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All experiments were conducted in accordance with protocols approved by the Boston Children’s Hospital Institutional Animal Care and Use Committee (IACUC) under approval number 00002611. A complete list of all materials used in this protocol, including reagents, consumables, and equipment, is provided in the Table of Materials, along with the corresponding manufacturers and catalog numbers to ensure reproducibility.
Primary cultures of mouse adrenal zona glomerulosa and zona fasciculata cells
The methods used to establish primary cultures of adult male mouse wild-type (Mus musculus, C57BL/6) adrenocortical cells in this study were adapted from a procedure originally developed for Sprague-Dawley rats28. To confirm the segregation and identity of zona glomerulosa and zona fasciculata cell populations, a lineage-tracing model was employed using Cyp11b2tm1.1(cre)Brlt/+ (also known as-Cre) mice1,2,3,4 and Gt(ROSA)26Sortm4(ACTB-tdTomato-EGFP) Luo/J (also known as ROSAmT/mG) mice29.
Preparation before the procedure
Materials
Two sets of forceps and scissors for superficial incisions and another set for incision of the abdominal cavity (Supplementary Figure 1A). Warmed the culture medium and PBS (37 °C). Prepared 2 dishes (P60) with DMEM/F-12. Prepared 3 dishes (P60) with warmed PBS to wash the glands in sequence (bath 1, 2, and 3) (Supplementary Figures 1B, 1–3), and 1 dish to keep the adrenal in solution (Supplementary Figures 1B, 4). Prepared 2 dishes (P60) with sterile filter paper on the surface (Supplementary Figures 1C, 1–2). Prepared 2 P60 dishes with 500 µL of digestion solution and labeled them for the glomerulosa (zG) or the fasciculata (zF) (Supplementary Figures 1D, zG, zF). Prepared 2 tubes, labeled zG and zF, and added 4.5 mL of digestion solution.
Solutions
To make the digestion solution, collagenase type I (final concentration 4 mg/mL) and DNase I (final concentration 0.04 mg/mL) were dissolved in 5 mL of pure DMEM/F-12 medium. Filtered the solution into a 50 mL tube using a syringe and a 0.22 µM filter. The digestion solution should be prepared fresh each time.
Animals
To obtain primary cultures enriched for mouse adrenal zona glomerulosa and zona fasciculata cells, use 10–15 young adult male mice, approximately 6–7 weeks of age. Females have slightly larger adrenal glands than males, and either sex can be used with this protocol. However, in this study, only males were used to avoid potential interference from the X-zone present in young females, ensuring accurate zonal separation. Mice were euthanized by CO₂ inhalation in accordance with institutional animal care guidelines. Death was confirmed by the absence of respiration and lack of reflex response. Adrenal glands were dissected immediately, within 3–5 min after confirmation of death, to preserve tissue viability.
Position and exposure of the abdomen
The mouse was placed in a dorsal decubitus position on a sterile flat surface (Figure 1A). The animal’s fur was disinfected with 70% alcohol. Forceps and scissors were used for the cutaneous incisions, and the second set for the abdominal cavity incision. An initial incision in the inguinal region of the abdomen was made, extending laterally towards the thorax on both sides to expose the peritoneum (Figure 1B). The skin was carefully retracted, followed by the abdominal musculature, to expose the abdominal cavity (Figure 1C). The initial incision should be superficial to avoid damage to the internal organs. Advance to the muscle layer with a cautious incision, then expose the abdominal cavity. Avoid rupturing blood vessels, as bleeding can make it difficult to locate the adrenal glands and delay collection. Change surgical instruments to minimize microbial contamination.
Identification and collection of the left adrenal gland
The left adrenal gland is located medially and superior to the left kidney in the retroperitoneum, with an oval shape and pink coloration, surrounded by white adipose tissue (Figures 1D–G). While carefully displacing adjacent organs with blunt forceps to improve visualization, use scissors to remove most of the adipose tissue using short, controlled cuts, isolating the adrenal gland. Avoid directly grasping the adrenal gland to prevent damage to its capsule. The gland was placed immediately after isolation in a P60 culture dish with 10 mL of pre-warmed DMEM/F-12 at 37 °C (Figure 1F).
