The Effects of Indoxyl Sulfate on Human Umbilical Cord-Derived Mesenchymal Stem Cells In Vitro

Indoxyl sulfate, an important protein-bound uremic toxin, can damage stem cells, thus hampering stem cell-based regenerative medicine approaches targeting chronic kidney diseases (CKD). Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) are thought to have promising clinical application because of their high proliferative potential and ease of isolation than MSCs from other sources. In the present study, we aimed to determine the harmful effects of indoxyl sulfate on the phenotype and functional potential of hUC-MSCs in vitro.

The toxicity and cell viability was examined by Trypan blue exclusion and MTT assay. The cellular surface markers and the percentage of apoptotic cells by Annexin-V/PI staining were analyzed by flow cytometry. Proliferation was evaluated based on cell number counting and Ki-67 immunostaining. Cell senescence was measured using senescence-associated β-Galactosidase activity. The ability to stimulate the development of CD4+CD25+FoxP3+ regulatory T cells was assessed by incubating hUC-MSCs with peripheral blood mononuclear cells from the healthy volunteers.

Our results demonstrated that the immunophenotype of hUC-MSCs was not affected by indoxyl sulfate flow cytometry. However, a significant decrease in cell numbers and fraction of Ki-67 positive proliferating cells, along with a significant increase in cellular senescence were detected in hUC-MSCs after exposure to indoxyl sulfate. Additionally, their ability to stimulate CD4+CD25+FoxP3+ regulatory T cell production was compromised when hUC-MSCs were pretreated with indoxyl sulfate.

Taken together, our study clearly demonstrated that the molecular alterations and functional incompetence in hUC-MSCs under the challenge of indoxyl sulfate in vitro.