Hydrogen Sulfide Delivery to Enhance Bone Tissue Engineering Cell Survival.

Though crucial for natural bone healing, local calcium ion (Ca) and phosphate ion (P) concentrations can exceed the cytotoxic limit leading to mitochondrial overload, oxidative stress, and cell death. For bone tissue engineering applications, HS can be employed as a cytoprotective molecule to enhance mesenchymal stem cell (MSC) tolerance to cytotoxic Ca/P concentrations. Varied concentrations of sodium hydrogen sulfide (NaSH), a fast-releasing HS donor, were applied to assess the influence of HS on MSC proliferation. The results suggested a toxicity limit of 4 mM for NaSH and that 1 mM of NaSH could improve cell proliferation and differentiation in the presence of cytotoxic levels of Ca (32 mM) and/or P (16 mM). To controllably deliver HS over time, a novel donor molecule (thioglutamic acid-GluSH) was synthesized and evaluated for its HS release profile. Excitingly, GluSH successfully maintained cytoprotective level of HS over 7 days. Furthermore, MSCs exposed to cytotoxic Ca/P concentrations in the presence of GluSH were able to thrive and differentiate into osteoblasts. These findings suggest that the incorporation of a sustained HS donor such as GluSH into CaP-based bone graft substitutes can facilitate considerable cytoprotection, making it an attractive option for complex bone regenerative engineering applications.