Identification and collection of the right adrenal gland
The right adrenal gland is located laterally and superior to the right kidney in the retroperitoneum, with an oval shape and pink coloration (Figures 1E–H). Identifying this adrenal gland may be more challenging due to its proximity to other organs, such as the liver and ascending colon, as well as nearby blood vessels. While carefully displacing adjacent organs with blunt forceps to improve visualization, use scissors to remove most of the adipose tissue using short, controlled cuts, isolating the adrenal gland, while taking care not to damage the capsule. The gland was placed immediately after isolation in a P60 culture dish with 10 mL of pre-warmed DMEM/F-12 at 37 °C. The adrenals are combined in the same dish (Figure 1F). During the procedure, it is essential to handle the major blood vessels in the area with care to avoid accidental cuts, which can cause bleeding and complicate the collection process. The main vessels to be cautious of include the renal veins and renal arteries. Collected the adrenal gland with some adherent adipose tissue. This facilitates the handling of the gland and protects against capsule damage and contamination (Figure 1I).
Work in a sterile laminar flow hood
Before transferring the glands to the laminar flow hood, the dish was wiped clean with 70% alcohol. The adrenals were washed with PBS three times at room temperature (25 °C) (in dishes 1, 2, and 3 and collected in dish 4) (Supplementary Figure 1B). The filter paper helps with fat adhesion and ensures better results. During the preparation of multiple glands, the separated tissues should be maintained in pre-warmed DMEM to preserve viability. The adrenal gland was grasped by the adherent adipose tissue (Figures 1I–J), and the fat was carefully dissected on the filter paper (Supplementary Figure 1C, dish 1), using fine forceps and controlled movements to avoid damaging the capsule. The expected result is a smooth, intact gland free of excess adipose and connective tissue, as shown in Figure 1K. The adrenal glands were transferred carefully to fresh filter paper (Supplementary Figure 1C, dish 2) to facilitate precise microdissection. The capsule was gently pinched with fine forceps, and using the scalpel blade, a radial incision was made in the gland without completely transecting the tissue.
The inner contents of the cortex were gently exposed by expelling them outward through the incision through the application of slight mechanical pressure with the forceps. The capsule and the zG remained connected to the tip of the forceps, while the inner expelled glandular material corresponded to the zF and medulla. Enzymatic digestion should be initiated only after all glands have been processed (Figure 1L), due to mechanical separation of the outer and inner zones.
Digestion
Two tubes were labeled as OF (Outer Fraction: capsule and zG) or IF (Inner Fraction: zF and medulla) (Figure 1M). A total of 4.5 mL of pre-warmed digestion solution (37 °C) was added, and the OF and IF were transferred to the appropriate tubes. The samples were incubated at 37 °C in a humidified incubator with 5% CO₂ for 30 min, and the tubes were gently swirled every 10 min, by manually inverting them 2–3 times to ensure uniform exposure to the enzyme solution. The time required for digestion may vary depending on the quality, activity, and storage conditions of the collagenase. After 30 min, the tissue was dissociated by pipetting up and down 40 times with slow, controlled strokes, using a 5 mL serological pipette to generate a single cell slurry. After dissociation of the tissue, ideally, no visible fragments should remain, and the medium should appear cloudy. If fragments are still present, an additional 15-min digestion may be considered.
