Bilateral Adrenal Hyperplasia: Pathogenesis and Treatment

Bilateral adrenal hyperplasia is a rare cause of Cushing’s syndrome. Micronodular adrenal hyperplasia, including the primary pigmented micronodular adrenal dysplasia (PPNAD) and the isolated micronodular adrenal hyperplasia (iMAD), can be distinguished from the primary bilateral macronodular adrenal hyperplasia (PBMAH) according to the size of the nodules. They both lead to overt or subclinical CS. In the latter case, PPNAD is usually diagnosed after a systematic screening in patients presenting with Carney complex, while for PBMAH, the diagnosis is often incidental on imaging. Identification of causal genes and genetic counseling also help in the diagnoses. This review discusses the last decades’ findings on genetic and molecular causes of bilateral adrenal hyperplasia, including the several mechanisms altering the PKA pathway, the recent discovery of ARMC5, and the role of the adrenal paracrine regulation. Finally, the treatment of bilateral adrenal hyperplasia will be discussed, focusing on current data on unilateral adrenalectomy.

Colocalization of Wnt/β-catenin and ACTH signaling pathways and paracrine regulation in aldosterone producing adenoma

Context Aldosterone-producing adenomas (APA) are a common cause of primary aldosteronism. Despite the discovery of somatic mutations in APA and characterization of multiple factors regulating adrenal differentiation and function, the sequence of events leading to APA formation remains to be determined. Objective We investigated the role of Wnt/β-catenin and ACTH signaling, as well as elements of paracrine regulation of aldosterone biosynthesis in adrenals with APA and their relationship to intratumoral heterogeneity and mutational status. Design We analyzed expression of CYP11B2, CYP17A1, β-catenin, MC2R, pCREB, Tryptase, S100, CD34 by multiplex immunofluorescence and IHC guided RT-qPCR. Setting 11 adrenals with APA and one with micronodular hyperplasia from patients with PA were analysed. Main Outcome Measure(s) Localization of CYP11B2, CYP17A1, β-catenin, MC2R, pCREB, Tryptase, S100, CD34 in APA and aldosterone producing cell clusters (APCC). Results Immunofluorescence revealed abundant mast cells and a dense vascular network in APA, independent of mutational status. Within APA, mast cells were localized in areas expressing CYP11B2 and were rarely co-localized with nerve fibers, suggesting that their degranulation is not controlled by innervation. In these same areas, ß-catenin was activated, suggesting a zona glomerulosa cell identity. In heterogeneous APA with KCNJ5 mutations, MC2R and VEGFA expression was higher in areas expressing CYP11B2. A similar pattern was observed in APCC, with high expression of CYP11B2, activated β-catenin, and numerous mast cells. Conclusions Our results suggest that aldosterone producing structures in adrenals with APA share common molecular characteristics and cellular environment, despite different mutation status, suggesting common developmental mechanisms.

Interaction Between Wnt/β-catenin and ACTH Signaling Pathways and Paracrine Regulation in Aldosterone Producing Adenoma

