Isolation of Mouse Megakaryocyte Progenitors

Summary

This method describes the purification by flow cytometry of MEP and MKp from mice femurs, tibias, and pelvic bones.

Abstract

Bone marrow megakaryocytes are large polyploid cells that ensure the production of blood platelets. They arise from hematopoietic stem cells through megakaryopoiesis. The final stages of this process are complex and classically involve the bipotent Megakaryocyte-Erythrocyte Progenitors (MEP) and the unipotent Megakaryocyte Progenitors (MKp). These populations precede the formation of bona fide megakaryocytes and, as such, their isolation and characterization could allow for the robust and unbiased analysis of megakaryocyte formation. This protocol presents in detail the procedure to collect hematopoietic cells from mouse bone marrow, the enrichment of hematopoietic progenitors through magnetic depletion and finally a cell sorting strategy that yield highly purified MEP and MKp populations. First, bone marrow cells are collected from the femur, the tibia, and also the iliac crest, a bone that contains a high number of hematopoietic progenitors. The use of iliac crest bones drastically increases the total cell number obtained per mouse and thus contributes to a more ethical use of animals. A magnetic lineage depletion was optimized using 450 nm magnetic beads allowing a very efficient cell sorting by flow cytometry. Finally, the protocol presents the labeling and gating strategy for the sorting of the two highly purified megakaryocyte progenitor populations: MEP (Lin^-Sca-1^-c-Kit⁺CD16/32^-CD150⁺CD9^dim) and MKp (Lin^- Sca-1^-c-Kit⁺CD16/32^-CD150⁺CD9^bright). This technique is easy to implement and provides enough cellular material to perform i) molecular characterization for a deeper knowledge of their identity and biology, ii) in vitro differentiation assays, that will provide a better understanding of the mechanisms of maturation of megakaryocytes, or iii) in vitro models of interaction with their microenvironment.

Introduction

Blood platelets are produced by megakaryocytes. These large polyploid cells are located in the bone marrow and as for all blood cells they are derived from Hematopoietic Stem Cells (HSC)¹. The classical pathway of production of megakaryocytes in the bone marrow originates from HSC and involves the generation of different progenitors that progressively restrict their differentiation potential². The first progenitor signing the commitment to the megakaryocytic lineage is the Megakaryocyte-Erythrocyte Progenitor (MEP), a bipotent progenitor capable of producing both erythroid cells and megakaryocytes³

Protocol

Protocols involving animals were performed in accordance with the CREMEAS Committee on the Ethics of Animal Experiments of the University of Strasbourg (Comité Régional d'Ethique en Matière d'Expérimentation Animale Strasbourg. Permit Number: E67-482-10).

1. Mouse bone collection

1. Sacrifice the animal in compliance with the institutional guidelines.
   NOTE: The data presented in this manuscript were obtained from C57Bl/6 mice of 8 to 12 weeks old. Th.......

Discussion

The method described in this paper allows for the extraction and purification of mouse MEP and MKp. An important parameter in the optimization of the protocol was to obtain sufficient number of cells that would be compatible with most molecular- and cellular-based assays. The general practice of mouse bone collection for hematopoietic cell extraction usually consists in harvesting both the femurs and tibias of each mouse. The pelvic bone, another source of hematopoietic material, is thus often overlooked. The reasons for.......

Materials

Name	Company	Catalog Number	Comments
21-gauge needles	BD Microlance	301155
7AAD	Sigma-Aldrich	A9400
Antibody Gr-1-biotin	eBioscience	13-5931-85	Magnetic depletion
Antibody B220-biotin	eBioscience	13-0452-85	Magnetic depletion
Antibody Mac-1-biotin	eBioscience	13-0112-85	Magnetic depletion
Antibody CD3e-biotin	eBioscience	13-0031-85	Magnetic depletion
Antibody CD4-biotin	eBioscience	13-9766-82	Magnetic depletion
Antibody CD5-biotin	eBioscience	13-0051-85	Magnetic depletion
Antibody CD8a-biotin	eBioscience	13-0081-85	Magnetic depletion
Antibody TER119-biotin	eBioscience	13-5921-85	Magnetic depletion
Antibody CD127-biotin	eBioscience	13-1271-85	Magnetic depletion
Antibody CD45-FITC	eBioscience	11-0451-85	Cell sorting
Antibody CD45-PE	eBioscience	12-0451-83	Cell sorting
Antibody TER119-APC	eBioscience	17-5921-83	Cell sorting
Antibody CD45-PECy7	eBioscience	25-0451-82	Cell sorting
Antibody CD45-biotin	eBioscience	13-0451-85	Cell sorting
Antibody CD9-FITC	eBioscience	11-0091-82	Cell sorting
Antibody  c-kit-APC	eBioscience	17-1171-83	Cell sorting
Antibody Sca-1-PE	eBioscience	12-5981-83	Cell sorting
Antibody CD16/32-PE	eBioscience	12-0161-83	Cell sorting
Antibody CD150-PECy7	eBioscience	25-1502-82	Cell sorting
Culture medium StemSpan-SFEM	Stemcell technologies	#09650
Dissection pad	Fisher Scientific	10452395
DPBS	Life Technologies	14190-094
Ethanol	vWR Chemicals	83813.360
Forceps	Euronexia	P-120-AS
Glass pasteur pipette	Dutscher	42011
Magnet :  DynaMag-5	Thermo Fisher Scientific	12303D
Magnetic beads: Dynabeads Sheep Anti-Rat IgG	Thermo Fisher Scientific	11035
Megacult	Stemcell technologies	#04970
MethoCult SF M3436	Stemcell technologies	#03436
Newborn Calf Serum	Dutscher	50750-500
Red Cell Lysis solution	BD Bioscience	555899
Scalpels	Fisher Scientific	12308009
Scissors	Euronexia	C-165-ASB
Sterile 1 mL syringes	BD Bioscience	303172
Sterile 15mL tubes	Sarstedt	62.554.502
Sterile 5mL polypropylene tubes	Falcon	352063
Sterile 5mL polystyrene tubes	Falcon	352054
Sterile tubes with 70µm cell strainer cap	Falcon	352235
Sterile petri dish	Falcon	353003
Streptavidin-APC-Cy7	BD Biosciences	554063	Cell sorting
Tube roller	Benchmark Scientific	R3005