Multipotent Glia-Like Stem Cells Mediate Stress Adaptation

SOX2+ sustentacular cells are stem cells of the postnatal adrenal medulla

Renewal of the catecholamine-secreting chromaffin cell population of the adrenal medulla is necessary for physiological homeostasis throughout life. Definitive evidence for the presence or absence of an adrenomedullary stem cell has been enigmatic. In this work, we demonstrate that a subset of sustentacular cells endowed with a support role, are in fact adrenomedullary stem cells. Through genetic tracing and comprehensive transcriptomic data of the mouse adrenal medulla, we show that cells expressing Sox2/SOX2 specialise as a unique postnatal population from embryonic Schwann Cell Precursors and are also present in the normal adult human adrenal medulla. Postnatal SOX2+ cells give rise to chromaffin cells of both the adrenaline and noradrenaline lineages in vivo and in vitro. We reveal that SOX2+ stem cells have a second, paracrine role in maintaining adrenal chromaffin cell homeostasis, where they promote proliferation through paracrine secretion of WNT6. This work identifies SOX2+ cells as a true stem cell for catecholamine-secreting chromaffin cells.

Role of Adrenal Progenitor Cells in the Structural Response of Adrenal Gland to Various forms of Acute Stress and Subsequent Recovery in Adult Male Albino Rats

Background

Stress is a response to stressogenic stimuli that interferes with an organism's homeostasis. The adrenal gland is crucial in the body's reaction to stress.

Objective

This study compared the effects of immobility and cold as acute stressors and the subsequent recovery on the histological changes of the adrenal gland and the suspected role of the adrenal progenitor cells.

Materials and Methods

Thirty-five adult male albino rats were divided equally into five groups. Group I: Control group, Group II: Rats subjected to the acute cold stress procedure, Group III: Rats subjected to the acute immobilization stress procedure, Group IV: The combined stress group, and Group V: Similar to the combined stress group and recovered for 6 days then sacrificed 1 day later. Serum cortisol level was determined, and the adrenal glands were processed for histological and immunohistochemical studies.

Results

Serum cortisol concentration was higher in the acute-stress groups and decreased in the recovery group. The adrenal cortex had enlarged, vacuolated cells with pyknotic nuclei, sinusoidal dilatation, and congestion. Chromaffin cells were crowded, enlarged, and vacuolated. There was strong immunohistochemical reactivity for heat shock protein-70 and caspase-3. In addition, the combined group showed a significant increase in the optical density of chromogranin-A in the medullary cells as well as CD44+ve cells. These findings were decreased in the recovery group.

Conclusions

The combined stress has more deleterious adrenal cortical changes than immobilization and cold stress alone. The progenitor and chromaffin cells apparently had an important regenerative role in recovery from both types of stress.

Recent progress in molecular classification of phaeochromocytoma and paraganglioma

Phaeochromocytomas (PC) and paragangliomas (PG) are neural crest cancers with high heritability. Recent advances in molecular profiling, including multi-omics and single cell genomics has identified up to seven distinct molecular subtypes. These subtypes are defined by mutations involving hypoxia-inducible factors (HIFs), Krebs cycle, kinase and WNT signalling, but are also defined by chromaffin differentiation states. PCPG have a dominant proangiogenic microenvironment linked to HIF pathway activity and are generally considered "immune cold" tumours with a high number of macrophages. PCPG subtypes can indicate increased metastatic risk but secondary mutations in telomere maintenance genes TERT or ATRX are required to drive the metastatic phenotype. Molecular profiling can identify molecular therapeutic (e.g. RET and EPAS1) and radiopharmaceutical targets while also helping to support variant pathogenicity and familial risk. Molecular profiling and subtyping of PCPG therefore confers the possibility of nuanced prognostication and individual treatment stratification but this still requires large-scale prospective validation.

