Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Schlagenhauf, A.
Dissection of platelet peculiarities in the newborn
[ Dissertation ] Medical University of Graz; 2013. pp. 125
[OPEN ACCESS]
FullText
- Autor*innen der Med Uni Graz:
- Schlagenhauf Axel
- Betreuer*innen:
- Birner-Grünberger Ruth
- Fauler Günter
- Muntean Eugen
- Altmetrics:
- Abstract:
- Background: Neonatal platelets show distinct functional deficiencies when compared with adult platelets. In-vitro platelet aggregation is impaired with many commonly used agonists. On the other hand, newborns clinically exhibit a well-performing primary hemostasis, and neonatal platelets are functionally involved in ductus arteriosus closure after birth. We wanted to investigate the specific attributes of neonatal platelets, and the special role they play in primary and secondary hemostasis during this first period of life, and to investigate a potential developmental mismatch of adult platelet transfusions with the neonatal hemostatic system. A major part of this thesis constitutes a comparative study of the neonatal platelet membrane. Methods: Thrombin receptors (PAR1, PAR4, GPIb¿) in platelets were analyzed from umbilical cord blood and from venous adult blood using Western blot analysis in correlation with platelet aggregation data. The impact of adult platelets on the neonatal hemostatic system was evaluated using calibrated automated thrombography. Platelet membrane proteins were enriched by aqueous two-phase partitioning. After protein digestion neonatal and adult peptides were differently tagged using dimethyl. Prefractionation was done using strong cation exchange chromatography and peptides were analyzed with LC-MS/MS. Proteins were identifed by database matching, and over- or underexpressed proteins in neonatal samples were subjected to enrichment and network analyses. Plasma levels of prostaglandin E2 were quantified using GC-MS and a potential inhibiting effect was investigated using ow cytometric analysis of the responsible EP4 receptor, platelet aggregation testing and ELISA measurements of intracellular cAMP concentrations. Results: We found significantly lower levels of PAR1 and PAR4 in neonatal as compared to adult samples, and a correlation with aggregation data. Thrombin generation measurements in neonatal plasma with adult platelets from concentrates resulted in shortened dynamic parameters. Analysis of the platelet membrane proteome resulted in overall identification of 939 proteins with 146 underexpressed and 104 overexpressed features in neonatal samples. Analysis of underexpressed proteins in neonatal samples revealed underrepresentation of cytoskeletal proteins in neonatal samples, and less interactivity, while overexpressed proteins exhibited a high level of interaction. Additional network analysis of overexpressed proteins revealed a clusters of platelet adhesion molecules, G-proteins, andvesicular proteins. Prostaglandin E2 levels were substantially higher in cord blood than in adult samples. Spiking of adult samples with prostaglandin E2 revealed an observable reduction in ADP and collagen mediated platelet aggregation accompanied by an increase in intracellular cAMP concentration. Conclusion: Function of neonatal platelets is not generally impaired. They exhibit certain up- and downregulations to handle specific tasks. Hypoaggregability to thrombin is adequate for the interplay with the neonatal plasmatic coagulation system. Enrichment of platelet adhesion molecules in neonatal platelets suggest a specific gain of function to fulfill a role in ductus arteriosus closure. Prostaglandin E2 levels peak at birth providing a protective inhibitory stimulus for neonatal platelets, followed by a steep decline. These peculiarities of neonatal platelets and their interplay with the neonatal plasmatic coagulation system need to be taken into account in future treatment strategies for newborns.