The Sensitivity of Multipotent Mesenchymal Stromal Cells to Short-Term Hypoxic Stress In Vitro Depends on the Efficiency of Homotypic Communication through Gap Junctions

Abstract

Gap junctions (GJ) provide metabolic cooperation between cells through the direct exchange of cytoplasmic components. The authors analyzed the effect of short-term hypoxic stress on the efficiency of communication through the GJs in cultured multipotent mesenchymal stromal cells (MSCs) and characterized the sensitivity of MSCs to short-term hypoxic stress depending on the GJ function. Mitotically inactive MSCs were used in the experiments, in which the GJs were blocked with a specific inhibitor: carbenoxolone. The MSCs were continuously cultured at 20% O₂. Further, MSCs with blocked and working GJs were subjected to hypoxic stress (0.1%, 24 h). The efficiency of GJ communication was attenuated under hypoxic stress. The combined action of GJ inhibition and hypoxic stress was accompanied by an increase in ROS level as compared to the MSCs after hypoxic stress only. MSCs with blocked GJs were less sensitive to short-term hypoxic stress in comparison with MSCs integrated into the common network through working GJs. This was manifested in attenuation of hypoxia-induced angiogenic activity of MSCs. The angiogenic effects of conditioned medium from the MSCs with blocked GJs were almost two times less, which seems to be related to differences in the angiogenic mediators’ profiles: VEGF level decreased and FGF-2 level increased, while the monocyte chemoattractant protein 3 (MCP-3) level was unchanged. Thus, a decrease in the efficiency of direct MSCs–MSCs communication had a negative effect on mostly requested MSC activity, the ability to induce angiogenesis. It is concluded that blocking of GJ communication in MSCs is a negative event that impairs the coordination of MSCs’ response to microenvironmental factors, in particular hypoxic stress, and reduces their functional plasticity.