Name: culture of brain capillary pericytes for cytosolic calcium measurements and calcium imaging studies
Uploaded: 2020-05-27T15:00:00
Description: Watch this Scientific Journal Video about Culture of Brain Capillary Pericytes for Cytosolic Calcium Measurements and Calcium Imaging Studies at JoVE.com

The authors wish to acknowledge funding from the Lundbeck Foundation Research initiative on Brain Barriers and Drug Delivery (RIBBDD) and Simon Hougners Family Foundation.

1. Preparation of buffers and solutions for cell culturing
<ol>
	<li>Prepare collagen stock solution by dissolving 5 mg of collagen IV from human placenta in 50 mL of PBS overnight at 4 &#176;C. Aliquot the stock solution into 5 mL portions and store at -20 &#176;C.</li>
	<li>Prepare fibronectin stock solution by dissolving 5 mg of fibronectin in 5 mL of sterile water overnight. Store the fibronectin stocks in aliquots of 500 &#181;L at -20 &#176;C. When thawing, add PBS to a final volume of 50 mL to prepare the work s...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bovine+retinal+microvascular+pericytes:+isolation,+propagation,+and+identification.">Bovine retinal microvascular pericytes: isolation, propagation, and identification.</a> Methods In Molecular Medicine. 46, 247-263 (2001).</li><li>Nees, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation,+bulk+cultivation,+and+characterization+of+coronary+microvascular+pericytes:+the+second+most+frequent+myocardial+cell+type+in+vitro.">Isolation, bulk cultivation, and characterization of coronary microvascular pericytes: the second most frequent myocardial cell type in vitro.</a> American Journal of Physiology-Heart and Circulatory Physiology. 302 (1), H69-H84 (2012).</li><li>Armulik, A., Abramsson, A., Betsholtz, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial/pericyte+interactions.">Endothelial/pericyte interactions.</a> Circulation Research. 97 (6), 512-523 (2005).</li><li>Helms, H. C., Brodin, B., Milner, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+in+Molecular+Biology.">Methods in Molecular Biology.</a> Cerebral Angiogenesis: Methods and Protocols. 1135, 365-382 (2014).</li><li>Abbracchio, M. P., Burnstock, G., Verkhratsky, A., Zimmermann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purinergic+signalling+in+the+nervous+system:+an+overview.">Purinergic signalling in the nervous system: an overview.</a> Trends in Neurosciences. 32 (1), 19-29 (2009).</li><li>Cai, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimulation-induced+rises+in+cerebral+blood+flow+and+local+capillary+vasoconstriction+depend+on+conducted+vascular+responses+in+brain+capillaries.">Stimulation-induced rises in cerebral blood flow and local capillary vasoconstriction depend on conducted vascular responses in brain capillaries.</a> PNAS. , (2018).</li><li>Tigges, U., Welser-Alves, J. V., Boroujerdi, A., Milner, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+and+simple+method+for+culturing+pericytes+from+mouse+brain.">A novel and simple method for culturing pericytes from mouse brain.</a> Microvascular Research. 84 (1), 74-80 (2012).</li><li>Maier, C. L., Shepherd, B. R., Yi, T., Pober, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Explant+Outgrowth,+Propagation+and+Characterization+of+Human+Pericytes.">Explant Outgrowth, Propagation and Characterization of Human Pericytes.</a> Microcirculation. 17 (5), 367-380 (2010).</li><li>Orlidge, A., Damore, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+specific+effects+of+glycosaminoglycans+on+the+attachment+and+proliferation+of+vascular+wall+components.">Cell specific effects of glycosaminoglycans on the attachment and proliferation of vascular wall components.</a> Microvascular Research. 31 (1), 41-53 (1986).</li><li>Rhinehart, K., Zhang, Z., Pallone, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ca2++signaling+and+membrane+potential+in+descending+vasa+recta+pericytes+and+endothelia.">Ca2+ signaling and membrane potential in descending vasa recta pericytes and endothelia.</a> American Journal of Physiology-Renal Physiology. 283, F852-F860 (2002).</li><li>Bintig, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purine+receptors+and+Ca2++signalling+in+the+human+blood-brain+barrier+endothelial+cell+line+hCMEC/D3.">Purine receptors and Ca2+ signalling in the human blood-brain barrier endothelial cell line hCMEC/D3.</a> Purinergic Signalling. 8 (1), 71-80 (2012).</li><li>Neuhaus, A. A., Couch, Y., Sutherland, B. A., Buchan, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+method+to+study+pericyte+contractility+and+responses+to+ischaemia+in+vitro+using+electrical+impedance.">Novel method to study pericyte contractility and responses to ischaemia in vitro using electrical impedance.</a> Journal of Cerebral Blood Flow and Metabolism. 37 (6), 2013-2024 (2017).</li><li>Kamouchi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+influx+pathways+in+rat+CNS+pericytes.">Calcium influx pathways in rat CNS pericytes.</a> Molecular Brain Research. 126 (2), 114-120 (2004).</li><li>Das, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ATP+Causes+Retinal+Pericytes+to+Contract+In+vitro.">ATP Causes Retinal Pericytes to Contract In vitro.</a> Experimental Eye Research. 46, 349-362 (1988).</li></ol>

