Satellite Cells 2 Flashcards
What factors can stimulate satellite cells to differentiate
Immune response - interleukins and inflammatory cells
Vasculature - EGF, Insulin GF-I,II
Motor neuron
Testosterone
NO
Autocrine factors - IGF-I, IGF-II
What are the roles of IGF in satellite cells
IGF increases proliferation in activated satellite cells
IGF promotes muscle differentiation in the presence of Mef2 and other late MRFs
When are the number of satellite cells reduced
Ind dystrophies or elderly
Why are satellite cells needed
Exercise causes microtrauma due to overload - requires cell replacement
How do satellite cells repair and regenerate skeletal muscle?
Myotrauma and inflammation activate satellite cell proliferation, allowing them to line up across the affected site
Satellite cell start to differentiate and fuse to the existing myotubes and to each other
Myofibre is regenerated
A small number of satellite cells goes back to quiescence and refills the satellite cell pool
Broadly speaking, what causes muscular dystrophies regarding satellite cells
Balance between Pax and MRFs is important to determine if satellite cells proliferate or initiate terminal differentiation. There is an imbalance in these patients
What did Sadeh discover regarding satellite cells in 1985
Gave bupivacaine to rodents weekly which breaks down muscel fibres but keeps nerves, vessels and satellite cells unaffected.
Showed that satellite cells were able to keep up with the level of muscle breakdown - therefore shows the high capacity that satellite cells have.
What happens to protein in muscle hypertrophy
Positive protein balance - increase synthesis and/or decreased degradation
Why do myotubes have more than one nucleus
Myotubes are too big to be controlled by only one nucleus
one myo-nucleus controls only a small part of the myotube
Many nuclei are needed to get the mRNA to the distal ribosomes within the muscle cell.
Why are satellite cells important for muscle growth
In the muscle growth, the protein content of a myotube increases which means it becomes to big for the number of nuclei to manage it. Therefore, the number of myo-nuclei must increase by fusion of addition satellite cells to allow for muscle growth.
The number of satellite cells is seen to increase in resistance training.
What did Pax7 -/- mice show regarding cell differentiation
WIDER READING - Seale 2000
These mice were able to form 10-fold of hematopioetic cells (going backwards with regards to differnetation) meaning that PAX7 must be crucial to induce satellite cell specificaiton and restricting it from becoming another stem cell type unrelated to muscle cells.
Why are satellite cells restricted in medical treatment
Kowalski 2017
Used male mice in vitro from gastromncemius muscle and degraded the muscle and injected satellite cells.
Transplanted satellite cells have a limited capacity for migration, and are only able to regenerate muscle in the region of the delivery site. As such, systemic treatments or even the treatment of an entire muscle in this way is not possible.
