Embryonic rat adrenal glands in organ culture: effects of dexamethasone, nerve growth factor and its antibodies on pheochromoblast differentiation

Treatment of pregnant females with dexamethasone influences postnatal development of the adrenal medulla

In the light of the mutual dependence between the adrenal cortex and medulla, the aim of this work was to examine whether glucocorticoid treatment of pregnant rats affects the development of the adrenal medulla of their offspring in the postnatal period. Pregnant rats were treated with dexamethasone (Dx) in a daily dose of 0.3 mg Dx/kg b.w. during days 16-20 of gestation. The structure and function of the adrenal medulla of their 14-day-old offspring were estimated on the basis of the morphometric parameters of the gland, chromaffin cell mitotic index and adrenal gland adrenaline content. Stereological analysis was carried out at the light microscopic level, the mitotic index was determined by counting the number of metaphase arrested chromaffin cells following the administration of vincristine-sulphate, whereas adrenaline content in the adrenal gland was measured fluorimetrically. Plasma ACTH concentrations of the offspring were also determined by RIA. Long term Dx treatment of pregnant rats caused a significant decrease of the total volume of adrenal chromaffin tissue in the 14-day-old offspring as well as a reduction in the number of chromaffin cells and the average cell and nuclear volumes. The proliferative activity of the chromaffin cells was also lower than in the control offspring. These changes were accompanied by a significantly reduced adrenaline content in the adrenals. The results of this work show that glucocorticoid excess during the period of pregnancy when the fetal adrenal medulla is formed has a strong inhibitory effect on the adrenal medulla of the offspring at the age of 14 days.

Sympathoadrenal progenitors in embryonic chick sympathetic ganglia show distinct responses to glucocorticoid hormones

The sympathoadrenal cell lineage originates from the neural crest and comprises the neurons of sympathetic ganglia, adrenal and extra-adrenal chromaffin cells, and the so-called small intensely fluorescent cells. In vitro studies using mammalian immature chromaffin cells, adrenal or sympathetic ganglionic progenitors, or ganglionic small intensely fluorescent cells, have suggested that glucocorticoid hormones are essential for inhibiting neuronal differentiation of sympathoadrenal progenitors and promoting the chromaffin cell phenotype. In avian systems, however, the distinct cellular phenotypes in this lineage and the molecular cues underlying their differentiation have not been fully explored. In the chick embryo, early sympathetic ganglion anlagen are populated by granule-containing cells that morphologically resemble small intensely fluorescent cells and chromaffin cell progenitors. These cells subsequently disappear from the ganglia, by death and by transition into fully differentiated sympathetic neurons, as indicated by the appearance of cells that are ultrastructurally intermediate between granule-containing cells and fully differentiated neurons (granule-containing cells in transition). In the present study, we show that treatment of cultured sympathetic cells dissociated from embryonic day (E) 7, 9, or 11 lumbar sympathetic ganglia with the glucocorticoid hormones hydrocortisone or corticosterone has neither an inhibitory nor an inductive effect on phenotypes of granule-containing cells or granule-containing cells in transition. In cell cultures of E15 ganglia, however, glucocorticoid treatment induces a granule-containing cell resembling the granule-containing phenotype. These results suggest that the early granule-containing cells and granule-containing cells in transition in chick sympathetic ganglia are not the counterparts of glucocorticoid-responsive mammalian small intensely fluorescent or chromaffin progenitor cells, despite their morphological similarity. However, E15 sympathetic ganglia apparently contain a glucocorticoid-responsive progenitor population that can differentiate into chromaffin-like cells. These progenitors seem to require a systemic or intraganglionic developmental signal or undergo a temporal switch that renders them susceptible to glucocorticoids.

