The protective effects of conditioned media from human mesenchymal stem cells against Methylglyoxal-mediated injury of cultured endothelial cells

Poster by Maram Hasan and Abdelali Agouni (Qatar University)

Background: Diabetes is highly prevalent worldwide and is associated with several complications that predispose to a high risk of mortality. Endothelial dysfunction is a hallmark cellular process associated with diabetes. Mesenchymal stem cells (MSCs) possess specific properties including the inhibition of apoptosis, oxidative stress, and secretion of trophic factors. These unique properties prompted us to investigate the effect of MSCs conditioned medium (MSCs-CM) on preventing the noxious effects of methylglyoxal (MGO), a precursor of advanced glycated end-products (AGEs) that play a key role in the pathophysiology of diabetes, on endothelial cells with respect to oxidative stress and cell survival. Additionally, we investigated certain cellular alterations associated with oxidative damage such as the Nrf2 pathway, as a major system involved in cellular defense mechanisms against oxidative stress.

Objective: To assess the protective effect of (MSCs-CM) against MGO-mediated injury of cultured endothelial cells in terms of ROS generation, cell survival, and Nrf2 antioxidant pathway.

Methods: Endothelial EA.hy926 cells were exposed or not to MGO(1mM) in the presence or absence of (MSCs-CM)(50% in α-MEM). Then, oxidative stress was quantified by DCF-DA assay and cell viability and apoptosis quantification via Annexin V & caspase 3/7 activity were assessed using flowcytometry. The activation of the Nrf2 pathway was evaluated by western blot and qPCR methods.

Results: Our results showed that MGO (1 mM) induced substantial ROS generation in EA.hy926 cells after 6 hours of exposure as measured by DCF-DA assay; this effect was attenuated by treating cells with MSCs-CM (50%). Moreover, Ea.hy926 cell viability was significantly reduced by 35% when treated with MGO; while cells treated with MSCs-CM (50%) were protected. We also investigated the protective effects of MSCs-CM against MGO-induced apoptosis in EA.hy926 endothelial cells using the Annexin V/propidium iodide assay and the quantification of caspases 3/7 activity. Our findings showed a significant protective effect of MSCs-CM (50%) on MGO-mediated cell death and caspases 3/7 activation in endothelial cells.

Nrf2 controls the transcription of several ROS-detoxifying enzymes including NQO1, and GSTA gene expression, thus the effect of MSCs-CM (50%) on the mRNA expression of Nrf2, NQO1, and GSTA was assessed in MGO-injured cells. We noted that only the mRNA expression of Nrf2 was increased in cells treated with MSCs-CM (50%). At the protein expression level, our results demonstrated that MSCs-CM (50%) enhanced the expression of the detoxifying NQO1in MGO-injured cells.

Conclusion: Altogether, these findings underscore the promising therapeutic potential of MSC-CM in fighting oxidative stress and molecular alterations associated with AGEs, a major molecular hallmark of diabetes, in endothelial cells. The protective effects of MSC-CM against endothelial dysfunction, the first step in atherogenesis, may contribute to the reduction of the risk of cardiovascular complications associated with diabetes.