A clinical approach to brown adipose tissue in the para-aortic area of the human thorax.

BACKGROUND: Human thoracic brown adipose tissue (BAT), composed of several subdivisions, is a well-known target organ of many clinical studies; however, the functional contribution of each part of human thoracic BAT remains unknown. The present study analyzed the significance of each part of human thoracic BAT in the association between regional distribution, cellularity, and factors involved in the functional regulation of thoracic BAT. METHODS: We analyzed 1550 healthy adults who underwent medical check-ups by positron-emission tomography and computed tomography (PET-CT) imaging, 8 cadavers, and 78 autopsy cases in an observational study. We first characterized the difference between the mediastinum and the supraclavicular areas using counts of BAT detection and conditions based on PET-CT outcomes. The measurable important area was then subjected to systematic anatomical and immunohistochemical analyses using anti-uncoupling protein 1 (UCP1) antibody to characterize the cellularity in association with age and sex. RESULTS: In PET-CT scanning, the main site of thoracic BAT was the mediastinum rather than the supraclavicular area (P < 0.05). Systemic macroanatomy revealed that the thumb-sized BAT in the posterior mediastinal descending para-aortic area (paBAT) had feeding vessels from the posterior intercostal arteries and veins and sympathetic/parasympathetic innervation from trunks of the sympathetic and vagus nerves, respectively. Immunohistochemical analysis indicated that the paBAT exhibited immunoreactivity for tyrosine hydroxylase and vesicular acetylcholine transporter located in the pericellular nervous fibers and intracellular UCP1. The brown adipose cells of paBAT showed age-dependent decreases in UCP1 expression (P < 0.05), accompanied by a significant increase in vacuole formation, indicating fat accumulation (P < 0.05), from 10 to 37 years of age (P < 0.01). CONCLUSIONS: paBAT may be one of the essential sites for clinical application in BAT study because of its visible anatomy with feeding vessels and sympathetic/parasympathetic innervation functionally affected by outer condition and senescence.

Sympathoadrenal neural crest cells: the known, unknown and forgotten?

Neural crest cells (NCCs) are highly migratory progenitor cells that give rise to a vast array of differentiated cell types. One of their key derivatives is the autonomic nervous system (ANS) that is comprised in part from chromaffin cells of the adrenal medulla and organ of Zuckerkandl, the sympathetic chain and additional prevertebral ganglia such as the celiac ganglia, suprarenal ganglia and mesenteric ganglia. In this review we discuss recent advances toward our understanding of how the NCC precursors of the ANS migrate to their target regions, how they are instructed to differentiate into the correct cell types, and the morphogenetic signals controlling their development. Many of these processes remain enigmatic to developmental biologists worldwide. Taking advantage of lineage tracing mouse models one of our own aims is to address the morphogenetic events underpinning the formation of the ANS and to identify the molecular mechanisms that help to segregate a mixed population of NCCs into pathways specific for the sympathetic ganglia, sensory ganglia or adrenal medulla.

Cell loss and autophagy in the extra-adrenal chromaffin organ of Zuckerkandl are regulated by glucocorticoid signalling.

Neuroendocrine chromaffin cells exist in both intra- and extra-adrenal locations; the organ of Zuckerkandl (OZ) constitutes the largest accumulation of extra-adrenal chromaffin tissue in mammals. The OZ disappears postnatally by modes that are still enigmatic but can be maintained by treatment with glucocorticoids (GC). Whether the response to GC reflects a pharmacological or a physiological role of GC has not been clarified. Using mice with a conditional deletion of the GC-receptor (GR) gene restricted to cells expressing the dopamine ß-hydroxylase (DBH) gene [GR(fl/fl) ; DBHCre abbreviated (GR(DBHCre) )], we now present the first evidence for a physiological role of GC signalling in the postnatal maintenance of the OZ: postnatal losses of OZ chromaffin cells in GR(DBHCre) mice are doubled compared to wild-type littermates. We find that postnatal cell loss in the OZ starts at birth and is accompanied by autophagy. Electron microscopy reveals autophagic vacuoles and autophagolysosomes in chromaffin cells. Autophagy in OZ extra-adrenal chromaffin cells is confirmed by showing accumulation of p62 protein, which occurs, when autophagy is blocked by deleting the Atg5 gene (Atg5(DBHCre) mice). Cathepsin-D, a lysosomal marker, is expressed in cells that surround chromaffin cells and are positive for the macrophage marker BM8. Macrophages are relatively more abundant in mice lacking the GR, indicating more robust elimination of degenerating chromaffin cells in GR(DBHCre) mice than in wild-type littermates. In summary, our results indicate that extra-adrenal chromaffin cells in the OZ show signs of autophagy, which accompany their postnatal numerical decline, a process that is controlled by GR signalling.

Grafts of extra-adrenal chromaffin cells as aggregates show better survival rate and regenerative effects on parkinsonian rats than dispersed cell grafts.

