Stimulus‐dependent release of tissue‐regenerating factors by equine platelets

Abstract

Supernatants collected from coagulated platelets could be an alternative treatment to PRP.

Activation of Equine Platelet‐Rich Plasma: Comparison of Methods and Characterization of Equine Autologous Thrombin

“…The most commonly described human PRP activation methods use either CaCl 2 or thrombin as the main platelet stimulants. Freeze thawing of PRP is also occasionally used, but our results and those of others 42 indicate that other methods are more effective for eliciting PDGF release. Extracellular ionized calcium serves as a cofactor for the activation of almost every coagulation protein in the cascade, 43 resulting in indirect platelet activation.…”

“…The clot is useful in human reconstructive surgery because it serves as a scaffold and “provisional matrix” in areas of tissue deficit, allowing the surgeon to sculpt it into a defect and combine it with other scaffold substrates such as bone graft . Platelet‐rich fibrin clots are purported to provide long‐lasting growth factor release, creating a “depot effect” within the treated site, but experimental data on growth factor content of the clot releasates suggests that maximal release actually takes place by 1–6 hours after clot formation, with little subsequent release . We evaluated growth factor content of not only the releasate but also the clot itself, and found that the release versus the retention of growth factor within those clots depended upon the activation method employed.…”

“…Given that Triton causes thorough dissolution of membranes, that the number of monocytes in PRP is quite small, and that the difference between the positive control and thrombin‐activated content is quite large (∼ 2.7‐fold), the third explanation is the most likely. This phenomenon is called “signal‐dependent translation,” and has been recently suggested to occur in equine platelets . The implication of this process is that platelets can release not only the presynthesized growth factor contained in their alpha granules, but are capable of producing more growth factor after maximal activation.…”

“…10 Platelet-rich fibrin clots are purported to provide long-lasting growth factor release, 17 creating a "depot effect" within the treated site, but experimental data on growth factor content of the clot releasates suggests that maximal release actually takes place by 1-6 hours after clot formation, with little subsequent release. 39,42,60 We evalu-ated growth factor content of not only the releasate but also the clot itself, and found that the release versus the retention of growth factor within those clots depended upon the activation method employed. Thrombin activation resulted in an even distribution of PDGF between the clot and clot releasate, while calcium chloride activation resulted in the majority of PDGF being liberated from the clot into the releasate.…”

“…This phenomenon is called "signal-dependent translation," and has been recently suggested to occur in equine platelets. 42 The implication of this process is that platelets can release not only the presynthesized growth factor contained in their alpha granules, but are capable of producing more growth factor after maximal activation. As originally reported in human platelets, 63 new protein synthesis was evident 5-15 minutes after platelet activation by low-dose (0.1 U/mL) thrombin.…”