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Engineering functional 3-dimensional patient-derived endocrine organoids for broad multiplatform applications

Open AccessPublished:November 15, 2022DOI:https://doi.org/10.1016/j.surg.2022.09.027

      Abstract

      Background

      Recent advancements in 3-dimensional patient-derived organoid models have revolutionized the field of cancer biology. There is an urgent need for development of endocrine tumor organoid models for medullary thyroid carcinoma, adrenocortical carcinoma, papillary thyroid carcinoma, and a spectrum of benign hyperfunctioning parathyroid and adrenal neoplasms. We aimed to engineer functionally intact 3-dimensional endocrine patient-derived organoids to expand the in vitro and translational applications for the advancement of endocrine research.

      Methods

      Using our recently developed fine needle aspiration–based methodology, we established patient-derived 3-dimensional endocrine organoid models using prospectively collected human papillary thyroid carcinoma (n = 6), medullary thyroid carcinoma (n = 3), adrenocortical carcinoma (n = 3), and parathyroid (n = 5). and adrenal (n = 5) neoplasms. Multiplatform analyses of endocrine patient-derived organoids and applications in oncoimmunology, near-infrared autofluorescence, and radiosensitization studies under 3-dimensional in vitro conditions were performed.

      Results

      We have successfully modeled and analyzed the complex endocrine microenvironment for a spectrum of endocrine neoplasms in 3-dimensional culture. The endocrine patient-derived organoids recapitulated complex tumor microenvironment of endocrine neoplasms morphologically and functionally and maintained cytokine production and near-infrared autofluorescence properties.

      Conclusion

      Our novel engineered endocrine patient-derived organoid models of thyroid, parathyroid and adrenal neoplasms represent an exciting and elegant alternative to current limited 2-dimensional systems and afford future broad multiplatform in vitro and translational applications, including in endocrine oncoimmunology.