Postnatal Exposure to the Endocrine Disruptor Dichlorodiphenyltrichloroethane Affects Adrenomedullary Chromaffin Cell Physiology and Alters the Balance of Mechanisms Underlying Cell Renewal

Dichlorodiphenyltrichloroethane (DDT) is a wide-spread systemic pollutant with endocrine disrupting properties. Prenatal exposure to low doses of DDT has been shown to affect adrenal medulla growth and function. The role of postnatal exposure to DDT in developmental disorders remains unclear. The aim of the present investigation is to assess growth parameters and the expression of factors mediating the function and renewal of chromaffin cells in the adult adrenal medulla of male Wistar rats exposed to the endocrine disruptor o,p'-DDT since birth until sexual maturation. The DDT-exposed rats exhibited normal growth of the adrenal medulla but significantly decreased tyrosine hydroxylase production by chromaffin cells during postnatal period. Unlike the control, the exposed rats showed enhanced proliferation and reduced expression of nuclear β-catenin, transcription factor Oct4, and ligand of Sonic hedgehog after termination of the adrenal growth period. No expression of pluripotency marker Sox2 and absence of Ascl 1-positive progenitors were found in the adrenal medulla during postnatal ontogeny of the exposed and the control rats. The present findings indicate that an increase in proliferative activity and inhibition of the formation of reserve for chromaffin cell renewal, two main mechanisms for cell maintenance in adrenal medulla, in the adult DDT-exposed rats may reflect a compensatory reaction aimed at the restoration of catecholamine production levels. The increased proliferation of chromaffin cells in adults suggests excessive growth of the adrenal medulla. Thus, postnatal exposure to DDT alters cell physiology and increases the risk of functional insufficiency and hyperplasia of the adrenal medulla.

BET and CDK Inhibition Reveal Differences in the Proliferation Control of Sympathetic Ganglion Neuroblasts and Adrenal Chromaffin Cells

Neuroblastoma arising from the adrenal differ from ganglionic neuroblastoma both genetically and clinically, with adrenal tumors being associated with a more severe prognosis. The different tumor properties may be linked to specific tumor founder cells in adrenal and sympathetic ganglia. To address this question, we first set up cultures of mouse sympathetic neuroblasts and adrenal chromaffin cells. These cultures were then treated with various proliferation inhibitors to identify lineage-specific responses. We show that neuroblast and chromaffin cell proliferation was affected by WNT, ALK, IGF1, and PRC2/EZH2 signaling inhibitors to a similar extent. However, differential effects were observed in response to bromodomain and extraterminal (BET) protein inhibitors (JQ1, GSK1324726A) and to the CDK-7 inhibitor THZ1, with BET inhibitors preferentially affecting chromaffin cells, and THZ1 preferentially affecting neuroblasts. The differential dependence of chromaffin cells and neuroblasts on BET and CDK signaling may indicate different mechanisms during tumor initiation in sympathetic ganglia and adrenal.

Isolation and in vitro cultivation of adrenal cells from mice

The adrenal gland consists of two tissues, cortex and medulla, united under one capsule. Adrenal stem/progenitor cells play a key role in development and homeostasis. Here, we describe a protocol for generating primary cultures of adrenal cells from mice. We describe techniques for separating the cortex and medulla, generating spheroid cultures containing stem- and progenitor cells, and for the differentiation into steroidogenic and chromaffin cells, respectively. This protocol enables analysis of various treatments before, during, or after differentiation.

For complete details on the use and execution of this protocol, please refer to Rubin de Celis et al. (2015), Steenblock et al. (2018), and Werdermann et al. (2021).

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Protocol for establishment of adrenal spheroids from mice

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Adrenal spheroids contain cells possessing stem cell characteristics

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Differentiation into steroid-producing cells or into chromaffin cells

Adrenal medulla development and medullary-cortical interactions

The mammalian adrenal gland is composed of two distinct tissue types in a bidirectional connection, the catecholamine-producing medulla derived from the neural crest and the mesoderm-derived cortex producing steroids. The medulla mainly consists of chromaffin cells derived from multipotent nerve-associated descendants of Schwann cell precursors. Already during adrenal organogenesis, close interactions between cortex and medulla are necessary for proper differentiation and morphogenesis of the gland. Moreover, communication between the cortex and the medulla ensures a regular function of the adult adrenal. In tumor development, interfaces between the two parts are also common. Here, we summarize the development of the mammalian adrenal medulla and the current understanding of the cortical-medullary interactions under development and in health and disease.

