Researchers in the U.S. have developed an exciting new way of growing muscle tissue in the lab. The team, headed by Professor Warren Grayson of Johns Hopkins University Baltimore, are able to generate functional muscle tissue to a degree that has not been achieved in any previous studies.

This is a significant finding that could have applications in many conditions associated with muscle damage. However, the group focuses their study towards treating a condition called volumetric muscle loss (VML).

Volumetric Muscle Loss

As the name suggests, VML is the rapid loss of significant volumes of muscle leading to permanent physical disabilities. It is caused by severe trauma and is a common condition amongst military veterans.

Therapies are limited by the fact that damaged muscle tissue is difficult to heal without significant medical intervention. More simply, the body cannot recover from the volumes of muscle that are lost in cases of such severe trauma.

As a result, there is a great demand for innovative ways of regenerating new, healthy muscle tissue in cases of volumetric muscle loss.

A Significant Breakthrough?

In a multi-institute collaboration, the researchers have developed a platform for growing muscle tissue that is functional to an unprecedented level.

The success of the technique is likely down to how the researchers have designed their system. Muscle cells are grown in a hydrogel scaffold comprised of a protein called fibrin. The protein is normally associated with blood clotting but the researchers are interested in its ability to form fibrous structures.

The team are able to exploit this to produce a scaffold that mimics the organised network of fibres that make up muscle tissue. When muscle cells are incorporated into the fibrin network, they align along the fibres.

As a result, the fibrin-based structures are able to contract and function like normal muscle tissue.

Treating VML

Building on this, the team have looked at the clinical potential of their scaffolds by implanting them into a mouse model of VML. In the published study, the scaffolds were inserted into large muscle defects and left for 4 weeks to encourage healing.

Remarkably, the researchers have shown that the treated mice gain complete functional recovery at the site of muscle loss after only 2 weeks (untreated mice do not). Even more interestingly, this can be achieved by implanting the fibrin scaffold both with and without muscle cells.

This is because, when mice are treated with cell-loaded fibrin scaffolds, regeneration is kick-started by cells incorporated within the implant. However, when muscle cells are absent from the implant, it acts as a platform for regenerating tissue using cells from within the mouse’s body.

In essence, it promotes the body’s natural healing mechanisms and aids development of new muscle tissue.

A New Therapy For Volumetric Muscle Loss?

This is a very exciting breakthrough for treating disabilities associated with muscle loss. A lot of work is still required before a therapy like this can make its way to the clinic. However, this study represents a significant step in the right direction.

A lot of the disabilities associated with conditions like VML result from our body’s inability to cope with severe trauma. Technologies such as this could give our internal repair mechanisms the boost required to make a significantly better recovery.

Gilbert-Honick, J., Iyer, S. R., Somers, S. M., Lovering, R. M., Wagner, K., Mao, H.-Q. & Grayson, W. L. Engineering functional and histological regeneration of vascularized skeletal muscle Biomaterials, February 2018, DOI: 10.1016/j.biomaterials.2018.02.006.

Author: Dr Sam Moxon; Biomaterials Research Associate at the University of Manchester. Image: Adrian Wressell, Heart of England NHS FT. CC BY

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