Flow Cytometry-Based Quantification and Analysis of Myocardial B-Cells

Summary

Here we report a protocol for the quantification and differentiation of myocardial B-lymphocytes based on their location in the intravascular or endothelial space using flow cytometry.

Abstract

A growing body of evidence shows that B-lymphocytes play an important role in the context of myocardial physiology and myocardial adaptation to injury. However, the literature reports contrasting data on the prevalence of myocardial B-cells. B-cells have been reported to be both among the most prevalent immune cells in the rodent heart or to be present, but at a markedly lower prevalence than myeloid cells, or to be quite rare. Similarly, several groups have described that the number of myocardial B-cells increases after acute ischemic myocardial injury, but one group reported no changes in the number of B-cells of the injured myocardium. Implementation of a shared, reproducible method to assess the prevalence of myocardial B-cells is critical to harmonize observations from different research groups and thus promote the advancement of the study of B-cell myocardial interactions. Based on our experience, the seemingly contrasting observations reported in the literature likely stem from the fact that murine myocardial B-cells are mostly intravascular and connected to the microvascular endothelium. Therefore, the number of B-cells recovered from a murine heart is exquisitely sensitive to the perfusion conditions used to clean the organ and to the method of digestion used. Here we report an optimized protocol that accounts for these two critical variables in a specific way. This protocol empowers reproducible, flow cytometry-based analysis of the number of murine myocardial B-cells and allows researchers to distinguish extravascular vs. intravascular myocardial B-cells.

Introduction

B-lymphocytes are highly specialized immune cells that play an important role in both adaptive and innate immune responses¹. There are two main populations of B-cells: a smaller population of B1 cells that are mostly produced during embryonic life, and a preponderant population of B2 cells that are produced in adult life in the bone marrow¹. After maturing in the bone marrow, B-cells migrate to primary and secondary lymphoid organs. From there they continuously recirculate between lymphoid organs traveling through blood vessels and lymphatic vessels². B-cells express specific antibodies on their s....

Protocol

All experiments described in this manuscript were performed with the approval of the IACUC at Johns Hopkins University School of Medicine.

1. Preparations

1. Prepare the FACS Buffer, as described in Table 1.
2. Ensure there is enough CO₂ to euthanize the animals.
3. Prepare the dissection space (place the bench pad and place the tape and dissection tools nearby).
4. Label the 15 mL tubes, put 3 mL of HBSS with calcium a.......

Discussion

A growing body of evidence indicates that B-cells play an important role in the context of myocardial physiology and myocardial remodeling/adaptation to injury^{7,8,9,10,11,12,13,36}. Flow cytometry is an excellent tool to study immune cell populations in any .......