In this study, we have presented a method to isolate primary pericytes from bovine brains. The described protocol allows culture of this otherwise rather inaccessible cell type. The subsequently obtained cell culture was a nearly homogenous population of pericytes, with little or no contamination with endothelial cells&#160;and glial cells based on cell morphology and protein expression12. Furthermore, we demonstrated a simple and straightforward method to load the pericytes with calcium dyes for ...

Brain capillary pericytes, together with endothelial cells and astrocytes, constitute the NVU1,2,3. The endothelial cells, which form the structural basis of the capillaries, form long cylindrical tubes with a diameter of 5-8 &#181;m. The endothelial cells are sporadically covered with pericytes and surrounded by protrusions from astrocytes; the astrocyte endfeet.
The blood-brain barrier (BBB), situated at the brain capillaries, is the main site for exchange of nutrients, gases and waste products between the brain and the blood. The BBB also protects the brain from endogenous and exogenous neurotoxins and serves as a barrier for the delivery of a large number of drug compounds. The barrier function is a focus area, as well as an obstacle, for drug companies developing central nervous system (CNS) medicines. This has spurred a large interest in investigating the cells of the NVU in culture4. Brain astrocytes and endothelial cells have been cultured and characterized in a number of studies, whereas the studies and protocols for pericyte culture are sparse.
Previously published protocols have described generation of brain capillary pericyte cultures to some degree, using a range of different approaches such as immunopanning5, high- and low-glucose media6, fluorescent-activated cell sorting7, density gradient centrifugation8, etc. Although these methods seem sufficient to obtain cultures of pericytes, some are time consuming, cost expensive and the pericytes obtained might not be ideal due to the number of culture passages that can de-differentiate the pericytes9. Furthermore, the potential of cultured pericytes in in vitro signaling studies has been fairly unexplored until now.
The present work focuses on the generation of pericyte cultures from isolated bovine brain capillaries and the subsequent setup for measurements and imaging studies of changes in intracellular calcium, an important intracellular second messenger. We briefly describe the isolation of capillaries from cortical gray matter (for details see Helms et al.10) and the isolation and culture of pericytes in pure monoculture without contamination with endothelial or glial cells. We then provide a protocol for seeding of pericytes in 96-well plates and loading protocols for the calcium probe Fura-2 AM. Finally, we show how pericytes can be used in real-time confocal imaging in microscope culture chambers and describe the protocols for this.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>ATP</td>
			<td>Tocris</td>
			<td>3245</td>
			<td></td>
		</tr>
		<tr>
			<td>Cal-520 AM</td>
			<td>AAT Bioquest</td>
			<td>21130</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell incubator</td>
			<td>Thermo Fisher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Thermo Fisher</td>
			<td>Heraeus Multifuge 3SR+</td>
			<td>Standard large volume centrifuge for spinning down cells</td>
		</tr>
		<tr>
			<td>Collagen IV</td>
			<td>Sigma Aldrich</td>
			<td>C5533</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal laser scanning microscope</td>
			<td>Carl Zeiss</td>
			<td>Zeiss LSM 510</td>
			<td>Inverted microscope</td>
		</tr>
		<tr>
			<td>Counting chamber</td>
			<td>FastRead</td>
			<td>102</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslip cell chamber</td>
			<td>Airekacells</td>
			<td>SC15022</td>
			<td></td>
		</tr>
		<tr>
			<td>Cremophor EL</td>
			<td>Sigma Aldrich</td>
			<td>C5135</td>
			<td>Formerly known as Kolliphor EL</td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma Aldrich</td>
			<td>471267</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagles Medium</td>
			<td>Sigma Aldrich</td>
			<td>D0819</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>PAA/GE Healthcare</td>
			<td>A15-101</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin</td>
			<td>Sigma Aldrich</td>
			<td>F1141</td>
			<td></td>
		</tr>
		<tr>
			<td>Fura-2 AM</td>
			<td>Thermo Fisher</td>
			<td>F1201</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass coverslips 22x22 mm</td>
			<td>VWR International</td>
			<td>631-0123</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS</td>
			<td>Gibco</td>
			<td>14065-049</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>Sigma Aldrich</td>
			<td>H3149</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>AppliChem Panreac</td>
			<td>A1069</td>
			<td></td>
		</tr>
		<tr>
			<td>Light microscope</td>
			<td>Olympus</td>
			<td>Olympus CK2</td>
			<td>Upright light microscope with phase contrast</td>
		</tr>
		<tr>
			<td>MEM nonessential amino acids</td>
			<td>Sigma Aldrich</td>
			<td>M7145</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate Reader</td>
			<td>BMG LabTech</td>
			<td>NOVOstar</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma Aldrich</td>
			<td>D8537</td>
			<td>Phosphate-buffered saline</td>
		</tr>
		<tr>
			<td>penicillin G sodium/streptomycin sulfate</td>
			<td>Sigma Aldrich</td>
			<td>P0781</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F127</td>
			<td>Sigma Aldrich</td>
			<td>P2443</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Sigma Aldrich</td>
			<td>T4299</td>
			<td></td>
		</tr>
		<tr>
			<td>T-75 flask</td>
			<td>Sigma Aldrich</td>
			<td>CLS3972</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>Corning incorporated</td>
			<td>3603</td>
			<td></td>
		</tr>
	</tbody>
</table>

