The Expression of Cell Cycle Cyclins in a Human Megakaryoblast Cell Line Exposed to Simulated Microgravity.

The study of the physiological and pathophysiological processes under extreme conditions facilitates a better understanding of the state of a healthy organism and can also shed light on the pathogenesis of diseases. In recent years, it has become evident that gravitational stress affects both the whole organism and individual cells. We have previously demonstrated that simulated microgravity inhibits proliferation, induces apoptosis, changes morphology, and alters the surface marker expression of megakaryoblast cell line MEG-01. In the present work, we investigate the expression of cell cycle cyclins in MEG-01 cells. We performed several experiments for 24 h, 72 h, 96 h and 168 h. Flow cytometry and Western blot analysis demonstrated that the main change in the levels of cyclins expression occurs under conditions of simulated microgravity after 96 h. Thus, the level of cyclin A expression showed an increase in the RPM group during the first 4 days, followed by a decrease, which, together with the peak of cyclin D, may indicate inhibition of the cell cycle in the G2 phase, before mitosis. In addition, based on the data obtained by PCR analysis, we were also able to see that both cyclin A and cyclin B expression showed a peak at 72 h, followed by a gradual decrease at 96 h. STED microscopy data also confirmed that the main change in cyclin expression of MEG-01 cells occurs at 96 h, under simulated microgravity conditions, compared to static control. These results suggested that the cell cycle disruption induced by RPM-simulated microgravity in MEG-01 cells may be associated with the altered expression of the main regulators of the cell cycle. Thus, these data implicate the development of cellular stress in MEG-01 cells, which may be important for proliferating human cells exposed to microgravity in real space.

Investigation of Platelet Apoptosis in Patients after Surgical Myocardial Revascularization.

Platelets are one of the main participants in vascular accidents in cases of coronary heart disease (CHD). In this study, we sought to detect platelet apoptosis in patients with coronary artery disease who underwent scheduled myocardial revascularization surgery. To identify apoptotic events, we analyzed phosphatidylserine (PS) expression on the surface of platelets and mitochondrial membrane potential (ΔΨm) by flow cytometry in two groups of 30 patients aged 45-60 years: Group 1-patients before myocardial revascularization surgery and group 2-patients after myocardial revascularization surgery. The control group consisted of 10 healthy volunteers aged 45-60 years. According to our data, the percentage levels of PS expression in patients greatly decreased after surgery. We confirmed platelet apoptosis by recording depolarization of ΔΨm in pre- and postoperative patients. ΔΨm readings were considerably improved after surgery. Our data indicated that the functional parameters of platelets in patients with coronary heart disease differed from the characteristics of platelets in patients who underwent myocardial revascularization, and from those of patients in a control group. Future studies of platelet phenotypic characteristics and platelet apoptosis biomarkers should greatly advance our understanding of the pathophysiology of coronary heart disease, and further promote the development of methods for predicting adverse outcomes after surgery.