Lectin binding distinguishes between neuroendocrine and neuronal derivatives of the sympathoadrenal neural crest

Lectin cytochemistry was used to identify surface epitopes selectively expressed by chromaffin cell chemoreceptors (glomus cells) in the rat carotid body. Unexpectedly, these studies revealed that binding sites for peanut agglutinin (PNA; Arachis hypogea) were highly expressed by all neuroendocrine-derivatives of the sympathoadrenal neural crest, including glomus cells, small, intensely fluorescent cells, and adrenal chromaffin cells in situ. In contrast, principal sympathetic neurons did not express PNA receptors. PNA binding was inhibited by 2% galactose. To determine whether expression of PNA receptors was selectively induced by neuroendocrine differentiation of sympathoadrenal precursors, we compared PNA labeling of embryonic sympathoblasts in the presence of either nerve growth factor (NGF) or the synthetic glucocorticoid dexamethasone (DEX). DEX-treated cells, which expressed several neuroendocrine traits, bound PNA, whereas NGF-treated neuronal derivatives did not. In addition, to examine whether expression of existing PNA receptors was down-regulated by neuronal differentiation of chromaffin cells, we compared labeling of PC12 cells, which normally bind PNA, in the presence and absence of NGF. Although PC12 cells acquired characteristic neuronal morphologies in the presence of NGF, they did not lose PNA labeling, even after 8 days of NGF treatment. These findings indicate that neuronal and neuroendocrine derivatives of the sympathoadrenal lineage can be distinguished by differential expression of carbohydrate epitopes and suggest that PNA receptors are induced by neuroendocrine differentiation.

Histochemically demonstrable catecholamines in the sympathetic nervous system of trisomic 16 and normal fetal mice

The formaldehyde-induced fluorescence (FIF) and micro-spectrofluorometric techniques were used to study catecholamines in the sympathetic nervous system of normal and trisomy 16 fetal mice with a gestation age of 15 days, an animal model for human trisomy 21 (Down's syndrome). FIF intensity in the stellate sympathetic ganglion of trisomic embryos did not differ from that of controls, whereas in the adrenal medulla the FIF intensity was 38% less in trisomic than in control embryos. When adrenal medullary cells from embryos with a gestational age of 15 days were maintained in culture for 7-10 days, a difference in FIF intensity between groups was still evident. The rate of noradrenaline uptake in cultured adrenal medullary cells also was significantly less in trisomic than in control fetal mice. The results suggest that the development of adrenal medulla is slowed in trisomic 16 mice and that uptake of noradrenaline by trisomic adrenal medullary cells is impaired.

The sympathoadrenal lineage in avian embryos. I. Adrenal chromaffin cells lose neuronal traits during embryogenesis

Cells of the sympathoadrenal lineage, including sympathetic neurons, adrenal chromaffin cells (pheochromocytes), and small intensely fluorescent (SIF) cells, arise from the neural crest. We have used antisera against catecholamine biosynthesis enzymes in conjunction with the monoclonal antibody A2B5 and an antiserum against the 160-kDa neurofilament (NF) protein, as markers of neuronal differentiation, to characterize the ontogeny of the sympathoadrenal lineage in quail embryos. The precursors of sympathetic neurons and pheochromocytes, present in the primary sympathetic chains, express neuronal traits and tyrosine hydroxylase (TH) early in development. The precursors that enter the developing adrenal gland from the primary sympathetic chain lose neuronal traits and later express the enzyme phenylethanolamine N-methyltransferase (PNMT). No TH+ cells differentiate in cultures of early (E7) embryonic adrenal glands after all A2B5+ cells have been immunoablated. When transplanted onto the neural crest migratory pathway, cells present in older (E13) embryonic adrenal glands can give rise to NF+ cells in the sympathetic ganglia. We conclude that both sympathetic neurons and pheochromocytes in avian embryos arise from a common bipotential precursor that initially expresses neuronal traits.

Mitotic cell division in the extraadrenal chromaffin system of various species

Mitotic activity often has been reported in embryonic and fetal sympathetic neuroblasts, principal sympathoblasts, and primitive sympathetic cells in various species at different stages of development. Postnatal adrenal medullary cells also are known to undergo mitosis, but such dividing capabilities rarely have been observed in the true postnatal extraadrenal chromaffin system. Although few in number, this work nevertheless has clearly identified such cells in varying stages of the mitotic cycle in the young dog, Syrian hamster, mouse, rabbit, and rat. The dividing cells were noted in paraaortic chromaffin organs, paraganglia, and within the inferior mesenteric ganglion as well. They displayed the morphological character usually associated with their adrenal medullary catecholaminergic counterparts, including numerous dense-cored vesicles known to be the harbingers of catecholamines and various peptides. Nerve endings were not noticed upon the mitotic cells. The phenomenon of dividing extraadrenal chromaffin cells augments existing data and perhaps suggests that these cells are more endocrine than neural in type and subservient to the adrenal medulla in its classic endocrine function.