culture of brain capillary pericytes for cytosolic calcium measurements and calcium imaging studies

Pericytes are associated with endothelial cells and astrocytic endfeet in a structure known as the neurovascular unit (NVU). Brain capillary pericyte function is not fully known. Pericytes have been suggested to be involved in capillary development, regulation of endothelial barrier tightness and trancytosis activity, regulation of capillary tone and to play crucial roles in certain brain pathologies.
Pericytes are challenging to investigate in the intact brain due to the difficulties in visualizing processes in the brain parenchyma, as well as the close proximity to the other cells of the NVU. The present protocol describes a method for isolation and culture of primary bovine brain capillary pericytes and their following usage in calcium imaging studies, where effects of agonists involved in brain signaling and pathologies can be investigated. Cortical capillary fragments are allowed to attach to the bottom of culture flasks and, after 6 days, endothelial cells and pericytes have grown out from the capillary fragments. The endothelial cells are removed by gentle trypsinization and pericytes are cultured for 5 additional days before passaging.
Isolated pericytes are seeded in 96-well culture plates and loaded with the calcium indicator dye (Fura-2 acetoxymethyl (AM)) to allow for measurements of intracellular calcium levels in a plate reader setup. Alternatively, pericytes are seeded on coverslips and mounted in cell chambers. Following loading with the calcium indicator (Cal-520 AM), calcium live-imaging can be performed using confocal microscopy at an excitation wavelength of 488 nm and emission wavelength of 510-520 nm.
The method described here has been used to obtain the first intracellular calcium measurements from primary brain capillary pericytes, demonstrating that pericytes are stimulated via ATP and are able to contract in vitro.

Bovine brain capillaries were isolated from fresh brain tissue and Figure 1 presents the capillary seeding and cellular outgrowth over days and subsequent purification&#160;of pericytes. The capillaries are fully attached to the flask at day 1 and on day 2 endothelial sprouting has become visible (Figure 1, day 2). After 4 days, the cellular outgrowth is highly distinctive (Figure 1, day 4a) and the ...

Watch this Scientific Journal Video about Culture of Brain Capillary Pericytes for Cytosolic Calcium Measurements and Calcium Imaging Studies at JoVE.com

Culture of Brain Capillary Pericytes for Cytosolic Calcium Measurements and Calcium Imaging Studies

Brain capillary pericytes are essential players in the regulation of blood-brain barrier properties and blood flow. This protocol describes how brain capillary pericytes can be isolated, cultured, characterized with respect to cell type and applied for investigations of intracellular calcium signaling with fluorescent probes.

Pericytes are associated with endothelial cells and astrocytic endfeet in a structure known as the neurovascular unit (NVU). Brain capillary pericyte ...

