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.
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