Pulmonary Neuroendocrine Cell System in Pediatricand Adult Lung DiseaseJOHN R. GOSNEY*Department of Pathology, University of Liverpool, Liverpool L69 3BX, United Kingdom

KEY WORDS lung; neuroendocrine cells; peptides; tumourlets

ABSTRACT In human lungs affected by naturally occurring pulmonary disease, the pulmonaryneuroendocrine cell system, which is normally arranged in a sparse but even distributionthroughout the respiratory tract, increases in size. It is likely that the stimulus for this is pulmonaryinjury and that its purpose is the paracrine regulation of the restoration of pulmonary tissues totheir normal state, an hypothesis supported by studies of animal lungs subjected to experimentalinjury as well as of the development of human and animal lungs in utero. Initially, this increaseinvolves the development of interrupted rows of neuroendocrine cells. In the later stages, however,development of more disorderly intraepithelial aggregates can occur and the small, locally invasiveneuroendocrine cell lesions known as tumourlets may occasionally result. Both of these latterstructures often contain secretory products not found in the neuroendocrine cells of normal humanlungs, probably indicating a derangement of what appears to be a fundamentally physiologicalresponse. It is likely that, in some circumstances, this disorderly change may contribute topulmonary disease as well as being the result of it. Microsc. Res. Tech., 37:107–113, 1997.r 1997 Wiley-Liss, Inc.

INTRODUCTIONIn common with other epithelia, that which lines the

airways and alveoli of the lungs contains within it asystem of widely dispersed amine and peptide-secret-ing neuroendocrine cells which acts in concert withhigher neural and endocrine control systems to main-tain pulmonary homeostasis. The precise ways in whichit does this are currently unclear, but roles in mediatingthe pulmonary response to hypoxia and controlling thegrowth of pulmonary tissues during both pulmonarydevelopment and following injury are gradually beingdefined.The purpose of this article is to review how studies of

the pulmonary neuroendocrine cell system in naturallyoccurring human pulmonary disease have contributedto the development of these ideas. First, however, abrief overview of the characteristics of the pulmonaryneuroendocrine cell system of normal human lungs willbe given.

THE NORMAL HUMAN PULMONARYNEUROENDOCRINE CELL SYSTEM

In healthy, adult human lungs, pulmonary neuroen-docrine cells are found at all levels of the respiratorytree from the larynx to the alveoli, but are concentratedmainly in intrapulmonary bronchi and terminal bron-chioles, where their distribution is remarkably regular(Figs. 1 and 2a). They have an overall concentrationwithin the lung of about one neuroendocrine cell forevery 2,500 epithelial cells (Gosney et al., 1988). Thevast majority of these cells are solitary (Fig. 3), withonly a very small number forming the innervatedcorpuscular structures which Lauweryns and Peuskens(1972) have termed neuroepithelial bodies (Fig. 4). Inthe neonate and infant, pulmonary neuroendocrine

cells are probably present at a greater concentrationthan in the adult, although whether their absolutenumber is greater is unclear (Gosney, 1992). Proportion-ally more of them are in the form of neuroepithelialbodies (Gosney, 1993). Three peptides and one aminehave been confirmed unequivocally as secretory prod-ucts of normal human neuroendocrine cells. These aregastrin-releasing peptide (GRP; Wharton et al., 1978),which is the human analogue of amphibian bombesin,calcitonin (CT; Becker et al., 1980), calcitonin gene-related peptide (CGRP; Johnson and Wobken, 1987)and serotonin (5-hydroxytryptamine; 5-HT; Lauwerynset al., 1982). Others, including leucine (leu-) enkepha-lin, adrenocorticotrophin (ACTH), the subunits of hu-man chorionic gonadotrophin (HCG), cholecystokinin(CCK), somatostatin (ST), substance P and the endothe-lins, have all been reported in such cells in man(Gosney, 1992; Polak et al., 1993), but not yet confirmedby repeated demonstration. In healthy adult humanlungs, about 65% of neuroendocrine cells contain GRPand the vast majority of the rest CT (Gosney et al.,1988).

INFLAMMATORY AND FIBROTICPULMONARY DISEASE

Most studies of the pulmonary neuroendocrine cellsystem in human pulmonary disease have involvedconditions characterised or complicated by inflamma-tion, often with an infective element. These have in-cluded bronchial asthma (Stanislawski et al., 1981),

*Correspondence to: Dr. J.R. Gosney, B.Sc., M.D., M.R.C.Path., Reader inPathology, Department of Pathology, University of Liverpool, P.O. Box 147,Liverpool L69 3BX, UKAccepted 10 May 1995.