      Introduction

      There is an urgent need for the development and use of endocrine tumor organoid platforms to model several endocrine diseases, including malignancy. Rapid advancement in developing various 3-dimensional (3D) patient-derived organoid (PDO) cancer models has elucidated the vast biomedical applications of these invaluable multicellular platforms and significantly advanced translational studies, while offering new avenues for personalized medical applications, including stem cell biology, organogenesis, and various human pathologies. These advances span the generation of breast, liver, and cancer stem cells; lacrimal duct organoids; clustered regularly interspaced short-palindromic repeat (CRISPR)–based organoid genetic manipulation; single-cell sequencing; and xenotransplantation.
      • Boj S.F.
      • Hwang C.I.
      • Baker L.A.
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      Model organoids provide new research opportunities for ductal pancreatic cancer.
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      Exploring the human lacrimal gland using organoids and single-cell sequencing.
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      Promises and challenges of organoid-guided precision medicine.
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      Application of human liver organoids as a patient-derived primary model for HBV infection and related hepatocellular carcinoma.
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      Long-term culture, genetic manipulation and xenotransplantation of human normal and breast cancer organoids.
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      The generation of organoids for studying Wnt signaling.
      • Drost J.
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      Who is in the driver's seat: tracing cancer genes using CRISPR-barcoding.
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      Evaluating CRISPR-based prime editing for cancer modeling and CFTR repair in organoids.
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      Patient-derived organoids model cervical tissue dynamics and viral oncogenesis in cervical cancer.
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      Medium-throughput drug- and radiotherapy screening assay using patient-derived organoids.
      Historically, endocrine origin cells have been more challenging to grow in 2D culture conditions. Several potential contributing factors have hampered the development of endocrine 3D organoid models, likely due to the terminal differentiation of the endocrine cells, hormone-secreting profile, and inability to replicate exact conditions required to maintain physiologic feedback loops in culture. The first endocrine organoid-based disease modeling of papillary thyroid carcinoma (PTC) in vitro was reported by the investigators in this group, spearheaded by Weisss et al,
      • Vilgelm A.E.
      • Bergdorf K.
      • Wolf M.
      • et al.
      Fine-needle aspiration-based patient-derived cancer organoids.
      thus recapitulating the complex multicellular 3D tumor microenvironment (TME) of PTC, the most common endocrine malignancy and the most common type of thyroid cancer. However, we still lack endocrine organoid models for rare endocrine malignancies, such as medullary thyroid carcinoma (MTC) and adrenocortical carcinoma (ACC), where we stand to gain the most benefit by exploring various therapeutic applications. Furthermore, the development of organoid models for adrenal and parathyroid hyperfunctioning neoplasms can offer indispensable platforms for targeted therapy and define organ physiology in the intact 3D models.
      Thyroid and parathyroid tissue near-infrared autofluorescence (NIRAF) has been demonstrated since our institution’s discovery of parathyroid fluorescence in 2008. Parathyroid NIRAF discovery rapidly spawned a wide range of technological advancements in the development of image and probe-based detection tools currently employed in operating rooms worldwide.
      • Mannoh E.A.
      • Parker L.B.
      • Thomas G.
      • Solorzano C.C.
      • Mahadevan-Jansen A.
      Development of an imaging device for label-free parathyroid gland identification and vascularity assessment.
      • Mannoh E.A.
      • Thomas G.
      • Baregamian N.
      • Rohde S.L.
      • Solorzano C.C.
      • Mahadevan-Jansen A.
      Assessing intraoperative laser speckle contrast imaging of parathyroid glands in relation to total thyroidectomy patient outcomes.
      • Mannoh E.A.
      • Thomas G.
      • Solorzano C.C.
      • Mahadevan-Jansen A.
      Intraoperative assessment of parathyroid viability using laser speckle contrast imaging.
      • McWade M.A.
      • Paras C.
      • White L.M.
      • Phay J.E.
      • Mahadevan-Jansen A.
      • Broome J.T.
      A novel optical approach to intraoperative detection of parathyroid glands.
      • McWade M.A.
      • Paras C.
      • White L.M.
      • et al.
      Label-free intraoperative parathyroid localization with near-infrared autofluorescence imaging.
      • McWade M.A.
      • Thomas G.
      • Nguyen J.Q.
      • Sanders M.E.
      • Solorzano C.C.
      • Mahadevan-Jansen A.
      Enhancing parathyroid gland visualization using a near infrared fluorescence-based overlay imaging system.
      • Solorzano C.C.
      • Thomas G.
      • Baregamian N.
      • Mahadevan-Jansen A.
      Detecting the near infrared autofluorescence of the human parathyroid: hype or opportunity?.
      • Thomas G.
      • McWade M.A.
      • Nguyen J.Q.
      • et al.
      Innovative surgical guidance for label-free real-time parathyroid identification.
      • Thomas G.
      • McWade M.A.
      • Paras C.
      • et al.
      Developing a clinical prototype to guide surgeons for intraoperative label-free identification of parathyroid glands in real time.
      • Thomas G.
      • Solorzano C.C.
      • Baregamian N.
      • et al.
      Comparing intraoperative parathyroid identification based on surgeon experience versus near infrared autofluorescence detection—a surgeon-blinded multi-centric study.
      Clinically, we have observed heterogeneity and differential spectrum of NIRAF in parathyroid and thyroid glands; however, the physiologic and structural significance of this heterogeneity remains unknown, and the fluorophore discovery has not yet been made. Moreover, no previous studies have been performed to date to study NIRAF in endocrine organoids.
      The application of cancer organoid models as promising preclinical tumor models for drug development and immune response modulation has rendered organoid platforms indispensable for precision oncoimmunology and tumor radiosensitization. Autologous immune cell cocultures and nonautologous immune cells, including examining the critical role of the tumor-infiltrating T lymphocytes (TILs) in TME, can be scaled for oncoimmunologic drug development applications; however, this has not been explored in endocrine tumors using endocrine organoid platforms. Thus, our group aimed to engineer functionally intact 3D models of thyroid, parathyroid, and adrenal neoplasms to expand in vitro and translational applications for the rapid advancement of endocrine research using state-of-the-art 3D culture technologies and to advance the understanding of endocrine disease mechanisms.

      Methods

      Human endocrine tissue acquisition

      Human endocrine tissues were prospectively collected for the endocrine neoplasia biorepository (ENB) with institutional review board approval. Fresh resected human PTC (n = 6), MTC (n = 3), ACC (n = 3), parathyroid adenomas (n = 5), and adrenal (n = 5) neoplasms were obtained in the operating room at the time of resection. Under sterile intraoperative conditions, tumors were biopsied ex vivo using a sterile fine needle aspiration (FNA)–based technique to establish patient-derived 3D endocrine organoid models in the 3D semisolid culture conditions previously developed, optimized, and described by our group.
      • Vilgelm A.E.
      • Bergdorf K.
      • Wolf M.
      • et al.
      Fine-needle aspiration-based patient-derived cancer organoids.
      ,
      • Phifer C.J.
      • Bergdorf K.N.
      • Bechard M.E.
      • et al.
      Obtaining patient-derived cancer organoid cultures via fine-needle aspiration.
      ,
      • Bergdorf K.
      • Phifer C.
      • Bharti V.
      • et al.
      High-throughput drug screening of fine-needle aspiration-derived cancer organoids.
      The patient endocrine tumor unstained slides underwent hematoxylin-eosin (H&E) staining, immunohistochemical (IHC) analysis for endocrine markers, and imaging.

