The differentiation of hMSCs counteracts their migration capability and pro-angiogenic effects in vitro.

Human mesenchymal stem cells (hMSCs) have been applied therapeutically in numerous clinical trials. The pro-angiogenic effects of hMSCs, as well as their strong tumor tropism, have been shown both in vitro and in vivo. Some studies suggest using hMSCs as potential drug-carriers for tumor therapy. In previous investigations by our group, the pro-tumorigenic effects of hMSCs on head and neck squamous cell carcinoma (HNSCC) were shown. However, the influence of hMSCs on tumor vascularization as well as the possibility of its inhibition are yet to be elucidated. The cytokine patterns of the HNSCC cell line FaDu, native hMSCs (hMSCs-nat), hMSCs differentiated into adipocytes (hMSCs-adip) and osteocytes (hMSCs-ost) were evaluated. Human umbilical vein endothelial cells (HUVECs) were co-cultured with FaDu cells, hMSCs-nat, hMSCs-adip and hMSCs-ost. The capillary tube formation assay was applied. Furthermore, the migration capability of hMSCs-nat, hMSCs-adip and hMSCs-ost towards FaDu cells was measured in a Transwell system. Spheroids were cultured from hMSCs-nat, FaDu cells and DiI-labeled HUVECs. FaDu cells, hMSCs-nat, hMSCs-adip and hMSCs-ost released a wide range of cytokines and growth factors, e.g., IL-6, IL-8, IL-10, GRO and MCP. In the capillary tube formation assay, HUVECs generated significantly longer tubes after co-cultivation with hMSCs-nat as compared to HUVECs alone and FaDu. Differentiation into adipocytes and osteocytes counteracted the tube formation. The adipogenic differentiation did not alter hMSC motility, whereas osteogenic differentiation significantly inhibited hMSC migration. Generation of multi-cellular spheroids from hMSCs-nat, FaDu cells and DiI-labeled HUVECs was possible. Florescence microscopy revealed that all HUVECs were present in the spheroid core. Taken together, hMSCs-nat have a pro-angiogenic effect. The effects are counteracted by the differentiation of hMSCs towards osteogenic and adipogenic lineages. The differentiation of stem cells into different lineages may be a promising solution to generating carriers for cancer therapy without pro-tumorigenic properties.