Investigation of peripheral rat blood immune phenotype to evaluate the biocompatibility of graphene nanoparticles and xenografted mesenchymal stem cells

Aim: Peripheral nerve injuries (PNIs) often result in a diminished quality of life for those affected and are the most common nervous system injury, with limited treatment options. Regenerative medicine presents novel biomaterial and cell-based therapies to repair the damaged tissue. Graphene oxide (GO), and mesenchymal stem cells (MSCs) have the potential to serve as components to treat PNI. This study evaluates the systemic toxicity of GO and xenogenic human MSCs by analyzing the peripheral blood immune phenotype when a novel nerve guidance conduit (NGC) is implanted in a rat model for six months. Methods: A 10-mm long sciatic nerve defect model was created in 8–10-week-old Lewis rats. Four treatment groups were generated: autograft (positive control), poly (lactic-co-glycolic acid) (PLGA) NGC, PLGA NGC with 0.25% GO, and PLGA/GO NGC seeded with 1 × 106 human adipose-derived MSCs. Tail blood was collected before surgery, and at 24 hours, 2 weeks, 2, 3, 5, and 6 months after surgery. Hematological analyses were carried out to evaluate systemic changes, if any, in peripheral immune cell types, namely, T lymphocytes, B lymphocytes, natural killer cells, and macrophages. The treated and contralateral sciatic nerves were excised, paraffin embedded, sectioned, and H&E stained, to identify any local foreign body rejection. Results: Treatment groups with GO and MSCs displayed percent total values of peripheral immune cells equivalent to the autograft at each time point. There was no evidence of an inflammatory response in the histological samples. Conclusions: The lack of changes in immune phenotype demonstrates a lack of nanotoxicity of the graphene nanoparticles and no evidence of adverse effects due to the MSCs. This was further supported by a lack of local foreign body response at the site of implantation. Overall, the PLGA/GO NGC + MSCs construct is biocompatible for six months in a rat PNI model, exhibiting a potential for clinical translation.