The objective was to discern the neuroregenerative effect of grafts of extra-adrenal cells of the Zuckerkandl's paraganglion (ZP) in the nigrostriatal circuit, by using the retrograde model of parkinsonism in rats. The antiparkinsonian efficacy of two types of grafting procedures was studied (cell aggregates vs. dispersed cells), and GDNF and TGFbeta(1) (dopaminotrophic factors) as well as dopamine presence in extra-adrenal tissue was analyzed. Extra-adrenal chromaffin cells are noradrenergics, tissue dopamine is low, and they express both GDNF and TGFbeta(1). Grafts of cell aggregates, not of dispersed cells, exerted a trophic regeneration of the host striatum, leading to amelioration of motor deficits. Sprouting of spared dopaminergic fibers within the striatum, reduction of dopamine axon degeneration, and/or enhanced phenotypic expression of TH would explain striatal regeneration. Grafted cells as aggregates showed a better survival rate than dispersed cells, and they express higher levels of GDNF. Higher survivability and GDNF content together with the neurorestorative and dopaminotrophic action of both GDNF and TGFbeta(1) could account for striatal recovery and functional amelioration after grafting ZP cell aggregates. Finally, nigral degeneration and partial degeneration of ventral tegmental area were not precluded after transplantation, indicating that the trophic effect of grafts was local within the host striatum.

Functional regeneration in a rat Parkinson's model after intrastriatal grafts of glial cell line-derived neurotrophic factor and transforming growth factor beta1-expressing extra-adrenal chromaffin cells of the Zuckerkandl's organ.

Intrabrain transplantation of chromaffin cell aggregates of the Zuckerkandl's organ, an extra-adrenal paraganglion that has never been tested for antiparkinsonian treatment, induced gradual improvement of functional deficits in parkinsonian rats. These beneficial effects were related to long survival of grafted cells, striatal reinnervation, and enhancement of dopamine levels in grafted striatum. Grafted cells were not dopaminergics, but they expressed glial cell line-derived neurotrophic factor (GDNF) and transforming growth factor-beta(1). These factors were detected in the host striatal tissue, indicating that chromaffin cells secreted them after grafting. Because glial cell line-derived neurotrophic factor possesses neurorestorative properties over dopaminergic neurons, and transforming growth factor-beta(1) is a cofactor that potentiates the neurotrophic actions of GDNF, functional regeneration was likely caused by the chronic trophic action of neurotrophic factors delivered by long-surviving grafted cells. This work should stimulate research on the clinical applicability of transplants of the Zuckerkandl's organ in Parkinson's disease.

An electron microscopic study of cells with steroid-secreting morphology in the paraaortic lymph node of the hamster.

Clustered cells with steroid-secreting morphology (SH), located within the paraaortic lymph node (PLN) capsules of normal and pregnant female golden hamsters, were examined by light and electron microscopy. Hydroxysteroid dehydrogenase (HD) activity of the SH cell cluster also was examined by histochemical techniques. The cluster was composed of mostly packed SH cells and surrounding mesenchymal cells. Individual SH cells possessed prominent smooth endoplasmic reticulum, well-developed Golgi complexes, some lipid droplets, and numerous mitochondria containing tubulovesicular cristae common to mammalian SH cells. Intermediate-type junctions were often observed between SH cells. The same SH cells were rarely detected in the subcapsular sinus and in the cortical parenchyma of the PLN. Early oophorectomy of the hamster resulted in cytoplasmic degeneration of the SH cell at day 5 after the operation. On the other hand, normal adult male hamsters possessed similar PLNs, but no SH cells were recognized in the nodes. The present histochemical preparation of normal female PLNs revealed moderate-to-strong HD activity, probably associated with SH cell clusters, in the limited regions of the capsules. Based on the present ultrastructural and histochemical findings, it is proposed that the SH cell cluster consists of steroid hormone producing cells.

The effect of hydrocortisone on the para-aortic body of the newborn mouse: an in vivo fraction of labelled mitoses study.

Information about the cell cycle of the mouse para-aortic body within the first 24 hours of postnatal life was derived from a fraction of labelled mitoses study. The total cell cycle time was 8 1/2 hours, being made up as follows: S phase-2 hours; G2 phase-1 hour; M phase-3 1/2 hours (by analysis of the results, not by assumption) and G1 phase-2 hours (by subtraction). Problems are discussed regarding the length of G2 and M phases and the consequences for G1. After hydrocortisone administration (40 mg/kg/day) to female mice for the last seven days of pregnancy, the pattern in newborn mice was disrupted. Values for G2 and M were similar to those of the untreated group, but no values were obtainable for the other phases of the cell cycle or for the total cell cycle time. These results after hydrocortisone treatment could be explained by the superimposition of the cell cycles of two or more different groups of cells. They are discussed with regard to the life span of the para-aortic body, and their implications are considered in the light of previously reported glucocorticoid-induced transformations of small granule cells from cervical sympathetic ganglia into catecholamine-storing chromaffin cells. The established hyperplastic effect of hydrocortisone on the para-aortic body is therefore not the result simply of an acceleration of the cell cycle, but it may involve the incorporation into the proliferative compartment of cells previously either moribund or nonproliferating.