      3D endocrine organoid culture and imaging

      Endocrine cells isolated from tissues were suspended in 50-mL conical tube with warmed Dulbecco's Modified Eagle Medium (DMEM) media and transported to the laboratory. The cells were centrifuged (1,200 rpm, 5 minutes, at 22°C), the media was carefully aspirated, and the cells were resuspended in complete organoid media, prepared according to our previously published protocols,
      • Vilgelm A.E.
      • Bergdorf K.
      • Wolf M.
      • et al.
      Fine-needle aspiration-based patient-derived cancer organoids.
      ,
      • Phifer C.J.
      • Bergdorf K.N.
      • Bechard M.E.
      • et al.
      Obtaining patient-derived cancer organoid cultures via fine-needle aspiration.
      ,
      • Bergdorf K.
      • Phifer C.
      • Bharti V.
      • et al.
      High-throughput drug screening of fine-needle aspiration-derived cancer organoids.
      and plated in a 24-well ultralow attachment plate. Each well was replenished with 200 μL per well of fresh complete organoid media supplemented with a solubilized basement membrane matrix (5% Matrigel; Thermo Fisher Scientific International, Inc, Pittsburgh, PA), an additional 2% fetal bovine serum (dFBS, Life Technologies, Rockville, MD) in a dropwise fashion weekly. The cells were passaged 3 to 4 times following organoid formation, and then cryopreserved.
      • Vilgelm A.E.
      • Bergdorf K.
      • Wolf M.
      • et al.
      Fine-needle aspiration-based patient-derived cancer organoids.
      ,
      • Phifer C.J.
      • Bergdorf K.N.
      • Bechard M.E.
      • et al.
      Obtaining patient-derived cancer organoid cultures via fine-needle aspiration.
      ,
      • Bergdorf K.
      • Phifer C.
      • Bharti V.
      • et al.
      High-throughput drug screening of fine-needle aspiration-derived cancer organoids.
      The live endocrine organoids (parathyroid, adrenal, and thyroid) were grown in 3D culture, as previously described, and were imaged using color brightfield microscopy (Cytation 5; BioTek, Winooski, VT) during early (1–2 weeks) and late (>6 weeks) 3D culture growth phases, and live imaging was obtained using color brightfield microscopy. Endocrine PDOs were also grown in 75% Matrigel disk form to test the feasibility of using endocrine PDOs in NIRAF, irradiation, and oncoimmunologic models, and live imaging was obtained using color brightfield microscopy; immunofluorescent (IF), NIRAF, and IHC images were obtained and are described below in detail.

      Transmission electron microscopy of endocrine organoid cells

      Endocrine organoids were grown in 3D culture on a thin layer of Matrigel and fixed with supplies provided by the transmission electron microscopy (TEM) core staff: 2% paraformaldehyde, 2% glutaraldehyde for 1 hour at room temperature followed by 24 hours at 4°C. After fixation, the organoids were microdissected out of the dishes and postfixed in 1% tannic acid, followed by 1% osmium tetroxide, and en bloc stained in 1% uranyl acetate. Organoids were dehydrated in a graded ethanol series followed by gradual infiltration with Quetol 651(Thermo Fisher Scientific International)–based Spurr‘s resin (Sigma-Aldrich, Corp, St. Louis, MO) using propylene oxide as a transition solvent. The Spurr‘s resin was polymerized at 60ºC for 48 hours and sectioned at a nominal thickness of 70 nm. The sections were stained with 2% uranyl acetate and lead citrate. The TEM was performed using an FEI T12 operating at 100 kV using an AMT NanoSprint 5 complementary metal-oxide semiconductor (CMOS) camera. Single images were acquired using AMT acquisition software operating in drift correction mode. Large montages were acquired using Serial EM. Montages and were processed in the IMOD software suite. FIJI (https://imagej.net/software/fiji/) was used to adjust image brightness/contrast. The Enhance Local Contrast function in FIJI was used to normalize the contrast across montaged datasets to improve low magnification contrast but not for the higher magnification insets.

      H&E and IHC staining of endocrine organoids

      The organoids were centrifuged at 1,200 rpm for 10 minutes. Media was aspirated, and the organoids were resuspended in 10% neutral buffered formalin for 30 minutes. The organoids were then centrifuged at 1,200 rpm for 10 minutes. The neutral buffered formalin was aspirated, and the organoids were resuspended in 70% alcohol for 15 minutes 3 times. The organoids were centrifuged at 1,200 rpm for 10 minutes between each alcohol wash. After the final alcohol wash, cells were resuspended in 1.5% heated UltraPure Agarose (Invitrogen, Waltham, MA/ThermoFisher) and transferred to a cryomold for 30 minutes. The agarose-organoid block was processed and embedded in paraffin using a 2-hour processing run. Organoid H&E and IHC staining was performed by the Translational Pathology Shared Resource (TPSR) core staff using validated primary antibodies (TPSR core antibodies were used for thyroid transcription factor-1 [TTF-1], neuron-specific enolase (NSE), calcitonin [Ctn], Ki67, and nuclear factor erythroid 2-related factor 2 [Nrf2] [Abcam, Cambridge, UK]). An experienced pathologist reviewed slides.

