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

Abstract

Summary. 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.

No evidence for increased platelet activation in patients with hepatitis B- or C-related cirrhosis and hepatocellular carcinoma

“…We did, however, detect substantially decreased platelet activatability in patients. Based on previous studies on the platelet activation status in different types of cancer, we anticipated that the platelet activation status in patients with cirrhosis who developed HCC would be increased in comparison to patients with cirrhosis without HCC [32][33][34][35][36][37][38]. However, our results indicate that patients with cirrhosis and HCC might not have a relative hyperreactivity of their primary hemostatic system compared to patients with cirrhosis without HCC.…”

The prognostic value of plasma thrombospondin-1 concentrations after aneurysmal subarachnoid hemorrhage

“…Actually, it is also present in other cells such as leukocytes and endothelial cells [9][10][11]. TSP-1 has received increased attention because of its involvement in synaptogenesis, angiogenesis, platelet aggregation, inflammatory response, and wound repair [12][13][14][15][16][17]. In the central nervous system, reactive astrocytes can produce TSP-1 [18,19].…”

Neoadjuvant bevacizumab persistently inactivates VEGF at the time of surgery despite preoperative cessation

“…Platelet-poor plasma was prepared as previously described (Brostjan et al , 2008; Starlinger et al , 2010b, 2011). Briefly, blood (10 ml) was drawn into prechilled CTAD tubes containing sodium citrate, theophylline, adenosine, and dipyridamole, was kept on ice and further processed within 30 min.…”