Single-cell transcriptomes reveal characteristic features of cell types within the human adrenal microenvironment

Various cells within the adrenal microenvironment are important in maintaining the body homeostasis. However, our understanding of adrenal disease pathogenesis is limited by an incomplete molecular characterization of the cell types responsible for the organ's multiple homeostatic functions. We report a cellular landscape of the human adrenal gland using single-cell RNA sequencing. We reveal characteristic features of cell types within the human adrenal microenvironment and found immune activation of nonimmune cells in the adrenal endothelial cells. We also reveal that abundant immune cells occupied a lot of space in adrenal gland. Additionally, Sex-related diversity in the adrenocortical cells and different gene expression profiles between the left and right adrenal gland are also observed at single-cell resolution. Together, at single-cell resolution, the transcriptomic map presents a comprehensive view of the human adrenal gland, which serves as a fundamental baseline description of this organ and paves a way for the further studies of adrenal diseases.

Stem cells, evolutionary aspects and pathology of the adrenal medulla: A new developmental paradigm

The mammalian adrenal gland is composed of two main components; the catecholaminergic neural crest-derived medulla, found in the center of the gland, and the mesoderm-derived cortex producing steroidogenic hormones. The medulla is composed of neuroendocrine chromaffin cells with oxygen-sensing properties and is dependent on tissue interactions with the overlying cortex, both during development and in adulthood. Other relevant organs include the Zuckerkandl organ containing extra-adrenal chromaffin cells, and carotid oxygen-sensing bodies containing glomus cells. Chromaffin and glomus cells reveal a number of important similarities and are derived from the multipotent nerve-associated descendants of the neural crest, or Schwann cell precursors. Abnormalities in complex developmental processes during differentiation of nerve-associated and other progenitors into chromaffin and oxygen-sensing populations may result in different subtypes of paraganglioma, neuroblastoma and pheochromocytoma. Here, we summarize recent findings explaining the development of chromaffin and oxygen-sensing cells, as well as the potential mechanisms driving neuroendocrine tumor initiation.

Insulin and obesity transform hypothalamic-pituitary-adrenal axis stemness and function in a hyperactive state

Objective

Metabolic diseases are an increasing problem in society with the brain-metabolic axis as a master regulator of the human body for sustaining homeostasis under metabolic stress. However, metabolic inflammation and disease will trigger sustained activation of the hypothalamic-pituitary-adrenal axis. In this study, we investigated the role of metabolic stress on progenitor cells in the hypothalamic-pituitary-adrenal axis.

Methods

In vitro, we applied insulin and leptin to murine progenitor cells isolated from the pituitary and adrenal cortex and examined the role of these hormones on proliferation and differentiation. In vivo, we investigated two different mouse models of metabolic disease, obesity in leptin-deficient ob/ob mice and obesity achieved via feeding with a high-fat diet.

Results

Insulin was shown to lead to enhanced proliferation and differentiation of both pituitary and adrenocortical progenitors. No alterations in the progenitors were noted in our chronic metabolic stress models. However, hyperactivation of the hypothalamic-pituitary-adrenal axis was observed and the expression of the appetite-regulating genes Npy and Agrp changed in both the hypothalamus and adrenal.

Conclusions

It is well-known that chronic stress and stress hormones such as glucocorticoids can induce metabolic changes including obesity and diabetes. In this article, we show for the first time that this might be based on an early sensitization of stem cells of the hypothalamic-pituitary-adrenal axis. Thus, pituitary and adrenal progenitor cells exposed to high levels of insulin are metabolically primed to a hyper-functional state leading to enhanced hormone production. Likewise, obese animals exhibit a hyperactive hypothalamic-pituitary-adrenal axis leading to adrenal hyperplasia. This might explain how stress in early life can increase the risk for developing metabolic syndrome in adulthood.

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Insulin enhances proliferation and differentiation of adrenocortical and pituitary progenitors.

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Obesity leads to hyperactivation and priming of the HPA axis.

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Obesity leads to overexpression of appetite-regulating genes in the hypothalamus.

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Obesity leads to a decrease in the expression of appetite-regulating genes in the adrenal gland.

Are Nestin-positive cells responsive to stress?