      IF endocrine organoid imaging

      Parathyroid organoids were plated in 8-well chambered slides using 75% Matrigel gel and maintained in complete organoid culture overnight. Media was aspirated, and organoids were washed and fixed with methanol (100%) and permeabilized with Triton X-100 (0.5%; Dow Chemical Company, Midland, MI) in phosphate-buffered saline (PBS). The organoids were blocked with 5% bovine serum albumin (BSA) in PBS and incubated with calcium-sensing receptor (CaSR) antibody (Sigma-Aldrich, Corp) overnight. The organoids were washed and incubated with a secondary Alexa-conjugated antibody (1:250) antibody (Invitrogen/ThermoFisher). Fluorescent images were captured using fluorescent filters with a fluorescence microscope (Keyence, Itasca, IL) with 3D analytic capabilities and a broad wavelength range (ultraviolet [UV] to infrared [IR]).

      Endocrine organoid NIRAF

      Endocrine organoid NIRAF imaging was performed in live organoids in 3D culture and fixed organoids on chamber slides using Keyence with 3D analytic capabilities and a broad wavelength range (UV to IR). Specifically, 2 filters were employed for NIRAF imaging—indocyanine green (ICG) (ET775/50x, ET875/55m, Chroma, Bellows Falls, VT) and Cy5.5 (ET650/45x, ET720/60m, Chroma). Organoids were first imaged using brightfield microscopy for 3D localization, followed by dye-free autofluorescence imaging obtained with ICG filter.

      Endocrine organoid hormone enzyme-linked immunosorbent assays

      Endocrine organoids were grown in 5% Matrigel semisolid condition. Supernatants were collected for assessment of parathyroid, adrenal, and MTC hormonal production. Enzyme-linked immunosorbent assay (ELISA) kits were used to measure parathyroid hormone (PTH) levels secreted by newly formed parathyroid organoids, cortisol secretion by the cortisol-secreting ACC and benign adrenal neoplasms organoids, and Ctn secretion by the MTC organoids (PTH kit [Abcam]; Ctn kit [Sigma-Aldrich, Corp]; and cortisol kit [Arbor Assays, Ann Arbor, MI]). All tests were performed in triplicates.
      For the parathyroid organoid calcium challenge experiment, formed primary hyperparathyroidism (PHPT) PDOs previously grown in complete organoid media with physiologically relevant calcium content (1.8 mmol/L) were transferred into calcium-free organoid culture media and incubated for 3 hours. Supernatant was collected for PTH ELISA assessment. Parathyroid organoids were then challenged with calcium-containing organoid media (10 mmol/L) for 1 hour, and collected supernatant was analyzed for PTH levels in response to calcium supplementation.

      Isolation of tumor-infiltrating T lymphocytes from human papillary thyroid carcinoma tumors

      Fresh PTC tumor disks (1–2 mm thick) were obtained from the resected thyroid gland specimens and transported in a sterile vial to the laboratory on ice. The TIL isolation from tumor tissues was performed using DNAse (Sigma-Aldrich, Corp) to shear the DNA and collagenase (Sigma-Aldrich, Corp) to break down tissue collagen. Cells were treated with ACK lysis solution (Lonza, Basel, Switzerland), suspended in 2-mL RPMI medium and counted. The TIL cells were centrifuged at 300 rpm for 10 min. The CD3+ T-cell isolation and purification were performed using a human CD3+ T-cell isolation kit (Miltenyi Biotech, Bergisch Gladbach, Germany). The supernatant was removed, and TILs were resuspended in 100 μL of buffer (PBS with 0.5% BSA and 2 mmol/L ethylenediaminetetraacetic acid (EDTA), filtered through a 0.22-μm filter to sterilize), and a CD3 microbeads kit (Miltenyi Biotec) was used as per manufacturer’s protocol. Collected CD3+ TIL suspension was used for cell count and cryopreservation.

      Tumor-infiltrating lymphocyte–papillary thyroid carcinoma organoid coculture model

      Freshly isolated and cryopreserved CD3+ TILs were thawed, spun, and resuspended in complete organoid media first. The PTC organoid disks from 6 different patients were plated in 6-well plates, and TILs were directly added to the wells with organoids and complete organoid media. The TIL-PTC organoids were incubated for 72 hours and media aspirated and centrifuged, and supernatants were analyzed for CD3+ TIL cytokine response to coculture with PTC organoids. Human T-cell cytokine panel kit (LEGENDplex, BioLegend, San Diego, CA) was used to detect cytokine response according to the manufacturer’s instructions.

      Endocrine organoid irradiation model

      PTC organoids grown in 3D culture were irradiated with 2 Gy (cesium-137 at 2 Gy/min) daily for 3 days (total dose of 6 Gy) at the Radiation Oncology Research Irradiator Shared Resource core. Irradiated PTC organoids were collected, formalin-fixed, and stained for the Nrf2 expression by the TPSR core, per the previously described protocol above.

