Aldosterone-producing Cell Clusters Research Articles

Diverse pathological lesions of primary aldosteronism and their clinical significance

Primary aldosteronism (PA) is mainly clinically classified as unilateral aldosterone-producing adenoma (APA) or bilateral idiopathic hyperaldosteronism. Immunohistochemistry for aldosterone synthase reveals a diverse PA pathology, including pathological APA and aldosterone-producing cell clusters. The relationship between PA pathology and adrenalectomy outcomes was examined herein. Data from 219 unilaterally adrenalectomized PA cases were analyzed. Pathological analyses revealed diverse putative aldosterone-producing lesions. Postoperative biochemical outcomes in 114 cases (test cohort) were classified as complete success (n = 85), partial success (n = 19), and absent success (n = 10). Outcomes in the large and small PA lesion groups, rather than between PA lesion types, were compared at five threshold values for PA lesion sizes (2–6 mm with 1-mm increments) to streamline the results. The proportion of complete success was significantly higher in the large PA lesion group than in the small PA lesion group at the 5-mm threshold only. The proportion of absent success was significantly higher in the small PA lesion group than in the large PA lesion group at all thresholds. Univariate and multivariate analyses of the test cohort identified serum K as an independent predictive factor for the small PA lesion group, which was confirmed in the 105-case validation cohort. Chi-squared automatic interaction detector analysis revealed that the best threshold of serum K for predicting large PA lesions was 2.82 mEq/L. These results will be beneficial for treating PA in clinical settings because patients with low serum K levels and apparent adrenal masses on CT may be subjected to adrenalectomy even if the adrenal venous sampling test is unavailable.

DNA Methylation of Steroidogenic Enzymes in Benign Adrenocortical Tumors: New Insights in Aldosterone-Producing Adenomas.

DNA methylation has been identified among putative regulatory mechanisms for CYP11B2 expression in primary aldosteronism. The objective of this work is to investigate DNA methylation and expression of genes encoding steroidogenic enzymes in benign adrenocortical tumors. This cross-sectional study took place at university hospitals. We collected fresh-frozen tissues from patients with benign adrenocortical adenomas (n = 48) (nonfunctioning n = 9, autonomous cortisol secretion n = 9, Cushing syndrome n = 17, aldosterone-producing [APA] n = 13) and adrenal cortex adjacent to APA (n = 12). We collected formalin-fixed, paraffin-embedded (FFPE) specimens of paired APA and concurrent aldosterone-producing cell clusters (APCCs) (n = 6). DNA methylation levels were evaluated by quantitative bisulfite next-generation sequencing in fresh-frozen tissues (CYP11A1, CYP11B1, CYP11B2, CYP17A1, CYP21A2, HSD3B1, HSD3B2, NR5A1, STAR, and TSPO) and FFPE APA/APCC paired samples (CYP11B2). CYP11B1, CYP11B2, CYP17, CYP21, and STAR gene expressions were examined by quantitative real-time polymerase chain reaction. The main outcome measure was DNA methylation. CYP11B2 methylation levels were significantly lower in APA than in other adrenal tissues (P < .001). Methylation levels of the remaining genes were comparable among groups. Overall, CYP11B2 expression and DNA methylation were negatively correlated (ρ = -0.379; P = .003). In FFPE-paired APA/APCC samples, CYP11B2 methylation level was significantly lower in APA than in concurrent APCCs (P = .028). DNA methylation plays a regulatory role for CYP11B2 expression and may contribute to aldosterone hypersecretion in APA. Lower CYP11B2 methylation levels in APA than in APCCs may suggest an APCC-to-APA switch via progressive CYP11B2 demethylation. Conversely, DNA methylation seems not to be relevant in regulating the expression of genes encoding steroidogenic enzymes other than CYP11B2.

CYP11B2 DNA methylation pattern is discordant in aldosterone-producing adenomas and in concurrent aldosterone-producing cell clusters

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

A case of renovascular hypertension with incidental primary bilateral macronodular adrenocortical hyperplasia.