MICROSCOPY RESEARCH AND TECHNIQUE 37:107–113 (1997)

r 1997 WILEY-LISS, INC.

pneumonia (Allibone and Gosney, 1990), chronic bron-chitis and emphysema (Gosney et al., 1989a), bronchiec-tasis (Gould et al., 1983; Tsutsumi et al., 1983), cysticfibrosis (Dovey et al., 1989; Johnson et al., 1988; Wolf etal., 1986) and eosinophilic granuloma (Aguayo et al.,1990). All describe increased numbers of neuroendo-crine cells in comparison with normal lungs. Thisprocess produces two characteristic patterns: inter-rupted rows of cells applied to the basement membraneand larger, disorderly nodular aggregates, in which thecells appear to pile up within the epithelial layer (Figs.2b, 5, 2c and 6). It is likely that the first of thesepatterns is seen in the earlier stages of the response,the latter developing only when the process is moreflorid or prolonged. If sufficiently extended, it is pos-sible that tumourlets may eventually develop (Figs. 2dand 7). First described by Whitwell (1955) and muchdebated about since, these are small (2–3 mm) aggre-gates of pulmonary neuroendocrine cells which formlesions considerably larger than the nodular aggre-gates described above and which lose their relationshipto the pulmonary epithelium, extending across thebasement membrane to grow into the underlying tis-sues, developing a conspicuously fibrous stroma.As this pattern of change develops, the nature of the

secretory products of the neuroendocrine cells alters. In

the earlier stages, CT appears to become the dominantpeptide, a situation different from that in healthy lungswhere, as stated above, GRP predominates (Gosney,1992). This may underlie the hypercalcitoninaemia andhypercalcitoninuria which have been consistently de-monstrable in patients with inflammatory pulmonarydisease (Becker et al., 1981, 1984; Galan-Galan et al.,1982; Mulder et al., 1980; Schwartz et al., 1979; Yiakou-makis et al., 1987). In addition, however, substancesnot found in normal human pulmonary neuroendocrinecells become demonstrable within them as their num-bers increase, especially when nodular aggregates de-velop. The most frequently demonstrable is ACTH, butbeta-endorphin, ST, vasoactive intestinal polypeptide(VIP), human growth hormone (HGH) and subunits ofHCG have all been described (Fukayama et al., 1990;Gould et al., 1983; Sheard and Gosney, 1996; Tsutsumiet al., 1983). Such substances have also been demon-strated in tumourlets (Fukayama et al., 1990; Gosneyet al., 1990; Tsutsumi, 1989; Tsutsumi et al., 1983). Notsurprisingly, elevated serum levels of ACTH have beendescribed in subjects with inflammatory pulmonaryconditions such as tuberculosis, chronic bronchitis andemphysema and pulmonary abscess (Ayvazian et al.,1975; Dupont et al., 1984; Gewirtz and Yalow, 1974;Wolfsen and Odell, 1979), in whom its high molecularweight form and non-suppressibility are against itsbeing of pituitary origin, supporting its source as theneuroendocrine cells in the diseased lung.

PULMONARY HYPERTENSIONAlthough structural changes in pulmonary blood

vessels are seen whenever the pressure within them is

Fig. 1. A length of epithelium from an intrapulmonary bronchusshowing five typical evenly spaced solitary neuroendocrine cells. Thatat the top of the figure has conspicuous cytoplasmic processes.Avidin-biotin complexmethod for chromograninA. Original magnifica-tion 3375.

Fig. 2. Schematic representation of the pattern of increase ofpulmonary neuroendocrine cells described in the text. a: The normaleven spacing of solitary cells in the pulmonary epithelium (see alsoFigure 1). b: The earliest change seen during their increase, theformation of interrupted rows of cells still applied to the basementmembrane (see also Figure 5). In (c), the cells have begun to formnodular aggregates (see also Figure 6). In (d), the likely mechanism ofthe formation of a tumourlet is shown, the neuroendocrine cellsbreaching the basement membrane to grow into the immediatelyadjacent tissues (see also Figure 7).

108 J.R. GOSNEY

significantly raised, only in that form of pulmonaryhypertension known as plexogenic pulmonary arteriopa-thy (PPA) is the striking triad of fibrinoid vasculosis,concentric laminar fibrosis and plexiform lesions, fromwhich the entity takes its name, a feature (Hatano andStrasser, 1975). Crucial to the development of laminarfibrosis and plexiform lesions is the proliferation andmigration of vascular myofibroblasts (Smith et al.,1990), a process which is associated with markedlyincreased numbers of pulmonary neuroendocrine cells,especially those containing GRP (Gosney et al., 1989b).This change, which is most marked when activity ofmyofibroblasts is at its greatest and wanes as the PPAages, is usually absent in lungs affected by pulmonaryhypertension not characterized by PPA, even whenelevation of pulmonary arterial pressure is marked(Gosney et al., 1989b; Madden et al., 1994). It takes theform of both interrupted rows and nodular aggregates.Unlike the increase which occurs in inflammatorypulmonary disease, that in lungs affected by PPA bearsno relationship to inflammation, nor does it appear tobe accompanied by synthesis of peptides not normallyfound in healthy lungs.

