Concentration of Neurotransmitter and Neurotrophic Factors in Platelet Rich Plasma.

Use of autologous platelet rich plasma (PRP) is emerging in a variety of clinical settings. Although the desired effects of PRP application vary across indications, the common mechanism of action is the up-regulation of the healing response at the site of application. This effect has largely been attributed to the release of cytokines from alpha-granules during platelet degranulation. Research has demonstrated elevated concentrations of a variety of cytokines in PRP samples when compared to baseline blood. To date, no researchthat quantifies the concentration of neurotransmitter and neurotrophic agents present in activated PRP samples has been reported. A number of these molecules have been reported to be present in the alpha and dense granules of platelets with release occurring upon platelet degranulation. Upon release, these molecules elicit actions related to the hemostatic, inflammatory, and reparative processes during the natural wound healing response. In the current study, a commercially available platelet concentrator (GPS II System, Biomet Biologics, Inc) was used to prepare PRP from whole blood samples obtained from 9 healthy subjects. PRP and whole blood samples from each subject were analyzed using a hematology analyzer (Cell Dyn 3700, Abbot Laboratories) for cellular content and then activated with a bovine thrombin/calcium chloride solution. Following a 10-minute incubation, the activated samples were centrifuged for 5 minutes and the resultant serum was collected and assayed for serotonin, adrenaline, noradrenaline, dopamine, and brain derived neurotrophic factor (BDNF) using commercially available ELISA kits. Platelet concentration averaged 196x10³ platelets/ml in the baseline samples and 1230 x10³ platelets/ml in the PRP samples, a 6.28 fold increase. Serotonin serum levels increased 4.48 fold (base=201.9 pg/ml, PRP=904.6 pg/ml), noradrenaline serum levels increased 3.02 fold (base=286 pg/ml, PRP=863 pg/ml), and BDNF serum levels increased 3.06 fold (base=3.49ng/ml, PRP=10.6 ng/ml). Adrenaline results were highly inconsistent, a factor attributed to the potential of glandular release in response to the blood draw stick. Dopamine concentrations were not detected in any samples using an ELISA with a sensitivity of 100 pg/ml. This study confirms the presence of elevated neurotransmitter and neurotrophic concentrations in activated PRP samples when compared to corresponding base samples. Further studies are necessary to elucidate the role these elevated concentrations contribute in the up-regulation of the wound repair process reported during the clinical application of PRP.