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* These authors contributed equally
This paper describes an explant culture-based method for the isolation and culturing of primary, patient-specific human aortic smooth muscle cells and dermal fibroblasts. Furthermore, a novel method is presented for measuring cell contraction and subsequent analysis, which can be used to study patient-specific differences in these cells.
Smooth muscle cells (SMCs) are the predominant cell type in the aortic media. Their contractile machinery is important for the transmission of force in the aorta and regulates vasoconstriction and vasodilation. Mutations in genes encoding for the SMC contractile apparatus proteins are associated with aortic diseases, such as thoracic aortic aneurysms. Measuring SMC contraction in vitro is challenging, especially in a high-throughput manner, which is essential for screening patient material. Currently available methods are not suitable for this purpose. This paper presents a novel method based on electric cell-substrate impedance sensing (ECIS). First, an explant protocol is described to isolate patient-specific human primary SMCs from aortic biopsies and patient-specific human primary dermal fibroblasts for the study of aortic aneurysms. Next, a detailed description of a new contraction method is given to measure the contractile response of these cells, including the subsequent analysis and suggestion for comparing different groups. This method can be used to study the contraction of adherent cells in the context of translational (cardiovascular) studies and patient and drug screening studies.
Smooth muscle cells (SMCs) are the predominant cell type in the aortic medial layer, the thickest layer of the aorta. Within the wall, they are radially oriented and are involved in, among other functions, vasoconstriction and vasodilation1. The SMC contractile machinery is involved in the transmission of force in the aorta through the functional link with the extracellular matrix2. Mutations in genes encoding for the proteins of the SMC contractile apparatus, such as smooth muscle myosin heavy chain (MYH11) and smooth muscle actin (ACTA2), have been related to cases of familial thoracic aortic aneurysms, underscoring the relevance of SMC contraction in maintaining the structural and functional integrity of the aorta1,2. Furthermore, mutations in the TGFβ signaling pathway are also associated with aortic aneurysms, and their effects in aortic aneurysm pathophysiology can also be studied in skin fibroblasts3.
High-throughput measurement of SMC contraction in vitro is challenging. As SMC contractility cannot be measured in vivo in humans, in vitro assays on human cells present a feasible alternative. Moreover, abdominal aortic aneurysm (AAA) development in animal models is either chemically induced by, for example, elastase perfusion, or caused by a specific mutation. Therefore, animal data are not comparable to AAA development in humans, which mostly has a multifactorial cause, such as smoking, age, and/or atherosclerosis. In vitro SMC contractility has so far been mainly measured by traction force microscopy4,5, quantification of Fura-2 fluorescence intracellular calcium fluxes6, and collagen wrinkling assays7. While traction force microscopy provides invaluable numeric insight into the forces generated by a single cell, it is not suitable for high-throughput screening due to the complex mathematical data processing and the analysis of one cell at a time, meaning that it is very time-consuming to measure a representative number of cells per donor. Fura-2 dye and collagen wrinkling assays allow the superficial determination of contraction and do not give a precise numerical output, making them less suitable for discriminating patient-specific differences. Impaired SMC contraction in cells derived from the aorta of abdominal aortic aneurysm patients was demonstrated for the first time by optimizing a novel method for measuring SMC contraction in vitro8. This was done by repurposing the electric cell-substrate impedance sensing (ECIS) method. ECIS is a real-time, medium-throughput assay for the quantification of adherent cell behavior and contraction9,10,11 such as SMC growth and behavior in wound-healing and migration assays12,13,14. The exact method is described in the protocol section. In this optimized way, the ECIS can also be used to study fibroblast contraction due to their similar size and morphology.
The aim of this paper is to provide a stepwise description of the method for measuring SMC contraction in vitro using ECIS8 and comparing the contraction between control and patient SMCs. First, the isolation and culturing of primary SMCs from control and patient aortic biopsies is explained, which can be used for contraction measurement. Second, contraction measurements and analysis, alongside the verification of SMC marker expression, are described. Furthermore, this paper describes the method for the isolation of patient-specific dermal fibroblasts whose contraction can be measured using the same methodology. These cells can be used for patient-specific studies focused on aortic aneurysm or other cardiovascular pathologies15 or prognostic studies using a transdifferentiation protocol that allows contraction measurement prior to aneurysm surgery16.
