Regeneration and transdifferentiation of skeletal muscle
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Transcript of Regeneration and transdifferentiation of skeletal muscle
Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
REGENERATION AND TRANSDIFFERENTIATION OF SKELETAL MUSCLE
Dr. Péter Balogh and Dr. Péter EngelmannTransdifferentiation and regenerative medicine – Lecture 7
Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011
TÁMOP-4.1.2-08/1/A-2009-0011
Conditions requiring skeletal muscle regenerationInjury leading to extensive muscle damageInherited diseases – Duchenne’s muscular dystrophy:• X-linked mutation of dystrophin gene• 1:3500 males affected• Dystrophin (2.4 Mb in size) is the largest known
mammalian gene • Onset of the disease: DMD-afflicted patients are
diagnosed in childhood. The progressive muscle-wasting disease affects striated muscle including limb muscles, diaphragm, and heart leading to cardiorespiratory failure, and death usually occurs in the teenage years or early 20s.
TÁMOP-4.1.2-08/1/A-2009-0011Experimental models for studying muscle regeneration• Mdx mice: spontaneous mutation of the distrophin
gene (variable severities in different inbred mouse strains)
• Distrophin/utrophin double mutant mouse• Canine X-linked muscular dystrophy (cxmd) is the
best representation of DMD, but the phenotype is variable.
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Embyonic development of skeletal muscle
Myf5 Myf6Pax3
MyoD
MyogenesisMyogn Myf6, MyoD
NT
NC
MTSC
Limb VLL
DTDT
SC
Myf5Pax3/Pax7
MyoD
Bmp4
Wnt1/3Nog
Wnt11
Pax3
MyoD ShhWnt7a
NogMyf5
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Transcriptional control of myogenic differentiation
Transit Amplifying cells
MyotubeMyoblastDifferentiationActivation/Proliferation
Myogenic progenitor cells (MPC)Myogenic stem cell (MSC)Quiescent
Cd34Cdh15Foxk1MetPax3Pax7Sox8Sdc4Sox15Vcam1
Myf5Myf6MyoD
DesMyog
Myofibernuclei
Injury Fusion Differentiation Maturation
Proliferation andself-renewal of satellite cells
Regeneratingmyofiber nuclei
Satellite cell(quiescent)
Satellite cell(quiescent)
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Cellular sources for muscle regeneration• Satellite cells and their precursors• Endothelial cells associated with embryonic limb
muscles• Mesangioblasts• Bone marow-derived stem cells • Pluripotent cells found within muscle-derived side
population (SP) cells• Highly active Mdr-dependent expulsion of Hoechst
33342 dye
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Tissue sources for muscle regeneration
Vascular progenitors
Interstitial cells
Bone marrow cells
Myofibernuclei
Satellitecell
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Muscle stem cells – satellite cells• The satellite cells reside beneath the basal lamina of
muscle, closely juxtaposed to muscle fibers• Approximately up 2–7% of the nuclei associated with
a particular fiber• Heterogeneous composition: fusing/non-fusing
subsets• Ontogeny: somite/perivascular cells expressing
Pax3/Pax7• Surface markers
– Mouse: M-cadherin, CD34, VCAM, CD56, c-met (HGF-receptor)
– Human: CD56
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Structure and regeneration of skeletal muscle
Myofibril
Hematopoietic cells
Pericyte
Endothelial cell
Arteriole andcapillaries
Interstitial cell
Basal lamina
Satellite cell(SC)
Muscle fiber
Myonucleus
Quiescent SCPax7+
Activated SCPax7+
Myf5+MyoD+
Fusion anddifferentiation
Return toquiescence
MyoblastPax7-
Myf5+MyoD+
Expansion(symmetric
division)
Asymmetricdivision
Activation
MyocyteMyoD+
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Kinetics of muscle repair
Activation
Proliferation
Differentiation
Maturation
0 1 2 5 10 14Days post injury
TÁMOP-4.1.2-08/1/A-2009-0011Problems with myoblast regeneration in Duchenne’s muscular distrophy• Necessity for immunosuppression • Immunosuppressant drugs cause myoblast apoptosis• Short migratory distance following intramuscular
injection – 100 injections/cm2 (totalling up to 4,000 injections in a single patient!)
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Non-SCs contributing to muscle regeneration
Expansion
Commitment (if needed) Allogeneic transplantationAutologous transplantation(after genetic correction)
Mesenchymal differentation
Adipose-derived stem cellsMyoD-converted cells
HSCsSide population
Mesenchymal stem cellsMAPCs
SCs and subpopulationsMDSCs
CD133+ stem cells
HSCsSide population
CD133+ stem cells
MABs/pericytesMyoendothelial cells
EPCsMSCs
iPS cells
Reprogramming
Dermis or other tissues
Skeletal muscle
Bone marrow
Other sources
Blood
Vessels
Characterization
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Summary
• The prime candidates for skeletal muscle regeneration are the satellite cells, but cells from other sources (embryonic as well as non-embryonic) may also associate/promote the process.
• Muscle regeneration is accomplished through (a) promoting vascular repair, (b) cellular differentiation from muscle stem cells and (c) possible transdifferentiation.