SKELETAL MUSCLE TISSUE

Question 1

Introduction about the skeletal muscle progenitor cells

Answer 1

What are the muscle fibers and how they originate
1961: Alexander Mauro noticed cells between the plasmalemma surface and the basement membrane surrounding the fibers > satellite cells, function of maintenance and growth of the skeletal muscle
In the adult mitotically quiescent, 2-5% of all the cells in the fibers from the birth to the middle age
Once activated following an injury, they enter the cell cycle, the proliferate and eventually rest in G1 phase to form terminally differentiated and multinucleated fibers
Markers: Pax7, Pax3 and Myf5, upregulated after their activation

Question 2

Activation of the satellite cells

Answer 2

Resting G0 SC activated upon an injury or an intense exercise can give rise to:
-90% of committed precursors Pax7+Myf5+ > then, start to express MyoD, re enter the cell cycle as myoblasts and differentiate into myocytes, upregulating myogenin and downregulating Pax7
-10% of other SC
Depending on the orientation of the mitotic spindle:
-asymmetric division: perpendicular to muscle fibers
-symmetric expansion: parallel to muscle fibers, induced by Wnt7a
SC activation can be triggered by muscle injury/damage, exercise or diseases depending on physiological stimuli, signalling molecules, epigenetic changes.

Question 3

Activation of SC depending on the physiological stimuli

Answer 3

-damage/alteration of the SC niche formed by the sarcolemma and the basal lamina
-immune cell infiltration
-damage to the blood vessels

Question 4

Activation of the SC depending on signalling molecules

Answer 4

-HGF
-NO
-IGF
-FGF
-Notch
-Wnt
-TGF-beta

Question 5

SC and aging

Answer 5

Role of the autophagy and mitochondrial dynamics in the proteostatic and metabolic regulation

Question 6

SC and exercise in diseases related to the exhaustion of proliferative SC

Answer 6

Exercise downregulation of the Akt-mTOR pathway: prevention of the exhaustion

Question 7

SC cell therapy and diseases

Answer 7

Duchenne muscular distrophy mouse model
Practical limitations
IPSCs and gene targeting with CRISPR-CAS9 technology

Question 8

The mesoangioblasts

Answer 8

What they are
To which kinds of cells they can give rise