Development and plasticity of adrenal chromaffin cells: cues based on in vitro studies

Neural crest derived precursors of the sympathoadrenal cell lineage give rise to two major cell types that differ in a number of morphological, ultrastructural, and biochemical characteristics: principal sympathetic neurons and chromaffin cells of the adrenal medulla. The present article reviews experimental studies performed on cultured adrenal medullary cells and designed to unravel the nature of epigenetic signals governing the developmental choice between the endocrine chromaffin and the neuronal sympathetic phenotype. Emphasis is placed on the role of glucocorticoids in initiation, development, and maintenance of the endocrine chromaffin phenotype and apparently antagonistic influences exerted by nerve growth factor (NGF) in vitro, resulting in the acquisition of neuronal properties by differentiated chromaffin cells. Experimental data from in vitro studies are compatible with the following conclusions. Glucocorticoids represent the decisive signal for the initial induction of endocrine differentiation. Moreover, high steroid hormone concentrations, as present in the adrenal medulla, are a prerequisite for the maturation of chromaffin cells. Even in a differentiated state, the endocrine phenotype is unstable in the absence of glucocorticoids, and the cells seem to reenter the neuronal developmental pathway. Under these conditions, cellular survival and differentiation into sympathetic neurons become NGF-dependent, as in normal sympathetic development. Thus, the effects of NGF survival, neurite outgrowth, and transmitter synthesis of cultured chromaffin cells probably do not reflect the induction of a specific phenotype, but they may be interpreted as a general neurotrophic support observable with other responsive cell types.

Survival and neuritic growth of sympathoadrenal (chromaffin) precursor cells in vitro

Chromaffin precursor cells from embryonic rat adrenal glands were isolated at 16.3 and 20.3 days of gestation and purified by centrifugation on density gradients. Approximately 50% of the cells of both age groups that had attached to the culture substratum by 12 hr survived during a 4-day culture period in the absence of exogenous trophic factors. Nerve growth factor (NGF) and a C6 glioma-cell-conditioned medium (C6-CM) had no or a very moderate promoting effect on survival. The glucocorticoid dexamethasone (DEX) supported the survival of 70-80% of the cells that otherwise would have died. Spontaneous neuritic growth of the sympathoadrenal precursor cells was significantly more pronounced with cells isolated at embryonic day (E) 16.3 than at E20.3. NGF had a significantly smaller promoting effect on neurite ougrowth at E16.3 than at E20.3. C6-CM induced neurite outgrowth from 25% (E16.3) and 35% (E20.3) of the surviving cells. DEX (10(-6) M) completely abolished spontaneous neuritic growth and partially suppressed C6-CM-mediated fiber outgrowth. These data underscore the importance of glucocorticoids for the maintenance and development of an endocrine morphologic phenotype of sympathoadrenal precursors. They suggest that the cells may be initially driven by growth factors other than NGF into a neuronal direction and that they lack NGF-responsiveness and -dependence during the early stages of their development.

Role of glucocorticoids in the chromaffin-neuron developmental decision

Chromaffin cells and sympathetic neurons develop from a common neural crest-derived progenitor cell. The developmental fate of this cell differs depending upon whether it migrates to the sympathetic ganglion or to the adrenal gland primordium, suggesting that local environmental signals control its differentiation. Glucocorticoid (GC) is a good candidate for an important adrenal environmental signal. These steroids are known to regulate PNMT, an adrenal-specific enzyme. However, in vivo observations suggest that the adrenal microenvironment influences the phenotype of sympatho-adrenal progenitor cells as early as E14.5, 2 days before PNMT is first expressed by developing chromaffin cells. Using cDNA probes, we find that GC receptor mRNA can be detected in the embryonic adrenal at least one full day before the initial appearance of PNMT mRNA. This observation is compatible with the idea that the apparent early influence of the adrenal microenvironment reflects the action of GC on progenitors which have migrated into this environment. In support of this, we show that similar influences can be exerted by GC on PC12 cells, which contain GC receptor mRNA but do not express or induce PNMT mRNA. Taken together, these data suggest that other factors in addition to the presence of the GC receptor may be necessary for the developmental appearance of PNMT expression.