NEONATAL LUNG DISEASEBecause of the likely role of the pulmonary neuroen-

docrine cell system in the growth and development ofthe lung (Miller, 1994), changes in the system inpulmonary disorders occurring early in postnatal life

have attracted particular interest. In this regard, anumber of studies have investigated infantile hyalinemembrane disease and bronchopulmonary dysplasia.The first of these is a fundamentally destructive condi-tion of early extrauterine life due essentially to exuda-tion of plasma components and usually the result ofsurfactant deficiency in preterm infants. The second isan exaggeration and disturbance of the processes ofhealing which follows the treatment of hyaline mem-brane disease with mechanical ventilation and highlevels of oxygen.The paucity of pulmonary neuroendocrine cells in

hyalinemembrane disease (Ghatei et al., 1983; Johnsonet al., 1982, 1985, 1988) probably is a consequencemerely of their loss as part of the generalised epithelialdamage, although depletion of their content may inpart be responsible for their apparent decrease innumber. In contrast, the changes seen in bronchopulmo-nary dysplasia involve a remarkable increase in thenumber of neuroendocrine cells which accompanies theflorid growth of epithelial and mesenchymal elementsthat characterizes the condition (Johnson and Wobken,1987; Johnson et al., 1982, 1985, 1988; Stahlman andGray, 1984; Stahlman et al., 1985). The pattern ofchange here is indistinguishable from that seen in theadult pulmonary diseases discussed above but is particu-larly florid, so that nodular aggregates are common(Fig. 6). All of the peptides normally found in healthy

Fig. 3. A typical human solitary pulmonary neuroendocrine cell.Avidin-biotin complex method for chromograninA, original magnifica-tion 31,500.

Fig. 4. A discrete, compact neuroendocrine cell cluster from anormal human lung, almost certainly a true neuroepithelial body.Avidin-biotin complex method for chromograninA, original magnifica-tion 31,500.

109NEUROENDOCRINE CELLS IN DISEASED LUNGS

human lungs have been demonstrated in neuroendo-crine cells in bronchopulmonary dysplasia, but it isuncertain which, if any, predominates.The pulmonary neuroendocrine cell system has been

examined in a miscellany of other neonatal conditions.Thus, these cells have been reported as absent, reducedin number or increased in hypoplastic lungs with orwithout anencephaly (Sunday et al., 1988), increased innumber in the Wilson-Mikity syndrome (Cutz et al.,1984) and after brain stem injury due to birth asphyxia(Gillan et al., 1986), and unchanged after birth as-phyxia uncomplicated by brain stem injury (Gillan etal., 1986) and in anencephaly (Ito et al., 1987).

SUDDEN INFANT DEATH SYNDROMEThe diagnosis of sudden infant death syndrome is, by

definition, one of exclusion, many theories having beenproposed to explain it (Valdes-Dapena, 1980). Centralto many of the suggested explanations is hypoxia but,despite their putative role in chemoreception, pulmo-nary neuroendocrine cells have been surprisingly littlestudied in the condition. In 1989, however, Gillan et al.described a significantly greater number of these cellsas well as their more peripheral extension in the lungsof 25 children dying of the syndrome when comparedwith lungs from 20 age-matched controls. Perrin et al.(1991) found a similar increase in GRP-containingneuroendocrine cells in 25 infants with a diagnosis of

sudden infant death syndrome in comparison withcontrols, and also described an increase in the size ofneuroendocrine cell clusters.

CAUSES AND CONSEQUENCESOF CHANGES IN THE SYSTEM

What can be learned from the changes describedabove? A striking feature of them is their stereotypednature, the increase in numbers of pulmonary neuroen-docrine cells in diseased lungs seeming generally tofollow the predictable sequence illustrated in Figure 2.The morphological changes are accompanied by analteration in the secretory products of the cells suchthat, as they become more disordered, peptides notnormally found in them make an appearance. It istempting to speculate that what is, in most cases, ameasured physiological response of the system mightoccasionally become excessive, the increasingly disor-derly morphology of the change going hand-in-handwith expression of abnormal secretory products.These changes are not always seen, however and, in

some chronic pulmonary diseases, their absence seemsdifficult to explain at first sight. An example is diffusepulmonary fibrosis, whether idiopathic or due to condi-tions like asbestosis, in which neuroendocrine cells arenormal or even reduced in number (Wilson et al., 1993),a picture contrasting markedly with the large numbersof cells seen in eosinophilic granuloma (Aguayo et al.,

Fig. 5. An interrupted row of neuroendocrine cells in a lungaffected by lobar pneumonia (note the neutrophils in the lumen).Avidin-biotin complex method for chromograninA, original magnifica-tion 3600.

Fig. 6. A large, disorderly nodular aggregate of neuroendocrinecells immunolabelled for GRP in a neonatal lung affected by broncho-pulmonary dysplasia. Avidin-biotin complex method for GRP, originalmagnification 3600.