In a number of adult tissues, Nestin-positive stem cells/progenitors have been identified and shown to be involved in maintenance and remodeling. Various studies have shown that under stressful conditions, quiescent Nestin-positive progenitor cells are activated. Thereby, they migrate to their target location and differentiate into mature cells. In the current paper, we discuss if Nestin-positive progenitors in the hippocampus and adrenal gland belong to unique cell populations that are responsive to stress. Furthermore, we speculate about the mechanism behind their activation and the clinical importance of this stress-response.

Development of the Autonomic Nervous System: Clinical Implications

Investigations of the cellular and molecular mechanisms that mediate the development of the autonomic nervous system have identified critical genes and signaling pathways that, when disrupted, cause disorders of the autonomic nervous system. This review summarizes our current understanding of how the autonomic nervous system emerges from the organized spatial and temporal patterning of precursor cell migration, proliferation, communication, and differentiation, and discusses potential clinical implications for developmental disorders of the autonomic nervous system, including familial dysautonomia, Hirschsprung disease, Rett syndrome, and congenital central hypoventilation syndrome.

Cancer Stem Cells in Pheochromocytoma and Paraganglioma

Pheochromocytoma (PCC) and paraganglioma (PGL) are rare neuroendocrine tumors associated with high cardiovascular morbidity and variable risk of malignancy. The current therapy of choice is surgical resection. Nevertheless, PCCs/PGLs are associated with a lifelong risk of tumor persistence or recurrence. A high rate of germline or somatic mutations in numerous genes has been found in these tumors. For some, the tumorigenic processes are initiated during embryogenesis. Such tumors carry gene mutations leading to pseudohypoxic phenotypes and show more immature characteristics than other chromaffin cell tumors; they are also often multifocal or metastatic and occur at an early age, often during childhood. Cancer stem cells (CSCs) are cells with an inherent ability of self-renewal, de-differentiation, and capacity to initiate and maintain malignant tumor growth. Targeting CSCs to inhibit cancer progression has become an attractive anti-cancer therapeutic strategy. Despite progress for this strategy for solid tumors such as neuroblastoma, brain, breast, and colon cancers, no substantial advance has been made employing similar strategies in PCCs/PGLs. In the current review, we discuss findings related to the identification of normal chromaffin stem cells and CSCs, pathways involved in regulating the development of CSCs, and the importance of the stem cell niche in development and maintenance of CSCs in PCCs/PGLs. Additionally, we examine the development and feasibility of novel CSC-targeted therapeutic strategies aimed at eradicating especially recurrent and metastatic tumors.

Stem Cells, Self-Renewal, and Lineage Commitment in the Endocrine System

The endocrine system coordinates a wide array of body functions mainly through secretion of hormones and their actions on target tissues. Over the last decades, a collective effort between developmental biologists, geneticists, and stem cell biologists has generated a wealth of knowledge related to the contribution of stem/progenitor cells to both organogenesis and self-renewal of endocrine organs. This review provides an up-to-date and comprehensive overview of the role of tissue stem cells in the development and self-renewal of endocrine organs. Pathways governing crucial steps in both development and stemness maintenance, and that are known to be frequently altered in a wide array of endocrine disorders, including cancer, are also described. Crucially, this plethora of information is being channeled into the development of potential new cell-based treatment modalities for endocrine-related illnesses, some of which have made it through clinical trials.

The adrenal gland in stress - Adaptation on a cellular level

Human individuals are constantly confronted to various kinds of stressors and the body's response and adaptation is essential for human health. The adrenal gland as the main producer of stress hormones plays a major role in the response to physiological challenges and is able to adapt to these physiological needs. Proper adaptation is of particular importance since dysregulation of the stress system is the cause of various human diseases including obesity, depression, Parkinson's disease, and post-traumatic stress disorder. Therefore, it is fundamental to understand the physiological, cellular, and molecular underpinnings of the stress adaptation in humans. Because of ethical reasons it is problematic to study the plasticity of the human gland in stress. Hence, various experimental models have been established for the analysis of the functional and cellular role of the adrenal gland adaptation on a translational approach. Here, we summarize the insights of stress-induced adrenal plasticity gained from these models and discuss their relevance to clinical observations.

