The Role of the Hippocampus in the Neuroendocrine Response to Neurobiological Stimuli in Experiment.

We compared the levels of functional activity of cells in each adrenal zone with blood levels of corticosterone, testosterone, and neuropeptide Y in control and hippocampectomized F1(C57BL/6×DBA/2) mice during modeling of metabolic, motivational, and cognitive tension. The morphofunctional state of the adrenal glands was studied using a new morphometric approach. It was found that hippocampectomy changed the testosterone response to neurobiological stimuli; similar changes were observed in the zona reticularis of the adrenal cortex producing dehydroepiandrosterone that is involved in the regulation of testosterone secretion. At the same time, hippocampectomy enhanced the response of the peptide hormone; the index of functional activity of chromaffin cells producing this hormone also increased. These findings allow us to put forward a hypothesis that the hippocampus is involved in the regulation of mutual influences of the studied hormones and that it modulates the sensitivity of testosterone and NPY to metabolic and cognitive factors.

Adrenal Corticosteroid Perturbation by the Endocrine Disruptor BDE-47 in a Human Adrenocortical Cell Line and Male Rats.

Polybrominated diphenyl ethers (PBDEs) have been previously shown to alter various endocrine biosynthetic pathways. Growing epidemiological evidence suggests that PBDEs alter cardiovascular function. The goal of this study was to examine the effects of BDE-47 on adrenal corticosteroid pathways that play vital roles in cardiovascular homeostasis and pathophysiology. The effect of BDE-47 on aldosterone and cortisol secretion was characterized in a human adrenocortical cell line. HAC15 cells were exposed to various concentrations of BDE-47 (1 nM to 100 µM). Cell viability, corticosteroid secretion, gene expression of enzymes involved in corticosteroid synthesis, and metabolic activity was examined. Additionally, Sprague Dawley male rats were orally exposed to BDE-47 (10 or 100 µg/kg), 5 days per week for 16 weeks. Organ weights and plasma corticosteroid levels were measured. In HAC15 cells, basal and stimulated aldosterone and cortisol secretion was significantly increased by BDE-47. Gene expression of several enzymes involved in corticosteroid synthesis and mitochondrial metabolism also increased. In Sprague Dawley rats, adrenal but not heart, kidney, or liver weights, were significantly increased in BDE-47 treatment groups. Plasma corticosterone levels were significantly increased in the 100 µg BDE-47/kg treatment group. No change in plasma aldosterone levels were observed with BDE-47 exposure. These data indicate that BDE-47 disrupts the regulation of corticosteroid secretion and provides further evidence that PBDEs are potential endocrine disruptors. Future studies will determine the underlying molecular mechanism of altered corticosteroid production and examine whether these alterations result in underlying cardiovascular disease in our rodent model of 16-week BDE-47 exposure.

Adrenal cortex renewal in health and disease.

Resident progenitor and/or stem cell populations in the adult adrenal cortex enable cortical cells to undergo homeostatic renewal and regeneration after injury. Renewal occurs predominantly in the outer layers of the adrenal gland but newly formed cells undergo centripetal migration, differentiation and lineage conversion in the process of forming the different functional steroidogenic zones. Over the past 10 years, advances in the genetic characterization of adrenal diseases and studies of mouse models with altered adrenal phenotypes have helped to elucidate the molecular pathways that regulate adrenal tissue renewal, several of which are fine-tuned via complex paracrine and endocrine influences. Moreover, the adrenal gland is a sexually dimorphic organ, and testicular androgens have inhibitory effects on cell proliferation and progenitor cell recruitment in the adrenal cortex. This Review integrates these advances, including the emerging role of sex hormones, into existing knowledge on adrenocortical cell renewal. An in-depth understanding of these mechanisms is expected to contribute to the development of novel therapies for severe endocrine diseases, for which current treatments are unsatisfactory.

Primary Cultures and Cell Lines for In Vitro Modeling of the Human Adrenal Cortex.

