How Does Platelet-Rich Plasma Help Tendons Repair?


Athletes are always in a hurry to get back into action whether that’s on a football field, tennis court, or baseball diamond. For professional athletes, time is money and a place in the limelight. Tendon injuries are common among sports participants. And tendons are notorious for being slow to heal and quick to reinjure.

Efforts are being made to find ways to speed up and enhance the healing process. Scientists have discovered that human blood contains key ingredients for healing. The plasma portion of human blood (the clear liquid) has parts called components that may come to our aid.

In particular, tiny platelets circulate every minute of every day in the blood — they are always there in case of an injury. Platelets help form blood clots to stop bleeding. When the body signals that there is a need for platelets, they become activated and rush to the area of injury. Once there, they clump together to form a clot and then release tiny chemicals called growth factors.

It’s those growth factors that turn stem cells into tendons. Stem cells are basic cells that haven’t formed a specific type of cell (e.g., heart, muscle, joint, organ). The body can turn a stem cell into any kind of cell needed including tenocytes (tendon cells). In this study, blood and tendons were taken from rabbits and used together in the lab to see what the effect of platelet-rich plasma would be on the damaged tendon.

Actually, from previous experiments, they already know that platelet-rich plasma injected into injured tissues (such as ligaments and tendons) does help promote healing. The question now is: how does it do so? That’s the focus of this study. By examining the process in the laboratory under a microscope, scientists hope to unravel the mysteries of this healing helper.

By using different dosages of the platelet-rich plasma (two per cent and 10 per cent), they were able to measure the effects of each on the injured tendon cells. Using gene analysis, they could examine cells produced in the damaged tendons and see how many and what type of tissue was forming (e.g., collagen fibers, scar tissue, healthy tenocytes). The experiment included a control group — damaged tendons that did not receive the platelet-rich plasma.

They found that the platelet-rich plasma did indeed cause tendon stem cells to form into tenocytes. They were interested to note that once stimulated, these stem cells didn’t form other types of cells like fat cells, bone cells, or cartilage cells. That’s good because a mix of all those types would impair tendon healing rather than stimulate it.

Using platelet-rich plasma not only causes stem cells to form tenocytes, it also increases the number of tendon cells formed. Not only were there more tenocytes, but there was plenty of the right kind of collagen (the basic building block of all soft tissues) needed for healthy tendon tissue rather than weak scar tissue.

In summary, this study helps shine some light on how tendon stem cells fit into the picture of tendon healing and how platelet-rich plasma as a treatment might aid in that healing process. It is a safe procedure but one that will require further study to find the right concentration of platelet-rich plasma to get the ideal healing response.

There are far more “unknowns” about tendon healing and the role of platelet-rich plasma in tendon healing than we currently have answers. Questions that remain to be answered include:

  • Why don’t rabbit tendon stem cells make other types of cells when stimulated by platelet-rich plasma?
  • Is it possible to regulate exactly how many tenocytes are activated to get the perfect healing response (not too little and not too much)?
  • Can the results of this study be applied in humans?
  • What will happen when the new tendon tissue is stressed with movement or mechanical load? Will they hold up like normal, healthy (uninjured) tendons?
  • Can platelet-rich plasma injections be used effectively in older adults who have fewer stem cells to work with?