SummaryRenovascular hypertension (RVHT) is an important and potentially treatable form of resistant hypertension. Hypercortisolemia could also cause hypertension and diabetes mellitus. We experienced a case wherein adrenalectomy markedly improved blood pressure and plasma glucose levels in a patient with RVHT and low-level autonomous cortisol secretion. A 62-year-old Japanese man had been treated for hypertension and diabetes mellitus for 10 years. He was hospitalized because of a disturbance in consciousness. His blood pressure (BP) was 236/118 mmHg, pulse rate was 132 beats/min, and plasma glucose level was 712 mg/dL. Abdominal CT scanning revealed the presence of bilateral adrenal masses and left atrophic kidney. Abdominal magnetic resonance angiography demonstrated marked stenosis of the left main renal artery. The patient was subsequently diagnosed with atherosclerotic RVHT with left renal artery stenosis. His left adrenal lobular mass was over 40 mm and it was clinically suspected the potential for cortisol overproduction. Therefore, laparoscopic left nephrectomy and adrenalectomy were simultaneously performed, resulting in improved BP and glucose levels. Pathological studies revealed the presence of multiple cortisol-producing adrenal nodules and aldosterone-producing cell clusters in the adjacent left adrenal cortex. In the present case, the activated renin-angiotensin-aldosterone system and cortisol overproduction resulted in severe hypertension, which was managed with simultaneous unilateral nephrectomy and adrenalectomy.Learning points:Concomitant activation of the renin-angiotensin-aldosterone system and cortisol overproduction may contribute to the development of severe hypertension and lead to lethal cardiovascular complications.Treatment with simultaneous unilateral nephrectomy and adrenalectomy markedly improves BP and blood glucose levels.CYP11B2 immunohistochemistry staining revealed the existence of aldosterone-producing cell clusters (APCCs) in the adjacent non-nodular adrenal gland, suggesting that APCCs may contribute to aldosterone overproduction in patients with RVHT.

OR09-05 Expression of SLC35F1 in the Plasma Membrane of Cells of Aldosterone Producing Cell Clusters (APCCs) and Its Possible Role in Aldosterone Synthesis

Background Genetic mutations and histological appearances suggest that APCCs are precursors to some aldosterone producing adenomas (APA). They are hypothesised to contribute to post-operative non-cure and recurrence of primary aldosteronism (PA) but are currently undetectable pre-operatively. SLC35F1 is a possible nucleotide sugar transporter. On microarray it is highly expressed in APCCs, but not in the rest of the adrenal cortex (1). Our aim was to investigate the role of SLC35F1 in APCCs, determine its subcellular localisation and establish whether expression is consistent with pathological APCC subtypes (as suggested by recent evidence from in situ metabolomic studies (2)). Methods Comparative bioinformatic analysis of the SLC35F1 amino acid sequence was carried out. Ex vivo 4uM adrenal sections, from 6 PA patients in the MATCH study, were stained on serial sections with anti-CYP11B2 (Gomez-Sanchez) or anti-SLC35F1 (Novus NBP1-86755). In vitro, H295R cells were transfected with SLC35F1 cDNA. Subcellular localisation of SLC35F1-GFP was studied by comparison to organelle markers (golgin 97, RAB11, wheat germ agglutinin, calnexin and Tom20) using confocal microscopy. Overexpression and siRNA knock-down in H295R cells was correlated to aldosterone production. Results SLC35F1 is a decamembrane-spanning transporter molecule predicted to have a negatively charged pocket in the substrate binding site, implying a transport substrate with a positive charge. Strong staining of CYP11B2 in clusters of cells in adrenal cortex, consistent with APCCs, were present in all six adrenal glands (25 APCCs). Serial sections showed specific SLC35F1 staining of APCCs, in cytoplasm and plasma membrane. SLC35F1 staining was absent from normal cortex. 12 APCCs (48%) were SLC35F1-negative. Visualisation of transiently expressed SLC35F1 demonstrated localisation to the endoplasmic reticulum in H295R cells (Pearson’s coefficient r=0.758) with no plasma membrane localisation (r=-0.07). Preliminary transfection data suggest direct involvement in aldosterone production. Conclusions Expression of SLC35F1 in the plasma membrane and cytosol of APCC cells supports a role in pathological aldosterone production by APCCs. The inferred transport substrate of SLC35F1 is the NAD(P)(H) precursor, nicotinamide riboside, a positively-charged nucleotide sugar. If confirmed, the essential requirement for NAD(P)H in steroidogenesis, and heterogeneity of SLC35F1-staining in APCCs, is consistent with a metabolically active, possibly pathological, subtype of APCCs. Detection of SLC35F1 in vivo may therefore facilitate sub-classification of PA patients.1). Nishimoto et. al. PNAS. 2015 Aug 18;112(33):E4591-9. 2). Murakami et. al. 2019 Hypertension. In press.

