hUC-MSCs: evaluation of acute and long-term routine toxicity testing in mice and rats.

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) are present in human umbilical connective tissue and can differentiate into various cell types. Our previous studies have proved that hUC-MSCs do not lead to allergies and tumorigenesis. In the present study, the acute and long-term toxicity of hUC-MSCs in mice and rats was evaluated. The acute toxicity of hUC-MSCs was assessed in 8-week-old mice receiving two caudal intravenous (i.v.) injections of hUC-MSCs at the maximum tolerated dose of 1.5 × 107 cells/kg with an interval of 8 h and the observation period sustained for 14 days. For the long-term toxicity evaluation, rats were randomly divided into control, low-dose (3.0 × 105 cells/kg), mid-dose (1.5 × 106 cells/kg), and high-dose (7.5 × 106 cells/kg) groups, which were treated with hUC-MSCs via a caudal i.v. injection every 3 days for 90 days. Weight and food intake evaluation was performed for all rats for 2 weeks after the hUC-MSC administration. The animals were then sacrificed for hematological, blood biochemical, and pathological analyses, as well as organ index determination. We observed no obvious acute toxicity of hUC-MSCs in mice at the maximum tolerated dose. Long-term toxicity tests in rats showed no significant differences between HUC-MSC-treated and control groups in the following parameters: body weight, hematological and blood biochemical parameters, and histopathologic changes in the heart, liver, kidneys, and lungs. This study provides evidence of the safety of i.v. hUC-MSCs infusion for future clinical therapies.