Activation of platelet-rich plasma using soluble type I collagen

Abstract

Purpose: Platelet-rich plasma (PRP) has recently been found to be a useful delivery system for growth factors important to oral tissue healing. But application of PRP in a liquid form to a wound site within the oral cavity can be complicated by significant loss of the PRP into the surrounding oral space unless gelation through the clotting mechanism is accomplished. Gelation is currently accomplished using bovine thrombin; however, rare but serious complications of this method have led to the search for alternative clotting mechanisms, including the use of soluble collagen as a clotting activator. In this work, our hypothesis was that soluble type I collagen would be as effective as bovine thrombin in causing clotting of the PRP and stimulating growth factor release from the platelets and granulocytes.

Materials and methods: PRP from human donors was clotted using type I collagen or bovine thrombin. Clot retraction was determined by measuring clot diameters over time. The release of platelet-derived growth factor (PDGF)-AB, transforming growth factor (TGF)-beta1, and vascular endothelial growth factor (VEGF) from both types of clots was measured over 10 days using enzyme-linked immunosorbent assasy.

Results: Clots formed using type I collagen exhibited far less retraction than those formed with bovine thrombin. Bovine thrombin and type I collagen stimulated similar release of PDGF-AB and VEGF between 1 and 10 days; however, thrombin activation resulted in a greater release of TGF-beta1 during the first 5 days after activation.

Conclusions: The use of type I collagen to activate clotting of PRP may be a safe and effective alternative to bovine thrombin. The use of collagen results in less clot retraction and equal release of PDGF-AB and VEGF compared with currently available methods of clot activation.

Figures

Figure 1

Clot Retraction of bovine thrombin activated clots and Type I collagen activated clots. The thrombin-PRP clots had significantly greater retraction within the first twenty four hours than the clots activated with Type I collagen(133 +/− 1.7 mm2 vs 74 +/− 23 mm2; mean +/− st dev, repeated measures ANOVA, p < 0.003). Points represent the average value at each time point, error bars represent the standard deviation for each group (n=4) at each time point.

Figure 2

PDGF-AB release from thrombin and collagen PRP clots at time points greater than 24 hours. No significant difference was observed between groups at these later time points (p > 0.15). Points represent the average value at each time point, error bars represent the standard deviation for each group (n=4) at each time point.

Figure 3

TGF-β1 release from thrombin and collagen PRP clots at time points between 12 hours and 10 days. A significant difference was observed between groups at all time points (repeated measures ANOVA, p

Figure 4

VEGF release in pg/hour from thrombin and collagen PRP clots at time points between 12 hours and 10 days. No significant difference was observed between groups, likely due in part to a relatively large variation in release between patients (repeated measures ANOVA, p > 0.15). Points represent the average value at each time point, error bars represent the standard deviation for each group (n=4) at each time point.