1 Department of Obstetrics and Gynecology, Fujita Health University, School of Medicine, 198 Dengakugakubo, Kutsukakecho, Toyoake, Aichi, Japan 470-1192
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Abstract |
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Key words: adhesion/adhesion prevention/hyaluronic acid/murine uterine horn model/reproductive surgery
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Introduction |
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Hyaluronic acid (HA) is a linear polysaccharide with repeating disaccharide units, naturally occurring from extracellular matrix components. Experimental and clinical data using various contents of HA solution have suggested that covering an operation field with soluble HA would reduce postoperative adhesions (Rogers et al., 1997; Thornton et al., 1998
).
This report evaluates the efficacy of a soluble barrier fluid composed of high molecular weight HA, which is different from conventional HA in its molecular makeup, in reducing postoperative adhesion formation in the murine uterine horn model.
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Materials and methods |
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Examination of the adhesion prevention effect of HA
Materials
The high molecular weight HA was manufactured by Denkikagaku Kogyo Co. Ltd (Tokyo, Japan). It has a molecular weight of 1.9x106 and is purified by the fermentation method; it is sterile and non-pyrogenic, with neutral pH, and is manufactured with a high intrinsic viscosity twice that of conventional HA.
Methods
HA was administered into the abdominal cavity of 80 ICR mice of 7 weeks old. The HA was adjusted to concentrations of 0.3, 0.5, 0.75 and 1.0, and 3 ml of each was intraperitoneally injected into 13, 25, 31 and 11 mice respectively, immediately before closing the wound at the end of the surgery to induce adhesions (by the iodine abrasion method: see Results below). For the 25 control mice, 3 ml of physiological saline was injected under the same conditions. In order to examine the effect of different molecular weights of HA, 3 ml of sodium hyaluronate [HA-S: having molecular weight 0.61.2x106 and collected from rooster combs by extraction (Swann, 1968); Seikagaku Kogyo Co. Ltd, Tokyo, Japan] was injected into 11 mice in the same manner.
Concentrations of intraperitoneally administered HA were measured daily by high performance liquid chromatography (HPCL) using a column of Shodex OHpak KB806 with flow rate of 0.5 ml/min with 0.1 mol NaNO3 (Beaty et al., 1985). This was used to examine the metabolism of HA in the abdominal cavity.
The adhesion prevention effects were determined at a second-look laparotomy on the 7th postoperative day. The adhesion scores were measured using a 03 point scale for the following four states: 0, no adhesion (); 1, slight adhesion (1+): adhesion of ~1 mm; 2, moderate adhesion (2+): adhesion of ~2 mm; and 3, severe adhesion (3+): adhesion of >3 mm.
The adhesion suppressing effects were measured against the control group. A suppressing effect of 1 point or more on the 03 scale was interpreted as a preventive effect.
Statistical analysis was performed using the 2-test where appropriate, Fisher's exact test or Student's t-test. A P value < 0.05 was considered statistically significant.
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Results |
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Discussion |
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In the present study, three methods were tested to induce adhesion formation: suture, desiccation with electrosurgery, and iodine abrasion. Other reported adhesion forming methods include wounds made by CO2 laser (Urman and Gomel, 1991), mechanical stimulation (Treutner et al., 1995
), and abrasion using sandpaper (Shushan et al., 1994
), all reported the prevention effects for de-novo adhesions. The method using iodine abrasion, which in our hands showed the best reproducibility and had a favourable adhesion formation rate, was used in the present adhesion prevention experiment.
The adhesion prevention effect of HA is clarified by our experiment, and it was found that lower concentrations were more effective. This result agrees with a report on the relationship between the viscosity of HA and its adhesion prevention effect (Burns et al., 1995), and with a report on the better effect of HA when used at lower viscosity and lower molecular weight (Rogers et al., 1997
). On the other hand, it has been reported that 1% HA concentration is most effective (Shushan et al., 1994
). The concentration and amount of HA to administer in future to human beings needs further experimentation, since the results obtained in this study were from mice.
The adhesion prevention mechanism of HA is still unclear and it is difficult to throw any more light on it from our present experiment. In another study, ferric hyaluronate gel with a half-life in the peritoneal cavity approximately twice that of conventional HA reduced significantly the number, severity and extent of adhesion formation in the abdominal cavity after laparotomy (Thornton et al., 1998). Considering the rapid decline of the intraperitoneal concentration of HA (lowered to normal value on the 4th day; half-life ~24 h), it can be concluded that the prevention mechanism is working at an extremely early stage of adhesion formation. Therefore, the co-operative adhesion suppression of fibroblasts and/or the platelet coagulation suppression can be assumed to be related to this mechanism (Shushan et al., 1994
), in addition to the coating effect which was shown by the shallower tissue injury crater depth on histological examination after preoperative HA administration (Urman et al., 1995). The adhesion suppression mechanism is known to be associated with the appearance of various cytokines, such as epidermal growth factor or transforming growth factor-ß, that suppress the activity of tissue repair cells in the postoperative period via macrophages (Fukazawa et al., 1989
). Further research is needed to explain the mechanism fully.
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Acknowledgments |
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Notes |
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References |
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Submitted on November 11, 1998; accepted on February 24, 1999.