Neurosurg. Rev. 13 (1990) 299 303

Neural tissue compatibi l i ty o f Teflon as an implant material for microvascular decompress ion

Ahmed Ammar 1, Carl Lagenaur 2, and Peter Jannetta 3

aDepartment of Neurosurgery, College of Medicine and Medical Sciences, King Faisal University, Dammam, Saudi Arabia, 2Department of Neurobiology, Anat- omy, and Cell Science, and 3Department of Neurological Surgery, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, U.S.A.

Abstract

Teflon is utilized in neurosurgery as well as in plastic, vascular and heart surgery. Although the effect of Teflon on different types of cells and tissues has been previously studied, we are not aware of any study in which the effect of Teflon was tested on cells of the central nervous system. We have therefore examined the tissue compat- ibility of spongy and fibrous Teflon by directly exposing the Teflon to dissociated cerebellar cells containing both glia and neurons in tissue culture. Daily examination of the growth of the cells adjacent to Teflon fibers using an inverted phase contrast microscope revealed that Teflon has little or no effect on the growth of these cells. When the cells are fixed after 7 days in culture and stained by the Jenner-Giemsa method, adhesion of both gila and neurons to the surface of the Teflon was seen. Attachment of neural cells to the Teflon was not exten- sive, as was shown by indirect immunofluorescence tech- nique in connection with double-label staining with anti- GFAP as glia marker and anti-M6 as mouse neuron marker. Thus, these experiments show that Teflon is relatively inert when used as an implant in the central nervous system.

Keywords: Cell adhesion, cell culture, microvascular de- compression, mouse cerebellum, Teflon, tissue compat- ibility.

1 Introduction

Material that is used as a permanent implant in the central nervous system should fulfill the fol- lowing criteria: 1) have good mechanical proper- ties; 2) be physically stable inside the body (not subject to ionization or absorption); 3) be non- toxic, nonstimulating, and noncarcinogenic; 4) and be compatible with its surrounding tissue [1, 2, 31.

�9 1990 by Walter de Gruyter & Co. Berlin �9 New York

Teflon has been used in plastic vascular surgery since the 1960's. Some experiments have recently demonstrated a carcinogenic effect of Teflon if implanted subcunaneously in rats [5, 26], while other studies have suggested that Teflon has a toxic effect when used as implant material, espe- cially when used as a substitute for small arteries [6, 22, 28 -30 ] . Other in vitro experiments have suggested that Teflon has little effect on the mouse embryo cell division rate, which has been used a measure of general toxic effect [/4]. In contrast to these results, the surgical use of Teflon in man during the past 20 or more years has provided little evidence of general tissue incompatibility [15, 19]. Several in vivo and in vitro studies demon- strated the good tissue compatibility of Teflon [7, 8, / 0 - 1 3 , 23, 24, 25, 28].

The mechanical properties of shredded Teflon fa- vor it over several other materials as implants in microvasular decompression (MVD) operations for treatment of trigeminal neuralgia, hemifacial spasm, disabling positional vertigo, glossophar- yngeal neuralgia, and spasmodic torticollis [ 1 5 - 19]. To the best of our knowledge the reaction of Teflon, placed in such operations against cells of the central nervous system, has not been tested.

The purpose of the present study was to evaluate the tissue compatibility and adhesion properties of Teflon when placed against cells of central nerv- ous system origin. Tissue culture techniques have long been utilized for testing the tissue compati- bility of different implant materials and different types of cells of man, mouse [6, 7, 9 - 1 1 , 25, 30], or chick embryo [2, 3] have been used. We chose the cerebellar cells of mice for our experiments

300 Ammar et al., Tissue compatibility of Teflon

because the cerebellum has earlier successfully been used as a source of glia cells (astrocyte and oligodendrocyte) and neurons [20, 21]. Tissue cul- ture methods provided the model to study tissue compatibility of materials as well as to study cell- to-cell interaction.

2 Materials and methods

The cerebellar cells containing neurons, glia, mi- croglia, as well as endothelial and meningeal cells, were obtained from 4 - 5 days old bred CD-1 mice (CHARLES RIVERS). The cerebellum was dissected under microscope, cut into about 0.5 mm pieces, and trypsinized with 1 percent trypsin for 13 min- utes, then dissociated with trituration in 0.25 per- cent DNAse in Hanks buffered saline (Gmco). The culture was carried out as described by SC~MITZER and SCHACHNER [27]. About 2.5 mm 2 pieces of shredded Teflon were sterilized and fixed by paraffin wax [2, 3] in the bot tom of 2 x 106/60 mm 2 tissue culture dishes under aseptic conditions. A few fibers were also taken from a Teflon sheet and were fixed to the bot tom of the dishes with paraffin wax. The experiment was repeated 3 times. In every experiment, 5 tissue culture dishes were used. In a second experiment, Teflon pieces and fibers were left floating in the medium. In a third experiment, the Teflon fibers were fixed on the surface of cover slips, which were placed in tissue culture dishes. In the first experiment, ] 0 6

cells were cultured in 3 ml of BME Earle's con- taining + 10 percent horse serum in the dishes containing the Teflon. Polylysine-coated cover slips were used as controls to monitor cell growth.

