Structure of rosettes in the zona glomerulosa of human adrenal cortex

Abstract

Recent studies in mouse models have demonstrated that the multi-cellular rosette structure of the adrenal zona glomerulosa (ZG) is crucial for aldosterone production by ZG cells. However, the rosette structure of human ZG has remained unclear. The human adrenal cortex undergoes remodeling during aging, and one surprising change is the occurrence of aldosterone-producing cell clusters (APCCs). It is intriguing to know whether APCCs form a rosette structure like normal ZG cells. In this study, we investigated the rosette structure of ZG in human adrenal with and without APCCs, as well as the structure of APCCs. We found that glomeruli in human adrenal are enclosed by a laminin subunit β1 (lamb1)-rich basement membrane. In slices without APCCs, each glomerulus contains an average of 11 ± 1 cells. In slices with APCCs, each glomerulus in normal ZG contains around 10 ± 1 cells, while each glomerulus in APCCs has significantly more cells (average of 22 ± 1). Similar to what was observed in mice, cells in normal ZG or in APCCs of human adrenal formed rosettes through β-catenin- and F-actin-rich adherens junctions. The cells in APCCs form larger rosettes through enhanced adherens junctions. This study provides, for the first time, a detailed characterization of the rosette structure of human adrenal ZG and shows that APCCs are not an unstructured cluster of ZG cells. This suggests that the multi-cellular rosette structure may also be necessary for aldosterone production in APCCs.

Keywords: adherens junction; adrenal zona glomerulosa; aldosterone-producing cell clusters; rosette structure.

FIGURE 1

Normal ZG cell clusters and APCCs are enclosed by lamb1‐rich basement membranes. (a) Representative immunofluorescence images showing Laminin β1(Lamb1) expression in normal ZG and APCCs. Lamb1 (red) and nuclei (DAPI, blue) for normal adrenal slices. Lamb1 (red), CYP11B2 (green), and nuclei (DAPI, blue) for adrenal slices with APCCs. (b) Statistical analysis of the lamb‐1‐enwrapped areas. N stands for the number of counted areas. ****, p < 0.0001.

FIGURE 2

Human ZG cells within glomeruli form multicellular rosettes. (a) Laminin β1 (Lamb1, red) outlines individual glomeruli. β‐catenin (green) marks individual ZG cells within glomerulus. Circles show a representative rosette and arrows point to the center of the rosette. (b) Top: Confocal z‐stack (step size 2 μm) images of the rosette in (a), showing β‐catenin (green), laminin b1 (red), and nuclei (DAPI, blue). Bottom: Tracing of ZG cells (numbered 1–12) forming the rosette shown in the top panel. Arrows point to the rosette center. (c) Representative immunofluorescence images showing the expression of β‐catenin (red) and CYP11B2 (green) in APCCs, and glomerulus adjacent to APCCs (left). Each glomerulus in APCCs consists of more cells than that in normal ZG and ZG adjacent to APCCs. N indicates the number of counted glomerulus (right). Control: adrenal slices without APCCs. ****, p < 0.0001.

FIGURE 3

F‐Actin‐rich adherens junctions are abundant in human adrenal zona glomerulosa. (a) Representative examples of immunofluorescence images showing the expression of F‐Actin (red) in normal glomerulus, APCCs, and glomerulus adjacent to APCCs. Arrows point to the F‐Actin punctae. (b) Each glomerulus in APCCs has more F‐Actin punctae than that in normal ZG and ZG adjacent to APCCs. N indicates the number of counted glomerulus. Control: Adrenal slices without APCCs. *, p < 0.05; **, p < 0.01.