The human adrenal cortex is a complex endocrine organ that produces mineralocorticoids, glucocorticoids and androgens. These steroids are produced in distinct cell types located within the glomerulosa, fasciculata and reticularis of the adrenal cortex. Abnormal adrenal steroidogenesis leads to a variety of diseases that can cause hypertension, metabolic syndrome, infertility and premature adrenarche. The adrenal cortex can also develop steroid-producing adenomas and rarely adrenocortical carcinomas. In vitro cell culture models provide important tools to study molecular and cellular mechanisms controlling both the physiologic and pathologic conditions of the adrenal cortex. In addition, the presence of multiple steroid-metabolizing enzymes within adrenal cells makes it a model for defining possible endocrine disruptors that might block these enzymes. The regulation and dysregulation of human adrenal steroid production and cell division/tumor growth can be studied using freshly isolated cells but this requires access to human adrenal glands, which are not available to most investigators. Immortalized human adrenocortical cell lines have proven to be of considerable value in studying the molecular and biochemical mechanisms controlling adrenal steroidogenesis and tumorigenesis. Current human adrenal cell lines include the original NCI-H295 and its substrains: H295A, H295R, HAC13, HAC15, HAC50 and H295RA as well as the recently established MUC-1, CU-ACC1 and CU-ACC2. The current review will discuss the use of primary cultures of fetal and adult adrenal cells as well as adrenocortical cell lines as in vitro models for the study of human adrenal physiology and pathophysiology.

Stem cell function and plasticity in the normal physiology of the adrenal cortex.

The adrenal cortex functions to produce steroid hormones necessary for life. To maintain its functional capacity throughout life, the adrenal cortex must be continually replenished and rapidly repaired following injury. Moreover, the adrenal responds to endocrine-mediated organismal needs, which are highly dynamic and necessitate a precise steroidogenic response. To meet these diverse needs, the adrenal employs multiple cell populations with stem cell function. Here, we discuss the literature on adrenocortical stem cells using hematopoietic stem cells as a benchmark to examine the functional capacity of particular cell populations, including those located in the capsule and peripheral cortex. These populations are coordinately regulated by paracrine and endocrine signaling mechanisms, and display remarkable plasticity to adapt to different physiological and pathological conditions. Some populations also exhibit sex-specific activity, which contributes to highly divergent proliferation rates between sexes. Understanding mechanisms that govern adrenocortical renewal has broad implications for both regenerative medicine and cancer.

Targeted Disruption of Lats1 and Lats2 in Mice Impairs Adrenal Cortex Development and Alters Adrenocortical Cell Fate.

It has recently been shown that the loss of the Hippo signaling effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in adrenocortical steroidogenic cells impairs the postnatal maintenance of the adrenal gland. To further explore the role of Hippo signaling in mouse adrenocortical cells, we conditionally deleted the key Hippo kinases large tumor suppressor homolog kinases 1 and -2 (Lats1 and Lats2, two kinases that antagonize YAP and TAZ transcriptional co-regulatory activity) in steroidogenic cells using an Nr5a1-cre strain (Lats1flox/flox;Lats2flox/flox;Nr5a1-cre). We report here that developing adrenocortical cells adopt characteristics of myofibroblasts in both male and female Lats1flox/flox;Lats2flox/flox;Nr5a1-cre mice, resulting in a loss of steroidogenic gene expression, adrenal failure and death by 2 to 3 weeks of age. A marked accumulation of YAP and TAZ in the nuclei of the myofibroblast-like cell population with an accompanying increase in the expression of their transcriptional target genes in the adrenal glands of Lats1flox/flox;Lats2flox/flox;Nr5a1-cre animals suggested that the myofibroblastic differentiation could be attributed in part to YAP and TAZ. Taken together, our results suggest that Hippo signaling is required to maintain proper adrenocortical cell differentiation and suppresses their differentiation into myofibroblast-like cells.

The Potential Role of Aldosterone-Producing Cell Clusters in Adrenal Disease.

Primary aldosteronism (PA) is the most common cause of secondary hypertension. The hallmark of PA is adrenal production of aldosterone under suppressed renin conditions. PA subtypes include adrenal unilateral and bilateral hyperaldosteronism. Considerable progress has been made in defining the role for somatic gene mutations in aldosterone-producing adenomas (APA) as the primary cause of unilateral PA. This includes the use of next-generation sequencing (NGS) to define recurrent somatic mutations in APA that disrupt calcium signaling, increase aldosterone synthase (CYP11B2) expression, and aldosterone production. The use of CYP11B2 immunohistochemistry on adrenal glands from normal subjects, patients with unilateral and bilateral PA has allowed the identification of CYP11B2-positive cell foci, termed aldosterone-producing cell clusters (APCC). APCC lie beneath the adrenal capsule and like APA, many APCC harbor somatic gene mutations known to increase aldosterone production. These findings suggest that APCC may play a role in pathologic progression of PA. Herein, we provide an update on recent research directed at characterizing APCC and also discuss the unanswered questions related to the role of APCC in PA.

