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The potential for using PRP to promote healing and hair growth after hair transplantation is centered in three functional applications:
1. To preserve and enhance hair follicle viability during and after hair transplantation;
2. To promote and enhance tissue repair and healing after hair transplantation; and,
3. To reinvigorate dormant hair follicles and stimulate new hair growth.
To Preserve and Enhance Hair Follicle Viability
Between the time that hair follicles are removed from a donor area of the scalp and transplanted into a recipient area, they are subject to damage from several causes:
• Dehydration if the donor follicles are inadequately moistened between the times of removal and transplantation;
• Oxygen and nutrient starvation due to being removed from blood supply during the harvest-to-transplantation time period;
• Temperature and acid/alkaline changes in the follicle environment; and,
• Revascularization injury when the donor follicles are transplanted to the recipient site and must re-adapt to having a blood supply.
A common approach to maintaining donor hair follicle viability during the transition period is to keep them in a storage solution that provides a protective environment of appropriate temperature, chemical balance and nutrient supply. Recent research has indicated that addition of PRP to the storage solution improves follicle viability during and after transplantation, enhances post-transplantation tissue healing and promotes hair growth in transplanted follicles. An approach advocated by some investigators is to bathe the donor hair follicles in activated PRP just prior to transplantation.
Investigators have reported that PRP promotes hair growth from follicles by the action of platelet growth factors on hair follicle stem cells. The platelet growth factors induce follicle stem cells to shift from a dormant state to an active state that starts the process of hair production. While investigators have reported such activity, no advertised claims of PRP efficacy in promoting hair growth can be made because there has been no FDA approval that would allow such claims to be made.
To Promote and Enhance Tissue Repair and Healing
In activity promoting tissue repair and healing after injury of surgery, the growth factors stored in platelets are released at a site of tissue injury, promoting tissue repair and healing. Individual growth factors such as PDGF have been used by surgeons to promote wound healing in hospitalized surgical patients. The rationale for using PRP in outpatient surgical hair restoration is to use the full array of platelet-associated growth factors to promote healing and minimize scar formation, as well as to promote maximum hair growth in transplanted follicles.
A described method of applying PRP to scalp incisions is by injection of a PRP gel into the wounds at the time of wound closure. Clinicians and investigators using this procedure have described enhanced healing at the transplant site. These reports are usually of individual cases or of a small number of cases. Such reports do not meet definitions of clinical trials that would, for example, be required in the United States for seeking FDA approval of PRP use specifically in hair transplantation with claims of efficacy and safety. Some investigators suggest that PRP should not be used routinely in hair transplantation to promote healing, but might be of use in patients who have had previous injury or scarring at a transplant site. Investigators who oppose routine use of PRP in hair transplantation cite the need for additional data from well-designed clinical trials.
To Reinvigorate Dormant Hair Follicles
After noting enhanced hair growth of transplanted hair after use of PRP, investigators conducted a small study of PRP effect on dormant non-transplanted hair follicles. The study hypothesized that platelet growth factors can “wake up” dormant hair follicles and begin the production of new hair. PRP was applied after scalp skin was slightly injured to induce platelets to release growth factors at the injury site. Enhanced hair growth and hair diameter was noted over the next 4 months, with a fall-off in enhanced hair growth after 4 months
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