Survival, morphology, and catecholamine storage of chromaffin cells in serum-free culture: evidence for a survival and differentiation promoting activity in medium conditioned by purified chromaffin cells

Adult bovine and young rat chromaffin cells cultured in serum-free medium were examined for their survival and differentiation following exposure to various additives, trophic agents and conditioned media. Adrenal chromaffin cells dissociated from 8 day old rats were maintained by dexamethasone, NGF and CNTF or without any additives in an N1-supplemented medium in similar numbers as in serum-containing medium for up to 6 days. Neuritic growth elicited by NGF or CNTF was enhanced in the absence of serum. Medium conditioned by purified bovine chromaffin cells improved cell survival and caused neurite outgrowth in a dose-dependent manner. The activiti(es) was sensitive to heat and trypsin and not blocked by the addition of anti-NGF antibodies. Bovine chromaffin cell survival was reduced by 30% when cells were maintained for one week in the absence as compared to the presence of serum. Addition of insulin, the N1 supplement, dexamethasone or dbcAMP single or in combinations improved the survival to different extents. A combination of insulin (5 micrograms/ml) and dexamethasone (5 X 10(-6) M) proved to be optimal in this respect. However, these supplements failed to restore the cellular catecholamine, noradrenaline and adrenaline contents to levels seen in the presence of serum. This was also true for a chromaffin cell-conditioned medium, which improved survival without elevating the catecholamine contents. Conditioned medium, however, partly restored a more physiological adrenaline-noradrenaline-ratio.

Differential effects of nerve growth factor and ciliary neuronotrophic factor on catecholamine storage and catecholamine synthesizing enzymes of cultured rat chromaffin cells

The effects of nerve growth factor (NGF) and ciliary neuronotrophic factor (CNTF) on catecholamine content and in vitro activities of tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) were studied in adrenal chromaffin cells cultured from 8-day-old rats. Both NGF and CNTF enhanced chromaffin cell survival and partially prevented losses of adrenaline during the 4-day culture period in a dose-dependent manner. CNTF was more potent, although cellular levels of adrenaline and noradrenaline were not maintained. NGF did not add to the effect of CNTF. The effect of CNTF on catecholamine storage was not accompanied by changes in the activities of TH and PNMT. In contrast, NGF induced TH but not PNMT activity. These data indicate differences between the mechanisms by which NGF and CNTF affect adrenal chromaffin cells.

Age-dependent differences in 125I-nerve growth factor binding properties of rat adrenal chromaffin cells

Nerve growth factor (NGF) has been shown to influence survival, morphology, and transmitter phenotype of young postnatal rat chromaffin cells in vitro. Significant differences in NGF responses of chromaffin cells from newborn rats compared to 8-10-day-old ones have been reported. For this reason we studied equilibrium binding and dissociation kinetics of 125I-NGF on newborn (D1) and 10-day-old (D10) rats. Under equilibrium conditions no differences were found between the two cell types, with respect to dissociation constant (approximately 2.5 X 10(-9) M) and receptor number (10-22,000 per cell). In dissociation experiments D10 chromaffin cells exhibited two classes of NGF receptors, similar to those found in other NGF-responsive cells. From fast receptors 125I-NGF was released rapidly both at 4 degrees C and at 37 degrees C, whereas dissociation from "slow" receptors was observed only at 37 degrees C. The slow receptor class was not found on D1 cells. Instead, more than 50% of specifically bound 125I-NGF did not dissociate in the presence of excess unlabeled NGF at 37 degrees C. These age-dependent differences seem to indicate regulatory developmental changes in NGF-binding properties of rat chromaffin cells.

A bipotential neuroendocrine precursor whose choice of cell fate is determined by NGF and glucocorticoids

Adrenal medullary endocrine (chromaffin) cells and sympathetic neurons both derive from the neural crest. We have found that the embryonic adrenal medulla and sympathetic ganglia are both initially populated by precursors expressing neural-specific genes. By birth, however, the medulla consists largely of chromaffin cells. In primary culture, the medullary precursors have three developmental fates: in NGF they continue to mature into neurons and survive, whereas in glucocorticoid they either extinguish their neuronal properties and exhibit an endocrine phenotype, or else continue to develop into neurons but then die. These data suggest that, in vivo, the adrenal medulla develops through both the glucocorticoid-induced differentiation of bipotential progenitors and the degeneration of committed neuronal precursors, which have migrated into the gland.