      Statistical Analyses

      Statistical analyses were performed using GraphPad Prism 9 Software (San Diego, CA). Throughout the manuscript, statistical significance is designated as: ns (p ≥ 0.05),* (P < .05),** (P < .01), and ***(P < .001).

      Results

      Endocrine organoids morphologically recapitulate complex endocrine tumor microenvironment in 3D culture

      We successfully established several novel 3D endocrine PDO models of PTC, MTC, ACC, and parathyroid and adrenal neoplasms in vitro. All isolated endocrine tumor cells exhibited rapid organoid formation and growth during the early stage (1–3 weeks) in 3D culture. All endocrine organoids underwent successful culture passages at least 2 to 3 times before cryopreservation and biobanking. Endocrine organoids recapitulated their respective complex TMEs morphologically with robust expression of endocrine organ-specific markers, such as TTF-1 and NSE (Figure 1). The PTC organoids, when left in culture >6 weeks (late phase), developed a fibroblast track and a broad-based core tethering the tumor organoid to the bottom of the culture well (Figure 2). Interestingly, the parathyroid, benign adrenal, and MTC organoids, in contrast to PTC and ACC organoids, required longer culture times (1–2 weeks more) for organoid formation.
      Figure thumbnail gr1
      Figure 1Models of 3-dimensional (3D) endocrine patient-derived organoid (PDO). Top row (left to right), human PTC tumor H&E stain, PTC PDO in 3D semisolid Matrigel culture, IHC staining of the same organoid with TTF-1. Second row (left to right), human ACC tumor H&E stain, ACC PDO in 3-D semisolid Matrigel culture demonstrates cell with membrane protrusions (“budding”), the same organoid with H&E and IHC co-stains, NSE and Ki67. Third row (left to right), human MTC tumor H&E demonstrates abundant amyloid (amorphous pink material), tumor matched MTC PDO, and abundant amyloid present in 3D semisolid Matrigel culture, and the same organoid with H&E and Ctn IHC co-stain. Bottom row (left to right), human parathyroid adenoma (PHPT) H&E stain shows chief (purple), oxyphil (pink), and adipose (white) cells, PHPT PDO in 3D semisolid Matrigel culture, same organoid H&E stain shows predominantly chief cell enriched PHPT PDO. All tissue H&E images were taken at 20× magnification, organoids at 40× magnification. ACC, adrenocortical carcinoma; Ctn, calcitonin; H&E, hematoxylin-eosin; IHC, immunohistochemical; MTC, medullary thyroid carcinoma; NSE, neuron-specific enolase; PDO, patient-derived organoid; PHPT, primary hyperparathyroidism; PTC, papillary thyroid carcinoma; TTF-1, thyroid transcription factor-1.
      Figure thumbnail gr2
      Figure 2PTC organoids in 3D early- and late-stage in vitro culture. A. Spherical PTC organoid formed during first 2 weeks in 3D culture and imaged live using Brightfield microscopy. B. PTC organoid formed with fibroblast “corona”. C. Large PTC organoid with few membrane protrusions (“budding”). D-E. In the late 3D culture phase, PTC organoid is now fully formed and anchored to the bottom of the plate by migrating fibroblasts, the same PTC organoid at 40× magnification. F. The long narrow stalk anchors the PTC organoid to the fibroblasts at the bottom of the plate. Images A-D were obtained at 20× magnification, whereas E-F are imaged at 40× magnification. PTC, papillary thyroid carcinoma; 3D, three dimensional.
      The TEM imaging of endocrine organoid cells provided a detailed compartment-level overview of cellular structures consistent with endocrine cells—abundant secretory granules, pronounced Golgi apparatus, and parallel endoplasmic reticular (ER) structures of hormone-secreting endocrine cells (Figure 3). Specific findings in MTC organoid cells included multinucleated unusual trilobed nuclear structures in parafollicular C cells. The TEM of a PTC PDO cell at higher magnification showed extensive cytoskeletal features and numerous small membrane protrusions. The TEM of an ACC PDO cell showed abundant secretory granules (Figure 3). The TEM of a parathyroid PDO cell derived from a parathyroid adenoma at higher magnification of the cell body showed membrane-bound granular structures and a higher density of elongated mitochondria.
      Figure thumbnail gr3
      Figure 3Morphologic features of 3D endocrine PDOs on transmission electron microscopy (TEM). TEM of a PTC PDO cell at low magnification overview (top left corner box) showing the general size and morphology. Higher magnification of the cell body showing extensive cytoskeletal features (black arrows) and numerous small membrane protrusions (blue arrows). TEM of an ACC PDO cell demonstrates abundant secretory granules. TEM of the MTC PDO cell at a low magnification overview of the organoid structure shows a large cell with an unusual trilobed nuclear structure; many cells exhibit parallel ER structures, elongated mitochondria (blue arrow), and lysosomes (orange arrow). TEM of a parathyroid PDO cell at low magnification showing the general size and morphology. Higher magnification of the cell body showing membrane-bound granular structures and elongated mitochondria (blue arrow). Scale bars for low magnification images are 5 μm and 1 μm for higher magnification. ACC, adrenocortical carcinoma; MTC, medullary thyroid carcinoma; PDO, patient-derived organoid; PTC, papillary thyroid carcinoma; TEM, transmission electron microscopy; TTF-1, thyroid transcription factor-1.