110 J.R. GOSNEY

1990), in which disease fibrosis is also a central feature.Perhaps the explanation lies in the inflammatory com-ponent of diseases like eosinophilic granuloma; it isnotable how either inflammation or active regeneration(rather than fibrosis) of pulmonary tissues is almostalways present as part of the disease process whenpulmonary neuroendocrine cells increase in number.The major exception to this generality is hypertensivepulmonary vascular disease characterized by PPA, butthis group of conditions is probably unique in thenature of its pathogenetic relationship with the pulmo-nary neuroendocrine system. Individual, perhaps ge-netic variation can also never be excluded.What is the mechanism of this increase in endocrine

cell number? Although often referred to as ‘‘hyperpla-sia’’ or ‘‘proliferation,’’ such terms are not really appro-priate implying, as they do, that cell division is respon-sible, and there is no good evidence for this. Mitosesoccur in pulmonary neuroendocrine cells in culture(Carabba, 1985) and are undoubtedly seen in fetallungs during the period of rapid expansion of theirpopulation, but are rarely, if ever, found in late gesta-tion or postnatally (Cutz et al., 1985; Sarikas et al.,1985). Hernandez-Vasquez et al. (1978) have shownthat fully differentiated pulmonary neuroendocrine cellsdo not take up tritiated thymidine. Linnoila (1982) hasshown how, when this isotope is given to normalhamsters, it is taken up not by pulmonary neuroendo-

crine cells, but by the Clara-like cells immediatelyadjacent to them. This is followed, after about 8 days,by its appearance within the pulmonary neuroendo-crine cells themselves, suggesting that the adjacentnon-neuroendocrine cells which were first labelled di-vide and develop an endocrine phenotype. Studies ofregeneration of the epithelium of pieces of guinea pigairway transplanted into mice (DiAugustine et al.,1984) show that neuroendocrine cells appear late in theprocess of renewal and apparently from undifferenti-ated epithelial precursors. In an autoradiographic studyof the development of clusters of pulmonary neuroendo-crine cells in newborn hamsters, Hoyt et al. (1990)describe how neuroendocrine cells heavily labelled withtritiated thymidine were seen in the periphery oflightly labelled already-developed clusters and prob-ably represented cells newly recruited from adjacentnon-endocrine epithelium. Most recently, Sunday et al.(1994) studied indices of proliferation in the epitheliumof the lungs of Syrian golden hamsters in which num-bers of pulmonary neuroendocrine cells were greatlyincreased by administration of carcinogens in an hyper-oxic environment. They found that non-neuroendocrinecells rather than the neuroendocrine cells themselveswere proliferating. They concluded that the increase inneuroendocrine cells arose by a process of differentia-tion of non-neuroendocrine cells rather than by divisionof neuroendocrine cells themselves.All this evidence points to accelerated differentiation

of non-neuroendocrine cells as the most importantmechanism underlying the increase in their numberwhich is seen in diseased lungs. A similar mechanism,inwhich an apparent increase in numbers of neuroendo-crine cells results from the appearance of certain neuro-endocrine components in fundamentally non-neuroen-docrine cells, has recently been described (Bousbaa etal., 1994). In this study, antigen sensitization of guineapigs resulted in an increase in chromogranin-A contain-ing cells, but this was inapparent when neuron-specificenolase was used as a marker. The precise interpreta-tion of studies such as this depends, of course, on thecriteria by which one recognizes a cell as bona fideneuroendocrine.Whether accelerated differentiation of non-neuroen-

docrine cells is the only mechanism involved when thechanges in diseased lungs described above occur isunknown. It is easy to envisage such a mechanism asthe cause of interrupted rows of neuroendocrine cells,but the formation of nodular aggregates and of tumour-lets in particular is a disorganized process, suggestingthat more than just an orderly process of differentiationof non-neuroendocrine components might be respon-sible. Studies of the kinetics of the increase in neuroen-docrine cell number in diseased human lungs may shedlight on some of these questions.What might be the stimulus for this increase? Be-

cause of the experimentally proven response of neuro-epithelial bodies of animals to a decrease in oxygenconcentration (Lauweryns andCokelaere, 1973a, 1973b;Lauweryns et al., 1977, 1978, 1983), many authorshave attributed proliferation of the system to thehypoxia which is a common accompaniment to many ofthe diseases discussed above. There is, however, nohard evidence for this. Not only havemost studies of theresponse of the human pulmonary neuroendocrine sys-

Fig. 7. The edge of a tumourlet showing its association withnodular aggregates of neuroendocrine cells in the airway adjacent toit. Avidin-biotin complex method for chromograninA, original magnifi-cation 3375.

111NEUROENDOCRINE CELLS IN DISEASED LUNGS

tem to hypoxia failed to show an effect (Gosney, 1994), itis most unlikely that the groups of proliferating neuro-endocrine cells which appear in these conditions areactually bona fide neuroepithelial bodies anyway; theyare far more likely to be aggregates of solitary cellswhich simply come to lie in juxtaposition as theyincrease in number within the epithelium. Hypoxiamay occasionally be a relevant stimulus to the humanpulmonary neuroendocrine cell system and increasednumbers of neuroepithelial bodies may result (thechanges described in the lungs of children dying of thesudden infant death syndrome are an obvious example),but such a scenario is almost certainly exceptional.If not a response to hypoxia, what might be the