Ginsenoside Rd attenuates ACTH-induced corticosterone secretion by blocking the MC2R-cAMP/PKA/CREB pathway in Y1 mouse adrenocortical cells.

BACKGROUND: Higher levels of glucocorticoids (GCs), and impaired regulation of the hypothalamic-pituitary-adrenal (HPA) axis may cause or exacerbate the occurrence of metabolic and psychiatric disorders. It has been reported that ginseng saponin extract (GSE) has an inhibitory effect on the hyperactivity of the HPA axis induced by stresses and increased corticosterone level induced by intraperitoneal injection of adrenocorticotrophic hormone (ACTH) in mice. However, the molecular mechanisms by which GSE and its active ginsenosides inhibit corticosterone secretion remain elusive. MAIN METHODS: Y1 mouse adrenocortical cells were treated with ACTH for up to 60 min to establish a cell model of corticosterone secretion. After treatment with different concentrations of GSE or ginsenoside monomers for 24 h prior to the addition of ACTH, analyses of cAMP content, PKA activity, and the levels of steroidogenesis regulators, melanocortin-2 receptor (MC2R), and melanocortin-2 receptor accessory protein (MRAP) in ACTH-induced Y1 cells were performed. RESULTS: We demonstrated that GSE inhibits ACTH-stimulated corticosterone production in Y1 cells by inhibiting factors critical for steroid synthesis. Ginsenoside Rd, an active ingredient of GSE, inhibits corticosterone secretion in the cells and impedes ACTH-induced corticosterone biosynthesis through down-regulation of proteins in the cAMP/PKA/CREB signaling pathway. In addition, Western blot and qPCR analyses showed that ginsenoside Rd attenuated the induction of MC2R and MRAP by ACTH. CONCLUSION: Our findings indicate that ginsenoside Rd inhibits ACTH-induced corticosterone production through blockading the MC2R-cAMP/PKA/CREB pathway in adrenocortical cells. Overall, this mechanism may represent an important therapeutic option for the treatment of stress-related disorders, further supporting the pharmacological benefits of ginseng.

Androgen Receptor Is Dispensable for X-Zone Regression in the Female Adrenal but Regulates Post-Partum Corticosterone Levels and Protects Cortex Integrity.

Adrenal androgens are fundamental mediators of ovarian folliculogenesis, embryonic implantation, and breast development. Although adrenal androgen function in target tissues are well characterized, there is little research covering the role of androgen-signaling within the adrenal itself. Adrenal glands express AR which is essential for the regression of the X-zone in male mice. Female mice also undergo X-zone regression during their first pregnancy, however whether this is also controlled by AR signaling is unknown. To understand the role of the androgen receptor (AR) in the female adrenal, we utilized a Cyp11a1-Cre to specifically ablate AR from the mouse adrenal cortex. Results show that AR-signaling is dispensable for adrenal gland development in females, and for X-zone regression during pregnancy, but is required to suppress elevation of corticosterone levels post-partum. Additionally, following disruption to adrenal AR, aberrant spindle cell development is observed in young adult females. These results demonstrate sexually dimorphic regulation of the adrenal X-zone by AR and point to dysfunctional adrenal androgen signaling as a possible mechanism in the early development of adrenal spindle cell hyperplasia.

Tissue non-specific alkaline phosphatase mediates the accumulation of cholesterol esters in the murine Y1 adrenal cortex cell line.

BACKGROUND: Cholesterol esters (CEs) accumulate in the cells of the adrenal cortex and are used for the synthesis of steroid hormones. The full molecular pathways involved in mediating the accumulation of CEs within the adrenal cortex are yet to be elucidated. Tissue non-specific alkaline phosphatase (TNAP) is needed for intracellular lipid accumulation of triglycerides in adipocytes and is also expressed in the cortical cells of the adrenal gland. Therefore we aimed to determine if TNAP is needed for the accumulation of CEs within the murine Y1 adrenal cortex cell line. METHODS: Y1 cells were induced to accumulate lipids. Lipid accumulation and TNAP activity and expression were determined throughout intracellular lipid accumulation. The location of TNAP within the cell was determined through immunohistochemical analysis. Lipid accumulation in the cells was associated with a rise in TNAP activity and TNAP was localised to lipid droplets within the Y1 cells. Inhibition of TNAP with a specific inhibitor (levamisole) resulted in the cessation of CE accumulation. DISCUSSION AND CONCLUSIONS: These data demonstrate that TNAP plays a role in the control of lipid accumulation in this adrenal cortex cell line. Therefore, in both triglyceride and CE storing cell types TNAP would seem to be essential for intra-cellular lipid storage.

