labial Mucosal Transposition Flaps to Correct Stenosis of the Nares Following Bilateral Rostral Maxillectomy Combined with Nasal Planum Resection in a Dog

OBJECTIVE

To describe a technique using labial mucosal flaps to correct stenosis of the nares subsequent to bilateral rostral maxillectomy and nasal planum resection.

STUDY DESIGN

Case report

ANIMALS

Client-owned dog.

METHODS

A 10-year-old, neutered male Golden Retriever developed repeated stenosis of the nares, at first after bilateral rostral maxillectomy and nasal planum resection, and again after revision surgery. Bilateral, superior labial mucosal transposition flaps were created and interpolated between the nasal mucosa and skin after debridement of scar tissue.

RESULTS

The stenosis did not recur after mucosal flap transposition and the dog returned to normal quality of life (last follow-up 25 months postoperative).

CONCLUSION

Single-stage, superior labial mucosal transposition flaps can be used to correct nares stenosis subsequent to previous surgery.

Favorable vocal fold wound healing induced by platelet-rich plasma injection

OBJECTIVES

To introduce a new injection material for vocal fold diseases, which could be readily translated to clinical practice, we investigated the effectiveness of platelet-rich plasma (PRP) injection on the injured vocal fold in terms of histological recovery.

METHODS

Blood samples were drawn from New Zealand White rabbits and PRP was isolated through centrifugation and separation of the samples. Using a CO2 laser, we made a linear wound in the 24 vocal fold sides of 12 rabbits and injected each wound with PRP on one vocal fold side and normal saline (NS) on the other. Morphologic analyses were conducted at 2, 4, and 12 weeks after injection, and inflammatory response, collagen deposit, and changes in growth factors were assessed using H&E and masson trichrome (MT) staining and western blot assay.

RESULTS

PRP was prepared in approximately 40 minutes. The mean platelet concentration was 1,315,000 platelets/mm(3). In morphological analyses, decreased granulation was observed in the PRP-injected vocal folds (P<0.05). However, the irregular surface and atrophic change were not difference. Histological findings revealed significant inflammation and collagen deposition in NS-injected vocal folds, whereas the PRP-injected vocal folds exhibited less (P<0.05). However, the inflammatory reaction and fibrosis were not difference. In western blot assay, increased amounts of growth factors were observed in PRP-injected vocal folds.

CONCLUSION

Injection of injured rabbit vocal folds with PRP led to improved wound healing and fewer signs of scarring as demonstrated by decreased inflammation and collagen deposition. The increased vocal fold regeneration may be due to the growth factors associated with PRP.

Synthesis of a novel CS-g-MMCs conjugate and the inhabitation on the proliferation of Tenon's capsule fibroblasts in vitro

A novel anti-proliferative macromolecular conjugate, CS-g-MMCs, was synthesized in order to decrease the cytotoxicity of Mitomycin C (MMC) which was a traditional anti-proliferative agent of fibroblast in trabeculectomy. The structure of CS-g-MMCs was characterized by (1)H NMR, FT-IR spectroscopy and GPC analysis. The grafting degree (dg) of MMC onto chitosan (CS) was determined to be in the range of 2.8-11.3%, which could be controlled by variation of the molar ratios of MMC to oxidized chitosan (CS-CHO). In the drug release profiles of CS-g-MMCs in vitro, an initial burst followed by slow leakage was observed, and addition of acid or lysozyme obviously accelerated the MMC release. The MTS assay indicated that CS-CHO of 8 mg/ml has no cytotoxicity against human Tenon's capsule fibroblasts (HTCFs). The inhibition of HTCFs proliferation by CS-g-MMCs increased along with increasing the dg of conjugate. The CS-g-MMCs also caused the apoptosis of HTCFs and interfered in the active DNA synthesis in HTCFs. Furthermore, the expression of a-SMA at gene and protein levels were obviously lower when HTCFs were treated with CS-g-MMCs, as compared to MMC or blend of MMC/CS-CHO (p<0.05). Our results primarily demonstrated that the CS-g-MMCs conjugates have low cytotoxicity and have the effect to inhibit fibroblast proliferation.

Mitomycin C in Revision Endoscopic Dacryocystorhinostomy: A Prospective Randomized Study

Background

Endoscopic dacryocystorhinostomy (EN-DCR) is an effective and safe procedure when treating saccal and postsaccal nasolacrimal duct obstruction. However, sometimes scarring of the rhinostomy site caused by fibrosis may occur, particularly in revision operations. The application of intraoperative mitomycin C (MMC), an antiproliferative agent, has been introduced as one possible technique to improve the outcome. We conducted a prospective, randomized study to evaluate if the use of MMC improves the success in endonasal revision DCR procedure.

Methods

Thirty revision EN-DCR procedures were performed during 2004–2010. The patients were randomized into two study groups, according to whether the intraoperative MMC was used or not. The technique of EN-DCR procedure in both groups was the same, but in the MMC group, at the end of the procedure a piece of tampon soaked in MMC (0.4 mg/mL) was placed into the rhinostoma for 5 minutes. No silicone stents were inserted. The surgical outcome at the 6-month follow-up visit was considered successful if the lacrimal sac irrigation succeeded and if the patients’ symptoms were relieved.

Results

The success rate after revision EN-DCR with MMC was 93% and without MMC was 60%. The overall success rate was 77%. The difference between the two groups was not statistically significant (p = 0.08). The relief of the symptoms between groups in both the Nasolacrimal Duct Obstruction Symptom Score and ocular symptoms was statistically significant (p = 0.007 and p = 0.02, respectively).

Conclusion

The results of our study indicate that the application of intraoperative mitomycin C may improve the outcome in revision EN-DCR.

