Tissue Engineering of Skeletal Muscle
http://www.liebertonline.com/doi/abs/10.1089/ten.2006.0408
Tissue Engineering
Tissue Engineering of Skeletal Muscle.
Wentao Yan, Sheela George, Upinder Fotadar, Natalia Tyhovych, Angela Kamer, Michael J. Yost, Robert L. Price, Charles R. Haggart, Jeffrey W. Holmes, Louis Terracio. Tissue Engineering. ahead of print. doi:10.1089/ten.2006.0408.
Although a considerable amount of research has been done in skeletal muscle tissue engineering, there has yet to be a method for replacing lost tissue. In their study, Yan et al. have suggested the possibility of reconstruction through an in vitro construction of skeletal muscle with satellite cells to be reconstituted in vivo. Their 3D skeletal construct, engineered by seeding satellite cells on an aligned matrix of type I collagen fibrils, has been shown to closely resemble adult skeletal muscle function and structure and brings us only one step closer to a striated muscle implant in the future.
Experimental results prove the validity of their construct. Immunohistochemical staining of actin filaments and MyoD, the regulatory protein in muscle differentiation, revealed the differentiation of the satellite cells to myotubes and the parallel orientation of the multilayer muscle cells that are characteristic of skeletal muscle. Real-time RT-PCR tracked the muscle cell maturation process by assessing gene expression for various proteins. mRNA expressions for embryonic and adult myosin heavy chain, dystrophin, and alpha- and beta-enolases were consistent with patterns of in vivo mRNA expression reported in previous studies. Cell viability, measured using Trypan blue, was determined to filter out the possibility of death with aberrations in gene expression. Twitch and titanic stresses were implemented on the cells to test for their function. Measurements of the construct showed that the amount of developed force increases with the amount of stretching until the force plateaus. This force-length relationship observed parallels with that of known skeletal muscle. It is clear from their analyses that their construct mimics the basic phenotypes of adult skeletal muscle; however, their research is still incomplete. Further examinations on thickening the culture, contributions of extracellular matrix components, and hypertrophy of muscle stretching are needed until we can perform the first muscle transplant.
As the paper indicates, muscle loss has no answer, so I believe this study has a lot of potential in solving the problem. What I found most interesting is how simple the muscle construct was—a plate painted with stripes of collagen, seeded with isolated satellite cells. This comes to show that a project as a complex as skeletal muscle tissue engineering need not necessarily be carried out with an intricate protocol, but rather one that is well thoroughly thought-out. In addition, I realized how universal and widely-applicable the techniques we learned in class are. In fact, most of the techniques Yan et al. used to characterize their construct were introduced to us in class—immunochemistry, RT-PCR, Trypan blue counting. For my project, I hope to research on a topic related to skeletal muscle engineering, and I feel that this paper will serve as a good guideline.
4 comments:
This sounds like a significant development in the tissue engineering of replacement skeletal muscle. Did the researchers try stimulating the cells with a simulated nerve impulse or with any signaling molecules or proteins?
Great article! How would the implanted muscle respond to new damage? As I understand it, normally the satellite cells in our muscles activate upon injury of the muscle and replace the damaged unit. How would this tissue engineered muscle replacement perform when damaged?
It is interesting how these satellite cells differentiate into myotubes and other myocytes that closely resemble that of skeletal muscle simply in the presence of type I collagen fibrils. Did Yan et al. add any growth factors or other components beside the collagen to induce such a successful differentiation?
Ben and David: The simplicity and reproducibility of their skeletal muscle model is what amazed me most. Other than the lines of type I collagen fibrils and satellite cells, the researchers added a differentiation medium of DMEM (which is basically a medium impacted with vitamins, iron, and amino acids), serum, antibiotics, and HEPES (which we learned from class is a pH-maintaining agent).
Lizhi: Though the article does not explicitly say how the model would respond to new damage, I believe it would mimic the processes as that of normal muscle. Because the transplant model was seeded with a tens of millions of satellite cells, I think that those that do not differentiate into mature muscle cells would become activated from their quiescent state to regenerate the damaged muscle. Again, I am not sure if this is exactly true, but judging from their model's morphological, molecular, and physiological similarities to real muscle, it seems reasonable to believe that the responses to trauma should be similar as well.
Let me also add that, when the trauma is too extreme, the healing/regeneration process is inefficient as satellite cell activation is hindered by the accompanying overgrowth of fibroblast cells located within the connective tissue network.
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