Muscle cells have been grown in the lab without genetic engineering
Researchers have developed a safe method for the rapid production of muscle cells from connective tissue.Bioengineers from the Swiss ETH Zurich have developed a technology to produce muscle cells from connective tissue without altering the genome. Using a cocktail of small molecules and proteins, they "reprogram" connective tissue cells into muscle stem cells. The latter rapidly multiply and produce muscle fibers.
An important component of the cocktail and a central catalyst of cellular transformation is the MyoD protein. It is a transcription factor that regulates the activity of certain muscle genes in the cell nucleus. MyoD is normally absent in connective tissue cells. To "transform" cells, they must produce this protein in the nucleus within a few days.
Traditionally, researchers have used genetic engineering to accomplish this. Viral particles that contain the code to produce the protein are embedded in the cell nucleus. But this is a risky approach: scientists cannot control which parts of the genome the virus will insert instructions into. In some cases, such a procedure makes cells unviable or leads to mutations and the formation of cancer cells.
To avoid the risk, Swiss bioengineers do not change the original genome of the cell, but introduce mRNA of the desired gene into them. Matrix RNA (mRNA) is synthesized from DNA during transcription and serves as the basis for protein synthesis in cells. Such changes do not disrupt the genome, but trigger the production of the MyoD protein. Together with other components of the cocktail, this triggers the conversion of connective tissue into muscle fibers.
The researchers demonstrated their method on mouse cells, but they are confident that the adapted principle will work in humans as well. Such artificial muscle fibers in the future can be used in surgery, and muscle stem cells can be used to treat certain diseases. In addition, the method can be adapted for cows and artificial meat can be produced.