Laser and topical mitomycin C for management of nasal synechia after FESS: a preliminary report

The objective of the study is to assess the role of diode laser coupled with topical mitomycin C (MMC) in the management of synechia after endoscopic sinus surgery. Twenty-five patients with recurrent sinusitis due to synechia between the middle turbinate and lateral nasal wall after endoscopic sinus surgery were included in this study. Diode laser was used to divide the synechia and MMC was applied topically in the area of the middle meatus for 5 min. Patients were followed for 6 months to assess symptoms improvement, recurrence of synechia and CT scan changes. Most of our patients reported improvement of their symptoms, recurrent synechia occurred in 15% of the patients with significant improvement of the CT scan findings. In conclusion, the diode laser with topical MMC is an outpatient procedure which is simple, safe and effective in managing postoperative nasal synechia.

[Bronchoscopic dilation techniques and topical application of mitomycin-C in the treatment of tracheal stenosis post intubation - two case reports]

Tracheal stenosis follows any injury to the airway mucosa, such as ischaemic, traumatic and other injuries. The treatment of tracheal stenosis remains a challenging problem despite all the advances in endoscopic and surgical techniques. Scar formation and reestenosis are the main causes of treatment failure. The authors present two cases of successful treatment of a tracheal stenosis after tracheal injury from prolonged oro -tracheal intubation / tracheostomy following dilatation with rigid broncoscope and laser therapy, associated with topical application of mitomycin C as an adjuvant treatment.

Angiogenesis, fibrinogenesis and presence of synechiae after exeresis of a swine vocal fold mucosal microflap and use of topical mitomycin-C

PURPOSE: To evaluate swine vocal fold healing in a period of 30 days after topical mitomycin-C application. METHODS: Twelve swine underwent exeresis of mucosal flaps from the free edge of the anterior third of both vocal folds with a cold instrument (laryngeal scissors). The animals were divided into two groups: EG (Experimental Group), consisting of 6 animals undergoing topical MMC application (4 mg/dL) on the operated area for 4 minutes; CG (Control Group), 6 animals undergoing topical saline solution application on the operated area for 4 minutes. After 30 days, the animals were sacrificed and the larynges were collected and examined for the presence of synechiae as well as a histological immunohistochemical assessment of immature and mature collagen deposition, number of blood vessels and myofibroblasts. RESULTS: Mature collagen deposition in the EG was 452.12 μm² and 1332.31μm² in the CG; immature collagen deposition was 1511.73μm² in the EG and 1020.61μm² in the CG. The number of myofibroblasts was 1.556 in the EG and 3.583 in the CG. The number of blood vessels was 2.565 in EG and 6.917 in the CG. There were no synechiae in the two studied groups. CONCLUSIONS: There was an increase in immature collagen deposition in the experimental group when compared with the control group. There was a decrease in mature collagen deposition in the experimental group when compared with the control group. There was a decrease in the number of myofibroblasts in the experimental group when compared with the control group. A decrease in blood vessels was observed in the experimental group when compared with the control group. There was no synechia formation in either studied group.

Topical use of MMC in the upper aerodigestive tract: a review on the side effects

Not much is known about the side effects of mitomycin C (MMC), an anti-fibrogenetic agent, in the upper aerodigestive tract. However, its use in ophthalmology is widely known and without quantitatively important side effects. A literature review was performed for side effects of MMC in the upper aerodigestive tract. Forty-six articles, describing the use of MMC to prevent scarring, were retracted from PubMed. Thirty-two are human studies. MMC is used in different concentrations (0.1–10 mg/ml) with different application times (2–5 min) and frequencies (up to 4 times). Five hundred and thirty-eight patients were included in those publications, of whom 19 developed side effects (3.53%). No side effects developed in studies, where post-application irrigation with saline was reported. The longest mean follow-up period is 75.5 months. Direct relations between the reported side effects and MMC seem absent in most studies. Serious complications seem to occur when MMC is used in high concentrations. Unfortunately, sometimes crucial information is lacking. One patient was described who supposedly developed laryngeal carcinoma after repeated treatment of hyperkeratosis and anterior commissure webbing. Animal studies show that excessive fibrin production can lead to acute airway obstruction. In conclusion, topical application of MMC on a wound with consecutive irrigation with saline can be performed safely to prevent scar formation in circular structures of the upper aerodigestive tract. Long-term yearly control of the application site seems advisable.

Hydrogel blends of chitin/chitosan, fucoidan and alginate as healing-impaired wound dressings

In order to create a moist environment for rapid wound healing, a hydrogel sheet composed of a blended powder of alginate, chitin/chitosan and fucoidan (ACF-HS; 60:20:2:4 w/w) has been developed as a functional wound dressing. ACF-HS gradually absorbed DMEM without any maceration, and fluid absorption became constant within 18 h. On application, ACF-HS was expected to effectively interact with and protect the wound in rats, providing a good moist healing environment with exudates. In addition, the wound dressing has properties such as ease of application and removal and good adherence. Full-thickness skin defects were made on the backs of rats and mitomycin C solution (1 mg/ml in saline) was applied onto the wound for 10 min in order to prepare healing-impaired wounds. After thoroughly washing out the mitomycin C, ACF-HS was applied to the healing-impaired wounds. Although normal rat wound repair was not stimulated by the application of ACF-HS, healing-impaired wound repair was significantly stimulated. Histological examination demonstrated significantly advanced granulation tissue and capillary formation in the healing-impaired wounds treated with ACF-HS on day 7, as compared to those treated with calcium alginate fiber (Kaltostat; Convatec Ltd., Tokyo, Japan) and those left untreated.

Topical heparin: a promising agent for the prevention of tracheal stenosis in airway surgery

BACKGROUND

The protective effects of topical mitomycin-C (MMC) have been well documented for tracheal stenosis; however, to the best of our knowledge, the use of heparin as an anti-inflammatory agent to support wound healing in upper airway surgery was not studied before. The aim of this study was to investigate the efficacy of topical heparin for healing of tracheal re-implants in a rabbit's model and its resultant histological changes compared with that of MMC.

