**3. Definition of plasma growth factors**

Growth factors are obtained in an autologous way from the whole blood of the same patient with the aim of reducing the possibility of producing hypersensitivity effects or transmission of infectious diseases during their application. It is called leukocyte-rich plasma or (PRL) to the suspension of the mononuclear fraction or buffy coat in a quantity of patient's serum with a count higher than 20,000/ mm<sup>3</sup> ; while platelet-rich plasma (PRP) would be that platelet concentrate suspension in a small amount of patient serum whose count exceeds 1000,000/mm<sup>3</sup> of platelets. The optimum pH to obtain both cellular fractions is estimated between 6.5 and 6.7 at a temperature of 22°C. Recent studies, such as the one led by the group of Dr. Alcaraz et al., have observed the predominance of PDGF and IGF-like plasma growth factors in platelet-rich suspensions, while other growth factors such as VEGF or TGF would predominate in those final concentrates rich in leukocytemononuclear cells [4–6] (**Table 2**).


**Table 2.** Levels of growth factors and cell count in peripheral blood and PRP.