Materials

Name	Company	Catalog Number	Comments
Alexa Fluor 700 anti-mouse/human CD11b Antibody	101222	BioLegend	100 µg 200 µL
(CellTreat 29481) Cell Strainer, 40 µm, Blue	QBIAP303	Southern Labware
0.5 mL Natural Microcentrifuge Tube	1605-0000	SealRite, USA Scientific
0.9% Sodium Chloride Injection, USP	114-055-101	Quality Biological	0.90%
1.5 mL Natural Microcentrifuge Tube	1615-5500	SealRite, USA Scientific
10 µL Graduated TipOne Filter Tips	11213810	USA Scientific
1000 µL Graduated TipOne Filter Tips	11267810	USA Scientific
15 mL Centrifuge Tube, Plug Seal Cap, Polypropylene, RNase-/DNase-free	430052	Corning
1-Way Stop Valve, Polycarbonate	SVPT951	ECT Manufacturing
2,2,2-Tribromoethanol	T48402	Sigma-Aldrich
200 µL Graduated TipOne Filter Tips	11208810	USA Scientific
3-Way Stop Valve, Polycarbonate	SVPT953	ECT Manufacturing
5 mL Polystyrene Round-Bottom Tube, 12 x 75 mm style	352054	Falcon, a Corning Brand
50 mL Centrifuge Tube, Plug Seal Cap, Polypropylene, RNase-/DNase-free	430290	Corning
ACK (Ammonium-Chloride-Potassium) Lysing Buffer	118-156-101	Quality Biological	Osmolality: 290 + or -5% mOsm/Kg H20
Adapter 4x50ml, for 250 mL rectangular bucket in Rotor A-4-63	5810759005	Eppendorf
Adapter for 15 mL Centrifuge Tubes, 9 Tubes per Adapter, Conical Bottom for use with Rotor Model A-4-62	22638289	Eppendorf
Adapter for 15 round-bottom tubes 2.6 – 7 mL, for 250 mL rectangular bucket in Rotor A-4-62	22638246	Eppendorf
Aluminum Foil 12 in x 75' Roll .0007	UPC 109153	Reynolds Wrap
Anesthesia Induction Chamber - Mouse	RWD-AICMV-100	Conduct Science
BD Luer Slip Tip Syringe with attached needle 25 G x 5/8 in., sterile, single use, 1 mL	309626	BD Becton, Dickinson and Company
Brandzig Ultra-Fine Insulin Syringes 29G 1cc 1/2" 100-Pack	CMD 2613	Brandzig
Brilliant Violet 421 anti-mouse CD19 Antibody	115537	BioLegend	50 µg/mL
CAPS for Flow Tubes w/strainer mesh 35 µm, Dual position for 12 x 75 mm tubes, sterile	T9009	Southern Labware
Carbon Dioxide USP E CGA 940	CD USPE	AirGas USA
Cole-Parmer Essentials Low-Form Beaker, Glass, 500 mL	UX-34502-46	Cole-Parmer
Collagenase 2	LS004176	Sigma-Aldrich
Connector brass chrome plated 1/4" female NPT x 1/4" barb	Y992611-AG	AirGas USA
Cytek Aurora Flow Cytometer		Cytek Biosciences
Diss 1080 Nipple 1/4 BARB CP	M-08-12	AirGas USA
DNase I - 40,000 U	D4527	Sigma-Aldrich
Easypet 3 - Electronic Pipette Controller	4430000018	Eppendorf
Electronic Balance, AX223/E	30100606	Ohaus Corp.
Eppendorf 5810R centrifuge	5810R	Eppendorf
Eppendorf Research plus 1-channel variable pipettes		Eppendorf
FlowJo 10.8.1		BD Becton, Dickinson and Company
GLACIERbrand, triple density Ice Pan (IPAN-3100)	Z740287	Heathrow Scientific
HBSS (1x) - Ca2+ [+] Mg2+ [+]	14025076	gibco	1x
Hyaluronidase	H3506	Sigma-Aldrich
Kelly Hemostats, Straight	13018-14	Fine Science Tools
Luer Slip Syringe sterile, single use, 20 mL	302831	BD Becton, Dickinson and Company
M1 Adj. Reg 0-100 PSI/CGA940	M1-940-PG	AirGas USA
McKesson Underpads, Moderate	4033-CS150	McKesson
Navigator Multi-Purpose Portable Balance	NV2201	Ohaus Corp.
PBS pH 7.4 (1X) Ca2+ [-] Mg2+ [-]	10010023	gibco	1x
PE anti-mouse/human CD45R/B220 Antibody	103208	BioLegend	200 µg/mL
PerCP/Cyanine5.5 anti-mouse CD45 Antibody	103132	BioLegend	100 µg 500 uL
Petri dish, Stackable 35 mm x 10 mm Sterile Polystyrene	FB0875711YZ	Fisher Scientific
Pkgd: Diss 1080 Nut/CO2/CO2-02	M08-1	AirGas USA
Powerful 6 Watt LED Dual Goose-Neck Illuminator	LED-6W	AmScope
PrecisionGlide Needle 25 G x 5/8 (0.5 mm x 16 mm)	305122	BD Becton, Dickinson and Company
Purified Rat Anti-Mouse CD16/CD32 (Mouse BD Fc Block) Clone 2.4G2 (RUO)	553141	BD Becton, Dickinson and Company Biosciences	0.5 mg/mL
R 4.1.1		The R Foundation
Razor Blades	9501250000	Accutec Blades Inc
Regulator analytical two stage 0-25 psi delivery CGA320 3500 psi inlet	Y12244A320-AG	AirGas USA
Rotor A-4-62, incl. 4 x 250 mL rectangular buckets	Rotor A-4-62	Eppendorf
Serological pipette, plugged, 10 mL, sterile, non-pyrogenic/endotoxin-free, non-cytotoxic, 1 piece(s)/blister	86.1254.001	Sarstedt AG & Co KG
Sigma label tape	L8394	Sigma-Aldrich
SpectroFlo 3.0.0		Cytek Biosciences
Spex VapLock Luer Fitting, PP, Straight, Male Luer Lock x 1/8" Hose Barb; 1/EA	MTLL230-6005	Spex
Std Wall Lab Tubing, Size S2, Excelon, 1/8" ID x 3/16" OD x 1/32" Wall x 50' Long	CG-730-003	Excelon Laboratory
Syringe PP/PE without needle, 3 mL	Z683566	Millipore Sigma
Syringe pump	55-1199 (95-240)	Harvard Apparatus
Thomas 3-Channel Alarm Timer TM10500	9371W13	Thomas Scientific
Tube Rack, 12 positions, 6 for 5.0 mL and 15 mL tubes and 6 for 25 mL and 50 mL tubes, polypropylene, numbered positions, autoclavable	30119835	Eppendorf
Tube Rack, 12 positions, for 5.0 mL and 15 mL tubes, polypropylene, numbered positions, autoclavable	30119827	Eppendorf
TYGON R-3603 Laboratory Tubing, I.D. × O.D. 1/4 in. × 3/8 in.	T8913 (Millipore Sigma)	Tygon, Saint-Gobain
Vortex-Genie 2	SI-0236	Scientific Industries, Inc.
VWR Dissecting Forceps with Guide Pin with Curved Tips	89259-946	Avantor, by VWR
VWR Dissecting Scissors, Sharp Tip, 4½"	82027-578	Avantor, by VWR
VWR Incubating Orbital Shaker, Model 3500I	12620-946	Avantor, by VWR
Zombie Aqua Fixable Viability Kit	423102	BioLegend