Loss of stiffness in collagen-rich uterine fibroids after digestion with purified collagenase Clostridium histolyticum

Abstract

Background: Uterine fibroids are a significant health problem. These common benign tumors occur in 70-80% of women before age 50 years and often cause bleeding and pain and can interfere considerably with daily life. Current treatment options are limited. Fibroids contain substantial amounts of altered and disordered collagens, which contribute to their bulk. Targeting these collagens directly presents a novel treatment approach.

Objectives: We sought to test the hypothesis that a highly purified collagenase Clostridium histolyticum will digest interstitial collagen in uterine fibroids and reduce their stiffness and thereby evaluate the feasibility that this collagenase C histolyticum can be developed into an alternative treatment for fibroids. A secondary objective was to describe the collagen content of the fibroid tissue.

Study design: Fibroid tissue cubes (1 cm³; n = 154) were cut from 17 uterine fibroids that were obtained from 7 consented subjects undergoing scheduled hysterectomies. Tissue cubes were injected with diluent, placebo, or highly purified collagenase C histolyticum (0.05, 0.1, or 0.2 mg/cube) and incubated at 37°C for 24, 48, 72, or 96 hours. At each time point, 6 noninjected control cubes were also evaluated. Tissue cubes were photographed before and after incubation. Myometrial samples (n = 21) were also evaluated. Stiffness was quantified through rheometry by measuring complex shear moduli of the tissues. Percent fibrosis was determined by computerized analysis of Masson-trichrome-stained slides. Digestion of collagen fibrils was confirmed by transmission electron microscopy.

Results: Fibrosis in untreated fibroids ranged from 37% to 77%, reflecting the collagen-rich nature of these tumors. After treatment with collagenase for 96 hours, fibrosis ranged from 5.3% to 2.4%. Transmission electron microscopy confirmed complete digestion of collagen fibrils. Tissue stiffness was reduced with all 3 doses of collagenase treatment and at all 4 time points. Longer incubation times with collagenase caused greater reduction in stiffness, and treated cubes lost their cuboidal shape and had gelatinous/liquefied centers. At 96 hours the stiffness in tissues treated with the lowest dose was reduced to 966 ± 106 Pascal compared with the diluent-treated control at the same time (5323 ± 903 Pascal; P < .0001; by analysis of variance with Tukey-Kramer).

Conclusion: Uterine fibroids have a high content of collagen that can be effectively digested by highly purified collagenase C histolyticum, resulting in reduced tissue stiffness. Loss of stiffness may decrease bulk symptoms in vivo and possibly lead to shrinkage of fibroids through changed mechanotransduction, leading ultimately to reduced fibroid symptoms of pain and bleeding. Clinical trials are necessary to evaluate the safety and efficacy of collagenase C histolyticum including the rate of regrowth of fibroids. The data of this study provide a strong rationale for using this purified collagenase in clinical trials as a local treatment for women with fibroids.

Keywords: collagen; collagenase; fibroid; fibroid therapy; leiomyoma; mechanotransduction; tissue stiffness; uterine fibroids.