ANO4 (Anoctamin 4) Is a Novel Marker of Zona Glomerulosa That Regulates Stimulated Aldosterone Secretion.

Microarray comparison of the transcriptomes of human adrenal zona glomerulosa (ZG) and zona fasciculata found several ZG-specific genes that negatively regulate aldosterone secretion. The third and most significantly upregulated ZG-gene (19.9-fold compared with zona fasciculata, P=6.58×10-24) was ANO4, a putative Ca2+-activated chloride channel. We have investigated the role of ANO4 in human adrenal, and whether it functions like the prototype anoctamin, ANO1. We evaluated ANO4 mRNA and protein expression in human adrenal by qPCR and immunohistochemistry, compared the effects of ANO4 and ANO1 overexpression on baseline and stimulated aldosterone secretion and cell proliferation in H295R cells, and analyzed ANO4 activity as a Ca2+-activated chloride channel in comparison with other anoctamins by a fluorescence-based functional assay. The expression of ANO4 in ZG was confirmed by qPCR as 23.21-fold upregulated compared with zona fasciculata (n=18; P=4.93×10-7). Immunohistochemistry found cytoplasmic, ZG-selective expression of ANO4 (anoctamin 4) protein. ANO4 overexpression in H295R cells attenuated calcium-mediated aldosterone secretion and cell proliferation in comparison to controls. The latter effects were in a different direction to those of ANO1. The functional assay showed that, in contrast to ANO1, ANO4 expression results in low levels of calcium-dependent anion transport. In conclusion, ANO4 is one of the most highly expressed genes in ZG. It attenuates stimulated aldosterone secretion and cell proliferation. Although belonging to a family of Ca2+-activated chloride channels, it does not generate significant plasma membrane chloride channel activity.

Role of Transcription Factor Oct4 in Postnatal Development and Function of the Adrenal Cortex.

We analyzed the expression of transcriptional factor Oct4 in rat adrenal cortical cells during postnatal development. It was found that Oct4 is expressed by typical cortical cells of the zona glomerulosa, zona fasciculata, and zona reticularis in pubertal and postpubertal periods. The maximum number of Oct4+ cells was found in the zona glomerulosa. An inverse correlation between the number of Oct4+ glomerulosa cells and serum level of aldosterone both in pubertal and postpubertal periods was revealed. After puberty, the number of Oct4+ glomerulosa cells directly correlated with the number of Ki-67+ cells. A hypothesis was put forward that Oct4 is involved in postnatal morphogenesis, regeneration, and functioning of the adrenal cortex.

Androgen receptor signalling in the male adrenal facilitates X-zone regression, cell turnover and protects against adrenal degeneration during ageing.

Androgens are known to be an essential regulator of male health. Androgen receptor (AR) is widely expressed throughout the adrenal cortex, yet the wider role for androgen signalling in the adrenal remains underexplored. To investigate AR-dependent and AR-independent androgen signalling in the adrenal, we used a novel mouse model with a specific ablation of androgen receptor in the adrenal cortex with or without reduction of circulating androgen levels by castration. Our results describe AR expression in the human and mouse adrenal and highlight that the mouse is a viable model to investigate androgen signalling in the adrenal cortex. We show androgen signalling via AR is required for X-zone regression during puberty. Furthermore, cortex measurements define differences in X-zone morphology depending on whether circulating androgens or AR have been removed. We show androgens promote both cortical cell differentiation and apoptosis but are dispensable for the formation of the definitive cortex. Additionally, investigation of aged mice with AR ablation reveals severe cortex disruption, spindle cell hyperplasia and X-zone expansion. The data described herein demonstrates AR-signalling is required to facilitate X-zone regression, cell clearance and to protect against adrenal degeneration during ageing.

5-oxo-ETE activates migration of H295R adrenocortical cells via MAPK and PKC pathways.