METHODS

In a rabbit model (n = 21), an elliptically shaped portion of the anterior tracheal wall was excised (3-4 tracheal cartilages) under anesthesia and immersed in an isotonic saline solution containing 0.4 mg/mL (0.04%) MMC (n = 7), heparin (liquemine) 5000 U/mL (n = 7), or none (n = 7) for 2 min and then re-implanted. The follow-up period was 2 wk for all animals and then both the larynx and the trachea were excised for histological evaluation. Hematoxylin-eosin (H and E) staining was applied to the excised tissues for microscopic evaluation.

RESULTS

Compared with controls, the granulation tissue formation score in MMC group (P = 0.03), and epithelial regeneration and inflammation scores in heparin group (P = 0.032 and P = 0.022, respectively) were more favorable. The fibrosis index and tracheal lumen ratio values were also more favorable in both MMC (P = 0.019 and P = 0.0028, respectively) and heparin (P = 0.023 and P = 0.0021, respectively) groups compared with controls on the 15th d.

CONCLUSIONS

Topical heparin application may have favorable effects on healing of tracheal autografts in a rabbit model. We suggest that heparin therapy should be further researched for the prevention of tracheal stenosis in airway surgery.

Histopathologic changes in guinea pig mastoid mucosa after topical mitomycin C application followed by mastoidectomy

PURPOSE

This study was performed to investigate the histopathologic changes observed in mastoid cavity of guinea pigs after the application of mitomycin C after mastoidectomy.

MATERIALS AND METHODS

The study was performed on 50 guinea pigs. Unilateral (right ear) mastoidectomy was performed on all guinea pigs. Twenty-five guinea pigs were separated as study group and the remaining were separated as control group. A mitomycin C-soaked sponge was placed in the mastoid cavities of the study group and a dry sponge was placed in those of the control group. Their mastoid cavities were examined histopathologically for absorbable sponge waste, abscess formation, fibrosis, vascularization, polymorphonuclear leukocyte infiltration, edema, lymphoplasmacytic inflammatory infiltration, and granulation tissue.

RESULTS

Absorbable sponge waste, abscess formation, fibrosis, vascularization, edema, and lymphoplasmacytic inflammatory infiltration were not significantly different between the groups. However, polymorphonuclear leukocyte infiltration and granulation tissue were statistically different between the groups.

CONCLUSION

Mitomycin C can be used after mastoidectomy to decrease the granulation tissue formation in ear discharges and to prevent the discharge.

Acute and chronic changes in the subglottis induced by graded carbon dioxide laser injury in the rabbit airway

OBJECTIVE

To investigate the repair process following carbon dioxide laser injury to the upper airway mucosa (UAM) during the development of chronic subglottic stenosis (SGS).

DESIGN

Animals were assigned to either sham control (cricothyroidotomy only) or injured (cricothyroidotomy and posterior subglottic laser) groups using various carbon dioxide laser exposures (8, 12, and 16 W) for 4 seconds.

SUBJECTS

Twenty-four New Zealand white rabbits.

INTERVENTIONS

The subglottis was approached via cricothyroidotomy. Sham control airways were immediately closed, whereas injured airways were subjected to graded carbon dioxide laser exposures prior to closure. Airways were endoscopically monitored preoperatively, postoperatively, and on postoperative days 7, 14, 28, 42, 56, 70, and 84. Animals were killed at 14 and 84 days. Subglottic tissue was harvested for histologic evaluation (reepithelialization, extracellular matrix, vascularity, and inflammation).

MAIN OUTCOME MEASURES

Endoscopic visualization and histologic analysis.

RESULTS

(1) Increases in UAM thickness (up to 5 times the thickness of normal mucosa) were observed but were limited primarily to the lamina propria. The mucosal epithelium regenerated without chronic changes. Focal areas of cartilage repair were encountered acutely after injury and to a greater extent in the chronic phases of repair. (2) Acutely, the thickened lamina propria comprised poorly organized extracellular matrix components and demonstrated increases in blood vessel size and number. (3) Histologic changes present in the acute phase only partially resolved in progression to chronic SGS. Chronic SGS was characterized by thick collagen fiber bundles extending into the remodeled subglottic cartilage.

CONCLUSIONS

The carbon dioxide laser induces acute changes to lamina propria architecture and vascularity that persist chronically. Elucidating responsible signaling pathways may facilitate the development of therapeutic agents to prevent or reduce the formation of SGS.

Mitomycin C and airway surgery: How well does it work?

Objective

Systematically review and critically evaluate all available published data on the use of topical mitomycin C (MMC) as an adjunctive in airway surgery.

Data Sources

Published studies indexed in MEDLINE, EMBASE, or Cochrane databases. Inclusion criteria were English language, sample size greater than five, and publication of data applicable to the analysis of topical MMC and airway surgery outcomes.

Review Methods

Evidence tables were compiled to include sample size, study design, and evidence level. Summary statistics, random-effects modeling, and subgroup analysis were performed.

Results

Twenty manuscripts (eight human, 12 animal) met the inclusion criteria. Seven of eight (87.5%) of the human studies and eight of 12 (66%) animal studies concluded topical MMC was beneficial to airway surgical outcomes. Eleven of twelve animal studies included randomization and a control group, compared with only two of eight human studies. Random-effects modeling of human studies (k=7) indicated that 81.4 percent (95% CI, 72.0%-90.9%; P < 0.001) of patients had improved outcomes attributable to MMC. Random-effects modeling of animal data included modeling of change in airway diameter (Hedge's G = −0.03; 95% CI, −0.66-0.60; P = 0.924) and the change in histologic measures (Hedge's G = 1.26; 95% CI, 0.596-1.92; P < 0.001) in MMC-treated animals vs controls.