OR19-02 Luteinizing Hormone/Human Chorionic Gonadotropin Receptor Protein Expression in Adrenocortical Progenitor Cells, Aldosterone Producing Cell Clusters and Adrenal Adenomas Derived from Postmenopausal Women

Objective/BackgroundAdrenal pathologies are more common in women than men. Embryologically the adrenals and gonads develop from the adrenogenital ridge with differential migration and differentiation. We hypothesized that in adult females there are adrenocortical progenitor cells that express the LH/hCG-R and proliferate in response to elevated LH. Indeed, several case reports demonstrated LH/hCG-R expression in adrenal secretory tumors in postmenopausal and pregnant females. In aging adults, nests of cells known as aldosterone-producing cell clusters (APCCs) that may be precursors to aldosterone producing adenomas are frequently detected. We retrospectively studied the immunohistochemical expression of LH/hCG-R in normal adrenals, adrenal adenomas and APCCs in archival specimens derived from post-menopausal women.MethodsArchival specimens from adrenal adenomas derived from 23 women >55 years of age were examined. Clinical data was obtained in a blinded fashion and hormonal data was available in 9/23 cases; 6/9 were secreting cortisol and 3/9 adenomas were secreting aldosterone. In addition, 6 samples derived from a repository of normal adrenal tissues from deceased kidney donors (1 male, and 5 postmenopausal females) were studied. All specimens were immunostained for LH/hCG-R and the adrenal stem cell marker DLK1 that facilitates the maintenance of an undifferentiated phenotype. The normal adrenal tissues were also stained for aldosterone synthase (CYP11B2) to detect APCCs. The slides were reviewed and graded by a pathologist in a blinded fashion.ResultsExpression of LH/hCG-R was demonstrated in both normal and adenomatous tissues in all 23 specimens. The staining in adenomas was heterogeneous, with clusters of densely stained LH/hCG-R positive cells in all specimens. There were less densely stained clusters in normal adjacent adrenocortical tissue that was most prominent in the subcapsular, zona glomerulosa region, an area where the putative adrenal cortical stem cells are found as well as the zona reticularis. Double staining for the stem cell marker DLK1 and LH/hCG-R confirmed that these cells represent adrenocortical progenitor cells. CYP 11B2 immunohistochemistry of normal adrenals demonstrated cell foci dipping from the capsule into the zona fasciculata classified as APCCs that co-expressed cytoplasmic LH/hCGR.ConclusionAdrenal adenomas and APCCs derived from postmenopausal women exhibited heterogeneous but strong immunohistochemical expression of LH/hCG-R in all samples. Interestingly, DLK1-positive adrenocortical stem cells in the subcapsular zone also expressed LH/hCG-R. These data may provide insights into the female predominance of adrenal pathologies, particularly in postmenopausal women with high LH levels. The LH/hCG-R may be a viable target for treatment of adrenal adenomas in postmenopausal women.

SUN-195 Bilateral Aldosterone-Producing Adenomas: A New Subtype of Bilateral Primary Aldosteronism?

