Human yarn production: (From left) A fresh sheet of CAM is detached from the flask after 8 weeks of culture and stretched over a frame. Ribbons 5-mm-wide are obtained by cutting a CAM sheet. Ribbons are twisted to obtain threads, dried and spooled onto a bobbin. When needed, the yarn is rehydrated and assembled by knitting, weaving, or winding to form complex structures or used in simple form as a suture.
Photo of the spooled thread.
Photo of a vascular graft being woven on a circular loom.Researchers have created a completely ‘bio’ yarn from human cells that can be braided, knitted, or woven into medical devices or scaffolds, which can be integrated into the body without eliciting an immune reaction [Magnan et al., Acta Biomaterialia 105 (2020) 111-120, https://doi.org/10.1016/j.actbio.2020.01.037].
Medical textiles currently used for suturing wounds or as vascular grafts for blood vessel repair, for example, are typically made from permanent polymers such as GORE-TEX® or biodegradable materials such as polyglycolic acid or collagen. Synthetic materials tend to be recognized by the body’s immune system, giving rise to an inflammatory response, while biodegradable materials can can loose strength too rapidly for more demanding applications. Tissue engineering is particularly dependent on synthetic biomaterials as scaffolds for cells to populate or regrow on, but a completely biological alternative would be highly desirable.
“For decades, we have been able to grow human cells in the lab,” says Nicolas L’Heureux, of the University of Bordeaux/INSERM, who led the research. “My team has been working for a long time on getting normal human cells to produce actual tissues. In the right conditions, a thin but strong sheet of human collagen (and other important proteins) is assembled by the cells.”
This material is known as cell-assembled extracellular matrix, or CAM, and can be mass-produced for clinical applications including tissue engineering. However, the process is complex and the usefulness of sheets for creating different shapes is limited. Now the researchers working at the University of Bordeaux/INSERM have created yarns of human cells from sheets of CAM.
“We make yarn by cutting the CAM sheet into ‘ribbons’ that can be used directly or twisted into ‘threads’ [with] slightly different mechanical properties,” explains L’Heureux.
The yarns, which can be 2-10 mm wide and up to 3 m long, can be used as they are as simple sutures for wound repair or woven, knitted, or braided into almost any shape. Multiple yarns can be twisted together to create thicker, stronger yarns if different mechanical properties are needed. The yarn can be simply dried, stored frozen, and rehydrated when needed.
“Textile assembly can be automated so tissue production will eventually be much faster, easier, and cheaper than with a sheet-based approach,” says L’Heureux. “Since the approach is very versatile, it can address many applications.”
As an example, the researchers fabricated a vascular graft from woven ‘human textile’ with properties that surpass clinical requirements. Unlike synthetic material, these fully ‘bio’ materials could be readily accepted by the body without eliciting an immune response.