This is a simple and effective method for isolating and culturing primary brain pericytes for study of intercellular calcium signaling. The obtained cell culture is a nearly homogenous population of pericytes, and it's straightforward to load the pericytes for calcium imaging. The methods described here should provide other researchers in the field with strong tools for studying pericyte biology, and intracellular signaling in pericytes in vitro.Begin by thawing one vial of capillaries in a 37 degree Celsius water bath. Once the capillaries have thawed, transfer them to a centrifuge tube with 30 milliliters of DMEM comp, and centrifuge them for five minutes at 500 times G.Then, remove the medium from the tube, and re-suspend the palette in 10 milliliters of fresh DMEM comp. Transfer the suspension to a coated T-75 flask, and allow the capillaries to adhere to the bottom for four to six hours in a 37 degrees Celsius incubator supplied with 10%carbon dioxide.After the incubation, inspect the flask under a light microscope. Fractions of capillaries should now be attached to the bottom of the flask. On day four after seeding the capillaries, inspect them under the microscope to ensure that they are approximately 60 to 70%confluent.Aspirate the medium, and gently wash the cells with PBS. Add two milliliters of thawed trypsin-EDTA, and leave the flask in the incubator for one to three minutes, taking the flask out frequently, and observing cell detachment with the microscope. When the endothelial cells start to round up, gently tap the flask to detach them.When the cells have detached, stop trypsinization by adding 10 milliliters of DMEM comp to the flask. Flush the flask a few times with the medium, and aspirate the endothelial cell suspension, which can now be used for other purposes. Add 10 milliliters of DMEM comp to the flask, and check it under the light microscope to assure that the pericytes are still present and attached to the bottom.Then, put the flask back into the incubator to allow the pericyte-enriched culture to grow. To seed pericytes into coated 96-well plates, detach them as described in the text manuscript. Aspirate the medium, taking care not to disturb the cell pellet, And re-suspend the pellet in one milliliter of fresh DMEM comp.Count the cells using a counting chamber, then calculate the volume of suspension that should be added to each well to seed 10, 000 cells per well. Add the cell suspension, then add enough DMEM comp to the cells to achieve a total volume of 200 microliters per well. When ready to load the pericytes with Fura-2 AM calcium indicator dye, take the 96-well plate with the cells out of the incubator, and aspirate the medium from the wells.Wash the cells twice with assay buffer, and add 100 microliters of loading solution to each well. Wrap the plate with tinfoil to avoid photo bleaching, and incubate it for 45 minutes with 30 RPM shaking at room temperature. After the incubation, aspirate the loading buffer, and wash the cells with the assay buffer twice.Add 100 microliters of fresh to assay buffer, and leave the cells to incubate for 30 minutes. After the incubation, set the temperature of the plate reader to 37 degrees Celsius, and transfer the 96-well plate with cells to the sample plate position, then place the reagent plate with agonist at the reagent plate position. Start by measuring loading of the cells to ensure equal loading of Fura-2 AM in all wells, then perform the measurements with excitation fluorescence wavelength at 340 to 380 nanometers, and the emission wavelength at 510 nanometers.Add 50 microliters of agonist, at a speed of 150 microliters per second, from the reagent plate to each well with cells. Mount a cover slip into the cell chamber, and tighten it to avoid leaks. Add DMEM comp and the calculated volume of cell suspension into each chamber, for a final volume of 500 microliters.Incubate the cell chambers at 37 degrees Celsius and 10%carbon dioxide for six days, or until confluent. Once the cells are confluent, take the cell chambers out of the incubator, and aspirate the medium. Wash the cells twice with assay buffer, and add 500 microliters of loading buffer to each chamber, then incubate them at room temperature for 45 minutes.After the incubation, aspirate the loading buffer, and wash the cells twice with assay buffer, then add 500 microliters of fresh assay buffer to each chamber and incubate them for another 30 minutes at room temperature, to allow cleavage of the AM ester. Replace the buffer with 500 microliters of fresh assay buffer, and proceed with live imaging at a confocal microscope. Mount the cell chamber on the stage of the microscope as gently as possible to avoid disturbance of the cells.Set the excitation wavelength at 488 nanometers, emission at 515 nanometers, two minute sequential image acquisition with five second intervals, and an x, y image size of 512 by 512 pixels. Add 300 microliters of 100 millimolar ATP to the cell chamber, and initiate image acquisition. This protocol was used to purify pericytes from bovine brain capillaries.Cellular outgrowth from the seeded capillaries was imaged over the course of nine days. The capillaries were fully attached to the flask at day one, and by day two, endothelial sprouting was visible. After four days, the cellular outgrowth was distinctive, and the endothelial cells were removed via trypsinization.Remnants of the capillaries were present after the trypsinization, but disappeared from the flask in the following days. After removal of the endothelial layer, the pericytes were allowed to grow until confluency. On day nine, the pericytes reached approximately 80%confluency, and formed islands.Addition of ATP to the Fura-2 loaded pericytes resulted in an increase in cytosolic calcium levels. The response occurred immediately after addition of ATP to the pericytes, and declined slowly over the measured time period. The calcium response was also measured with real-time confocal imaging.Baseline fluorescence was measured, then ATP was added at 64 seconds, and a strong intracellular calcium response was evident. Soon after, the cytosolic calcium compartmentalized in the cells, and a reduction in cell area was visible. By 300 seconds, the cell area heavily reduced, and the fluorescence declined almost to baseline levels.This method has been used to obtain the first intracellular calcium measurements from primary brain capillary pericytes, demonstrating that pericytes are stimulated via ATP, and are able to contract in vitro.

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Calcium Imaging in Mouse Superior Colliculus

Author Spotlight: Unveiling Neural Coding and Mechanisms of Visual Processing in the Superior Colliculus 

The superior colliculus (SC), an evolutionarily conserved midbrain structure in all vertebrates, is the most sophisticated visual center before the ...