      Endocrine organoids maintain hormonal functionality in 3D culture

      Parathyroid PDOs, Ctn-secreting MTC, and cortisol-secreting ACC and benign adrenal neoplasms PDOs were assessed for hormonal functionality in 3D culture (Figure 4). Parathyroid organoids maintained intact CaSR expression (Figure 4, A), a regulator of PTH secretion by parathyroid cells. Parathyroid tissue lysates were used as a positive control for parathyroid PDO PTH production assessment (Figure 4, B). Parathyroid organoids revealed functional hormonal responsiveness to fluctuating calcium concentrations in media. When the parathyroid PDOs were maintained in calcium-free media first, then supplemented with calcium, we first observed significantly higher PTH secretion levels in calcium-free media compared with the previously observed average PTH levels (Figure 4, C), and PTH levels down-trended with calcium supplementation ≤1 hour of administration. Modest suppression in PTH secretion after calcium supplementation may be explained by possible slow PTH degradation in 3D culture within a short period, and, in the absence of physiologic clearance. Parathyroid PDOs demonstrated sustained PTH secretion into the culture media over several passages (Figure 4, D).
      Figure thumbnail gr4
      Figure 4Functional assessment of endocrine PDOs in 3D culture in vitro. A. A parathyroid PDO expressing CaSR (green) using immunofluorescent staining; nuclei are counterstained with DAPI (blue, 20×). B. PTH secretion was measured in thyroid and parathyroid tissue lysates, and parathyroid PDO using a PTH ELISA assay. C. PTH secretion was measured in parathyroid PDOs incubated in calcium-free organoid media, then supplemented by calcium using ELISA assay, repeated in 3 separate patient samples. D. PTH secretion by parathyroid PDOs (n=3) in 3D culture over time (3 passages) was detected using an ELISA assay. E. Ctn-secreting MTC PDOs (n=2) were kept in 3D culture for 4 passages and calcitonin levels were measured with an ELISA assay. F. Cortisol-secreting adrenal PDOs (n=3) were kept in 3D culture for 4 passages, and cortisol levels were measured with an ELISA assay. CaSR, calcium-sensing receptor; Ctn, calcitonin; ELISA, enzyme-linked immunosorbent assay; MTC, medullary thyroid carcinoma; PDO, patient-derived organoid; PTH, parathyroid hormone.
      Functional assessment of MTC PDOs was performed using ELISA and compared with normal thyroid tissue lysate. The Ctn secretion by MTC organoids was observed in 3D media supernatant and Ctn secretion peaked by passage 2 (Figure 4, E); however, by the third and fourth passages, the MTC PDO Ctn secretion significantly dropped off and stopped. Notably, MTC PDOs are slow growing in 3D culture, and the time between passages is typically much longer than in PTC, parathyroid, or ACC organoids, which may account for Ctn secretion pattern differences.
      Functional assessment of cortisol-secreting adrenal PDOs–ACC (patient 1) and benign adrenal neoplasms (patients 2 and 3) was performed with ELISA (Figure 4, F). Adrenal PDO cortisol production was maintained by the organoids in 3D culture during the first 2 passages; however, by the third and fourth passages, the cortisol secretion tapered off significantly or stopped completely. Collectively, we observed robust hormone secretion by the endocrine PDOs in the early phases of 3D culture; however, as they are maintained in 3D culture over a longer timeframe, we observed differential hormonal functionality between endocrine PDOs. Notably, parathyroid PDOs displayed sustained secretion of PTH under late culture conditions in contrast to adrenal and MTC PDOs tapered hormone secretion patterns.

