| Backround: Vacol fold scarring following inflammation, trauma, surgery isthe mainly cause of a significant dysphonia. Previous studies of vocal fold scar in other animal models indicated that the scar generally developed in the lamina propria (LP). The LP consists of various extracellular matrix (ECM) components, such as fibrous proteins, glycoproteins, and glycosaminoglycans that contribute to maintaining the structure of the LP. The biomechanical properties of the vocal folds are determined largely by the relationship, density, and organization of the ECM components. We tried to establish rat model of vocal fold scar in this study, and analyzed the expression and distribution of collagen III and fibronectin at various time in the initial repair stage after acute vocal fold injury.Materials and Methods: Forty-five Spragua-Dawley rats (4 to 6 months old)were used in present study. The average body weight was about 420g. The vocal folds in 40 SD rats were visualized by 1.9mm-diameter endoscope. Bilateral vocal folds were stripped by microforceps. Four rats were dead after surgery. The remaining survived until the time of sacrifice were randomly divided into 4 groups(named as A, B, C, D group). All the ratlarynges of the 4 groups were harvested at 3d, 5d, 7d, 14d respectively after surgery. Five rats regarded as normal control were sacrificed without any performance. All samples were fixed in 10% formaldehyde solution, and then embedded in paraffin. Four-micron-thick sections were prepared, and stored at 4℃. Collagen III and fibronectin were detected by immunohistochemical method. The Stained area of each scared or control vocal fold in each slice was analyzed with an image analysis system specially developed for quantification of histologic images. All the figures were analyzed statistically with SPSS 13.0 software. Results:1. HE staining : On postoperative day 3, the normal epithelium and lamina propria of vocal fold were absent, and the thyroarytenoid muscle was covered with inflammatory granulation tissue and little collagen; on day 5, a lot of inflammatory granulation tissue and collagen appeared, and regenerating stratified epithelium was seen; by day 7, the epithelium had almost covered the wound site, and collagen fibers of LP are disorganized and in thick bundles; by day 14, ail animals exhibited a single epithelial cell layer at the wound site, and collagen fibers organized in the LP.2. immunohistochemical stainingIn control group: collagen type III was predominant and was especially present in both superficial and deep layers of the LP. Fibronectin was observed mainly in the basal membrane zone, and very little was in the superficial layer of LP. Study groups: the positive staining of collagen III and fibronectin was seen around the injured sites during days 3 to 14. Both expression were unevenly strong, widespread, and significantly greater than in the controls(P < 0.05), but statistically unchanged from day 3 to day 14(P>0.05). Theexpression of collagen III showed a significant positive correlation with the expression of fibronectin( γ =0.667, P< 0.001).Conclusion1. Although rat is smaller than canine or rabbit, the rat vocal foldcan be injured accurately by monitoring with telescope. The result suggests some characteristics of vocal fold wound healing and provides experimental base for further understanding the mechanism of vocal fold scar development.2. Both collagenIII and fibronectin expressed strongly from days 3 to days 14 after vocal fold injury. And the expression of collagenIII was positively correlated with the expression of fibronectin. This relationship indicated that fibronectin may compose the scaffold for the deposition of collagen III. CollagenIII stably expressed at a high level during 14days. |
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