Conclusion

The majority of the published literature individually suggests the use of topical MMC improves airway surgery outcomes. However, heterogeneity within the clinical studies, the lack of controlled data, and the lack of significance in the pooled animal data (other than histologic outcomes) suggest that the utility of MMC is still undetermined.

Anti-transforming growth factor beta as a treatment for laryngotracheal stenosis in a canine model

OBJECTIVES/HYPOTHESIS

Laryngotracheal stenosis (LTS) represents a significant treatment dilemma faced by otolaryngologists. Recent topical use of Mitomycin C as an adjunctive treatment has proved helpful but does not completely prevent stenosis. Current literature suggests that transforming growth factor beta (TGFB) plays a significant role in the development of subglottic stenosis. We modified an existing canine model to test antitransforming growth factor beta (anti-TGFB) as a possible treatment for laryngotracheal stenosis.

STUDY DESIGN

Pilot study in a modified canine model.

METHODS

Eight mixed-breed dogs underwent cautery injury to the subglottic region creating subsequent laryngotracheal stenosis. Four dogs were treated with saline injection into the injury site and four dogs were treated with a combination of intravenous (5 mg/kg on day 0 and 5 of the experiment) and local injection of anti-TGFB (50 micrograms).

RESULTS

In the canine model of induced subglottic airway injury, a combination of intralesional and intravenous anti-TGFB results in a reduction in tracheal stenosis (P < .05) and an increase in survival time (P < .03) when compared to the saline control subjects.

CONCLUSIONS

Anti-TGFB appears to be a useful adjunct in the treatment of LTS. Further study regarding the optimal dosing, route of administration, and timing of delivery is needed to understand the role of anti-TGFB in the treatment for laryngotracheal stenosis.

Wound healing modulators in a tracheoplasty canine model

Postsurgical tracheal stenosis results from fibrosis formation due to ischemia. There are healing modulators, hyaluronic acid (HA) and collagen polyvinylpyrrolidone (CPVP), which reduce collagen fibers formation. Thus we can hypothesize that the topical application of one of these modulators can diminish postsurgical tracheal scarring and stenosis. The aim of this work was to evaluate the macroscopic, microscopic, and biochemical changes of tracheal healing after the application of HA or CPVP in a canine tracheoplasty model. The study design was prospective experimental investigation in a canine model. Eighteen mongrel dogs underwent three cervical tracheal rings resection and end-to-end anastomosis. They were randomized into three groups according to treatment: group I (control group) (n = 6), topical application of saline solution on tracheal anastomosis; group II (n = 6), topical application of 15 microg HA on tracheal anastomosis; and group III (n = 6), topical application of 2.5 mg CPVP on tracheal anastomosis. They were evaluated clinical, radiological and tracheoscopically during 4 weeks. They were euthanized at the end of the study time. Macroscopic, microscopic, and biochemical changes of tracheal anastomosis healing were analyzed. Collagen formation was quantified by the Woessner method. All the animals survived the surgical procedure and study period. Macroscopic, radiologic, and endoscopic studies showed that animals in group I developed tracheal stenosis, inflammation, and firm fibrous tissue formation, and histological studies also showed severe inflammatory reaction and fibrosis formation. Groups II (HA) and III (CPVP) showed well-organized thin collagen fibers with minimal inflammatory response. Biochemical evaluation revealed a higher collagen concentration in group I animals (analysis of variance [ANOVA] p < .05 and Tukey p < .01). Thus, hyaluronic acid or collagen polyvinylpyrrolidone administered after tracheal anastomosis diminished the degree of stenosis and inflammatory reaction. Both modulators improved tracheal healing.

Topical mitomycin C effect on swine vocal folds healing

Several adjuvant therapies to surgery have been used to modulate the healing process of vocal folds, including topic mitomycin (MTC).

Aim

to evaluate the effect of topical MTC in the healing process of vocal folds 30 days after the exeresis of a mucosal fragment with CO₂ laser in a swine model (control group without mitomycin and study group with topical MTC), with collagen deposition measurement.

Study type

prospective experimental in swine.

Methods

two groups of 6 swine each were subjected to exeresis of a mucosal fragment of the vocal fold with CO₂ laser. Immediately after the procedure MTC was applied topically for three minutes on the study group. Thirty days later the animals were slaughtered and samples of the vocal folds were collected for histological analysis, with the purpose of quantifying collagen deposition by Picrosirius Red stain.

Results

the average area of total collagen in the vocal folds in the control group was 2.648,03 µm2, whereas in the study group it was 2.200,30 µm2 (p = 0.0043).

Conclusion

topical application of MTC after the exeresis of a mucous fragment of vocal fold with CO₂ laser in swine significantly decreased total collagen deposition.

Enhanced healing of mitomycin C-treated wounds in rats using inbred adipose tissue-derived stromal cells within an atelocollagen matrix

The aim of this study was to evaluate the potential accelerating effects of an adipose tissue-derived stromal cells (ATSC)-containing atelocollagen matrix with silicone membrane (ACMS) for repairing mitomycin C-treated healing-impaired wounds. Mitomycin C was applied to full-thickness skin incisions in this study to create a healing-impaired wound model in rat. After thoroughly washing out the mitomycin C from the wound, ACMS alone or ATSC-containing ACMS was applied to the wounds. Histological sections of the wounds were then prepared at indicated time periods after the treatments. These results indicated significantly advanced granulation tissue and capillary formations in the healing-impaired wounds treated with ATSC-containing ACMS compared with those treated with ACMS alone. Thus, this study suggested that transplantation of inbred ATSC-containing ACMS is effective for repairing healing-impaired wounds.

The role of mitomycin C in surgery of the frontonasal recess: a prospective open pilot study

BACKGROUND

Mitomycin C (MMC) inhibits fibroblast proliferation. The objective of this study was to determine the efficacy of MMC in reducing frontal ostium stenosis after endoscopic sinus surgery.

