# Toxicological Effects of Titanium Dioxide Nanoparticles on Human Menstrual Blood Mesenchymal Stem Cells

## TL;DR

This study shows that high concentrations of titanium dioxide nanoparticles can harm human menstrual blood stem cells, affecting their survival, function, and ability to regenerate.

## Contribution

The novel contribution is the first evaluation of titanium dioxide nanoparticle effects on human menstrual blood mesenchymal stem cells.

## Key findings

- TiO2 NPs reduced hMB-MSC viability and proliferation in a concentration- and time-dependent manner.
- NP exposure decreased membrane expression of CD73 and CD90, indicating altered cell surface markers.
- TiO2 NPs reduced reactive oxygen species generation, suggesting altered cellular stress responses.

## Abstract

Human exposure to titanium dioxide nanoparticles (TiO2 NPs) is common. These NPs are used in cosmetics, paint, food, and other products. Their nanometric size (<100 nm) allows entry into the bloodstream, from which they can reach organs and cells throughout the body. Although TiO2 NPs have been reported to damage certain cell lines and organs and to alter cellular function, their impact on human menstrual blood mesenchymal stem cells (hMB-MSCs) is unknown. This study evaluated the effects of TiO2 NPs on viability, proliferation, morphology, membrane-marker expression, and reactive oxygen species (ROS) production in primary cultures of hMB-MSCs derived from menstrual blood. Cells were exposed to different concentrations of TiO2 NPs for 3, 7, and 14 days. TiO2 NPs decreased hMB-MSC viability and proliferation in a concentration- and time-dependent manner. Cellular viability was reduced by up to 6%, 11%, and 18% at 3, 7, and 14 days, respectively (statistically significant vs. control). Cellular proliferation decreased by 3%, 5%, and 33% at 15.63, 62.5, and 250 μg/mL TiO2, respectively. TiO2 NPs were internalized and observed in the cytoplasm, forming perinuclear aggregates. NP-exposed cells showed reduced membrane expression of CD73 (7.9% decrease) and CD90 (25.72% decrease) compared with control cells. Finally, TiO2 NPs at 15.63, 62.5, and 250 µg/mL reduced ROS generation by 56.79%, 62.79%, and 53.35%, respectively, after 4 h (statistically significant vs. control). In summary, exposure to high concentrations of TiO2 NPs leads to intracellular nanoparticle deposits and alters key functions of human menstrual blood mesenchymal stem cells, including immunomodulation, immune protection, molecular behavior, cell differentiation, and regenerative capacity.