Cross-Species Comparison of Platelet Proteomes Reveals Developmentally Regulated Metabolic and Inflammatory Changes

• Developmental changes in neonatal vs. adult platelet proteins account for functional differences. • Cross-species comparison using machine learning can define key pathways with conserved developmental differences. Liberal transfusions of adult platelets increase preterm infant morbidity and mortality. This harm may be due to functional differences between neonatal and adult platelets. Preclinical murine models remain essential to investigate the underlying mechanisms. A prerequisite to developing and using these models is a cross-species comparison of developmentally regulated molecules in platelets. The objective of this study was to define proteins and biological pathways that differ between neonatal and adult platelets in mice, and to ascertain developmentally regulated molecules and pathways that are consistent across murine and human platelets. In comparing proteomes from resting murine and human platelets, we identified a consistent increase in inflammatory proteins in adult platelets across species, including β2M and CXCL12. Other markers for platelet function differed between species, including P-selectin, which was increased in adult murine platelets but did not differ over development in humans. To better elucidate developmentally regulated pathways across species, we employed sparse principal component and machine learning-based approaches. These revealed developmentally regulated growth factors, inflammatory signaling pathways, and metabolic changes that were consistent across species, as well as some discrepant molecules and signaling pathways. Our results clarify molecular differences in neonatal and adult platelets with direct relevance for altered reactivity and inflammatory functions. This approach will help bridge understanding between animal models and human biology to investigate the impact of developmental differences in platelet biology on neonatal transfusion. These methods can be similarly used in other biological systems to improve the translatability of preclinical research.