METHODS

A prospective open pilot study was conducted in 28 patients who had undergone one or more previous surgical interventions for frontal sinusitis. MMC solution was applied to the frontal ostial region via an endoscopic or combined endoscopic and external approach. Patency of the frontal ostium was evaluated endoscopically during regular follow-up. If restenosis was observed further, endoscopic application of MMC was undertaken.

RESULTS

There were 17 men and 11 women (mean age, 51.7 years; range, 26-86 years). Mean number of applications was 1.5 (range, 1:3). Mean follow-up was 19 months (range, 6-32 months). Patency rate was 86%.

CONCLUSION

Mitomycin appears to have an important role in reducing postoperative scarring, which may obviate the need for repeated and more extensive surgery.

The Efficacy of Mitomycin-C in the Treatment of Laryngotracheal Stenosis

OBJECTIVE

The purpose of this study is to evaluate whether the addition of topical mitomycin-C (MMC) application to the wound site after endoscopic treatment of laryngotracheal stenosis (LTS) resulted in measurable improvement in clinical outcomes.

STUDY DESIGN AND SETTING

A retrospective chart review of patients with LTS treated by the senior author over a 6-year period was performed. The treatment groups were stratified into two main categories: 1) endoscopic treatment alone and 2) endoscopic treatment + topical MMC. The "symptom-free" interval was determined (in months) for each subject using a two-tailed t test for statistical analysis of the control/study groups.

RESULTS

Sixty-seven procedures were performed in 36 patients with LTS with a mean of 1.86 surgical treatments per patient. The mean duration of the symptom-free interval after endoscopic treatment for LTS was 4.9 months in the endoscopic-only treatment group and 23.2 months in the endoscopic group receiving topical MMC. The symptom-free interval observed in the MMC group was significantly longer than the control subjects (P = 1 x 10).

CONCLUSIONS

The results of this study suggest that MMC is an effective adjuvant in the treatment of LTS. The results of this study provide strong supporting evidence that topical MMC is an effective adjuvant in the treatment of LTS.

Halofuginone prevents subglottic stenosis in a canine model

OBJECTIVES

Halofuginone is a low-molecular weight quinazolinone alkaloid coccidiostat that inhibits collagen type I synthesis, extracellular matrix deposition, and angiogenesis. This study was conducted to assess its potential in preventing subglottic stenosis (SGS).

METHODS

We induced SGS in 10 dogs randomly divided into 2 groups. Each group received treatment between 3 days before and 21 days after the induction of SGS. One group received oral halofuginone 40 microg/kg, and the other was given placebo. The area of the subglottic lumen was measured at baseline and 3 months later. In addition, human tracheal fibroblasts were cultured. The inhibitory effect of halofuginone was compared to the effect of mitomycin.

RESULTS

All dogs survived throughout the study with no side effects. Three months after the operation, no halofuginone-treated dog had SGS, in contrast to a 66% to 80% stenosis rate (mean, 72%) in controls (p < .008). Thick fibrotic tissue was found in the placebo-treated larynges, whereas an almost normal architecture was observed in halofuginone-treated larynges. Halofuginone inhibited the growth of human tracheal fibroblasts by 75%, in comparison with 60% inhibition by mitomycin (no statistically significant difference).

CONCLUSIONS

This preliminary study shows that halofuginone is effective in preventing SGS caused by an acute injury. Halofuginone has a potential therapeutic role in preventing SGS in humans.

Expandable tracheal stenting for benign disease: worth the complications?

OBJECTIVES

To characterize the limitations of self-expandable stents in the management of benign tracheal stenosis, we performed a retrospective review at a tertiary care medical center.

METHODS

Patients who underwent tracheal stenting were assessed for the cause and severity of tracheal stenosis, comorbidities, stent-related complications, and follow-up airway procedures.

RESULTS

Sixteen adults (12 women, 4 men; mean age, 47 years) had a total of 26 stents placed for benign disease. Intubation-related stenoses were most frequent (81%). The average follow-up time was 20 months (range, 1 to 40 months). Each stent remained functional for an average of 12.4 months. In the study group, 87% had a complication that required surgical intervention to maintain a patent airway. The most common problem was granulation tissue formation at the ends of the stent causing airway restenosis (81%), and 5 patients (31%) required tracheotomy as a result of restenosis around the stent. Fourteen of the stents (56%) were removed or expelled from the patients.

CONCLUSIONS

The implantation of self-expandable stents is a minimally invasive method of managing benign tracheal stenosis. Although a small subset of patients may benefit from placement, the majority of patients have complications that require intervention to maintain a patent airway. Thoughtful discretion is critical in selecting patients for this intervention.

Effects of Mitomycin-C on Normal Dermal Fibroblasts

OBJECTIVES

To evaluate the effects of mitomycin-C on the growth and autocrine growth factor production of human dermal fibroblasts from the face.

STUDY DESIGN

In vitro study using normal adult dermal fibroblast cell lines in a serum-free model.

METHODS

Cell cultures were exposed to 4 mg/mL, 0.4 mg/mL, 0.04 mg/mL, 0.004 mg/mL, and 0.0004 mg/mL concentrations of mitomycin-C solution. Cell counts were performed, and the cell-free supernatants were collected at 0, 1, 3, and 5 days after the initial exposure. Population doubling times were calculated and supernatants were quantitatively assayed for basic fibroblast growth factor (bFGF) and transforming growth factor (TGF)-beta1.

RESULTS

Continuous exposure to mitomycin-C caused fibroblast cell death by day 7 at all tested concentrations. A 4 minute exposure to mitomycin-C at 4 mg/mL caused rapid fibroblast cell death. A 4-minute exposure to mitomycin-C at either 0.4 mg/mL or 0.04 mg/mL resulted in decreased fibroblast proliferation. A 4 minute exposure to mitomycin-C at 0.4 mg/mL resulted in a marked increase in the production of both bFGF and TGF-beta1.

