Immuno-scanning electron microscopy of collagen types I and III in human vocal fold lamina propria

Objectives: This study was undertaken to identify the types of collagen fibrils in the extracellular matrix of the human vocal fold lamina propria. Methods: Human vocal folds were obtained from 3 autopsy cases less than 65 years of age. The vocal fold specimens were labeled by primary antibodies of anti-type I and anti-type III collagens, and then by secondary antibody conjugated with 15 nm colloidal gold. The specimens were observed with a scanning electron microscope. Secondary electron imaging and backscatter electron imaging of high-resolution field emission scanning electron microscopy were used to detect gold particles indicating immunolabeling. Results: Type III collagen-labeling gold particles were abundant on the fibrils constructing collagenous fibers, whereas type I collagen-labeling gold particles were sparsely present on fibrils in collagenous fibers. A few reticular fibers were labeled by both collagen type I and collagen type III. Conclusions: The results suggest that collagen type I coexists with collagen type III in fibrils of both collagenous fibers and reticular fibers.