Mesenchymal stem cells (MSCs) are broadly applied in regenerative therapy to replace cells that are lost or impaired during disease. The low survival rate of MSCs after transplantation is one of the major limitations heavily influencing the success of the therapy. Unfavorable microenvironments with inflammation and oxidative stress in the damaged regions contribute to MSCs loss. Most of the strategies developed to overcome this obstacle are aimed to prevent stress-induced apoptosis, with little attention paid to senescence—another common stress reaction of MSCs. Here, we proposed the strategy to prevent oxidative stress-induced senescence of human endometrial stem cells (hMESCs) based on deferoxamine (DFO) application. DFO prevented DNA damage and stress-induced senescence of hMESCs, as evidenced by reduced levels of reactive oxygen species, lipofuscin, cyclin D1, decreased SA-β-Gal activity, and improved mitochondrial function. Additionally, DFO caused accumulation of HIF-1α, which may contribute to the survival of H₂O₂-treated cells. Importantly, cells that escaped senescence due to DFO preconditioning preserved all the properties of the initial hMESCs. Therefore, once protecting cells from oxidative damage, DFO did not alter further hMESCs functioning. The data obtained may become the important prerequisite for development of a new strategy in regenerative therapy based on MSCs preconditioning using DFO.

The prototypical receptor tyrosine kinase epidermal growth factor receptor (EGFR) is regulated by a set of its ligands, which determines the specificity of signaling and intracellular fate of the receptor. The EGFR signaling system is well characterized in immortalized cell lines such as HeLa derived from tumor tissues, but much less is known about EGFR function in untransformed multipotent stromal/stem cells (MSCs). We compared the effect of epidermal growth factor (EGF), transforming growth factor-$\alpha$ (TGF-$\alpha$) and amphiregulin (AREG) on physiological responses in endometrial MSCs (enMSC) and HeLa cells. In addition, using Western blotting and confocal microscopy, we studied the internalization and degradation of EGFR stimulated by the three ligands in these cell lines. We demonstrated that unlike HeLa, EGF and TGF-$\alpha$, but not AREG, stimulated enMSC proliferation and prevented decidual differentiation in an EGFR-dependent manner. In HeLa cells, EGF targeted EGFR for degradation, while TGF-$\alpha$ stimulated its recycling. Surprisingly, in enMSC, both ligands caused EGFR degradation. In both cell lines, AREG-EGFR internalization was not registered. In HeLa cells, EGFR was degraded within 2 h, restoring its level in 24 h, while in enMSC, degradation took more than 4–8 h, and the low EGFR level persisted for several days. This indicates that EGFR homeostasis in MSCs may differ significantly from that in immortalized cell lines.

The c-ErbB receptor family is a fundamental cell signaling system that regulates cell proliferation, motility, apoptosis, differentiation, and other key cellular functions. Overexpressed and mutated in some tumors, c-ErbB receptors play a pivotal role in their progression but are also present in many non-malignant cells, including those that are promising from the point of view of regenerative medicine, such as mesenchymal stromal cells (MSCs). The role of c-ErbB receptors in these cells is not clearly understood, and the data on their expression are sporadic. Therefore, the systemic characterization of c-ErbB receptor family expression in MSCs from a wide range of tissues is of high priority. Here, using RT-qPCR and Western blotting analysis, we evaluated the c-ErbB receptors expression pattern at the mRNA and protein levels in human MSCs isolated from six different tissues. We found that MSCs possess considerable EGFR and HER2 mRNA levels comparable to those in some malignant cells while showing trace HER3 and HER4 expression. However, EGFR but not HER2 was detected in MSCs at the protein level. We also show that the absence of HER2 protein is not associated with its rapid lysosomal degradation. We conclude that c-ErbB signaling in human MSCs is exclusively mediated by EGFR.

It is well-known that EGF binding to EGFR stimulates signal transduction and endocytosis, with the latter leading to lysosomal degradation of EGFR. However, the majority of data on the regulation of endocytosis have been obtained in tumor-derived cells. Here, we perform a comprehensive analysis of the role of endolysosome acidification in the regulation of endocytic pathway in tumor cells and in endometrial MSCs as a model of proliferating, undifferentiated, non-immortalized cells. Using QD-labeled EGF, the dynamics of co-localization of EGF-receptor complexes with endocytic markers in the control and upon inhibition of V-ATPase by Bafilomycin A1 (BafA1) were studied using confocal microscopy. Image analysis showed that in HeLa and A549 cells, BafA1 significantly slowed down EGFR entry into and exit from EEA1-positive early endosomes without disrupting passage through Rab7, CD63, and Lamp1 compartments, but rather shifting it to later times. In enMSCs, only a portion of EGF-containing endosomes entered the degradation pathway, and lysosomal delivery was significantly delayed. Unlike HeLa, in enMSC early endosomes, BafA1 increased the association of EGF-QDs with EEA1, suggesting a lower pH level, which is suboptimal for EEA1-dependent fusions. It is concluded that, unlike HeLa, enMSCs form a population of pH-independent endosomes containing activated EGFR for a long time.