NOTE: Aortic biopsies were obtained during open aneurysm repair in Amsterdam University Medical Centers, VU University Medical center, Amsterdam, Zaans Medisch Centrum, Zaandam and Dijklander hospital, Hoorn, the Netherlands. Control aortic tissue was obtained from the piece of the aorta attached to the renal artery harvested for kidney transplants. Only patients above the age of 18 were included, and all patients gave their informed consent to participate in the study. All material was collected in accordance with the regulations of the WMA Declaration of Helsinki and institutional guidelines of the Medical Ethical Committee of the VU Medical Center. All the experiments and experimental protocols were performed in accordance with institutional guidelines and approved by the Medical Ethical Committee of the VU Medical Center. For complete information about the control and patient cell lines used, refer to 8.
1. Isolating primary human SMCs from aortic biopsies
NOTE: Perform the following steps under a sterile tissue culture laminar flow hood. Wear gloves and use standard aseptic techniques when handling human blood and human tissue samples. SMCs are cultured in 231 Human Vascular Smooth Muscle Cell Basal Medium supplemented with 100 U/mL penicillin, 100 µg/mL streptomycin, and Smooth Muscle Growth Supplement referred to as SMC medium.
2. Isolating primary dermal fibroblasts from skin biopsies
NOTE: Perform the following steps under a sterile tissue culture laminar flow hood. Wear gloves and use standard aseptic techniques when handling human blood and human tissue samples. Fibroblasts are cultured in Basal Medium supplemented with 10% fetal bovine serum, 100 U/mL penicillin, and 100 µg/mL streptomycin, referred to as fibroblast medium.
3. Measuring contraction (example SMCs)
4. Detecting the presence of SMC specific markers
To test the reproducibility of this method, the method was first validated using control SMCs only. To determine interexperimental measurement reproducibility, two independent measurements of all included control and patient cell lines were plotted as a Bland-Altman plot (Figure 3B). The plot demonstrated that this method does not show variability outside the confidence interval, except for one outlier cell line. Furthermore, these results demonstrated that two wells seeded within the same e...
This paper presents a method to measure SMC contraction in vitro, based on the changes in impedance and surface occupation. First, the isolation, culturing, and expansion of patient-specific primary human SMCs and skin fibroblasts is described, followed by how to use them for contraction measurements.
A limitation of the study is related to obtaining the cells through an explant protocol. The cells that proliferate from the biopsy might have different properties than the original tis...
The authors have no conflicts of interest to declare.
We would like to gratefully acknowledge Tara van Merrienboer, Albert van Wijk, Jolanda van der Velden, Jan D. Blankensteijn, Lan Tran, Peter L. Hordijk, the PAREL-AAA team, and all vascular surgeons of the Amsterdam UMC, Zaans Medisch Centrum, and Dijklander hospital for providing materials and support for this study. This study is funded by the Dutch Heart Foundation, Dekkerbeurs senior clinical scientist award, project no. 2019T065.
Name | Company | Catalog Number | Comments |
96-well Array | Applied Biophysics | 96W10idf PET | Array used to measure contraction in the ECIS setup |
Custodiol | Dr. Franz Höhler Chemie GmbH | RVG 12801 | Solution used to transfer tissue in from surgery room to laboratorium |
Dimethyl sulfoxide | Sigma-Aldrich | 472301 | Solution used to dilute ionomycin |
Fetal Bovine Serum | Gibco | 26140079 | Addition to cell culture medium |
Ham's F-10 Nutrient Mix | Gibco | 11550043 | Medium used to culture skin fibroblasts |
Human Vascular Smooth Muscle Cell Basal Medium (formerly ''Medium 231'') | Gibco | M231500 | Medium used to culture smooth muscle cells |
Invitrogen countess II | Thermo Fisher Scientific | AMQAX1000 | Automated cell counter |
Ionomycin calcium salt from Streptomyces conglobatus | Sigma-Aldrich | I0634-1MG | Compound used for contraction stimulation |
NaCl 0.9% | Fresenius Kabi | B230561 | Solution used to transfer tissue in from surgery room to laboratorium |
Penicillin-Streptomycin | Gibco | 15140122 | Antibiotics used for cell culture medium |
Phospathe buffered saline | Gibco | 10010023 | Used to wash cells |
Quick-RNA Miniprep Kit | Zymo Research | R1055 | Kit used for RNA isolation |
Smooth Muscle Growth Supplement (SMGS) | Gibco | S00725 | Supplement which is added to smooth muscle cell culture medium |
SuperScript VILO cDNA Synthesis Kit | Thermo Fisher Scientific | 11754250 | Kit used for cDNA synthesis |
SYBR Green PCR Master Mix | Thermo Fisher Scientific | 4309155 | Reagent for qPCR |
Trypsin-EDTA | Gibco | 15400-054 | Used to trypsinize cells |
ZTheta | Applied Biophysics | ZTheta | ECIS instrument used for contraction measurements |
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