Immunopathological study of the larynx. IgA distribution and secretory activity

Progress in Vocal Fold Regenerative Biomaterials: An Immunological Perspective

Vocal folds, housed in the upper respiratory tract, are important to daily breathing, speech and swallowing functions. Irreversible changes to the vocal fold mucosae, such as scarring and atrophy, require a regenerative medicine approach to promote a controlled regrowth of the extracellular matrix (ECM)-rich mucosa. Various biomaterial systems have been engineered with an emphasis on stimulating local vocal fold fibroblasts to produce new ECM. At the same time, it is imperative to limit the foreign body reaction and associated immune components that can hinder the integration of the biomaterial into the host tissue. Modern biomaterial designs have become increasingly focused on actively harnessing the immune system to accelerate and optimize the process of tissue regeneration. An array of physical and chemical biomaterial parameters have been reported to effectively modulate local immune cells, such as macrophages, to initiate tissue repair, stimulate ECM production, promote biomaterial-tissue integration, and restore the function of the vocal folds. In this perspective paper, the unique immunological profile of the vocal folds will first be reviewed. Key physical and chemical biomaterial properties relevant to immunomodulation will then be highlighted and discussed. A further examination of the physicochemical properties of recent vocal fold biomaterials will follow to generate deeper insights into corresponding immune-related outcomes. Lastly, a perspective will be offered on the opportunity of integrating material-led immunomodulatory strategies into future vocal fold tissue engineering therapies.

Local immune status and tumour marker expression in the human larynx

This study examined the local immune status and tumour marker expression in secretions and related tissue specimens from the laryngeal ventricle, comparing individuals with and without head and neck cancer. Laryngeal secretion and mucosal tissue specimens were collected during laryngeal microsurgery or surgical laryngectomy. The laryngeal secretions were found to contain immunological factors such as immunoglobulins G and A and secretory immunoglobulin A. A high level of the tumour marker Cyfra 21-1 was also detected in laryngeal secretions and mucosal tissue. Lows levels of secretory immunoglobulin A and Cyfra 21-1 were seen in the laryngeal mucosal tissue of controls and patients who had previously undergone radiation therapy. The level of secretory immunoglobulin A in laryngeal secretions closely correlated to the level of this immunoglobulin in mucosal tissue. These results indicate that local immunity is present in the human larynx; furthermore, it is strongly affected both by the presence of malignancy and by laryngeal cancer treatments such as irradiation.

Effect of Irradiation on the Human Laryngeal Glands

Objectives:

The present study was conducted to determine the effects of irradiation on the human laryngeal glands.

Methods:

Light and transmission electron microscopic observations were made.

Results:

Granular endoplasmic reticula and Golgi apparatuses were sparse in the cytoplasm of serous and mucous cells in cases with a short duration after radiotherapy. The secretory granules in serous cells had decreased in number. The secretory granules were less electron-dense compared to those in non-irradiated specimens, but were electron-lucent. The mucigen droplets in mucous cells were not as numerous as those in non-irradiated specimens. The discharge of secretory granules and mucigen droplets had decreased. In cases with a long duration after radiotherapy, there were some granular endoplasmic reticula and Golgi apparatuses in the cytoplasm. However, the transmission electron microscopy findings of secretory granules and mucigen droplets were the same as those in the irradiated glands with a short duration after radiotherapy.

Conclusions:

Morphological changes in the irradiated laryngeal glands influenced not only the amount but also the quality of secretions. The above changes lessened the lubrication of the vocal folds, thus causing a voice disorder to some extent. Local immunity and mucociliary transport were also affected. The effects of irradiation on the laryngeal glands partially altered the laryngeal functions.

Age related changes in the distribution of laryngeal glands in the human adult larynx

OBJECTIVE

To understand the defense status of glandular tissue in the human adult larynx, we examined the glandular distribution, concentration and the ratio of the mucous glands in the subglottic and supraglottic larynx.

METHODS

One-hundred and seven adult larynges were examined. The area of the mucosa and glands were measured using an image analyzing system. The correlations of the concentration as well as the ratio of the mucous glands with age were analyzed.

RESULTS

The ratio of the areas occupied by the glandular acini of the subglottis was almost equal to that of infants as we reported earlier. The concentration of the laryngeal glands decreased in higher-aged adults at the level of the supraglottis, but not at the level of the subglottis.