In the second and third experiments, 2 x ] 0 6 cells were cultured in the dishes in which the shredded Teflon was fixed. The cells were examined daily under an inverted phase contrast microscope. After seven days, the cells of the first experiment were fixed and stained by the Jenner-Giemsa method in order to document the growth of the cells on the surface of the Teflon. The cells from the third experiment were stained by anti-GFAP, which is a marker for astrocytes [4, 9, 21]. Anti- G F A P was obtained from DAKO on the fourth day of the experiment. The same cells were also stained by monoclonal antibody anti-MG, which is used as a marker for mouse neurons [20, 24]. A Zeiss standard fluorescence microscope was used to examine the adherent stained cells on the Teflon fibers.

Figure 1. A: The normal growth of mixed cerebellar cells around the Teflon fibers, as shown under an inverted phase contrast microscope. Bar = 25 gin. B: The ad- hesion of the cells on the surface of Teflon fibers. The cells were stained by the Jenner-Giemsa method. Mag- nification 6.3 x 12.5. C: The adhesion of the cells to the surface of a piece of Teflon sponge. The cells were stained by the Jenner-Giemsa method. Magnification 6.3 x 12.5.

3 Results

Cells were consistently found to grow normally in close proximity to the Teflon, and only a few degenerating cells were observed near the Teflon. Extensive neurite outgrowth and cell attachments were observed on the polylysine-coated cover slips adjacent to Teflon fibers (Figure 1, A). As early as the second or third day, a few cells were clearly adherent to the surface of the Teflon fibers. The growth of the cells was not obviously inhibited or stimulated by directly exposing the cells to the Teflon. Jenner-Giemsa stained specimens showed some cells attached to the fibers of the Teflon as

Neurosurg. Rev. 13 (1990)

Ammar et al., Tissue compatibility of Teflon 301

Figure 1

well as to the surface of the Teflon sheets (Figure 1, B, C). Both glia and neurons were seen to adhere to the Teflon when immunofluorescence tech- niques were used (Figure 2, A, B, C).

4 Discussion

The results of the present study clearly show: 1) that Teflon is compatible to both glia and neuron cells; 2) that a small population of both neurons and glia cells can attach to Teflon in two or three days, possibly less.

Figure 2. A: The adhesion of a group of cells to the Teflon fibers as appeared by immunofluorescence technique.

Neurosurg. Rev. 13 (1990)

302 Ammar et al., Tissue compatibility of Teflon

Figure 2. B: MG monoclonal antibody marker identifes the neurons attached to Teflon fibers. C: Anti-GFAP glia marker recognizes the glia cells attached to the Teflon fiber. Bar = 50 gin.

There are several impor tan t implicat ions of the results of using Teflon as a permanent implant material in neurosurgery. Excessive a t tachment of neural tissue to implanted mater ial could lead to subsequently mechanical damage to adherent tis- sue. In particular, excessive a t tachment of neurog- lial cells might produce glial scarring. Thus our finding that Teflon is relatively inert and not ad- hesive to cells of neural origin to any great extent implies that it is a suitable mater ial for use in microvascular decompression procedures. How- ever, the fact that neural cells can a t tach to Teflon fibers makes it difficult to predict Teflon-tissue interact ion in cases in which Teflon is being im- planted directly into brain tissue. Whether the

abili ty of Teflon to adhere to neural tissue can be used for other purposes than a passive implant such as, for instance, to enhance axonal growth remains a topic for future investigation.

Acknowledgements: We wish to express our warmest thanks to Dr. STEPHEN L. PHILLIPS, Department of Bio- chemistry and Dr. P. HEBDA, Department of Dermatol- ogy, University of Pittsburgh School of Medicine for permitting us to use their laboratory facilities. Especially, thanks to Mrs. D. MEMON and Mrs. R. HALL for their excellent technical help. Also thanks is due to Dr. A. R. MOLLER, Department of Neurosurgery, University of Pittsburgh School of Medicine for his continuous sup- port and advice, and to Mrs. J. Russo for preparation of the manuscript.

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Submitted June 15, 1989. Accepted July 17, 1989.

Ahmed Ammar, M. D. Department of Neurosurgery King Fahd Hospital of the University R O. Box 400 40 A1-Khobar 31952 Saudi Arabia

Neurosurg. Rev. 13 (1990)