      Preserved NIRAF in 3D endocrine organoids

      We were the first to report preserved NIRAF in parathyroid, thyroid, and adrenal PDOs (Figures 5, A and B). We maintained PTC PDOs in 3D culture >6 weeks to allow for the formation of a fibroblast core that tethered the tumor organoid to a fibroblast disk at the bottom of the well with the intention to examine label-free autofluorescence in endocrine and nonendocrine cells in the multicellular organoid structure. Live PTC PDO in the 3D culture was imaged concurrently with brightfield and NIR microscopy, and, when images were overlayed, we observed no NIRAF in fibroblasts and enhanced NIRAF in PTC PDO (emission >680 nm). Similarly, the ACC PDO was imaged live in 3D culture. The brightfield and NIR microscopy overlay images revealed intense NIRAF in ACC PDO.
      Figure thumbnail gr5
      Figure 5Multiplatform applications of 3D endocrine organoids in tumor autofluorescence, oncoimmune coculture and irradiation models in vitro. A. PTC PDO NIRAF measured using Cy5.5 filter (emission >680 nm) (top row) is depicted in late-stage 3D culture (black) with migrated fibroblasts (clear disk of cells) anchoring at the bottom of the well in 3D culture with NIRAF overlay detected in cancer cells only. ACC PDO NIRAF (bottom row) is depicted in 3-D culture. B. Parathyroid PDO is imaged with an ICG filter (emission >800 nm) to detect NIRAF (yellow); nuclei are counterstained with DAPI (blue), 20× magnification. C. PTC PDOs are directly cocultured with isolated CD3+ TILs in 3D culture. D. CD3+ TILs: PTC PDO co-culture and TILs alone culture supernatants (n=4) were analyzed for cytokines response, INF-γ and TNF-α (±SEM, ***P < .001). E. PTC PDOs are irradiated with 2 Gy daily for 3 days (XRT), and IHC stained for Nrf2 (brown, 20× magnification). ACC, adrenocortical carcinoma; IHC, immunohistochemical; ICG, indocyanine green; INF- γ, interferon gamma; NIRAF, near-infrared autofluorescence; Nrf2, nuclear factor erythroid 2-related factor; PDO, patient-derived organoid; PTC, papillary thyroid carcinoma; TIL, tumor-infiltrating lymphocyte; TNF-α, tumor necrosis factor alpha; XRT, irradiation.
      The parathyroid PDOs were imaged using NIR imaging and IF staining, with NIRAF obtained using ICG filter (NIRAF emission >800 nm), and fixed organoid nuclei were counterstained with DAPI (Figure 5, B). We observed heterogeneous clusters of NIRAF throughout the organoids, with varying degrees of NIRAF intensity. In agreement with prior studies by Mahadevan-Jansen et al
      • McWade M.A.
      • Paras C.
      • White L.M.
      • Phay J.E.
      • Mahadevan-Jansen A.
      • Broome J.T.
      A novel optical approach to intraoperative detection of parathyroid glands.
      • McWade M.A.
      • Paras C.
      • White L.M.
      • et al.
      Label-free intraoperative parathyroid localization with near-infrared autofluorescence imaging.
      • McWade M.A.
      • Thomas G.
      • Nguyen J.Q.
      • Sanders M.E.
      • Solorzano C.C.
      • Mahadevan-Jansen A.
      Enhancing parathyroid gland visualization using a near infrared fluorescence-based overlay imaging system.
      that reported NIRAF in parathyroid tissues, our finding supported preserved NIRAF in parathyroid organoids in 3D culture. The results also confirmed that nonendocrine origin fibroblast cells do not possess NIRAF and can be discriminated in tissues in situ and in organoids in vitro.

      Endocrine organoid and immune coculture model

      We assessed the application of the endocrine PDOs in endocrine oncoimmunology by measuring alterations in CD3+ TIL cytokine levels, interferon (INF)-γ and tumor necrosis factor (TNF)-α, when directly cocultured with tumor-matched PTC PDOs for 72 hours (Figure 5, C). Cytokine responses were measured. They showed a significant increase in INF-γ and TNF-α secretion compared to CD3+ TILs alone, suggesting that PTC PDO and CD3+ TIL in-culture interactions have an impact on cytokine production and elicit enhanced CD3+ TIL cytokine responses against tumor cells in organoids (Figure 5, D). Our findings reported the feasibility of endocrine PDO-TIL coculture model applicability for future endocrine oncoimmunological studies under 3-D culture conditions.

      Endocrine organoid irradiation model

      Radiosensitization is commonly used in vitro and in vivo to study tumor cell responses and resistance to treatment. To establish the feasibility for the organoid irradiation model in vitro under 3D culture conditions, we irradiated PTC-PDOs for 3 days and observed for induction of the key regulator of antioxidant cellular response, Nrf2. We observed increased expression levels of cytoplasmic and nuclear Nrf2 within PTC PDOs (Figure 5, E), thus proving the feasibility of application of endocrine PDOs in the in vitro irradiation model for future studies.