purpose of the increase? The weight of evidence fromthe studies of naturally occurring pulmonary diseasedescribed above as well as that from studies of thepulmonary neuroendocrine cell system in lungs subjectto experimental damage (Gosney, 1992), when added tothat derived from investigations of its function indeveloping lungs in utero (Hoyt et al., 1991; King et al.,1993; Sunday et al., 1990, 1992, 1993), points unargu-ably to a primary role, at least in human beings, in theparacrine regulation of the growth and development ofpulmonary tissues, whether de novo, in developinglungs, or following pulmonary tissue damage.Finally, might the products released from the cells of

the system ever contribute to pulmonary pathology? Ithas already been described how increased numbers ofneuroendocrine cells parallel the activity of myofibro-blasts in PPA, suggesting a role for GRP or otherpulmonary peptides in its pathogenesis, a possibilitygiven recent support by a study of CGRP-containingneuroendocrine cells during hypoxic pulmonary vascu-lar remodelling in the rat (Roncalli et al., 1993). Experi-ments in animals have suggested that these pulmonaryneuroendocrine cell products might stimulate fibrogen-esis (Johnson et al., 1980; Sheppard et al., 1982) andothers have proposed such a role in causing the fibrosiswhich accompanies or results from a variety of pulmo-nary diseases (Aguayo et al., 1990, 1992; Johnson andGeorgieff, 1989). A recent study of the pulmonaryneuroendocrine cell system in a series of human lungsaffected by diffuse pulmonary fibrosis failed to provideany evidence for this (Wilson et al., 1993), but itremains a possibility. Perhaps a role in the exuberantand excessive proliferation of epithelial as well asmesenchymal elements as seen so vividly in conditionslike bronchopulmonary dysplasia is more likely.It is to be hoped that further investigation of the

pulmonary neuroendocrine cell system in diseased hu-man lungs, studies of experimentally induced pulmo-nary injury in laboratory animals and, of course, fur-ther investigationof themechanismsunderlying thegrowthand differentiation of pulmonary tissues during normalpulmonary development will combine to provide the an-swers to these interesting and important questions.

REFERENCESAguayo, S.M., King, T.E., Waldron, J.A., Sherritt, K.M., Kane, M.A.,and Miller, Y.E. (1990) Increased pulmonary neuroendocrine cellswith bombesin-like immunoreactivity in adult patients with eosino-philic granuloma. J. Clin. Invest., 86:838–844.

Aguayo, S.M., Miller, Y.E., Waldron, J.A., Bogin, R.M., Sunday, M.E.,Staton, G.W., Beam, W.R., and King, T.E. (1992) Brief report:Idiopathic diffuse hyperplasia of pulmonary neuroendocrine cellsand airways disease. New Engl. J. Med., 327:1285–1288.

Allibone, R.O. and Gosney, J.R. (1990) Rapid changes in pulmonary

endocrine cells in acute bronchopneumonic consolidation (abstract).J. Pathol., 161:347.

Ayvazian, L.F., Schneider, B., Gewirtz, G., and Yalow, R.S. (1975)Ectopic production of big ACTH in carcinoma of the lung: Its clinicalusefulness as a biologic marker. Am. Rev. Respir. Dis., 111:279–287.

Becker, K.L., Monaghan, K.G., and Silva, O.L. (1980) Immunocyto-chemical localization of calcitonin in Kulchitsky cells of human lung.Arch. Pathol. Lab. Med., 104:196–198.

Becker, K.L., Nash, D., Silva, O.L., Snider, R.H., and Moore, C.F.(1981) Increased serum and urinary calcitonin levels in patientswith pulmonary disease. Chest, 79:211–216.

Becker, K.L., Silva, O.L., Snider, R.H., Moore, C.F., Geelhoed, G.W.,and Nash, D. (1984) The pathophysiology of pulmonary calcitonin.In: The Endocrine Lung in Health and Disease. K.L. Becker andA.F.Gazdar, eds. Saunders, Philadelphia, pp. 277–299.

Bousbaa, H., Poron, F., and Fleury-Feith, J. (1994) Changes inchromograninA-immunoreactive guinea-pig pulmonary neuroendo-crine cells after sensitization and challenge with ovalbumin. CellTissue Res., 275:195–199.

Carabba, V.H., Sorokin, S.P., and Hoyt, R.F. (1985) Development ofneuroepithelial bodies in intact and cultured lungs of fetal rats. Am.J. Anat., 173:1–27.

Cutz, E., Gillian, J.E., and Track, N.S. (1984) Pulmonary endocrinecells in the developing human lung and during neonatal adaptation.In: The Endocrine Lung in Health and Disease. K.L. Becker andA.F.Gazdar, eds. Saunders, Philadelphia, pp. 210–231.

Cutz, E., Gillan, J.E., and Bryan, A.C. (1985) Neuroendocrine cells inthe developing human lung: Morphologic and functional consider-ations. Pediatr. Pulmonol., 1 (suppl.):S21–S29.

DiAugustine, R.P., Jahnke, G.D., and Talley, F. (1984) Endocrine cellsof the guinea pig upper airways. Morphology, distribution, anddisposition after xeno-transplantation in the nude mouse. In: TheEndocrine Lung in Health and Disease. K.L. Becker and A.F.Gazdar, eds. Saunders, Philadelphia, pp. 232–248.