The carotid body: a physiologically relevant germinal niche in the adult peripheral nervous system

Oxygen constitutes a vital element for the survival of every single cell in multicellular aerobic organisms like mammals. A complex homeostatic oxygen-sensing system has evolved in these organisms, including detectors and effectors, to guarantee a proper supply of the element to every cell. The carotid body represents the most important peripheral arterial chemoreceptor organ in mammals and informs about hypoxemic situations to the effectors at the brainstem cardiorespiratory centers. To optimize organismal adaptation to maintained hypoxemic situations, the carotid body has evolved containing a niche of adult tissue-specific stem cells with the capacity to differentiate into both neuronal and vascular cell types in response to hypoxia. These neurogenic and angiogenic processes are finely regulated by the niche and by hypoxia itself. Our recent data on the cellular and molecular mechanisms underlying the functioning of this niche might help to comprehend a variety of different diseases coursing with carotid body failure, and might also improve our capacity to use these stem cells for the treatment of neurological disease. Herein, we review those data about the recent characterization of the carotid body niche, focusing on the study of the phenotype and behavior of multipotent stem cells within the organ, comparing them with other well-documented neural stem cells within the adult nervous system.

Isolation and characterization of adrenocortical progenitors involved in the adaptation to stress

Humans are constantly confronted with multiple stressors, to which the bodily response and adaptation are essential. The adrenal gland plays a major role in the response to physiological challenges. Maintenance of the adrenal is partly accomplished by proliferation and differentiation of adult progenitors and stem cells in the cortex and medulla. In this study, we have isolated and characterized a subpopulation of adrenocortical progenitors, which are interconnected with adrenomedullary stress-dependent progenitors. Under stress, the adrenocortical progenitors are also activated and they mobilize, giving rise to steroidogenic cells. Our findings demonstrate the coordinated action of stress-inducible stem cells to ensure tissue remodeling and cellular and functional adaptation to stress.

The adrenal gland is a master regulator of the human body during response to stress. This organ shows constant replacement of senescent cells by newly differentiated cells. A high degree of plasticity is critical to sustain homeostasis under different physiological demands. This is achieved in part through proliferation and differentiation of adult adrenal progenitors. Here, we report the isolation and characterization of a Nestin⁺ population of adrenocortical progenitors located under the adrenal capsule and scattered throughout the cortex. These cells are interconnected with progenitors in the medulla. In vivo lineage tracing revealed that, under basal conditions, this population is noncommitted and slowly migrates centripetally. Under stress, this migration is greatly enhanced, and the cells differentiate into steroidogenic cells. Nestin⁺ cells cultured in vitro also show multipotency, as they differentiate into mineralocorticoid and glucocorticoid-producing cells, which can be further influenced by the exposure to Angiotensin II, adrenocorticotropic hormone, and the agonist of luteinizing hormone-releasing hormone, triptorelin. Taken together, Nestin⁺ cells in the adult adrenal cortex exhibit the features of adrenocortical progenitor cells. Our study provides evidence for a role of Nestin⁺ cells in organ homeostasis and emphasizes their role under stress. This cell population might be a potential source of cell replacement for the treatment of adrenal insufficiency.

Nestin in the epididymis is expressed in vascular wall cells and is regulated during postnatal development and in case of testosterone deficiency

Vascular smooth muscle cells (SMCs), distinguished by the expression of the neuronal stem cell marker nestin, may represent stem cell-like progenitor cells in various organs including the testis. We investigated epididymal tissues of adult nestin-GFP mice, rats after Leydig cell depletion via ethane dimethane sulfonate (EDS), rats and mice during postnatal development and human tissues. By use of Clarity, a histochemical method to illustrate a three-dimensional picture, we could demonstrate nestin-GFP positive cells within the vascular network. We localized nestin in the epididymis in proliferating vascular SMCs by colocalization with both smooth muscle actin and PCNA, and it was distinct from CD31-positive endothelial cells. The same nestin localization was found in the human epididymis. However, nestin was not found in SMCs of the epididymal duct. Nestin expression is high during postnatal development of mouse and rat and down-regulated towards adulthood when testosterone levels increase. Nestin increases dramatically in rats after Leydig cell ablation with EDS and subsequently low testosterone levels. Interestingly, during this period, the expression of androgen receptor in the epididymis is low and increases until nestin reaches normal levels of adulthood. Here we show that nestin, a common marker for neuronal stem cells, is also expressed in the vasculature of the epididymis. Our results give new insights into the yet underestimated role of proliferating nestin-expressing vascular SMCs during postnatal development and repair of the epididymis.