CONCLUSIONS

A clinically ideal concentration of mitomycin-C would slow fibroblast proliferation yet not cause cell death to allow for a wound healing response. Mitomycin-C 0.4 mg/mL for 4 minutes satisfies the above criteria in vitro.

Can Mitomycin C Really Prevent Airway Stenosis?

BACKGROUND/OBJECTIVES

Mitomycin C (MMC) is used in the prevention of upper airway stenosis. However, the efficacy of MMC is still debatable, and the potential complications of MMC use have been scarcely reported. We evaluated the efficacy and early complications of MMC in a wound model of the subglottis.

STUDY DESIGN

A randomized animal study.

METHODS

Sixty rabbits underwent a full-thickness injury to the posterior subglottis by diode laser. The animals were randomly assigned to three groups according to the different topical treatments of MMC 0.4 or 10 mg/mL or saline alone for 5 minutes. Animals were killed at 4 weeks, and gross and histologic findings were compared among different groups and 10 age-matched, non-wound, normal controls.

RESULTS

Thirty-two of the 60 (53%) animals died mainly of acute airway obstruction by necrotic debris, sloughs on, or cartilage collapse of the unhealed posterior subglottis during early weeks after wounding, higher in the MMC-treated animals (67%) than in the wound controls (25%) (P = .007). This resulted from the significant delay of wound healing in the MMC-treated groups compared with the wound controls (P = .012). The degree of subglottic stenosis was comparable among different groups (P > .8), although collagen deposition was significantly lower in the MMC-treated groups compared with the untreated controls (P = .036).

CONCLUSIONS

There was a significant risk of acute airway obstruction from delayed wound healing in rabbits that received subglottic laser wounding and MMC treatment. This risk should be considered in the use of MMC in clinical practice.

Airway complications from topical mitomycin C

OBJECTIVE

Topical application of mitomycin C appears to be a useful adjunct in reducing cicatricial scarring of the airways. Human and animal studies have demonstrated the efficacy and safety of mitomycin C topically in the treatment of airway stenosis at concentrations ranging from 0.4 mg/mL to 10 mg/mL. Although no reports of mitomycin C toxicity have been reported in the otolaryngology literature, the ophthalmologic literature has documented serious, vision-threatening complications resulting from the use of topical mitomycin C. The purpose of this study is to report complications related to mitomycin C use in the treatment of glottic and subglottic stenosis. Risk factors associated with these complications are identified.

STUDY DESIGN AND SETTING

A retrospective chart review of all patients treated by the senior author for laryngotracheal stenosis with endoscopic CO(2) laser incisions/dilation and adjuvant topical mitomycin C was performed to determine the incidence of complications. Variables studied included patient age and gender, location and severity of stenosis, medical comorbidities, length of procedure, postoperative instrumentation of the airway, and mitomycin C concentration.

RESULTS

Eighty-five cases of adjuvant topical mitomycin C use after CO(2) laser endoscopic treatment and dilation for upper airway stenosis were identified in a total of 44 patients. Complications that were believed to be caused by the local toxicity of mitomycin C occurred in 4 cases out of 85 (or 4.7%), manifested by accumulation of fibrinous debris at the operative site, resulting in partial airway obstruction and the need for emergent airway intervention.

CONCLUSIONS

Caution should be exercised when topical mitomycin C is used in the treatment of airway stenosis.

Prolongation of patency of airway bypass stents with use of drug-eluting stents

OBJECTIVE

Airway bypass by transbronchial fenestration has been shown to improve forced expiratory volume and flow in explanted emphysematous human lungs. We previously demonstrated the feasibility and safety of airway bypass stent placement in a canine model, but we found that most stents occluded within 1 week. The aim of this study was to evaluate the influence of controlled-release paclitaxel-eluting stents on prolongation of patency.

METHODS

With the subject dogs under general anesthesia, suitable segmental and subsegmental bronchial wall sites were selected by direct visualization with a flexible bronchoscope. A Doppler probe was used to detect and avoid sites with adjacent blood vessels. Transbronchial passages were formed with a 25-gauge transbronchial needle-tipped catheter and dilated with a 2.5-mm balloon integrated into the needle catheter. A specifically designed expandable stainless steel stent (3 mm long x 3 mm wide) embedded in a sleeve of silicone rubber was placed within the passage and expanded until secured about the bronchial wall. Fifty control stents (no paclitaxel impregnation) and 107 paclitaxel-eluting stents were placed in 25 dogs. Animals underwent bronchoscopy at intervals to assess stent patency.

RESULTS

Eight instances of minor and brief bleeding occurred during stent placement; all resolved without incident. There were no pneumothoraces or deaths associated with stent placement. No delayed complications occurred. No identifiable paclitaxel-related toxicity was observed. At 1, 4, 8, and 12 weeks, the patency rates were 10%, 0%, 0%, and 0% for control stents and 100%, 96%, 76%, and 65% for paclitaxel stents.

CONCLUSION

In an animal model, the use of specifically designed paclitaxel-eluting airway bypass stents was both feasible and safe. These stents resulted in a significant prolongation of patency.

Current treatment of vocal fold scarring

PURPOSE OF REVIEW

Vocal fold scarring still remains a therapeutic challenge, with the most problematic issue being the histologic changes that are primarily responsible for altering the viscoelasticity of the vocal fold mucosa. Optimal treatment for vocal fold scarring has not yet been established. To restore or regenerate damaged vocal folds, it is important to investigate the changes to the layer structure of the lamina propria. Tissue engineering and regenerative medicine may provide new strategies for the prevention and treatment of vocal fold scarring. Recent developments in this field are reviewed in the present article.