Dovey, M., Wisseman, C.L., Roggli, V.L., Roomans, G.M., Shelburne,J.D., and Spock, A. (1989) Ultrastructural morphology of the lung incystic fibrosis. J. Submicrosc. Cytol. Pathol., 21:521–534.

Dupont, A.G., Somers, G., Van Steirteghem, A.C., Watson, F., andVanhaelst, L. (1984) Ectopic adrenocorticotropin production: Disap-pearance after removal of inflammatory tissue. J. Clin. Endocrinol.Metab., 58:654–658.

Fukayama, M., Hayashi, Y., Shiozawa, Y., Furukawa, E., Funata, N.,and Koike, M. (1990) Human chorionic gonadotropin alpha subunitin endocrine cells of fibrotic and neoplastic lung. Lab. Invest.,62:444–451.

Galan-Galan, F., Hurtado, J., Cano, R.P., and Peralta, M.G. (1982)High plasma calcitonin concentrations in chronic bronchitis. Br.Med. J., 285:850–851.

Gewirtz, G. and Yalow, R.S. (1974) Ectopic ACTH production incarcinoma of the lung. J. Clin. Invest., 53:1022–1032.

Ghatei, M.A., Sheppard, M.D., Henzen-Logman, S., Blank, M.A.,Polak, J.M., and Bloom, S.R. (1983) Bombesin and vasoactiveintestinal polypeptide in the developing lung: Marked changes inacute respiratory distress syndrome. J. Clin. Endocrinol. Metab.,57:1226–1232.

Gillan, J.E., Pape, K.E., and Cutz, E. (1986) Association of changes inbombesin immunoreactive neuroendocrine cells in lungs of newborninfants with persistent fetal circulation and brainstem damage dueto birth asphyxia. Pediatr. Res., 20:828–833.

Gillan, J.E., Curran, C., O’Reilly, E., Cahalane, S.F., and Unwin, A.R.(1989) Abnormal patterns of pulmonary neuroendocrine cells invictims of sudden infant death syndrome. Paediatrics, 84:828–834.

Gosney, J.R. (1992) Pulmonary Endocrine Pathology: Endocrine Cellsand Endocrine Tumours of the Lung. Butterworth-Heinemann,Oxford.

Gosney, J.R. (1993) Neuroendocrine cell populations in postnatalhuman lungs: Minimal variation from childhood to old age. Anat.Rec., 236:177–180.

Gosney, J.R. (1994) The endocrine lung and its response to hypoxia.Thorax, 49:S25–S26.

Gosney, J.R., Sissons, M.C.J., and Allibone, R.O. (1988) Neuroendo-crine cell populations in normal human lungs: A quantitative study.Thorax, 43:878–882.

Gosney, J.R., Sissons, M.C.J., Allibone, R.O., and Blakey, A.F. (1989a)Pulmonary endocrine cells in chronic bronchitis and emphysema. J.Pathol., 157:127–133.

Gosney, J., Heath, D., Smith, P., Harris, P., and Yacoub, M. (1989b)Pulmonary endocrine cells in pulmonary arterial disease. Arch.Pathol. Lab. Med., 113:337–341.

Gosney, J.R., Green, A.R.T., and Taylor, W. (1990) Appropriate andinappropriate neuroendocrine products in pulmonary tumourlets.Thorax, 45:679–683.

112 J.R. GOSNEY

Gould, V.E., Linnoila, R.I., Memoli, V.A., and Warren, W.H. (1983)Neuroendocrine components of the bronchopulmonary tract: Hyper-plasias, dysplasias and neoplasms. Lab. Invest., 49:519–537.

Hatano, S. and Strasser, T., eds. (1975) Primary Pulmonary Hyperten-sion. W.H.O., Geneva.

Hernandez-Vasquez, A., Will, J.A., and Quay, W.B. (1978) A radioauto-graphic study of the neuroepithelial bodies of the lungs in fetal andneonatal rabbits. Cell Tissue Res., 186:203–207.

Hoyt, R.F., McNelly, N.A., and Sorokin, S.P. (1990) Dynamics ofneuroepithelial body (NEB) formation in developing hamster lung:Light microscopic autoradiography after 3H-thymidine labelling invivo. Anat. Rec., 227:340–350.

Hoyt, R.F., McNelly, N.A., McDowell, E.M., and Sorokin, S. (1991)Neuroepithelial bodies stimulate proliferation of airway epitheliumin fetal hamster lung. Am. J. Physiol., 260:234–240.

Ito, T., Nakatani, Y., Nagahara, N., Ogawa, T., Shibegaki, T., andKanisawa, M. (1987) Quantitative study of pulmonary endocrinecells in anencephaly. Lung, 165:297–304.

Johnson, D.E. and Georgieff, M.K. (1989) Pulmonary neuroendocrinecells. Their secretory products and their potential roles in healthand chronic lung disease in infancy.Am. Rev. Respir. Dis., 140:1807–1813.

Johnson, D.E. and Wobken, J.D. (1987) Calcitonin gene-related pep-tide immunoreactivity in airway epithelial cells of the human fetusand infant. Cell Tissue Res., 250:579–583.

