Thrombospondin‐1: a unique marker to identify in vitro platelet activation when monitoring in vivo processes

• Published in: Journal of thrombosis and haemostasis Vol. 8; no. 8; pp. 1809 - 1819
• Main Authors: STARLINGER, P., MOLL, H. P., ASSINGER, A., NEMETH, C., HOETZENECKER, K., GRUENBERGER, B., GRUENBERGER, T., KUEHRER, I., SCHOPPMANN, S. F., GNANT, M., BROSTJAN, C.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2010; Elsevier Limited
• Subjects: Adult; Aged; Blood platelets; cancer; Case-Control Studies; Drug therapy; Female; Humans; In Vitro Techniques; Male; marker; Middle Aged; Neoplasms - blood; Platelet Activation; Protein Isoforms; Proteins; Recombinant Proteins - chemistry; Temperature; Thrombospondin 1 - blood; Thrombospondin 1 - chemistry; thrombospondin‐1; Time Factors; Wound Healing
• ISSN: 1538-7933; 1538-7836; 1538-7836
• DOI: 10.1111/j.1538-7836.2010.03908.x

Background:  Measuring platelet activation in patients has become a potent method to investigate pathophysiological processes. However, the commonly applied markers are sensitive to detrimental influences by in vitro platelet activation during blood analysis. Objectives:  Protein isoforms of platelet‐derived thrombospondin‐1 (TSP‐1) were investigated for their potential to identify in vitro platelet activation when monitoring in vivo processes. Methods:  TSP‐1 was determined in plasma, serum or supernatant of purified platelets by ELISA and immunoblotting and was compared with standard markers of platelet activation. A collective of 20 healthy individuals and 30 cancer patients was analyzed. Results:  While in vitro platelet degranulation led to a selective increase in the 200‐kDa full‐length molecule, an in vivo process involving platelet activation such as wound healing resulted in the predominant rise of the 140‐kDa TSP‐1 protein. The physiological ratio of circulating TSP‐1 variants was determined and a cut‐off level at 1.0 was defined to identify plasma samples with artificial in vitro platelet activation exceeding the cut‐off level. In contrast, cancer patients known to frequently exhibit increased in vivo activation of platelets presented with a significantly decreased ratio of TSP‐1 variants as compared with healthy volunteers. Conclusions:  In comparison to standard platelet markers, TSP‐1 constitutes a sensitive and stable parameter suited to monitor in vitro platelet activation. The analysis of TSP‐1 protein isoforms further offers a valuable tool to reliably discriminate between in vitro and in vivo effects, to exclude variability introduced during blood processing and improve clinical monitoring.