Background: Primary aldosteronism (PA) is the most common cause of endocrine hypertension (HT). PA subtypes include aldosterone-producing adenomas (APA) and bilateral adrenal hyperplasia. To date, few PA patients with bilateral adenomas have been reported, but only one case was well characterized by anatomopathological analysis and clinical outcome after adrenal sparing surgery (1). Clinical case: A 53-year-old woman was referred to investigate resistant HT and hypokalemia. (3.0 mEq/L). PA screening revealed aldosterone (A) of 37.9 ng/dL, renin (R) < 1.6 (4.4-46.1 mUI/L), A/R ratio of 24.8. Confirmatory testing confirmed PA diagnosis: seated saline infusion test (A= 83.3 ng/dL) and intravenous furosemide test (R= 3.1 mUI/L; positive test <13 mUI/L). Hypercortisolism investigation revealed a non-suppressible cortisol after an overnight 1 mg low-dose dexamethasone suppression [cortisol (C)= 2.9 μg/dL and dexamethasone= 701 (˃130 ng/dL)], and normal urinary free cortisol, midnight salivary cortisol, plasma DHEAS and ACTH levels. Computed tomography demonstrated bilateral adrenal nodules without adrenal thickening: 3.5 cm right nodule (pre-contrast density of 7UH density; absolute wash-out of 71%) and 2.5 cm left nodule (pre-contrast density of 8UH density; absolute wash-out of 78%). Sequential adrenal venous (AV) sampling (AVS) under continuous cosyntropin infusion showed a lateralization index of 3.4 (bilateral disease <4). Then, the patient underwent right adrenalectomy and left nodulectomy. In the postoperative period, she presented normalization of K+ levels and complete HT remission. She remained under hydrocortisone replacement for 2 months. After 2 months, biochemical evaluation revealed normal basal cortisol levels (13.3 µg/dL) and biochemical cure of PA (A= 3.1 ng/dL and R= 15.3 mUI/L). Currently, she doesn’t have symptoms of adrenal insufficiency after discontinuation of hydrocortisone. Anatomopathological analysis showed bilateral adenomas (Weiss score of 0) in both sides without adjacent hyperplasia. CYP11B2 immunohistochemistry displayed a strong staining in 50% of cells in the right adenoma and in 30% of cells in the left adenoma. Few aldosterone-producing cell clusters (APCC) were identified in the right zona glomerulosa, which is a frequent finding in normal adrenals. Conclusion: We herein described a very rare case of PA caused by bilateral-producing adenomas, confirmed by AVS and CYP11B2 staining after adrenal sparing surgery.

MON-LB043 A Case of Renovascular Hypertension With Cortisol-Producing Adrenal Masses

Renovascular hypertension (RVHT) is an important and potentially treatable form of resistant hypertension. Hypercortisolemia could also cause hypertension and diabetes mellitus. We experienced a case wherein adrenalectomy markedly improved blood pressure and plasma glucose levels in a patient with RVHT and subclinical Cushing’s syndrome. A 62-year-old Japanese man had been treated for hypertension and diabetes mellitus for 10 years. He was hospitalized because of disturbance in consciousness. His blood pressure (BP) was 236/118 mmHg; pulse rate, 132 beats/min; and plasma glucose level, 712 mg/dl. Abdominal computed tomography scanning revealed the presence of bilateral adrenal masses and left atrophic kidney. Abdominal magnetic resonance angiography demonstrated marked stenosis of the left main renal artery. The patient was subsequently diagnosed with atherosclerotic RVHT with left renal artery stenosis. Bilateral adrenal masses were immunohistologically identified as potential sites for cortisol overproduction. Therefore, laparoscopic left nephrectomy and adrenalectomy were simultaneously performed resulting in improved BP and glucose levels. Pathological studies revealed the presence of multiple cortisol-producing adrenal nodules and aldosterone-producing cell clusters in the adjacent left adrenal cortex. In the present case, activated renin-angiotensin-aldosterone system and cortisol overproduction resulted in severe hypertension, which was managed with simultaneous unilateral nephrectomy and adrenalectomy.

Primary Aldosteronism in the Elderly.

The clinical spectrum and knowledge of the molecular mechanisms underlying primary aldosteronism (PA), the most frequent form of endocrine hypertension, has evolved over recent years. In accordance with the Endocrine Society guidelines and in light of the growing evidence showing adverse cardiovascular outcomes, it is expected that a progressively wider population of patients affected by hypertension will be screened for PA, including the elderly. A systematic search of PubMed was undertaken for studies related to the renin-angiotensin-aldosterone system (RAAS), PA, and adrenal histopathology in the elderly population. Several studies showed an age-dependent decrease in the activity of RAAS, together with a progressive decrease of the aldosterone response to sodium intake, particularly after the sixth decade of life. The positive correlation between age and serum aldosterone during liberal sodium intake over serum aldosterone during sodium restriction is paralleled by histological changes in adrenal aldosterone synthase (CYP11B2) expression patterns. Immunohistochemical studies showed a progressive loss of the continuous expression of CYP11B2 in the adrenal zona glomerulosa with aging and a concomitant increase of aldosterone-producing cell clusters, which might be responsible for relatively autonomous aldosterone production. Additionally, following PA confirmation and subtype diagnosis, older age is correlated with a lower benefit after adrenalectomy for unilateral PA. Accumulating evidence suggests that RAAS physiology and regulation show age-related changes. Further studies may investigate to what extent these variations might affect the diagnostic workup of patients affected by PA.