Expression of progenitor markers is associated with the functionality of a bioartificial adrenal cortex

Encapsulation of primary bovine adrenocortical cells in alginate is an efficacious model of a bioartificial adrenal cortex. Such a bioartificial adrenal cortex can be used for the restoration of lost adrenal function in vivo as well as for in vitro modeling of the adrenal microenvironment and for investigation of cell–cell interactions in the adrenals. The aim of this work was the optimization of a bioartificial adrenal cortex, that is the generation of a highly productive, self-regenerating, long-term functioning and immune tolerant bioartificial organ. To achieve this, it is necessary that adrenocortical stem and progenitor cells are present in the bioartificial gland, as these undifferentiated cells play important roles in the function of the mature gland. Here, we verified the presence of adrenocortical progenitors in cultures of bovine adrenocortical cells, studied the dynamics of their appearance and growth and determined the optimal time point for cell encapsulation. These procedures increased the functional life span and reduced the immunogenicity of the bioartificial adrenal cortex. This model allows the use of the luteinizing hormone-releasing hormone (LHRH) agonist triptorelin, the neuropeptide bombesin, and retinoic acid to alter cell number and the release of cortisol over long periods of time.

Oxygen sensing and stem cell activation in the hypoxic carotid body

The carotid body (CB) is the major arterial chemoreceptor responsible for the detection of acute decreases in O₂ tension (hypoxia) in arterial blood that trigger hyperventilation and sympathetic activation. The CB contains O₂-sensitive glomus (chief) cells, which respond to hypoxia with the release of transmitters to activate sensory nerve fibers impinging upon the brain respiratory and autonomic centers. During exposure to sustained hypoxia (for weeks or months), the CB grows several-fold in size, a response associated with acclimatization to high altitude or to medical conditions presenting hypoxemia. Here, I briefly present recent advances on the mechanisms underlying glomus cell sensitivity to hypoxia, in particular the role of mitochondrial complex I in acute oxygen sensing. I also summarize the properties of adult CB stem cells and of glomus cell-stem cell synapses, which contribute to CB hypertrophy in chronic hypoxia. A note on the relationship between hypoxic CB growth and tumorigenesis is included. Finally, the medical implications of CB pathophysiology are discussed.

From proliferation to target innervation: signaling molecules that direct sympathetic nervous system development

The sympathetic division of the autonomic nervous system includes a variety of cells including neurons, endocrine cells and glial cells. A recent study (Furlan et al. 2017) has revised thinking about the developmental origin of these cells. It now appears that sympathetic neurons and chromaffin cells of the adrenal medulla do not have an immediate common ancestor in the form a "sympathoadrenal cell", as has been long believed. Instead, chromaffin cells arise from Schwann cell precursors. This review integrates the new findings with the expanding body of knowledge on the signalling pathways and transcription factors that regulate the origin of cells of the sympathetic division of the autonomic nervous system.

Pathology of Human Pheochromocytoma and Paraganglioma Xenografts in NSG Mice

A major impediment to the development of effective treatments for metastatic or unresectable pheochromocytomas and paragangliomas has been the absence of valid models for pre-clinical testing. Attempts to establish cell lines or xenografts from human pheochromocytomas and paragangliomas have previously been unsuccessful. NOD-scid gamma (NSG) mice are a recently developed strain lacking functional B-cells, T-cells, and NK cells. We report here that xenografts of primary human paragangliomas will take in NSG mice while maintaining their architectural and immunophenotypic characteristics as expressed in the patients. In contrast to grafts of cell lines and of most common types of primary tumors, the growth rate of grafted paragangliomas is very slow, accurately representing the growth rate of most pheochromocytomas and paragangliomas even in metastases in humans. Although the model is therefore technically challenging, primary patient-derived xenografts of paragangliomas in NSG mice provide a potentially valuable new tool that could prove especially valuable for testing treatments aimed at eradicating the small tumor deposits that are often numerous in patients with metastatic paraganglioma.

Adrenal cortical and chromaffin stem cells: Is there a common progeny related to stress adaptation?