The OXE receptor is a GPCR activated by eicosanoids produced by the action of 5-lipoxygenase. We previously found that this membrane receptor participates in the regulation of cAMP-dependent and -independent steroidogenesis in human H295R adrenocortical carcinoma cells. In this study we analyzed the effects of the OXE receptor physiological activator 5-oxo-ETE on the growth and migration of H259R cells. While 5-oxo-ETE did not affect the growth of H295R cells, overexpression of OXE receptor caused an increase in cell proliferation, which was further increased by 5-oxo-ETE and blocked by 5-lipoxygenase inhibition. 5-oxo-ETE increased the migratory capacity of H295R cells in wound healing assays, but it did not induce the production of metalloproteases MMP-1, MMP-2, MMP-9 and MMP-10. The pro-migratory effect of 5-oxo-ETE was reduced by pharmacological inhibition of the MEK/ERK1/2, p38 and PKC pathways. 5-oxo-ETE caused significant activation of ERK and p38. ERK activation by the eicosanoid was reduced by the "pan" PKC inhibitor GF109203X but not by the classical PKC inhibitor Gö6976, suggesting the involvement of novel PKCs in this effect. Although H295R cells display detectable phosphorylation of Ser299 in PKCδ, a readout for the activation of this novel PKC, treatment with 5-oxo-ETE per se was unable to induce additional PKCδ activation. Our results revealed signaling effectors activated by 5-oxo-ETE in H295R cells and may have significant implications for our understanding of OXE receptor in adrenocortical cell pathophysiology.

DLK1/PREF1 marks a novel cell population in the human adrenal cortex.

The adrenal cortex governs fundamental metabolic processes though synthesis of glucocorticoid, mineralocorticoids and androgens. Studies in rodents have demonstrated that the cortex undergoes a self-renewal process and that capsular/subcapsular stem/progenitor cell pools differentiate towards functional steroidogenic cells supporting the dynamic centripetal streaming of adrenocortical cells throughout life. We previously demonstrated that the Notch atypical ligand Delta-like homologue 1 (DLK1)/preadipocyte factor 1 (PREF1) is expressed in subcapsular Sf1 and Shh-positive, CYP11B1-negative and CYP11B2-partially positive cortical progenitor cells in rat adrenals, and that secreted DLK1 can modulate GLI1 expression in H295R cells. Here we show that the human adrenal cortex remodels with age to generate clusters of relatively undifferentiated cells expressing DLK1. These clusters (named DLK1-expressing cell clusters or DCCs) increased with age in size and were found to be different entities to aldosterone-producing cell clusters, another well-characterized and age-dependent cluster structure. DLK1 was markedly overexpressed in adrenocortical carcinomas but not in aldosterone-producing adenomas. Thus, this data identifies a novel cell population in the human adrenal cortex and might suggest a yet-to be identified role of DLK1 in the pathogenesis of adrenocortical carcinoma in humans.

Regulation of Proliferative Processes in Rat Adrenal Cortex by Transcriptional Factor PRH under Conditions of Developmental Exposure to Endocrine Disruptor DDT.

The effects of endocrine disrupters of transcriptional control of morphogenesis are poorly studied. Changes in the expression of transcriptional factor PRH and proliferation of adrenal cortical cells were analyzed in pubertal and postpubertal rats exposed prenatally and postnatally to low doses of endocrine disrupter DDT. In rats exposed to DDT, the expression of PRH and proliferation of adrenal cortical cells differed from those in control rats. Association between these parameters was weakened in the zona glomerulosa and zona reticularis and was absent in the zona fasciculata. These findings suggest that exposure to DDT in pre- and postnatal periods impairs the regulation of proliferative processes by transcriptional factor PRH in all zones of rat adrenal cortex, which can be a mechanism of the disruptive action of DDT.

Correlation Between Differentiation of Adrenocortical Zones and Telomere Lengths Measured by Q-FISH.

