Morphology of platelets of newborns by using electron microscopy

Objective - to study the morphological features of platelets of newborns by using electron microscopy.

Materials and methods. Peripheral blood platelets of healthy newborns were studied by means of transmission electron microscopy (TEM) method. The sample included 50 healthy babies from the Clinical Perinatal Center of Saratov region born at a gestational age of 37-42 weeks with an assessment on the Apgar scale (1952) at the first minute of at least 7 points. After blood sampling, platelet-rich plasma (PRP) was obtained by centrifugation.

Results. As a result of the study, 3 forms of platelets were identified: 1. Inactive ones, rounded or more often oval-shaped, in which it is possible to see almost all intracellular structures being typical for platelets; 2. Activated forms that have long processes (pseudopods) and usually have no granules; 3. Transitional forms - apparently, platelets at the initial stages of activation: elements of their open tubular system are already expanding, and this leads to the appearance of vacuoles. However, they do not yet have a distinct rearrangement of the cytoskeleton, and, accordingly, long processes and a significant change in shape. Platelets of newborns are heterogeneous in morphofunctional state: most of them are represented by inactive forms 82(80-85)%, the smaller part includes activated 15(13-17)% and transitional forms 3(2-4)%. Platelet microparticles (PM) are platelet derivatives and are also variable in size and structure. They can be represented by simple vesicles without internal contents, or they can have secretory granules involved in the transmission of signaling information to other platelets and endothelial cells. In our study, several mechanisms of formation and separation of PM from “precursor platelets” were discovered, but their meaning is not yet fully understood and requires further study.

Conclusion. This study demonstrates the heterogeneity of the platelet population of newborns associated with their morphofunctional state. For convenience of description, three morphological classes of platelets have been devised. The hypothesis about possible mechanisms of PM formation has been formulated.

1. Ponomareva A.A., Nevzorova T.A., Mordakhanova E.R., Andrianova I.A., Litvinov R.I. Structural characterization of platelets and platelet-derived microvesicles. Cell and tissue biology. 2016;58(2):105-114 (in Russ.).

2. Budak Ya.U., Polat M., Huysal K. The use of platelet indices, plateletcrit, mean platelet volume and platelet distribution width in emergency non-traumatic abdominal surgery: a systematic review. Biochem Med (Zagreb). 2016;26(2):178-193. DOI: 10.11613/BM.2016.020

3. Gaetani E., Del Zompo F., Marcantoni M., Gatto I., Giarretta I., Porfidia A., Scaldaferri F., Laterza L., et al. Microparticles Produced by Activated Platelets Carry a Potent and Functionally Active Angiogenic Signal in Subjects with Crohn's Disease. Int J Mol Sci. 2018;19(10):2921. DOI: 10.3390/ijms19102921

4. McGinn C.M., MacDonnell B.F., Shan C.X., Wallace R., Cummins P.M., Murphy R.P. Microparticles: A Pivotal Nexus in Vascular Homeostasis and Disease. Curr Clin Pharmacol. 2016;11(1):28-42. DOI: 10.2174/1574884711666160122093527

5. Rautou P.E., Vion A.C., Amabile N., Chironi G., Simon A., Tedgui A., Boulanger C.M. Microparticles, vascular function, and atherothrombosis. Circ Res. 2011;109(5):593-606. DOI: 10.1161/CIRCRESAHA.110.233163

6. Reei M.C., Fustolo-Gunnink S.F., Bekker V., Fijnvandraat K.J., Steggerda S.J., Lopriore E. Thrombocytopenia in neonatal sepsis: Incidence, severity and risk factors. PloS one. 2017;12(10):e0185581. DOI: 10.1371/journal.pone.0185581

7. Thushara R.M., Hemshekhar M., Basappa K.K., Rangappa, K.S., Girish, K.S. Biologicals, platelet apoptosis and human diseases: an outlook. Crit Rev Oncol Hematol. 2015;93(3):149-158. DOI: 10.1016/j.critrevonc.2014.11.002