Flashcards in Lecture 27 Deck (13)
What is the function of neutrophils in muscle repair?
Neutrophils release degradative enzymes; destroy debris; increase vascular permeability.
Stimulate monocyte accumulation; stimulate satellite cells.
What is the function of macrophages in muscle repari?
phagocytose debris and neutrophils; release factors that activate and stimulate satellite cells.
What is the effect of duration of inflammation on the response?
Sometimes too much inflammation can occur and other times too little inflammation can occur. Both can comprimise the optimal regeneration of the muscle.
What is the inflammatory response like in older adults?
Older adults have a much greater inflammatory response than young adults. They also have a diminished expression of myoD and myogenin. This results in a blunted response to muscle injury.
How are myotubes aligned correctly within muscle cells that are being repaired?
Basal lamina forms scaffold for muscle alignment and so myotubes can not be produced correctly if the basal lamina is damaged.
What factors determine the rate of muscle regeneration?
Extent of the injury, number of cells to replace
The muscle injured
The animal model: species, metabolic rate, etc
Differential expression of transcription factors, myogenic regulatory factors, and growth factors.
Host (systemic) environment (young vs old)
What are some factors that affect aging that could also result in slow regeneration of muscle?
Physical activity is reduced.
GH and growth factors are reduced.
Neural support is also reduced
What happens to muscle regeneration if nerve supply to that muscle is not active?
If nerve attachment is compromised this results in loss of regenerative capacity.
What is the benefit of this method of regeneration?
Deficit in force production is reduced after regeneration. Making the muscle more resistant to damage in subsequent injuries.
What does the costamere contain and what is its function?
Costamere contains the DCG and viculin-talin-integrin proteins which transfers the force from the cytoskeleton to the Extracellular matrix.
What happens to the fiber types of muscles that have been injured after 7 days and after 14 days?
Regenerating muscles, like embryonic muscles, undergo fiber type transitions according to functional demand (load bearing, etc). This is influenced by change in the type of myosin present.
After 14 days the fiber phenotype return to the original fiber type (slow twitch returns to being slow twitch and vice versa). The force produced by the 14th day is still less than the original force produced by the muscle. With type force returns to normal
*This is important when considering injured players and how their performance will be affected by the injury.
What interventions can be made to make recovery post exercise quicker?
Some drugs can be introduced to inhibit fibrosis in muscle cells which make recovery quicker post injury.
*Anti-fibrotic agents, for example, that antagonize TGF-beta1 can prevent fibrosis and improve muscle healing and recovery.
*Growth factors (eg IGF-1) can improve muscle regeneration but post injury healing process remains incomplete and fibrosis may still occur as a result of this treatment.