Immunogold EM localization of neurochemicals in human pulmonary neuroendocrine cells

The pulmonary neuroepithelial body microenvironment represents an underestimated multimodal component in airway sensory pathways

Exciting new imaging and molecular tools, combined with state-of-the-art genetically modified mouse models, have recently boosted interest in pulmonary (vagal) sensory pathway investigations. In addition to the identification of diverse sensory neuronal subtypes, visualization of intrapulmonary projection patterns attracted renewed attention on morphologically identified sensory receptor end-organs, such as the pulmonary neuroepithelial bodies (NEBs) that have been our area of expertise for the past four decades. The current review aims at providing an overview of the cellular and neuronal components of the pulmonary NEB microenvironment (NEB ME) in mice, underpinning the role of these complexly organized structures in the mechano- and chemosensory potential of airways and lungs. Interestingly, the pulmonary NEB ME additionally harbors different types of stem cells, and emerging evidence suggests that the signal transduction pathways that are active in the NEB ME during lung development and repair also determine the origin of small cell lung carcinoma. Although documented for many years that NEBs appear to be affected in several pulmonary diseases, the current intriguing knowledge on the NEB ME seems to encourage researchers that are new to the field to explore the possibility that these versatile sensor-effector units may be involved in lung pathogenesis or pathobiology.

Pathogenesis of Interstitial Lung Disease in Children and Adults

Interstitial lung diseases (ILDs) occur across the lifespan, from birth to advanced age. However, the causes, clinical manifestations, histopathology, and management of ILD differ greatly among infants, older children, and adults. The historical approach of classifying childhood ILD (chILD) using adult classification schemes may therefore have done more harm than good. Nevertheless, identification of novel forms of chILD in the past decade, such as surfactant metabolism dysfunction disorders and neuroendocrine cell hyperplasia of infancy (NEHI), as well as genomic analysis of adult ILDs, has taught us that identical genotypes may result in distinct phenotypes at different ages and developmental stages, and that lung developmental pathways and cellular phenotypes are often recapitulated in adult ILDs. Thus comparison of the pathophysiology of ILD in children and adults in the context of lung development is useful in understanding the pathogenesis of these disorders, and may lead to novel therapeutic interventions for ILDs at all ages.

A confocal microscopic study of solitary pulmonary neuroendocrine cells in human airway epithelium

BACKGROUND

Pulmonary neuroendocrine cells (PNEC) are specialized epithelial cells that are thought to play important roles in lung development and airway function. PNEC occur either singly or in clusters called neuroepithelial bodies. Our aim was to characterize the three dimensional morphology of PNEC, their distribution, and their relationship to the epithelial nerves in whole mounts of adult human bronchi using confocal microscopy.

METHODS

Bronchi were resected from non-diseased portions of a lobe of human lung obtained from 8 thoracotomy patients (Table 1) undergoing surgery for the removal of lung tumors. Whole mounts were stained with antibodies to reveal all nerves (PGP 9.5), sensory nerves (calcitonin gene related peptide, CGRP), and PNEC (PGP 9.5, CGRP and gastrin releasing peptide, GRP). The analysis and rendition of the resulting three-dimensional data sets, including side-projections, was performed using NIH-Image software. Images were colorized and super-imposed using Adobe Photoshop.

RESULTS

PNEC were abundant but not homogenously distributed within the epithelium, with densities ranging from 65/mm2 to denser patches of 250/mm2, depending on the individual wholemount. Rotation of 3-D images revealed a complex morphology; flask-like with the cell body near the basement membrane and a thick stem extending to the lumen. Long processes issued laterally from its base, some lumenal and others with feet-like processes. Calcitonin gene-related peptide (CGRP) was present in about 20% of PNEC, mainly in the processes. CGRP-positive nerves were sparse, with some associated with the apical part of the PNEC.

CONCLUSION

Our 3D-data demonstrates that PNEC are numerous and exhibit a heterogeneous peptide content suggesting an active and diverse PNEC population.

G and D cells in rat antral mucosa: An immunoelectron microscopic study

AIM: To investigate the gastrin secreting cells (G cells) and the somatostatin secreting cells (D cells) of antral mucosa in rats at the ultrastructural level.

METHODS: Revised immunoelectron microscopic technique was used to detect the G cells and D cells in rat antral mucosa through gastrin and somatostatin antibodies labeled by colloidal gold. Also the relevant quantitative analysis regarding the granular number of colloidal gold in G cells and in D cells was conducted.

RESULTS: Immunological granules of colloidal gold were distributed in G cells and D cells. Gastrin labeled golden granules or somatostatin labeled ones presented mainly as lobation-like or island-like congeries. Most of the golden congeries were observed dissociated in cytoplasms of G cells or D cells, near the basement membrane. A few golden congeries were located in nuclei. The number of golden granules in one G cell was around 107.04 ± 19.68 and was 83.36 ± 17.58 in one D cell.

CONCLUSION: Gastrin secreting granules are located in cytoplasms and nuclei of G cells, and somatostatin secreting granules both in cytoplasms and in nuclei of D cells. The number of golden granules can be quantitatively analyzed to determine the relative amount of gastrin secreting granules or somatostatin secreting granules.

The diffuse endocrine system: from embryogenesis to carcinogenesis

In the present review we will summarise the current knowledge about the cells comprising the Diffuse Endocrine System (DES) in mammalian organs. We will describe the morphological, histochemical and functional traits of these cells in three major systems gastrointestinal, respiratory and prostatic. We will also focus on some aspects of their ontogeny and differentiation, as well as to their relevance in carcinogenesis, especially in neuroendocrine tumors. The first chapter describes the characteristics of DES cells and some of their specific biological and biochemical traits. The second chapter deals with DES in the gastrointestinal organs, with special reference to the new data on the differentiation mechanisms that leads to the appearance of endocrine cells from an undifferentiated stem cell. The third chapter is devoted to DES of the respiratory system and some aspects of its biological role, both, during development and adulthood. Neuroendocrine hyperplasia and neuroendocrine lung tumors are also addressed. Finally, the last chapter deals with the prostatic DES, discussing its probable functional role and its relevance in hormone-resistant prostatic carcinomas.

The pulmonary neuroendocrine system: the past decade

The pulmonary neuroendocrine system consists of specialized airway endocrine epithelial cells, associated with nerve fibres. The epithelial cells, the pulmonary neuroendocrine cells (PNEC), can be solitary or clustered to form neuroepithelial bodies (NEB). During the last thirty years, the pulmonary neuroendocrine system has been intensively investigated and much knowledge of its function has been obtained. This text reviews work which dates from the last ten years. In this period, the picture of the pulmonary neuroendocrine system we previously had, has not fundamentally changed. The pulmonary neuroendocrine system is still regarded as an oxygen sensitive chemoreceptor with local and reflex-mediated regulatory functions, and as a regulator of airway growth and development. Continuing research has much more refined this picture. This text reviews several aspects of the pulmonary neuroendocrine system: phylogeny, the amine and peptide content of its epithelial cells, ontogeny and influence on lung development, the influence of hypoxia and nonhypoxic stimuli, immunomodulatory function, innervation and pathology. Among the discoveries of the past decade, three stand out prominently because of their great significance: additional proof that the neural component of the pulmonary neuroendocrine system is sensory, sound experimental evidence that PNEC stimulate airway epithelial cell differentiation and the discovery of a specific membrane oxygen receptor in the PNEC.