Immunohistochemistry of the Human Adrenal CYP11B2 in Normal Individuals and in Patients with Primary Aldosteronism.

The CYP11B2 enzyme is the terminal enzyme in the biosynthesis of aldosterone. Immunohistochemistry using antibodies against CYP11B2 defines cells of the adrenal ZG that synthesize aldosterone. CYP11B2 expression is normally stimulated by angiotensin II, but becomes autonomous in primary hyperaldosteronism, in most cases driven by recently discovered somatic mutations of ion channels or pumps. Cells expressing CYP11B2 in young normal humans form a continuous band beneath the adrenal capsule; in older individuals they form discrete clusters, aldosterone-producing cell clusters (APCC), surrounded by non-aldosterone producing cells in the outer layer of the adrenal gland. Aldosterone-producing adenomas may exhibit a uniform or heterogeneous expression of CYP11B2. APCC frequently persist in the adrenal with an aldosterone-producing adenoma suggesting autonomous CYP11B2 expression in these cells as well. This was confirmed by finding known mutations that drive aldosterone production in adenomas in the APCC of clinically normal people. Unilateral aldosteronism may also be due to multiple CYP11B2-expressing nodules of various sizes or a continuous band of hyperplastic ZG cells expressing CYP11B2. Use of CYP11B2 antibodies to identify areas for sequencing has greatly facilitated the detection of aldosterone-driving mutations.

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.

Genetic, Cellular, and Molecular Heterogeneity in Adrenals With Aldosterone-Producing Adenoma.

Aldosterone-producing adenoma (APA) cause primary aldosteronism-the most frequent form of secondary hypertension. Somatic mutations in genes coding for ion channels and ATPases are found in APA and in aldosterone-producing cell clusters. We investigated the genetic, cellular, and molecular heterogeneity of different aldosterone-producing structures in adrenals with APA, to get insight into the mechanisms driving their development and to investigate their clinical and biochemical correlates. Genetic analysis of APA, aldosterone-producing cell clusters, and secondary nodules was performed in adrenal tissues from 49 patients by next-generation sequencing following CYP11B2 immunohistochemistry. Results were correlated with clinical and biochemical characteristics of patients, steroid profiles, and histological features of the tumor and adjacent adrenal cortex. Somatic mutations were identified in 93.75% of APAs. Adenoma carrying KCNJ5 mutations had more clear cells and cells expressing CYP11B1, and fewer cells expressing CYP11B2 or activated β-catenin, compared with other mutational groups. 18-hydroxycortisol and 18-oxocortisol were higher in patients carrying KCNJ5 mutations and correlated with histological features of adenoma; however, mutational status could not be predicted using steroid profiling. Heterogeneous CYP11B2 expression in KCNJ5-mutated adenoma was not associated with genetic heterogeneity. Different mutations were identified in secondary nodules expressing aldosterone synthase and in independent aldosterone-producing cell clusters from adrenals with adenoma; known KCNJ5 mutations were identified in 5 aldosterone-producing cell clusters. Genetic heterogeneity in different aldosterone-producing structures in the same adrenal suggests complex mechanisms underlying APA development.

Mass Spectrometry Imaging Establishes 2 Distinct Metabolic Phenotypes of Aldosterone-Producing Cell Clusters in Primary Aldosteronism.

Aldosterone-producing adenomas (APAs) are one of the main causes of primary aldosteronism and the most prevalent surgically correctable form of hypertension. Aldosterone-producing cell clusters (APCCs) comprise tight nests of zona glomerulosa cells, strongly positive for CYP11B2 (aldosterone synthase) in immunohistochemistry. APCCs have been suggested as possible precursors of APAs because they frequently carry driver mutations for constitutive aldosterone production, and a few adrenal lesions with histopathologic features of both APCCs and APAs have been identified. Our objective was to investigate the metabolic phenotypes of APCCs (n=27) compared with APAs (n=6) using in situ matrix-assisted laser desorption/ionization mass spectrometry imaging of formalin-fixed paraffin-embedded adrenals from patients with unilateral primary aldosteronism. Specific distribution patterns of metabolites were associated with APCCs and classified 2 separate APCC subgroups (subgroups 1 and 2) indistinguishable by CYP11B2 immunohistochemistry. Metabolic profiles of APCCs in subgroup 1 were tightly clustered and distinct from subgroup 2 and APAs. Multiple APCCs from the same adrenal displayed metabolic profiles of the same subgroup. Metabolites of APCC subgroup 2 were highly similar to the APA group and indicated enhanced metabolic pathways favoring cell proliferation compared with APCC subgroup 1. In conclusion, we demonstrate specific subgroups of APCCs with strikingly divergent distribution patterns of metabolites. One subgroup displays a metabolic phenotype convergent with APAs and may represent the progression of APCCs to APAs.