RECENT FINDINGS

Histologic studies have revealed that hyaluronic acid, fibronectin, decorin, and various other extracellular matrix components, as well as collagen, may contribute to determining the vibratory properties of the vocal fold mucosa. Changes of these molecules are thought to affect the viscoelasticity of the scarred vocal folds. Based on such histologic findings, innovative approaches have been developed, including administration of hyaluronic acid into injured or scarred vocal folds. Other strategies that have recently shown advances include growth factor therapy and cell therapy using stem cells or mature fibroblasts. The effects of these new treatments have not fully been confirmed clinically, but there seems to be great therapeutic potential in such regenerative medical strategies.

SUMMARY

Recent research has revealed the detailed histologic and rheologic changes related to vocal fold scarring. Based on these findings, various new therapeutic strategies have been developed in animal models using tissue engineering and regenerative medicine. However, no clinical trials have been performed, and more studies are necessary to establish the optimum modality.

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.

Single perivascular delivery of mitomycin C stimulates p21 expression and inhibits neointima formation in rat arteries

OBJECTIVE

Mitomycin C (MMc) is an antibiotic that exerts a potent antiproliferative effect in tumor cells. Because the proliferation of vascular smooth muscle cells (VSMCs) plays a prominent role in the development of restenosis after percutaneous coronary interventions, the present study examined the effect of MMc on VSMC proliferation and on neointima formation after arterial balloon injury.

METHODS AND RESULTS

Treatment of cultured rat aortic VSMCs with MMc (1 nmol to 30 micromol/L) inhibited VSMC proliferation in a concentration-dependent manner. Whereas high concentrations of MMc (1 to 30 micromol/L) induced VSMC apoptosis, as reflected by DNA laddering and caspase-3 activation, lower concentrations of MMc (1 to 300 nmol/L) directly inhibited VSMC growth by arresting cells in the G2/M phase of the cell cycle. The antiproliferative action of MMc was associated with a selective increase in the expression of the cyclin-dependent kinase inhibitor p21, and with a decrease in cyclin B1-cyclin-dependent kinase-1 complex activity. Finally, the local perivascular delivery of MMc immediately after balloon injury of rat carotid arteries induced p21 expression and markedly attenuated neointima formation.

CONCLUSIONS

These studies demonstrate that MMc exerts a potent inhibitory effect on VSMC proliferation and neointima formation after arterial injury. MMc represents a potentially new therapeutic agent in treating and preventing vasculoproliferative disease.

Feasibility and safety of airway bypass stent placement and influence of topical mitomycin C on stent patency

OBJECTIVE

Airway bypass via transbronchial fenestration has been shown to improve forced expiratory volume and flow in explanted human emphysematous lungs. The aim of this study was to evaluate the feasibility and safety of in vivo airway bypass stent placement by using a canine model and to assess the influence of topical mitomycin C on the prolongation of stent patency.

METHODS

With dogs under general anesthesia, suitable segmental and subsegmental bronchial wall sites were selected by direct visualization with a flexible bronchoscope. Peribronchial blood vessel injury was avoided by using a Doppler probe. Transbronchial fenestration was formed with a 22-gauge transbronchial needle, and the passage was then dilated with a 2.5-mm angioplasty balloon. A balloon expandable stainless-steel stent (3 mm long x 3 mm wide) with a sleeve of silicone rubber covering was placed within the fenestration. Animals were bronchoscoped weekly to assess stent patency. Seventy stents were placed in 12 dogs. Thirty-five served as controls, and the other 35 received transbronchoscopic topical application of mitomycin C once weekly to evaluate the effect on the maintenance of stent patency. Mitomycin C stents were divided into 4 groups according to the number of treatments: group A, 1 treatment only; group B, 4 weeks; group C, 7 weeks; and group D, 9 weeks. Each once-weekly mitomycin C application consisted of 0.2 mL at a concentration of 1 mg/mL, delivered through a small polyethylene catheter.

RESULTS

Four instances of minor and brief bleeding occurred during stent placement and resolved without incident. One pneumothorax occurred and was treated by chest tube placement, without any adverse sequelae. There was no mortality associated with stent placement. No delayed hemorrhage or pneumothorax occurred. All control stents were occluded at the 1-week follow-up. The median durations of stent patency for group A (n = 8), group B (n = 9), group C (n = 10), and group D (n = 8) were 3, 8, 13, and greater than 20 weeks, respectively.

CONCLUSIONS

Airway bypass stent placement can be performed safely. In an animal model, most stents became occluded within 1 week, but topical mitomycin application resulted in significant prolongation of patency.

Increased expression of epidermal growth factor receptors in the tracheal epithelia after topical mitomycin-C in rabbits

The aim is to examine histopathological changes and expression of epidermal growth factor receptor (EGFR) in tracheal epithelia caused by application of topical mitomycin-C (MMC) in rabbit model after the tracheotomy procedure. The conventional tracheotomy was performed in 16 rabbits. They were randomly divided into two equal groups. The first group was applied MMC at a concentration of 0.4 mg/ml around tracheotomy for 5 min, and the other group was not taken a treatment as a control. The animals were sacrificed at the end of 4 weeks. Their tracheas were evaluated with H&E and Masson's trichrome histochemically, and with antiepidermal growth factor receptor immunohistochemically. Results showed that there was no significant difference between MMC and control group for inflammatory cells (P=0.09). The numbers of fibroblasts and subepithelial tissue thickness in the group exposed to MMC were significantly lower than the control group (P<0.05). In contrast, the percentage of EGFR in the application of MMC group was significantly higher than the control group (P<0.05). The application of topical MMC on airway epithelia after tracheotomy showed significant elevation in the levels of epithelial EGFR expression compared to controls in a rabbit model. The activation of epithelial EGFR may facilitate epithelial healing, but further studies are needed to assess the effect of topical MMC on respiratory epithelia.

