Upon minimal stimulation, satellite cells
in vitro or
in vivo will undergo a myogenic differentiation program. Unfortunately, it seems that 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. However, other cells in the body such as
pericytes and
hematopoietic stem cells have all been shown to be able to contribute to muscle repair in a similar manner to the endogenous satellite cell. The advantage of using these cell types for therapy in muscle diseases is that they can be systemically delivered, autonomously migrating to the site of injury. Particularly successful recently has been the delivery of
mesoangioblast cells into the
Golden Retriever dog model of
Duchenne muscular dystrophy, which effectively cured the disease. However, the sample size used was relatively small and the study has since been criticized for a lack of appropriate controls for the use of immunosuppressive drugs. Recently, it has been reported that Pax7 expressing cells contribute to dermal wound repair by adopting a fibrotic phenotype through a Wnt/β-catenin mediated process.
Regulation Little is known of the regulation of satellite cells. Whilst together
PAX3 and
PAX7 currently form the definitive satellite markers, Pax genes are notoriously poor transcriptional activators. The dynamics of activation and quiesence and the induction of the myogenic program through the
myogenic regulatory factors,
Myf5,
MyoD,
myogenin, and
MRF4 remains to be determined. There is some research indicating that satellite cells are negatively regulated by a protein called
myostatin. Increased levels of myostatin up-regulate a
cyclin-dependent kinase inhibitor called
p21 and thereby inhibit the differentiation of satellite cells.
Myosatellite cells and cultured meat Myosatellite cells contribute the most to muscle regeneration and repair. This makes them a prime target for the
meat culturing field. These satellite cells are the main source of most muscle cell formation postnatally, with embryonic myoblasts being responsible for prenatal muscle generation. A single satellite cell can proliferate and become a larger amount of muscle cells. With the understanding that myosatellite cells are the progenitor of most
skeletal muscle cells, it was theorized that if these cells could be grown in a lab and placed on scaffolds to make fibers, the muscle cells could then be used for food production. This theory has been proven true with many companies sprouting around the globe in the field of cultured meat including
Mosa Meat in the Netherlands, and
Upside Foods in the USA. An overview of the culturing process first involves the selection of a cell source. This initial stage is where the selection of a meat type happens, for example if the desired product is beef then cells are taken from a cow. The next part involves isolating and sorting out the myosatellite cells from whatever the selected cell source was. After being separated into the cellular components, the myosatellite cells need to be proliferated through the use of a
bioreactor, a device used to grow microorganisms or cells in a media that can be easily controlled. Whatever media chosen will simulate the cells being in prime condition to proliferate within an organism. After proliferation the cells are shaped using a scaffold. These scaffolds can be an organic structure like decellularized plant or animal tissues, inorganic such as
polyacrylamide, or a mix of both. Once the cells have attached themselves to the scaffold and fully matured, they have become a raw meat product. The final step will include any necessary food processes needed for the desired final product. == See also ==