Most people who have sweated it out in the gym trying to add a bit of muscle definition to their bodies will know just how difficult such a task is, but trying to grow muscle tissue with a real muscle structure complete with blood vessels in the laboratory has proven to be an even more difficult brief for researchers. Now a team from the Eindhoven University of Technology (TU/e) has done just that, paving the way for the creation of engineered muscle tissue that can be implanted into patients who have lost muscle tissue through accidents or surgery.

Although other researchers have succeeded in engineering muscle tissue containing blood vessels, the TU/e team says that the muscle cells and blood vessels in these cases were disorganized. This is a problem because the muscle cells need to be aligned in the same direction to give the muscles their strength, and the muscles also need blood vessels to supply them with oxygen and nutrients.

The TU/e research team achieved where others had failed by first producing engineered muscle tissue from a mixture of pre-cultured stem cells and blood vessel cells from mice in a gel. The pieces of cultured tissue, measuring 2 x 8 mm, were then fastened in one direction using Velcro to prevent the shrinkage that usually results from this process. The resulting tension caused the muscle cells to become aligned in the culturing process. It is this alignment that is essential for the muscles to be able to exert a force.

In addition to the alignment of the muscle cells, blood vessels were formed without the need for the researchers to add any growth factors, as the muscle cells produced the required growth factor themselves as a result of the tension applied. The researchers say this is a big plus because the action of biochemical growth factors, which are normally required to initiate the process, is often difficult to control.

Up until now, the researchers say the maximum thickness of engineered muscle tissue that could be achieved in the lab was just 0.4 mm, because the cells must be located no further than 0.2 mm from a blood vessel or other source of nutrients to ensure that they receive sufficient oxygen. The formation of blood vessels seen in the TU/e process, which will allow blood supply through the blood vessels, means that it will be possible to feed the engineered muscle from within and culture thicker tissue in the near future, claim the researchers.

The TU/e team says the aim of the research is to ultimately allow the treatment of people who have lost tissue - through accidents of surgery to remove tumors, for example.

"Just one example is the restoration of facial tissue", explains Dr. Daisy van der Schaft. "Using these engineered muscle tissues would not just be cosmetic, but would give function back to the tissue."

Dr. Van der Schaft expects such treatments to be possible within the next ten years.

The team will next begin working on the engineering of thicker muscle tissue and say the same techniques will need to be applied to human cells. Dr. Van der Schaft says researchers at the University Medical Center Groningen, working in partnership with the TU/e research team, has already started to engineer human muscle tissue.

The TU/e team's study entitled "Mechanoregulation of vascularization in aligned tissue engineered muscle; a role for VEGF" appears in the journal Tissue Engineering Part A.

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