Time and Dose Effects of Mitomycin C on Extracellular Matrix Fibroblasts and Proteins

OBJECTIVES/HYPOTHESIS

The objective was to determine treatment dose and time-dependent effects of injected mitomycin C on extracellular matrix fibroblasts, collagen, and fibronectin, important mediators in the wound healing response, in a rat cutaneous wound model.

STUDY DESIGN

A prospective, controlled animal study.

METHODS

Forty rats were injected with three different doses (0.4, 2.3, and 5.0 mg/mL) of mitomycin C at three different wound sites with a fourth wound site receiving saline as a control. The rats were grouped to have their tissue harvested at five different dates ranging from 1 week to 8 weeks. After death, samples from the wound site underwent Western blot analysis for collagen and fibronectin and histological analysis measuring fibroblast apoptosis.

RESULTS

Over an 8-week period, collagen and fibronectin significantly decreased and fibroblast apoptosis significantly increased. No correlation was found between the injected dose of mitomycin C and either the extracellular matrix protein concentration or the rate of fibroblast apoptosis.

CONCLUSION

Mitomycin C demonstrated a long-term effect in a wound, inhibiting collagen and fibronectin production and inducing apoptosis. Use of mitomycin C in excess of 0.4 mg/mL did not alter protein concentrations or rate of apoptosis.

The effects of mitomycin C and 5-fluorouracil/triamcinolone on fibrosis/scar tissue formation secondary to subglottic trauma (experimental study)

PURPOSE

The aim of the study was to compare the effects of mitomycin-C (MMC) and 5-fluorouracil/triamcinolone acetonide (5-FU/TA) on the development of fibrosis/scar tissue formation of rabbit subglottic area, which is injured acutely.

MATERIALS AND METHODS

After standardized trauma to subglottic area the rabbits were divided into those that received treatment and those that did not (controls). The subjects were treated with either topical 0.4 mg/mL MMC or 5 mg 5-FU/TA injection. Those groups were further divided into subgroups depending on the time of examination: at 2 or 6 weeks. Each subgroup had 4 rabbits. The specimens were examined histopathologically and the measurements were performed using a software.

RESULTS

The fibrosis indices (FIs) of the treated subgroups were significantly less than the FIs of their corresponding control subgroups (P<.05). The difference in FIs of the MMC-treated and 5-FU/TA-treated groups was not statistically significant (P>.05). MMC and 5-FU/TA did not interfere with regeneration of the epithelium although in 2 cases treated with 5-FU/TA the regenerated epithelium showed squamous metaplasia.

CONCLUSIONS

Both MMC and 5-FU/TA decrease fibrosis/scar tissue formation secondary to experimentally induced acute subglottic trauma. There is no significant difference between the effects of the 2 drugs.

Use of mitomycin C in the pediatric airway

PURPOSE OF REVIEW

Mitomycin C was not used in the field of otolaryngology before 1998. Currently it is commonly used by all pediatric otolaryngologists dealing with airway stenoses. Mitomycin C offers the surgeon a method of modifying healing and diminishing granulation tissue and cicatricial scar.

RECENT FINDINGS

There are numerous animal studies showing the beneficial effect of mitomycin C on wound healing in the airway. The human studies rarely have controls and in many cases are case reports. Human studies typically use dosages commonly used in ophthalmology, which are in the low range in relation to the animal airway studies.

SUMMARY

This article attempts to summarize the available research on mitomycin C, helping the clinical otolaryngologist choose the proper dosage, indications, and frequency of use.

Mitomycine C : prévention et traitement des synéchies glottiques antérieures

OBJECTIVES

Topical applications of mitomycin C to the anterior glottis may prevent anterior glottic synechia (prevention group) or restenosis (treatment group).

METHODS

In the prevention group, six patients with glottic carcinoma involving the anterior commissure were treated by transoral laser surgery. Repeated procedures were performed in one patient. For the six patients in the treatment group, the anterior glottic synechia was secondary to frontolateral laryngectomy (three patients), transoral laser therapy for laryngeal papillomatosis (two patients) or bilateral glottic carcinoma (one patient). Mitomycin C (0.4 mg/ml) was used as a topical application on the anterior commissure for a duration of 4 minutes. Outcome was assessed clinically at three months using a visual scale: no synechia (success), micro-synechia (partial failure), and synechia (failure).

RESULTS

In the prevention group, there were six successes and one partial failure. In the treatment group, there were two successes, three partial failures, and one failure. No side effects were noted.

CONCLUSION

Topical application of mitomycin C was effective to prevent anterior glottic synechia after transoral laser surgery for glottic carcinoma involving the anterior commissure. It is an alternative to endolaryngeal keel in patients with sequellar synechia. These preliminary results should be further evaluated in a larger series.

Transforming growth factor-beta1, myofibroblasts, and tissue remodeling in the pathogenesis of tracheal injury: potential role of gastroesophageal reflux

Subglottic stenosis (SGS) is characterized by the obliteration of the tracheal lumen due to excessive deposition of connective tissue. We hypothesize that tracheal injury triggers the early production of transforming growth factor-beta1 (TGF-beta1), a factor implicated in fibroproliferative disorders. In turn, TGF-beta1 stimulates the transformation of tracheal fibroblasts into myofibroblasts with increased matrix production and scar contraction that might be influential in laying the foundation for the development of SGS. Consistent with this hypothesis, histologic analysis of tracheas from humans with SGS and from rats with experimental tracheal injury revealed increased alpha-smooth muscle actin-positive cells as compared to control tracheas, suggesting increased myofibroblast differentiation. Rat tracheal fibroblasts exposed to TGF-beta1 or gastric juice in vitro showed increased expression of alpha-smooth muscle actin, alterations in the expression of matrix molecules, and increased contraction of collagen gels. These findings suggest that gastric juice or other agents of tracheal injury promote tissue remodeling through the stimulation of the differentiation of fibroblasts into myofibroblasts.