      Discussion

      Our group successfully engineered several functionally intact endocrine patient tumor-derived 3D organoid models of thyroid, parathyroid, and adrenal neoplasms. We were the first to characterize the structural and functional fidelity of the spectrum of the 3D endocrine organoid models of PTC, MTC, ACC, and parathyroid and adrenal neoplasms; their in-culture growth and hormone secretion patterns; autofluorescence properties; and applications in oncoimmunology and radiosensitization studies under 3D in vitro conditions.
      Structural characterization of endocrine organoid models was greatly enhanced by electron microscopy, which confirmed the robust presence of secretory granules, altered cytoskeleton, and several unique features characteristic of endocrine origin cells. We observed a differential functional window of hormone secretion between various endocrine tumor organoids, which should be considered during experimental design when using 3D endocrine organoid models. Although MTC organoids remain in culture the longest, compared with the other types of endocrine organoids, largely due to their relatively slow growth, mirroring well-described 2D in vitro behavior the Ctn secretion by the cells in MTC organoid is sustained for the first 2 passages over a longer period. Therefore, future experimental designs for the MTC organoids should be planned accordingly. Dynamic PTH secretion and rapid response to calcium level fluctuations by the parathyroid organoid cells in 3D in vitro conditions establish parathyroid PDO as a valuable model for future organoid-based studies. Importantly, we observed preserved CaSR expression in parathyroid organoid cells and its functionality by regulating PTH secretion into the 3D culture media in response to calcium fluctuations. This finding provided a critical window into future studies aiming at therapeutically targeting CaSR for either the treatment of permanent hypoparathyroidism or persistent hyperparathyroidism in benign and malignant parathyroid disease.
      Using endocrine organoid models for endocrine oncoimmunology applications provides an invaluable preclinical route for modeling the complexities of endocrine tumors in vitro for drug development and immune response modulation. Furthermore, insight into the hormonal secretory behavior of the endocrine organoids may influence potential therapeutic windows and endocrine hormone modulatory effect on immune cells. Additionally, the usefulness of endocrine organoid platforms in autologous immune cell cocultures and nonautologous immune cells can be scaled for oncoimmunology drug development applications.
      Radioactive iodine ablation is one of the therapeutic modalities used to treat thyroid cancer and typically follows surgical resection. Recurrent and radioactive iodine–resistant thyroid tumors present a therapeutic challenge; therefore, radiosensitization, alone or in combination with new drug therapies or oncoimmunologic modalities, can be employed using endocrine organoid models of thyroid cancer to measure endocrine tumor responses. The benefit of 3D endocrine tumor organoids for oncoimmunologic and radiosensitization applications is the enhanced by the clinical relevance of multicellular endocrine tumor organoids closely emulating endocrine TME under 3D culture conditions and testing tumor responses that are untenable under 2D conditions.
      Despite numerous advantages of organoid applications, we recognize several challenges and limitations of using engineered 3D endocrine organoid model platforms. In our experience, the 3D culture growth of endocrine cells can be challenging in some cases and not all endocrine tumor cells will grow readily to form organoids in 3D. Variability in endocrine organoid size and number, hormone secretion profile, limited availability, ability to elicit immunologic responses, or drug responses in 3D culture can present a challenge that uniquely mimics patient tumor heterogeneity. Thus, we repeated experiments at least 3 times to validate the observed trends.
      Organoid imaging presents a unique challenge due to the high risk of organoid loss in processing steps, small size, a limited number of organoids, and 3D structure requiring use of a 75% Matrigel disk format to secure organoids to the slides. The background fluorescence of Matrigel is a limiting factor for the NIRAF and IF studies. Consideration should be given to isolated tumor cell labeling before plating for 3D organoid formation and growth.
      Future genetic manipulations within endocrine organoids using molecular technologies, such as the lentiviral expression system and clustered regularly interspaced short-palindromic repeat/Cas9, will enable endocrine disease modeling and targeted gene therapy. As the organoid technology rapidly expands, our understanding of its vast applications, such as in stem cell biology, organogenesis, and various human pathologies; the organoid-based disease modeling with precision; 3D architecture; and spatial arrangement of endocrine multicellular TME (Figure 6), will thrust endocrine biomedical research forward.
      Figure thumbnail gr6
      Figure 6Engineered 3-dimensional endocrine organoids for future broad multiplatform applications. 3D, three dimensional; NIRAF, near-infrared autofluorescence; PDO, patient-derived organoid; PDX, patient-derived xenograft.
      In conclusion, we successfully engineered a spectrum of patient-derived 3D endocrine organoid models of thyroid cancers, ACC, and parathyroid and adrenal neoplasms. We launched a series of initial in vitro multiplatform analyses to pave the way for the broader translational applications of endocrine organoids.

      Funding/Support

      This work was supported by the Burroughs Wellcome Fund Vanderbilt SCRIPS faculty scholar award (Dr Baregamian).

      Conflict of interest/Disclosure

      The authors have no conflicts of interests or disclosures to report.

      Acknowledgements

      The authors would like to recognize the contribution of the specimen donors as well as the research entities who have made these analyses possible, including Cindy Lowe and Karen Thompson (TPSR core) and the Radiation Oncology Research Irradiator Shared Resource and Vanderbilt Cell Imaging Shared Resource (supported by National Institutes of Health grants CA68485 , DK20593 , DK58404 , DK59637 , and EY08126 ) cores.

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