CONTEXT: Adrenocortical zonation is associated with a markedly complex developmental process, and the pathogenesis and/or etiology of many disorders of adrenocortical zonal development have remained unknown. Cells from the three adrenocortical zones are morphologically and functionally differentiated, and the mature stage of cell development or senescence has been recently reported to be correlated with telomere length. However, the telomere length of each adrenocortical zonal cell has not yet been studied in human adrenal glands. OBJECTIVE: We aimed to study the telomere lengths of adrenocortical parenchymal cells from three different zones of the adrenal glands present during childhood, adolescence, and adulthood. METHODS: Adrenal glands of 30 autopsied subjects, aged between 0 and 68 years, were retrieved from pathology files. The normalized telomere to centromere ratio (NTCR), an index of telomere length, was determined in the parenchymal cells of the zona glomerulosa, zona fasciculata, and zona reticularis (ZR), using quantitative fluorescence in situ hybridization. RESULTS: NTCR of ZR cells was the longest, followed in decreasing order by that of zona glomerulosa and zona fasciculata cells in subjects aged 20 to 68 years, but no substantial differences in NTCR were detected among these three zones in the group <20 years of age. NTCR of ZR increased with age in subjects aged 20 to 68 years, whereas no important age-dependent changes in NTCR were detected in the group <20 years of age. CONCLUSION: The telomere lengths for three zones in adrenal cortex were correlated with their differentiation in adulthood but not in childhood and adolescence.

Primary Culture of Rat Adrenocortical Cells and Assays of Steroidogenic Functions.

The hormone which the adrenal cortex secretes is vital for animals against stress and diseases. The method described here is the procedure of primary cultured rat adrenal cells and related functional assays (immunofluorescence staining of lipid droplet surface protein, as well as corticosterone analysis). Unlike an in vivo model, the variation of interexperiments in adrenal monolayer cultures is less and the experimental condition is easy to control. Besides, the source of rats is also more stable than other animals, like bovine ones. There are also several human adrenal cell lines (NCI-H295, NCI-H295R, SW13, etc.) that can be used in adrenal studies. However, the steroid production of these lines will still be influenced by numerous factors, which include serum lot number, passage number, mutant/loss of distinct genes, etc. Except for lacking 17α-hydroxylase, the primary culture of rat adrenocortical cells is a better and more convenient technique for studying adrenal physiology. In summary, primary rat adrenal cultures could be a good in vitro platform for researchers to investigate the mechanisms of the reagent of interest in the adrenal gland system.

Immunohistochemical demonstration of LH/CG receptors in non-neoplastic human adrenal cortex and adrenocortical tumors.

INTRODUCTION: Numerous data indicate that luteinizing hormone and/or chorionic gonadotropin (LH/CG) exert direct actions on the adrenal cortex and are involved in the adrenal pathology. However, the immunohistochemical studies on the expression of LH/CG receptors (LH/CGR) in the human adrenal cortex and in the adrenocortical tumors are scarce. MATERIAL AND METHODS: Paraffin sections of samples of 6 human non-neoplastic adrenal cortex and 25 adrenocortical tumors were immunostained with anti-LH/CGR polyclonal antibody. RESULTS: All zones of the human non-neoplastic adrenal cortex present a positive immunoreaction with anti-LH/CGR antibody showing the strongest reaction in cell membranes. The LH/CGR immunostaining in the vast majority of hormonally non-functioning adenomas and in all hormone-secreting adenomas does not differ from the non-neoplastic adrenal cortex. In contrast to non-neoplastic adrenal cortex and benign adenomas, in adrenocortical cancers the immunostaining with anti-LH/CGR antibody behaves differently. The immunopositive material is almost totally filling the cytoplasm of the cells but the immunopositivity of cell membranes is weak or lacking. CONCLUSIONS: The data presented in our study show that the expression of LH/CGR in adrenocortical tumors is not ectopic but eutopic. The immunohistochemical examination of LH/CGR may be useful in the differentiation between benign and malignant lesions in the adrenal cortex. Moreover, the loss of membrane localization of LH/CGR in adrenocortical cancer suggests the alteration of receptors' function.

The transient cortical zone in the adrenal gland: the mystery of the adrenal X-zone.

The X-zone is a transient cortical region enriched in eosinophilic cells located in the cortical-medullary boundary of the mouse adrenal gland. Similar to the X-zone, the fetal zone in human adrenals is also a transient cortical compartment, comprising the majority of the human fetal adrenal gland. During adrenal development, fetal cortical cells are gradually replaced by newly formed adult cortical cells that develop into outer definitive zones. In mice, the regression of this fetal cell population is sexually dimorphic. Many mouse models with mutations associated with endocrine factors have been reported with X-zone phenotypes. Increasing findings indicate that the cell fate of this aged cell population of the adrenal cortex can be manipulated by many hormonal and nonhormonal factors. This review summarizes the current knowledge of this transient adrenocortical zone with an emphasis on genes and signaling pathways that affect X-zone cells.