But the growth of usable human tendon cells, which have to be stretched and twisted, has been more complicated. Over the past two decades, scientists have encouraged the cells and tissues of designed tendons to grow and mature by repeatedly stretching them in one direction. However, this approach has so far failed to produce fully functional tissue grafts that could be used clinically in the human body.
A new study, published today in Nature Communications Engineering, shows how humanoid robots could be used to make designed tendon tissue that looks more like reality.
“The clinical need is clearly there,” says Pierre-Alexis Mouthuy of Oxford University, who led the team. “If we can create in vitro grafts that can be of good enough quality for use in clinics, that would be very helpful in improving patient outcomes. Any improvement would be more than welcome.”
The first step involved redesigning the test chamber that houses the cells, known as the bioreactor, to connect it to a humanoid robot shoulder that can bend, push, stretch, and twist the cells in the same way that so would the musculoskeletal tissues.
While traditional bioreactors look like rigid boxes, the team created a flexible one in which human fibroblast cells (elongated cells found in connective tissue) are grown in a soft plastic scaffold. suspended between two rigid blocks. They connected this camera to the robotic shoulder, which spent half an hour a day for 14 days replicating the types of elevations and rotational movements a human would make.
Bioreactor cells were then found to reproduce faster than samples that had not been stretched, and to express genes differently, although researchers still do not know how this would translate into graft quality. The team plans to investigate how cells grown in its new bioreactor are compared to those grown in traditional bioreactors.