The adrenal gland is a highly plastic organ with the capacity to adapt the body homeostasis to different physiological needs. The existence of stem-like cells in the adrenal cortex has been revealed in many studies. Recently, we identified and characterized in mice a pool of glia-like multipotent Nestin-expressing progenitor cells, which contributes to the plasticity of the adrenal medulla. In addition, we found that these Nestin progenitors are actively involved in the stress response by giving rise to chromaffin cells. Interestingly, we also observed a Nestin-GFP-positive cell population located under the adrenal capsule and scattered through the cortex. In this article, we discuss the possibility of a common progenitor giving rise to subpopulations of cells both in the adrenal cortex and medulla, the isolation and characterization of this progenitor as well as its clinical potential in transplantation therapies and in pathophysiology.

The effects of stress on brain and adrenal stem cells

The brain and adrenal are critical control centers that maintain body homeostasis under basal and stress conditions, and orchestrate the body's response to stress. It is noteworthy that patients with stress-related disorders exhibit increased vulnerability to mental illness, even years after the stress experience, which is able to generate long-term changes in the brain's architecture and function. High levels of glucocorticoids produced by the adrenal cortex of the stressed subject reduce neurogenesis, which contributes to the development of depression. In support of the brain-adrenal connection in stress, many (but not all) depressed patients have alterations in the components of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis, with enlarged adrenal cortex and increased glucocorticoid levels. Other psychiatric disorders, such as post-traumatic stress disorder, bipolar disorder and depression, are also associated with abnormalities in hippocampal volume and hippocampal function. In addition, hippocampal lesions impair the regulation of the LHPA axis in stress response. Our knowledge of the functional connection between stress, brain function and adrenal has been further expanded by two recent, independent papers that elucidate the effects of stress on brain and adrenal stem cells, showing similarities in the way that the progenitor populations of these organs behave under stress, and shedding more light into the potential cellular and molecular mechanisms involved in the adaptation of tissues to stress.

Adrenal Gland Microenvironment and Its Involvement in the Regulation of Stress-Induced Hormone Secretion during Sepsis

Survival of all living organisms depends on maintenance of a steady state of homeostasis, which process relies on its ability to react and adapt to various physical and emotional threats. The defense against stress is executed by the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal medullary system. Adrenal gland is a major effector organ of stress system. During stress, adrenal gland rapidly responds with increased secretion of glucocorticoids (GCs) and catecholamines into circulation, which hormones, in turn, affect metabolism, to provide acutely energy, vasculature to increase blood pressure, and the immune system to prevent it from extensive activation. Sepsis resulting from microbial infections is a sustained and extreme example of stress situation. In many critical ill patients, levels of both corticotropin-releasing hormone and adrenocorticotropin, the two major regulators of adrenal hormone production, are suppressed. Levels of GCs, however, remain normal or are elevated in these patients, suggesting a shift from central to local intra-adrenal regulation of adrenal stress response. Among many mechanisms potentially involved in this process, reduced GC metabolism and activation of intra-adrenal cellular systems composed of adrenocortical and adrenomedullary cells, endothelial cells, and resident and recruited immune cells play a key role. Hence, dysregulated function of any of these cells and cellular compartments can ultimately affect adrenal stress response. The purpose of this mini review is to highlight recent insights into our understanding of the adrenal gland microenvironment and its role in coordination of stress-induced hormone secretion.

15 YEARS OF PARAGANGLIOMA: Pathology of pheochromocytoma and paraganglioma

Pathologists using their routine diagnostic tools can contribute both to the care of patients with pheochromocytoma/paraganglioma and to understanding the pathobiology of the tumors. They can document details of tissue organization and cytology that are accessible only by microscopy and can characterize admixtures of cell types that are morphologically distinct or show differential expression of immunohistochemical markers. Current roles and challenges for pathologists include differential diagnosis, identifying clues to the presence of hereditary disease, and effective communication of pathology information for clinical and research purposes. Future roles will increasingly involve risk stratification, identification of actionable targets for personalized therapies, and aiding the interpretation of molecular tests by helping characterize genetic variants of unknown significance. It remains to be determined to what extent the need for pathology input will be overshadowed by the availability of genetic testing and other molecular analyses at ever-decreasing cost, together with very effective clinical paradigms for risk stratification and patient care.