Destruction of the preganglionic nerves by beta-bungarotoxin does not interfere with normal embryonic development of the rat adrenal medulla

Using beta-bungarotoxin (beta-BTX) as a tool to eliminate the preganglionic cholinergic nerve supply to the embryonic rat adrenal gland, we have investigated whether or not these nerves affect the differentiation of embryonic chromaffin cells (pheochromoblasts). Rat fetuses received a single injection of 1 or 2 micrograms beta-BTX or an identical volume of saline at embryonic day (E) 17 and were taken for morphological and biochemical analyses at E 21. Administration of beta-BTX caused a 15 to 20% reduction in body weight, crown-rump-length and adrenal weight. Spinal cord development was reduced and acetylcholinesterase-positive cells in ventral and lateral columns were virtually absent in toxin-treated animals. In adrenal glands, a decrease of choline acetyltransferase activity to 13% of control levels and a concomitant decrease of ultrastructurally identifiable nerve fibers and axon terminals revealed that application of 2 micrograms beta-BTX effectively reduced the neuronal input to E 21 adrenal glands. Values for total adrenal catecholamines, relative amounts of adrenaline and noradrenaline, tyrosine hydroxylase and phenylethanolamine N-methyltransferase activities were unaltered. All ultrastructural features of pheochromoblasts (except the lack of synapse-like axon terminals) were inconspicuous. Corticosterone levels in adrenals and plasma were identical to controls. These data strongly suggest that normal embryonic development of adrenal chromaffin cells does not require an intact nerve supply.

Effects of pre- and postnatal administration of antibodies to nerve growth factor on the morphological and biochemical development of the rat adrenal medulla: a reinvestigation

Whether or not adrenal medullary (chromaffin) cells which respond to nerve growth factor (NGF) both in vitro and in vivo require NGF for their normal development is controversial. Systemic deprivation of endogenous NGF by injection of anti-NGF antibodies into rat fetuses or by transfer of anti-NGF to the offspring of autoimmunized mothers has provided conflicting results. We have reinvestigated the effects of a specific antiserum to NGF on the morphology, catecholamine (CA) and neuropeptide (Met-enkephalin, Met-ENK; substance P, SP) content, and choline acetyltransferase (ChAT) activity of the rat adrenal medulla. Fetuses were injected with anti-NGF antibodies on day 17 of gestation and postnatally at daily intervals for 7 days. The histological appearance of adrenal medullae of anti-NGF injected animals was not altered as compared to controls. Ultrastructurally, no degenerative changes or developmental retardation of chromaffin cells could be detected. However, numbers of chromaffin granules per micron 2 of cytoplasmic area were greater and the mean diameters of the cores of adrenaline storage granules were smaller in antibody-treated than in control animals. CA and SP content, ratios of adrenaline to noradrenaline and ChAT activities were identical in anti-NGF-treated and control animals. Anti-NGF antibodies caused a reduction of adrenal Met-ENK by 40% as compared to controls. Superior cervical ganglia from the same animals were used to document immunosympathectomy induced by the antiserum. They displayed the well-established structural alterations and a marked reduction of the CA content. We conclude that administration of anti-NGF antibodies to embryonic and early postnatal rats induces only subtle changes in the ultramorphology of chromaffin cells without altering the development of normal CA levels. The small, yet significant effects of anti-NGF antibodies on adrenal Met-ENK, however, may suggest a role for endogenous NGF in the regulation of opioid peptide metabolism in developing chromaffin cells.

