BACKGROUND: The trophic function is one of the important but insufficiently studied features of mesenchymal stromal cells (MSCs), their microvesicles (MVs), and plasma enriched with soluble platelet factors (PRPs), which ensure the viability of target cells.
AIM: To analyze the capability of MSCs, MVs, and PRP to affect the viability and spontaneous and activation-induced apoptosis of rat spleen lymphocytes during culturing in vitro.
MATERIALS AND METHODS: MSCs were isolated from the mononuclear cell fraction of the femoral bone marrow of Wistar rats using the plastic adhesion method. MVs were obtained from the conditioned medium of MSCs by centrifugation at 14,500 g. PRP was prepared by freezing/thawing rat peripheral blood platelet concentrate. Rat spleen lymphocytes were isolated on a density gradient of 1.077 g/cm3. The viability and degree of lymphocyte apoptosis in vitro were assessed by flow cytometry for 7-AAD incorporation and binding to annexin V.
RESULTS: The presence of MSCs at 10 and 20% concentrations caused an increase in the number of living intact and PMA-activated lymphocytes by the end of 3-day in vitro cultivation. Compared with controls, the amount of necrotic cells decreased 8.3–13.5 times, and the number of apoptotic cells decreased 2.3–4.0 times, mainly due to lymphocytes at the late stage of apoptosis. MVs of MSCs at the indicated concentrations did not significantly affect the viability of lymphocytes cultured in vitro but reduced the level of apoptosis of intact and PMA-activated lymphocytes by 3.6 (р=0.03) and 4.8–5.2 (р=0.048; р=0.03) times respectively. Studies have shown that 1.25% rat PRP has a growth-stimulatory activity against MSCs but not against lymphocytes cultured in vitro. In the culture of intact lymphocytes, PRPs did not significantly affect cell viability with a slight decrease (2.7–2.9 fold, p 0.05) in the number of necrotic cells. In the culture of PMA-activated lymphocytes, 1.25–2.50% PRP increased the number of living cells by 1.6–2.2 times (р=0.002; р=0.01) and the number of necrotic cells by two times (р=0.02).
CONCLUSION: MSCs, MVs of MSCs, and PRP, in decreasing order, enhanced the viability of rat spleen lymphocytes and suppressed late apoptosis during in vitro cultivation. Lymphocytes activated by phorbol myristate acetate are more sensitive to their vital action compared with resting cells.