Endoplasmic Reticulum Chaperone Calmegin Is Upregulated in Aldosterone-Producing Adenoma and Associates With Aldosterone Production.

The endoplasmic reticulum (ER) plays a pivotal role in syntheses of proteins and steroid hormones and regulation of intracellular Ca2+ level. We aimed to investigate ER-associated genes in aldosterone-producing adenomas (APAs) and clarify their effect on aldosterone production. Microarray analysis targeting 288 ER-associated genes was conducted using nonfunctioning adrenocortical adenomas (n=5) and APAs (n=19). Immunohistochemistry and quantitative polymerase chain reaction analyses were performed with 13 nonfunctioning adrenocortical adenoma and 48 APA samples. Functional studies were performed with human adrenocortical carcinoma (HAC15) cells, some of which were genetically modified using lentiviruses. The ER chaperone calmegin (CLGN) was the most highly expressed ER-associated gene in APAs relative to nonfunctioning adrenocortical adenomas. Analysis with quantitative polymerase chain reaction revealed CLGN to be 9.5-fold upregulated in APAs relative to nonfunctioning adrenocortical adenomas. There were no differences among different APA genotypes affecting aldosterone production. Immunohistochemistry analysis revealed that CLGN was strongly expressed in APAs and aldosterone-producing cell clusters. Angiotensin II stimulation or KCNJ5 T158A overexpression in HAC15 cells did not affect CLGN mRNA levels. CLGN overexpression in HAC15 cells increased aldosterone levels but did not stimulate CYP11B2 mRNA levels. Pathway and gene ontology analyses using RNA sequencing results showed that tRNA aminoacyl metabolism was the most enriched pathway in CLGN-overexpressing cells. CYP11B2 (aldosterone synthase) and HSD3B2 (3 beta-hydroxysteroid dehydrogenase/delta 5->4-isomerase type 2) protein expression were more abundant in CLGN-overexpressing cells. CLGN knockdown using CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9) method in HAC15 cells that carry the KCNJ5 mutation did not affect aldosterone production. To summarize, CLGN was upregulated and associated with aldosterone production via translational regulation of CYP11B2 in APAs.

Application of CYP11B2 immunohistochemistry in the histopathological diagnosis of primary aldosteronism

Objective To evaluate the value of CYP11B2 immunohistochemistry in the histopathological diagnosis of primary aldosteronism(PA) among Chinese population. Methods Ninety-six cases of unilateral PA patients were retrospectively enrolled, and with 15 cases of non-hyperfunctioning adenoma, and 15 cases of cortisol producing adenoma as control. CYP11B2 immunohistochemistry was performed in the tumor sections of these patients and was analysed by semi-quantified method. The positive rate of CYP11B2 in tumor specimen of all cases enrolled was calculated and PA patients were subtypely classified based on their histopathological features and CYP11B2 expressions. Results The immune-positive rate of CYP11B2 in the PA group was 91.7% (88/96), with the control group being 6.7% (2/30, P<0.001). Subgroup analysis revealed that the immune-positive rate of CYP11B2 in the aldosterone producing adenoma group and unilateral hyperplasia group were 91.8% (78/85) and 90.9% (10/11), respectively. Based upon histopathological feature and CYP11B2 immunohistochemistry, PA patients were further subtypely classified as aldosterone producing adenoma (85/96), unilateral diffuse adrenocortical hyperplasia (7/96), unilateral mono-adrenocortical micronodules (1/96), unilateral multiple adrenocortical micronodules (1/96), and unilateral multiple aldosterone-producing cell clusters (multiple APCCs, 2/96). Conclusion CYP11B2 immunohistochemistry may serve as an useful tool for the histopathological diagnosis of PA. Key words: Primary aldosteronism; Immunohistochemistry; Pathological diagnosis

