11 Plasma-Rich Protein and ACell

Fabio Rinaldi

Summary

Platelet-rich plasma (PRP) has emerged as a new treatment for a large number of medical and dermatological conditions. PRP may be a simple, cost-effective, and feasible treatment option for hair loss, and it can be regarded as a valuable adjuvant treatment method for patients with androgenetic alopecia, female pattern hair loss, alopecia areata, and hair transplant surgery. Growth factors and cytokines derived from platelets act on specific receptors located in stem cells in the bulge area, thus stimulating the development of new follicles and promoting neovascularization. PRP is also posited to increase the proliferation of DP cells and stimulate extracellular signal-regulated kinase and Akt signaling. Fibroblast growth factor 7 and beta-catenin, which are potent stimuli for hair growth, were upregulated in DP cells. In mice, the injection with activated PRP induced a faster telogen-to-anagen transition than in the control group. PRP has emerged as a new treatment option in dermatology in general, and preliminary evidence suggests that it may also play a significant role in hair restoration.

Medical literature offers a wide number of scientifically reliable articles on platelet-rich plasma (PRP): a PubMed search (February 2017) has retrieved more than 13,351 references, with more than 668 additions in 2016. Scientific evidence has been published regarding the use of PRP for tissue regeneration in many fields including orthopedics, ophthalmology, plastic, maxillofacial, dental surgery,1 as well as a growing number of applications for dermatology and aesthetic medicine.

In the trichological field, several in vitro studies have also shown that platelet growth factors exert an action on the dermal papilla and hair follicles.^2,3

The most important cellular components of PRP are platelets, which are responsible not only for the secretion of growth factors and chemokines but also for the regulation of inflammatory reactions by expressing chemokine receptors. Platelets release a wide array of growth factors, which are listed in Table 11.1.⁴

Table 11.1 Platelet-rich plasma growth factors and their action

As growth factors are contained in the alpha granules within platelets, their concentration in PRP is also significantly higher than their concentration in the circulating blood. The study by Eppley et al⁵ clearly demonstrates that the concentration of platelet-derived growth factors is significantly higher in PRP compared with baseline and with the concentration of the same growth factors in platelets that are activated and physiologically degranulated during normal wound healing processes.

Activated platelets also secrete a large array of additional factors from the α-granules, including PF-4, osteocalcin, osteonectin, fibrinogen, vitronectin, fibronectin, and thrombospondin-1. These factors are also likely to play a significant role in the different effects of PRP.

Furthermore, PRP contains thrombin, which directly triggers the mitogenesis and secretion of growth factor, and several antimicrobial peptides which enhance the antibacterial properties of PRP. However, research is likely to discover some additional factors which may mediate the effects of PRP.

The rationale of the use of PRP is based on the well-known effects of plasma growth factors and cytokines which lead to cell proliferation and migration. In particular, growth factors can affect the mechanism of the “hair clock cycle” and scalp inflammation as reported in Table 11.2.

Table 11.2 Effects of platelet growth factors on hair follicles and scalp

The hair follicle is a cylindrical epithelial structure, which grows into the dermis and subcutaneous fat and enlarges at the base forming the hair bulb that surrounds the mesenchyme-derived dermal papilla.⁶ The hair-follicle bulge area is a structure in the outer root sheath at the level of the insertion site of arrector pili muscle (APM) above the insertion site of APM and below the sebaceous gland,⁷ where stem cells can provide an accessible source of undifferentiated, highly proliferative, multipotent stem cells. In the early anagen phase, signals from the dermal papilla stimulate transient amplifying cells (β-catenin) to proliferate and differentiate as well as to form a new hair bulb.

Some in vitro studies have demonstrated that PRP can stimulate the dermal fibroblasts of the dermal papilla8 and are involved in many cellular activities such as proliferation, differentiation, stem cell stimulation, and regulation of pro/anti-inflammatory and anabolic/catabolic processes. Several authors have shown that the antiapoptotic activity of PRP can induce hair growth and improve cell survival through the activation of Akt and ERK signaling pathways. PRP can also stimulate the transcriptional activity of β-catenin regulatory protein levels.⁹ This effect was observed both in an in vitro and in vivo study which demonstrated the prolongation of the anagen phase and the shortening of the telogen phase in response to platelet growth factors. PRP upregulates vascular endothelial growth factor (VEGF) and platelet derived growth factor, thus increasing perifollicular vascular permeability and improving the supply of blood and nourishment to hair follicles. Fibroblast growth factor 7 and insulin-like growth factor 1 act by normalizing the scalp milieu and reducing dermal fibrosis.

11.2 Preparation of Platelet-Rich Plasma

Practitioners draw peripheral blood, ranging in quantity from 10 to 120 mL. There are many systems available to produce PRP and some practitioners use a single spin, while others use a double spin. It is very important to know the various parameters and percentages of components in the PRP.

The author collects 36 mL of whole blood and divides it into four vials (9 mL each), each containing 1.5 mL of ACD-A anticoagulant solution. Blood is processed in a centrifuge (600 spin/min, 265 g for 8 minutes) to obtain PRP, which contains platelet concentration five or seven times higher than the baseline value. From 36 mL of blood, 7.3 mL of PRP (average) and 10.6 mL of PPP (average) are obtained. PRP can be stored for 24 hours with no special precautions, but it is generally used immediately. PRP must be frozen to be stored for a longer period. Usually, only the PRP fraction is used (Video 11.1).

11.3 Activation of Platelet-Rich Plasma

The activation of PRP before administration helps stimulate the degranulation of platelets to release growth factors from α-granules. The activation of PRP before performing a treatment is included in several protocols, and it is usually carried out by adding calcium chloride (CaCl₂) or/and thrombin. Cole has also produced a new system for activation using sonification. Some clinicians prefer to use PRP in its resting form, relying on the spontaneous activation of platelets by the native collagen in the dermis. There is no actual evidence of the best method to activate PRP, and the choice of whether or not, and how, to activate PRP is the physician’s decision. The author prefers to activate PRP by adding CaCl₂ (5% of PRP collected). Once it has been activated, PRP must be used within 15 minutes as growth factors are released in a short time.

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