Elsevier

The Spine Journal

Volume 10, Issue 5, May 2010, Pages 441-447
The Spine Journal

Basic Science
Mitomycin C-polyethylene glycol controlled-release film inhibits collagen secretion and induces apoptosis of fibroblasts in the early wound of a postlaminectomy rat model

https://doi.org/10.1016/j.spinee.2010.02.017Get rights and content

Abstract

Background context

Recovery from spine surgery is usually accompanied with the development of epidural scar adhesions from the abnormal proliferation of fibroblast and extracellular matrix–related metabolism. Polyethylene glycol (PEG) could alleviate the postsurgical adhesion formation with still leaving a gap between the sheet and the dura. However, PEG film could not function as a three-dimensional barrier to prevent adhesion completely. Mitomycin C (MMC) could also reduce the scar formation after surgery, but cytotoxicity and the administrative pathway prevent its application.

Purpose

Our purpose was to design and attest the role of new delivery system MMC-PEG controlled-release film in preventing the epidural scar adhesions after laminectomy in the rat model.

Study design/setting

A total laminectomy of L1 in the rat model was used to assess epidural fibrosis between and around the spinal nerves using a histochemistry assessment along with flow cytometry analysis.

Patient sample

The sample comprises 64 adult male Sprague-Dawley rats.

Outcome measures

The outcome measures are macroscopic evaluation, histological analysis, and flow cytometry analysis.

Methods

Lumbar laminectomies at L1 and L2 with a L1–L2 disc injury were performed on 64 adult male Sprague-Dawley rats. The rats were then randomized into four groups. In Group I, 25 mg PEG film was applied on the dura mater in the laminectomy area before the layers were sutured. In Group II, a cotton pad soaked with 0.05% MMC solution was kept on the laminectomy area for 5 minutes. In Group III, 25 mg PEG film containing 0.01% MMC was implanted on the laminectomy area. In Group IV, the laminectomy area was flushed with saline before wound closure. The rats were sacrificed 4 weeks after the operation. Macroscopic evaluation and histological analysis of epidural scar adhesion with the hematoxylin and eosin stain and Masson stain were used followed by the quantification of hydroxyproline (Hyp) and flow cytometry analysis of the apoptosis of fibroblasts in the scar tissues.

Results

The recovery of all rats was uneventful after the operations. In the laminectomy sites of rats treated with MMC or MMC-PEG, the dura mater was clean without any evident adhesion or membrane. Collagen tissue hyperplasia significantly decreased in the MMC- or MMC-PEG–treated models. Accordingly, Hyp concentration was significantly reduced in these two groups compared with saline-control group. In addition, the apoptosis of fibroblasts, however, was significantly elevated in the MMC or MMC-PEG group compared with the saline-control group.

Conclusions

These results demonstrate that the treatment of postlaminectomy wounds with MMC-PEG film reduces the severity of adhesion by decreasing the concentration of Hyp and increasing the apoptosis of fibroblasts.

Introduction

Epidural fibrosis is an expected healing consequence after laminectomy. This extradural fibrotic tissue may extend into the vertebral canal and adhere to the dura mater and nerve roots, causing recurrent symptoms including pain [1], [2], [3], [4], possibly leading to the failure of spinal surgery [5]. Furthermore, epidural adhesions make reexposure of the same operative area technically difficult and dangerous because the risk of nerve root injury and dural tears are greatly increased [6], [7].

The control of scar formation has been one of the main concerns in spine surgery and the subject of research for many years. A large number of materials and methods for preventing epidural fibrosis have been studied including free or pedicle fat grafts [8], [9], absorbable gelatin films and sponges, cellulose mesh [9], [10], hyaluronic acid [11], and local or systemic pharmaceuticals such as methylprednisolone and dexamethasone [12], [13], [14], [15], [16] in an attempt to physically or chemically inhibit scar ingrowths.

Polyethylene glycol (PEG) is a water-soluble polymer, has no electric charge and no affinity for any specific organ, and is nonimmunogenic and nontoxic [17], [18], [19]. Although PEG significantly reduced postlaminectomy proliferative scar without affecting the integrity of incisional wound healing, the process of readsorption would result in a fibrotic mass and leave a gap between the sheet and the dura [20]. Meanwhile, PEG could not prevent nerve root adhesion.

Mitomycin C (MMC), a widely used chemotherapeutic drug, has been proposed as a potential adjuvant for the control of scar tissue in surgical wounds [21], [22], [23] because of its capacity to inhibit proliferation and induce the apoptosis of fibroblasts [24], [25]. The toxic characteristics of MMC were most likely responsible for the greater tissue damage that occurred when it was used in the injected form or at high concentration in long-term use, causing increased scar tissue formation and even the failure of the wound healing [26]. The strategy to reduce the dose of MMC in topical application would be encouraging.

In the current study, we used a new controlled-release delivery system in which a small dose of MMC was adsorbed on the PEG film. The purpose of our research was to investigate the efficacy of MMC-PEG film as a biophysical and chemical barrier to suppress postlaminectomy scar invasion. We hypothesize that with the decomposition of PEG film, MMC would be continuously released and induce the apoptosis of fibroblasts. If true, it will offer a novel strategy to apply MMC in the prevention of postlaminectomy adhesions in spine surgery.

Section snippets

Animals

A total of 64 mature male Sprague-Dawley rats, weighing 300±20 g, were used in this study (protocol approved by the Animal Care and Research Committee of the Nanjing Medical University, China).

Preparation of MMC-PEG film

First, three different liquids were prepared. Liquid A: 20 g polyvinyl alcohol-124 was resolved in 85% ethanol, dried at 50°C, and redissolved completely in 200 mL water and was sterilized. Liquid B: the mixture of 2.0 g sorbic acid and 2.0 g glycerin was resolved in 50 mL water and sterilized. Second, 50

Macroscopic evaluation of epidural scar adhesion

The recovery of all rats was uneventful after the operations. There was no case of wound infection or neurological deficit in any rat. In the laminectomy sites of rats treated with PEG, the dura mater was covered by a thin adhesion, which could be easily removed and expose clean dura mater with little bleeding. But in the laminectomy sites of rats treated with saline, severe, thick, and tenacious epidural scar adhesions were found between the dura mater and surrounding tissue. The dissection of

Discussion

Epidural fibrosis remains a great challenge in the recovery after spine surgery. Fibroblasts, originating from the overlying muscles and following extension of postoperative hematoma into the vertebral canal, release excessive extracellular matrix and cause the abundance and strong adhesion of the tissue [27]. Thus, the migration of fibroblasts from the raw surface of the erector spine musculature was stated as the source of postoperative scar tissue [28].

Various reagents and materials have

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  • Cited by (0)

    FDA device/drug status: not applicable.

    Author disclosures: JL (stock ownership, including options, warrants, paper; grants, Key Technique Project, Shanghai; other relationships, paper); BN (stock ownership, including options, warrants, paper; grants, Key Technique Project, Shanghai; other relationships, paper); LZ (other relationships, paper); JY (other relationships, paper); XC (stock ownership, including options, warrants, paper; other relationships, paper); WZ (stock ownership, including options, warrants, paper; other relationships, paper).

    This project was funded by the Key Technique Project of Shanghai (08JC1406900), the Key Project of Nanjing Medical University (08NMUZ023), and the Natural Science Foundation of Jiangsu Provincial Education Department (06KJD320075).

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