Human Embryonic Stem Cells Acquire Responsiveness to TRAIL upon Exposure to Cisplatin

Sensitivity of Human Induced Pluripotent Stem Cells and Thereof Differentiated Kidney Proximal Tubular Cells towards Selected Nephrotoxins

Proximal tubular epithelial cells (PTEC) are constantly exposed to potentially toxic metabolites and xenobiotics. The regenerative potential of the kidney enables the replacement of damaged cells either via the differentiation of stem cells or the re-acquisition of proliferative properties of the PTEC. Nevertheless, it is known that renal function declines, suggesting that the deteriorated cells are not replaced by fully functional cells. To understand the possible causes of this loss of kidney cell function, it is crucial to understand the role of toxins during the regeneration process. Therefore, we investigated the sensitivity and function of human induced pluripotent stem cells (hiPSC), hiPSC differentiating, and hiPSC differentiated into proximal tubular epithelial-like cells (PTELC) to known nephrotoxins. hiPSC were differentiated into PTELC, which exhibited similar morphology to PTEC, expressed prototypical PTEC markers, and were able to undergo albumin endocytosis. When treated with two nephrotoxins, hiPSC and differentiating hiPSC were more sensitive to cisplatin than differentiated PTELC, whereas all stages were equally sensitive to cyclosporin A. Both toxins also had an inhibitory effect on albumin uptake. Our results suggest a high sensitivity of differentiating cells towards toxins, which could have an unfavorable effect on regenerative processes. To study this, our model of hiPSC differentiating into PTELC appears suitable.

Methyl-CpG-binding domain 3 (Mbd3) is an important regulator for apoptosis in mouse embryonic stem cells

Methyl-CpG-binding domain 3 (Mbd3) is a core repressor complex component. Although Mbd3 is required for the pluripotency of embryonic stem cells (ES), the role of Mbd3 in mouse ES (mES) cell apoptosis remains undefined. In this study naïve-state mES were derived and maintained in the presence of a selective protein kinase C pathway inhibitor (PKCi; Gӧ6983) to study the function of Mbd3 during mES apoptosis. Mbd3 overexpression in mES decreased the total cell number and viability, and it also dramatically increased the rate of apoptosis. Further investigation of Mbd3 overexpression revealed a 3-fold increase in the proapoptotic/prosurvival protein ratio (Bax/Bcl-2) and elevated RNA expression levels of apoptosis-related genes, including Bim, Trail, Fasl, and caspase 3, with reduced Bcl-2 RNA expression levels. Removal of PKCi from the mES cell culture resulted in upregulated Mbd3 expression and apoptosis, similar to the effects of Mbd3 overexpression. Furthermore, specific knockdown of endogenous Mbd3 partially rescued the mES apoptosis induced by the removal of PKCi, thus increasing the total cell number and viability while decreasing the rate of apoptosis. Additionally, Bax, Bim, Trail, and caspase 3 RNA expression levels were partially reduced, and that of Bcl-2 was partially increased. Our findings support Mbd3 as a pivotal regulator of apoptosis in mES.