Washing and plating
Following the digestion, the cells were washed by adding 45 mL of DMEM/F-12 to remove residual enzyme (Figure 1 M). Samples were centrifuged at 150 × g for 12 min at room temperature (25 °C). Following centrifugation, a small and compact pellet with a slightly pinkish to pale yellow appearance is expected, while the supernatant should remain clear and free of visible particulates. The supernatant was carefully removed and discarded, taking care not to disturb the pellet. The pellet was resuspended in pre-warmed (37 °C) culture medium according to the final volume required for plating (see below). An optimal plating density of approximately 70% was maintained to ensure culture viability and vigor. The cell number was estimated using a Neubauer counting chamber prior to plating, and the number of cells seeded was adjusted according to the culture dish area to achieve the desired confluency. Plate the zG-enriched outer fraction (OF) cells at a density of approximately one animal per well (typically yielding ~1.5–2.5 × 104 cells) and the zF-enriched inner fraction (IF) cells at ~0.63 animals per well (typically yielding ~2.5–4.0 × 104 cells) in a 48-well plate.
Cell culture maintenance
Cells were cultured in the Culture Medium described above and maintained under standard conditions in a humidified incubator at 37 °C with 5% CO₂. After 24 h of culture, the medium was replaced to remove debris and any residual blood cells. This step promotes optimal growth. The plate was carefully aspirated, and fresh pre-warmed (37 °C) medium was added. Wait at least 48 h before assessing the cells in functional experiments. It’s recommended to wait three days before performing functional experiments to ensure the cultures are well-established. Extended culture beyond this period may require trypsinization and passaging, which can lead to cell selection and loss of primary culture characteristics.
Data analysis and supporting procedures
Preparation of primary adrenal cell cultures
Primary cultures of whole adrenal glands were established following the same procedures for tissue collection, digestion, washing, and plating, and were used as standard controls for molecular and functional assays.
Gene expression analysis
To purify total RNA from OF and IF cells, the cultured cells were homogenized in TRIReagent using the RNA kit, according to the manufacturer’s protocol. RNA integrity and concentration were evaluated by using spectrometry. Further processing of total RNA involved reverse transcription into cDNA using the high-capacity cDNA reverse transcription kit. Gene expression analysis was performed by real-time quantitative PCR (qPCR) using the thermocycler. Technical duplicates were used to control for variability. The TaqMan Universal PCR Master Mix and mouse TaqMan primers were used (Table 1). A cycle threshold (CT) value was selected within the linear amplification range for each sample run in duplicate. It was normalized by endogenous control genes β-actin and ribosomal protein 18S (Rps18). The relative expression levels were calculated using the 2–ΔΔCt method30. The data from three different experiments are presented as mean ± standard deviation (SD). We performed three independent experiments.
Stimulation of aldosterone and corticosterone secretion in primary ZG and ZF cultures
Primary cultures of zona glomerulosa (ZG) and zona fasciculata (ZF) cells were established and maintained at 37 °C in a humidified atmosphere containing 5% CO₂. Approximately 5 × 104 cells were plated per well in a 48-well plate using complete growth medium. After four days of continuous culture, basal secretion measurements reflected cumulative hormone production over this time period. For stimulation assays, the medium was aspirated, and the cells were washed once with phosphate-buffered saline (PBS) to remove residual factors. Subsequently, 200 µL of fresh medium was added to each well, and the following assays represent acute stimulated secretion within a defined time window. For aldosterone stimulation assays, the culture medium was supplemented with angiotensin II (Ang II, 10 nM), potassium (K+), as potassium chloride (KCl, 10 mM), and ACTH, (10 nM). Sodium chloride (NaCl, 10 mM) was used as the vehicle control. For corticosterone stimulation assays, the same procedures were followed, but the medium was supplemented with ACTH (10 nM), forskolin (10 µM), or NaCl (10 mM) as a vehicle control. After 6 h of incubation at 37 °C and 5% CO₂, the culture supernatants were collected and stored at −80 °C for subsequent hormone quantification, as described previously31. The remaining adherent cells were lysed for protein extraction, and hormone levels were normalized to the total protein content of the corresponding lysate.
Protein extraction and normalization of aldosterone and corticosterone measurements
Protein extraction was performed using RIPA lysis and extraction buffer, supplemented with 1x halt protease inhibitor cocktail. Cells were resuspended by pipetting up and down 15 times using a P200 pipette tip and subsequently sonicated using a probe sonicator. Protein concentration was determined with the BCA protein assay kit according to the manufacturer’s instructions.
