Unfractionated Bulk Culture of Mouse Skeletal Muscle to Recapitulate Niche and Stem Cell Quiescence

Summary

Skeletal muscle comprises multiple cell types, including resident stem cells, each with a special contribution to muscle homeostasis and regeneration. Here, the 2D culture of muscle stem cells and the muscle cell niche in an ex vivo setting that preserves many of the physiological, in vivo, and environmental characteristics are described.

Abstract

Skeletal muscle is the largest tissue of the body and performs multiple functions, from locomotion to body temperature control. Its functionality and recovery from injuries depend on a multitude of cell types and on molecular signals between the core muscle cells (myofibers, muscle stem cells) and their niche. Most experimental settings do not preserve this complex physiological microenvironment, and neither do they allow the ex vivo study of muscle stem cells in quiescence, a cell state that is crucial for them. Here, a protocol is outlined for the ex vivo culture of muscle stem cells with cellular components of their niche. Through the mechanical and enzymatic breakdown of muscles, a mixture of cell types is obtained, which is put in 2D culture. Immunostaining shows that within 1 week, multiple niche cells are present in culture alongside myofibers and, importantly, Pax7-positive cells that display the characteristics of quiescent muscle stem cells. These unique properties make this protocol a powerful tool for cell amplification and the generation of quiescent-like stem cells that can be used to address fundamental and translational questions.

Introduction

Movement, breathing, metabolism, body posture, and body temperature maintenance all depend on skeletal muscle, and malfunctions in the skeletal muscle can, thus, cause debilitating pathologies (i.e., myopathies, muscular dystrophies, etc.)¹. Given its essential functions and abundance, skeletal muscle has drawn the attention of research labs worldwide that strive to understand the key aspects that support normal muscle function and can serve as therapeutic targets. In addition, skeletal muscle is a widely used model to study regeneration and stem cell function, as healthy muscle can fully self-repair after complete injury ....

Protocol

All experiments complied with French and EU animal regulations at the Institut Mondor de Recherche Biomédicale (INSERM U955), notably the directive 2010/63/UE. Animals were kept in a controlled and enriched environment at the animal facilities with certification numbers A94 028 379 and D94-028-028; they were handled only by authorized researchers and animal caretakers, and they were visually inspected by animal housing personnel for signs of discomfort during their lifetime. They were euthanized by cervical dis.......

Discussion

Adult skeletal muscle function is underpinned by a finely orchestrated set of cellular interactions and molecular signals. Here, a method is presented that allows for the study of these parameters in an ex vivo setting that closely resembles the physiological microenvironment.

Several groups have reported in vitro methods to culture myogenic cells. These methods aimed to isolate satellite cells to study their myogenic progenitor properties. Two main approaches are used to iso.......

Materials

Name	Company	Catalog Number	Comments
anti-CD31	BD	550274	dilution 1:100
anti-FOSB	Santa Cruz	sc-7203	dilution 1:200
anti-GFP	Abcam	ab13970	dilution 1:1000
anti-Ki67	Abcam	ab16667	dilution 1:1000
anti-MyHC	DSHB	MF20-c	dilution 1:400
anti-MYOD	Active Motif	39991	dilution 1:200
anti-MYOG	Santa Cruz	sc-576	dilution 1:150
anti-Pax7	Santa Cruz	sc-81648	dilution 1:100
anti-PDGFRα	Invitrogen	PA5-16571	dilution 1:50
b-FGF	Peprotech	450-33	concentration 4 ng/mL
bovine serum albumin (BSA) – used for digestion	Sigma Aldrich	A7906-1006	concentration 0.2%
BSA IgG-free, protease-free – used for staining	Jackson ImmunoResearch	001-000-162	concentration 5%
cell strainer 40 um	Dominique Dutscher	352340
cell strainer 70 um	Dominique Dutscher	352350
cell strainer 100 um	Dominique Dutscher	352360
Collagenase	Roche	10103586001	concentration 0.5 U/mL
Dimethyl sulfoxide (DMSO)	Euromedex	UD8050-05-A
Dispase	Roche	4942078001	concentration 3 U/mL
Dissection forceps size 5	Fine Science Tools	91150-20
Dissection forceps size 55	Fine Science Tools	11295-51
Dissection scissors (big, straight)	Fine Science Tools	9146-11	ideal for chopping
Dissection scissors (small, curved)	Fine Science Tools	15017-10
Dissection scissors (small, straight)	Fine Science Tools	14084-08
Dulbecco's Modified Eagle's Medium (DMEM)	ThermoFisher	41966-029
EdU Click-iT kit	ThermoFisher	C10340
Fetal bovine serum – option 1	Eurobio	CVF00-01
Fetal bovine serum – option 2	Gibco	10270-106
Matrigel	Corning Life Sciences	354234	coating solution
Parafilm	Dominique Dutscher	090261	flexible film
Penicillin streptomycin	Gibco	15140-122
Paraformaldehyde – option 1	PanReac AppliChem ITW Reagents	211511.1209	concentration 4%
Paraformaldeyde – option 2	ThermoFisher	28908	concentration 4%
Shaking water bath	ThermoFisher	TSSWB27
TritonX100	Sigma Aldrich	T8532-500 ML	concentration 0.5%
Wild-type mice	Janvier	C57BL/6NRj