Primary aldosteronism : Genetics and pathology

Primary aldosteronism, the excessive production of the steroid hormone aldosterone, is the most common cause of secondary hypertension. Common subforms include bilateral adrenal hyperplasia and aldosterone-producing adenoma. The goal of this review is to summarize important publications on the genetic basis of primary aldosteronism. Somatic mutations in the KCNJ5, CACNA1D, ATP1A1, and ATP2B3 genes have been described as causes of aldosterone-producing adenomas. They eventually all lead to increased cellular calcium influx and aldosterone production. The mechanisms of rare CTNNB1 mutations are less defined. Correlations between mutations and different histologic characteristics as well as gender and ethnicity remain unexplained. Recent publications suggest that bilateral hyperplasia is at least partially due to so-called aldosterone-producing cell clusters, often with mutations in CACNA1D. Rare familial forms show mutations in the CYP11B2, CLCN2, KCNJ5, CACNA1H, or CACNA1D genes. These results suggest that asignificant fraction of primary aldosteronism is due to somatic mutations in single genes.

SLC35F1, a potential marker for aldosterone producing cell clusters

SLC35F1, a potential marker for aldosterone producing cell clusters

Molecular mechanisms in primary aldosteronism

Primary aldosteronism (PA) is the most common form and an under-diagnosed cause of secondary arterial hypertension, accounting for up to 10% of hypertensive cases and associated to increased cardiovascular risk. PA is caused by autonomous overproduction of aldosterone by the adrenal cortex. It is mainly caused by a unilateral aldosterone-producing adenoma (APA) or bilateral adrenal hyperplasia. Excess aldosterone leads to arterial hypertension with suppressed renin, frequently associated to hypokalemia. Mutations in genes coding for ion channels and ATPases have been identified in APA, explaining the pathophysiology of increased aldosterone production. Different inherited genetic abnormalities led to the distinction of four forms of familial hyperaldosteronism (type I to IV) and other genetic defects very likely remain to be identified. Somatic mutations are identified in APA, but also in aldosterone-producing cell clusters (APCCs) in normal adrenals, in image-negative unilateral hyperplasia, in transitional lesions and in APCC from adrenals with bilateral adrenal hyperplasia (BAH). Whether these structures are precursors of APA or whether somatic mutations occur in a proliferative adrenal cortex, is still a matter of debate. This review will summarize our knowledge on the molecular mechanisms responsible for PA and the recent discovery of new genes related to early-onset and familial forms of the disease. We will also address new issues concerning genomic and proteomic changes in adrenals with APA and discuss adrenal pathophysiology in relation to aldosterone-producing structures in the adrenal cortex.

Primary Aldosteronism: KCNJ5 Mutations and Adrenocortical Cell Growth.

Aldosterone-producing adenomas with somatic mutations in the KCNJ5 G-protein-coupled inwardly rectifying potassium channel are a cause of primary aldosteronism. These mutations drive aldosterone excess, but their role in cell growth is undefined. Our objective was to determine the role of KCNJ5 mutations in adrenal cell proliferation and apoptosis. The Ki67 proliferative index was positively correlated with adenoma diameter in aldosterone-producing adenomas with a KCNJ5 mutation (r=0.435, P=0.007), a negative correlation was noted in adenomas with no mutation detected (r=-0.548, P=0.023). Human adrenocortical cell lines were established with stable expression of cumate-inducible wild-type or mutated KCNJ5. Increased cell proliferation was induced by low-level induction of KCNJ5-T158A expression compared with control cells (P=0.009), but increased induction ablated this difference. KCNJ5-G151R displayed no apparent proliferative effect, but KCNJ5-G151E and L168R mutations each resulted in decreased cell proliferation (difference P<0.0001 from control cells, both comparisons). Under conditions tested, T158A had no effect on apoptosis, but apoptosis increased with expression of G151R (P<0.0001), G151E (P=0.008), and L168R (P<0.0001). We generated a specific KCNJ5 monoclonal antibody which was used in immunohistochemistry to demonstrate strong KCNJ5 expression in adenomas without a KCNJ5 mutation and in the zona glomerulosa adjacent to adenomas irrespective of genotype as well as in aldosterone-producing cell clusters. Double immunofluorescence staining for KCNJ5 and CYP11B2 (aldosterone synthase) showed markedly decreased KCNJ5 immunostaining in CYP11B2-positive cells compared with CYP11B2-negative cells in aldosterone-producing adenomas with a KCNJ5 mutation. Together, these findings support the concept that cell growth effects of KCNJ5 mutations are determined by the expression level of the mutated channel.

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.