The effect of in vivo hydrocortisone administration on the labelling index and size of chromaffin tissue in the postnatal and adult mouse.

Hydrocortisone administration in vivo to neonatal mice for seven days led to a significant increase in both the size and the labelling index of extra-adrenal chromaffin tissue (as represented by the para-aortic body) of 8 days old mice. In untreated animals at this age, the para-aortic body was in most cases too small to obtain a valid labelling index. In the para-aortic bodies of 14 days old, 21 days old and adult mice, the extra-adrenal chromaffin tissue was too dispersed to obtain values for either volumetric analysis or labelling indices, and hydrocortisone was without significant effect in promoting a hyperplastic response. In the postnatal adrenal medulla at all ages studied, hydrocortisone had no effect on the medullary size or on the labelling indices of either adrenaline- or noradrenaline-storing cells, although it led to a marked diminution of adrenocortical volume. The relative proportion of adrenaline-storing cells increased between the values for 8 days old animals and those for adults; this was unaffected by hydrocortisone. The cortico-medullary ratio remained unchanged from the eighth postnatal day onwards. The results are discussed and related to those of other workers. It is suggested that factors as yet unknown might modulate the response to corticosteroids of developing intra- and extra-adrenal chromaffin tissue.

The effect of in vivo hydrocortisone administration on the labelling index and size of the intra- and extra-adrenal chromaffin tissue of the fetal and perinatal mouse.

Administration of hydrocortisone in vivo to pregnant mice between the eighth and sixteenth days of gestation leads to highly significant increases in both the volume and the labelling index of extra-adrenal chromaffin tissue (as represented by the para-aortic body) of 16 days fetal mice. The labelling index of intra-adrenal chromaffin cells increases slightly after hydrocortisone administration, but the volume of the adrenal chromaffin tissue was not assessed since the groups of chromaffin cells had not in all cases aggregated to form a distinct medulla. Hydrocortisone administration to mice for the last week of gestation also leads to a highly significant increase in the size and the labelling index of the perinatal para-aortic body. Although an increase in the labelling index of perinatal intra-adrenal chromaffin cells is brought about, this is much less marked than that of the extra-adrenal tissue and neither is it reflected by any increase in the volume of the now discernible adrenal medulla. These increases in size and labelling index of the para-aortic body constitute a hyperplastic response rather than a hypertrophic response. Various possible mechanisms and implications are discussed in the light of the development of chromaffin tissue and the effects of the cortex and its secretions on the medulla. Associated effects of hydrocortisone noted in this work are the resultant marked diminution of adrenocortical volume in the perinatal gland, and a slight fall in the labelling index of perinatal intra-adrenal haemopoietic cells.

A special type of small granule-containing cell in the abdominal para aortic region of the frog.

Light and electron microscopic studies have been made of a special type of small granule-containing cell (termed Type IV cell) in the frog abdominal para aortic region. These cells contain numerous dense granular vesicles (100--150 nm in diameter) and are considerably smaller (10--20 mu) than neighbouring nerve cells, although they have many features in common with them. They do not resemble chromaffin cells as do Types I, II and III cells. The cell bodies are completely ensheathed by satellite cells and are isolated from neighbouring cells of the same type. Type IV cells have long processes which usually become incorporated in bundles containing 2--20 processes, including some cholinergic nerve fibres, and are loosely enveloped by perineurium. The termination of the processes of Type IV cells do not appear to form efferent synapses on nerve cells at least within the para aortic region or in paravertebral sympathetic ganglia. A close topographical relationship is not found between these processes and blood vessels. It is suggested that the small Type IV granule-containing cells in the frog abdominal para aortic region are not interneurons or neurosecretory cells, but are a special type of sympathetic nerve cell.

Distribution and morphology of amphibian extra-adrenal chromaffin tissue.

1. The distribution and morphology of chromaffin cells in the para-aortic region and in the ganglia of the paravertebral sympathetic chain was studied with fluorescence histochemistry and electron microscopy. 2. Four types of chromaffin cell were distinguished largely on the basis of their vesicular content: Type I cells contain large, electron-dense vesicles (600-7000 A) and are comparable to noradrenaline-containing cells in the adrenal gland, Type II cells contain large, vesicles (600-7000 A) that are filled with a less electron-dense material than that in Type I cells and are comparable to adrenaline-containing cells in the adrenal gland, Type III cells contain smaller vesicles (1000-3000 A) that are incompletely filled with an electron-dense material and may represent cells that have been depleted of their catecholamines by stimulation, Type IV cells are clearly different from the other three cell types with respect to the size and appearance of the vesicles (1000-1500 A), nuclei and rough endoplasmic reticulum and may represent immature sympathetic neurons. 3. Nerve profiles, identified as cholinergic, were found in close apposition with all four cell types. No examples of a close association between processes of chromaffin cells and sympathetic neurons were found.