Isolation of Cardiomyocyte Nuclei from Post-mortem Tissue

Summary

Cardiac nuclei are isolated via density sedimentation and immunolabeled with antibodies against pericentriolar material 1 (PCM-1) to identify and sort cardiomyocyte nuclei by flow cytometry.

Abstract

Identification of cardiomyocyte nuclei has been challenging in tissue sections as most strategies rely only on cytoplasmic marker proteins¹. Rare events in cardiac myocytes such as proliferation and apoptosis require an accurate identification of cardiac myocyte nuclei to analyze cellular renewal in homeostasis and in pathological conditions². Here, we provide a method to isolate cardiomyocyte nuclei from post mortem tissue by density sedimentation and immunolabeling with antibodies against pericentriolar material 1 (PCM-1) and subsequent flow cytometry sorting. This strategy allows a high throughput analysis and isolation with the advantage of working equally well on fresh tissue and frozen archival material. This makes it possible to study material already collected in biobanks. This technique is applicable and tested in a wide range of species and suitable for multiple downstream applications such as carbon-14 dating³, cell-cycle analysis⁴, visualization of thymidine analogues (e.g. BrdU and IdU)⁴, transcriptome and epigenetic analysis.

Protocol

1. Isolation of the Cardiac Nuclei

1. Coat ultracentrifuge tubes (Beckman Centrifuge Tubes #363664) with 10 ml of 1%BSA/PBS coating solution. Cap the tubes and let them rotate for 30 min in a tube rotator. Remove the coating solution and let the centrifuge tubes air dry (one tube per mouse heart is required for the analysis of single mouse hearts, alternately up to 5 mouse hearts or 1 g of heart tissue from a different species (e.g. human) can be processed in one tube).
2. All following steps should be performed on ice. Dissect the left ventricle from fresh or snap-frozen mouse heart with a scalpel. Note, this protocol is optimized for mouse heart but ....

Discussion

Accurate identification of cardiomyocyte nuclei is crucial for the analysis of regenerative processes in the myocardium^2,3. Conventional techniques to isolate cardiomyocytes from fresh tissue are mainly based on enzymatic digestion of extracellular matrix proteins and the subsequent purification from interstitial cells by low speed centrifugation. Further purification of living cardiomyocytes from embryonic stem cells (ESC) can be performed by immunolabeling with surface markers such as SIRPA⁹ or mi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1. Lysis Buffer
Name of the reagent
0.32 M sucrose
10 mM Tris-HCl (pH = 8)
5 mM CaCl2
5 mM magnesium acetate
2.0 mM EDTA
0.5 mM EGTA
1 mM DTT
2. Sucrose buffer
Name of the reagent
2.1 M sucrose
10 mM Tris-HCl (pH = 8)
5 mM magnesium acetate
1 mM DTT
3. Nuclei storage buffer (NSB plus)
Name of the reagent
0.44 M sucrose
10 mM Tris-HCl (pH = 7.2)
70 mM KCl
10 mM MgCl2
1.5 mM spermine
Isotype rabbit IgG- ChIP Grade, #ab37415	Abcam
Rabbit anti-PCM-1 antibody, #HPA023374	Atlas Antibodies
Donkey sec. antibody, anti-rabbit Alexa 488 Fluor, #A-21206 or equivalent sec. fluorescent antibody	Life Technologies
DRAQ5	Biostatus
cell strainers 30 μm, 70 μm and 100 μm	BD Biosciences
Glass douncer (40 ml) and pestle "L"	VWR (Wheaton Industries Inc.)
T-25 Ultra-Turrax Homogenizer	IKA Germany
Dispersing tool S25 N-18 G	IKA Germany
Beckman Avanti Centrifuge	Beckman Coulter
Falcon Tubes 15 ml and 50 ml	VWR
Beckman Centrifuge Tubes #363664	Beckman Coulter
JS13.1 free swinging rotor	Beckman Coulter
Influx cytometer	Beckman Coulter
Tube Rotator	VWR