A quantitative electron microscopic study of the effect of glucocorticoids in vivo on the early postnatal differentiation of paraneuronal cells in the carotid body and the adrenal medulla of the rat

The postnatal differentiation of carotid body chief cells and endocrine adrenal medullary cells was comparatively examined during ontogenesis and in rats which were treated with dexamethasone for 7 days after birth. Ultrastructure and innervation of carotid body chief cells are mature in neonates according to the functional requirements of chemoreception. By the end of the first postnatal week, only an increase in number of dense core vesicles can be noticed, the concentration of which then will reach the adult level. Under the effect of dexamethasone most of the heterochromatin is transformed into finely dispersed euchromatin within the nuclei of carotid body chief cells. In the cytoplasm, the Golgi apparatus becomes larger and the granular endoplasmic reticulum hypertrophic. The number of catecholamines storing dense core vesicles increases considerably. The innervation density remains constant. In contrast to the carotid body chief cells, the adrenal medullary cells have not reached their definitive maturity at the time of birth. Besides phenotypes of adrenaline-cells, noradrenaline-cells and small granules containing cells, pheochromoblasts and intermediary cells can be seen as well. Their cytoplasm is sparse, the concentration of dense core vesicles and the innervation density very low. After 8 days of postnatal ontogenesis, pheochromoblasts and intermediary cells are no longer present in the adrenal medulla. In adrenaline-cells and noradrenaline-cells, important processes of growth can be noticed, the cytoplasm has grown in extent, the number of dense core vesicles doubled and the innervation density of single cells triplicated. Only the few small granules containing cells remain small. Under the effect of dexamethasone also in the nuclei of chromaffin cells a transformation of heterochromatin into euchromatin occurs. The increase in number of dense core vesicles is relatively lower than in carotid body chief cells. The significant growth of innervation density during the first postnatal week was inhibited. Our observations suggest that dexamethasone stimulates the synthesis of catecholamines in adrenal medullary cells of newborn rats less pronouncedly than in carotid body chief cells. This could be attributed to the inhibited formation of synapses of growing chromaffin cells and to the in vivo active endocrine counter-regulation.

Phenotypical changes of embryonic chick adrenal medullary cells in vitro induced by nerve growth factor and ciliary neuronotrophic factor

This study investigates the survival properties and changes in the morphological phenotype of adrenal medullary (chromaffin and neuronal) cells cultured from embryonic chicks at different developmental ages (embryonic days E8 to E16) in response to nerve growth factor (NGF) and ciliary neuronotrophic factor (CNTF). The 4-day survival of medullary cells from all embryonic ages except E8 was about 80% of the seeded cells and was only slightly enhanced by the addition of saturating doses of CNTF (10 ng/ml). With no factors, after 4 days 10-30% of the surviving medullary cells extended neurites. NGF (100 ng/ml) and, even more, CNTF (10 ng/ml) and their combination substantially increased the proportions of neurite-bearing cells (up to 70%). The effect of the factors were maximal at E10 and E12 and declined at older developmental ages. Neurite growth was virtually unaffected by NGF and CNTF at E8. These results show that in vitro survival and neurite growth of chick adrenal medullary cells in response to trophic factors is developmentally regulated.

Nerve growth factor and dexamethasone specify the catecholaminergic phenotype of cultured rat chromaffin cells: dependence on developmental stage

Antibodies to epinephrine (E) and bovine phenylethanolamine N-methyltransferase (PNMT) have been used to monitor the regulation of the E- and PNMT-immunoreactive chromaffin cell phenotypes by dexamethasone (DEX) and nerve growth factor (NGF). The cells were isolated from 1-, 10- and 30-day-old (D1, D10 and D30) rat adrenal glands and grown for 4 days on a polyornithine substratum. DEX (10(-5)M) supported the survival of 90% of the cells from all postnatal ages studied. In contrast, only 45% (D1), 33% (D10) and 60% (D30) of the chromaffin cells had survived after 4 days in control cultures or when treated with NGF (100 ng/ml). Throughout this study numbers of E-immunoreactive cells were approximately 10% larger than those of cells stained by anti-PNMT antibodies irrespective of the treatments applied. 55% of the cells isolated at D1 and 79% of the cells at D10 were stained by anti-E antibodies. The proportion of E-positive cells was constant in D1 cultures carried for 4 days, while E-immunoreactive cells dropped to 63% in cultures from D10. At D1 and D10 DEX and NGF had opposite effects on the portions of E-positive cells, DEX increasing and NGF decreasing their relative numbers, 66% of the chromaffin cells isolated at D30 displayed E-specific immunoreactivity. DEX caused a significant increase (to 74%), while both NGF-treated and control cultures exhibited a decrease in the relative numbers of E-immunoreactive cells.(ABSTRACT TRUNCATED AT 250 WORDS)