CONCLUSIONS

In comparison to infants, the ratio of laryngeal glands of the human subglottic larynx is rather constant in human adults. However, the supraglottic larynx seems to be influenced by increasing age. The changes deserved in the laryngeal glands predominantly occur in the supraglottic larynx.

A survey of the pattern of glandular distribution in the larynges of human infants

We studied the development of glandular structures and the pattern of distribution of serous and mucous-type glands in the larynges of 77 human infants obtained at autopsy. The subglottic larynx was subjected to quantitative and qualitative analysis, using an image binarization procedure. The areas of mucosa and inner space of the subglottic larynx tended to increase with age. The area occupied by the glands differed considerably in younger infants and the areas of total glands and serous-type glands increased with age. There was no correlation between the area of the mucous glands and age. These findings indicate that local immune function of the secretory glandular system in the larynx of human infants increases with advancing age.

Subglottic airway becomes stable with age in the human infant larynx

Development of the mucosal defence system and its relationship to the pathogenesis of laryngeal diseases was studied by examining the changes in the laryngeal structures at the level of subglottic larynx of 59 human infants who died within 1 year of birth. By making a transverse section at the level of the cricoid cartilage, the area and diameter of each subglottic structure were examined using an image analysis system. The results were analysed, not only by their age at death, but also based on the total development score. The areas of the whole structure, cricoid ring, subglottic mucosa and inner cavity (available area) increased in close correlation with the total development score. In contrast to the increased diameter of the inner cavity, the thickness of the mucosa was almost the same size. These results indicate the stability of the subglottic airway with advancing age in the human infant larynx.

Age-related changes in the human laryngeal glands

The present study was conducted to determine age-related changes in the human laryngeal glands by means of excised human adult larynges. Scanning and transmission electron microscopic observations were made. The results obtained are summarized as follows. 1) Granular endoplasmic reticulum and Golgi apparatus were sparse in the cytoplasm of serous and mucous cells. 2) Secretory granules in serous cells had decreased in number. 3) Secretory granules were less electron-dense compared to those in younger adult specimens, but were electron-lucent. 4) Mucigen droplets in mucous cells were not as numerous as those in younger adults. 5) Discharge of secretory granules and mucigen droplets had decreased. 6) Age-related morphologic changes in the laryngeal glands influenced not only the amount but also the quality of secretions. 7) The above changes lessened lubrication of the vocal folds, thus causing aging of the voice to some extent. 8) Local immunity and mucociliary transport were also affected. 9) Age-related changes in the laryngeal glands partially altered laryngeal function.

Expression of epithelial membrane antigen and secretory component in carcinomas of the laryngeal ventricle, epiglottis and vocal cord

Expression of epithelial membrane antigen (EMA) and secretory component (SC) in 11 laryngeal carcinomas from the laryngeal ventricle was studied immunohistochemically and the results were compared with findings in carcinomas originating from the epiglottis and vocal cord. EMA was almost constantly present in laryngeal carcinomas of each type, while the expression of SC was observed in 7 of 11 (64%) ventricle carcinomas, 9 of 34 (26%) carcinomas from the epiglottis and 2 of 11 (18%) carcinomas from the vocal cord. In 4 ventricle carcinomas, immunostaining for SC was intense. It would appear that some carcinomas in the laryngeal ventricle originate from cells of the secretory glandular acini or the epithelium.

Immunohistopathology of variations of human olfactory mucosa

The characteristics of the human olfactory mucosa were studied immunohistologically. Regular, zonal distribution of the supporting cells, multilayered olfactory receptor cells and basal cells was commonly found in the olfactory mucosa of the human fetus. In contrast, most of the olfactory mucosa in the adult varied to some extent. In the relatively thick, slightly degenerated olfactory mucosa, olfactory marker protein positive receptor cells were arranged irregularly. The most common evidence for variation was the decrease or disappearance of the olfactory receptor cells. Serous-type lactorferrin-containing glandular acini were characteristically found beneath degenerated epithelium. Islands of respiratory epithelium were also seen. The ductules of the Bowman's glands were distended and the openings of these ductules were wide. There was invagination or epithelial cell processes into the glandular lumina. These findings suggest that the epithelial cells of Bowman's glands play an important role in the regeneration of the human olfactory mucosa.