Primary aldosteronism (PA) is the most frequent form of secondary arterial hypertension and is caused in the majority of cases by an aldosterone producing adenoma (APA) or bilateral adrenal hyperplasia. Different somatic mutations have been identified in APA and in other aldosterone producing structures, which can be distinct within the same adrenal, suggesting multiple mechanisms underlying APA development. Also, APA show important cellular and molecular heterogeneity which may be due to interaction of different signaling pathways involved in adrenal cortex cell differentiation and function. The aim of this study was to investigate the role of Wnt/β-catenin and ACTH signaling as well as elements of paracrine regulation of aldosterone biosynthesis and vascularization in the development of APA and aldosterone producing cell clusters (APCC) and their relationship with intratumoral heterogeneity and mutational status. We performed immunohistochemistry and multiplex immunofluorescence (CYP11B2, CYP17A1, β-catenin, MC2R, pCREB, Tryptase, S100, CD34) multispectral image analysis on 11 adrenals with APA and one with micronodular hyperplasia from patients with PA. CYP11B2 (aldosterone synthase) IHC guided RT-qPCR was performed on RNA extracted from formalin-fixed paraffin-embedded tissues in 7 adrenals. Multiplex immunofluorescence revealed high abundance of tryptase positive mast cells and a dense vascular component in APA, which were independent of the mutational status. Within APA, mast cells were mainly localized in zones expressing CYP11B2, but not in areas expressing CYP17A1, and were rarely colocalized with nerve fibers, suggesting that their activity is not controlled by innervation. In cells expressing aldosterone synthase, β-catenin was activated, i.e. shows nuclear and/or cytoplasmic staining, features suggestive of a zona glomerulosa cell identity; MC2R was found at the cell membrane. Expression of MC2R mRNA was observed at different levels in APA, similar to expression of MRAP and VEGFA; MRAP2 was not detected. Within heterogeneous APA carrying KCNJ5 mutations, both MC2R and VEGFA expression was higher in areas expressing CYP11B2. Remarkably, this pattern was maintained in APCC, where cells show high CYP11B2 expression, together with activated β-catenin, independently of the mutation status. In addition, a high number of mast cells was detected around APCC, with a reorganization of the capillaries around the CYP11B2 positive cells. Our results suggest that aldosterone producing structures in adrenals with APA share common molecular characteristics and cellular environment, despite different mutation status. Mast cells appear to be closely associated with cells expressing aldosterone synthase, both in APA and APCC, and their role in regulating aldosterone biosynthesis in the context of somatic mutations in PA remains to be established.

Extracorporeal shock wave promotes activation of anterior cruciate ligament remnant cells and their paracrine regulation of bone marrow stromal cells’ proliferation, migration, collagen synthesis, and differentiation

Aims Proliferation, migration, and differentiation of anterior cruciate ligament (ACL) remnant and surrounding cells are fundamental processes for ACL reconstruction; however, the interaction between ACL remnant and surrounding cells is unclear. We hypothesized that ACL remnant cells preserve the capability to regulate the surrounding cells’ activity, collagen gene expression, and tenogenic differentiation. Moreover, extracorporeal shock wave (ESW) would not only promote activity of ACL remnant cells, but also enhance their paracrine regulation of surrounding cells. Methods Cell viability, proliferation, migration, and expression levels of Collagen-I (COL-I) A1, transforming growth factor beta (TGF-β), and vascular endothelial growth factor (VEGF) were compared between ACL remnant cells untreated and treated with ESW (0.15 mJ/mm2, 1,000 impulses, 4 Hz). To evaluate the subsequent effects on the surrounding cells, bone marrow stromal cells (BMSCs)’ viability, proliferation, migration, and levels of Type I Collagen, Type III Collagen, and tenogenic gene ( Scx, TNC) expression were investigated using coculture system. Results ESW-treated ACL remnant cells presented higher cell viability, proliferation, migration, and increased expression of COL-I A1, TGF-β, and VEGF. BMSC proliferation and migration rate significantly increased after coculture with ACL remnant cells with and without ESW stimulation compared to the BMSCs alone group. Furthermore, ESW significantly enhanced ACL remnant cells’ capability to upregulate the collagen gene expression and tenogenic differentiation of BMSCs, without affecting cell viability, TGF-β, and VEGF expression. Conclusion ACL remnant cells modulated activity and differentiation of surrounding cells. The results indicated that ESW enhanced ACL remnant cells viability, proliferation, migration, and expression of collagen, TGF-β, VEGF, and paracrine regulation of BMSC proliferation, migration, collagen expression, and tenogenesis. Cite this article: Bone Joint Res 2020;9(8):457–467.

Author Correction: Structural basis for delta cell paracrine regulation in pancreatic islets

An amendment to this paper has been published and can be accessed via a link at the top of the paper.