Effect of mitomycin C on keloid fibroblasts: an in vitro study

Use of mitomycin C for treatment of keloid: a preliminary report

OBJECTIVES

Mitomycin C (MC) is an anti-neoplastic agent with an anti-proliferative effect on fibroblasts. We set out to evaluate the effect of MC application following keloid excision.

STUDY DESIGN AND SETTING

Patients with keloid in a tertiary referral center were enrolled in a prospective study. The scar was excised and prior to skin closure, a pledget with 1 cc of MC 0.4 mg/mL was applied for 5 minutes. Patient satisfaction and keloid thickness were assessed.

RESULTS

All patients were satisfied with the results, although complete disappearance of the keloid was evident only in two. Keloid thickness was measured and ranged from 5 to 26 mm. Following surgery and treatment at 2 months thickness ranged from 0 to 8 mm.

CONCLUSIONS

MC application following scar resection appears to be effective in treatment of keloid.

SIGNIFICANCE

As no specific effective treatment for keloid is currently available, utilization of this readily available therapeutic agent may improve treatment outcome.

Otologic Effects of Topical Mitomycin C: Phase I-Evaluation of Ototoxicity

HYPOTHESIS

To determine ototoxicity of topical mitomycin C when placed in the middle ear at varying concentrations.

BACKGROUND

Despite meticulous surgical technique and diligent postoperative care, some patients develop excessive scar and granulation tissue in the middle ear or mastoid cavity. Poor wound healing may result in infection, tympanic membrane perforation, or conductive hearing loss, which may necessitate further surgery. Use of topical mitomycin C in the ear may be beneficial in reducing scar and granulation tissue formation. This phase of the study was developed to determine the safety of topical mitomycin C in the rat model relative to ototoxicity.

METHODS

Twelve Sprague-Dawley rats were evaluated with auditory brainstem response testing before and after treatments. Topical mitomycin C was injected in the middle ear of the right ear of eight animals. Varying concentrations of 0.125 to 0.5 mg/ml were used. Saline was injected in the left ear of each animal to serve as a control. Four separate animals were evaluated with placement of topical mitomycin C on Gelfoam into the middle ear. In two animals, Gelfoam was placed in the middle ear for 1 minute and then removed. In two animals, Gelfoam was placed in the middle ear and left in place. Auditory brainstem response testing was performed at 4 weeks and at 8 weeks.

RESULTS

Using a high concentration of mitomycin C (>0.25 mg/ml) resulted in ototoxicity, with an increase in the auditory brainstem response threshold at 4 weeks and at 8 weeks. At low concentrations (<0.20 mg/ml), no change in auditory brainstem response threshold was noted. Animals treated with Gelfoam soaked in mitomycin C showed no change in auditory brainstem response threshold.

CONCLUSION

The results of this study indicate that topical mitomycin C on Gelfoam applied in the middle ear appears safe when low concentrations are used, even in the rat, which has a higher susceptibility to gentamycin toxicity than humans. Higher concentrations may lead to ototoxicity based on changes in Wave V on auditory brainstem response. This treatment may prove to be an important option for patients suffering from chronic granulation tissue or scar tissue in the external or middle ear.

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.

Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.

A Comparative Evaluation of the Efficacy of Intraoperative Mitomycin C Use After the Excision of Cobblestone-Like Papillae in Severe Atopic and Vernal Keratoconjunctivitis

OBJECTIVE

To evaluate the effect of intraoperative 0.02% mitomycin-C (MMC) use after excision of cobblestone-like papillae on preventing corneal recurrences compared with simple papillary resection.

METHODS

Thirteen cases of atopic keratoconjunctivitis (AKC) and 6 cases of vernal keratoconjunctivitis (VKC) with a mean age of 12.0 +/- 3.4 years participated in this study. All patients had cobblestone-like papillae on the upper tarsal conjunctiva and corneal ulcers or erosions that were refractory to conventional treatment. Seventeen eyes received simple papillary excision. Papillary excision with intraoperative application of MMC was performed in 7 eyes: 0.02% MMC was applied for 2 minutes to the upper palpebral conjunctiva immediately after papillary excision. Recurrence of corneal lesions and regrowth of papillae were evaluated and compared retrospectively between the 2 groups. Postoperative follow-up ranged from 12 to 18 months.

RESULTS

Papillary regrowth was observed in 14 out of 17 eyes (82.4%) in the simple resection group, whereas regrowth was noted in 4 out of 7 eyes (57.1%) in the MMC group (P > 0.05). The recurrence of corneal lesions was observed in 8 out of 17 eyes (47.1%) in the simple resection group (mean onset 1.5 +/- 1.7 months) compared with 1 eye with corneal recurrence 6 months after surgery in the MMC group (14.3%). The difference was statistically significant (P < 0.05). No complications related to MMC use were observed during the follow-up period.

CONCLUSION

MMC-aided papillary resection may be rewarding in well-selected severe AKC and VKC cases in preventing recurrence of corneal complications, but the potential complications of MMC use would suggest caution in its consideration.