BDC #10 - Satellite Cells

Hello!!! Are missing the BDC series? Relax!! I am still studying, so there will always a new post for this series.

I have a new homework today (d*mn!! I shouldn't take this class!! They give a journal-review-HW every week >.<  hahahaha!!!). This time, it's walking about "Satellite Cells". Hem.... what is that? I only know there 2 things called the satellite cells: the myosatellite cells and satellite glial cells. For now, I will only talk about the first one, Myosatellite Cells.

Myosatellite Cells, or just Satellite Cells, are precursor or progenitor cells for skeletal muscle cells. Precursor or progenitor in cell biological term means "soon to be / going to be", and skeletal muscles are muscles attached to your bones, work for the body movement. So these muscles are not related to internal organs. 

These cells are located between the basal lamina and sarcolemma of the muscle fibers. Basal lamina is a layer of extracellular matrix secreted by epithelial cells, where the epithelium sits. On the other hand, sarcolemma, also called myelomma, is the cell membrane of muscle cells, either the skeletal, cardiac, or smooth muscles. The experts say that it's actually quite easy to distinguish these cells amongst the muscles fibers due to its' unique characters; such as, high nuclear-to-cytoplasmic volume ratio (comparatively small nuclear size), few organelles, and a large quantity of nuclear heterochromatin relative to myonuclei.

These cells was actually founded in 1961 (pretty early, huh?) by Alexander Mauro. During that time, without any solid evidence yet, he already hypothesized that these cells represent a kind of muscle progenitor cells, capable of forming new muscle in response to injury.  The experts indeed confirmed this hypothesis years later. 

While there is an injury on the muscle, satellite cells will proliferate following the muscle trauma and form new myofibers through a process similar to fetal muscle development (fetal = baby). After several cell divisions, the satellite cells begin to fuse with the damaged myotubes and undergo further differentiations and maturation, with peripheral nuclei as in hallmark. 

Upon minimal stimulation, satellite cells in vitro or in vivo might continue to the myogenic differentiation process. However, it looks like the transplanted satellite cells have a limited capacity for migration, and are only able to regenerate muscle in the region of the delivery site.  BUT other cells in the body such as hematopoietic stem cells (HSCs) have all been shown to be able to contribute to muscle repair in a similar manner to the endogenous satellite cell. And the advantage of using these cell types for therapy in muscle diseases is that they can be systemically delivered and migrating to the site of injury by themselves. A successful therapy recently has been the delivery of mesoangioblast cells into the Golden Retriever dog model of Duchenne muscular dystrophy, which effectively cured the disease (link).

By the end, we still don't know exactly how to really implement the stem cells therapy to cure diseases. However, if we keep on being curious and researching, we will definitely find ways!! So... keep trying my fellow researches!!!! 

If you want to learn more about these Satellite Cells, you can try to read this review paper.