Aldosterone measurement by radioimmunoassay (RIA)
The concentration of aldosterone in cell culture supernatants was determined by following the manufacturer’s protocol. In brief, 50 µL of supernatant and 150 µL of 1% BSA in PBS, together with 500 µL of the aldosterone radioactive tracer, were added to aldosterone antibody-coated tubes. After mixing, the tubes were incubated at room temperature (25 °C) for 18 h. Then, the incubation mixture was decanted, and the radioactivity in the tubes was counted using a Cobra II auto-gamma counter31. Aldosterone levels were normalized to total protein, as previously described.
Corticosterone measurement
Corticosterone concentrations in cell culture supernatants were measured using a competitive enzyme-linked immunosorbent assay (ELISA) kit specific for mouse and rat corticosterone, following the manufacturer’s protocol. Corticosterone levels were normalized to total protein, as previously described32.
Immunostaining
Immunofluorescence was performed on both paraffin-embedded adrenal sections and cultured cells grown on pre-treated glass coverslips coated with Poly-L-lysine. For all samples, blocking was performed with 5% normal goat serum (NGS) in PBS, and nuclei were counterstained with DAPI (4′, 6-diamidino-2-phenylindole, 1:1000). Slides and coverslips were washed three times for 5 min each with 0.1% Tween-20 in PBS between incubation steps. After staining, samples were mounted with Antifade Mountant and stored in the dark until imaging. Tissue sections: Adrenal paraffin sections were deparaffinized in xylene, then rinsed through a graded ethanol series (100%, 95%, 70%), and finally rinsed in PBS. Antigen retrieval was performed in Tris-EDTA buffer (10 mM Tris base, 1 mM EDTA, 0.05% Tween-20, pH 9.0) by heating at 95 °C for 20 min. After cooling to room temperature, sections were washed in PBS and blocked with 5% NGS in PBS for 1 h. Sections were incubated overnight at 4 °C with the following primary antibodies diluted 1:100 in 5% NGS in PBS: mouse anti-Dab2, chicken anti-GFP, and rabbit anti-RFP. The following secondary antibodies were used (1:300): Alexa Fluor 594 goat anti-mouse IgG, Alexa Fluor 594 goat anti-chicken IgY, and Alexa Fluor 647 goat anti-rabbit IgG.
Cultured cells: Immunofluorescence on coverslips was performed four days after plating. Cells were fixed with pre-warmed 4% paraformaldehyde (PFA) at 37 °C for 15 min and washed three times in PBS. Blocking was performed using 5% NGS in PBS for 1 h at room temperature. Coverslips were incubated overnight at 4 °C with mouse anti-Dab2 (1:100 in 5% NGS/PBS), followed by Alexa Fluor 488 goat anti-mouse (1:500).
Image acquisition: Brightfield and fluorescence images (mGFP and mTomato) of cultured cells were acquired using a microscope system. The mGFP fluorescence was captured using a filter set for green fluorescence (excitation: 470 nM, emission: 525 nM), and mTomato fluorescence was captured using a filter set for red fluorescence (excitation: 585 nM, emission: 624 nM).
Software and statistical analysis
Visual summaries, schematic diagrams, and figures were created using Adobe Illustrator 2023 (Adobe Inc., https://www.adobe.com/products/illustrator.html) and BioRender (https://www.biorender.com), accessed in May 2025. Data were analyzed using GraphPad Prism version 10.0. Available at: https://www.graphpad.com. All experiments were performed at least in triplicate and independently repeated to ensure reproducibility of the results. For comparisons between two groups, Student’s t-test (paired or unpaired, as appropriate) was used. For comparisons involving three or more groups, analysis of variance (ANOVA) followed by the appropriate post hoc test was performed to identify significant differences between groups. Results are presented as mean ± SD. A p-value of less than 0.05 was considered statistically significant.