Johnson, D.E., Lock, J.E., Elde, R.P., and Thompson, T.R. (1982)Pulmonary neuroendocrine cells in hyaline membrane disease andbronchopulmonary dysplasia. Pediatr. Res., 16:446–454.

Johnson, D.E., Kulik, T.J., Lock, J.E., Elde, R.P., and Thompson, T.R.(1985) Bombesin-, calcitonin-, and serotonin-immunoreactive pulmo-nary neuroendocrine cells in acute and chronic neonatal lungdisease. Pediatr. Pulmonol., 1 (suppl.):S13–S20.

Johnson, D.E., Wobken, J.D., and Landrum, B.G. (1988) Changes inbombesin, calcitonin and serotonin immunoreactive pulmonaryneuroendocrine cells in cystic fibrosis and after prolonged mechani-cal ventilation. Am. Rev. Respir. Dis., 137:123–131.

Johnson, N.F., Wagner, J.C., and Wills, H.A. (1980) Endocrine cellproliferation in the rat lung following asbestos inhalation. Lung,158:221–228.

King, K.A., Hua, J., Torday, J.S., Drazen, J.M., Graham, S.A., Shipp,M.A., and Sunday, M.E. (1993) CD10/Neutral endopeptidase 24.11regulates fetal lung growth and maturation in utero by potentiatingendogenous bombesin-like peptides. J. Clin. Invest., 91:1969–1973.

Lauweryns, J.M. and Cokelaere, M. (1973a) Hypoxia-sensitive neuro-epithelial bodies. Intrapulmonary secretory neuroreceptors, modu-lated by the CNS. Z. Zellforsch Mikroskop. Anat., 145:521–540.

Lauweryns, J.M. and Cokelaere, M. (1973b) Intrapulmonary neuro-epithelial bodies: Hypoxia sensitive neuro-(chemo-)receptors. Expe-rientia, 29:1384–1386.

Lauweryns, J.M. and Peuskens, J.C. (1972) Neuroepithelial bodies(neuroreceptor or secretory organs?) in human infant bronchialepithelium.Anat. Rec., 172:471–482.

Lauweryns, J.M., Cokelaere, M., Deleersnyder, M., and Liebens, M.(1977) Intrapulmonary neuro-epithelial bodies in newborn rabbits.Influence of hypoxia, hyperoxia, hypercapnia, nicotine, reserpine,L-Dopa and 5-HPT. Cell Tissue Res., 182:425–440.

Lauweryns, J.M., Cokelaere, M., Lerut, T., and Theunynck, P. (1978)Cross-circulation studies on the influence of hypoxia and hypoxae-mia on the neuro-epithelial bodies in young rabbits. Cell TissueRes., 193:373–386.

Lauweryns, J.M., De Bock, V., Verhofstad, A.A.J., and Steinbusch,H.W.M. (1982) Immunohistochemical localization of serotonin in intra-pulmonary neuroepithelial bodies. Cell TissueRes., 226:215–223.

Lauweryns, J.M., De Bock, V., Guelinckx, P., and Decramer, M. (1983)Effects of unilateral hypoxia on neuroepithelial bodies in rabbitlungs. J. Appl. Physiol., 55:1665–1668.

Linnoila, R.I. (1982) Effects of diethylnitrosamine on lung neuroendo-crine cells. Exp. Lung Res., 3:225–236.

Madden, B.P., Gosney, J., Coghlan, J.G., Kamalvand, K., Caslin, A.W.,Smith, P., Yacoub, M., and Heath, D. (1994) Pretransplant clinico-pathological correlation in end stage primary pulmonary hyperten-sion. Eur. Respir. J., 7:672–678.

Miller, Y.E. (1994) Pulmonary neuroendocrine cells and lung develop-ment: Dim outlines emerge. J. Clin. Invest., 91:1861.

Mulder, H., Silberbusch, J., Hackeng, W.H.L., Van der Meer, C., andden Ottolander, G.J.H. (1980) Hypercalcitoninaemia in patientswith chronic inflammatory disease. Netherlands J. Med., 23:129–131.

Perrin, D.G., McDonald, T.J., and Cutz, E. (1991) Hyperplasia ofbombesin-immunoreactive pulmonary neuroendocrine cells and neu-

roepithelial bodies in sudden infant death syndrome. Paediatr.Pathol., 11:431–447.

Polak, J., Becker, K.L., Becker, E., Cutz, E., Gail, D.B., Goniakowska-Witalinska, L., Gosney, J.R., Lauweryns, J.M., Linnoila, I., McDow-ell, E.M., Miller, Y.E., Scheuermann, D.W., Springall, D.R., Sunday,M.E., and Zaccone, G. (1993) Lung endocrine cell markers, peptidesand amines. Anat. Rec., 236:169–171.

Roncalli, M., Springall, D.R., Maggioni, M., Moradoghli-Haftvani, A.,Winter, R.J.D., Zhao, L., Coggi, G., and Polak, J.M. (1993) Earlychanges in the calcitonin gene-related peptide (CGRP) content ofpulmonary endocrine cells concomitant with vascular remodellingin the hypoxic rat. Am. J. Respir. Cell Mol. Biol., 9:467–474.

