Sample preparation technique and white cell content influence the detectable levels of growth factors in platelet...

Autologous platelet concentrate (PC) is applied locally to improve wound healing and tissue repair. Previous measurements of the growth factor content of platelets have given conflicting results. To date, there is no information on the influence of different preanalytical sample-preparation methods on the detectable amount of growth factors.

We measured the level of growth factors in PCs obtained by plateletpheresis and by leukapheresis. We subjected aliquots of these components to six different preparation methods: freezing/thawing once or twice; dissolution in 0.5% Triton-X-100; and clot formation by the addition of calcium and thrombin with subsequent incubation for 1 h, for 24 h, or for 1 h followed by freezing and thawing.

In samples dissolved in Triton-X-100, higher levels of growth factors were detected than in the other specimens. In comparison to clot formation, freezing and thawing platelets twice was equivalent with respect to the release of platelet-derived growth factor (PDGF) but superior with respect to the release of transforming growth factor-beta1 (TGF-beta1). Overall, mean levels of 4.77 x 10(-16) g of PDGF-AB, 2.2 x 10(-17) g of PDGF-BB, and 2.41 x 10(-16) g of TGF-beta1 were found per single human platelet in white blood cell (WBC)-poor samples dissolved in Triton-X-100.

Dissolving PC in Triton-X-100 releases maximum quantities of growth factors from platelets. The release of each growth factor by any sample preparation method should be investigated and interpreted separately. The preanalytical sample-preparation method, as well as the platelet and WBC content, influence the measurable levels of growth factors in PCs. The results implicate the need to correct, considerably upwards, previous estimations of the PDGF content of platelets.