» » He’ll reply you that PRP is damn good working (a full head of hair
» » – what did you thought?
» I won’t be asking him a dumb question like ‘is it good’.
Ok. The following represents the current scientifically-known REALITY:
Year : 2010
William M Parsley1, David Perez-Meza2
1 Department of Dermatology, University of Louisville Medical Center, Louisville, Kentucky, USA
2 Plastic Surgery and Hair Transplant Surgery, Mexico City, Mexico, USA
Wound healing occurs as a sequential cascade of overlapping processes and requires the coordinated completion of a variety of cellular activities. Each step during the process is orchestrated by varying levels of many growth factors and by differential expression of their receptors. Growth factors are the engines, or modulating factors, that drive wound healing. ,,, Beginning in the 90s, polypeptide growth factors have emerged as the “Holy Grail” in wound repair. Platelets release large amounts of platelet-derived growth factor (PDGFaa, PDGFbb and PDGFab), transforming growth factor beta (TGFβ1 and β2), epidermal growth factor (EGF) and VEGF. The circulating platelet participates in natural wound healing based on its number in circulating blood. It further enhances wound healing by virtue of its concentration as Platelet-rich plasma (PRP).
PRP is an autologous concentration of human platelets in a small volume of plasma that has a higher platelet concentration (4-7-times) above baseline. PRP is obtained from the patient’s own blood after processing in an automated centrifuge.  Manual centrifuges are not recommended, not only due to their potential for product contamination but also due to their decreased efficiency in platelet recovery (30-70%) as compared to automated devices.  In 2007, the FDA approved the use of automated centrifuges for the preparation of growth factors to be used in chronic ulcers of diabetic patients.
There are also several reports demonstrating that the content of growth factors in PRP can vary tremendously, depending on the automated system used. Variations in key properties of the PRP, including platelet concentration, type of clot activator, using or not using a clot activator, etc., may markedly influence the different biological effects.
PRP has been used in the past in plastic surgery, dental surgery, general surgery, neurosurgery, orthopedic surgery, etc. ,, to reduce bleeding, swelling, prevent infection and to speed up the wound-healing process. The application of PRP in surgery has produced conflicting results - positive in some publications , and negative results in others. , It appears that PRP probably has a greater effect in chronic wounds, compromised wounds, poor vascularized tissue or infection.
Platelet-poor plasma, which is obtained during the separation and concentration process, does not contain growth factors and can be used only as a sealant or haemostatic agent (fibrin glue).
Perez-Meza et al., in part 1 of their growth factors study, , found that growth factors appear to play a key role in the wound-healing process and revascularization of the hair graft following HTS.
There are only two hair growth and survival studies using PRP in HTS.
In the first one, Perez-Meza et al. studied, used automated centrifuges and applied PRP in the donor and recipient area, including a graft storage study. They included 10 patients for the wound-healing study and three of them for the hair-survival study. The graft-survival study areas were selected; three boxes (1 cm² each) were marked in each side of the scalp for the PRP study and the placebo control study, respectively. Twenty sites were made using a 1.3 Minde blade, 4 mm deep. Two hair FUs were placed. The grafts of the PRP group were preserved in the PRP solution (non-activated) and soaked in PRP gel 10’ (activated) before placing. At 1-year follow-up, hair counts were similar between the two groups. At the ISHRS 2005 meeting, Sydney, Australia, Perez-Meza D presented the results. 
In 2005, Uebel performed the second study using a manual centrifuge. He included 23 patients. Two areas (2.5 cm²) each were marked in the scalp and planted at 20 g/cm 2 . At 1-year, the area treated with PRP demonstrated a yield of 18.7 FU/cm² vs. 16.4 FU/cm² of the placebo group, an increase in follicular density of 15.1%.  . Further controlled studies including more patients and automated devices are needed.
So draw your own conclusions …