Sarikas, S.N., Hoyt, R.F., and Sorokin, S.P. (1985) Ontogeny of smallgranule APUD cells in hamster lung: A morphological study. Anat.Rec., 213:396–409.

Schwartz, K.E., Wolfsen, A.R., Forster, B., and Odell, W.D. (1979)Calcitonin in non-thyroidal cancer. J. Clin. Endocrinol. Metab.,49:438–444.

Sheard, J.D.H. and Gosney, J.R. (1996) Endocrine cells in tumour-bearing lungs. Thorax., 51:721–726.

Sheppard, M.N., Johnson, N.F., Cole, G.A., Bloom, S.R., Marangos,P.J., and Polak, J.M. (1982) Neuron specific enolase immunostain-ing. A useful tool for the microscopical detection of endocrine cellhyperplasia in adult rats exposed to asbestos. Histochemistry,74:505–513.

Smith, P., Heath, D., Yacoub, M., Madden, B., Caslin, A.W., andGosney, J.R. (1990) The ultrastructure of plexogenic pulmonaryarteriopathy. J. Pathol., 160:111–121.

Stahlman, M.T. and Gray, M.E. (1984) Ontogeny of neuroendocrinecells in human fetal lung. I. An electron microscopic study. Lab.Invest., 51:449–463.

Stahlman, M., Grey, M.E., and Kasselberg, A.G. (1985) Immunoreac-tive bombesin and calcitonin paracrine cells of human fetal andnewborn airways. Pediatr. Pulmonol., 1 (suppl.):S6–S12.

Stanislawski, E.C., Hernandez-Garcia, J., Mora-Torres, M.A., andAbrajan-Polanco, E. (1981) Lung neuroendocrine structures. Topog-raphy, morphology, composition and relation with intrinsic asthma(non-immune). Arch. Invest. Med., 12:559–577.

Sunday, M.E., Kaplan, L.M., Motoyama, E., Chin, W.W., and Spindel,E.R. (1988) Gastrin-releasing peptide (mammalian bombesin) geneexpression in health and disease. Lab. Invest., 59:5–24.

Sunday, M.E., Hua, J., Dai, H.B., Nusrat, A., and Torday, J.S. (1990)Bombesin increases fetal lung growth and maturation in utero andin organ culture. Am. J. Respir. Cell Mol. Biol., 3:199–205.

Sunday, M.E., Hua, J., Torday, J.S., Reyes, B., and Shipp, M.A. (1992)CD10/Neutral endopeptidase 24.11 in developing human fetal lung.J. Clin. Invest., 90:2517–2525.

Sunday, M.E., Hua, J., Reyes, B., Masui, H., and Torday, J.S. (1993)Anti-bombesin monoclonal antibodies modulate fetal mouse lunggrowth and maturation in utero and in organ cultures. Anat. Rec.,236:25–32.

Sunday, M.E., Willett, C.G., Patidar, K., and Graham, S.A. (1994)Modulation of oncogene and tumour suppressor gene expression in ahamster model of chronic lung injury with varying degrees ofpulmonary neuroendocrine cell hyperplasia. Lab. Invest., 70:875–888.

Tsutsumi, Y. (1989) Expression of the alpha subunit of humanchorionic gonadotropin in normal and neoplastic neuroendocrinecells. An immunohistochemical study. Acta Pathol. Jpn., 39:413–419.

Tsutsumi, Y., Osamura, R.Y., Watanabe, K., and Yanaihara, N. (1983)Immunohistochemical studies on gastrin-releasing peptide andadrenocorticotropic hormone-containing cells in the human lung.Lab. Invest., 48:623–632.

Valdes-Dapena, M. (1980) Sudden infant death syndrome. A review ofthe medical literature 1974–1979. Paediatrics, 66:597–614.

Wharton, J., Polak, J.M., Bloom, S.R., Ghjatei, M.A., Solcia, E., andBrown, M.R. (1978) Bombesin-like immunoreactivity in the lung.Nature, 273:769–770.

Whitwell, F. (1955) Tumourlets of the lung. J. Pathol. Bacteriol.,70:529–541.

Wilson, N.J.E., Gosney, J.R., and Mayall, F. (1993) Endocrine cells indiffuse pulmonary fibrosis. Thorax, 48:1252–1256.

Wolf, P., Hall, C., and Kilbourn, J.P. (1986) Demonstration of calcitoninand calmodulin by immunoperoxidase in the cystic fibrosis lung.Chest, 89:327–330.

Wolfsen,A.R. and Odell, W.D. (1979) ProACTH: Use for early detectionof lung cancer. Am. J. Med., 66:765–772.

Yiakoumakis, E., Proukakis, C., Raptis, Korres, A., Dondas, N., andSamaras, V. (1987) Calcitonin concentrations in lung cancer andnon-malignant pulmonary diseases. Oncology, 44:145–149.

113NEUROENDOCRINE CELLS IN DISEASED LUNGS