Irradiated macula flava in the human vocal fold mucosa

There have been no investigations regarding radiation-induced damage on human maculae flavae (MFs) in the vocal fold mucosa (VFM) and on stellate cells (SC) in the MF. The VFM, especially MF, after irradiation was investigated histologically.

The lamina propria of the irradiated VFM was investigated in 5 human adult vocal folds by light and electron microscopy.

Fibroblasts in the irradiated Reinke's space (RS) showed no morphological changes. Irradiated RS was composed of fibrous tissue with increased collagenous fibers. Most of the SC in the irradiated MF had dark cytoplasm. The nucleus-cytoplasm ratio was relatively small, but there were few intracellular organelles in the cytoplasm. Some SC showed degeneration. Fewer vesicles were present at the periphery of the cytoplasm. The MF was rather deficient in fibrous components. Elastic and collagenous fibers immediately surrounding SC in the irradiated MF were lower in number than usual, but elastic fibers and collagenous fibers composed of irregular collagen fibrils could be detected at a distance from SC. It was suggested that precursors of collagenous and elastic fibers synthesized by SC were damaged by irradiation. Radiation sensitivity of SC was higher than that of conventional fibroblasts in RS, and SC appeared to decrease their level of activity.

Radiation sensitivity of SC was different from that of conventional fibroblasts. Radiation induced not only changes in the lamina propria of the VFM but also dysfunction of the SC in the MF, and is one of the causes of voice disorders after irradiation.